Nuclear respiratory factor 1 (NRF1) and inhibitor of differentiation protein 3 (ID3) are transcription regulating proteins. Recently we have uncovered a novel oncogenic function of NRF1 in breast cancer development and progression. In this study, we tested the postulate that exposure to PCB153 contributes in ID3 over-expressing endothelial stem cells (EndSCs) chaperoning and guiding of mesenchymal NRF1 breast cancer stem cells (BCSCs) across the blood-brain barrier. BCSCs/EndSCs were subjected to functional gain/loss of ID3 and/or NRF1 to test if PCB153 [1ng/ml] exposure produces NRF/ID3 signals regulating lineage specific BCSCs organ entry. First, we tested whether NRF1 promotes transmigration of breast cancer using a 3D blood-brain barrier (BBB) model consisting of breast tumor initiating cells (BTICs) or MDAMB231 cells, brain endothelial cell layer, and astrocytes. NRF1 overexpression increased the propensity for BTICs and mesenchymal enriched MDAMB231 BCSCs to adhere to brain endothelial cells and migrate across a human BBB model. Increased adhesion of NRF1+ BCSCs with ID3+ EndSCs was detected. ID3 EndSCs promoted the transmigration of BCSCs through the BBB. We found differential effects by endocrine disruptors, namely PCB153 and PCB77. The treatment with PCB153 showed increased growth of NRF1+ BCSCs tumor spheroids. PCB153 also induced the tumor cell adhesion to microvascular endothelium and transendothelial migration of BCSCs. The exosomal ID3 released from endothelial cells helped the mesenchymal NRF1+ BCSCs to cross through blood brain barriers. Xenograft experiments showed that ID3+ brain EndSCs not only supported the growth of estrogen treated NRF1+ BCSC tumorospheroids, but guided them to the brain in zebrafish. These findings show for the first time a key role for ID3 and NRF1 by which specific circulatory EndSCs accompany a particular sub-type of BCSCs to distant metastatic sites where they most likely facilitate the seeding, survival, and proliferation of BCSCs. This knowledge is important for pre-clinical testing of NRF1/ID3 modifying agents that prevent the spread of breast cancer to the brain. This work was, in part, supported by a VA MERIT Review (VA BX001463) grant to DR.

Citation Format: Jayanta K. Das, Mayur Doke, Alok Deoraj, Quentin Felty, Deodutta Roy. Exosomal ID3 is pro-metastatic through guiding NRF1-induced breast cancer stem cells across the blood-brain-barrier [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 1128.