Abstract 5154: Diagnostic serum markers for metastatic brain tumors identified by cross-species hybridization of microarrays in animal models

Introduction: Cancer-related mortality of many tumors is due to development of metastasis to the brain with limited response to conventional therapies. Diagnosis of metastasis to the brain depends on symptoms or imaging techniques, which often fail to detect small brain lesions. Serologic markers enabling early diagnosis of metastatic brain tumors would therefore significantly improve clinical outcome. Using the cross-species hybridization of microarrays differentiating human from mouse gene signatures, we identified proteins significantly increased in brain metastases were detected in the sera of mice bearing human cancer metastases to the brain and determined whether these can be potentially diagnostic. Materials and Methods: Human breast cancer (MDA-MB-231), lung cancer (PC-14), melanoma (A375), colon cancer (KM12), prostate cancer (PC-3P) and renal cancer (SN12) cells were implanted into relative primary and metastatic organs of nude mice. RNAs were extracted from tumor tissues and processed for differential hybridization of microarray. To identify genes differentially expressed in brain lesions, the random variance t test or one-way ANOVA was performed for the two-group or multi-group analysis, respectively. In the next set of experiments, we determined whether coded proteins differentially expressed in brain metastasis can be detected in the sera. MDA-MB-231 and PC-14 cells were implanted into mammary fat pad, lung or brain. Tumor tissues and sera were collected for immunohistochemical (IHC) analyses and antibody array with 13 available antibodies detecting proteins coded by genes differentially expressed in the brain metastases. Results: In the first set of experiments, common 210 genes were identified to be differentially expressed in metastatic brain tumors, as compared with tumors growing in other organs such as mammary fat pad, lung, skin, cecum, prostate, kidney, and bone. Among the proteins coded by the 210 genes, 13 with commercially available antibodies were selected for validation. In the second set of experiments, IHC revealed that all these 13 proteins were expressed in metastasis produced by MDA-MB-231 and PC-14. Compared to sera of mice bearing primary tumors, elevated level of 10 proteins was detected in sera collected from mice with brain metastases. Conclusion: These data demonstrated that cross-species differential hybridization of microarray with class comparison of gene expression using orthotopic animal is a novel approach to identify potential diagnostic serum markers for brain metastases. Studies to detect these proteins in the sera of patients with brain metastases are now planned. Citation Format: Ho Jeong Lee, Sun Jin Kim, Hyun Kyung Yu, Seung Wook Kim, Qiuyu Wu, Junqin He, Isaiah J. Fidler. Diagnostic serum markers for metastatic brain tumors identified by cross-species hybridization of microarrays in animal models. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 5154. doi:10.1158/1538-7445.AM2015-5154