Molecular mechanisms of TWIST1-regulated transcription in EMT and cancer metastasis.

TWIST1 induces epithelial-to-mesenchymal transition (EMT) to drive cancer metastasis. It is yet unclear what determines TWIST1 functions to activate or repress transcription. We found that the TWIST1 N-terminus antagonizes TWIST1-regulated gene expression, cancer growth and metastasis. TWIST1 interacts with both the NuRD complex and the NuA4/TIP60 complex (TIP60-Com) via its N-terminus. Non-acetylated TWIST1-K73/76 selectively interacts with and recruits NuRD to repress epithelial target gene transcription. Diacetylated TWIST1-acK73/76 binds BRD8, a component of TIP60-Com that also binds histone H4-acK5/8, to recruit TIP60-Com to activate mesenchymal target genes and MYC. Knockdown of BRD8 abolishes TWIST1 and TIP60-Com interaction and TIP60-Com recruitment to TWIST1-activated genes, resulting in decreasing TWIST1-activated target gene expression and cancer metastasis. Both TWIST1/NuRD and TWIST1/TIP60-Com complexes are required for TWIST1 to promote EMT, proliferation, and metastasis at full capacity. Therefore, the diacetylation status of TWIST1-K73/76 dictates whether TWIST1 interacts either with NuRD to repress epithelial genes, or with TIP60-Com to activate mesenchymal genes and MYC. Since BRD8 is essential for TWIST1-acK73/76 and TIP60-Com interaction, targeting BRD8 could be a means to inhibit TWIST1-activated gene expression.

Steroid receptor coactivator 1 promotes human hepatocellular carcinoma invasiveness through enhancing MMP-9.

SRC-1 functions as a transcriptional coactivator for steroid receptors and various transcriptional factors. Notably, SRC-1 has been implicated in oncogenic roles in multiple cancers, including breast cancer and prostate cancer. Previous investigations from our laboratory have established the high expression of SRC-1 in human HCC specimens, where it accelerates HCC progression by enhancing Wnt/beta-catenin signalling. In this study, we uncover a previously unknown role of SRC-1 in HCC metastasis. Our findings reveal that SRC-1 promotes HCC metastasis through the augmentation of MMP-9 expression. The knockdown of SRC-1 effectively mitigated HCC cell metastasis both in vitro and in vivo by suppressing MMP-9 expression. Furthermore, we observed a positive correlation between SRC-1 mRNA levels and MMP-9 mRNA levels in limited and larger cohorts of HCC specimens from GEO database. Mechanistically, SRC-1 operates as a coactivator for NF-κB and AP-1, enhancing MMP-9 promoter activity in HCC cells. Higher levels of SRC-1 and MMP-9 expression are associated with worse overall survival in HCC patients. Treatment with Bufalin, known to inhibit SRC-1 expression, significantly decreased MMP-9 expression and inhibited HCC metastasis in both in vitro and in vivo settings. Our results demonstrated the pivotal role of SRC-1 as a critical modulator in HCC metastasis, presenting a potential therapeutic target for HCC intervention.

Cell lineage tracing links ERα loss in Erbb2-positive breast cancers to the arising of a highly aggressive breast cancer subtype.

