# Co-first author: W.T., G.L., X.X.

* Co-Correspondence: C.G. and W.G.J.


Background: Circulating tumor cells (CTCs) display changes in epithelial-mesenchymal transition (EMT) markers and miRNAs regulate EMT in breast cancer cells. The association between EMT characteristics and miRNA expression in CTCs of metastatic breast cancer (MBC) patients and their clinical implications remain unknown.

Methods: CTC-specific miRNAs were screened based on comparison of the miRNA profile between CTC and primary tumor. RT-PCR was used to quantity the expression levels of EMT makers and miRNA candidates. We enrolled 219 MBC patients with CTCs ≥ 5/7.5mL blood from 2 cohorts and CTCs were detected and enriched by CellSearch. Overall survival (OS) and radiological response were analyzed. CTCs were divided into epithelial- (E-CTCs) and mesenchymal-like CTC (M-CTCs) phenotypes based on a cut-off value derived from suspended breast cancer cells recovered from PBMCs.

Results: MiR-106b displayed upregulation in CTCs, with a higher level in M-CTCs than E-CTCs. Patients with E-CTCs showed better OS than those with M-CTCs (HR 1.77, 95% CI 1.14-2.78, P =0.012). CTCs from chemo-resistant MBC patients exhibited higher miR-106b. CTC-specific miR-106b was negatively associated with therapy response and OS (HR 1.73, 95% CI 1.06-2.84, P = 0.029).

Conclusions: CTC-specific miR-106b was associated with EMT phenotypes of CTCs and may predict prognosis in MBC patients.

Citation Format: Tan W, Liang G, Xie X, Tan L, Sanders AJ, Liu Z, Ling Y, Zhong W, Jiang WG, Gong C. Expression of miR-106b in circulating tumor cells is associated with EMT and prognosis in metastatic breast cancer patients [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P6-09-07.