Guo, Lixia

It is well established that many tumor types possess defective autophagic pathways. Several studies have reported that the transmembrane, autophagic lipid scramblase ATG9B is altered in multiple cancers, suggesting that this dysregulation could contribute to oncogenesis. Therefore, the goal of this study was to define the cellular distribution of ATG9B in two different tumor cell types and to provide insights into its cellular function. Surprisingly, we found that ATG9B shows a modest association with autophagic structures and exhibits a unique and prominent localization to mitochondria, in contrast to its related form ATG9A. Upon expression of tagged ATG9B forms, this mitochondrial distribution was accompanied by aberrant changes in mitochondrial morphology as well as a reduction in the mitochondrial membrane potential and the release of mtDNA. Few indicators for ATG9B-dependent mitophagy were noted. Instead, ATG9B overexpression led to pronounced apoptotic cell death as assessed by a variety of indicators. Further, we find that the N-terminal sequence of ATG9B acts as a mitochondrial targeting domain and that expression of this peptide alone can induce apoptotic cell death. These findings provide new insights into a putative cellular localization and function for ATG9B.

AbstractNOTCH1 is the prototype of the NOTCH family of single‐pass transmembrane receptors and regulates many basic processes during embryonic development and human pathogenesis. In core to NOTCH1 activation are proteolytic cleavages that release its intracellular domain (NICD1), which in turn translocates to the nucleus to regulate gene transcription. Macroautophagy (hereafter autophagy) has been shown to promote the degradation of NOTCH1, but the underlying mechanisms remain elusive. Here, we show that autophagy promotes the degradation of NOTCH1 by p62‐dependent binding between NICD1 and LC3, a component of the autophagosomes that execute autophagy. Strikingly, deleting any of the structural NICD1 domains fails to block the degradation of NICD1 by autophagy, and p62 binds to almost all these domains independently, indicating that p62 binds to multiple sites on NICD1 to promote its degradation. Intriguingly, inhibition of autophagy induces the accumulation of NICD1 in not only the cytoplasm but also the nucleus and increases the transcriptional activity of NICD1, and such regulation of nuclear NICD1 by autophagy is unique to NICD1 and not observed for all other NICDs (NICD2‐4). Collectively, our results suggest that autophagy tightly controls nuclear NOTCH1 activity through multiple p62 binding sites, and that modulating autophagy activity may be useful for treating NOTCH1 related human diseases. © 2018 IUBMB Life, 70(10):985–994, 2018

Abstract Lung cancer remains the leading cause of cancer-related death, partly due to the fact that most patients are diagnosed with metastatic disease, which is the main cause of death, yet effective therapeutics are lacking. Utilizing mouse models of metastatic lung adenocarcinomas, we report that the transcription factor GATA3 and its cofactor FOG2 play critical roles in lung adenocarcinoma metastasis by promoting the expression of the lysyl hydroxylase (LH) family members, which in turn regulate the tumorigenicity and motility of lung tumor cells through both EMT and EMT-independent mechanisms. In vivo, LHs are elevated in human lung adenocarcinomas and are associated with worse patient survival. Collectively, our data suggest that targeting LHs may be useful for treating metastatic lung cancer. Citation Format: Wei Liu, Ting Zhang, Lixia Guo, Yuanyuan Wang, Yanan Yang. Role of lysyl hydroxylases in metastatic lung cancer [abstract]. In: Proceedings of the AACR Special Conference: Advances in Modeling Cancer in Mice: Technology, Biology, and Beyond; 2017 Sep 24-27; Orlando, Florida. Philadelphia (PA): AACR; Cancer Res 2018;78(10 Suppl):Abstract nr B07.

Lung cancer is one of the most common types of human malignancies and the leading cause of cancer-related death. Patients with surgically resectable early stage lung cancer are more likely curable, but currently only a small population of patients can be diagnosed at such a stage, partly due to our incomplete understanding of the biology of lung cancer and the lack of diagnostic and prognostic biomarkers. Recent studies have shown that NOTCH1 is a critical regulator of human carcinogenesis and has been implicated in multiple steps of cancer development and progression. Herein, we review recent findings about the role of NOTCH1 in lung cancer and discuss its potential usefulness as both a therapeutic target and a biomarker for lung cancer.

AbstractMicroRNA‐200 (miR‐200) has emerged as a regulator of the PI3K/AKT pathway and cancer cell growth. It was reported that miR‐200 can activate PI3K/AKT by targeting FOG2 (friend of GATA 2), which directly binds to the p85α regulatory subunit of PI3K. We found that miR‐200 was elevated in early stage lung adenocarcinomas when compared with normal lung tissues, and the expression of miR‐200 promoted the tumor spheroid growth of lung adenocarcinoma cells. We show that AKT activation was essential for such oncogenic action of miR‐200. However, depletion of FOG2 had little effect on AKT activation. By performing a reverse‐phase protein array, we found that miR‐200 not only activated AKT but also concomitantly inactivated S6K and increased IRS‐1, an S6K substrate that is increased on S6K inactivation. Depletion of IRS‐1 partially inhibited the miR‐200‐dependent AKT activation. Taken together, our results suggest that miR‐200 may activate AKT in lung adenocarcinoma cells through a FOG2‐independent mechanism involving IRS‐1. Our findings also provide evidence that increased miR‐200 expression may contribute to early lung tumorigenesis and that AKT inhibitors may be useful for the treatment of miR‐200‐dependent tumor cell growth. © 2015 IUBMB Life, 67(9):720–725, 2015

Significance Our study not only reveals a novel role of peroxisome proliferator-activated receptor δ (PPARδ) in colonic inflammation and colitis-associated tumorigenesis, but also provides some rationale for development of PPARδ antagonists as new therapeutic agents in the treatment of inflammatory bowel disease and colitis-associated colorectal cancer. Moreover, our findings indicate that prostaglandin E 2 generated by chronic inflammation is a crucial mediator connecting chronic inflammation and colorectal carcinogenesis.