High-density array analysis of DNA methylation in Tamoxifen-resistant breast cancer cell lines

Roughly two-thirds of all breast cancers are ERα-positive and can be treated with the antiestrogen, Tamoxifen, however resistance occurs in 33% of women who take the drug for more than 5 y. Aberrant DNA methylation, an epigenetic mechanism that alters gene expression in cancer, is thought to play a role in this resistance. To develop an understanding of Tamoxifen-resistance and identify novel pathways and targets of aberrant methylation, DNA from MCF-7 breast cancer cells and Tamoxifen-resistant derivatives, TMX2–11 and TMX2–28, were analyzed using the Illumina HumanMethylation450 BeadChip. Normalizing against MCF-7 values, ERα-positive TMX2–11 had 4000 hypermethylated sites and ERα-negative TMX2–28 had over 33?000. Analysis of CpG sites altered in both TMX2–11 and TMX2–28 revealed that the Tamoxifen-resistant cell lines share 3000 hypermethylated and 200 hypomethylated CpGs. ZNF350 and MAGED1, two genes hypermethylated in both cell lines, were examined in greater detail. Treatment with 5-aza-2′deoxycitidine caused a significant reduction in promoter methylation of both ZNF350 and MAGED1 and a corresponding increase in expression in TMX2–28. A similar relationship between methylation and expression was not detected in TMX2–11. Our findings are indicative of the variable responses to methylation-targeted breast cancer therapy and highlight the need for biomarkers that accurately predict treatment outcome.     

High-density array analysis of DNA methylation in Tamoxifen-resistant breast cancer cell lines

Roughly two-thirds of all breast cancers are ERα-positive and can be treated with the antiestrogen, Tamoxifen, however resistance occurs in 33% of women who take the drug for more than 5 y. Aberrant DNA methylation, an epigenetic mechanism that alters gene expression in cancer, is thought to play a role in this resistance. To develop an understanding of Tamoxifen-resistance and identify novel pathways and targets of aberrant methylation, DNA from MCF-7 breast cancer cells and Tamoxifen-resistant derivatives, TMX2–11 and TMX2–28, were analyzed using the Illumina HumanMethylation450 BeadChip. Normalizing against MCF-7 values, ERα-positive TMX2–11 had 4000 hypermethylated sites and ERα-negative TMX2–28 had over 33 000. Analysis of CpG sites altered in both TMX2–11 and TMX2–28 revealed that the Tamoxifen-resistant cell lines share 3000 hypermethylated and 200 hypomethylated CpGs. ZNF350 and MAGED1, two genes hypermethylated in both cell lines, were examined in greater detail. Treatment with 5-aza-2′deoxycitidine caused a significant reduction in promoter methylation of both ZNF350 and MAGED1 and a corresponding increase in expression in TMX2–28. A similar relationship between methylation and expression was not detected in TMX2–11. Our findings are indicative of the variable responses to methylation-targeted breast cancer therapy and highlight the need for biomarkers that accurately predict treatment outcome.     

MicroRNA expression profiling of endocrine sensitive and resistant breast cancer cell lines

