PTEN and nonpapillary renal cell carcinoma: Xing et al. demonstrated that KLF5 deletion in PTEN-null mice upregulated epidermal growth factor (EGF) and its downstream signaling molecules AKT and ERK and initiated luminal-type mouse prostate tumors.38 It has been reported that tumor suppressor gene PTEN was deleted or mutated during ccRCC carcinogenesis.7, 39 KLF5 also could inhibit the activation of ERK in ccRCC (data not shown).