YAP promotes proliferation, chemoresistance, and angiogenesis in human cholangiocarcinoma through TEAD transcription factors

Abstract

The Yes-associated protein (YAP)/Hippo pathway has been implicated in tissue development, regeneration, and tumorigenesis. However, its role in cholangiocarcinoma (CC) is not established. We show that YAP activation is a common feature in CC patient biopsies and human CC cell lines. Using microarray expression profiling of CC cells with overexpressed or down-regulated YAP, we show that YAP regulates genes involved in proliferation, apoptosis, and angiogenesis. YAP activity promotes CC growth in vitro and in vivo by functionally interacting with TEAD transcription factors (TEADs). YAP activity together with TEADs prevents apoptosis induced by cytotoxic drugs, whereas YAP knockdown sensitizes CC cells to drug-induced apoptosis. We further show that the proangiogenic microfibrillar-associated protein 5 (MFAP5) is a direct transcriptional target of YAP/TEAD in CC cells and that secreted MFAP5 promotes tube formation of human microvascular endothelial cells. High YAP activity in human CC xenografts and clinical samples correlates with increased MFAP5 expression and CD31 1 vasculature. Conclusions: These findings establish YAP as a key regulator of proliferation and antiapoptotic mechanisms in CC and provide first evidence that YAP promotes angiogenesis by regulating the expression of secreted proangiogenic proteins. (HEPATOLOGY 2015;62:1497-1510 C holangiocarcinoma (CC) represents the second most frequent primary liver cancer, with increasing incidence and mortality rates worldwide. The majority of CC is detected at advanced stages, preventing curative surgery and leaving patients with a median survival of only 24 months. Systemic chemotherapy (cisplatin plus gemcitabine) is currently the first-line treatment for CC with limited success.

Pan-mTOR inhibitor MLN0128 is effective against intrahepatic cholangiocarcinoma in mice

“…Equivalent levels of AKT immunoreactivity in ICC and corresponding non-neoplastic livers were detected in the remaining samples. In accordance with previous findings [21,22], nuclear accumulation of Yap was almost ubiquitously detected in ICC (90/94; 95.74%), whereas only faint nuclear and/or cytoplasmic immunoreactivity of Yap was observed in surrounding non-neoplastic counterparts. Noticeably, 63 of 94 (67.02%) ICC displayed simultaneous activation of phosphorylated AKT and Yap, thus suggesting the relevance of the two concomitant oncogenic events along cholangiocarcinogenesis.…”

Molecular Mechanisms Driving Cholangiocarcinoma Invasiveness: An Overview

“…Consistent with immunohistochemical findings 151–153 , CCA cell lines display high levels of nuclear (i.e., transcriptionally active) YAP, whereas in non-malignant biliary epithelial cells, YAP is mainly sequestered in the cytoplasm 154 . Forced overexpression of YAP promoted the migratory and invasive capabilities of CCA cells, in vitro , and enhanced the metastatic dissemination of intraperitoneal CCA xenografts.…”

“…Interestingly, both gankyrin and FGFR (notably, FGFR2) could in turn support YAP expression, consistent with the presence of positive feedback loops involving YAP and its targets 151,154 . Given the ability of CCA cells to rapidly inactivate YAP upon high mechanical stress, as in high-density culture conditions 153 , it is also tempting to speculate that the increased ECM rigidity within the CCA-associated stroma may induce a cytoskeleton-dependent, Hippo-independent YAP/TAZ activation in CCA cells, thus further enhancing their malignant properties.…”

Targeting Developmental Pathways: The Achilles Heel of Cancer?

“…YAP activation/overexpression is commonly seen in human CCA cell lines and biopsies from patients, and is more frequently found in CCA than in hepatocellular carcinoma, although in more than 85% of CCA patients, YAP is mutated [31] . More research is required to identify critical mutations upstream of YAP or indirect YAP regulation by crosstalk with other signalling pathways to provide novel strategies for the therapeutic disruption of the YAP-TEAD axis in CCA.…”

“…Genetic mutation (loss of NF2 function) leads to a constitutive activation of the YAP/TAZ-TEAD cascade, and is found in several cancers including MPM, hepatocellular carcinoma, bile cholangiocarcinoma (CCA), and gastric and ovarian cancers, as well as in other malignancies [26,31] .…”