Methyl-CpG-DNA binding proteins in human prostate cancer: expression of CXXC sequence containing MBD1 and repression of MBD2 and MeCP2

We analyzed gene expression of MBD1, MBD2, MBD3, MBD4, and MeCP2 and protein expression of MBD1, MBD2, and MeCP2 in prostate cancer cell lines, benign prostate epithelium (BPH-1) cell line, 49 BPH tissues, and 46 prostate cancer tissues. The results of this study demonstrate that MBD2 gene is expressed in all samples and MeCP2 gene is expressed in all cancer cell lines but not in BPH-1 cell line. However, there was no protein expression for MBD2 and MeCP2 in cancer cell lines and cancer tissues. For CXXC sequence containing MBD1, both protein and mRNA were expressed in cancer cell lines, cancer tissues, BPH-1 cell line, and BPH tissues. We observed that, in BPH tissues and low-grade cancer tissues, MBD1 protein expression was very high and gradually decreased with increase of cancer grade. Treatment of cancer cell lines with proteasome inhibitor (MG-132) did not restore expression of MBD2 and MeCP2 proteins. When prostate cancer cell lines were treated with hypomethylating agent, 5-aza-2(')-deoxycytidine (DNMT inhibitor), HDAC1 and HDAC2 expression was decreased. This is the first report demonstrating that CXXC sequence containing MBD1 is overexpressed and can be the major factor of hypermethylated chromatin segments through HDAC1/2 translocation and histone deacetylation in human prostate cancer.     

EGR1促进前列腺增生上皮细胞系 BPH-1的增殖

早期生长反应基因1（early growth response gene 1, EGR1）属于锌指结构的转录因子,表达受多种因素调节,其蛋白至少参与对30种以上靶基因的调控. EGR1在前列腺癌中作为癌基因其表达量与肿瘤的恶性程度成正比,而在良性前列腺增生（benign prostatic hyperplasia, BPH）中其机制和功能尚不明确. EGR1在大鼠和人BPH组织中表达升高, 提示EGR1在BPH进程中发挥重要作用. 通过构建EGR1表达载体,以及EGR1稳定转染的良性前列腺增生上皮细胞系BPH-1,可见过表达EGR1的BPH-1细胞增殖能力升高. 通过转染siRNA将EGR1表达抑制,BPH 1细胞的增殖水平下降. 雌激素在BPH疾病进程中发挥重要作用, 在BPH 1细胞中,雌二醇 (estradiol, E2) 能促进EGR1的核迁移,从而激活其转录活性. 在EGR1稳定转染的BPH 1细胞系中胰岛素样生长因子2 (insulin like growth factor 2, IGF2) 的表达上调,表明EGR1可以调控IGF2的表达. 同时发现,E2可上调BPH-1细胞中 IGF2的表达,而将EGR1敲除后上调效果消失, 说明E2通过EGR1来调节IGF2的表达. E2对EGR1及其靶基因的调节可能是E2参与影响BPH的重要环节. 本文为进一步研究E2和EGR1在BPH中作用奠定了基础.     

Differential response to zinc-induced apoptosis in benign prostate hyperplasia and prostate cancer cells

Zinc concentrations in the prostate are uniquely high but are dramatically decreased with prostate cancer. Studies have suggested that increasing zinc in the prostate may be a potential therapeutic strategy. The goal of this study was to evaluate the antiproliferative effects of zinc in prostate cancer cells (PC-3) and noncancerous benign prostate hyperplasia (BPH) cells (BPH-1) and to define possible mechanisms. PC-3 and BPH-1 cells were treated with zinc (0–250 μM) for 24 and 48 h, and cell growth and viability were examined. Apoptosis was assessed by phosphatidylserine externalization, caspase activation and protein expression of B-cell CLL/lymphoma 2 (Bcl-2)-associated X protein (BAX):Bcl-2. BPH-1 cells were more sensitive to the antiproliferative effects of zinc compared to PC-3. The response to zinc in PC-3 and BPH-1 cells differed as evidenced by opposing effects on Bcl-2:BAX expression. Additionally, different effects on the nuclear expression and activity of the p65 subunit of nuclear factor kappa B were observed in response to zinc between the two cell types. The differential response to zinc in PC-3 and BPH-1 cells suggests that zinc may serve an important role in regulating cell growth and apoptosis in prostate cancer and hyperplasia cells.     

