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Hypothalamic neuropeptides named hypocretin/orexins which were identified in 1998 regulate critical functions such as wakefulness in the central nervous system. These past 20 years had revealed that orexins/receptors system was also present in the peripheral nervous system where they participated to the regulation of multiple functions including blood pressure regulation, intestinal motility, hormone secretion, lipolyze and reproduction functions. Associated to these peripheral functions, it was found that orexins and their receptors were involved in various diseases such as acute/chronic inflammation, metabolic syndrome and cancers. The present review suggests that orexins or the orexin neural circuitry represent potential therapeutic targets for the treatment of multiple pathologies related to inflammation including intestinal bowel disease, multiple sclerosis and septic shock, obesity and digestive cancers.

Pancreatic ductal adenocarcinoma (PDAC) is still the poorest prognostic tumor of the digestive system. We investigated the antitumoral role of orexin-A and almorexant in PDAC. We analyzed the orexin receptor type 1 (OX1R) expression by immunohistochemistry in human normal pancreas, PDAC and its precursor dysplastic intraepithelial lesions. We used PDAC-derived cell lines and fresh tissue slices to study the apoptotic role of hypocretin-1/orexin-A and almorexant in vitro and ex vivo. We analyzed in vivo the hypocretin-1/orexin-A and almorexant effect on tumor growth in mice xenografted with PDAC cell lines expressing, or not, OX1R. Ninety-six percent of PDAC expressed OX1R, while adjacent normal exocrine pancreas did not. OX1R was expressed in pre-cancerous lesions. In vitro, under hypocretin-1/orexin-A and almorexant, the OX1R-positive AsPC-1 cells underwent apoptosis, abolished by the tyrosine phosphatase SHP2 inhibitor, NSC-87877, whereas the OX1R-negative HPAF-II cell line did not. These effects were mediated by phosphorylation of OX1R and recruitment of SHP2. Ex vivo, caspase-3 positive tumor cells were significantly higher in fresh tumour slices treated 48h with hypocretin-1/orexin-A, as compared to control, whereas cellular proliferation, assessed by Ki-67 index, was not modified. In vivo, when AsPC-1 cells or patient-derived cells were xenografted in nude mice, hypocretin-1/orexin-A or almorexant, administrated both starting the day of cell line inoculation or after tumoral development, strongly slowed tumor growth. Hypocretin-1/orexin-A and almorexant induce, through OX1R, the inhibition of PDAC cellular growth by apoptosis. Hypocretins/orexins and almorexant might be powerful candidates for the treatment of PDAC.

International audience; Orexins (orexin-A and orexin-B) are hypothalamic peptides that are produced by the same precursor and are involved in sleep/wake control, which is mediated by two G protein-coupled receptor subtypes, OX1R and OX2R. Ulcerative colitis (UC) is an inflammatory bowel disease, (IBD) which is characterized by long-lasting inflammation and ulcers that affect the colon and rectum mucosa and is known to be a significant risk factor for colon cancer development. Based on our recent studies showing that OX1R is aberrantly expressed in colon cancer, we wondered whether orexin-A could play a role in UC. Immunohistochemistry studies revealed that OX1R is highly expressed in the affected colonic epithelium of most UC patients, but not in the non-affected colonic mucosa. Injection of exogenous orexin-A specifically improved the inflammatory symptoms in the two colitis murine models. Conversely, injection of inactive orexin-A analog, OxB7-28 or OX1R specific antagonist SB-408124 did not have anti-inflammatory effect. Moreover, treatment with orexin-A in DSS-colitis induced OX1R −/− knockout mice did not have any protective effect. The orexin-A anti-inflammatory effect was due to the decreased expression of pro-inflammatory cytokines in immune cells and specifically in T-cells isolated from colonic mucosa. Moreover, orexin-A inhibited canonical NFκB activation in an immune cell line and in intestinal epithelial cell line. These results suggest that orexin-A might represent a promising alternative to current UC therapies.

