Abstract 4410: miRNA-34a sensitizes triple-negative breast cancer cells to paclitaxel reducing cancer stem cell population and lung colonization

Abstract

Abstract Background: Cancer stem cells (CSCs) have inherent or developed drug resistance for which chemotherapy fails to eliminate all tumor cells, a property that is critically contributing to recurrence and metastasis. Here, we combine miR-34a, a well-known tumor suppressor miRNA that controls proliferation, apoptosis and self-renewal, with Paclitaxel (PTX), a commonly used first-line chemotherapy drug. Based on our preliminary observations (Bonetti et al., manuscript under revision), we hypothesized a combinatorial approach, coupling miRNA- and chemo- treatment, aimed at reducing CSCs in vitro and recurrence in vivo using triple-negative breast cancer (TNBC) as a model. Methodology: As a model, we exploited SUM159pt cells (TNBC mesenchymal-like, with CSC features) to mimic aggressive breast cancer, which harbor a vector for pLUC, which is induced by luciferin in vivo, to monitor tumor growth in real time. Furthermore, we used i) pSlik34a, with tunable expression of miR-34a by doxycycline; ii) treatment with PTX to select for resistant cells (RC); and combined the two, by treating RC with doxycycline. CSC content was evaluated by ALDH (Aldehyde Dehydrogenase) activity, sphere-forming efficiency (SFE) and qRT-PCR of known markers. A similar approach was followed for in vivo studies, with NSG female injected through tail vein injection with 500,000 SUM159/pLUC/pSlik34a cells, and separated into three groups: not treated (NT), PTX alone, and PTX+34a. Results: As observed for aggressive breast cancer, treatment of SUM159 with PTX generated resistant cells (RC) with increased CSC content (ALDH activity and spheres forming ability). When miR-34a was induced in the RC, cells changed morphology, slowed proliferation rate, and decreased CSC content (ALDH activity and spheres). Moreover, a second PTX treatment almost completely abolished the ALDH activity and SFE. The combined effect was evaluated in vivo, following by luminescence the growth of metastases after lung colonization, with PTX+34a mice reducing lung colonization than the PTX treatment or miR-34a treatment alone. Conclusions: Overall, these results indicate that miR-34a sensitize PTX-resistant cells reducing cancer stem-cell capacities, and in this preclinical setting limited the aggressive phenotype of breast cancer, including proliferation, drug resistance, relapse and metastasis causing in delay of lung colonization in vivo. Citation Format: Montserrat Climent, Paola Bonetti, Francesco Nicassio. miRNA-34a sensitizes triple-negative breast cancer cells to paclitaxel reducing cancer stem cell population and lung colonization [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 4410.