Deficiency of TET2-mediated KMT2D self-transcription confers a targetable vulnerability in hepatocellular carcinoma.

Hepatocellular carcinoma (HCC) has become a leading cause of cancer-related mortality worldwide. Conventional therapies tend to exacerbate comorbidities, liver dysfunction, and relapse, rendering an urgent demand for novel strategy for management of HCC. Here, we reported that DNA dioxygenase TET2 collaborates with histone methyltransferase KMT2D to enable transcription of KMT2D and ARID1A in HCC. Mechanistically, KMT2D and ARID1A are the major epigenetic targets of TET2 through RNA-seq analysis. Moreover, KMT2D recruits TET2 to facilitate self-transcription via oxidation of 5-methylcytosine in promoter, thereby maintaining expression of ARID1A. Physiologically, KMT2D was identified as a tumor suppressor and mediates the antitumor effect of vitamin C in HCC. Tumors with depleted KMT2D present growth advantage over control group. Vitamin C is able to impair tumor growth, which is compromised by deficiency of KMT2D. Furthermore, loss of KMT2D sensitizes HCC tumors to cisplatin with reduced tumor weight and high level of DNA damage. Ultimately, TET2-KMT2D axis correlates with prognosis of patients with HCC. Patients with high amounts of TET2 and KMT2D present better outcome. Our findings not only put forth a heretofore unrecognized mechanism underlying cross-talk between TET2 and KMT2D in mediating self-transcription of KMT2D, but also propose a targetable vulnerability for HCC therapy on the basis of TET2-KMT2D axis.