ERK5 Inhibition Induces Autophagy-Mediated Cancer Cell Death by Activating ER Stress

ERK5 kinase; Antitumor drug; ApoptosisKinasa ERK5; Medicament antitumoral; ApoptosiQuinasa ERK5; Medicamento antitumoral; ApoptosisAutophagy is a highly conserved intracellular process that preserves cellular homeostasis by mediating the lysosomal degradation of virtually any component of the cytoplasm. Autophagy is a key instrument of cellular response to several stresses, including endoplasmic reticulum (ER) stress. Cancer cells have developed high dependency on autophagy to overcome the hostile tumor microenvironment. Thus, pharmacological activation or inhibition of autophagy is emerging as a novel antitumor strategy. ERK5 is a novel member of the MAP kinase family that is activated in response to growth factors and different forms of stress. Recent work has pointed ERK5 as a major player controlling cancer cell proliferation and survival. Therefore small-molecule inhibitors of ERK5 have shown promising therapeutic potential in different cancer models. Here, we report for the first time ERK5 as a negative regulator of autophagy. Thus, ERK5 inhibition or silencing induced autophagy in a panel of human cancer cell lines with different mutation patterns. As reported previously, ERK5 inhibitors (ERK5i) induced apoptotic cancer cell death. Importantly, we found that autophagy mediates the cytotoxic effect of ERK5i, since ATG5ˉ/ˉ autophagy-deficient cells viability was not affected by these compounds. Mechanistically, ERK5i stimulated autophagic flux independently of the canonical regulators AMPK or mTORC1. Moreover, ERK5 inhibition resulted in ER stress and activation of the Unfolded Protein Response (UPR) pathways. Specifically, ERK5i induced expression of the ER luminal chaperone BiP (a hallmark of ER stress), the UPR markers CHOP and ATF4, and the spliced form of XBP1. Pharmacological inhibition of UPR with chemical chaperone TUDC, or ATF4 silencing, resulted in impaired ERK5i-mediated UPR, autophagy and cytotoxicity. Overall, our results suggest that ERK5 inhibition induces autophagy-mediated cancer cell death by activating ER stress. Since ERK5 inhibition sensitizes cancer cells and tumors to chemotherapy, future work will determine the relevance of UPR and autophagy in the combined use of chemotherapy and ERK5i to tackle Cancer.This work was supported by the Spanish Ministry of Economy and Competitiveness (MINECO, grant SAF2015-64237-R), the Spanish Ministry of Science and Innovation (Grant PID2019-107561RB-I00), and cofounded by the European Regional Development Fund (ERDF)

The New Antitumor Drug ABTL0812 Inhibits the Akt/mTORC1 Axis by Upregulating Tribbles-3 Pseudokinase

Purpose: ABTL0812 is a novel first-in-class, small molecule which showed antiproliferative effect on tumor cells in phenotypic assays. Here we describe the mechanism of action of this antitumor drug, which is currently in clinical development. Experimental design: We investigated the effect of ABTL0812 on cancer cell death, proliferation, and modulation of intracellular signaling pathways, using human lung (A549) and pancreatic (MiaPaCa-2) cancer cells and tumor xenografts. To identify cellular targets, we performed in silico high-throughput screening comparing ABTL0812 chemical structure against ChEMBL15 database. Results: ABTL0812 inhibited Akt/mTORC1 axis, resulting in impaired cancer cell proliferation and autophagy-mediated cell death. In silico screening led us to identify PPARs, PPARα and PPARγ as the cellular targets of ABTL0812. We showed that ABTL0812 activates both PPAR receptors, resulting in upregulation of Tribbles-3 pseudokinase (TRIB3) gene expression. Upregulated TRIB3 binds cellular Akt, preventing its activation by upstream kinases, resulting in Akt inhibition and suppression of the Akt/mTORC1 axis. Pharmacologic inhibition of PPARα/γ or TRIB3 silencing prevented ABTL0812-induced cell death. ABTL0812 treatment induced Akt inhibition in cancer cells, tumor xenografts, and peripheral blood mononuclear cells from patients enrolled in phase I/Ib first-in-human clinical trial. Conclusions: ABTL0812 has a unique and novel mechanism of action, that defines a new and drugable cellular route that links PPARs to Akt/mTORC1 axis, where TRIB3 pseudokinase plays a central role. Activation of this route (PPARα/γ-TRIB3-Akt-mTORC1) leads to autophagy-mediated cancer cell death. Given the low toxicity and high tolerability of ABTL0812, our results support further development of ABTL0812 as a promising anticancer therapy

Structural and Atropisomeric Factors Governing the Selectivity of Pyrimido-benzodiazipinones as Inhibitors of Kinases and Bromodomains

