Abstract P1-05-10: lncRNA UBA6-AS1 participates in the integrated stress response of breast cancer

Breast cancer is the most prevalent malignant neoplasm among women worldwide and in Taiwan, and the incidence of breast cancer has been increasing over the past years. Accumulating studies has shown that multiple stress responses are activated in breast cancer. Oncogene activation, massive proliferation and increased nutrient demands often result in nutrient and oxygen deprivation, which triggers integrated stress response (ISR) in tumor cells. ISR dictates the cellular adaptive signaling in response to the intrinsic and extrinsic stresses, which lead to endoplasmic reticulum (ER) stress and cytosolic stress. Delineating the regulatory mechanisms of ISR may help us understand how cancer cells adapt and survive under stressed condition. To elucidate the role of long non-coding RNAs (lncRNAs) in the ISR of breast cancer, we have performed a two-step human lncRNA RNA interference (RNAi) screening coupled with cell viability assays in a breast cancer cell line MDA-MB-231 under glucose deprivation to induce extrinsic metabolic stress. A novel lncRNA, UBA6-AS1, was identified to be upregulated to promote breast cancer cell death upon glucose deprivation. Besides of glucose deprivation, UBA6-AS1 was also induced by the deprivation of amino acids including glutamine and arginine in several breast cancer cell lines, suggesting that the upregulation of UBA6-AS1 was a universal metabolic stress event. We also found that UBA6-AS1 expression was increased upon the administration of ER stress inducers, tunicamycin (Tm) and thapsigargin (Tg) in breast cancer cells, implicating a potential role of UBA6-AS1 in harmonizing the nutrient and ER stresses. Moreover, after analyzing the genomic position and sequence of UBA6-AS1, activating transcription factor 4 (ATF4), a critical regulator in the ISR coordinating nutrient and ER stress signaling for controlling cell survival and stress adaption, has been predicted to be the regulator of UBA6-AS1 upon the induction of nutrient stress, further supporting the role of UBA6-AS1 participating in the ISR of breast cancer cells. Depletion of UBA6-AS1 rendered breast cancer cells more resistant to nutrient deprivation, and the opposite results were observed when UBA6-AS1 was overexpressed, indicating that UBA6-AS1 may participate in the regulation of breast cancer cell survival under metabolic stress. To investigate the function of UBA6-AS1, RNA-sequencing (RNA-seq) was performed to profile gene expression in breast cancer cells overexpressing UBA6-AS1. The RNA-seq analysis revealed that the top 10 enriched biological processes were mostly related to apoptosis or programmed cell death in the UBA6-AS1 overexpressing cells, suggesting that the up-regulation of UBA6-AS1 may induce apoptosis in response to metabolic stress. In the future, we will focus on the molecular mechanism of the regulation and function of UBA6-AS1 as well as its biological role and association with breast cancer progression. Citation Format: Yi-Zhen Wu, Yi-Hsuan Chen, Chun-Ting Cheng, Kevin Chi, Tse-Chun Kuo, Hsing-Jien Kung, David Kong Ann, Ching-Ying Kuo. lncRNA UBA6-AS1 participates in the integrated stress response of breast cancer [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P1-05-10.