HER2-positive (HER2+) breast cancers (BrCs) contain approximately equal numbers of ERα+HER2+ and ERα-HER2+ cases. An enduring obstacle is the unclear cell lineage-related characteristics of these BrCs. Although ERα+HER2+ BrCs could lose ERα to become ERα-HER2+ BrCs, direct evidence is missing. To investigate ERα dependencies and their implications during BrC growth and metastasis, we generated ERαCreRFP-T mice that produce an RFP-marked ERα+ mammary gland epithelial cell (MGEC) lineage. RCAS virus-mediated expression of Erbb2, a rodent Her2 homolog, first produced comparable numbers of ERα+RFP+Erbb2+ and ERα-RFP-Erbb2+ MGECs. Early hyperplasia developed mostly from ERα+RFP+Erbb2+ cells and ERα-RFP-Erbb2+ cells in these lesions were rare. The subsequently developed ductal carcinomas in situ had 64% slow-proliferating ERα+RFP+Erbb2+ cells, 15% fast-proliferating ERα-RFP+Erbb2+ cells derived from ERα+RFP+Erbb2+ cells, and 20% fast-proliferating ERα-RFP-Erbb2+ cells. The advanced tumors had mostly ERα-RFP+Erbb2+ and ERα-RFP-Erbb2+ cells and only a very small population of ERα+RFP+Erbb2+ cells. In ERα-RFP+Erbb2+ cells, GATA3 and FoxA1 decreased expression and ERα promoter regions became methylated, consistent with the loss of ERα expression. Lung metastases consisted of mostly ERα-RFP+Erbb2+ cells, a few ERα-RFP-Erbb2+ cells, and no ERα+RFP+Erbb2+ cells. The high metastatic capacity of ERα-RFP+Erbb2+ cells was associated with ERK1/2 activation. These results show that the slow-proliferating, nonmetastatic ERα+RFP+Erbb2+ cells progressively lose ERα during tumorigenesis to become fast-proliferating, highly metastatic ERα-RFP+Erbb2+ cells. The ERα-Erbb2+ BrCs with an ERα+ origin are more aggressive than those ERα-Erbb2+ BrCs with an ERα- origin, and thus, they should be distinguished and treated differently in the future.

Long intergenic non-coding RNA Linc00485 promotes lung cancer progression by modulating miR-298/c-Myc axis.

Long non-coding RNAs (lncRNAs), which are non-protein-coding transcripts, are emerging as novel biomarkers for cancer diagnosis. Their dysregulation is increasingly recognized to contribute to the development and progression of human cancers, including lung cancer. Linc00485 is a newly discovered cancer-related lncRNA; however, little is known about its role in lung cancer progression. In this study, we found that the expression of Linc00485 was significantly increased in human lung cancer tissue and associated with malignant phenotypes, including tumour-node-metastasis (TNM) stage, metastasis and relapse. Furthermore, the proliferative, migratory and invasive abilities of lung cancer cells in vitro were significantly enhanced by overexpression of Linc00485 but inhibited by its silencing. Mechanistically, Linc00485 regulated the expression of c-Myc by directly binding to miR-298; the effects of Linc00485 overexpression could be significantly reversed by a c-Myc inhibitor or small interfering RNA. Xenotransplantation experiments showed that Linc00485 silencing significantly weakened the proliferation potential of A549 cells in vivo. Overall, these findings indicate that Linc00485 overexpression down-regulates miR-298, resulting in the up-regulation of c-Myc and thereby promoting the development of lung cancer.

The transcriptional co-activator NCOA6 promotes estrogen-induced GREB1 transcription by recruiting ERα and enhancing enhancer-promoter interactions.

Estrogen and its cognate receptor, ERα, regulate cell proliferation, differentiation, and carcinogenesis in the endometrium by controlling gene transcription. ERα requires co-activators to mediate transcription via mechanisms that are largely uncharacterized. Herein, using growth-regulating estrogen receptor binding 1 (GREB1) as an ERα target gene in Ishikawa cells, we demonstrate that nuclear receptor co-activator 6 (NCOA6) is essential for estradiol (E2)/ERα-activated GREB1 transcription. We found that NCOA6 associates with the GREB1 promoter and enhancer in an E2-independent manner and that NCOA6 knockout reduces chromatin looping, enhancer-promoter interactions, and basal GREB1 expression in the absence of E2. In the presence of E2, ERα bound the GREB1 enhancer and also associated with its promoter, and p300, myeloid/lymphoid or mixed-lineage leukemia protein 4 (MLL4), and RNA polymerase II were recruited to the GREB1 enhancer and promoter. Consequently, the levels of the histone modifications H3K4me1/3, H3K9ac, and H3K27ac were significantly increased; enhancer and promoter regions were transcribed; and GREB1 mRNA was robustly transcribed. NCOA6 knockout reduced ERα recruitment and abolished all of the aforementioned E2-induced events, making GREB1 completely insensitive to E2 induction. We also found that GREB1-deficient Ishikawa cells are much more resistant to chemotherapy and that human endometrial cancers with low GREB1 expression predict poor overall survival. These results indicate that NCOA6 has an essential role in ERα-mediated transcription by increasing enhancer-promoter interactions through chromatin looping and by recruiting RNA polymerase II and the histone-code modifiers p300 and MLL4. Moreover, GREB1 loss may predict chemoresistance of endometrial cancer.