This is the author accepted manuscript. The final version is available from American Chemical Society via the DOI in this recordBromodomains have been pursued intensively over the past several years as emerging targets for the devel-opment of anti-cancer and anti-inflammatory agents. It has recently been shown that some kinase inhibitors are able to potently inhibit the bromodomains of BRD4. The clinical activities of PLK inhibitor BI-2536 and JAK2-FLT3 inhibitor TG101348 have been attributed to this unexpected poly-pharmacology, indicating that dual-kinase/bromodomain activity may be advantageous in a therapeutic context. However, for target validation and biological investigation, a more selec-tive target profile is desired. Here we report that benzo[e]pyrimido-[5,4-b]diazepine-6(11H)-ones, versatile ATP-site di-rected kinase pharmacophores utilized in the development of inhibitors of multiple kinases including a number of previ-ously reported kinase chemical probes, are also capable of exhibiting potent BRD4-dependent pharmacology. Using a dual kinase-bromodomain inhibitor of the kinase domains of ERK5 and LRRK2, and the bromodomain of BRD4 as a case study, we define the structure-activity relationships required to achieve dual kinase/BRD4 activity as well as how to di-rect selectivity towards inhibition of either ERK5 or BRD4. This effort resulted in identification of one of the first report-ed kinase-selective chemical probes for ERK5 (JWG-071), a BET selective inhibitor with 1 μM BRD4 IC50 (JWG-115), and additional inhibitors with rationally designed polypharmacology (JWG-047, JWG-069). Co-crystallography of seven representative inhibitors with the first bromodomain of BRD4 demonstrate that distinct atropisomeric conformers rec-ognize the kinase ATP-site and the BRD4 acetyl lysine binding site, conformational preferences supported by rigid dock-ing studies.This work was supported by NIH (Grant No. U54HL127365, to N.S.G. and J.W.; No. NIH P50 GM107618, to X.X. and S.C.B.; Nos. NIH U54 HD093540 and P01 CA066996, to J.Q.), the Medical Research Council (No. MC_UU_12016/2, to D.R.A.), the Spanish Ministerio de Economia y Competitividad (MINECO) (Grant No. SAF2015-60268R, to J.M.L.), and Fondo Europeo de Desarrollo Regional (FEDER) funds (to J.M.L.). D.L.B. was supported as a Merck Fellow of Damon Runyon Cancer Research Foundation (No. DRG-2196-14)

Evaluation of appendicitis risk prediction models in adults with suspected appendicitis

Background Appendicitis is the most common general surgical emergency worldwide, but its diagnosis remains challenging. The aim of this study was to determine whether existing risk prediction models can reliably identify patients presenting to hospital in the UK with acute right iliac fossa (RIF) pain who are at low risk of appendicitis. Methods A systematic search was completed to identify all existing appendicitis risk prediction models. Models were validated using UK data from an international prospective cohort study that captured consecutive patients aged 16–45 years presenting to hospital with acute RIF in March to June 2017. The main outcome was best achievable model specificity (proportion of patients who did not have appendicitis correctly classified as low risk) whilst maintaining a failure rate below 5 per cent (proportion of patients identified as low risk who actually had appendicitis). Results Some 5345 patients across 154 UK hospitals were identified, of which two‐thirds (3613 of 5345, 67·6 per cent) were women. Women were more than twice as likely to undergo surgery with removal of a histologically normal appendix (272 of 964, 28·2 per cent) than men (120 of 993, 12·1 per cent) (relative risk 2·33, 95 per cent c.i. 1·92 to 2·84; P < 0·001). Of 15 validated risk prediction models, the Adult Appendicitis Score performed best (cut‐off score 8 or less, specificity 63·1 per cent, failure rate 3·7 per cent). The Appendicitis Inflammatory Response Score performed best for men (cut‐off score 2 or less, specificity 24·7 per cent, failure rate 2·4 per cent). Conclusion Women in the UK had a disproportionate risk of admission without surgical intervention and had high rates of normal appendicectomy. Risk prediction models to support shared decision‐making by identifying adults in the UK at low risk of appendicitis were identified

Mecanisme d'acció del nou fàrmac antitumoral ART10812: rol de la pseudoquinasa TRIB3, l'estrès reticular i els esfingolípids en la mort mediada per autofàgia

