Sensitivity of human prostate cancer cells to chemotherapeutic drugs depends on EndoG expression regulated by promoter methylation

Analysis of promoter sequences of all known human cytotoxic endonucleases showed that endonuclease G (EndoG) is the only endonuclease that contains a CpG island, a segment of DNA with high G+C content and a site for methylation, in the promoter region. A comparison of three human prostate cancer cell lines showed that EndoG is highly expressed in 22Rv1 and LNCaP cells. In PC3 cells, EndoG was not expressed and the EndoG CpG island was hypermethylated. The expression of EndoG correlated positively with sensitivity to cisplatin and etoposide, and the silencing of EndoG by siRNA decreased the sensitivity of the cells to the chemotherapeutic agents in the two EndoG-expressing cell lines. 5-aza-2'-deoxycytidine caused hypomethylation of the EndoG promoter in PC3 cells, induced EndoG mRNA and protein expression, and made the cells sensitive to both cisplatin and etoposide. The acetylation of histones by trichostatin A, the histone deacetylase inhibitor, induced EndoG expression in 22Rv1 cells, while it had no such effect in PC3 cells. These data are the first indication that EndoG may be regulated by methylation of its gene promoter, and partially by histone acetylation, and that EndoG is essential for prostate cancer cell death in the used models.     

Cell kinetic measurements in prostate cancer

: To test the relative effect of neoadjuvant and adjuvant androgen deprivation on the radiation response of an androgen dependent tumor.

: The transplantable, adrogen and dependent. Shionogi adenocarcinoma was grown as allografts in the ind limbs of NCr/Sed (nu/nu) athymic nude mice. Bilateral orchiectomy was the chosen form of androgen deprivation. Groups of tumors were irradiated to graded tumor doses and then studied for durable tumor control. The radiation response was expressed as the radiation dose required to control 50% of the tumors (TCD₅₀). The sequence of radiation and orchiectomy was studied.

; When radiation was combined with orchiectomy the Shionogi tumor was significantly more likely to be controlled than when radiation was used alone. Orchiectomy 12 days prior to radiation (neoadjuvant therapy) produced a significantly greater decline in the TCD₅₀ than when orchiectomy was used 1 day or 12 days after radiation (adjuvant therapy). If, before radiation, tumors were allowed to regrow after orchiectomy to their original size in an androgen independent fashion then the advantage was largely lost. Those tumors responding well to neoadjuvant orchiectomy (>50% volume decrease) weer significantly more likely to be eradicated by radiation that those with a lesser response.

: When using combination of androgen deprivation and radiation in the treatment of the Shionogi tumor, sequence and timing of the therapies are crucial to maximize the effect.     

Epigenetic biomarkers in prostate cancer: Current and future uses

Epigenome alterations are characteristic of nearly all human malignancies and include changes in DNA methylation, histone modifications and microRNAs (miRNAs). However, what induces these epigenetic alterations in cancer is largely unknown and their mechanistic role in prostate tumorigenesis is just beginning to be evaluated. Identification of the epigenetic modifications involved in the development and progression of prostate cancer will not only identify novel therapeutic targets but also prognostic and diagnostic markers. This review will focus on the use of epigenetic modifications as biomarkers for prostate cancer.     

UCH-L1 promotes cancer metastasis in prostate cancer cells through EMT induction

Ubiquitin C-terminal hydrolse-L1 (UCH-L1) is a deubiquitinating enzyme (DUB) that cleaves the ubiquitin (ub) moiety from ub precursors or protein substrates. The correlation between UCH-L1 and cancer has been reported in various tissues, but the role of UCH-L1 in prostate cancer has not been thoroughly researched. Here we found that UCH-L1 is specifically highly expressed in the metastatic DU145 prostate cancer cell line, but not in the benign or weakly metastatic prostate cancer cells. To determine the role of UCH-L1 in prostate cancer metastasis, we constructed UCH-L1-knockdown DU145 and UCH-L1 or the active site mutant form of UCH-L1 (UCH-L1 C90S) expressing RWPE1 stable cells. Notably, the expression of UCH-L1 in RWPE1 cells promotes epithelial-to-mesenchymal transition (EMT), and this is an important process for cancer cell invasion and metastasis. On the contrary, knockdown of UCH-L1 in DU145 cells induces MET, the reverse program of EMT. Furthermore, the change of EMT status caused by altering the UCH-L1 level affects the migration and invasiveness of prostate cancer cells. Our results indicate that UCH-L1 promotes prostate cancer metastasis through EMT induction and UCH-L1 could be a novel diagnostic and therapeutic target for prostate cancer treatment.     

