An H3K4me3 reader, BAP18 as an adaptor of COMPASS-like core subunits co-activates ERα action and associates with the sensitivity of antiestrogen in breast cancer.

Estrogen receptor alpha (ERα) signaling pathway is essential for ERα-positive breast cancer progression and endocrine therapy resistance. Bromodomain PHD Finger Transcription Factor (BPTF) associated protein of 18kDa (BAP18) has been recognized as a crucial H3K4me3 reader. However, the whole genomic occupation of BAP18 and its biological function in breast cancer is still elusive. Here, we found that higher expression of BAP18 in ERα-positive breast cancer is positively correlated with poor prognosis. ChIP-seq analysis further demonstrated that the half estrogen response elements (EREs) and the CCCTC binding factor (CTCF) binding sites are the significant enrichment sites found in estrogen-induced BAP18 binding sites. Also, we provide the evidence to demonstrate that BAP18 as a novel co-activator of ERα is required for the recruitment of COMPASS-like core subunits to the cis-regulatory element of ERα target genes in breast cancer cells. BAP18 is recruited to the promoter regions of estrogen-induced genes, accompanied with the enrichment of the lysine 4-trimethylated histone H3 tail (H3K4me3) in the presence of E2. Furthermore, BAP18 promotes cell growth and associates the sensitivity of antiestrogen in ERα-positive breast cancer. Our data suggest that BAP18 facilitates the association between ERα and COMPASS-like core subunits, which might be an essential epigenetic therapeutic target for breast cancer.

ASH2L is involved in promotion of endometrial cancer progression via upregulation of PAX2 transcription.

Absent, small or homeotic 2-like protein (ASH2L) is a core component of a multimeric histone methyltransferase complex that is involved in the maintenance of active transcription, participating in several cancers, however the biological function and molecular mechanism of ASH2L in endometrial cancer (ECa) are largely unknown. Endometrial cancer is a common malignant tumor in women and the incidence of this cancer is on the rise. Estrogen-ERα signaling, as an oncogenic pathway, plays a crucial role in endometrial carcinogenesis. Therefore, further exploration of the molecular mechanisms around ERα-mediated gene transcription in ECa would be helpful to the understanding of tumor development and to finding a new therapeutic target for ECa. Here, our study demonstrated that ASH2L was highly expressed in ECa samples, and higher expression of ASH2L was positively correlated with a poor prognosis. Moreover, we identified that ASH2L associated with ERα and that knockdown of ASH2L resulted in decreased expression of a subset of the estrogen-induced target genes, including paired box 2 (PAX2), an oncogenic gene in ECa. ASH2L was recruited to cis-regulatory elements in PAX2, thereby altering histone H3K4me3 and H3K27me3 levels, to enhance ERα-mediated transactivation. Finally, depletion of ASH2L suppressed endometrial cancer cell proliferation and migration. Our findings suggest that ASH2L participates in the promotion of ECa progression, if not totally at least partially, via upregulation of PAX2 transcription.

Histone acetyltransferase MOF is involved in suppression of endometrial cancer and maintenance of ERα stability.

Histone acetyltransferase MOF is involved in active transcription regulation through histone H4K16 acetylation. MOF is downexpressed in a number of human tumors, but biological function of MOF in endometrial cancer has not been fully defined. The estrogen receptor α (ERα) is a transcription factor that regulates estrogen-stimulated cell proliferation in hormone-responsive tumors. However, ERα expression is decreased in grade III ECa samples and high expression of ERα is associated with long disease-free survival in ECa. The molecular mechanism for these observations is still unclear. Here we demonstrate knockdown of MOF promotes ECa cell growth and proliferation in vitro and in vivo. Clinical evidence indicates that expression MOF is decreased and positively correlated with that of ERα in ECa tissues. Furthermore, MOF physically interacts with ERα and modulates ERα stability in ECa cells. In addition, MOF modulates expression of a subset of endogenous genes regulated by ERα. Taken together, our results define MOF as a potential tumor suppressor in ECa participates in maintenance of ERα protein stability and regulation of ERα action.