L’ABTL0812 és un derivat lipídic amb activitat antitumoral llicenciat per la companyia biofarmacèutica Ability Pharmaceuticals. En estudis preliminars es va observar que l’ABTL0812 indueix citotoxicitat en un ampli espectre de cèl·lules tumorals humanes i una inhibició del creixement de tumors xenografts derivats de cèl·lules tumorals humanes, propietats que han motivat el seu desenvolupament pre-clínic. A l’actualitat, l’ABTL0812 es troba en Fase Clínica 2 en pacients amb càncer de pulmó escamós i d’endometri avançat (identificador ClinicalTrials.gov: NCT03366480). El nostre laboratori està implicat en caracteritzar el seu mecanisme d’acció antitumoral, utilitzant com a model les cèl·lules MiaPaca2 (adenocarcinoma pancreàtic) i A549 (adenocarcinoma de pulmó). Estudis previs realitzats al laboratori mostren que l’ABTL0812 activa els receptors PPAR i PPAR, que medien en la inducció de mort dependent d’autofàgia sense induir l’aparició de trets típicament apoptòtics. En aquesta Tesi Doctoral, mitjançant assajos de gen reporter luciferasa, quantificació de mRNA per RT-qPCR i assaig d’immunoblot, demostrem que l’activació dels receptors PPAR/ indueix l’activació transcripcional de la pseudoquinasa TRIB3. Una vegada sobre-expressada, TRIB3 uneix Akt i impedeix la seva activació per les quinases activadores PDK1 i mTORC2. Com a conseqüència d’això, s’inhibeix el complex mTORC1. Tanmateix, s’ha constatat que la inhibició del complex mTORC1 a les cèl·lules tumorals humanes MiaPaca2 i A549 no és suficient per induir una autofàgia robusta anàloga a l’observada per l’ABTL0812. Aquest fet va motivar l’estudi sobre si l’estrès reticular podia estar relacionat amb la sobre-expressió de TRIB3 i la mort cel·lular mediada per autofàgia induïdes per l’ABTL0812, tal com s’ha proposat per altres composts anti-tumorals com el tetrahidrocannabinol. En aquest treball hem observat que l’ABTL0812 indueix dilatació del reticle endoplasmàtic i la sobre-expressió dels marcadors d’estrès reticular BiP, ATF4 i CHOP. En conjunt, aquests resultats demostren la inducció d’estrès reticular per part de l’ABTL0812. El bloqueig farmacològic de l’estrès reticular mostra preliminarment que l’estrès reticular media en la citotoxicitat induïda per l’ABTL0812. D‘interès, s’ha posat a punt la quantificació dels nivells de mRNA plasmàtics dels marcador d’estrès reticular CHOP i TRIB3, tant en mostres de sang total com a PBMCs purificades, i s’ha constatat que augmenten en els pacients humans en resposta al tractament amb ABTL0812. En l’actualitat, aquests biomarcadors farmacodinàmics s’estan utilitzant a la Fase Clínica 2. L’anàlisi per espectrometria de masses de l’esfingolipidoma de cèl·lules tumorals ha permès observar que l’ABTL0812 indueix l’acumulació de dihidroceramides de cadena llarga, sense alterar els nivells de ceramides. Aquest esdeveniment s’explica pel fet que la incubació amb ABTL0812 resulta en la inhibició de l’enzim desaturasa-1 (Des-1) a la cèl·lula tumoral. Des-1 és l’últim enzim de la via de síntesi de novo de ceramides (catalitza el pas de dihidroceramides a ceramides) i la seva inhibició resulta en l’acumulació de dihidroceramides de cadena llarga, de manera anàloga a la mostrada per l’inhibidor específic de Des-1 GT11. D’interès, el tractament de les cèl·lules tumorals amb la dihidroceramida de cadena curta dideuterada d2c8DhCer (que provoca un augment dels nivells cel·lulars de dihidroceramides) resulta en la inducció d’estrès reticular, autofàgia i citotoxicitat a les cèl·lules tumorals MiaPaca2 i A549, tal com fa l’ABTL0812. L’estudi preliminar dels processos executors de la mort cel·lular induïda per l’ABTL0812 mostra que aquest compost altera la funció mitocondrial (depleció dràstica d’ATP cel·lular) i activa la via canònica de mitofàgia PINK1/parkina/ubiquitina. A més a més, l’ABTL0812 promou l’alliberació citosòlica de catepsines lisosomals, suggerint la inducció de permeabilització de membrana lisosomal (LMP) que explicaria la mort per necrosi observada a les cèl·lules tumorals. Finalment, aquesta Tesi proposa que l’ABTL0812 actuaria de forma paral·lela a través de dos eixos. Per un costat, activaria els receptors PPAR/, que indueixen la sobre-expressió de TRIB3 i la subseqüent inhibició d’Akt i del complex mTORC1. Per l’altre costat, l’ABTL0812 inhibiria l’enzim Des-1, provocant una acumulació de dihidroceramides de cadena llarga i l’activació d’estrès reticular. Ambdós eixos del mecanisme sinergitzen en l’activació d’autofàgia robusta i mort cel·lular, com demostra el tractament combinat amb l’inhibidor específic de mTORC1 Everolimus i l’inhibidor específic de Des-1 GT11.ABTL0812 is a polyunsaturated fatty acid derivative with antitumoral activity licensed by the biopharmaceutical company Ability Pharmaceuticals. ABTL0812 shows cytotoxicity in a wide panel of human tumor cell lines and induces tumor growth inhibition in human tumor cell-derived xenografts. This have encouraged its pre-clinical and clinical development. ABTL0812 recently started Phase 2 Clinical trials in patients with advanced endometrial cancer and squamous NSCLC, as a first line of treatment in combination with paclitaxel and carboplatin (ClinicalTrials.gov: NCT03366480). Our laboratory is involved in the characterization of ABTL0812’s antitumoral mechanism of action, using MiPaca2 (pancreatic adenocarcinoma) and A549 (lung adenocarcinoma) cell lines as models. Previous studies carried out in our laboratory uncovered that in cells ABTL0812 activates peroxisome proliferator-activated receptors PPAR/ receptors, inducing autophagy-mediated cancer cell death without activating apoptosis. Here, by using gene reporter luciferase assay, qRT-PCR mRNA quantification and immunoblot analysis, we show that ABTL0812 activates PPAR-mediated transcription of Tribbles 3 (TRIB3) pseudokinase. Over-expressed TRIB3 then binds and inhibits Akt, preventing its activation by PDK1 and mTORC2 upstream kinases, resulting in inhibition of the oncogenic Akt/mTORC1 axis. However, we found that mTORC1 inhibition is not enough to induce robust autophagy in MiaPaca2 and A549 cell lines, as it does ABTL0812. Thus, we investigated whether endoplasmic reticulum (ER) stress could also account for ABTL0812-induced TRIB3 overexpression, as it has been proposed for other antitumoral drugs such as tetrahydrocannabinol. We found ABTL0812 induces endoplasmic reticulum dilatation and over-expression of the endoplasmic reticulum stress markers BiP, ATF4 and CHOP (both mRNA and protein levels), indicating that ABTL0812 induces ER stress in these tumor cells. We also show preliminary pharmacological data suggesting that ER stress has a role in mediating ABTL0812-induced cytotoxicity. Remarkably, we have optimized a protocol for the quantification of TRIB3 and CHOP mRNAs (qRT-PCR) in blood and purified PBMCs from patients enrolled in Clinical Phase 2. We describe increased levels of CHOP and TRIB3 mRNAs in response to ABTL0812 treatment. Furthermore, we have proposed and optimized RT quantification of the ER stress genes TRIB3 and CHOP as reliable pharmacodynamic biomarkers for the ongoing Phase 2 Clinical trials. Given the role of sphingolipids in initiating the ER stress, we undertook a comprehensive mass-spec analysis of cellular sphingolipids to show that ABTL0812 induces long-chain dihydroceramides accumulation without affecting ceramide levels. In cells, dihydroceramides are converted into ceramides by the desaturase-1 (Des-1) enzyme. Enzymatic analysis demonstrated that ABTL0812 treatment results in inhibition of Des-1 activity in vitro and in cellular assays, provoking an accumulation of long-chain dihydroceramides, analogously to that induced by Des-1 specific inhibitor GT11. Interestingly, we show that treatment with the dideuterated short-chain dihydroceramide d2c8DhCer (which induces an increase of cellular dihydroceramides) results in endoplasmic reticulum stress, autophagy and cytotoxicity in MiaPaca2 and A549 cell lines. Preliminary characterization of ABTL0812-induced cell death shows that this compound alters mitochondrial function (induces a drastic depletion of cellular ATP) and it activates the canonic mitophagy pathway PINK1/parkin/ubiquitin. Furthermore, ABTL0812 induces cytosolic release lysosomal cathepsin B, suggesting a lysosomal membrane permeabilization (LMP) that would explain the necrotic cell death observed in tumor cells. Finally, this work proposes that ABTL0812 exerts its antitumoral activity acting simultaneously on two axes. On one hand, ABTL0812 activates PPAR/ receptors, which induce TRIB3 over-expression and the subsequent Akt and mTORC1 inhibition. On the other hand, ABTL0812 inhibits Des-1 enzyme, resulting in accumulation of long-chain dihydroceramides and the subsequent activation of ER stress. Both axes synergize to activate a robust autophagy which ultimately leads to lysosomal membrane permeabilization and necrosis. In agreement with this, we show that the inhibition of mTORC1 (Everolimus) synergizes with Des-1 inhibition (GT11) to promote autophagy and cytotoxicity