2′-羟基黄烷酮对前列腺癌细胞的放射增敏作用及机制探讨

目的 研究2′-羟基黄烷酮(2′-HF)对前列腺癌细胞的放射增敏作用并初步探讨其机制。方法 应用克隆形成实验、叔丁基过氧化氢(TBHP)氧化损伤实验、Hoechst荧光染色、Annexin V-FITC和PI流式细胞仪凋亡检测实验检测2′-HF对前列腺癌VCaP细胞的放射敏感性影响。应用Western blot方法检测2′-HF对VCaP细胞中AKT、p-AKT、AKR1C3蛋白表达水平影响并初步探讨作用机制。采用t检验和析因方差分析检验结果。结果 克隆形成实验结果提示经2′-HF处理的VCaP细胞在照射后增殖能力明显低于空白对照组(P=0.010),SR=1.19;TBHP氧化损伤实验结果提示经2′-HF处理的VCaP细胞的抗氧化损伤能力明显弱于空白对照组(P=0.015);Hoechst荧光染色、Annexin V-FITC和PI流式凋亡检测实验结果提示2′-HF联合放射线会增加VCaP细胞调亡(P=0.001);Western blot实验结果提示2′-HF可以抑制VCaP细胞中p-AKT、AKR1C3蛋白的表达(P=0.013,P=0.016)。结论 2′-HF可提高前列腺癌细胞的放射敏感性,这可能与其对前列腺癌细胞中AKT通路阻滞或AKR1C3蛋白表达抑制相关。     

前列腺癌特异抗原3对前列腺癌LNCaP细胞增殖的影响

背景与目的:前列腺癌抗原3(prostate cancer antigen 3,PCA3)作为一种长链非编码RNA已被证实在前列腺癌中特异性高表达,预示其可能在前列腺癌的发生、发展中发挥重要作用。本研究拟通过靶向干扰PCA3以初步观察其对前列腺癌细胞株LNCaP细胞增殖的影响。方法:使用脂质体介导小干扰RNA(siRNA)转染前列腺癌LNCaP细胞,荧光倒置显微镜观察转染效率,实时定量PCR检测siRNA对PCA3的抑制程度;CCK-8法和克隆形成实验检测转染前列腺癌LNCaP细胞后细胞的增殖能力。结果:荧光倒置显微镜观察转染后48 h转染效率为50%～70%;实时定量PCR检测结果发现,与PCA3 siRNA(si731)和PCA3 siRNA(si2060)比较,PCA3 siRNA(si164)对PCA3的抑制程度最大;细胞增殖实验显示,转染PCA3 siRNA(si164)组中LNCaP细胞增殖能力较阴性对照组明显下降(P<0.05)。结论:PCA3 siRNA(si164)在前列腺癌LNCaP细胞株中能靶向沉默PCA3的表达并抑制前列腺癌细胞增殖,表明PCA3通过调节细胞增殖促进前列腺癌发展,并可成为前列腺癌新的治疗靶点。     

Promoter hypermethylation in circulating blood cells identifies prostate cancer progression

Promoter hypermethylation of circulating cell DNA has been advocated as a diagnostic marker for prostate cancer, but its prognostic use is currently unclear. To assess this role, we compared hypermethylation of circulating cell DNA from prostate cancer patients with (Group 1, n = 20) and without (Group 2, n = 22) disease progression and age-matched controls (benign prostatic hyperplasia, Group 3, n = 22). We measured hypermethylation of 10 gene promoters in 2 sequential venous samples, obtained at diagnosis and during disease progression (median time, 15 months later). Matched time samples were obtained in the nonprogressing patients. We found that more hypermethylation was detected in the diagnostic sample from the patients with cancer than in controls for GSTP1, RASSF1 alpha, APC and RAR beta (p < 0.0001). Patients undergoing disease progression had a significant increase in methylation levels of these 4 genes when compared to the other patients (p < 0.001). Patients at risk of disease progression have higher detectable concentrations of circulating cell hypermethylation, than those without progression. The extent of this hypermethylation increases during disease progression and can be used to identify the extent and duration of treatment response in prostate cancer.     

Kindlin-2 controls sensitivity of prostate cancer cells to cisplatin-induced cell death

Resistance to anticancer drugs is often observed in prostate cancer therapy. Kindlin-2 was recently found overexpressed during cancer progression. In this study, we examined the functional role of Kindlin-2 in cisplatin-induced prostate cancer cell death. Kindlin-2 was highly expressed in the androgen-insensitive (PC-3 and DU-145), but not in the androgen-sensitive cell lines (e.g., LNCaP). Overexpression of Kindlin-2 in LNCaP protected the cells from cisplatin-induced death, while Kindlin-2 knock-down in PC-3 cells enhanced cisplatin sensitivity. Mechanistically, Kindlin-2 regulation of the anti-apoptotic Bcl-xL may explain the increased cell death in the absence of Kindlin-2. Taken together, Kindlin-2 appears to play a functional role in prostate cancer cell sensitivity to cisplatin. Targeting Kindlin-2 may therefore improve drug efficacy and reduce drug doses, and would likely be beneficial for the treatment of prostate cancer.     

