Abstract 4227: Influence of anti-angiogenic therapy on the prevalence of breast cancer stem cells

Abstract

Abstract Purpose: The objectives of this study are to investigate the effects of anti-angiogenic therapy on breast cancer stem cell (BCSC) prevalence and hemodynamic imaging factors associated with these biomarkers. Introduction: Angiogenic inhibitors in breast cancer patients have shown to increase progression-free survival but not overall survival. Targeting the tumor vasculature can be used to alter the microenvironment (hypoxic)-niche, either enhancing BCSC subpopulations or causing these cells to differentiate. In this study, mice bearing triple-negative inflammatory breast tumors were treated with different dose regimens of VEGFR2 inhibitors and changes in ALDH1, EpCAM, and DLL1 measured. Material and Methods: Four cohorts of athymic nude mice bearing SUM149 breast tumors were treated with a low-(LD) (10mg/kg), moderate-(MD) (40mg/kg), and a high-dose (HD) (120mg/kg) of DC101, an anti-VEGFR2 monoclonal antibody, 3-times every three days. One group was not treated. All groups were imaged prior to and after treatment using DCE-CT and PCT-S to assess vascular physiology (perfusion, fractional plasma volume, permeability) and hemoglobin status (SaO2), after which the tumors were excised, fixed, sectioned at 4-6 different planes (1-2mm apart) and stained for ALDH1, EpCAM, and DLL1. Expression was calculated by determining the percent of the tissue exceeding a threshold determined from positive controls. Results: A reduction in ALDH1 and DLL1 expression was observed between untreated and MD group (3.6 to 1.0%, P = 0.03; 18.3 to 1.5%, P = 0.1), with a subsequent increase from MD to HD groups (1.0 to 1.9%, P = 0.08; 1.5 to 3.6%, P = 0.02). Changes in EpCAM were not observed (P>0.25). In vivo imaging results (DCE-CT and PCT-S) indicate, on average, favorable changes in tumor hemodynamic parameters may have occurred within the MD treated group, where perfusion (+26%) and Fp (-30%) on average resulted in a shorter mean-transit-time and the fraction of the vasculature with low SaO2 levels decreased (from 23% to 10%) not observed in LD or HD groups (but not reaching significance). Conclusions: Anti-angiogenic drugs targeting VEGFR2 in inflammatory TNB cancer has been shown to modulate ALDH1 and DLL1, but not EpCAM. Preliminary data demonstrate that vascular physiologic parameters obtained from DCE-CT and PCT-S may provide potential diagnostic factors. Given the overlap of ALDH1 and DLL1 with Notch and subsequent VEGF pathways, both a biomechanistic and oxygen microenvironment influence may be involved in modulating BCSC maintenance. Citation Format: Connor Holloway, Huisi Ai, Mario Dzemidzic, Marc Mendonca, Harikrishna Nakshatri, Keith Stantz. Influence of anti-angiogenic therapy on the prevalence of breast cancer stem cells. [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 4227.