Mecanisme d'acció del nou fàrmac antitumoral ART10812: rol de la pseudoquinasa TRIB3, l'estrès reticular i els esfingolípids en la mort mediada per autofàgia

L’ABTL0812 és un derivat lipídic amb activitat antitumoral llicenciat per la companyia biofarmacèutica Ability Pharmaceuticals. En estudis preliminars es va observar que l’ABTL0812 indueix citotoxicitat en un ampli espectre de cèl·lules tumorals humanes i una inhibició del creixement de tumors xenografts derivats de cèl·lules tumorals humanes, propietats que han motivat el seu desenvolupament pre-clínic. A l’actualitat, l’ABTL0812 es troba en Fase Clínica 2 en pacients amb càncer de pulmó escamós i d’endometri avançat (identificador ClinicalTrials.gov: NCT03366480). El nostre laboratori està implicat en caracteritzar el seu mecanisme d’acció antitumoral, utilitzant com a model les cèl·lules MiaPaca2 (adenocarcinoma pancreàtic) i A549 (adenocarcinoma de pulmó). Estudis previs realitzats al laboratori mostren que l’ABTL0812 activa els receptors PPAR i PPAR, que medien en la inducció de mort dependent d’autofàgia sense induir l’aparició de trets típicament apoptòtics. En aquesta Tesi Doctoral, mitjançant assajos de gen reporter luciferasa, quantificació de mRNA per RT-qPCR i assaig d’immunoblot, demostrem que l’activació dels receptors PPAR/ indueix l’activació transcripcional de la pseudoquinasa TRIB3. Una vegada sobre-expressada, TRIB3 uneix Akt i impedeix la seva activació per les quinases activadores PDK1 i mTORC2. Com a conseqüència d’això, s’inhibeix el complex mTORC1. Tanmateix, s’ha constatat que la inhibició del complex mTORC1 a les cèl·lules tumorals humanes MiaPaca2 i A549 no és suficient per induir una autofàgia robusta anàloga a l’observada per l’ABTL0812. Aquest fet va motivar l’estudi sobre si l’estrès reticular podia estar relacionat amb la sobre-expressió de TRIB3 i la mort cel·lular mediada per autofàgia induïdes per l’ABTL0812, tal com s’ha proposat per altres composts anti-tumorals com el tetrahidrocannabinol. En aquest treball hem observat que l’ABTL0812 indueix dilatació del reticle endoplasmàtic i la sobre-expressió dels marcadors d’estrès reticular BiP, ATF4 i CHOP. En conjunt, aquests resultats demostren la inducció d’estrès reticular per part de l’ABTL0812. El bloqueig farmacològic de l’estrès reticular mostra preliminarment que l’estrès reticular media en la citotoxicitat induïda per l’ABTL0812. D‘interès, s’ha posat a punt la quantificació dels nivells de mRNA plasmàtics dels marcador d’estrès reticular CHOP i TRIB3, tant en mostres de sang total com a PBMCs purificades, i s’ha constatat que augmenten en els pacients humans en resposta al tractament amb ABTL0812. En l’actualitat, aquests biomarcadors farmacodinàmics s’estan utilitzant a la Fase Clínica 2. L’anàlisi per espectrometria de masses de l’esfingolipidoma de cèl·lules tumorals ha permès observar que l’ABTL0812 indueix l’acumulació de dihidroceramides de cadena llarga, sense alterar els nivells de ceramides. Aquest esdeveniment s’explica pel fet que la incubació amb ABTL0812 resulta en la inhibició de l’enzim desaturasa-1 (Des-1) a la cèl·lula tumoral. Des-1 és l’últim enzim de la via de síntesi de novo de ceramides (catalitza el pas de dihidroceramides a ceramides) i la seva inhibició resulta en l’acumulació de dihidroceramides de cadena llarga, de manera anàloga a la mostrada per l’inhibidor específic de Des-1 GT11. D’interès, el tractament de les cèl·lules tumorals amb la dihidroceramida de cadena curta dideuterada d2c8DhCer (que provoca un augment dels nivells cel·lulars de dihidroceramides) resulta en la inducció d’estrès reticular, autofàgia i citotoxicitat a les cèl·lules tumorals MiaPaca2 i A549, tal com fa l’ABTL0812. L’estudi preliminar dels processos executors de la mort cel·lular induïda per l’ABTL0812 mostra que aquest compost altera la funció mitocondrial (depleció dràstica d’ATP cel·lular) i activa la via canònica de mitofàgia PINK1/parkina/ubiquitina. A més a més, l’ABTL0812 promou l’alliberació citosòlica de catepsines lisosomals, suggerint la inducció de permeabilització de membrana lisosomal (LMP) que explicaria la mort per necrosi observada a les cèl·lules tumorals. Finalment, aquesta Tesi proposa que l’ABTL0812 actuaria de forma paral·lela a través de dos eixos. Per un costat, activaria els receptors PPAR/, que indueixen la sobre-expressió de TRIB3 i la subseqüent inhibició d’Akt i del complex mTORC1. Per l’altre costat, l’ABTL0812 inhibiria l’enzim Des-1, provocant una acumulació de dihidroceramides de cadena llarga i l’activació d’estrès reticular. Ambdós eixos del mecanisme sinergitzen