RCC with molecular characteristics that resulted in pronounced polycythemia.

Computed tomography of the abdomen showing a left-sided renal mass (arrow) with central necrosis (A). Ribonuclease protection assay for EPO transcripts (B, left panel) and other hypoxia-inducible genes (B, right panel) demonstrated markedly elevated expression of these genes in the tumor (T) as compared with the control (C) adjacent nontumorous kidney tissue. Cell extracts from HepG2 cells were exposed to normoxia (N) or 16 hours of hypoxia (H) for comparison. U6sn served as internal control. Radiolabelled probes were protected from ribonuclease digestion by hybridization to 50 μg or 1 μg total RNA for HIF targets and U6sn, respectively. M indicates molecular weight marker; P, digested riboprobes; and U6sn and EPO, undigested riboprobes. Immunohistochemistry for HIF-1α of the tumor tissue shows homogenous nuclear staining of virtually every tumor cell (C). Sections were counterstained with Richardson's reagent. Magnifications are 100 × and 800 ×, respectively. Immunoblotting of protein extracts from tumor (T), control kidney tissue (C), and HepG2 cell extracts under normoxia (N) and 4 hours of hypoxia (H) demonstrates pronounced up-regulation of HIF-1α and HIF-2α proteins (arrows in panel D). The position of the 97 kd marker is indicated.