Abstract 4291: Bai1 inhibition promotes ferroptosis of breast cancer cells to prevent tumor growth in human xenograft tumor models
Authors: Noubissi Felicite Kamdem , Odubanjo Oluwatowin , Huang Hung-Chung , Ogle Brenda , Tchounwou Paul 
Published: March 2024

The adhesion G-protein coupled- receptor 1 ADGRB1/Bai1 was identified as a phosphatidylserine receptor that cooperates with ELMO/Dock180/Rac to promote maximal engulfment of apoptotic cells. This function of Bai1 was also shown to promote myoblasts fusion. Cell-cell fusion has been demonstrated to occur in normal physiological functions as well as in diseases. Studies have shown in cancer that cell-cell fusion increases tumor heterogeneity, drug resistance, and metastasis as hybrids acquire new properties that allow them to migrate and proliferate at new sites. Activation of ELMO-Dock signaling pathway has been associated with breast cancer metastasis. Moreover, ELMO1 has been identified as a modifier of breast cancer risk for BRCA mutation carriers. Rac1 was also shown to be overexpressed in proliferative breast disease, preinvasive and invasive breast carcinoma as well as lymph node metastases. Our recent studies showed that breast cancer cell fusion with bone marrow-derived mesenchymal stem cells was modulated by hypoxic conditions and promoted by apoptosis. Our hypothesis is that hypoxia stress induced apoptosis activates the phosphatidylserine receptor Bai1, and it signals through the ELMO/DOCK180/Rac to promote breast cancer cell fusion-driven tumor heterogeneity and metastasis. In this study, we determined the ability of Bai1 depleted breast cancer cells to induce tumor growth in immunocompromised mice. We used Bai1 sgRNA to inhibit Bai1 expression in the breast cancer cell MDA-MB-231. These cells (1x 106) together with bone marrow-derived mesenchymal stem cells (MSCs) (1x 106) were injected into the fat pad of the breast of 15 NOD SCID female mice. Control mice (15) received the same cells with no inhibition of Bai1. The mice were monitored for eight weeks. We found that Bai1 inhibition significantly reduced tumor growth in these mice in the course of time (P&lt;0.05). The average tumor weight was also significantly reduced when Bai1 was inhibited (P&lt;0.001). RNA sequencing of tumors generated from these mice revealed a significant increase in the expression of genes driving ferroptosis and a reduction in critical oncogenes in the experiment group compared to the control group. These findings will be helpful in the development of new classes of drugs effective in breast cancer treatment. Grant Support The NIH/NIMHD grant 5U54MD015929-03, the Society for Investigative Dermatology (SID) Freinkel Diversity Fellowship, and NSF Award Notice for Award ID 2142465 (awarded to FNK).

Citation Format: Felicite Kamdem Noubissi, Oluwatowin Odubanjo, Hung-Chung Huang, Brenda Ogle, Paul Tchounwou. Bai1 inhibition promotes ferroptosis of breast cancer cells to prevent tumor growth in human xenograft tumor models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4291.