Steroid Receptor Coactivator 3 Contributes to Host Defense against Enteric Bacteria by Recruiting Neutrophils via Upregulation of CXCL2 Expression.

Steroid receptor coactivator 3 (SRC-3) is a transcriptional coactivator that interacts with nuclear receptors and some other transcription factors to enhance their effects on target gene transcription. We reported previously that SRC-3-deficient (SRC-3-/-) mice are extremely susceptible to Escherichia coli-induced septic peritonitis as a result of uncontrolled inflammation and a defect in bacterial clearance. In this study, we observed significant upregulation of SRC-3 in colonic epithelial cells in response to Citrobacter rodentium infection. Based on these findings, we hypothesized that SRC-3 is involved in host defense against attaching and effacing bacterial infection. We compared the responses of SRC-3-/- and wild-type mice to intestinal C. rodentium infection. We found that SRC-3-/- mice exhibited delayed clearance of C. rodentium and more severe tissue pathology after oral infection with C. rodentium compared with wild-type mice. SRC-3-/- mice expressed normal antimicrobial peptides in the colons but exhibited delayed recruitment of neutrophils into the colonic mucosa. Accordingly, SRC-3-/- mice showed a delayed induction of CXCL2 and CXCL5 in colonic epithelial cells, which are responsible for neutrophil recruitment. At the molecular level, we found that SRC-3 can activate the NF-κB signaling pathway to promote CXCL2 expression at the transcriptional level. Collectively, we show that SRC-3 contributes to host defense against enteric bacteria, at least in part via upregulating CXCL2 expression to recruit neutrophils.

Steroid Receptor Coactivator 1 Promotes Human Hepatocellular Carcinoma Progression by Enhancing Wnt/ß-Catenin Signaling.

Steroid receptor coactivator 1 (SRC-1) is a transcriptional coactivator not only for steroid receptors, such as androgen receptor and estrogen receptor, but also for other transcription factors. SRC-1 has been shown to play an important role in the progression of breast cancer and prostate cancer. However, its role in liver cancer progression remains unknown. In this study, we report that SRC-1 was overexpressed in 25 (62.5%) of 40 human hepatocellular carcinoma (HCC) specimens. Down-regulation of SRC-1 decreased HCC cell proliferation and impaired tumor maintenance in HCC xenografts. Knockdown of SRC-1 reduced protein levels of the proliferation marker proliferating cell nuclear antigen (PCNA) and the oncogene c-Myc. Knockout of SRC-1 in mice reduced diethylnitrosamine/CCl4-induced tumor formation in the liver and the expression of c-Myc and PCNA in liver tumors. SRC-1 promoted c-Myc expression, at least in part, by directly interacting with ß-catenin to enhance Wnt/ß-catenin signaling. Consistent with these results, the expression of SRC-1 was positively correlated with PCNA expression in human HCC specimens, and the expression levels of c-Myc in SRC-1-positive HCC specimens were higher than in SRC-1-negative HCC specimens. In addition, SRC-1 and SRC-3 were co-overexpressed in 47.5% of HCC specimens, and they cooperated to promote HCC cell proliferation. Simultaneous down-regulation of SRC-1 and SRC-3 dramatically inhibited HCC cell proliferation. Our results demonstrate that SRC-1 promotes HCC progression by enhancing Wnt/ß-catenin signaling and suggest that SRC-1 is a potential therapeutic molecular target for HCC.

Hepatitis B virus X protein stabilizes amplified in breast cancer 1 protein and cooperates with it to promote human hepatocellular carcinoma cell invasiveness.

