biostudies-literatureQu MU.S. Department of Veterans Affairs (VA)HHS | NIH | National Institute of Neurological Disorders and Stroke (NINDS)HHS | NIH | National Institute of Neurological Disorders and StrokeHHS | NIH | National Institute on Alcohol Abuse and AlcoholismBLR&amp;amp;D Research Career Scientist Award ApplicationNIAAA NIH HHSUSDA | National Institute of Food and AgricultureUSC Norris Comprehensive Cancer Center Translational Team Accelerator ProgramHHS | NIH | National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)HHS | NIH | National Institute of Diabetes and Digestive and Kidney DiseasesHHS | NIH | National Cancer InstituteNCI NIH HHSUSDA | National Institute of Food and Agriculture (NIFA)HHS | NIH | National Cancer Institute (NCI)U.S. Department of Veterans AffairsBLR&amp;D Research Career Scientist Award Applicatione2214829120https://www.ebi.ac.uk/biostudies/studies/S-EPMC9926257biostudies-literatureUnknown120(2)Hepatocellular carcinoma (HCC) remains a global health challenge whose incidence is growing worldwide. Previous evidence strongly supported the notion that the circadian clock controls physiological homeostasis of the liver and plays a key role in hepatocarcinogenesis. Despite the progress, cellular and molecular mechanisms underpinning this HCC-clock crosstalk remain unknown. Addressing this knowledge gap, we show here that although the human HCC cells Hep3B, HepG2, and Huh7 displayed variations in circadian rhythm profiles, all cells relied on the master circadian clock transcription factors, BMAL1 and CLOCK, for sustained cell growth. Down-regulating Bmal1 or Clock in the HCC cells induced apoptosis and arrested cell cycle at the G2/M phase. Mechanistically, we found that inhibiting Bmal1/Clock induced dysregulation of the cell cycle regulators Wee1 and p21 which cooperatively contribute to tumor cell death. Bmal1/Clock knockdown caused downregulation of Wee1 that led to apoptosis activation and upregulation of p21 which arrested the cell cycle at the G2/M phase. Collectively, our results suggest that the circadian clock regulators BMAL1 and CLOCK promote HCC cell proliferation by controlling Wee1 and p21 levels, thereby preventing apoptosis and cell cycle arrest. Our findings shed light on cellular impact of the clock proteins for maintaining HCC oncogenesis and provide proof-of-principle for developing cancer therapy based on modulation of the circadian clock.Proceedings of the National Academy of Sciences of the United States of AmericaCircadian regulator BMAL1::CLOCK promotes cell proliferation in hepatocellular carcinoma by controlling apoptosis and cell cycle.PMC9926257CA139158P30 CA047904CA197718NA5 IK6BX0042055 I01BX001991DK124627CA2386622019-67022-29930U01 AA027681NS103434P50 AA011999Zhang GKay SALenz HJHuang WRich JNQu MVu AWu RQu HTsukamoto HJia ZfalseCircadian regulator BMAL1::CLOCK promotes cell proliferation in hepatocellular carcinoma by controlling apoptosis and cell cycle.Hepatocellular carcinoma (HCC) remains a global health challenge whose incidence is growing worldwide. Previous evidence strongly supported the notion that the circadian clock controls physiological homeostasis of the liver and plays a key role in hepatocarcinogenesis. Despite the progress, cellular and molecular mechanisms underpinning this HCC-clock crosstalk remain unknown. Addressing this knowledge gap, we show here that although the human HCC cells Hep3B, HepG2, and Huh7 displayed variations in circadian rhythm profiles, all cells relied on the master circadian clock transcription factors, BMAL1 and CLOCK, for sustained cell growth. Down-regulating Bmal1 or Clock in the HCC cells induced apoptosis and arrested cell cycle at the G2/M phase. Mechanistically, we found that inhibiting Bmal1/Clock induced dysregulation of the cell cycle regulators Wee1 and p21 which cooperatively contribute to tumor cell death. Bmal1/Clock knockdown caused downregulation of Wee1 that led to apoptosis activation and upregulation of p21 which arrested the cell cycle at the G2/M phase. Collectively, our results suggest that the circadian clock regulators BMAL1 and CLOCK promote HCC cell proliferation by controlling Wee1 and p21 levels, thereby preventing apoptosis and cell cycle arrest. Our findings shed light on cellular impact of the clock proteins for maintaining HCC oncogenesis and provide proof-of-principle for developing cancer therapy based on modulation of the circadian clock.2023-01-01T00:00:00Z2023 Jan2025-04-22T19:55:58.461Z2025-04-06T02:58:07.57ZS-EPMC99262573659567110.1073/pnas.2214829120