Abstract 4173: 2′-Hydroxyflavanone inhibits RLIP and suppresses breast cancer cell proliferation and metastasis
Authors: Singhal Sharad S. , Chikara Shireen , Singhal Jyotsana , Horne David , Salgia Ravi , Awasthi Sanjay 
Published: September 2020

Abstract
Breast cancer (BC) is one of the most common malignancies diagnosed in women, and this metastatic disease has a high mortality rate despite improvement in clinical outcome of targeted primary tumors. Management of triple-negative breast cancer (TNBC) becomes even more challenging due to lack of targeted therapy and systemic toxicity induced by current treatment regimens. Therefore, there is a need to identify new non-toxic treatment strategies to effectively treat TNBC. In the current study, we evaluated the anti-metastatic effects of 2'-Hydroxyflavanone (2HF), a flavonoid present in citrus fruits, in TNBC cell lines and in orthotopic mouse model of breast-to-lung metastasis. 2HF treatment reduced in-vitro cell viability of BC cells and also suppressed their migratory and invasive potential. Further, 2HF resulted in reduction in protein levels of RLIP, Kras, pERK, pStat3, and pP70S6K. RLIP (encoded by RALBP1; [18p11.22]) has emerged as a promising target for cancer treatment, because it is overexpressed in a variety of cancer cell lines and tumor tissues. RLIP is an ATP-dependent non ATP-binding cassette (ABC) transporter that is responsible for the major transport function in many cells, including cancer cell lines, causing the efflux of glutathione (GSH)-electrophile conjugates (GS-Es) of both endogenous metabolites and environmental chemical toxins. RLIP is essential for tumor growth and metastasis. In-vivo studies revealed that 2HF (50 mg/kg b.w.), RLIP antisense (RAS; 5 mg/kg b.w.) and RLIP antibody (Rab; 5 mg/kg b.w.) treated mice had significantly lower primary tumor-weight and exhibited reduced lung metastasis as compared to control treated mice. Mice treated with combination of 2HF+RAS+Rab has significantly lower tumor weight and exhibited no metastasis as compared to single agent treated mice. Western blotting and immuno-histological studies revealed that the levels of RLIP inhibition by 2HF were comparable to inhibition/depletion of RLIP by Rab and RAS alone. In addition, inhibition in Ki67, CD31, vimentin, and an increase in E-cadherin was observed in 2HF, RAS, and Rab treated mice and this effect was pronounced in 2HF+RAS+Rab group. These results indicate that 2HF suppresses in-vitro BC cell motility and invasion. In addition, it suppresses metastasis of BC cells to lungs in an orthotopic mouse model of BC by targeting RLIP protein. Collectively, our results suggest that 2HF has potential to be combined with RLIP inhibition/depletion to more effectively suppress primary breast tumor growth and its metastasis to distant organs.
Citation Format: Sharad S. Singhal, Shireen Chikara, Jyotsana Singhal, David Horne, Ravi Salgia, Sanjay Awasthi. 2′-Hydroxyflavanone inhibits RLIP and suppresses breast cancer cell proliferation and metastasis [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 4173.