BackgroundMicroRNAs (miRs) regulate gene expression through translation inhibition of target mRNAs. One of the most promising approaches for cancer therapy is through mimicking or antagonizing the action of miRs. In this report, we analyzed the miRnome profile of several human breast cancer cell lines to determine the influence of estrogen receptor (ER) silencing previously shown to result in epithelial to mesenchymal transition (EMT) and enhanced tumor invasion.MethodsMicroRNA extracted from MDA-MB-231 (de novo ER-) and ER-silenced (acquired ER-) pII and IM-26 or ER-expressing (YS1.2) siRNA transfected derivatives of MCF7 cells was deep sequenced on Illumina NextSeq500. Respective miRnomes were compared with edgeR package in R and Venny2.1 and target prediction performed with miRTarBase. Mimics and inhibitors of selected differentially expressed miRs associated with EMT mediators (miR-200c-3p targeting ZEB1, miR-449a targeting δ-catenin and miR-29a-3p) were transfected into pII cells and mRNA targets, as well as E-cadherin and keratin 19 (epithelial and mesenchymal markers respectively) were measured using taqman PCR.ResultsEach cell line expressed about 20% of the total known human miRnome; There was a high degree of similarity between the 3 tested ER-lines. Out of these expressed miRs, 50–60% were significantly differentially expressed between ER- and ER + lines. Transfection of miR-200c-3p mimic into pII cells down regulated ZEB1 and vimentin, and increased E-cadherin and keratin 19 with accompanying morphological changes, and reduced cell motility, reflecting a reversal back into an epithelial phenotype. On the other hand, transfecting pII with miR-449a inhibitor reduced cell invasion but did not induce EMT. Transfecting pII cell line with the mimic or inhibitor of miR-29a-3p showed no change in EMT markers or cell invasion suggesting that the EMT induced by loss of ER function can be reversed by blocking some but not just any random EMT-associated genes.ConclusionsThese data suggest that differences in miR expression can be exploited not only as mediators (using mimics) and targets (using miR antagonists) for general cancer therapies aimed at regulating either individual or multiple mRNAs, but also to re-sensitize endocrine resistant breast cancers by turning them back into a type that will be susceptible to endocrine agents.     

Global expression profiling and pathway analysis of mouse mammary tumor reveals strain and stage specific dysregulated pathways in breast cancer progression

It is believed that the alteration of tissue microenvironment would affect cancer initiation and progression. However, little is known in terms of the underlying molecular mechanisms that would affect the initiation and progression of breast cancer. In the present study, we use two murine mammary tumor models with different speeds of tumor initiation and progression for whole genome expression profiling to reveal the involved genes and signaling pathways. The pathways regulating PI3K-Akt signaling and Ras signaling were activated in Fvb mice and promoted tumor progression. Contrastingly, the pathways regulating apoptosis and cellular senescence were activated in Fvb.B6 mice and suppressed tumor progression. We identified distinct patterns of oncogenic pathways activation at different stages of breast cancer, and uncovered five oncogenic pathways that were activated in both human and mouse breast cancers. The genes and pathways discovered in our study would be useful information for other researchers and drug development.     

Interaction of p14ARF with Brca1 in cancer cell lines and primary breast cancer

We report an association between p14ARF and Brca1 in which both proteins co-immunoprecipitate (co-IP) in DU145 cells. The N-terminal 64 residues of p14ARF encoded by exon 1beta are sufficient for this association. Inside the cell, ectopic p14ARF co-localizes with ectopic and endogenous Brca1 in A375 cells. Endogenous p14ARF co-localizes with endogenous Brca1 in DU145 cells but not in H1299 cells. Since p14ARF interacts with B23 in the nucleolus, Brca1 co-localizes with B23 in DU145 but not in H1299 cells. While ectopic ARF potently inhibited DU145 cell proliferation, it had no effect on the proliferation of H1299 cells, suggesting that the interaction between ARF and Brca1 contributes to ARF-mediated tumor suppression. Consistent with this notion, ectopic p14ARF modulates endogenous Brca1 expression in MCF7 breast cancer cells and p14ARF co-localizes with Brca1 in normal breast epithelial cells. This co-localization is enhanced in primary breast cancer. Taken together, the results show that p14ARF associates with Brca1, which may play a major role in tumor suppression.     

乳腺癌细胞肿瘤标记物表达及其与临床病理特征相关性研究

目的 探讨肿瘤标记物14-3-3σ、Akt 和p27Kip1 蛋白在乳腺癌中的表达及其与临床病理特征及Her-2 的相关性.方法 选取43 份乳腺癌石蜡标本和10 份正常乳腺组织标本,采用免疫组织化学技术(SABC)检测组织中14-3-3σ、Akt 和p27Kip1 蛋白的表达,结合临床资料和随访资料,进行回顾性研究,...     