BAP18 coactivates androgen receptor action and promotes prostate cancer progression.

BPTF associated protein of 18 kDa (BAP18) has been reported as a component of MLL1-WDR5 complex. However, BAP18 is an uncharacterized protein. The detailed biological functions of BAP18 and underlying mechanisms have not been defined. Androgen receptor (AR), a member of transcription factor, plays an essential role in prostate cancer (PCa) and castration-resistant prostate cancer (CRPC) progression. Here, we demonstrate that BAP18 is identified as a coactivator of AR in Drosophilar experimental system and mammalian cells. BAP18 facilitates the recruitment of MLL1 subcomplex and AR to androgen-response element (ARE) of AR target genes, subsequently increasing histone H3K4 trimethylation and H4K16 acetylation. Knockdown of BAP18 attenuates cell growth and proliferation of PCa cells. Moreover, BAP18 depletion results in inhibition of xenograft tumor growth in mice even under androgen-depletion conditions. In addition, our data show that BAP18 expression in clinical PCa samples is higher than that in benign prostatic hyperplasia (BPH). Our data suggest that BAP18 as an epigenetic modifier regulates AR-induced transactivation and the function of BAP18 might be targeted in human PCa to promote tumor growth and progression to castration-resistance.

RNF8 identified as a co-activator of estrogen receptor α promotes cell growth in breast cancer.

The ring finger protein 8 (RNF8), a key component of protein complex crucial for DNA-damage response, consists of a forkhead-associated (FHA) domain and a really interesting new gene (RING) domain that enables it to function as an E3 ubiquitin ligase. However, the biological functions of RNF8 in estrogen receptor α (ERα)-positive breast cancer and underlying mechanisms have not been fully defined. Here, we have explored RNF8 as an associated partner of ERα in breast cancer cells, and co-activates ERα-mediated transactivation. Accordingly, RNF8 depletion inhibits the expression of endogenous ERα target genes. Interestingly, our results have demonstrated that RNF8 increases ERα stability at least partially if not all via triggering ERα monoubiquitination. RNF8 functionally promotes breast cancer cell proliferation. RNF8 is highly expressed in clinical breast cancer samples and the expression of RNF8 positively correlates with that of ERα. Up-regulation of ERα-induced transactivation by RNF8 might contribute to the promotion of breast cancer progression by allowing enhancement of ERα target gene expression. Our study describes RNF8 as a co-activator of ERα increases ERα stability via post-transcriptional pathway, and provides a new insight into mechanisms for RNF8 to promote cell growth of ERα-positive breast cancer.

MDC1 functionally identified as an androgen receptor co-activator participates in suppression of prostate cancer.

Mediator of DNA damage checkpoint protein 1 (MDC1) is essential for DNA damage response. However, the role of MDC1 in modulating gene transcription independently of DNA damage and the underlying mechanisms have not been fully defined. Androgen receptor (AR) is the central signaling pathway in prostate cancer (PCa) and its target genes are involved in both promotion and suppression of PCa. Here, we functionally identified MDC1 as a co-activator of AR. We demonstrate that MDC1 facilitates the association between AR and histone acetyltransferase GCN5, thereby increasing histone H3 acetylation level on cis-regulatory elements of AR target genes. MDC1 knockdown promotes PCa cells growth and migration. Moreover, depletion of MDC1 results in decreased expression of a subset of the endogenous androgen-induced target genes, including cell cycle negative regulator p21 and PCa metastasis inhibitor Vinculin, in AR positive PCa cell lines. Finally, the expression of MDC1 and p21 correlates negatively with aggressive phenotype of clinical PCa. These studies suggest that MDC1 as an epigenetic modifier regulates AR transcriptional activity and MDC1 may function as a tumor suppressor of PCa, and provide new insight into co-factor-AR-signaling pathway mechanism and a better understanding of the function of MDC1 on PCa.