Orexins (OxA and OxB) also termed hypocretins are hypothalamic neuropeptides involved in central nervous system (CNS) to control the sleep/wake process which is mediated by two G protein-coupled receptor subtypes, OX1R, and OX2R. Beside these central effects, orexins also play a role in various peripheral organs such as the intestine, pancreas, adrenal glands, kidney, adipose tissue and reproductive tract.In the past few years, an unexpected anti-tumoral role of orexins mediated by a new signaling pathway involving the presence of two immunoreceptor tyrosine-based inhibitory motifs (ITIM) in both orexin receptors subtypes, the recruitment of the phosphotyrosine phosphatase SHP2 and the induction of mitochondrial apoptosis has been elucidated. In the present review, we will discuss the anti-tumoral effect of orexin/OXR system in colon, pancreas, prostate and other cancers, and its interest as a possible therapeutic target.

Certain serine proteases are considered to be signaling molecules that act through protease-activated receptors (PARs). Our recent studies have implicated PAR1 and PAR4 (thrombin receptors) and PAR2 (trypsin receptor) in human colon cancer growth. Here we analyzed the expression of KLK4, a member of the kallikrein-related peptidase (KLK) family of serine proteases and explored whether this member can activate PAR1 and PAR2 in human colon cancer cells. Immunohistochemistry showed KLK4 expression in human colon adenocarcinomas and its absence in normal epithelia. KLK4 (1 μmol/L) initiated loss of PAR1 and PAR2 from the HT29 cell surface as well as increased intracellular calcium transients in HT29 cells. This KLK4-induced Ca2+ flux was abrogated after an initial challenge of the cells with TRAP (SFLLR-NH2; 100 μmol/L), which is known to desensitize PAR1 and PAR2. Interestingly, PAR1 blocking antibody, which inhibits cleavage and activation by thrombin, dramatically reduced KLK4-induced Ca2+ influx, but blocking cleavage of PAR2 failed to attenuate the KLK4-induced Ca2+ flux. Consistently, desensitization with AP1 (TFFLR-NH2), targeting PAR1, attenuated most of the Ca2+ flux induced by KLK4. KLK4 also induced a rapid and significant ERK1/2 phosphorylation in HT29 cells. Our results demonstrate, for the first time, that KLK4 is aberrantly expressed in colon cancer and capable of inducing PAR1 signaling in cancer cells. These data suggest that KLK4 signaling via PAR1 may represent a novel pathway in colon tumorigenesis.

Serine proteases are now considered as crucial contributors to the development of human colon cancer. We have shown recently that thrombin is a potent growth factor for colon cancer cells through activation of the aberrantly expressed protease-activated receptor 1 (PAR1). Here, we analyzed the signaling pathways downstream of PAR1 activation, which lead to colon cancer cell proliferation in HT-29 cells. Our data are consistent with the following cascade of events on activation of PAR1 by thrombin or specific activating peptide: (a) a matrix metalloproteinase–dependent release of transforming growth factor-α (TGF-α) as shown with TGF-α blocking antibodies and measurement of TGF-α in culture medium; (b) TGF-α-mediated activation of epidermal growth factor receptor (EGFR) and subsequent EGFR phosphorylation; and (c) activation of extracellular signal-regulated protein kinase 1/2 (ERK1/2) and subsequent cell proliferation. The links between these events are shown by the fact that stimulation of cell proliferation and ERK1/2 on activation of PAR1 is reversed by the MMP inhibitor batimastat, TGF-α neutralizing antibodies, EGFR ligand binding domain blocking antibodies, and the EGFR tyrosine kinase inhibitors AG1478 and PD168393. Therefore, transactivation of EGFR seems to be a major mechanism whereby activation of PAR1 results in colon cancer cell growth. Finally, PAR1 activation induces Src phosphorylation, which is reversed by using the Src tyrosine kinase inhibitor PP2, suggesting that Src activation plays a permissive role for PAR1-mediated ERK1/2 activation and cell proliferation probably acting downstream of the EGFR. These data explain how thrombin exerts robust trophic action on colon cancer cells and underline the critical role of EGFR transactivation.