UCH-L1在乳腺癌中的表达及其与转移关系的研究

目的研究泛素羧基末端水解酶L1(UCH-L1)与磷酸化p38(p-p38)在乳腺癌组织、细胞系中的表达情况、两种蛋白的表达与临床病理特征的关系以及UCH-L1与乳腺癌侵袭转移的关系。方法用免疫组织化学方法检测乳腺癌组织中UCH-L1与p-p38蛋白的表达情况,用Western Blot方法检测乳腺癌组织以及细胞系中UCH-L1与p-p38蛋白的表达情况。应用UCH-L1特异性抑制剂作用于乳腺癌高侵袭高转移细胞系MDA-MB-435s后,用Western Blot观察UCH-L1与p-p38蛋白表达改变的情况,用Transwell实验检测MDA-MB-435s细胞侵袭潜能的改变。结果 UCH-L1和p-p38蛋白在乳腺浸润性导管癌中的表达高于其在癌旁正常乳腺组织中的表达(P=0.012,P=0.001),二者呈正相关(r=0.397,P=0.000),并与乳腺癌的TNM分期(P=0.017,P=0.010)、淋巴结转移情况(P=0.033,P=0.021)相关。乳腺上皮细胞系MCF-10A、乳腺癌低侵袭低转移细胞系MCF-7和乳腺癌高侵袭高转移细胞系MDA-MB-435s中两种蛋白表达水平呈递增趋势(P均<0.05)。UCH-L1特异性抑制剂可以浓度依赖性地下调MDA-MB-435s细胞系中p-p38蛋白的表达水平(P均<0.05),并能抑制乳腺癌细胞的侵袭转移潜能。结论 UCH-L1、p-p38过表达与乳腺癌的TMN分期、淋巴结转移有关。UCH-L1可能通过上调p-p38介导乳腺癌转移。     

Global genome splicing analysis reveals an increased number of alternatively spliced genes with aging

Alternative splicing (AS) is a key regulatory mechanism for the development of different tissues; however, not much is known about changes to alternative splicing during aging. Splicing events may become more frequent and widespread genome‐wide as tissues age and the splicing machinery stringency decreases. Using skin, skeletal muscle, bone, thymus, and white adipose tissue from wild‐type C57BL6/J male mice (4 and 18 months old), we examined the effect of age on splicing by AS analysis of the differential exon usage of the genome. The results identified a considerable number of AS genes in skeletal muscle, thymus, bone, and white adipose tissue between the different age groups (ranging from 27 to 246 AS genes corresponding to 0.3–3.2% of the total number of genes analyzed). For skin, skeletal muscle, and bone, we included a later age group (28 months old) that showed that the number of alternatively spliced genes increased with age in all three tissues (P < 0.01). Analysis of alternatively spliced genes across all tissues by gene ontology and pathway analysis identified 158 genes involved in RNA processing. Additional analysis of AS in a mouse model for the premature aging disease Hutchinson–Gilford progeria syndrome was performed. The results show that expression of the mutant protein, progerin, is associated with an impaired developmental splicing. As progerin accumulates, the number of genes with AS increases compared to in wild‐type skin. Our results indicate the existence of a mechanism for increased AS during aging in several tissues, emphasizing that AS has a more important role in the aging process than previously known.     

Androgen-induced human breast cancer cell proliferation is mediated by discrete mechanisms in estrogen receptor-α-positive and -negative breast cancer cells

Androgens have important physiological effects in women. Not only are they the precursor hormones for estrogen biosynthesis in the ovaries and extragonadal tissues, but also act directly via androgen receptors (ARs) throughout the body. Studies of the role of androgens on breast cancer development are controversial and the mechanisms involved are not fully understood. In this report we demonstrate that a non-aromatizable androgen metabolite, dihydrotestosterone (DHT), stimulated cell proliferation in vitro of both estrogen receptor-α (ER-α)-positive MCF-7 cells and ER-α-negative MDA-MB-231 human breast cancer cells. A contribution of ER to the proliferative effect of DHT in MCF-7 cells was supported by actions of small interfering RNA (siRNA) ER-α transfection and of the specific inhibitor of ER, ICI 182,780 to block DHT-induced proliferation. A contribution of the possible conversion of DHT to androstane-3α, 17β-diol was not excluded in these MCF-7 cell studies. In MDA-MB-231 cells, a novel mechanism was implicated, in that anti-integrin αvβ3 or an Arg-Gly-Asp (RGD) peptide targeted at a small molecule binding domain of the integrin eliminated the DHT effect on cell proliferation. Anti-integrin αvβ3 did not affect DHT action on MCF-7 cells. A contribution from classical androgen receptor to the DHT effect in each cell line was excluded. A proliferative DHT signal is transduced in both ER-α-positive and ER-α-negative breast cancer cells, but by discrete mechanisms.     

