HIFa isoform specific activation drives cell-type specificity of VHL-associated oncogenesis

Cancers arising from dysregulation of generally operative signaling pathways are commonly tissue specific, but the mechanisms underlying this paradox are poorly understood. Based on striking cell-type specificity, we postulated that these mechanisms must operate very early in cancer development and set out to study them in a model of von Hippel Lindau disease. Biallelic mutation of the VHL ubiquitin ligase leads to constitutive activation of hypoxia inducible factors HIF1A and HIF2A and is often a truncal event in clear cell renal carcinoma. We used an oncogenic tagging strategy in which VHL-mutant cells are marked by tdTomato, enabling their observation, retrieval, and analysis early after VHL-inactivation. Our findings reveal markedly different consequences of HIF1A and HIF2A activation, but that both contribute to renal cell-type specific consequences of VHL-inactivation in the kidney. Early involvement of HIF2A in promoting proliferation within proximal tubular epithelium supports therapeutic targeting of HIF2A early in VHL disease. Vhl(KO/flox); Hif1a(flox/flox) (VHKO), Vhl(KO/flox); Epas1(flox/flox) (VEKO) and Vhl(KO/flox); Hif1a(flox/flox); Epas1(flox/flox) (VHEKO) mice carrying the renal tubular epithelium specific Pax8-CreERT2 were dosed with 5x 2 mg tamoxifen and harvested either at an early (1-3 weeks) or late (4-12 months) timepoints after dosing. Cre-mediated recombination marked Vhl and Hif1a and/or Epas1 recombination with the expression of tdTomato. tdTomato-positve cells were retrieved by FACS and subjected to scRNA-seq using the 10X Chromium NextGEM platform.