Several lines of evidence suggest that tumor-derived trypsin contributes to the growth and invasion of cancer cells. We have recently shown that trypsin is a potent growth factor for colon cancer cells through activation of the G protein-coupled receptor protease-activated receptor 2 (PAR2). Here, we analyzed the signaling pathways downstream of PAR2 activation that lead to colon cancer cell proliferation in HT-29 cells. Our data are consistent with the following cascade of events upon activation of PAR2 by the serine protease trypsin or the specific PAR2-activating peptide (AP2): (i) a matrix metalloproteinase-dependent release of transforming growth factor (TGF)-alpha, as demonstrated with TGF-alpha-blocking antibodies and measurement of TGF-alpha in culture medium; (ii) TGF-alpha-mediated activation of epidermal growth factor receptor (EGF-R) and subsequent EGF-R phosphorylation; and (iii) activation of ERK1/2 and subsequent cell proliferation. The links between these events are demonstrated by the fact that stimulation of cell proliferation and ERK1/2 upon activation of PAR2 is reversed by the metalloproteinase inhibitor batimastat, TGF-alpha-neutralizing antibodies, EGF-R ligand binding domain-blocking antibodies, and the EGF-R tyrosine kinase inhibitors AG1478 and PD168393. Therefore, transactivation of EGF-R appears to be a major mechanism whereby activation of PAR2 results in colon cancer cell growth. By using the Src tyrosine kinase inhibitor PP2, we further showed that Src plays a permissive role for PAR2-mediated ERK1/2 activation and cell proliferation, probably acting downstream of the EGF-R. These data explain how trypsin exerts robust trophic action on colon cancer cells and underline the critical role of EGF-R transactivation.

Orexin-A (OxA) and orexin-B (OxB) are hypothalamic peptides involved in the sleep/wake control which interact with two class A GPCR, OX1R and OX2R. We have demonstrated that OX1R was highly expressed in digestive cancers including cancer of colon1, pancreas2 and liver. In these cancers, orexin-A induces a mitochondrial apoptosis and a strong inhibition of tumor growth in nude mice xenografted with digestive cancer cell lines1,2. In the present work, we have compared and combined the effect of OxA and NAB-paclitaxel which represents the “gold standard” reference in the chemotherapeutic treatment of pancreas cancer, on their anti-tumoral properties. The incubation of AsPC-1 pancreatic cancer cell line which expressed OX1R, with 0.1μM OxA or 0.1 μM NAB-paclitaxel reveals a cell growth inhibition of 36% and 51%, respectively. The addition of 0.1 μM OxA and 0.1μM NAB-paclitaxel on AsPC-1 cells reveals a significantly cell growth inhibition of 70% suggesting that the double treatment was more efficient than individual treatment. Moreover, the addition of 0.1μM OxA and 0.1 μM NAB-paclitaxel induces 25% of cell apoptosis determined by annexin-V labeling, as compared to single treatment with 0.1μM OxA (18%) or 0.1 μM NAB-paclitaxel (12%). Additionally, we explore the sequential treatment by OxA and NAB-paclitaxel on cell growth of AsPC-1 cells. Our results evidenced than 48h treatment by OxA followed by 48h treatment of NAB-paclitaxel induced an inhibition of 35% of cell growth. In contrast, the reverse treatment (48H NAB-paclitaxel followed by 48h OxA) induces an inhibition of cell growth of 60%. OxA intraperitoneal injection (2 injections/week of 1.12 μmoles/kg OxA and/or NAB-paclitaxel) in nude mice xenografted with AsPC-1 cells, shows that OxA and NAB-paclitaxel induces an inhibition of tumoral volume of 60% and 62%, respectively. Moreover, injection of OxA plus NAB-paclitaxel induces an inhibition of tumoral volume of 70%. Sequential treatments of xenografted tumors in mice with OxA and NAB-paclitaxel was investigated and revealed 72% tumor growth inhibition when mice were treated 30 days with OxA followed by 30 days with NAB-paclitaxel and 83% tumor growth inhibition when they were treated 30 days with NAB-paclitaxel followed by 30 days with OxA. These results indicate that: 1) the addition of OxA and NAB-paclitaxel improves the effect of individual treatment; 2) the sequential treatment consisting of first OxA treatment followed by NAB-paclitaxel treatment was more efficient than reverse treatment. In conclusion, OxA was close to NAB-paclitaxel treatment in term of response and suggest that combined treatment OxA/ NAB-paclitaxel represents a new promising pancreas cancer therapy 1Voisin et al., Cancer research 2011, 71:3341-51 2Speisky et al., AACR annual meeting, 2014, San Diego, USA Citation Format: Thierry Voisin, Dina Plaut, Stephanie Dayot, Maxime Bergere, Valerie Gratio, Pascal Nicole, Anne Couvelard, Alain Couvineau. Combination treatment of orexin-A and NAB-paclitaxel in pancreas cancer: in vitro and in vivo studies. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4581.