Expression of nuclear XIAP associates with cell growth and drug resistance and confers poor prognosis in breast cancer

Evasion from apoptosis is one of the hallmarks of cancer. X-linked inhibitor of apoptosis protein (XIAP) is known to modulate apoptosis by inhibiting caspases and ubiquitinating target proteins. XIAP is mainly found at the cytoplasm, but recent data link nuclear XIAP to poor prognosis in breast cancer. Here, we generated a mutant form of XIAP with a nuclear localization signal (XIAP^NLS-C-term) and investigated the oncogenic mechanisms associated with nuclear XIAP in breast cancer. Our results show that cells overexpressing XIAP^ΔRING (RING deletion) and XIAP^NLS-C-term exhibited XIAP nuclear localization more abundantly than XIAP^wild-type. Remarkably, overexpression of XIAP^NLS-C-term, but not XIAP^ΔRING, conferred resistance to doxorubicin and increased cellular proliferative capacity. Interestingly, Survivin and c-IAP1 expression were not associated with XIAP oncogenic effects. However, NFκB expression and ubiquitination of K63, but not K48 chains, were increased following XIAP^NLS-C-term overexpression, pointing to nuclear signaling transduction. Consistently, multivariate analysis revealed nuclear, but not cytoplasmic XIAP, as an independent prognostic factor in hormone receptor-negative breast cancer patients. Altogether, our findings suggest that nuclear XIAP confers poor outcome and RING-associated breast cancer growth and chemoresistance.     

EGFR inhibition by pentacyclic triterpenes exhibit cell cycle and growth arrest in breast cancer cells

Aims

Pentacyclic triterpenes are a group of molecules with promising anticancer potential, although their precise molecular target remains elusive. The current work aims to investigate the antiproliferative and associated mechanisms of triterpenes in breast cancer cells in vitro.

Main methods

Effect of triterpenes on cell cycle distribution, ROS and key regulatory proteins were analyzed in three breast cancer cells in vitro. Growth inhibition, new DNA synthesis, colony formation assays and Western blot analysis were performed to assess the EGFR inhibitory effect of triterpenes. Molecular docking was performed to study the interaction between EGFR and triterpenes.

Key findings

We have demonstrated the ability of dimethyl melaleucate (DMM), a pentacyclic triterpene to exhibit cell cycle arrest at G0/G1 phase by down-regulation of cyclin D1 through PI3K/AKT inhibition. Further, to identify the upstream target of DMM, potential EGFR inhibitory activity of DMM and three structurally related pentacyclic triterpenes, ursolic acid, 18α-glycyrrhetinic acid and carbenoxolone was investigated. Interestingly, pentacyclic triterpenes limit EGF mediated breast cancer proliferation through sustained inhibition of EGFR and its downstream effectors STAT3 and cyclin D1 in breast cancer lines. We also show pentacyclic triterpenes to bind at the ATP binding pocket of tyrosine kinase domain of EGFR leading to the hypothesis that pentacyclic triterpenes could be a novel class of EGFR inhibitors. In conclusion, pentacyclic triterpenes inhibit EGFR activation through binding with tyrosine kinase domain thereby suppressing breast cancer proliferation.

Significance

Pentacyclic triterpenes may serve as a potential platform for development of novel drugs against breast cancer.     

