Novel Immunohistochemical Biomarkers for Renal Cell Carcinoma Derived from Expression Microarray Data
AN Young, Q Yin-Goen, JH Phan, R Moffitt, MD Wang, AO Osunkoya. Emory University School of Medicine, Atlanta, GA; Atlanta VA Medical Center, Decatur, GA; Georgia Institute of Technology, Atlanta, GA
Background: Biomarkers discovered through microarray technology have been exploited in the development of several novel immunohistochemical assays for tumor diagnosis. We used this approach to identify novel diagnostic markers for renal cell carcinoma (RCC).
Design: RCC microarray datasets were assessed for quality control with the CaCorrect algorithm, and candidate biomarkers were identified with the OmniBiomarker algorithm. Candidate RCC biomarkers were verified by quantitative RT-PCR, using total RNA from fixed tissues of 17 clear cell, 13 papillary and 7 chromophobe RCC. Selected biomarkers were further verified by immunohistochemistry, performed on KIC1501 tissue microarray (Clonagen), which includes 66 clear cell, 16 papillary and 12 chromophobe RCC. Antibodies used were: anti- Carbonic anhydrase IX (CA9); anti-Schwannomin-interacting protein 1 (SCHIP1); and anti- Cytochrome c oxidase subunit 5a (COX5A). Intensity of staining was graded on a 0/1+/2+/3+ scale.
Results: CA9 was strongly overexpressed in clear cell RCC by microarray, and this pattern was verified by quantitative RT-PCR and immunohistochemistry (p < 0.001). SCHIP1 was strongly overexpressed in papillary RCC by microarray and quantitative RT-PCR. By immunohistochemistry, staining was seen in papillary and clear cell RCC, but 3+ intensity was significantly more frequent in papillary RCC (p < 0.001). COX5A was strongly overexpressed in chromophobe RCC by microarray and quantitative RT-PCR. By immunohistochemistry, staining for COX5A was seen in all RCC subtypes; however, 3+ intensity was significantly more frequent in chromophobe RCC (p < 0.02).
Conclusions: Biomarker expression profiling is expected to become more important for renal tumor classification, with both diagnositic and therapeutic implications. CA9 is a known clear cell RCC biomarker and potential therapeutic target. SCHIP1 has not been described in RCC previously, and should be considered as a supplementary biomarker for papillary RCC diagnosis. COX5A is a mitochondrial gene product; many such proteins are overexpressed in chromophobe RCC. These candidate markers should be evaluated in larger prospective studies to validate their clinical diagnostic utility.
Category: Genitourinary (including renal tumors)
Tuesday, March 10, 2009 9:30 AM
Poster Session III # 82, Tuesday Morning