Abstract 3926: Is FGD3 a potentially prognostic marker for breast cancer

Abstract

Abstract Background: Prognostic factors are capable of providing information on clinical outcomes at the time of diagnosis; they are usually indicators of growth, invasion, and metastatic potential (Gasparini G. et al. 1993; Hayes DF. et al. 1998). Tissue marker is one of the prognostic factors; to date, only a small proportion of markers are ultimately clinically useful, including Ki-67 and HER2. Faciogenital dysplasia 3 protein (FGD3), a putative regulator of cell morphology and motility, has been shown to regulate cell migration. In a study of 3,256 tumors, low expression of FGD3 mRNA indicates poor outcome (Hayakawa M. et al. 2008; Scooter W. et al. 2014). However, an immunohistochemistry (IHC) study to evaluate FGD3 protein expression has not been done. We hypothesize that the expression levels of FGD3 protein by IHC might improve the prediction of patient outcomes, and FGD3 might be a potentially prognostic marker of breast cancer. Materials and Methods: 322 cases of breast cancer Tissue Microarrays (TMA) (BR1504a, BR1505b, HBre-Duc068Bch-01, and BR20837) were purchased from US Biomax, Inc (Rockville, MD). Rabbit polyclonal antibody against FGD3 was purchased from Novus Biologicals, LLC (Littleton, CO). Tissue cores were stained for FGD3 with Dako’s EnVision + Dual Link System. Image acquisition was performed using an Olympus camera and software. FGD3 protein expression by IHC was quantitatively determined in the range of 0-4. Unpaired t-test was used for data analyses. Results: 1) Benign tumor and breast adenocarcinomas in lower stages showed strong expression of FGD3, whereas the breast adenocarcinomas in higher stages showed mild ~ weak expression. 2) Invasive breast cancer in stage IIA showed strong FGD3 expression compared to matched metastatic carcinoma which showed mild expression of FGD3. 3) FGD3 protein levels for tumors (n=135) with N0 indicating no regional lymph node metastasis were compared with tumors with lymph node metastasis (N1-3; n=98) and corresponding matched metastatic tissue (n=103). An unpaired t-test comparing N0 vs. N1-3 showed lymph node metastasis is associated with lower FGD3 protein levels (p<0.0001). Conclusion: FGD3 protein expression levels within breast tumors were different according to metastatic status. Our IHC results suggest the possibility of FGD3 to be a prognostic marker in patients with breast cancer. Citation Format: Yuliang Sun, Scooter Willis, Xiaoqian Lin, Justin Achua, Casey Williams, Brian Leyland-Jones. Is FGD3 a potentially prognostic marker for breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3926. doi:10.1158/1538-7445.AM2017-3926