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Breast cancer is often treated with chemotherapy. However, the development of chemoresistance results in treatment failure. Long non‐coding RNA nuclear paraspeckle assembly transcript 1 (NEAT1) has been shown to contribute to chemoresistance in breast cancer cells. In studying the transcriptional regulation of NEAT1 using multi‐omics approaches, we showed that NEAT1 is up‐regulated by 5‐fluorouracil in breast cancer cells with wild‐type cellular tumor antigen p53 but not in mutant‐p53‐expressing breast cancer cells. The regulation of NEAT1 involves mediator complex subunit 12 (MED12)‐mediated repression of histone acetylation marks at the promoter region of NEAT1. Knockdown of MED12 but not coactivator‐associated arginine methyltransferase 1 (CARM1) induced histone acetylation at the NEAT1 promoter, leading to elevated NEAT1 mRNAs, resulting in a chemoresistant phenotype. The MED12‐dependent regulation of NEAT1 differs between wild‐type and mutant p53‐expressing cells. MED12 depletion led to increased expression of NEAT1 in a wild‐type p53 cell line, but decreased expression in a mutant p53 cell line. Chemoresistance caused by MED12 depletion can be partially rescued by NEAT1 knockdown in p53 wild‐type cells. Collectively, our study reveals a novel mechanism of chemoresistance dependent on MED12 transcriptional regulation of NEAT1 in p53 wild‐type breast cancer cells. [ABSTRACT FROM AUTHOR]

The pyruvate kinase M2 isoform (PKM2) is preferentially expressed in cancer cells to regulate anabolic metabolism. Although PKM2 was recently reported to regulate lipid homeostasis, the molecular mechanism remains unclear. Herein, we discovered an ER transmembrane protein 33 (TMEM33) as a downstream effector of PKM2 that regulates activation of SREBPs and lipid metabolism. Loss of PKM2 leads to up‐regulation of TMEM33, which recruits RNF5, an E3 ligase, to promote SREBP‐cleavage activating protein (SCAP) degradation. TMEM33 is transcriptionally regulated by nuclear factor erythroid 2‐like 1 (NRF1), whose cleavage and activation are controlled by PKM2 levels. Total plasma cholesterol levels are elevated by either treatment with PKM2 tetramer‐promoting agent TEPP‐46 or by global PKM2 knockout in mice, highlighting the essential function of PKM2 in lipid metabolism. Although depletion of PKM2 decreases cancer cell growth, global PKM2 knockout accelerates allografted tumor growth. Together, our findings reveal the cell‐autonomous and systemic effects of PKM2 in lipid homeostasis and carcinogenesis, as well as TMEM33 as a bona fide regulator of lipid metabolism. SYNOPSIS: This study identifies the endoplasmic reticulum (ER) transmembrane protein TMEM33 as a new mechanistic target of pyruvate kinase M2 (PKM2) and bona fide regulator of lipid metabolism. These findings have implications for cancer caused by elevated plasma cholesterol levels and underscore systemic functions of PKM2, opening up new avenues for therapeutic interventions. PKM2 down‐regulates TMEM33 expression in MEFs and breast cancer cells, derepressing the lipogenic transcription factor SREBP.TMEM33 is transcriptionally regulated by NRF1, whose activation depends on the PKM2/VCP axis.PKM2 loss induces TMEM33, leading it to recruit E3 ligase RNF5 for ubiquitination and degradation of SREBP‐cleavage factor SCAP.Depletion of PKM2 in mice elevates global cholesterol levels and promotes allografted growth of hepatocellular cancer. [ABSTRACT FROM AUTHOR]

Under pathological conditions, the Janus kinase (JAK)/STAT signaling pathway can regulate the proliferation, differentiation and migration of tumor cells, including colorectal cancer (CRC). CRC is the third major types of cancer among males and the second among females worldwide. In China, CRC is the fifth common cancer among both males and females. Western blotting, flow cytometry, RNA interference, immunoprecipitation, xenografts models, and immunohistochemical staining were carried out to evaluate the possible mechanisms of acton of ruxolitinib. The present data suggested that ruxolitinib can suppress CRC cell proliferation by inducing apoptosis. Firstly, JAK1/2-STAT1 was identified as the target of ruxolitinib. Then, ruxolitinib downregulated myeloid cell leukemia-1 (Mcl-1) mRNA level and decreased its protein level, which enabled Bak to trigger CRC apoptosis. Furthermore, ruxolitinib exerted potent activity against CRC xenograft growth in vivo. High expression of phosphorylated STAT1 (S727) was also confirmed in 44 pairs of human colon carcinoma and adjacent normal tissues. Taken together, the results showed that ruxolitinib decreased JAK1/2-STAT1-Mcl-1 protein level and effectively suppressed CRC cell proliferation in vitro and in vivo. Therefore, ruxolitinib could be a promising anticancer agent for CRC treatment. [ABSTRACT FROM AUTHOR]

