Influence of corticosteroid treatment on CXCR4 expression in DLBCL

BACKGROUND: CXCR4-targeted radioligand therapy (RLT) with [(177)Lu]Lu/[(90)Y]Y-PentixaTher has recently evolved as a promising therapeutic option for patients with advanced hematological cancers. Given their advanced disease stage, most patients scheduled for PentixaTher RLT require concomitant or bridging chemotherapy to prevent intermittent tumor progression. These (mostly combination) therapies may cause significant downregulation of tumoral CXCR4 expression, challenging the applicability of PentixaTher RLT. This study therefore aimed at investigating the influence of corticosteroids, a central component of these chemotherapies, on CXCR4 regulation in diffuse large B cell lymphoma (DLBCL). METHODS: Different DLBCL cell lines (Daudi, OCI-LY1, SUDHL-4, -5-, -6 and -8) as well as the human T-cell lymphoma cell line Jurkat were incubated with Dexamethasone (Dex; 0.5 and 5 µM, respectively) and Prednisolone (Pred; 5 and 50 µM, respectively) for different time points (2 h, 24 h). Treatment-induced modulation of cellular CXCR4 surface expression was assessed via flow cytometry (FC) and compared to untreated cells. A radioligand binding assay with [(125)I]CPCR4.3 was performed in parallel using the same cells. To quantify potential corticosteroid treatment effects on tumoral CXCR4 expression in vivo, OCI-LY1 bearing NSG mice were injected 50 µg Dex/mouse i.p. (daily for 6 days). Then, a biodistribution study (1 h p.i.) using [(68)Ga]PentixaTher was performed, and tracer biodistribution in treated (n = 5) vs untreated mice (n = 5) was compared. RESULTS: In the in vitro experiments, a strongly cell line-dependent upregulation of CXCR4 was observed for both Dex and Pred treatment, with negligible differences between the high and low dose. While in Jurkat, Daudi and SUDHL-8 cells, CXCR4 expression remained unchanged, a 1.5- to 3.5-fold increase in CXCR4 cell surface expression was observed for SUDHL-5 < SUDHL-4 /-6 < OCI-LY1 via FC compared to untreated cells. This increase in CXCR4 expression was also reflected in correspondingly enhanced [(125)I]CPCR4.3 accumulation in treated cells, with a linear correlation between FC and radioligand binding data. In vivo, Dex treatment led to a general increase of [(68)Ga]PentixaTher uptake in all organs compared to untreated animals, as a result of a higher tracer concentration in blood. However, we observed an overproportionally enhanced [(68)Ga]PentixaTher uptake in the OCI-LY1 tumors in treated (21.0 ± 5.5%iD/g) vs untreated (9.2 ± 2.8%iD/g) mice, resulting in higher tumor-to-background ratios in the treatment group. CONCLUSION: Overall, corticosteroid treatment (Dex/Pred) consistently induced an upregulation of CXCR4 expression DBLCL cells in vitro, albeit in a very cell line-dependent manner. For the cell line with the most pronounced Dex-induced CXCR4 upregulation, OCI-LY1, the in vitro findings were corroborated by an in vivo biodistribution study. This confirms that at least the corticosteroid component of stabilizing chemotherapy regimens in DLBCL patients prior to [(177)Lu]Lu-PentixaTher RLT does not lead to downregulation of the molecular target CXCR4 and may even have a beneficiary effect. However, further studies are needed to investigate if and to what extent the other commonly used chemotherapeutic agents affect CXCR4 expression on DLBCL to ensure the choice of an appropriate treatment regimen prior to [(177)Lu]Lu/[(90)Y]Y-PentixaTher RLT

In vivo molecular imaging of chemokine receptor CXCR4 expression in patients with advanced multiple myeloma

CXCR4 is a G-protein-coupled receptor that mediates recruitment of blood cells toward its ligand SDF-1. In cancer, high CXCR4 expression is frequently associated with tumor dissemination and poor prognosis. We evaluated the novel CXCR4 probe [(68)Ga]Pentixafor for in vivo mapping of CXCR4 expression density in mice xenografted with human CXCR4-positive MM cell lines and patients with advanced MM by means of positron emission tomography (PET). [(68)Ga]Pentixafor PET provided images with excellent specificity and contrast. In 10 of 14 patients with advanced MM [(68)Ga]Pentixafor PET/CT scans revealed MM manifestations, whereas only nine of 14 standard [(18)F]fluorodeoxyglucose PET/CT scans were rated visually positive. Assessment of blood counts and standard CD34(+) flow cytometry did not reveal significant blood count changes associated with tracer application. Based on these highly encouraging data on clinical PET imaging of CXCR4 expression in a cohort of MM patients, we conclude that [(68)Ga]Pentixafor PET opens a broad field for clinical investigations on CXCR4 expression and for CXCR4-directed therapeutic approaches in MM and other diseases