We hypothesized that kallikrein-related peptidase 14 (KLK14) is produced by colonic tumors and can promote tumorigenesis by activating proteinase-activated receptors (PARs). We found that KLK14 is expressed in human colon adenocarcinoma cells but not in adjacent cancer-free tissue; KLK14 mRNA, present in colon cancer, leads to KLK14 protein expression and secretion; and KLK14 signals viaPAR-2 in HT-29 cells to cause (1) receptor activation/internalization, (2) increases in intracellular calcium, (3) stimulation of ERK1/2/MAP kinase phosphorylation, and (4) cell proliferation. We suggest that KLK14, acting via PAR-2, represents an autocrine/paracrine regulator of colon tumorigenesis.

Serine proteinases participate in tumor growth and invasion by cleaving and activating proteinase-activated receptors (PARs). Recent studies have implicated PAR-1 and PAR-4 (activated by thrombin) and PAR-2 (activated by trypsin but not by thrombin) in human colon cancer growth. The endogenous activators of PARs in colon tumors, however, are still unknown. We hypothesize that the kallikrein-related peptidase (KLK) family member KLK14, a known tumor biomarker, is produced by colonic tumors and signals to human colon cancer cells by activating PARs. We found that i) KLK14 mRNA was present in 16 human colon cancer cell lines, ii) KLK14 protein was expressed and secreted in colon cancer cell lines, and iii) KLK14 (0.1 μmol/L) induced increases in intracellular calcium in HT29, a human colon cancer–derived cell line. KLK14-induced calcium flux was associated with internalization of KLK14-mediated activation of PAR-2. Furthermore, KLK14 induced significant extracellular signal–regulated kinases 1 and 2 (ERK1/2) phosphorylation and HT29 cell proliferation, presumably by activating PAR-2. A PAR-2 cleavage and activation–blocking antibody dramatically reduced KLK14-induced ERK1/2 signaling. Finally, ectopic expression of KLK14 in human colon adenocarcinomas and its absence in normal epithelia was demonstrated by IHC analysis. These results demonstrate, for the first time, the aberrant expression of KLK14 in colon cancer and its involvement in PAR-2 receptor signaling. Thus, KLK14 and its receptor, PAR-2, may represent therapeutic targets for colon tumorigenesis.

