MTOR and nonpapillary renal cell carcinoma: Not surprisingly, some known molecular markers of ccRCC include hypoxia-inducible factors (HIFs) - that in normal conditions are negatively regulated by VHL (von Hippel-Lindau) tumour suppressor protein and positively by the mammalian Target of Rapamycin (mTOR) [41, 42] - and their transcriptional targets, notably those encoding vascular endothelial growth factor (VEGFA), transforming growth factor α (TGFα), platelet-derived growth factor (PDGF), epidermal growth factor receptor (EGFR), all involved in cell proliferation and survival [43, 44].