Protein expression and gene mutation status of KIT and PDGFRA in renal cell carcinoma

The author investigated protein expression and gene mutations of KIT and PDGFRA in 61 consecutive surgical cases of renal cell carcinoma (RCC). The cases of RCC consisted of 43 clear cell RCC (CCRCC), 9 chromophobe RCC (ChrRCC), or 9 papillary RCC (PaRCC). Normal distribution of KIT and PDGFRA protein was also examined in non-tumorous normal parenchyma (n=10). In normal kidneys, KIT was expressed in distal convoluted tubules and collecting ducts, and PDGFRA in distal and proximal convoluted tubules and collecting ducts. KIT expression was recognized in 9 ChrRCC (100%, 9/9), but not in 43 CCRCC (0%, 0/43) and 9 PaRCC (0%, 0/9). PDGFRA expression was recognized in 7 CCRCC (16%, 7/43) and 2 PaRCC (28%, 2/9), but not in ChrRCC (0%, 0/9). A molecular genetic analysis using PCR-direct sequencing was performed in selected 30 cases (ChrRCC=9, CCRCC=12, PaRCC=9): it revealed no mutations in KIT (exons 9, 11, 13, and 17) or PDGFRA (exons 12 and 18) genes in any cases examined. These results suggest that in normal renal parenchyma KIT is expressed in distal convoluted tubules and collecting ducts, and PDGFRA in proximal and distal convoluted tubules and collecting ducts, that KIT is expressed exclusively in ChrRCC and its incidence is 100%, that KIT-positive ChrRCC was negative for PDGFRA, that PDGFRA is expressed in a small percentage in CCRCC and PaRCC, and that mutations of KIT (exons 9, 11, 13, and 17) and PDGFRA (exons 12 and 18) are absent in RCC.