New Von Hippel Lindau (VHL) tumor suppressor signaling in renal cancer

Project Summary Clear cell renal cell carcinoma (ccRCC), which accounts for approximately 85% of all renal cancers, is resistant to a variety of cancer therapies and is highly lethal. von Hippel-Lindau (VHL) is the most important tumor suppressor in renal cancer, its loss leads to hypoxia inducible factor  (HIF, including HIF1α and HIF2α)

accumulation. Although HIF2α inhibitor has been developed as a potential therapeutic target in renal cancer, only a small propotion of patients will respond to HIF2α inhibitore treatment, suggesting the importance of identifying additional therapeutic vulnerabilities in VHL-deficient kidney cancer. Methylation of adenosine (m6A)

determines the fate of modified messenger RNAs (mRNAs) and has recently been shown to play a key role regulating gen expression critical in cancer development. Although previous research has suggested that m6A may be important in renal cancer, the molecular mechanism behind its role in ccRCC tumorigenesis and

aggression is not yet well understood. Our preliminary data suggest that VHL binds to m6A enzymatic complex proteins Mettl3/14 and regulates their interaction. By performing m6A RIP-Seq and RNA-Seq in renal cells with and without VHL, we have identified a set of genes whose expression may be regulated by m6A in a VHL-

dependent manner. Among them, Phosphoinositide-3-Kinase Regulatory Subunit 3 (PIK3R3), an important component of PI3K pathway, its mRNA stability is regulated by VHL in an m6A-dependent manner. Functionally, PIK3R3 depletion promotes renal cell growth and tumor growth while its overexpression diminishes ccRCC cell

growth on 2-D colony formation, 3-D soft agar growth and tumor growth. We hypothesize that VHL regulates m6A-dependent gene expression, thereby controlling ccRCC tumorigenesis. This is the first study to link VHL with mRNA stability regulation via regulating the Mettl3/14 m6A enzymatic complex, which characterizes

the noncanonical function of VHL distinctive from its role as an E3 ubiquitin ligase. In Specific Aim 1, we will determine the molecular mechanism by which VHL regulates m6A modification in kidney cancer. In Specific Aim 2, we will examine the functional role of VHL-m6A signaling in ccRCC tumorigenesis. Specifically, we will

examine the therapeutic efficacy or PI3K and AKT inhibitors in kidney cancer xenografts and patient derived xenografts. Successful completion of these aims will provide mechanistic insight into a novel signaling pathway on how VHL regulates gene expression important in ccRCC and set the foundation for therapeutic intervention

targeting the VHL-Mettl3/14-m6A signaling axis in ccRCC.