Abstract 385: Predictive factors of c-kit-positive cancer stem cells, epithelial-mesenchymal transition and circulating tumor cells in distant metastasis formation in non-small cell lung cancer

Abstract

Abstract Cancer stem cells (CSC) are a rare subpopulation of undifferentiated cells that are responsible for tumor initiation and tumor regeneration after chemotherapy. Although a universal marker for CSCs has not been identified, previous studies showed that c-kit (CD117) functioned as a stem cell factor (SCF) receptor, and SCF-ckit signaling axis was essential for self-renewal and proliferation of lung CSCs. During tumorigenesis, subsets of tumor cells disseminate from primary tumors by undergoing phenotypic changes that allow the cells to penetrate blood vessels. These changes are accompanied by a process described as epithelial-mesenchymal transition (EMT). EMT endows epithelial cells with enhanced invasive potential by the loss of their epithelial characteristics and the acquisition of a mesenchymal phenotype. The aim of this study is to correlate c-kit-positive CSCs and EMT-positive, subpopulations of circulating tumor cells (CTCs) with clinicopathological parameters to verify whether these biomarkers contribute to cancer distant metastasis in non-small cell lung cancer (NSCLC). A total of 31 patients with NSCLC were enrolled into this study and evaluated for CTC levels at baseline. Peripheral blood samples (5 ml, anticoagulated with EDTA) were collected, transferred to the CanPatrol CTC tube, and then processed within 8 hours. The CanPatrol CTC enrichment technique was used to isolate and characterize CTCs. The first step of this technique was to isolate CTCs via a filter-based method; then, an quantifiable, quadruple-colorimetric RNA in situ hybridization (ISH) method was used to examine CTCs for expression of four epithelial (E) biomarkers (cytokeratins (CKs)8,18 and 19; and epithelial cell adhesion molecule (EpCAM)), two mesenchymal (M) biomarkers (vimentin and twist), c-kit and CD45. Using this technique, CTCs were detected in 25(80.6%) of 31 blood samples, and five categories of CTCs were defined using EMT biomarkers ranging from exclusively epithelial (E) to intermediate (E > M, E = M, M > E) and exclusively mesenchymal (M). Of the CTC-positive samples, 13(52%) samples contained c-kit-positive CTCs, and the percentage of cells with c-kit expression was 27.8%, with 2.1%, 4.6%, 2.1%, 18.3% and 0.8% in exclusively E, E > M, E = M, M > E and exclusively M CTCs, respectively. The expression of c-kit showed a high statistically significant correlation with distant metastasis (P = 0.0001). Compared with the non metastatic or regional metastatic carcinoma, mesenchymal CTCs (including M > E and exclusively M) were predominant in patients with distant metastatic carcinoma (P = 0.033). However, the sample size of this study was small, further validation needed to be done with a larger sample size. In summary, mesenchymal CTCs or/and c-kit may be potential predictive factors for invasion and metastatic spread of NSCLC. Citation Format: Shiyang Wu, Jianyu Sun, Weihua Qiu, Suyan Liu, Yujie Ma, Jiaming Che, Beili Gao, Jiasen Xu, David K. Ann. Predictive factors of c-kit-positive cancer stem cells, epithelial-mesenchymal transition and circulating tumor cells in distant metastasis formation in non-small cell lung cancer. [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 385. doi:10.1158/1538-7445.AM2015-385