UNLABELLED: Chronic infection of hepatitis B virus (HBV) is closely associated with the development of human hepatocellular carcinoma (HCC). HBV X protein (HBx) plays a key role in the progression of HCC. We recently found that amplified in breast cancer 1 (AIB1) protein is overexpressed in 68% of human HCC specimens and promotes HCC progression by enhancing cell proliferation and invasiveness. Given that both HBx and AIB1 play important oncogenic roles in HCC, we aimed to determine whether they could cooperatively promote human HCC development. Herein, we show that HBx-positive HCC tissues had a higher level of AIB1 protein, compared to HBx-negative HCC tissues. A positive correlation between HBx protein level and AIB1 protein level was established in HCC specimens. Without affecting its messenger RNA level, HBx induced a significant increase of the protein level of AIB1, which correlated with a significant extension of the half-life of AIB1 protein. Mechanistically, HBx could interact with AIB1 to prevent the interaction between envelope protein 3 ubiquitin ligase F-box and WD repeat domain containing 7 (Fbw7)α and AIB1, then inhibited the Fbw7α-mediated ubiquitination and degradation of AIB1. In addition, reporter assays and chromatin immunoprecipitation assays revealed that both HBx and AIB1 were recruited to matrix metalloproteinase-9 (MMP-9) promoter to enhance MMP-9 promoter activity cooperatively. Consistently, HBx and AIB1 cooperatively enhanced MMP-9 expression in HepG2 cells, which, in turn, increased cell-invasive ability. CONCLUSION: Our study demonstrates that HBx can stabilize AIB1 protein and cooperate with it to promote human HCC cell invasiveness, highlighting the essential role of the cross-talk between HBx and AIB1 in HBV-related HCC progression.

PolyC-RNA-binding protein 1 (PCBP1) enhances tropomyosin 3 (TPM3) mRNA stability to promote the progression of esophageal squamous cell carcinoma.

The molecular etiology of esophageal squamous cell carcinoma (ESCC) has not been fully elucidated. Understanding the molecular mechanisms and finding new therapeutic targets for ESCC are of crucial importance. PolyC-RNA-binding protein 1 (PCBP1) is an RNA-binding protein. Here, we found overexpressed PCBP1 in esophageal cancer tissues by quantitative polymerase chain reaction (qPCR) and western blotting analysis. PCBP1 knockdown significantly attenuated migratory and invasion abilities of ESCC cells. Mechanistically, PCBP1 bound directly to tropomyosin 3 (TPM3) mRNA, which was verified by RNA-protein immunoprecipitation (RIP) assay. PCBP1 knockdown markedly reduced messenger RNA (mRNA) levels of TPM3. After inhibiting intracellular mRNA synthesis with actinomycin D (ActD), it was found that PCBP1 knockdown contributed to a significant decrease in TPM3 mRNA degradation. Furthermore, PCBP1 promoted migration and invasion of EC cells by directly binding to the 3'UTR of TPM3 mRNA, increasing TPM3 mRNA stability. Taken together, PCBP1 acting as a pro-oncogenic factor enhances TPM3 mRNA stability by directly binding to the 3'UTR of TPM3 mRNA in esophageal squamous cell carcinoma. Our findings provide a new perspective for understanding the molecular mechanism of esophageal carcinogenesis, and PCBP1 is a promising therapeutic target.

Nuclear receptor coactivator SRC-1 promotes colorectal cancer progression through enhancing GLI2-mediated Hedgehog signaling.

Overexpression of nuclear coactivator steroid receptor coactivator 1 (SRC-1) and aberrant activation of the Hedgehog (Hh) signaling pathway are associated with various tumorigenesis; however, the significance of SRC-1 in colorectal cancer (CRC) and its contribution to the activation of Hh signaling are unclear. Here, we identified a conserved Hh signaling signature positively correlated with SRC-1 expression in CRC based on TCGA database; SRC-1 deficiency significantly inhibited the proliferation, survival, migration, invasion, and tumorigenesis of both human and mouse CRC cells, and SRC-1 knockout significantly suppressed azoxymethane/dextran sodium sulfate (AOM/DSS)-induced CRC in mice. Mechanistically, SRC-1 promoted the expression of GLI family zinc finger 2 (GLI2), a major downstream transcription factor of Hh pathway, and cooperated with GLI2 to enhance multiple Hh-regulated oncogene expression, including Cyclin D1, Bcl-2, and Slug. Pharmacological blockages of SRC-1 and Hh signaling retarded CRC progression in human CRC cell xenograft mouse model. Together, our studies uncover an SRC-1/GLI2-regulated Hh signaling looping axis that promotes CRC tumorigenesis, offering an attractive strategy for CRC treatment.

Immunotherapy vs platinum for advanced or metastatic thymic carcinoma: A protocol for systematic review and meta analysis.