CXCR4 hyperactivation cooperates with TCL1 in CLL development and aggressiveness

Aberrant CXCR4 activity has been implicated in lymphoma pathogenesis, disease progression, and resistance to therapies. Using a mouse model with a gain-of-function CXCR4 mutation (CXCR4(C1013G)) that hyperactivates CXCR4 signaling, we identified CXCR4 as a crucial activator of multiple key oncogenic pathways. CXCR4 hyperactivation resulted in an expansion of transitional B1 lymphocytes, which represent the precursors of chronic lymphocytic leukemia (CLL). Indeed, CXCR4 hyperactivation led to a significant acceleration of disease onset and a more aggressive phenotype in the murine Eµ-TCL1 CLL model. Hyperactivated CXCR4 signaling cooperated with TCL1 to cause a distinct oncogenic transcriptional program in B cells, characterized by PLK1/FOXM1-associated pathways. In accordance, Eµ-TCL1;CXCR4(C1013G) B cells enriched a transcriptional signature from patients with Richter’s syndrome, an aggressive transformation of CLL. Notably, MYC activation in aggressive lymphoma was associated with increased CXCR4 expression. In line with this finding, additional hyperactive CXCR4 signaling in the Eµ-Myc mouse, a model of aggressive B-cell cancer, did not impact survival. In summary, we here identify CXCR4 hyperactivation as a co-driver of an aggressive lymphoma phenotype

NOXA expression drives synthetic lethality to RUNX1 inhibition in pancreatic cancer

Evasion from drug-induced apoptosis is a crucial mechanism of cancer treatment resistance. The proapoptotic protein NOXA marks an aggressive pancreatic ductal adenocarcinoma (PDAC) subtype. To identify drugs that unleash the death-inducing potential of NOXA, we performed an unbiased drug screening experiment. In NOXA-deficient isogenic cellular models, we identified an inhibitor of the transcription factor heterodimer CBFβ/RUNX1. By genetic gain and loss of function experiments, we validated that the mode of action depends on RUNX1 and NOXA. Of note is that RUNX1 expression is significantly higher in PDACs compared to normal pancreas. We show that pharmacological RUNX1 inhibition significantly blocks tumor growth in vivo and in primary patient-derived PDAC organoids. Through genome-wide analysis, we detected that RUNX1-loss reshapes the epigenetic landscape, which gains H3K27ac enrichment at the NOXA promoter. Our study demonstrates a previously unknown mechanism of NOXA-dependent cell death, which can be triggered pharmaceutically. Therefore, our data show a way to target a therapy-resistant PDAC, an unmet clinical need

Genetic alterations of the SUMO isopeptidase SENP6 drive lymphomagenesis and genetic instability in diffuse large B-cell lymphoma

SUMOylation is a post-translational modification of proteins that regulates these proteins' localization, turnover or function. Aberrant SUMOylation is frequently found in cancers but its origin remains elusive. Using a genome-wide transposon mutagenesis screen in a MYC-driven B-cell lymphoma model, we here identify the SUMO isopeptidase (or deconjugase) SENP6 as a tumor suppressor that links unrestricted SUMOylation to tumor development and progression. Notably, SENP6 is recurrently deleted in human lymphomas and SENP6 deficiency results in unrestricted SUMOylation. Mechanistically, SENP6 loss triggers release of DNA repair- and genome maintenance-associated protein complexes from chromatin thereby impairing DNA repair in response to DNA damages and ultimately promoting genomic instability. In line with this hypothesis, SENP6 deficiency drives synthetic lethality to Poly-ADP-Ribose-Polymerase (PARP) inhibition. Together, our results link SENP6 loss to defective genome maintenance and reveal the potential therapeutic application of PARP inhibitors in B-cell lymphoma

Functional imaging in combination with mutation status aids prediction of response to inhibiting B-cell receptor signaling in lymphoma.

Aberrant B-cell receptor (BCR) signaling is known to contribute to malignant transformation. Two small molecule inhibitors targeting BCR pathway signaling include ibrutinib, a Bruton&#39;s tyrosine kinase (BTK) inhibitor, and idelalisib, a specific Phosphatidylinositol-4,5-bisphosphate 3-kinase delta (PI3Kd) inhibitor, both of which have been approved for use in haematological malignancies. Despite the identification of various diffuse large B-cell lymphoma (DLBCL) subtypes, mutation status alone is not sufficient to predict patient response and therapeutic resistance can arise. Herein we apply early molecular imaging across alternative activated B-cell (ABC) and germinal center B-cell (GCB) DLBCL subtypes to investigate the effects of BCR pathway inhibition. Treatment with both inhibitors adversely affected cell growth and viability. These effects were partially predictable based upon mutation status. Accordingly, very early 2-deoxy-2-[18F]fluoro-D-glucose positron emission tomography ( 18 F-FDG-PET) and 3&#39;-deoxy-3&#39;[18F]-fluorothymidine positron emission tomography ( 18 F-FLT-PET) reported tumour regression and reductions in tumour metabolism and proliferation upon treatment. Furthermore, matrix-assisted laser desorption ionization imaging mass spectrometry (MALDI IMS) identified alterations in the proteome of a model of ABC DLBCL upon treatment with ibrutinib or idelalisib. In conclusion we demonstrate that very early molecular imaging adds predictive value in addition to mutational status of DLBCL that may be useful in directing patient therapy