en l’activació d’autofàgia robusta i mort cel·lular, com demostra el tractament combinat amb l’inhibidor específic de mTORC1 Everolimus i l’inhibidor específic de Des-1 GT11.ABTL0812 is a polyunsaturated fatty acid derivative with antitumoral activity licensed by the biopharmaceutical company Ability Pharmaceuticals. ABTL0812 shows cytotoxicity in a wide panel of human tumor cell lines and induces tumor growth inhibition in human tumor cell-derived xenografts. This have encouraged its pre-clinical and clinical development. ABTL0812 recently started Phase 2 Clinical trials in patients with advanced endometrial cancer and squamous NSCLC, as a first line of treatment in combination with paclitaxel and carboplatin (ClinicalTrials.gov: NCT03366480). Our laboratory is involved in the characterization of ABTL0812’s antitumoral mechanism of action, using MiPaca2 (pancreatic adenocarcinoma) and A549 (lung adenocarcinoma) cell lines as models. Previous studies carried out in our laboratory uncovered that in cells ABTL0812 activates peroxisome proliferator-activated receptors PPAR/ receptors, inducing autophagy-mediated cancer cell death without activating apoptosis. Here, by using gene reporter luciferase assay, qRT-PCR mRNA quantification and immunoblot analysis, we show that ABTL0812 activates PPAR-mediated transcription of Tribbles 3 (TRIB3) pseudokinase. Over-expressed TRIB3 then binds and inhibits Akt, preventing its activation by PDK1 and mTORC2 upstream kinases, resulting in inhibition of the oncogenic Akt/mTORC1 axis. However, we found that mTORC1 inhibition is not enough to induce robust autophagy in MiaPaca2 and A549 cell lines, as it does ABTL0812. Thus, we investigated whether endoplasmic reticulum (ER) stress could also account for ABTL0812-induced TRIB3 overexpression, as it has been proposed for other antitumoral drugs such as tetrahydrocannabinol. We found ABTL0812 induces endoplasmic reticulum dilatation and over-expression of the endoplasmic reticulum stress markers BiP, ATF4 and CHOP (both mRNA and protein levels), indicating that ABTL0812 induces ER stress in these tumor cells. We also show preliminary pharmacological data suggesting that ER stress has a role in mediating ABTL0812-induced cytotoxicity. Remarkably, we have optimized a protocol for the quantification of TRIB3 and CHOP mRNAs (qRT-PCR) in blood and purified PBMCs from patients enrolled in Clinical Phase 2. We describe increased levels of CHOP and TRIB3 mRNAs in response to ABTL0812 treatment. Furthermore, we have proposed and optimized RT quantification of the ER stress genes TRIB3 and CHOP as reliable pharmacodynamic biomarkers for the ongoing Phase 2 Clinical trials. Given the role of sphingolipids in initiating the ER stress, we undertook a comprehensive mass-spec analysis of cellular sphingolipids to show that ABTL0812 induces long-chain dihydroceramides accumulation without affecting ceramide levels. In cells, dihydroceramides are converted into ceramides by the desaturase-1 (Des-1) enzyme. Enzymatic analysis demonstrated that ABTL0812 treatment results in inhibition of Des-1 activity in vitro and in cellular assays, provoking an accumulation of long-chain dihydroceramides, analogously to that induced by Des-1 specific inhibitor GT11. Interestingly, we show that treatment with the dideuterated short-chain dihydroceramide d2c8DhCer (which induces an increase of cellular dihydroceramides) results in endoplasmic reticulum stress, autophagy and cytotoxicity in MiaPaca2 and A549 cell lines. Preliminary characterization of ABTL0812-induced cell death shows that this compound alters mitochondrial function (induces a drastic depletion of cellular ATP) and it activates the canonic mitophagy pathway PINK1/parkin/ubiquitin. Furthermore, ABTL0812 induces cytosolic release lysosomal cathepsin B, suggesting a lysosomal membrane permeabilization (LMP) that would explain the necrotic cell death observed in tumor cells. Finally, this work proposes that ABTL0812 exerts its antitumoral activity acting simultaneously on two axes. On one hand, ABTL0812 activates PPAR/ receptors, which induce TRIB3 over-expression and the subsequent Akt and mTORC1 inhibition. On the other hand, ABTL0812 inhibits Des-1 enzyme, resulting in accumulation of long-chain dihydroceramides and the subsequent activation of ER stress. Both axes synergize to activate a robust autophagy which ultimately leads to lysosomal membrane permeabilization and necrosis. In agreement with this, we show that the inhibition of mTORC1 (Everolimus) synergizes with Des-1 inhibition (GT11) to promote autophagy and cytotoxicity