BACKGROUND: Thymic carcinoma is a rare malignancy, and platinum-based chemotherapy has not previously been established as a standard treatment for advanced or metastatic thymic carcinoma. With the breakthrough and progress of immunotherapy, the possibility of curing thymic carcinoma has greatly increased. Some clinical trials have reported that compared with traditional platinum-based chemotherapy, the use of programmed death 1 and programmed death ligand 1 inhibitors alone can benefit patients and effectively prolong their overall survival. We compare the efficacy of single immunotherapy with traditional platinum-based chemotherapy in a systematic review and meta-analysis to provide a reliable basis for clinicians. METHODS: Pubmed (Medline), Web of Science, Embase, Cochrane Central Register of Controlled Trials, and Google Scholar will be searched for relevant randomised controlled trials, quasi- randomised controlled trials, and Hi-Q(high quality) prospective cohort trials published or unpublished in any language before March 1, 2021. Subgroup analysis will be performed in tumor pathological stage and ethnicity. INPLASY registration number: INPLASY2020110060. RESULTS: The results of this study will be published in a peer-reviewed journal. CONCLUSION: The results of this systematic review and meta-analysis will provide a basis for clinicians to formulate the best chemotherapy regimen for patients, as well as a research clue for clinical researchers in this field. The results of this study will expand the treatment options for thymic carcinoma, but due to the nature of the disease and intervention, large sample clinical trials are not abundant, so we will include some high-quality small sample trials, which may cause high heterogeneity. INPLASY REGISTRATION NUMBER: INPLASY2020110060.

Artery-first vs vein-first surgical technique for segmentectomy of non-small cell lung cancer: A protocol for systematic review and meta-analysis.

BACKGROUND: Surgery for lung cancer squeezes the tumor, further promoting the circulation of tumor cells, which may be one of the reasons for lung cancer metastasis and recurrence. In theory, the potential risk of tumor cell proliferation can be minimized if the outflow veins are ligated first (via veins first [V-first]) rather than arteries first (via arteries first [A-first]). However, due to the lack of sufficient evidence, this technical concept has not been widely accepted as a standard in surgical oncology in the current guidelines. This systematic review and meta-analysis will be used to determine which techniques will yield longer patient survival and benefit patients during segmentectomy. METHODS: We will search PubMed, Web of Science, Embase, Cancerlit, the Cochrane Central Register of Controlled Trials, and Google Scholar databases for relevant clinical trials published in any language before January 1, 2021. Randomized controlled trials (RCTs), quasi-RCTs, propensity score-matched comparative studies, and prospective cohort studies of interest, published or unpublished, that meet the inclusion criteria will be included. Subgroup analysis of the type of operation, tumor pathological stage, and ethnicity will be performed. RESULTS: The results of this study will be published in a peer-reviewed journal. CONCLUSION: As far as we know, this study will be the first meta-analysis to compare the efficacy of the vein-first and artery-first surgical technique of segmentectomy for patients diagnosed with resectable non-small cell lung cancer. Due to the nature of the disease and intervention methods, RCTs may be inadequate, and we will carefully consider inclusion in high-quality, non-RCTs, but this may result in high heterogeneity and affect the reliability of the results.INPLASY registration number: INPLASY202080062.

Platinum versus immunotherapy for unresectable esophageal cancer: A protocol for systematic review and meta analysis.

BACKGROUND: Esophageal cancer is one of the most common malignant tumors, with early metastasis, highly malignant characteristics. Morbidity ranks 7th among all malignant tumors, and mortality ranks 6th. Esophageal adjuvant therapy can significantly improve overall survival in unresectable esophageal cancer patients. With the breakthrough and progress of immunotherapy, the possibility of curing esophageal cancer has greatly increased. Some clinical trials have reported that compared with traditional platinum-based chemotherapy, the use of programmed death 1 (PD-1) and programmed death ligand 1 (PD-L1) inhibitors alone can benefit patients and effectively prolong their overall survival. We compare the efficacy of single immunotherapy with traditional platinum-based chemotherapy in a systematic review and meta-analysis to provide a reliable basis for clinicians. METHODS: We will search PubMed, Medline, Embase, Web of Science, Cancerlit, Google Scholar, and the Cochrane Central Register of Controlled Trials for related studies published before December 1, 2019 without language restrictions. Two review authors will search and assess relevant studies independently. Randomized controlled trials (RCTs) or quasi-RCTs, and prospective cohort studies will be included. We will perform subgroup analysis in sex, age, ethnicity, and tumor stage of esophageal cancer patients. RESULTS: The results of this study will be published in a peer-reviewed journal. CONCLUSION: The results of this systematic review and meta-analysis will provide a basis for clinicians to formulate the best chemotherapy regimen for patients, as well as a research clue for clinical researchers in this field. The results of this study will expand the treatment options for esophageal patients, but due to the nature of the disease and intervention, large sample clinical trials are not abundant, so we will include some high-quality small sample trials, which may cause high heterogeneity. INPLASY REGISTRATION NUMBER: INPLASY2020110012.

