Background: Breast cancer is one of the leading causes of cancer death for women worldwide. Major hurdles for a successful treatment are cancer metastases, resistance to therapy and disease recurrence. The presence of circulating epithelial tumor cells (CETCs) is closely related to metastasis formation, but the mechanisms through which CETCs promote recurrence of disease are still unclear. CD36 is found in the cell membrane of tumor cells and responsible for taking up fatty acid. It is known that CD36 is a general marker of metastatic cells and its amplification specifically correlated with metastasis in a large number of human tumors. Therefore, the aim of this study was to determine the metastatic marker CD36 on CETCs and to correlate it's frequency with clinicopathological features in breast cancer patients.

Methods: CETCs were determined from blood of 42 patients suffering from breast cancer. The number of vital CETCs and their expression of CD 36 was investigated using the maintrac® method.

Results: CD36 expressing CETCs were detected in 95 % of breast cancer patients. Breast cancer patients with metastatic disease had significantly more CD36 positive CETCs as compared to patients without metastases (median 72% vs. 48%; p<0.05). The fraction of CD36 positive CETCs was significantly higher in patients with HER2 positive primary tumor (69% vs. 54%; p<0.05). Furthermore, triple negative breast cancer patients had significantly more CD36 positive CETCs as compared to hormone receptor positive tissue (median 62% vs. 52%; p<0.05). Interestingly, frequency of CD36 positive CETCs correlated significantly with a blinded determination of Ki-67 proliferation index in tumor tissue (r=0.75; p<0.01). We observed a significant heterogeneity in CD36 immunostaining intensity across CETCs from the same patients.

Conclusion: We showed for the first time that breast cancer patients have detectable CETCs with a high frequency of CD36 which highly correlated with progression of cancer disease. Our findings suggest that using a CD36 antibody treatment may be an effective strategy to fight cancer.

Citation Format: Monika Pizon, Dorothea Schott, Ulrich Pachmann, Katharina Pachmann. A subpopulation of circulating epithelial tumor cells positive for fatty acid receptor CD36 is linked to aggressiveness of breast cancer disease [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5193.