Orexins acting at the G protein-coupled receptor (GPCR) OX1R have recently been shown to promote dramatic apoptosis in cancer cells. We report here that orexin-induced apoptosis is driven by an immunoreceptor tyrosine-based inhibitory motif (ITIM) (IIY(358)NFL) present in the OX1R. This effect is mediated by SHP-2 phosphatase recruitment via a mechanism that requires Gq protein but is independent of phospholipase C activation. This is based on the following observations: 1) mutation of Y(358) into F abolished orexin-induced tyrosine phosphorylation in ITIM, orexin-induced apoptosis, and uncoupled OX1R from Gq protein in transfected Chinese hamster ovary (CHO) cells; 2) orexin-induced apoptosis in CHO cells expressing recombinant OX1R and in colon cancer cells expressing the native receptor was abolished by treatment with the tyrosine phosphatase inhibitor PAO and by transfection with a dominant-negative mutant of SHP-2; 3) orexins were unable to promote apoptosis in fibroblast cells invalidated for the G alpha q subunit and transfected with OX1R cDNA, whereas they promoted apoptosis in cells equipped with G alpha q and OX1R; and 4) the phospholipase C inhibitor U-73122 blocked orexin-stimulated inositol phosphate formation, whereas it had no effect on orexin-induced apoptosis in CHO cells expressing OX1R. These data unravel a novel mechanism, whereby ITIM-expressing GPCRs may trigger apoptosis.

Several lines of evidence suggest that tumor-derived trypsin contributes to the growth and invasion of cancer cells. We have recently shown that trypsin is a potent growth factor for colon cancer cells through activation of the G protein-coupled receptor protease-activated receptor 2 (PAR2). Here, we analyzed the signaling pathways downstream of PAR2 activation that lead to colon cancer cell proliferation in HT-29 cells. Our data are consistent with the following cascade of events upon activation of PAR2 by the serine protease trypsin or the specific PAR2-activating peptide (AP2): (i) a matrix metalloproteinase-dependent release of transforming growth factor (TGF)-alpha, as demonstrated with TGF-alpha-blocking antibodies and measurement of TGF-alpha in culture medium; (ii) TGF-alpha-mediated activation of epidermal growth factor receptor (EGF-R) and subsequent EGF-R phosphorylation; and (iii) activation of ERK1/2 and subsequent cell proliferation. The links between these events are demonstrated by the fact that stimulation of cell proliferation and ERK1/2 upon activation of PAR2 is reversed by the metalloproteinase inhibitor batimastat, TGF-alpha-neutralizing antibodies, EGF-R ligand binding domain-blocking antibodies, and the EGF-R tyrosine kinase inhibitors AG1478 and PD168393. Therefore, transactivation of EGF-R appears to be a major mechanism whereby activation of PAR2 results in colon cancer cell growth. By using the Src tyrosine kinase inhibitor PP2, we further showed that Src plays a permissive role for PAR2-mediated ERK1/2 activation and cell proliferation, probably acting downstream of the EGF-R. These data explain how trypsin exerts robust trophic action on colon cancer cells and underline the critical role of EGF-R transactivation.

The traditional view on the role of serine proteases in tumor biology has changed with the recent discovery of a family of protease-activated receptors (PARs). In this study we explored the expression and functional role of the thrombin receptor PAR-1 in human colon cancer cells. Reverse transcriptase-polymerase chain reaction analysis showed that PAR-1 mRNAs are present in 11 of 14 human colon cancer cell lines tested but not in normal human colonic epithelial cells. This is in line with the immunolocalization of PAR-1 in human colon tumors and its absence in normal human colonic mucosa. The functional significance of the aberrant expression of PAR-1 in colon cancer cells was then investigated. We found that 1) a prompt increase in intracellular calcium concentration was observed on thrombin (10 nmol/L) or PAR-1 agonist AP1 (100 micro mol/L) challenge of HT29 cells; 2) HT29 quiescent cells treated with thrombin (0.01 to 20 nmol/L) or AP1 (1 to 300 micro mol/L) exhibited dramatic mitogenic responses (3.5-fold increase in cell number). Proliferative effects of thrombin or AP1 were also observed in other colon cancer cell lines expressing PAR-1. This effect was reversed by the MEK inhibitor PD98059 in consonance with the ability of thrombin or AP1 to induce phosphorylation of p42/p44 extracellular-regulated protein kinases. 3) PAR-1 activation by thrombin or AP1 led to a two-fold increase in cell motility of wounded HT29-D4. Our results demonstrate for the first time the aberrant expression of the functional thrombin receptor PAR-1 in colon cancers and its important involvement in cell proliferation and motility. Thrombin should now be considered as a growth factor for human colon cancer.

