Introduction: The contact inhibition of proliferation is crucial for well-controlled organogenesis. Its disruption results in sustained cell proliferation, which is a hallmark of solid tumors. The Hippo signaling pathway has been implicated in contact inhibition of proliferation. Here, we investigated the role of TAZ (WWTR1), a key transcription co-activator of hippo-pathway, in HCC progression. Methods and Results: In HCC patients, the high TAZmRNA expression examined by real time PCR showed worsen survival outcomes compared with low expression group. Additionally, the tumor size in High TAZmRNA expression group was significantly larger than that in low expression group, and its high protein expression in HCC was deeply associated with the cell proliferative activity. A knockdown of TAZ expression in HCC cell lines attenuated the cell growth accompanying the downstream gene expressions (CTGF and CYR61). As the TAZ-mediated signaling pathway in cell growth, a knockdown of TAZ expression using RNAi inactivated the PI3K/Akt/mTOR pathway. Conclusion: Thus, TAZ plays a crucial role in tumor progression by accelerating cell growth via a PI3K/Akt/mTOR pathway, and tumoral TAZmRNA expression level may be a useful prognostic biomarker in HCC.

Citation Format: Hiromitsu Hayashi, Hideyuki Kuroki, Shigeki Nakagawa, Takaaki Higashi, Keita Sakamoto, Naomi Yokoyama, Takatoshi Ishiko, Toru Beppu, Hideo Baba. TAZ (WWTR1), a key transcription co-activator of hippo-pathway, promotes hepatocellular carcinoma progression via PI3K/Akt/mTOR pathway. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3520. doi:10.1158/1538-7445.AM2014-3520