The midbody (MB) is a singular organelle formed between daughter cells during cytokinesis and required for their final separation. MBs persist in cells long after division as midbody derivatives (MBds), but their fate is unclear. Here we show that MBds are inherited asymmetrically by the daughter cell with the older centrosome. They selectively accumulate in stem cells, induced pluripotent stem cells (iPSCs) and potential cancer ‘stem cells’ (CSCs) in vivo and in vitro. MBd loss accompanies stem cell differentiation, and involves autophagic degradation mediated by binding of the autophagic receptor, NBR1, to the MB protein Cep55. Differentiating cells and normal dividing cells do not accumulate MBds and possess high autophagic activity. Stem cells and cancer cells accumulate MBds by evading autophagosome encapsulation and exhibit low autophagic activity. MBd enrichment enhances reprogramming to iPSCs and increases in vitro tumorigenicity of cancer cells. These results suggest unexpected roles for MBds in stem cells and CSCs.

ZEB1 is a protein of 1124 amino acids with a predicted relative molecular mass ~124K. However, in Supplementary Fig. S5 (corresponding to Fig. 4a) of our manuscript, the uncropped image of the ZEB1 immunoblot shows two bands with a relative molecular mass of 200K and 125K, respectively. Two major ZEB1 signals (M r 124K and 200K) have been observed in western blots when using different antibodies in various cell types (please see references 1-4 below). Therefore, to examine whether the bands observed in our study represent ZEB1, we knocked down ZEB1 in MCF12A control and p53 R175H mutant cells using shRNA (Fig. 1a) and siRNA (Fig. 1b). As shown in the figure to the right, both of the bands are diminished by knockdown of ZEB1, indicating that these bands are ZEB1.

No abstract

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.

No abstract

Background Lineage plasticity is recognized as a treatment-induced resistance mechanism in prostate cancer (PCa) and contributes to the development of neuroendocrine prostate cancer (NEPC), a lethal variant of castration-resistant prostate cancer (CRPC), that is increasing in the era of second-generation anti-hormonal therapy. At present, there are no effective treatments for NEPC. Conclusions and perspectives Following our long-standing interest in studying RE1-silencing transcription factor (REST), a pivotal repressor of neuroendocrine differentiation (NED), we conducted a siRNA screening targeting 147 REST-repressing long non-coding RNAs (lncRNAs) and identified prostate cancer transcript-neuroendocrine 1 (PCAT-NE1) as a novel lncRNA that induces NED through activating autophagy signaling, crucial for NED of prostate adenocarcinoma cell. Analyses of clinical data and samples indicate that PCAT-NE1 is elevated in NEPC. Through gain- and loss-of-function experiments, we find that PCAT-NE1 promotes NED. Mechanistically, PCAT-NE1 acts as a competing endogenous RNA (ceRNA) that sponge hsa-miR-6889-3p, leading to the up-regulation of autophagy-related gene VPS13A and autophagy activation. These findings provide new insight into lncRNA-mediated mechanism for autophagy activation in NEPC and suggest PCAT-NE1 as a potential diagnostic biomarker and therapeutic target for NEPC.

No abstract

No abstract