Cholangiocarcinoma is a devastating cancer of biliary origin with limited treatment options. Symptoms are usually evident after blockage of the bile duct by the tumor, and at this late stage, they are relatively resistant to chemotherapy and radiation therapy. Therefore, it is imperative that alternative treatment options are explored. We present novel data indicating that the metabolism of serotonin is dysregulated in cholangiocarcinoma cell lines, compared with normal cholangiocytes, and tissue and bile from cholangiocarcinoma patients. Specifically, there was an increased expression of tryptophan hydroxylase 1 and a suppression of monoamine oxidase A expression (enzymes responsible for the synthesis and degradation of serotonin, respectively) in cholangiocarcinoma. This resulted in an increased secretion of serotonin from cholangiocarcinoma and increased serotonin in the bile from cholangiocarcinoma patients. Increased local serotonin release may have implications on cholangiocarcinoma cell growth. Serotonin administration increased cholangiocarcinoma cell growth in vitro, whereas inhibition of serotonin synthesis decreases tumor cell growth both in vitro and in vivo. The data presented here represent the first evidence that serotonin metabolism is dysregulated in cholangiocarcinoma and that modulation of serotonin synthesis may represent an alternative target for the development of therapeutic strategies. [Cancer Res 2008;68(22):9184-93]

Cholangiocarcinomas are cancers that have poor prognosis and limited treatment options. The noncanonical Wnt pathway is mediated predominantly by Wnt 5a, which activates a Ca(2+)-dependent pathway involving protein kinase C, or a Ca(2+)-independent pathway involving the orphan receptor Ror2 and subsequent activation of Jun NH(2)-terminal kinase (JNK). This pathway is associated with growth-suppressing effects in numerous cell types. We have shown that anandamide decreases cholangiocarcinoma growth in vitro. Therefore, we determined the effects of anandamide on cholangiocarcinoma tumor growth in vivo using a xenograft model and evaluated the effects of anandamide on the noncanonical Wnt signaling pathways. Chronic administration of anandamide decreased tumor growth and was associated with increased Wnt 5a expression in vitro and in vivo. Treatment of cholangiocarcinoma cells with recombinant Wnt 5a decreased cell proliferation in vitro. Neither anandamide nor Wnt 5a affected intracellular calcium release, but both increased the JNK phosphorylation. Stable knockdown of Wnt 5a or Ror2 expression in cholangiocarcinoma cells abolished the effects of anandamide on cell proliferation and JNK activation. Modulation of the endocannabinoid system may be important in cholangiocarcinoma treatment. The antiproliferative actions of the noncanonical Wnt signaling pathway warrants further investigation to dissect the mechanism by which this may occur.

Cholangiocarcinoma is a devastating cancer of biliary origin with limited treatment options. Symptoms are usually evident after blockage of the bile duct by the tumor, and at this late stage, they are relatively resistant to chemotherapy and radiation therapy. Therefore, it is imperative that alternative treatment options are explored. We have previously shown that serotonin metabolism is dysregulated in cholangiocarcinoma leading to an increased secretion of serotonin, which has growth-promoting effects. Because serotonin and dopamine share the degradation machinery, we evaluated the secretion of dopamine from cholangiocarcinoma and its effects on cell proliferation. Using 4 cholangiocarcinoma cell lines and human biopsy samples, we demonstrated that there was an increase in mRNA and protein expression of the dopamine synthesis enzymes tyrosine hydroxylase and dopa decarboxylase in cholangiocarcinoma. There was increased dopamine secretion from cholangiocarcinoma cell lines compared to H69 and HIBEC cholangiocytes and increased dopamine immunoreactivity in human biopsy samples. Furthermore, administration of dopamine to all cholangiocarcinoma cell lines studied increased proliferation by up to 30%, which could be blocked by the pretreatment of the D2 and D4 dopamine receptor antagonists, whereas blocking dopamine production by a-methyldopa administration suppressed growth by up to 25%. Administration of a-methyldopa to nude mice also suppressed cholangiocarcinoma tumor growth. The data presented here represent the first evidence that dopamine metabolism is dysregulated in cholangiocarcinoma and that modulation of dopamine synthesis may represent an alternative target for the development of therapeutic strategies.Cholangiocarcinoma arises from the neoplastic transformation of the epithelial cells or cholangiocytes that line the bile ducts. It accounts for about 3% of all gastrointestinal cancers and represent the second most common primary liver tumor after hepatocellular carcinoma.1 Biliary tumors are extremely aggressive and display a poor prognosis.1-4 The lack of therapeutic tools for such a devastating disease is due, at least in part, to the lack of knowledge regarding the mechanisms regulating cholangiocarcinoma growth. 2-4 However, increasing evidence has shown that neuropeptides and neuroendocrine hormones are amongst those factors that are able to affect cholangiocarcinoma biology, either promoting or inhibiting its growth. 1,[4][5][6][7] We recently demonstrated that cholangiocarcinoma overproduces and secretes serotonin, which has growth-promoting effects in an autocrine manner. 6 Specifically,

The endocannabinoids anandamide (AEA) and 2-arachidonylglycerol (2-AG) have opposing effects on cholangiocarcinoma growth. Implicated in cancer, Notch signaling requires the γ-secretase complex for activation. The aims of this study were to determine if the opposing effects of endocannabinoids depend on the differential activation of the Notch receptors; and to demonstrate that the differential activation of these receptors are due to presenilin 1 containing- and presenilin 2-containing- γ-secretase complexes. Mz-ChA-1 cells were treated with AEA or 2-AG. Notch receptor expression, activation and nuclear translocation was determined. Specific roles for Notch 1 and 2 on cannabinoid-induced effects were determined by transient transfection of Notch 1 or 2 shRNA vectors prior to stimulation with AEA or 2-AG. Expression of presenilin 1 and 2 was determined after AEA or 2-AG treatment and the involvement of presenilin 1 and 2 in the cannabinoid induced effects were demonstrated in cell lines with low presenilin 1 or 2 expression. Antiproliferative effects of AEA required increased Notch 1 mRNA, activation and nuclear translocation, whereas the growth-promoting effects induced by 2-AG required increased Notch 2 mRNA expression, activation and nuclear translocation. AEA increased presenilin 1 expression and recruitment into the γ-secretase complex whereas 2-AG increased expression and recruitment of presenilin 2. The development of novel therapeutic strategies aimed at modulating the endocannabinoid system, or mimicking the mode of action of AEA on Notch signaling pathways would prove beneficial for cholangiocarcinoma management.