Assessment of surveillance versus etiologic factors in the reciprocal association between papillary thyroid cancer and breast cancer

BackgroundMutually increased risks for thyroid and breast cancer have been reported, but the contribution of etiologic factors versus increased medical surveillance to these associations is unknown.MethodsLeveraging large-scale US population-based cancer registry data, we used standardized incidence ratios (SIRs) to investigate the reciprocal risks of thyroid and breast cancers among adult females diagnosed with a first primary invasive, non-metastatic breast cancer (N = 652,627) or papillary thyroid cancer (PTC) (N = 92,318) during 2000–2017 who survived ≥1-year.ResultsPTC risk was increased 1.3-fold [N = 1434; SIR = 1.32; 95 % confidence interval (CI) = 1.25–1.39] after breast cancer compared to the general population. PTC risk declined significantly with time since breast cancer (Poisson regression = P_trend <0.001) and was evident only for tumors ≤2 cm in size. The SIRs for PTC were higher after hormone-receptor (HR)+ (versus HR-) and stage II or III (versus stage 0-I) breast tumors. Breast cancer risk was increased 1.2-fold (N = 2038; SIR = 1.21; CI = 1.16–1.26) after PTC and was constant over time since PTC but was only increased for stage 0-II and HR + breast cancers.ConclusionAlthough some of the patterns by latency, stage and size are consistent with heightened surveillance contributing to the breast-thyroid association, we cannot exclude a role of shared etiology or treatment effects.     

Tepoxalin increases chemotherapy efficacy in drug-resistant breast cancer cells overexpressing the multidrug transporter gene ABCB1

Effective cancer chemotherapy treatment requires both therapy delivery and retention by malignant cells. Cancer cell overexpression of the multidrug transmembrane transporter gene ABCB1 (MDR1, multi-drug resistance protein 1) thwarts therapy retention, leading to a drug-resistant phenotype. We explored the phenotypic impact of ABCB1 overexpression in normal human mammary epithelial cells (HMECs) via acute adenoviral delivery and in breast cancer cell lines with stable integration of inducible ABCB1 expression. One hundred sixty-two genes were differentially expressed between ABCB1-expressing and GFP-expressing HMECs, including the gene encoding the cyclooxygenase-2 protein, PTGS2. Several breast cancer cell lines with inducible ABCB1 expression demonstrated sensitivity to the 5-lipoxygenase, cyclooxygenase-1/2 inhibitor tepoxalin in two-dimensional drug response assays, and combination treatment of tepoxalin either with chemotherapies or with histone deacetylase (HDAC) inhibitors improved therapeutic efficacy in these lines. Moreover, selection for the ABCB1-expressing cell population was reduced in three-dimensional co-cultures of ABCB1-expressing and GFP-expressing cells when chemotherapy was given in combination with tepoxalin. Further study is warranted to ascertain the clinical potential of tepoxalin, an FDA-approved therapeutic for use in domesticated mammals, to restore chemosensitivity and improve drug response in patients with ABCB1-overexpressing drug-resistant breast cancers.     

Inhibition of breast cancer growth via miR-7 suppressing ALDH1A3 activity concomitant with decreasing breast cancer stem cell subpopulation

Breast cancer patients with high expression of aldehyde dehydrogenases (ALDHs) cell population have higher tolerability to chemotherapy since the cells posses a characteristic of breast cancer stem cells (BCSCs) that are resistant to conventional chemotherapy. In this study, we found that the ALDH-positive cells were higher in CD44⁺CD24⁻ and CD44⁺CD24⁻ESA⁺BCSCs than that in both BT549 and MDA-MB-231 cell lines but microRNA-7 (miR-7) level was lower in CD44⁺CD24⁻ and CD44⁺CD24⁻ESA⁺BCSCs than that in MDA-MB-231 cells. Moreover, miR-7 overexpression in MDA-MB-231 cells decreased ALDH1A3 activity by miR-7 directly binding to the 3′-untranslated region of ALDH1A3; while the ALDH1A3 expression was downregulated in MDA-MB-231 cells, the expressions of CD44 and Epithelium Specific Antigen (ESA) were reduced along with decreasing the BCSC subpopulation. Significantly, enforced expression of miR-7 in CD44⁺CD24⁻ESA⁺BCSC markedly inhibited the BCSC-driven xenograft growth in mice by decreasing an expression of ALDH1A3. Collectively, the findings demonstrate the miR-7 inhibits breast cancer growth via suppressing ALDH1A3 activity concomitant with decreasing BCSC subpopulation. This approach may be considered for an investigation on clinical treatment of breast cancers.