Colon cancer cells maintain low levels of pyruvate to avoid cell death caused by inhibition of HDAC1/HDAC3

Human colon cancer cells and primary colon cancer silence the gene coding for LDH (lactate dehydrogenase)-B and up-regulate the gene coding for LDH-A, resulting in effective conversion of pyruvate into lactate. This is associated with markedly reduced levels of pyruvate in cancer cells compared with non-malignant cells. The silencing of LDH-B in cancer cells occurs via DNA methylation, with involvement of the DNMTs (DNA methyltransferases) DNMT1 and DNMT3b. Colon cancer is also associated with the expression of pyruvate kinase M2, a splice variant with low catalytic activity. We have shown recently that pyruvate is an inhibitor of HDACs (histone deacetylases). Here we show that pyruvate is a specific inhibitor of HDAC1 and HDAC3. Lactate has no effect on any of the HDACs examined. Colon cancer cells exhibit increased HDAC activity compared with non-malignant cells. HDAC1 and HDAC3 are up-regulated in colon cancer cells and in primary colon cancer, and siRNA (small interfering RNA)-mediated silencing of HDAC1 and HDAC3 in colon cancer cells induces apoptosis. Colon cancer cells silence SLC5A8, the gene coding for a Na(+)-coupled pyruvate transporter. Heterologous expression of SLC5A8 in the human colon cancer cell line SW480 leads to inhibition of HDAC activity when cultured in the presence of pyruvate. This process is associated with an increase in intracellular levels of pyruvate, increase in the acetylation status of histone H4, and enhanced cell death. These studies show that cancer cells effectively maintain low levels of pyruvate to prevent inhibition of HDAC1/HDAC3 and thereby to evade cell death.     

Inhibition of histone deacetylases promotes ubiquitin-dependent proteasomal degradation of DNA methyltransferase 1 in human breast cancer cells

Histone deacetylases (HDAC) play a critical role in chromatin modification and gene expression. Recent evidence indicates that HDACs can also regulate functions of nonhistone proteins by catalyzing the removal of acetylated lysine residues. Here, we show that the HDAC inhibitor LBH589 down-regulates DNA methyltransferase 1 (DNMT1) protein expression in the nucleus of human breast cancer cells. Cotreatment with the proteasomal inhibitor MG-132 abolishes the ability of LBH589 to reduce DNMT1, suggesting that the proteasomal pathway mediates DNMT1 degradation on HDAC inhibition. Deletion of the NH(2)-terminal 120 amino acids of DNMT1 diminishes LBH589-induced ubiquitination, indicating that this domain is essential for its proteasomal degradation. DNMT1 recruits the molecular chaperone heat shock protein 90 (Hsp90) to form a chaperone complex. Treatment with LBH589 induces hyperacetylation of Hsp90, thereby inhibiting the association of DNMT1 with Hsp90 and promoting ubiquitination of DNMT1. In addition, inactivation of HDAC1 activity by small interfering RNA and MS-275 is associated with Hsp90 acetylation in conjunction with reduction of DNMT1 protein expression. We conclude that the stability of DNMT1 is maintained in part through its association with Hsp90. Disruption of Hsp90 function by HDAC inhibition is a unique mechanism that mediates the ubiquitin-proteasome pathway for DNMT1 degradation. Our studies suggest a new role for HDAC1 and identify a novel mechanism of action for the HDAC inhibitors as down-regulators of DNMT1.     

DNMT1 and HDAC1 gene expression in impaired spermatogenesis and testicular cancer