Mecanisme d'acció del nou fàrmac antitumoral ARTL0812: rol de la pseudoquinasa TRIB3, l'estrès reticular i els esfingolípids en la mort mediada per autofàgia

L'ABTL0812 és un derivat lipídic amb activitat antitumoral llicenciat per la companyia biofarmacèutica Ability Pharmaceuticals. En estudis preliminars es va observar que l'ABTL0812 indueix citotoxicitat en un ampli espectre de cèl·lules tumorals humanes i una inhibició del creixement de tumors xenografts derivats de cèl·lules tumorals humanes, propietats que han motivat el seu desenvolupament pre-clínic. A l'actualitat, l'ABTL0812 es troba en Fase Clínica 2 en pacients amb càncer de pulmó escamós i d'endometri avançat (identificador ClinicalTrials.gov: NCT03366480). El nostre laboratori està implicat en caracteritzar el seu mecanisme d'acció antitumoral, utilitzant com a model les cèl·lules MiaPaca2 (adenocarcinoma pancreàtic) i A549 (adenocarcinoma de pulmó). Estudis previs realitzats al laboratori mostren que l'ABTL0812 activa els receptors PPAR i PPAR, que medien en la inducció de mort dependent d'autofàgia sense induir l'aparició de trets típicament apoptòtics. En aquesta Tesi Doctoral, mitjançant assajos de gen reporter luciferasa, quantificació de mRNA per RT-qPCR i assaig d'immunoblot, demostrem que l'activació dels receptors PPAR/ indueix l'activació transcripcional de la pseudoquinasa TRIB3. Una vegada sobre-expressada, TRIB3 uneix Akt i impedeix la seva activació per les quinases activadores PDK1 i mTORC2. Com a conseqüència d'això, s'inhibeix el complex mTORC1. Tanmateix, s'ha constatat que la inhibició del complex mTORC1 a les cèl·lules tumorals humanes MiaPaca2 i A549 no és suficient per induir una autofàgia robusta anàloga a l'observada per l'ABTL0812. Aquest fet va motivar l'estudi sobre si l'estrès reticular podia estar relacionat amb la sobre-expressió de TRIB3 i la mort cel·lular mediada per autofàgia induïdes per l'ABTL0812, tal com s'ha proposat per altres composts anti-tumorals com el tetrahidrocannabinol. En aquest treball hem observat que l'ABTL0812 indueix dilatació del reticle endoplasmàtic i la sobre-expressió dels marcadors d'estrès reticular BiP, ATF4 i CHOP. En conjunt, aquests resultats demostren la inducció d'estrès reticular per part de l'ABTL0812. El bloqueig farmacològic de l'estrès reticular mostra preliminarment que l'estrès reticular media en la citotoxicitat induïda per l'ABTL0812. D'interès, s'ha posat a punt la quantificació dels nivells de mRNA plasmàtics dels marcador d'estrès reticular CHOP i TRIB3, tant en mostres de sang total com a PBMCs purificades, i s'ha constatat que augmenten en els pacients humans en resposta al tractament amb ABTL0812. En l'actualitat, aquests biomarcadors farmacodinàmics s'estan utilitzant a la Fase Clínica 2. L'anàlisi per espectrometria de masses de l'esfingolipidoma de cèl·lules tumorals ha permès observar que l'ABTL0812 indueix l'acumulació de dihidroceramides de cadena llarga, sense alterar els nivells de ceramides. Aquest esdeveniment s'explica pel fet que la incubació amb ABTL0812 resulta en la inhibició de l'enzim desaturasa-1 (Des-1) a la cèl·lula tumoral. Des-1 és l'últim enzim de la via de síntesi de novo de ceramides (catalitza el pas de dihidroceramides a ceramides) i la seva inhibició resulta en l'acumulació de dihidroceramides de cadena llarga, de manera anàloga a la mostrada per l'inhibidor específic de Des-1 GT11. D'interès, el tractament de les cèl·lules tumorals amb la dihidroceramida de cadena curta dideuterada d2c8DhCer (que provoca un augment dels nivells cel·lulars de dihidroceramides) resulta en la inducció d'estrès reticular, autofàgia i citotoxicitat a les cèl·lules tumorals MiaPaca2 i A549, tal com fa l'ABTL0812. L'estudi preliminar dels processos executors de la mort cel·lular induïda per l'ABTL0812 mostra que aquest compost altera la funció mitocondrial (depleció dràstica d'ATP cel·lular) i activa la via canònica de mitofàgia PINK1/parkina/ubiquitina. A més a més, l'ABTL0812 promou l'alliberació citosòlica de catepsines lisosomals, suggerint la inducció de permeabilització de membrana lisosomal (LMP) que explicaria la mort per necrosi observada a les cèl·lules tumorals. Finalment, aquesta Tesi proposa que l'ABTL0812 actuaria de forma paral·lela a través de dos eixos. Per un costat, activaria els receptors PPAR/, que indueixen la sobre-expressió de TRIB3 i la subseqüent inhibició d'Akt i del complex mTORC1. Per l'altre costat, l'ABTL0812 inhibiria l'enzim Des-1, provocant una acumulació de dihidroceramides de cadena llarga i l'activació d'estrès reticular. Ambdós eixos del mecanisme sinergitzen