Combined Analyses of the VHL and Hypoxia Signaling Axes in an Isogenic Pairing of Renal Clear Cell Carcinoma Cells.

The loss of function of the Von Hippel-Lindau (VHL) tumor suppressor leads to the development of hypervascular tumors, exemplified by clear-cell-type renal cell carcinoma (RCC). VHL governs the adaptive responses to fluctuation of oxygen levels largely through the regulated suppression of hypoxia inducible factors (HIFs). Here, we combine proteome and phospho-proteomic analysis of isogenic 786-O RCC (±VHL) cells to compare signatures that reflect hypoxia and/or loss of VHL. VHL-independent hypoxic responses, notably include up-regulation of phosphorylation at Ser232 on the pyruvate dehydrogenase α subunit that is known to promote glycolysis. Hypoxic responses governed by VHL include up-regulation of known biomarkers of RCC (e.g., GLUT1, NDRG1) and the signaling adaptor molecule IRS-2. Notably, we also observe down-regulation of linked-components associated with the Jacobs-Stewart cycle, including the intracellular carbonic anhydrase II (CA2), which governs cellular response to CO2 fluctuations that often accompany hypoxia in tumors. Further studies indicate an unusual mechanism of control for CA2 expression that, at least in part, reflects enhanced activity of the NFκB pathway, which is associated with loss of VHL.