Pharmacological targeting of the protein synthesis mTOR/4E-BP1 pathway in cancer-associated fibroblasts abrogates pancreatic tumourchemoresistance

International audiencePancreatic ductal adenocarcinoma (PDAC) is extremely stroma-rich. Cancer-associated fibroblasts (CAFs) secrete proteins that activate survival and promote chemoresistance of cancer cells. Our results demonstrate that CAF secretome-triggered chemoresistance is abolished upon inhibition of the protein synthesis mTOR/4E-BP1 regulatory pathway which we found highly activated in primary cultures of -SMA-positive CAFs, isolated from human PDAC resections. CAFs selectively express the sst1 somatostatin receptor. The SOM230 analogue (Pasireotide) activates the sst1 receptor and inhibits the mTOR/4E-BP1 pathway and the resultant synthesis of secreted proteins including IL-6. Consequently, tumour growth and chemoresistance in nude mice xenografted with pancreatic cancer cells and CAFs, or with pieces of resected human PDACs, are reduced when chemotherapy (gemcitabine) is combined with SOM230 treatment. While gemcitabine alone has marginal effects, SOM230 is permissive to gemcitabine-induced cancer cell apoptosis and acts as an antifibrotic agent. We propose that selective inhibition of CAF protein synthesis with sst1-directed pharmacological compounds represents an anti-stromal-targeted therapy with promising chemosensitization potential

The Cdx2 homeobox gene suppresses intestinal tumorigenesis through non-cell-autonomous mechanisms

Developmental genes contribute to cancer, as reported for the homeobox gene Cdx2 playing a tumor suppressor role in the gut. In this study, we show that human colon cancers exhibiting the highest reduction in CDX2 expression belong to the serrated subtype with the worst evolution. In mice, mosaic knockout of Cdx2 in the adult intestinal epithelium induces the formation of imperfect gastric-type metaplastic lesions. The metaplastic knockout cells do not spontaneously become tumorigenic. However, they induce profound modifications of the microenvironment that facilitate the tumorigenic evolution of adjacent Cdx2-intact tumor-prone cells at the surface of the lesions through NF-κB activation, induction of inducible nitric oxide synthase, and stochastic loss of function of Apc. This study presents a novel paradigm in that metaplastic cells, generally considered as precancerous, can induce tumorigenesis from neighboring nonmetaplastic cells without themselves becoming cancerous. It unveils the novel property of non-cell-autonomous tumor suppressor gene for the Cdx2 gene in the gut

Le ciblage pharmacologique des cellules stellaires pancréatiques sensibilise les cellules cancéreuses pancréatiques à l'action cytotoxique de la chimiothérapie gemcitabine

L'adénocarcinome pancréatique canalaire présente une composante stromale très abondante. Les fibroblastes associés au cancer (CAFs) sécrètent énormément de facteurs participant à la survie des cellules cancéreuses ainsi qu'à leur chimiorésistance. Nos travaux démontrent la possibilité d'atténuer les propriétés chmioprotectrices des CAF en ciblant leur voie de signalisation mTOR/4E-BP1 qui est retrouvée fortement activée notamment dans les primo cultures de CAF isolées à partir de résections chirurgicales humaines. Les CAF expriment exclusivement le récepteur de somatostatine sst1. L'analogue SOM230 (Pasiréotide) active ce récepteur et inhibe la signalisation mTOR/4E-BP1 conduisant à une nette diminution du niveau de synthèse protéique des CAF. En conséquence, la croissance tumorale ainsi que la chimiorésistance des tumeurs (co xénogreffes réalisées chez la souris nude) ont été limitées lorsque la combinaison thérapeutique SOM230 / Gemcitabine a été appliquée. Tandis que, seule, la gemcitabine ne présente pas d'effet, le SOM230 sensibilise la tumeur à son action cytotoxique en agissant sur le stroma et en présentant un rôle anti fibrotique. Nous proposons alors une nouvelle approche thérapeutique qui consiste à cibler la synthèse protéique des CAF exprimant sst1 par un analogue de la somatostatine afin de limiter leur potentiel chimio protecteur et restaurer indirectement la sensibilité des cellules cancéreuses pancréatiques à l'action cytotoxique de la gemcitabine.Pancreatic ductal adenocarcinoma (PDAC) is extremely stroma-rich. Cancer-associated fibroblasts (CAFs) secrete proteins that activate survival and promote chemoresistance of cancer cells. Our results demonstrate that CAF secretome-triggered chemoresistance is abolished upon inhibition of the protein synthesis mTOR/4E-BP1 regulatory pathway which we found highly activated in primary cultures of a-SMA-positive CAFs, isolated from human PDAC resections. CAFs selectively express the sst1 somatostatin receptor. The SOM230 analogue (Pasireotide) activates the sst1 receptor and inhibits the mTOR/4E-BP1 pathway and the resultant synthesis of secreted proteins including IL-6. Consequently, tumour growth and chemoresistance in nude mice xenografted with pancreatic cancer cells and CAFs, or with pieces of resected human PDACs, are reduced when chemotherapy (gemcitabine) is combined with SOM230 treatment. While gemcitabine alone has marginal effects, SOM230 is permissive to gemcitabine-induced cancer cell apoptosis and acts as an antifibrotic agent. We propose that selective inhibition of CAF protein synthesis with sst1-directed pharmacological compounds represents an anti-stromal-targeted therapy with promising chemosensitization potential

