BMAL1-HIF2α heterodimers contribute to ccRCC

Abstract

Circadian disruption enhances cancer risk, and many tumors exhibit disordered circadian gene expression. We show rhythmic gene expression is unexpectedly robust in clear cell renal cell carcinoma (ccRCC). Furthermore, the clock gene BMAL1 is higher in ccRCC than in healthy kidneys, unlike in other tumor types. BMAL1 is closely related to ARNT, and we show that BMAL1-HIF2 regulates a subset of HIF2 target genes in ccRCC cells. Depletion of BMAL1 reprograms HIF2 chromatin association and target gene expression and reduces ccRCC growth in culture and in xenografts. Analysis of pre-existing data reveals higher BMAL1 in patient-derived xenografts that are sensitive to growth suppression by a HIF2 antagonist (PT2399). We show that BMAL1-HIF2 is more sensitive than ARNT-HIF2 to suppression by PT2399, and increasing BMAL1 sensitizes 786O cells to growth inhibition by PT2399. Together, these findings indicate that an alternate HIF2 heterodimer containing the circadian partner BMAL1 contributes to HIF2 activity, growth, and sensitivity to HIF2 antagonist drugs in ccRCC cells.