Abstract 6121: UCP2 inhibitor eradicates cancer stem-like population in trastuzumab-resistant HER2-positive breast cancer

Abstract Purpose: Uncoupling protein 2 (UCP2) is a member of the mitochondrial anion carrier protein family that plays an important role in stabilizing the inner mitochondrial membrane potential (MMP, ΔΨm) and controlling reactive oxygen species (ROS) production. A selective UCP2 inhibitor, genipin is known to elicit cytotoxicity in several cancers, however, its effects on cancer stem cells (CSCs)-like properties and trastuzumab resistance in HER2-positive breast cancer cells have not been fully elucidated. In the present study, we sought to investigate the mechanism of action of genipin responsible for the induction of apoptosis and its effects on CSC-like features, expression of HER family member and trastuzumab resistance in HER2-positive breast cancer cells in vitro and in vivo. Experimental Designs: The effects of genipin on trastuzuamb-sensitive [BT474 and SKBR3] and trastuzumab-resistant [JIMT-1 and MDA-MB-453] HER2-positive breast cancer cell lines in vitro were evaluated for cell viability, Sub-G1, ROS, MMP, ALDH1 activity, CD44+/CD24- subpopulation and mammosphere formation. To confirm the physiological relevance of our in vitro observations, we explored the impact of genipin on tumor growth and angiogenesis and expression of p95HER2 and ALDH1A1 in trastuzumab-resistant xenograft model in vivo. Results: HER2-positive breast cancer cells harbored a higher level of UCP2, when compared to their counterparts. Genipin significantly downregulated UCP2 and mitochondrial dysfunction coinciding with increased ROS generation and disruption of MMP. These phenomena were accompanied with upregulation of the Bax/Bcl-2 ratio and activation of caspase-3 and caspase-7. Genipin treatment led to significant reduction in levels of truncated p95HER2, p-HER2, p-HER3 and p-Akt levels in both trastuzumab-sensitive and -resistant lines. Marked decline of CD44 and ALDH1A1 expression by genipin treatment was associated with attenuation of mammosphere-forming ability. UCP2 level is predominantly upregulated in CSC-enriched populations, while its knockdown significantly suppressed CSC-like characteristics concomitant with decreased ALDH1A1 and CD44 expression as well as impairment of ALDH1 activity. Genipin administration significantly retarded tumor growth and angiogenesis in trastuzumab-resistant JIMT-1 xenograft tumors. The antitumor effect occurred concomitantly with a decrease in Ki-67 proliferating index and enhancement of apoptosis. Furthermore, individuals receiving genipin exhibited markedly lower levels of p95HER2, full-length p185HER2, CD44 and ALDH1A1 expression compared to their control counterparts. Conclusion: To our knowledge, our findings are the first reported instance of genipin-induced suppression of CSC-like properties and HER2/HER3/Akt axis, implying that genipin treatment may have application in addressing trastuzumab resistance. Citation Format: Minsu Park, Soeun Park, Juyeon Seo, Dongmi Ko, Seongjae Kim, Yong Koo Kang, Kee Dal Nam, So Ra Seuk, Tae-Min Cho, Eunsun Jung, Yoon-Jae Kim, Ji Young Kim, Jae Hong Seo. UCP2 inhibitor eradicates cancer stem-like population in trastuzumab-resistant HER2-positive breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6121.