PTK2B and nonpapillary renal cell carcinoma: Whereas PTK levels did not correlate with toxicity, STK levels did correlate with toxicity: STK levels were similar in ccRCC and normal kidney samples from patients that experienced grade 3 toxicity whereas in the population without toxicity STK levels were higher in ccRCC than in normal kidney (38 peptides significantly different phosphorylated, 1 peptide lower, 37 peptides more phosphorylated in ccRCC, Table 1).