DNA methylation catalyzed by DNA methyltransferases (DNMTs) and histone deacetylation catalyzed by histone deacetylases (HDACs) play an important role for the regulation of gene expression during carcinogenesis and spermatogenesis. We therefore studied the cell-specific expression of DNMT1 and HDAC1 for the first time in human testicular cancer and impaired human spermatogenesis. During normal spermatogenesis, DNMT1 and HDAC1 were colocalized in nuclei of spermatogonia. While HDAC1 was additionally present in nuclei of Sertoli cells, DNMT1 was restricted to germ cells exhibiting a different expression pattern of mRNA (in pachytene spermatocytes and round spermatids) and protein (in round spermatids). Interestingly, in infertile patients revealing round spermatid maturation arrest, round spermatids lack DNMT1 protein, while pachytene spermatocytes became immunopositive for DNMT1. In contrast, no changes in the expression pattern could be observed for HDAC1. This holds true also in testicular tumors, where HDAC1 has been demonstrated in embryonal carcinoma, seminoma and teratoma. Interestingly, DNMT1 was not expressed in seminoma, but upregulated in embryonal carcinoma. Olufunmilade A. Omisanjo is a scholarship holder of the German Academic Exchange Service (DAAD). Sonja Hartmann is a member of the German Research Foundation (DFG) Research Training Group 533 Cell–cell-Interaction in Reproduction.     

Glucose-regulated protein 78 modulates cell growth,epithelial–mesenchymal transition,and oxidative stress in the hyperplastic prostate

Benign prostatic hyperplasia (BPH) is a chronic condition which mainly affects elderly males. Existing scientific evidences have not completely revealed the pathogenesis of BPH. Glucose-regulated protein 78 (GRP78) is a member of the heat shock protein 70 superfamily, which serves as an important regulator in many diseases. This study aims at elucidating the role of GRP78 in the BPH process. Human prostate tissues, cultured human prostate cell lines (BPH-1 and WPMY-1) and clinical data from BPH patients were utilized. The expression and localization of GRP78 were determined with quantitative real time PCR (qRT-PCR), Western blotting and immunofluorescence staining. GRP78 knockdown and overexpression cell models were created with GRP78 siRNA and GRP78 plasmid transfection. With these models, cell viability, apoptosis rate, as well as marker levels for epithelial-mesenchymal transition (EMT) and oxidative stress (OS) were detected by CCK8 assay, flow cytometry analysis and Western blotting respectively. AKT/mTOR and MAPK/ERK pathways were also evaluated. Results showed GRP78 was localized in the epithelium and stroma of the prostate, with higher expression in BPH tissues. There was no significant difference in GRP78 expression between BPH-1 and WPMY-1 cell lines. In addition, GRP78 knockdown (KD) slowed cell growth and induced apoptosis, without effects on the cell cycle stage of both cell lines. Lack of GRP78 affected expression levels of markers for EMT and OS. Consistently, overexpression of GRP78 completely reversed all effects of knocking down GRP78. We further found that GRP78 modulated cell growth and OS via AKT/mTOR signaling, rather than the MAPK/ERK pathway. Overall, our novel data demonstrates that GRP78 plays a significant role in the development of BPH and suggests that GRP78 might be rediscovered as a new target for treatment of BPH.Subject terms: Prostatic diseases, Preclinical research     

Histone Deacetylase (HDAC) 10 Suppresses Cervical Cancer Metastasis through Inhibition of Matrix Metalloproteinase (MMP) 2 and 9 Expression

Aberrant expression of histone deacetylases (HDACs) is associated with carcinogenesis. Some HDAC inhibitors are widely considered as promising anticancer therapeutics. A major obstacle for development of HDAC inhibitors as highly safe and effective anticancer therapeutics is that our current knowledge on the contributions of different HDACs in various cancer types remains scant. Here we report that the expression level of HDAC10 was significantly lower in patients exhibiting lymph node metastasis compared with that in patients lacking lymph node metastasis in human cervical squamous cell carcinoma. Forced expression of HDAC10 in cervical cancer cells significantly inhibited cell motility and invasiveness in vitro and metastasis in vivo. Mechanistically, HDAC10 suppresses expression of matrix metalloproteinase (MMP) 2 and 9 genes, which are known to be critical for cancer cell invasion and metastasis. At the molecular level, HDAC10 binds to MMP2 and -9 promoter regions, reduces the histone acetylation level, and inhibits the binding of RNA polymerase II to these regions. Furthermore, an HDAC10 mutant lacking histone deacetylase activity failed to mimic the functions of full-length protein. These results identify a critical role of HDAC10 in suppression of cervical cancer metastasis, underscoring the importance of developing isoform-specific HDAC inhibitors for treatment of certain cancer types such as cervical squamous cell carcinoma.