Platinum versus immunotherapy for early resectable non-small cell lung cancer: A protocol for systematic review and meta analysis.

BACKGROUND: Lung cancer is one of the most common malignant tumors. Non-small cell Lung cancer (NSCLC) accounts for about 85% of the total lung cancer. For patients with resectable early NSCLC, conventional postoperative adjuvant therapy can significantly prolong the overall survival of patients and reduce the risk of tumor recurrence. With the emergence and maturity of molecular targeted therapy and immunotherapy, the strategy of postoperative chemotherapy for lung cancer patients has changed greatly. To evaluate the efficacy of postoperative chemotherapy (platinum based chemotherapy and immunotherapy) with or without radiotherapy for NSCLC patients, we will conduct a systematic review and meta-analysis of published or unpublished randomized controlled trials. METHODS: We will search Pubmed (Medline), Embase, Google Scholar, Cancerlit, and the Cochrane Central Register of Controlled Trials for related studies published without language restrictions before June 20, 2021. Two review authors will search and assess relevant studies independently. Randomized controlled trials and quasi-randomized controlled trials studies will be included. we will perform subgroup analysis in different methods of postoperative adjuvant therapy for patients with resectable early NSCLC. Because this study will be based on published or unpublished records and studies, there is no need for ethics approval. INPLASY registration number: INPLASY202080064. RESULTS: The results of this study will be published in a peer-reviewed journal. CONCLUSION: This study will compare the efficacy of platinum chemotherapy and immunotherapy in patients with resectable early NSCLC. Since the large sample randomized trials that meet the inclusion criteria of this study may be inadequate, we will consider incorporating some high quality small sample related tests, which may lead to heterogeneity and affect the reliability of the results.

Application of neck anastomotic muscle flap embedded in 3-incision radical resection of oesophageal carcinoma: A protocol for systematic review and meta analysis.

BACKGROUND: Oesophageal cancer is one of the most common malignant tumors and has been identified as one of the leading causes of cancer death worldwide. Surgery is considered to be the optimal treatment for patients with resectable oesophageal cancer. Oesophagectomy for oesophageal cancer can significantly extend the survival period of patients and provide a potential opportunity for a cure. However, there is still controversy regarding application of neck anastomotic muscle flap embedded. This systematic review and meta-analysis will be performed to determine whether the application of neck anastomotic muscle flap embedded would benefit patients more. METHODS: We will search PubMed, Web of Science, Embase, Cancerlit, the Cochrane Central Register of Controlled Trials, and Google Scholar databases for relevant clinical trials published in any language before October 1, 2020. Randomized controlled trials (RCTs), quasi-RCTs, propensity score-matched comparative studies, and prospective cohort studies of interest, published or unpublished, that meet the inclusion criteria will be included. Subgroup analysis of the type of operation, tumor pathological stage, and ethnicity will be performed. INPLASY registration number: INPLASY202080059. RESULTS: The results of this study will be published in a peer-reviewed journal. CONCLUSION: As far as we know, this study will be the first meta-analysis to compare the efficacy of the application of neck anastomotic muscle flap embedded in 3-incision radical resection of oesophageal carcinoma. Due to the nature of the disease and intervention methods, RCTs may be inadequate, and we will carefully consider inclusion in high-quality, non-RCTs, but this may result in high heterogeneity and affect the reliability of the results.

Histone acetyl transferase GCN5 promotes human hepatocellular carcinoma progression by enhancing AIB1 expression.

