Notch signalling pathway in development of cholangiocarcinoma

Table 1 List of main representatives of Notch Signalling pathway and their current findings in development of cholangiocarcinoma

Receptors, ligands and downstream signaling molecules	Type of model	Findings	Ref.
Notch 1	Mice model	Overexpression of NICD1 in mice liver leads to the formation of cystoadenomas and cystoadenocarcinomas. IH-CCA cell migration is enhanced by overexpression of Notch 1. It further enhances the growth of IH-CCA as result of Rac1 activation. The atypical expression by the up-regulation of Vimentin and α-SMA at the expense of E-cadherin expression leads to an EMT	[32,63]
	Human cell lines	Overexpression of Notch 1 receptor along with JAG-1 has been perceived in four human CCA cell lines (MzChA1, TFK1, SZ1and EgI1)	[61]
Notch 2	Wild-type and Notch2 flox/floxmice model	Notch2 is basically involved in regulating the hepatocyte derived CCA. Wild-type and Notch2 flox/floxmice models have been utilized for studying the Notch Signalling pathway in AKT/Yap-driven IH-CCA development and has been found that AKT/Yap-induced IH-CCA development is hepatocyte dependent and based on the canonical Notch signalling cascade in in vivo models	[14]
	Human cell lines	HCC and ICC cell lines reveals the down-regulation in expression of Sox9 and EpCAM, typical biliary markers after Notch 2 silencing	[14]
Notch 3	Mice model	IH-CCA development and survival has been found to be associated with activation of PI3K-AKT cascade by overexpression of the Notch 3 atypical receptor rather than canonical Notch-RBPJ mechanism. Hepatocarcinogen Thioacetamide induces cancer in CK19CreERTeYFPp53 mouse model owing constitutive Notch3 deletion that establishes the IH-CCA inhibition after loss of single copy of Notch 3 gene	[66,62]
Notch 4	Human samples	The overexpression of Notch 4 is associated with raised serum levels of CA125 that suggests the poor prognosis of IH-CCA	[59]
Jagged-1	Human cell lines	The suppression of the Jagged-1 results in the reduction of growth of the human CCA cell lines (HUCCT1 and KKU-156) with consequent down-regulation of downstream signalling molecules (Hes1 and Hes4)	[16]
RBPJ	Mice model	The down-regulation of RBPJ protein in AKT/JAG-1 mouse model results in total inhibition of Notch signalling pathway following the development of IH-CCA. Notch 1 plays its role in advancement of CCA by enhancing the cell survival and proliferation through the regulation of 14-3-3 theta in RBP-J-associated module. Hence, it concludes that that RBPJ is a significant element in Notch signalling pathway in CCA	[16,70]
Hes-1	Mice model	The tamoxifen-inducible Alb CreERT2; R26R Notch/+ mice expresses mouse NICD1 and delivers the constitutive Notch activity in hepatic cells. In Alb-CreERT2;Hes1fl/fl mice, these hepatocytes that lack the Hes1 gene have revealed that on treatment with TAA, CK10 positive cells significantly increases in lobules of Alb CreERT2; R26RNotch/+ and has been found to be reduced in Alb-CreERT2; Hes1fl/fl mice. Besides that, the rapid nodule formation has been found to be obvious in the livers of Alb CreERT2; R26RNotch/+ in contrast to those of Alb-CreERT2; Hes1fl/fl.. This observation confirms the fact that Hes1 is greatly involved in pathogenicity of IH-CCA. Further, this carcinogenesis can be blocked by inhibition of Hes1	[73,74]

CCA: Cholangiocarcinoma; TCC: Thioacetamide; IH-CCA: Intrahepatic cholangiocarcinoma; NICD: Notch intracellular domain; EMT: Epithelial-mesenchymal transition; RBP-J: Recombination signal Binding Protein for immunoglobulin kappa J; JAG: Jagged.