en l'activació d'autofàgia robusta i mort cel·lular, com demostra el tractament combinat amb l'inhibidor específic de mTORC1 Everolimus i l'inhibidor específic de Des-1 GT11.ABTL0812 is a polyunsaturated fatty acid derivative with antitumoral activity licensed by the biopharmaceutical company Ability Pharmaceuticals. ABTL0812 shows cytotoxicity in a wide panel of human tumor cell lines and induces tumor growth inhibition in human tumor cell-derived xenografts. This have encouraged its pre-clinical and clinical development. ABTL0812 recently started Phase 2 Clinical trials in patients with advanced endometrial cancer and squamous NSCLC, as a first line of treatment in combination with paclitaxel and carboplatin (ClinicalTrials.gov: NCT03366480). Our laboratory is involved in the characterization of ABTL0812's antitumoral mechanism of action, using MiPaca2 (pancreatic adenocarcinoma) and A549 (lung adenocarcinoma) cell lines as models. Previous studies carried out in our laboratory uncovered that in cells ABTL0812 activates peroxisome proliferator-activated receptors PPAR/ receptors, inducing autophagy-mediated cancer cell death without activating apoptosis. Here, by using gene reporter luciferase assay, qRT-PCR mRNA quantification and immunoblot analysis, we show that ABTL0812 activates PPAR-mediated transcription of Tribbles 3 (TRIB3) pseudokinase. Over-expressed TRIB3 then binds and inhibits Akt, preventing its activation by PDK1 and mTORC2 upstream kinases, resulting in inhibition of the oncogenic Akt/mTORC1 axis. However, we found that mTORC1 inhibition is not enough to induce robust autophagy in MiaPaca2 and A549 cell lines, as it does ABTL0812. Thus, we investigated whether endoplasmic reticulum (ER) stress could also account for ABTL0812-induced TRIB3 overexpression, as it has been proposed for other antitumoral drugs such as tetrahydrocannabinol. We found ABTL0812 induces endoplasmic reticulum dilatation and over-expression of the endoplasmic reticulum stress markers BiP, ATF4 and CHOP (both mRNA and protein levels), indicating that ABTL0812 induces ER stress in these tumor cells. We also show preliminary pharmacological data suggesting that ER stress has a role in mediating ABTL0812-induced cytotoxicity. Remarkably, we have optimized a protocol for the quantification of TRIB3 and CHOP mRNAs (qRT-PCR) in blood and purified PBMCs from patients enrolled in Clinical Phase 2. We describe increased levels of CHOP and TRIB3 mRNAs in response to ABTL0812 treatment. Furthermore, we have proposed and optimized RT quantification of the ER stress genes TRIB3 and CHOP as reliable pharmacodynamic biomarkers for the ongoing Phase 2 Clinical trials. Given the role of sphingolipids in initiating the ER stress, we undertook a comprehensive mass-spec analysis of cellular sphingolipids to show that ABTL0812 induces long-chain dihydroceramides accumulation without affecting ceramide levels. In cells, dihydroceramides are converted into ceramides by the desaturase-1 (Des-1) enzyme. Enzymatic analysis demonstrated that ABTL0812 treatment results in inhibition of Des-1 activity in vitro and in cellular assays, provoking an accumulation of long-chain dihydroceramides, analogously to that induced by Des-1 specific inhibitor GT11. Interestingly, we show that treatment with the dideuterated short-chain dihydroceramide d2c8DhCer (which induces an increase of cellular dihydroceramides) results in endoplasmic reticulum stress, autophagy and cytotoxicity in MiaPaca2 and A549 cell lines. Preliminary characterization of ABTL0812-induced cell death shows that this compound alters mitochondrial function (induces a drastic depletion of cellular ATP) and it activates the canonic mitophagy pathway PINK1/parkin/ubiquitin. Furthermore, ABTL0812 induces cytosolic release lysosomal cathepsin B, suggesting a lysosomal membrane permeabilization (LMP) that would explain the necrotic cell death observed in tumor cells. Finally, this work proposes that ABTL0812 exerts its antitumoral activity acting simultaneously on two axes. On one hand, ABTL0812 activates PPAR/ receptors, which induce TRIB3 over-expression and the subsequent Akt and mTORC1 inhibition. On the other hand, ABTL0812 inhibits Des-1 enzyme, resulting in accumulation of long-chain dihydroceramides and the subsequent activation of ER stress. Both axes synergize to activate a robust autophagy which ultimately leads to lysosomal membrane permeabilization and necrosis. In agreement with this, we show that the inhibition of mTORC1 (Everolimus) synergizes with Des-1 inhibition (GT11) to promote autophagy and cytotoxicity

