TFAM depletion overcomes hepatocellular carcinoma resistance to doxorubicin and sorafenib through AMPK activation and mitochondrial dysfunction

Mitochondrial transcription factor A (TFAM), which is required for mitochondrial DNA (mtDNA) transcription, has been linked to metabolic changes that contribute to tumorigenesis and chemoresistance. In this work, we investigated the expression pattern and role of TFAM in hepatocellular carcinoma (HCC). TFAM expression level is similar in 18 out of 20 paired normal liver and HCC tissues with only 2 HCC tissues showing 1.8-fold increase in TFAM. Similar phenomenon was observed in HCC cell lines compared to normal liver lines. Interestingly, TFAM expression is upregulated in resistant HCC cells regardless of the differential TFAM expression level in their parental lines and mechanism of resistance. TFAM depletion led to inhibition of growth and survival but not migration, and sensitization to doxorubicin and sorafenib treatment, through AMPK activation, reduction of nucleoside triphosphates and mitochondrial respiration in HCC cells. In addition, we demonstrated that resistant HCC cell lines were more sensitive to TFAM inhibition than parental lines, and this might be due to the increased mitochondrial biogenesis in resistant HCC cell lines. Our work reveals the preferential role of TFAM in HCC cell response to standard of care drugs, which suggests a potential sensitizing therapeutic target for HCC treatment.