BAP18 acting as a novel peroxisome proliferator-activated receptor α co-regulator contributes to hepatocellular carcinoma progression.

Hepatocellular carcinoma (HCC) is a common malignancy worldwide with a poor prognosis. The therapeutic outcomes of HCC patients are urgently needed to be improved, and predictive biomarkers for the optimal treatment selection remains to be further defined. In the present study, our results showed that BPTF-associated protein of 18 KDa (BAP18) was highly expressed in HCC tissues. In cultured HCC cells, BAP18 regulated a subset of down-stream genes involved in different functions, particularly including peroxisome proliferator-activated receptor (PPAR) pathway and lipid metabolism. Furthermore, BAP18 co-activated PPARα-mediated transactivation and facilitated the recruitment of nucleosome acetyltransferase of H4 (NuA4)/tat interacting protein 60 (TIP60) complex, thereby increasing histone H4 acetylation on stearoyl-CoA desaturase 1 (SCD1) loci. In addition, BAP18 promoted HCC cell proliferation, increased intracellular lipid levels and enhanced cell survival under the metabolic stress conditions, such as glucose limitation or tyrosine kinase inhibitors (TKIs) treatment. Importantly, higher BAP18 expression was positively correlated with the postoperative recurrence and the poor disease-free survival in clinical patients receiving sorafenib treatment. Altogether, we discovered that BAP18 plays an oncogenic role in the survival and proliferation of HCC cells, and BAP18 may serve as a predictive biomarker for adjunct TKIs treatment in patients with HCC, and further facilitate the precise treatment.

Ring finger protein 6 enhances chemo-resistance by transcriptionally activating proliferating cell nuclear antigen expression and attenuating DNA damage in lung adenocarcinoma.

The E3 ubiquitin ligase RING finger protein 6 (RNF6) is elevated in several cancers, including prostate and colorectal cancers. Here, we extended the finding of elevated RNF6 expression levels and its association with poor prognosis in patients with lung adenocarcinoma (LUAD). Genome-wide RNA sequencing in H3255 cells with RNF6 knockdown, followed by analysis of differentially expressed genes using Clusters of Orthologous Groups and gene set enrichment analysis revealed aberrations in genes related to DNA repair, especially double-strand break (DSB) repair. RNF6 knockdown increased γH2AX foci, a biomarker for DSBs in H3255 and A549 LUAD cells, and enhanced DNA damage induced by chemotherapy in cisplatin-resistant A549/CDDP cells. In a series of experiments in cultured cells, as well as in nude mice carrying xenografts, RNF6 knockdown restored the sensitivity of A549/CDDP cells to cisplatin treatment. Mechanistically, RNA sequencing in RNF6-knockdown cells revealed the significant downregulation of proliferating cell nuclear antigen (PCNA), an oncogene that promotes DNA repair. Re-chromatin immunoprecipitation assay results suggested the formation of a RNF6-TCF4 complex that binds to the PCNA promoter to activate its transcription. Downregulation of RNF6 reduced TCF4 recruitment to PCNA promoters in H3255 and A549 cells, indicating that RNF6 regulates PCNA transcription to a certain extent by regulating TCF4 binding to PCNA promoters. The collective results implicate RNF6 overexpression as a molecular target in the management of cisplatin-resistant LUAD.

ATXN7L3 positively regulates SMAD7 transcription in hepatocellular carcinoma with growth inhibitory function.

