Somatostatin receptor subtype 2 sensitizes human pancreatic cancer cells to death ligand-induced apoptosis
Somatostatin receptor subtype 2 sensitizes human pancreatic cancer cells to death ligand-induced apoptosis
Somatostatin receptor subtype 2 (sst2) gene expression is lost in 90% of human pancreatic adenocarcinomas. We previously demonstrated that stable sst2 transfection of human pancreatic BxPC-3 cells, which do not endogenously express sst2, inhibits cell proliferation, tumorigenicity, and metastasis. These sst2 effects occur as a consequence of an autocrine sst2-dependent loop, whereby sst2 induces expression of its own ligand, somatostatin. Here we investigated whether sst2 induces apoptosis in sst2-transfected BxPC-3 cells. Expression of sst2 induced a 4.4- ± 0.05-fold stimulation of apoptosis in BxPC-3 through the activation of tyrosine phosphatase SHP-1. sst2 also sensitized these cells to apoptosis induced by tumor necrosis factor α (TNFα), enhancing it 4.1- ± 1.5-fold. Apoptosis in BxPC-3 cells mediated by TNF-related apoptosis-inducing ligand (TRAIL) and CD95L was likewise increased 2.3- ± 0.5-fold and 7.4- ± 2.5-fold, respectively. sst2-dependent activation and cell sensitization to death ligand-induced apoptosis involved activation of the executioner caspases, key factors in both death ligand- or mitochondria-mediated apoptosis. sst2 affected both pathways: first, by up-regulating expression of TRAIL and TNFα receptors, DR4 and TNFRI, respectively, and sensitizing the cells to death ligand-induced initiator capase-8 activation, and, second, by down-regulating expression of the antiapoptotic mitochondrial Bcl-2 protein. These results are of interest for the clinical management of chemoresistant pancreatic adenocarcinoma by using a combined gene therapy based on the cotransfer of genes for both the sst2 and a nontoxic death ligand.
- French Institute of Health and Medical Research France
- Inserm France
- Institut Claudius Regaud France
Fas Ligand Protein, Membrane Glycoproteins, Base Sequence, Protein Tyrosine Phosphatase, Non-Receptor Type 6, Intracellular Signaling Peptides and Proteins, Apoptosis, Polymerase Chain Reaction, Recombinant Proteins, Enzyme Activation, Pancreatic Neoplasms, TNF-Related Apoptosis-Inducing Ligand, Kinetics, RNA, Ribosomal, 18S, Humans, RNA, Messenger, Receptors, Somatostatin, Enzyme Inhibitors, Protein Tyrosine Phosphatases, Apoptosis Regulatory Proteins, DNA Primers
Fas Ligand Protein, Membrane Glycoproteins, Base Sequence, Protein Tyrosine Phosphatase, Non-Receptor Type 6, Intracellular Signaling Peptides and Proteins, Apoptosis, Polymerase Chain Reaction, Recombinant Proteins, Enzyme Activation, Pancreatic Neoplasms, TNF-Related Apoptosis-Inducing Ligand, Kinetics, RNA, Ribosomal, 18S, Humans, RNA, Messenger, Receptors, Somatostatin, Enzyme Inhibitors, Protein Tyrosine Phosphatases, Apoptosis Regulatory Proteins, DNA Primers
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