The clear cell variant of renal cell carcinoma (ccRCC) is the most common renal epithelial malignancy and responsible for most of the deaths from kidney cancer. Patients carrying inactivating mutations in the Von Hippel-Lindau (VHL) gene have an increased proclivity to develop several types of tumors including ccRCC. Normally, the Hypoxia Inducible Factor alpha (HIF-α) subunits of the HIF heterodimeric transcription factor complex are regulated by oxygen-dependent prolyl-hydroxylation, VHL-mediated ubiquitination and proteasomal degradation. Loss of pVHL function results in elevated levels of HIF-α due to increased stability, leading to RCC progression. While HIF-1α acts as a tumor suppressor, HIF-2α promotes oncogenic potential by driving tumor progression and metastasis through activation of hypoxia-sensitive signaling pathways and overexpression of HIF-2α target genes. One strategy to suppress ccRCC aggressiveness is directed at inhibition of HIF-2α and the associated molecular pathways leading to cell proliferation, angiogenesis, and metastasis. Indeed, clinical and pre-clinical data demonstrated the effectiveness of HIF-2α targeted therapy in attenuating ccRCC progression. This review focuses on the signaling pathways and the involved genes (cyclin D, c-Myc, VEGF-a, EGFR, TGF-α, GLUT-1) that confer oncogenic potential downstream of the VHL-HIF-2α signaling axis in ccRCC. Discussed as well are current treatment options (including receptor tyrosine kinase inhibitors such as sunitinib), the medical challenges (high prevalence of metastasis at the time of diagnosis, refractory nature of advanced disease to current treatment options), scientific challenges and future directions.

Maladaptive tubular repair is a major contributor to fibrosis and chronic kidney disease (CKD), yet the molecular regulators of this process remain poorly understood. We report that the E3 ubiquitin ligases WWP1 and TRIM65 are novel regulators of tubular fibrosis. Both ligases were markedly induced in human and experimental CKD. WWP1 induction correlates with declining renal function in humans, highlighting the potential clinical relevance of WWP1. Profibrotic factor PAI-1 promotes a robust induction of WWP1 and TRIM65 in both primary human renal epithelial cells as well as cell line (HK-2). The silencing of WWP1 or TRIM65 significantly attenuated PAI-1-induced fibrotic signaling. Mechanistically, PAI-1 triggers a signaling cascade in which suppression of the regenerative BMP-7/SMAD5 pathway permits c-Myc induction, resulting in WWP1 and TRIM65 upregulation. The elevated expression of these ligases subsequently promotes epithelial dedifferentiation and fibrotic growth arrest. Restoration of BMP-7 or SMAD5 signaling disrupted this cascade and reduced fibrosis in renal tubular cells. Our study establishes a previously unrecognized PAI-1–c-Myc–WWP1/TRIM65 axis governing tubular maladaptive repair and positions WWP1 as a potentially new therapeutic target for slowing CKD progression.