BACKGROUND: General control non-depressible 5 (GCN5) is a crucial catalytic component of a transcriptional regulatory complex that plays important roles in cellular functions from cell cycle regulation to DNA damage repair. Although GCN5 has recently been implicated in certain oncogenic roles, its role in liver cancer progression remains vague. RESULTS: In this study, we report that GCN5 was overexpressed in 17 (54.8 %) of 31 human hepatocellular carcinoma (HCC) specimens. Down-regulation of GCN5 inhibited HCC cell proliferation and xenograft tumor formation. GCN5 knockdown decreased the protein levels of the proliferation marker proliferating cell nuclear antigen (PCNA) and amplified in breast cancer 1 (AIB1), but increased the protein levels of cell cycle inhibitor p21(Cip1/Waf1) in HepG2 cells. GCN5 regulated AIB1 expression, at least in part, by cooperating with E2F1 to enhance AIB1 transcription. Consistently, GCN5 expression was positively correlated with AIB1 expression in human HCC specimens in two GEO profile datasets. CONCLUSION: Since AIB1 plays a promoting role in HCC progression, our results propose that GCN5 promotes HCC progression at least partially by regulating AIB1 expression. This study implicates that GCN5 might be a potential molecular target for HCC diagnosis and treatment.

Downregulation of amplified in breast cancer 1 contributes to the anti-tumor effects of sorafenib on human hepatocellular carcinoma.

Multi-kinase inhibitor sorafenib represents a major breakthrough in the therapy of advanced hepatocellular carcinoma (HCC). Amplified in breast cancer 1 (AIB1) is frequently overexpressed in human HCC tissues and promotes HCC progression. In this study, we investigated the effects of sorafenib on AIB1 expression and the role of AIB1 in anti-tumor effects of sorafenib. We found that sorafenib downregulated AIB1 protein expression by inhibiting AIB1 mRNA translation through simultaneously blocking eIF4E and mTOR/p70S6K/RP-S6 signaling. Knockdown of AIB1 significantly promoted sorafenib-induced cell death, whereas overexpression of AIB1 substantially diminished sorafenib-induced cell death. Downregulation of AIB1 contributed to sorafenib-induced cell death at least in part through upregulating the levels of reactive oxygen species in HCC cells. In addition, resistance to sorafenib-induced downregulation of AIB1 protein contributes to the acquired resistance of HCC cells to sorafenib-induced cell death. Collectively, our study implicates that AIB1 is a molecular target of sorafenib and downregulation of AIB1 contributes to the anti-tumor effects of sorafenib.

Amplified in breast cancer 1 promotes colorectal cancer progression through enhancing notch signaling.

Aberrant activation of Notch signaling has an essential role in colorectal cancer (CRC) progression. Amplified in breast cancer 1 (AIB1), also known as steroid receptor coactivator 3 or NCOA3, is a transcriptional coactivator that promotes cancer cell proliferation and invasiveness. However, AIB1 implication in CRC progression through enhancing Notch signaling is unknown. In this study, we found that several CRC cell lines expressed high levels of AIB1, and knockdown of AIB1 decreased cell proliferation, colony formation and tumorigenesis of these CRC cells. Specifically, knockdown of AIB1 inhibited cell cycle progression at G1 phase by decreasing the mRNA levels of cyclin A2, cyclin B1, cyclin E2 and hairy and enhancer of split (Hes) 1. Furthermore, AIB1 interacted with Notch intracellular domain and Mastermind-like 1 and was recruited to the Hes1 promoter to enhance Notch signaling. Downregulation of AIB1 also decreased CRC cell invasiveness in vitro and lung metastasis in vivo. Besides that, knockout of AIB1 in mice inhibited colon carcinogenesis induced by azoxymethane/dextran sodium sulfate treatment. The mRNA levels of cyclin B1 and Hes5 were downregulated, but p27, ATOH1 and MUC2 were upregulated in the colon tumors from AIB1-deficient mice compared with those from wild-type mice. Thus, our results signify the importance of AIB1 in CRC and demonstrate that AIB1 promotes CRC progression at least in part through enhancing Notch signaling, suggesting that AIB1 is a potential molecular target for CRC treatment.