The purpose of this study was to determine the angiogenic profile of human oesophageal adenocarcinoma. This study was carried out on a large series of surgically resected Barrett's adenocarcinomas and associated preneoplastic lesions. Vascularization was quantified by microvessel counting and measurement of the percentage microvessel surface area after immunohistochemistry using the CD34 antibody. The expression of vascular endothelial cell growth factor (VEGF) was also examined by immunohistochemistry. Results were correlated with clinico-pathological data and prognosis. Vascularization, assessed by both microvessel counting and measurement of the microvessel surface, was statistically higher in superficial cancers than in others. Higher vascularization was correlated with a lower rate of lymph node and distant metastasis, as well as with better survival. However, when superficial carcinomas were excluded from the study, microvessel count failed to provide any significant prognostic information. Irrespective of the inclusion or exclusion of superficial tumours, the expression of VEGF was correlated with a higher vascularisation but did not provide prognostic significance. It is concluded that high angiogenic properties are acquired in precancerous lesions and early cancers in Barrett's oesophagus. Vascularization as assessed by both microvessel counting and measurement of the microvessel surface is not informative for prognosis in infiltrative Barrett's adenocarcinomas. The expression of VEGF is correlated with vascularization, but has no independent prognostic relevance.

Serine proteinases signal through proteinase-activated receptors (PARs). Our studies have implicated PAR1 and PAR4 (thrombin receptors) and PAR2 (trypsin receptor) in human colon cancer growth. However, endogenous activators of PARs in colon tumors are still unknown. Recently, members of the kallikrein-related peptidase (KLK) family have been shown to activate PARs in many cell systems. Thus, our aim was to determine if KLK14, a KLK family member, is expressed in colonic tumors and to see if this KLK can activate PARs in human colon cancer cells. The presence of KLK14 in colon cancer cell lines was assessed by RT-PCR, ELISA and immunofluorescence, and its expression in human colonic tissue was assessed by immunohistochemistry. The effects of recombinant KLK14 in parallel with PAR1/2 agonists (SFLLRN-NH2, an activating peptide for both PAR1 and PAR2; TFLLR-NH2, a selective activating peptide for PAR1 and the selective PAR2 agonists, 2-furoyl-LIGRLO-NH2; SLIGRL-NH2) were assessed for calcium flux, receptor internalization and ERK1/2 phosphorylation in a human colon cancer-derived HT29 cell line that expresses PAR1 and PAR2. We found that: a) KLK14 mRNA (RT-PCR) was present in 16 out of 16 human colon cancer cell lines, b) KLK14 protein is present (ELISA) in HT29 conditioned media and other colon cancer cell lines; c) there was strong staining of KLK14 in the cytoplasmic compartment of HT29 cells and of human colonic tumors (immunofluorescence and immunohistochemistry; paraffin sections) d) KLK14 (0.1 µM) caused prompt increases in intracellular calcium ([Ca2+]i) in HT29 cells (Microspectrofluorimetry with Fura 2/fluo-3). The KLK14-induced Ca2+-flux was abrogated after an initial challenge of the cells with SFLLRN-NH2 (100 µM), which desensitizes PAR1 and PAR2 simultaneously. Desensitization with 2-furoyl-LIGRLO-NH2 (10 µM) a potent PAR2 agonist, attenuated most of the Ca2+ flux induced by KLK14, whereas responses to TFLLR-NH2, the PAR1 agonist, were minimally affected. Consistently, a first challenge with thrombin did not affect KLK14-induced Ca2+ flux. These results strongly suggest that KLK14 activates preferentially PAR2 in HT29 cells. e) KLK14 initiates a dramatic loss of cell surface PAR2 (microscopic analysis) due to its internalization and f) KLK14 induces a rapid (within 5-10 min) and significant ERK1/2 phosphorylation in HT29 cells. This KLK14-PAR signaling pathway may represent a novel therapeutic target for colon tumorigenesis. Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4104.