Pharmacological targeting of the pancreatic stellate cells abrogates pancreatic cancer cells chemoresistance to gemcitabine

L'adénocarcinome pancréatique canalaire présente une composante stromale très abondante. Les fibroblastes associés au cancer (CAFs) sécrètent énormément de facteurs participant à la survie des cellules cancéreuses ainsi qu'à leur chimiorésistance. Nos travaux démontrent la possibilité d'atténuer les propriétés chmioprotectrices des CAF en ciblant leur voie de signalisation mTOR/4E-BP1 qui est retrouvée fortement activée notamment dans les primo cultures de CAF isolées à partir de résections chirurgicales humaines. Les CAF expriment exclusivement le récepteur de somatostatine sst1. L'analogue SOM230 (Pasiréotide) active ce récepteur et inhibe la signalisation mTOR/4E-BP1 conduisant à une nette diminution du niveau de synthèse protéique des CAF. En conséquence, la croissance tumorale ainsi que la chimiorésistance des tumeurs (co xénogreffes réalisées chez la souris nude) ont été limitées lorsque la combinaison thérapeutique SOM230 / Gemcitabine a été appliquée. Tandis que, seule, la gemcitabine ne présente pas d'effet, le SOM230 sensibilise la tumeur à son action cytotoxique en agissant sur le stroma et en présentant un rôle anti fibrotique. Nous proposons alors une nouvelle approche thérapeutique qui consiste à cibler la synthèse protéique des CAF exprimant sst1 par un analogue de la somatostatine afin de limiter leur potentiel chimio protecteur et restaurer indirectement la sensibilité des cellules cancéreuses pancréatiques à l'action cytotoxique de la gemcitabine.Pancreatic ductal adenocarcinoma (PDAC) is extremely stroma-rich. Cancer-associated fibroblasts (CAFs) secrete proteins that activate survival and promote chemoresistance of cancer cells. Our results demonstrate that CAF secretome-triggered chemoresistance is abolished upon inhibition of the protein synthesis mTOR/4E-BP1 regulatory pathway which we found highly activated in primary cultures of a-SMA-positive CAFs, isolated from human PDAC resections. CAFs selectively express the sst1 somatostatin receptor. The SOM230 analogue (Pasireotide) activates the sst1 receptor and inhibits the mTOR/4E-BP1 pathway and the resultant synthesis of secreted proteins including IL-6. Consequently, tumour growth and chemoresistance in nude mice xenografted with pancreatic cancer cells and CAFs, or with pieces of resected human PDACs, are reduced when chemotherapy (gemcitabine) is combined with SOM230 treatment. While gemcitabine alone has marginal effects, SOM230 is permissive to gemcitabine-induced cancer cell apoptosis and acts as an antifibrotic agent. We propose that selective inhibition of CAF protein synthesis with sst1-directed pharmacological compounds represents an anti-stromal-targeted therapy with promising chemosensitization potential

Anti-metastatic potential of somatostatin analog SOM230: Indirect pharmacological targeting of pancreatic cancer-associated fibroblasts