BACKGROUND: Hepatocellular carcinoma (HCC) is a leading cause of cancer death worldwide, with unmet need for the pharmacological therapy. The functions of ATXN7L3 in HCC progression are not known. METHODS: RNA sequence, quantitative real-time PCR, and western blot were performed to detect gene expression. Chromatin immunoprecipitation was performed to detect possible mechanisms. Immunohistochemical stain was performed to examine the protein expression. Colony formation, cell growth curve and xenograft tumor experiments were performed to examine cell growth in vitro and in vivo. FINDINGS: ATXN7L3 functions as a coactivator for ERα-mediated transactivation in HCC cells, thereby contributing to enhanced SMAD7 transcription. ATXN7L3 is recruited to the promoter regions of SMAD7 gene, thereby regulating histone H2B ubiquitination level, to enhance the transcription of SMAD7. A series of genes regulated by ATXN7L3 were identified. Moreover, ATXN7L3 participates in suppression of tumor growth. In addition, ATXN7L3 is lower expressed in HCC samples, and the lower expression of ATXN7L3 positively correlates with poor clinical outcome in patients with HCC. INTERPRETATION: This study demonstrated that ATXN7L3 is a novel regulator of SMAD7 transcription, subsequently participating in inhibition of tumor growth in HCC, which provides an insight to support a previously unknown role of ATXN7L3 in HCC progression. FUND: This work was funded by 973 Program Grant from the Ministry of Science and Technology of China (2013CB945201), National Natural Science Foundation of China (31871286, 81872015, 31701102, 81702800, 81902889), Foundation for Special Professor of Liaoning Province, Natural Science Foundation of Liaoning Province (No.20180530072); China Postdoctoral Science Foundation (2019M651164).

BAP18 is involved in upregulation of CCND1/2 transcription to promote cell growth in oral squamous cell carcinoma.

BACKGROUND: As a reader of histone H3K4me3, BPTF associated protein of 18 kDa (BAP18) is involved in modulation of androgen receptor action in prostate cancer. However, the function of BAP18 on oral squamous cell carcinoma (OSCC) and its molecular mechanism remains to be elusive. METHODS: OSCC-derived cell lines carrying silenced BAP18 were established by Lentiviral infection. Quantitative PCR (qPCR), western blot, and ChIP assay were performed to detect gene transcription regulation and the possible mechanism. Colony formation, cell growth curve and xenograft tumor experiments were performed to examine cell growth and proliferation. FINDINGS: Our study demonstrated that BAP18 was highly expressed in OSCC samples compared with that in benign. BAP18 depletion obviously influenced the expression of a series of genes, including cell cycle-related genes. We thus provided the evidence to demonstrate that BAP18 depletion significantly decreases CCND1 and CCND2 (CCND1/2) transcription. In addition, BAP18 is recruited to the promoter regions of CCND1/2, thereby facilitating the recruitment of the core subunits of MLL1 complex to the same regions, to increase histone H3K4me3 levels. Furthermore, BAP18 depletion delayed G1-S phase transition and inhibited cell growth in OSCC-derived cell lines. INTERPRETATION: This study suggests that BAP18 is involved in modulation of CCND1/2 transcription and promotes OSCC progression. BAP18 could be a potential target for OSCC treatment and diagnosis. FUND: This work was funded by National Natural Science Foundation of China (31871286, 81872015, 31701102, 81702800, 81902889), Foundation for Special Professor of Liaoning Province, and Supported project for young technological innovation-talents in Shenyang (No. RC170541).

USP22 positively modulates ERα action via its deubiquitinase activity in breast cancer.

Estrogen receptor α (ERα) is the crucial factor in ERα-positive breast cancer progression. Endocrine therapies targeting ERα signaling is one of the widely used therapeutic strategies for breast cancer. However, a large number of the patients become refractory to therapy. Abnormal expression of ERα co-regulator facilitates breast cancer development and tendency of endocrine resistance. Thus, it is necessary to discover the novel co-regulators modulating ERα action. Here, we demonstrate that histone deubiquitinase USP22 is highly expressed in breast cancer samples compared with that in the benign tissue, and high expression of USP22 was significantly associated with poorer overall survival in BCa samples. Moreover, USP22 associates with ERα to be involved in maintenance of ERα stability. USP22 enhances ERα-induced transactivation. We further provide the evidence that USP22 is recruited together with ERα to cis-regulatory elements of ERα target gene. USP22 promotes cell growth even under hypoxia condition and with the treatment of ERα antagonist in breast cancer cells. Importantly, the deubiquitination activity of USP22 is required for its functions on maintenance of ERα stability, thereby enhancing ERα action and conferring endocrine resistance in breast cancer.