ERK5 Inhibition Induces Autophagy-Mediated Cancer Cell Death by Activating ER Stress

Autophagy is a highly conserved intracellular process that preserves cellular homeostasis by mediating the lysosomal degradation of virtually any component of the cytoplasm. Autophagy is a key instrument of cellular response to several stresses, including endoplasmic reticulum (ER) stress. Cancer cells have developed high dependency on autophagy to overcome the hostile tumor microenvironment. Thus, pharmacological activation or inhibition of autophagy is emerging as a novel antitumor strategy. ERK5 is a novel member of the MAP kinase family that is activated in response to growth factors and different forms of stress. Recent work has pointed ERK5 as a major player controlling cancer cell proliferation and survival. Therefore small-molecule inhibitors of ERK5 have shown promising therapeutic potential in different cancer models. Here, we report for the first time ERK5 as a negative regulator of autophagy. Thus, ERK5 inhibition or silencing induced autophagy in a panel of human cancer cell lines with different mutation patterns. As reported previously, ERK5 inhibitors (ERK5i) induced apoptotic cancer cell death. Importantly, we found that autophagy mediates the cytotoxic effect of ERK5i, since ATG5 ˉ / ˉ autophagy-deficient cells viability was not affected by these compounds. Mechanistically, ERK5i stimulated autophagic flux independently of the canonical regulators AMPK or mTORC1. Moreover, ERK5 inhibition resulted in ER stress and activation of the Unfolded Protein Response (UPR) pathways. Specifically, ERK5i induced expression of the ER luminal chaperone BiP (a hallmark of ER stress), the UPR markers CHOP and ATF4, and the spliced form of XBP1. Pharmacological inhibition of UPR with chemical chaperone TUDC, or ATF4 silencing, resulted in impaired ERK5i-mediated UPR, autophagy and cytotoxicity. Overall, our results suggest that ERK5 inhibition induces autophagy-mediated cancer cell death by activating ER stress. Since ERK5 inhibition sensitizes cancer cells and tumors to chemotherapy, future work will determine the relevance of UPR and autophagy in the combined use of chemotherapy and ERK5i to tackle Cancer

Grp78 overexpression triggers PINK1-IP3R-mediated neuroprotective mitophagy

Altres ajuts: Marató de TV3 (201607.10)An experimental model of spinal root avulsion (RA) is useful to study causal molecular programs that drive retrograde neurodegeneration after neuron-target disconnection. This neurode-generative process shares common characteristics with neuronal disease-related processes such as the presence of endoplasmic reticulum (ER) stress and autophagy flux blockage. We previously found that the overexpression of GRP78 promoted motoneuronal neuroprotection after RA. After that, we aimed to unravel the underlying mechanism by carrying out a comparative unbiased proteomic analysis and pharmacological and genetic interventions. Unexpectedly, mitochondrial factors turned out to be most altered when GRP78 was overexpressed, and the abundance of engulfed mitochondria, a hallmark of mitophagy, was also observed by electronic microscopy in RA-injured motoneurons after GRP78 overexpression. In addition, GRP78 overexpression increased LC3-mitochondria tag-ging, promoted PINK1 translocation, mitophagy induction, and recovered mitochondrial function in ER-stressed cells. Lastly, we found that GRP78-promoted pro-survival mitophagy was mediated by PINK1 and IP3R in our in vitro model of motoneuronal death. This data indicates a novel relationship between the GRP78 chaperone and mitophagy, opening novel therapeutical options for drug design to achieve neuroprotection

The anti-cancer drug ABTL0812 induces ER stress-mediated cytotoxic autophagy by increasing dihydroceramide levels in cancer cells.

ABTL0812 is a first-in-class small molecule with anti-cancer activity, which is currently in clinical evaluation in a phase 2 trial in patients with advanced endometrial and squamous non-small cell lung carcinoma (NCT03366480). Previously, we showed that ABTL0812 induces TRIB3 pseudokinase expression, resulting in the inhibition of the AKT-MTORC1 axis and macroautophagy/autophagy-mediated cancer cell death. However, the precise molecular determinants involved in the cytotoxic autophagy caused by ABTL0812 remained unclear. Using a wide range of biochemical and lipidomic analyses, we demonstrated that ABTL0812 increases cellular long-chain dihydroceramides by impairing DEGS1 (delta 4-desaturase, sphingolipid 1) activity, which resulted in sustained ER stress and activated unfolded protein response (UPR) via ATF4-DDIT3-TRIB3 that ultimately promotes cytotoxic autophagy in cancer cells. Accordingly, pharmacological manipulation to increase cellular dihydroceramides or incubation with exogenous dihydroceramides resulted in ER stress, UPR and autophagy-mediated cancer cell death. Importantly, we have optimized a method to quantify mRNAs in blood samples from patients enrolled in the ongoing clinical trial, who showed significant increased DDIT3 and TRIB3 mRNAs. This is the first time that UPR markers are reported to change in human blood in response to any drug treatment, supporting their use as pharmacodynamic biomarkers for compounds that activate ER stress in humans. Finally, we found that MTORC1 inhibition and dihydroceramide accumulation synergized to induce autophagy and cytotoxicity, phenocopying the effect of ABTL0812. Given the fact that ABTL0812 is under clinical development, our findings support the hypothesis that manipulation of dihydroceramide levels might represents a new therapeutic strategy to target cancer.This work was supported by the Centre for Industrial Technological Development [CDTI,INNOGLOBAL/20171061]; European Regional Development Fund [PI18/00442 and PI15/00339]; European Regional Development Fund [INNPACTO/IPT-2012-0614-010000, RETOS RTC-2017-6261-1, SAF2015-64237-R]; Fundació la Marató de TV3 [20134031]; H2020 Marie Skłodowska-Curie Actions [TRAIN GA721532]; Instituto de Salud Carlos III [PI15/00339]; Instituto de Salud Carlos III [PI18/00442]; Ministerio de Ciencia, Innovación y Universidades [CTQ2017- 85378-R]; Ministerio de Economía y Competitividad [RTC-2015-3821-1]; Ministerio de Economía y Competitividad [RTC-2017-6261-1]; Ministerio de Economía y Competitividad [EMP-TU-2015-4576]; Ministerio de Economía y Competitividad [RETOS RTC-2017-6261-1]; Ministerio de Economía y Competitividad [BFU2016-78154-R]; Ministerio de Economía y Competitividad [INNPACTO/IPT-2012-0614-010000]; Ministerio de Economía y Competitividad [SAF2015-64237-R]; Ministerio de Economía y Competitividad [RTC-2014-1532-1].Peer reviewe