Mounira Chalabi-Dchar1, Stéphanie Cassant-Sourdy1, Camille Duluc1, Marjorie Fanjul1, Hubert Lulka1, Rémi Samain1, Catherine Roche2, Florence Breibach3, Marie-Bernadette Delisle3, Mary Poupot1, Marlène Dufresne1, Takeshi Shimaoka4, Shin Yonehara5, Muriel Mathonnet6, Stéphane Pyronnet1, Corinne Bousquet7. 1. INSERM UMR-1037, Toulouse University, Cancer Research Center of Toulouse, Equipe Labellisée Ligue Contre le Cancer and Laboratoire d'Excellence Toulouse Cancer, Toulouse, France. 2. UMR7286 CNRS-Aix-Marseille University, Neurobiology and Neurophysiology Research Center of Marseille, and Laboratory of Molecular Biology, AP-HM Conception, Marseille, France. 3. Pathology Department, Toulouse Hospitals, Toulouse, France. 4. Department of Molecular Preventive Medicine, Graduate School of Medicine, Tokyo University, Tokyo, Japan. 5. Laboratory of Molecular and Cellular Biology, Graduate School of Biostudies, Kyoto University, Kyoto, Japan. 6. EA 3842 Laboratory, Medicine and Pharmacy Faculties, Limoges University, Limoges, France. 7. INSERM UMR-1037, Toulouse University, Cancer Research Center of Toulouse, Equipe Labellisée Ligue Contre le Cancer and Laboratoire d'Excellence Toulouse Cancer, Toulouse, France. Electronic address: corinne.bousquet@inserm.fr.
Abstract
BACKGROUND & 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.
BACKGROUND & 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 humanPDAC. 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.
Authors: Jérémy Nigri; Meritxell Gironella; Christian Bressy; Elena Vila-Navarro; Julie Roques; Sophie Lac; Caroline Bontemps; Coraline Kozaczyk; Jérôme Cros; Daniel Pietrasz; Raphaël Maréchal; Jean-Luc Van Laethem; Juan Iovanna; Jean-Baptiste Bachet; Emma Folch-Puy; Richard Tomasini Journal: Cell Mol Life Sci Date: 2017-06-27 Impact factor: 9.261