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Fine-tuning and autoregulation of the intestinal determinant and tumor suppressor homeobox gene CDX2 by alternative splicing

On the basis of phylogenetic analyses, we uncovered a variant of the CDX2 homeobox gene, a major regulator of the development and homeostasis of the gut epithelium, also involved in cancer. This variant, miniCDX2, is generated by alternative splicing coupled to alternative translation initiation, and contains the DNA-binding homeodomain but is devoid of transactivation domain. It is predominantly expressed in crypt cells, whereas the CDX2 protein is present in crypt cells but also in differentiated villous cells. Functional studies revealed a dominant-negative effect exerted by miniCDX2 on the transcriptional activity of CDX2, and conversely similar effects regarding several transcription-independent functions of CDX2. In addition, a regulatory role played by the CDX2 and miniCDX2 homeoproteins on their pre-mRNA splicing is displayed, through interactions with splicing factors. Overexpression of miniCDX2 in the duodenal Brunner glands leads to the expansion of the territory of these glands and ultimately to brunneroma. As a whole, this study characterized a new and original variant of the CDX2 homeobox gene. The production of this variant represents not only a novel level of regulation of this gene, but also a novel way to fine-tune its biological activity through the versatile functions exerted by the truncated variant compared to the full-length homeoprotein. This study highlights the relevance of generating protein diversity through alternative splicing in the gut and its diseases

Loss of Somatostatin Receptor Subtype 2 Promotes Growth of KRAS-Induced Pancreatic Tumors in Mice by Activating PI3K Signaling and Overexpression of CXCL16

Comment inSomatostatin receptor subtype 2 as pancreatic tumorigenesis suppressor: identification of a new targetable signaling node. [Gastroenterology. 2015]International audienceBACKGROUND & AIMS:The KRAS gene is mutated in most pancreatic ductal adenocarcinomas (PDAC). Expression of this KRAS oncoprotein in mice is sufficient to initiate carcinogenesis but not progression to cancer. Activation of phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K) is required for KRAS for induction and maintenance of PDAC in mice. The somatostatin receptor subtype 2 (sst2) inhibits PI3K, but sst2 expression is lost during the development of human PDAC. We investigated the effects of sst2 loss during KRAS-induced PDAC development in mice.METHODS:We analyzed tumor growth in mice that expressed the oncogenic form of KRAS (KRAS(G12D)) in pancreatic precursor cells, as well as sst2+/- and sst2-/-, and in crossed KRAS(G12D);sst2+/- and KRAS(G12D);sst2-/- mice. Pancreatic tissues and acini were collected and assessed by histologic, immunoblot, immunohistochemical, and reverse-transcription polymerase chain reaction analyses. We also compared protein levels in paraffin-embedded PDAC samples from patients vs heathy pancreatic tissues from individuals without pancreatic cancer.RESULTS:In sst2+/- mice, PI3K was activated and signaled via AKT (PKB; protein kinase B); when these mice were crossed with KRAS(G12D) mice, premalignant lesions, tumors, and lymph node metastases developed more rapidly than in KRAS(G12D) mice. In crossed KRAS(G12D);sst2+/- mice, activation of PI3K signaling via AKT resulted in activation of nuclear factor-κB (NF-κB), which increased KRAS activity and its downstream pathways, promoting initiation and progression of neoplastic lesions. We found this activation loop to be mediated by PI3K-induced production of the chemokine CXCL16. Administration of a CXCL16-neutralizing antibody to KRAS(G12D) mice reduced activation of PI3K signaling to AKT and NF-κB, blocking carcinogenesis. Levels of CXCL16 and its receptor CXCR6 were significantly higher in PDAC tissues and surrounding acini than in healthy pancreatic tissues from mice or human beings. In addition, expression of sst2 was progressively lost, involving increased PI3K activity, in mouse lesions that expressed KRAS(G12D) and progressed to PDAC.CONCLUSIONS:Based on analyses of mice, loss of sst2 from pancreatic tissues activates PI3K signaling via AKT, leading to activation of NF-κB, amplification of oncogenic KRAS signaling, increased expression of CXCL16, and pancreatic tumor formation. CXCL16 might be a therapeutic target for PDAC