FK228 is a selective inhibitor of histone deacetylases that exhibits marked antitumor activity in cancer cells and xenograft models. However, the effect of FK228 on the global profile of histone lysine acetylation and the proteome of EC109 cells remains poorly understood. The present study aimed at analyzing histone lysine acetylation and identifying the proteomic changes in EC109 cells following treatment with FK228, using the stable isotope labelling by amino acids in cell culture technique and a high-sensitivity mass spectrometer. In total, 87 acetylation sites and 3,515 proteins revealed changes in response to FK228 treatment. Of the 87 acetylation sites, 25 were quantifiable and 19 were quantified with ratio of >1.3. Notably, no downregulated lysine acetylation (Kac) sites were quantified in the present study and the 62 unquantified Kac sites were only identified in the FK228-treated cells. Bioinformatic analysis revealed that these quantifiable proteins were primarily involved in multiple biological functions and metabolic pathways as well as in protein complexes. The results of the present study revealed the extensive lysine acetylome and proteome in EC109 cells and expanded upon the current understanding of the anticancer mechanism of FK228 in EC109 cells. [ABSTRACT FROM AUTHOR]

Background: Previously, we reported that high expression of nipped-B-like protein (NIPBL) was strongly correlated with poor prognosis, tumor differentiation, and lymph node metastasis. Survival analysis indicated that NIPBL expression was a potential prognostic factor for non-small cell lung cancer (NSCLC). Moreover, loss of NIPBL decreased lung cancer cells proliferation, migration, invasion and promoted apoptosis as well as sensitivity to chemotherapeutic agents. However, the deep mechanisms were not explored. Purpose: The objective of this study was to identify the role of NIPBL in DNA damage response, as well as autophagy pathway, so as to interpret the mechanisms of how NIPBL knockdown enhances the chemosensitivity of lung cancer cell. Methods: Cells (NCI-H1299 and NCI-H1650) were transfected by specific siRNAs before immunofluorescence and single-cell gel electrophoresis, which were mainly used to observe the differences of DNA damage in different groups. Additionally, protein were obtained and then analyzed by western blot and mass spectroscopy. Results: In this study, we found that knockdown of NIPBL resulted in accumulation of phosphorylated H2AX (γ-H2AX) foci and higher levels of DNA damage, as revealed by comet assay. Western blot assay revealed that loss of NIPBL decreased expression of ATM/ATR, Rad3-related protein and Ku70/Ku80, but increased expression of LC3-B and depletion of p62. Using mass spectroscopy, we identified eight proteins that were significantly differentially expressed upon NIPBL knockdown. Gene Ontology analysis revealed that these proteins are mainly involved in DNA repair, mismatch repair, and binding to damaged DNA. The expression changes in two of the proteins, MSH2 and STAT1, were verified by Western blotting in NIPBL-knockdown cells. Conclusions: In summary, these results reflected that loss of NIPBL impairs the DNA damage response and promotes autophagy. And NIPBL suppression may represent a novel strategy for preventing chemotherapy resistance in lung cancer. [ABSTRACT FROM AUTHOR]

Activation of hypoxia-inducible factor 1α (HIF1α) controls the transcription of genes governing angiogenesis under hypoxic condition during tumorigenesis. Here we show that hypoxia-responsive miR-182 is regulated by HIF1α at transcriptional level. Prolyl hydroxylase domain enzymes (PHD) and factor inhibiting HIF-1 (FIH1), negative regulators of HIF1 signaling, are direct targets of miR-182. Overexpression of miR-182 in prostate cancer cells led to a reduction of PHD2 and FIH1 expression and an increase in HIF1α level either under normoxic or hypoxic condition. Consistently, inhibition of miR-182 could increase PHD2 and FIH1 levels, thereby reducing the hypoxia-induced HIF1α expression. Matrigel plug assay showed that angiogenesis was increased by miR-182 overexpression, and vice versa. miR-182 overexpression in PC-3 prostate cancer xenografts decreased PHD2 and FIH1 expression, elevated HIF1α protein levels, and increased tumor size. Lastly, we revealed that the levels of both miR-182 and HIF1α were elevated, while the expression PHD2 and FIH1 was downregulated in a mouse model of prostate cancer. Together, our results suggest that the interplay between miR-182 and HIF1α could result in a sustained activation of HIF1α pathway, which might facilitate tumor cell adaption to hypoxic stress during prostate tumor progression. [ABSTRACT FROM AUTHOR]