Grap2 and Cyclin-D Interacting Protein (GCIP) Nuclear Expression Is Significantly More Frequent in Triple-Negative Breast Carcinomas (TNBCs) than Other Subtypes of Breast Carcinomas
WC Chen, MC Chang, TW Chang. National Cheng Kung University Medical Center, Tainan, Taiwan
Background: GCIP is a putative tumor suppressor in human carcinomas. GCIP exerts its function in the nucleus. In vivo studies showed GCIP bound to cyclin D1, reduced the phosphorylation of retinoblastoma protein and leaded to inhibition of the transcriptional activity mediated by E2F1 protein. Using immunophenotypes, molecular subtypes of breast carcinomas can be divided into four groups: luminal A (ER+ and/or PR+, HER2-), luminal B (ER+ and/or PR+, HER2+ ), HER2 (ER- and PR-, HER2+) and TNBC (ER-, PR-, HER2-). Of these subtypes, TNBC is a distinct group with poor prognosis and currently lacks targeted therapies. In this study, we compared GCIP nuclear expression using immunohistochemistry in the four subtypes of breast carcinomas.
Design: Fifty-three cases of primary invasive breast carcinomas were retrieved from archival files at our institution. Cases were further subdivided into luminal A, luminal B, HER2 and TNBC as defined above. The status of HER2 was determined by immunohistochemistry and followed by fluorescent in situ hybridization if the immunohistochemical results were equivocal. Immunohistochemical staining using GCIP monoclonal antibody was performed on whole tissue sections of all cases.
Results: Of 53 primary breast carcinomas, 29 (54.7%) were luminal A, 10 (18.9%) were luminal B, 4 (7.5%) were HER2 and 10 (18.9%) were TNBCs. GCIP nuclear staining was observed in 5 of 29 (17.2%) luminal A carcinomas, 1 of 10 (10%) luminal B carcinomas, none of 4 (0%) HER2 carcinomas and 7 of 10 (70%) TNBCs. TNBCs had significantly more frequent GCIP nuclear staining than other subtypes of breast carcinomas (p=0.002).
Conclusions: A significant percentage of TNBCs have GCIP nuclear expression compared to other subtypes of breast carcinomas. Contrast to other subtypes, the tumorigenesis of TNBCs may not involve inactivation of GCIP.
Tuesday, March 10, 2009 1:00 PM
Poster Session IV # 28, Tuesday Afternoon