Concepts of epigenetics in prostate cancer development

Substantial evidence now supports the view that epigenetic changes have a role in the development of human prostate cancer. Analyses of the patterns of epigenetic alteration are providing important insights into the origin of this disease and have identified specific alterations that may serve as useful diagnostic and prognostic biomarkers. Examination of cancer methylation patterns supports a stem cell origin of prostate cancer. It is well established that methylation of GSTpi is a marker of prostate cancer, and global patterns of histone marking appear to be linked to cancer prognosis with levels of acetylated histones H3K9, H3K18, and H4K12, and of dimethylated H4R3 and H3K4, dividing low-grade prostate cancer (Gleason 6 or less) into two prognostically separate groups. Elevated levels of several components of the polycomb group protein complex, EZH2, BMI1, and RING1, can also act as biomarkers of poor clinical outcome. Many components of the epigenetic machinery, including histone deacetylase (whose expression level is linked to the TMPRSS2:ERG translocation) and the histone methylase EZH2, are potential therapeutic targets. The recent discovery of the role of small RNAs in governing the epigenetic status of individual genes offers exciting new possibilities in therapeutics and chemoprevention.     

DNA demethylation by 5-aza-2-deoxycytidine treatment abrogates 17 beta-estradiol-induced cell growth and restores expression of DNA repair genes in human breast cancer cells

Prolonged exposure to elevated levels of estrogen is a risk factor for breast cancer. Though increased cell growth and loss of DNA repair capacity is one of the proposed mechanisms for estrogen-induced cancers, the mechanism through which estrogen induces cell growth and decreases DNA repair capacity is not clear. DNA hypermethylation is known to inactivate DNA repair genes and apoptotic response in cancer cells. Therefore, the objective of this study was to determine the role of DNA hypermethylation in estrogen-induced cell growth and regulation of DNA repair genes expression in breast cancer cells. To achieve this objective, the estrogen-responsive MCF-7 cells either pretreated with 5-aza-2-deoxycytidine (5-aza-dC) or untreated (as control) were exposed to 17 beta-estradiol (E2), and its effect on cell growth and expression of DNA repair genes were measured. The result revealed that 5-aza-dC abrogates the E2-induced growth in MCF-7 cells. An increased expression of OGG1, MSH4, and MLH1 by 5-aza-dC treatment alone, suggest the DNA hypermethylation as a potential cause for decreased expression of these genes in MCF-7 cells. The decreased expression of ERCC1, XPC, OGG1, and MLH1 by E2 alone and its restoration by co-treatment with 5-aza-dC further suggest that E2 reduces the expression of these DNA repair genes potentially through promoter hypermethylation. Reactivation of mismatch repair (MMR) gene MLH1 and abrogation of E2-induced cell growth by 5-aza-dC treatment suggest that estrogen causes increased growth in breast cancer cells potentially through the inhibition of MMR-mediated apoptotic response. In summary, this study suggests that estrogen increases cell growth and decreases the DNA repair capacity in breast cancer cells, at least in part, through epigenetic mechanism.     

Concordant colon tumors in monozygotic twins previously treated for prostate cancer

This report describes the quasi-simultaneous occurrence of colon cancers in monozygotic twin brothers (age 63 years) who had undergone androgen deprivation therapy for prostate cancers 4 years earlier. Concordance among male twins for both of these cancers has never been reported. Although the family history suggested possible genetic predispositions to both cancers, the twins have no evidence of the genetic alterations associated with hereditary colorectal tumors. We explore the possibility that colorectal tumorigenesis in these twins was fuelled by a combination of genetic and iatrogenic factors, in particular the androgen deprivation therapy used to treat their prostate cancers. Arnoud Templeton and Giancarlo Marra have contributed equally to this work.     

前列腺癌干细胞与去势抵抗性前列腺癌放射性耐受的研究进展

前列腺癌经过去势治疗后有进展为去势抵抗性前列腺癌的可能。去势抵抗性前列腺癌对临床医生最大的挑战为其治疗抵抗特性。针对放疗耐受,相关研究认为与前列腺癌干细胞及前列腺癌干细胞相关miRNA相关。下文从去势抵抗性前列腺癌进展机制、前列腺癌干细胞及前列腺癌干细胞相关miRNA等方面介绍去势抵抗性前列腺癌放射性耐受的研究进展。     

Cytogenomic aberrations associated with prostate cancer

Genetic changes associated with prostate cancer have finally begun to elucidate some of the mechanisms involved in the etiology of this complex and common disease. We highlight consistent and relatively frequent abnormalities seen by various methodologies. Specifically, the results of conventional and molecular cytogenetic studies, genome-wide association studies with single nucleotide polymorphisms, recurrent gene fusions, and epigenetic analyses are discussed.