Abstract 2493: Knocking down the expression of DCLK1 reduces mammary tumor formation, tumor cell self-renewal and metastasis: DCLK1 a novel therapeutic target in breast cancer

Abstract

Abstract Introduction: Breast cancer is a heterogeneous disease, and is comprised of a rare population of cells that display stem cell-like properties with high metastatic potential and relative resistance to conventional therapies. Doublecortin-like Kinase 1 (DCLK1) has recently been identified as a tumor stem cell marker in the intestine and pancreas and is overexpressed in many cancers including breast cancer. In this study, we targeted DCLK1 as a novel therapeutic strategy in breast cancer cells to reduce cancer cell self-renewal, tumorigenesis and metastasis. Methods: Anti-DCLK1-siRNA was transfected into breast cancer cell lines (MCF7 [luminal] and MDAMB231 [basal-triple negative breast cancer cell line]). For analysis of circulating tumor cells, MDAMB231/MCF7 cells were stably transfected with RFP (red fluorescence protein). Tumor cell colony formation, mammosphere formation (self-renewal), cell migration and invasion were assessed to evaluate the effect of DCLK1 knockdown and or DCLK1 overexpression on breast cancer cells self-renewal and metastatic potential. Xenograft model was used to identify the role of DCLK1 on breast cancer cell growth and circulating tumor cells in vivo. The data were generated utilizing experimental protocols for clonogenic culture, circulating tumor cells, immunohistochemistry, RT-qPCR and Western blotting. Results: Expression of DCLK1 was ∼36% higher in human breast cancer tissues than in normal breast tissue. Silencing DCLK1 via RNA interference decreased the colony formation (∼70%), and self-renewal ability (∼85%), of the breast cancer cell lines in vitro. In vitro migration and invasion assays demonstrated that knocking down DCLK1 led to less (40-80%) breast cancer cells migration and invasion. Furthermore, expression of EMT associated factors (Slug, Snail, Twist, Zeb-1, Zeb-2 and Vimentin) and pluripotency factors (c-Myc, Sox2, Nanog and Oct-4) were markedly reduced between 30 and 50%, after silencing DCLK1. Inhibition of DCLK1 in xenograft tumors resulted in reduced tumor growth (∼81%) and CTCs (∼95%) in vivo. However, overexpression of DCLK1 in the non-metastatic MCF7 breast cancer cell line increased its in vitro migration and invasion potency and pluripotency along with in vivo tumor formation and progression. Conclusions: DCLK1 expression is associated with breast cancer cell self-renewal, metastasis and tumorigenesis. Targeting DCLK1 reduced breast cancer cell self-renewal, CTCs, metastasis and tumor growth. DCLK1 inhibition may represent a novel targeted therapeutic approach to reduce the morbidity and mortality associated with breast cancer. Citation Format: PARTHASARATHY CHANDRAKESAN, Nathaniel Weygant, Dongfeng Qu, William Berry, Randal May, Naushad Ali, Sripathi Sureban, Eddie Bannerman-Menson, Michael Schlosser, Courtney Houchen. Knocking down the expression of DCLK1 reduces mammary tumor formation, tumor cell self-renewal and metastasis: DCLK1 a novel therapeutic target in breast cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2493.