SNF5 is Involved in Suppression of Hepatocellular Carcinoma Progression via TGF-Beta 1 Signaling.

SNF5 (SMARCB1/INI1/BAF47), a core subunit of SWI/SNF complex, has been reported to modulate cell proliferation and apoptosis. Genetic evidence has suggested that SNF5 participates in tumor suppression. However, the detailed biological function and underlying mechanisms of SNF5 in hepatocellular carcinoma (HCC) progression remain unclear. Here, SNF5 expression reduction in HCC tissues compared with the adjacent non-cancerous tissues has been demonstrated. Importantly, the results showed that reduced SNF5 expression has a strong correlation with worse overall survival of HCC patients. The data demonstrated that knockdown of SNF5 significantly promoted cell growth and migration in Hep3B and HCCLM3 cell lines. Interestingly, it was found that SNF5 suppressed transforming growth factor-ß1 (TGF-ß1) expression, and SNF5 mRNA expression was negatively correlated with TGF-ß1 in HCC tissues. Furthermore, depletion of SNF5 attenuated the sensitivity of HCC cells to sorafenib. Thus, the data suggested that SNF5 may participate in HCC suppression, and reduced expression of SNF5 correlates with the poor differentiation and prognosis of HCC, indicating that SNF5 might be an important prognostic biomarker and promising therapeutic target for HCC. Anat Rec, 299:869-877, 2016. © 2016 Wiley Periodicals, Inc.

MDC1 Enhances Estrogen Receptor-mediated Transactivation and Contributes to Breast Cancer Suppression.

Estrogen receptor α (ERα) is a key transcriptional factor in the proliferation and differentiation in mammary epithelia and has been determined to be an important predictor of breast cancer prognosis and therapeutic target. Meanwhile, diverse transcriptional co-regulators of ERα play crucial and complicated roles in breast cancer progression. Mediator of DNA damage checkpoint 1 (MDC1) has been identified as a critical upstream mediator in the cellular response to DNA damage, however, some non-DNA damage responsive functions of MDC1 haven't been fully defined. In this study, we have identified MDC1 as a co-activator of ERα in breast cancer cells and demonstrated that MDC1 associates with ERα. MDC1 was also recruited to estrogen response element (ERE) of ERα target gene. Knockdown of MDC1 reduced the transcription of the endogenous ERα target genes, including p21. MDC1 depletion led to the promotion of breast cancer progression, and the expression of MDC1 is lower in breast cancer. Taken together, these results suggested that MDC1 was involved in the enhancement of ERα-mediated transactivation in breast cancer cells. This positive regulation by MDC1 might contribute to the suppression of breast cancer progression by acting as a barrier of positive to negative ERα function transformation.

Identification of endocrine disrupting chemicals activating SXR-mediated transactivation of CYP3A and CYP7A1.

Endocrine disrupting chemicals (EDCs) have emerged as a major public health issue because of their potentially disruptive effects on physiological hormonal actions. SXR (steroid xenobiotic receptor), also known as NR1I2, regulates CYP3A expression in response to exogenous chemicals, such as EDCs, after binding to SXRE (SXR response element). In our study, luciferase assay showed that 14 out of 55 EDCs could enhance SXR-mediated rat or human CYP3A gene transcription nearly evenly, and could also activate rat CYP7A1 gene transcription by cross-interaction of SXR and LXRE (LXRα response element). SXR diffused in the nucleus without ligand, whereas intranuclear foci of liganded SXR were produced. Furthermore, endogenous mRNA expression of CYP3A4 gene was enhanced by the 14 positive EDCs. Our results suggested a probable mechanism of EDCs disrupting the steroid or xenobiotic metabolism homeostasis via SXR.