Epigenetics: Mechanisms, potential roles, and therapeutic strategies in cancer progression.

Mutations or abnormal expression of oncogenes and tumor suppressor genes are known to cause cancer. Recent studies have shown that epigenetic modifications are key drivers of cancer development and progression. Nevertheless, the mechanistic role of epigenetic dysregulation in the tumor microenvironment is not fully understood. Here, we reviewed the role of epigenetic modifications of cancer cells and non-cancer cells in the tumor microenvironment and recent research advances in cancer epigenetic drugs. In addition, we discussed the great potential of epigenetic combination therapies in the clinical treatment of cancer. However, there are still some challenges in the field of cancer epigenetics, such as epigenetic tumor heterogeneity, epigenetic drug heterogeneity, and crosstalk between epigenetics, proteomics, metabolomics, and other omics, which may be the focus and difficulty of cancer treatment in the future. In conclusion, epigenetic modifications in the tumor microenvironment are essential for future epigenetic drug development and the comprehensive treatment of cancer. Epigenetic combination therapy may be a novel strategy for the future clinical treatment of cancer.

A high AR:ERα or PDEF:ERα ratio predicts a sub-optimal response to tamoxifen therapy in ERα-positive breast cancer.

PURPOSE: Approximately 30% oestrogen receptor alpha (ERα)-positive breast cancer (BC) patients exhibit intrinsic or recurrent resistance to adjuvant endocrine therapy with tamoxifen. The androgen receptor (AR) is expressed in about 90% of ERα-positive patients, with particularly high expression in tamoxifen-resistant tumours. Prostate-derived Ets factor (PDEF), which is a co-regulator of AR, plays a role in tamoxifen resistance in ERα-positive BC. The purpose of this research was to analyse the potential roles of AR, PDEF and ERα levels in the response to tamoxifen resistance in ERα-positive BC. METHODS: The nuclear AR:ERα and PDEF:ERα ratios were examined immunohistochemically in a cohort of 225 ERα-positive pre-menopausal BC patients who had received adjuvant tamoxifen therapy. RESULTS: For both AR:ERα and PDEF:ERα ratios, the optimal cutoff value was 2.0. Patients receiving adjuvant tamoxifen treatment who had a high AR:ERα (≥ 2.0) (HR = 3.90) or PDEF:ERα ratio (≥ 2.0) (HR = 2.77) had a beyond twofold increased risk of failure. Both the AR:ERα ratio (P = 0.001) and PDEF:ERα ratio (P = 0.002) were independently associated with the risk of tamoxifen treatment failure. Furthermore, both a high ratio of AR:ERα (≥ 2.0) and PDEF:ERα (≥ 2.0) were associated with shorter disease-free survival (DFS) and shorter disease-specific survival (DSS). In addition, both the AR:ERα ratio and PDEF:ERα ratio were independent predictors of DFS (both P < 0.0001) and DSS (P = 0.001 and P < 0.0001, respectively). CONCLUSIONS: AR:ERα and PDEF:ERα ratios are independent predictors of the response to conventional ERα-directed tamoxifen endocrine therapy.

Interrelation of androgen receptor and miR-30a and miR-30a function in ER-, PR-, AR+ MDA-MB-453 breast cancer cells.

The association between androgen-induced androgen receptor (AR) activating signal and microRNA (miR)-30a was investigated, as well as the function of miR-30a in estrogen receptor-negative (ER-), progesterone receptor-negative (PR-), and AR-positive (AR+) MDA-MB-453 breast cancer cells. Androgen-induced AR activating signal upregulated the expression of AR, and downregulated the expression of miR-30a, b and c. Bioinformatics analysis indicated a putative miR-30a, b and c binding site in the 3'-untranslated region of AR mRNA. It was confirmed that the AR gene is a direct target of miR-30a, whereas AR does not target the miR-30a promoter, and AR activating signal may indirectly downregulate miR-30a through other cell signaling pathways. In this positive feedback mechanism AR is then upregulated through miR-30a. Overexpression of miR-30a inhibited cell proliferation, whereas inhibition of miR-30a expression by specific antisense oligonucleotides, increased cell growth. Previously, androgen-induced AR activating signal was demonstrated to inhibit cell proliferation in ER-, PR- and AR+ MDA-MB-453 breast cancer cells, but AR activating signal downregulated the expression of miR-30a, relieving the inhibition of MDA-MB-453 cell growth. Therefore, in MDA-MB-453 breast cancer cells, miR-30a has two different functions regarding cell growth: Inhibition of cell proliferation through a positive feedback signaling pathway; and the relative promotion of cell proliferation through downregulation of miR-30a. Thus, the association between AR activating signal and microRNAs is complex, and microRNAs may possess different functions due to different signaling pathways. Although the results of the present study were obtained in one cell line, they contribute to subsequent studies on ER-, PR- and AR+ breast cancer.

Loss of FAT1 during the progression from DCIS to IDC and predict poor clinical outcome in breast cancer.

FAT1 and ß-catenin are important tumor regulatory factors. The aim of this study was to detect the possible disparity in their expression from ductal carcinoma in situ (DCIS) to invasive ductal carcinoma (IDC) and to explore its correlation with clinicopathological factors. We used immunohistochemistry to detect protein expression of FAT1 and ß-catenin in breast cancer tissues from 113 cases of DCIS and 149 cases of IDC. As compared with DCIS, expression of FAT1 and ß-catenin were significantly decreased in IDC (P<0.05). In addition, our study also revealed a correlation between their expression and some clinicopathological factors. We found that FAT1 expression was associated with nuclear grade and comedonecrosis (P<0.05) in DCIS, whereas FAT1 expression showed significant variation with histological grade and LN status (P<0.05) in IDC. Similar associations were observed in the ß-catenin subgroup. Furthermore, expressions of FAT1 and ß-catenin were correlated with each other in DCIS and IDC (P<0.05). FAT1(-), ß-catenin(-), or FAT1(-)/ß-catenin(-) may indicate worse DFS and OS in breast cancer (P<0.05). This study suggests that loss of FAT1 and ß-catenin are associated with breast cancer progression, aggressive behavior, and poor prognosis. FAT1 alone or together with ß-catenin might be a valuable biomarker in predicting the prognosis of patients with breast cancer.

Clinicopathologic characteristics and molecular subtypes of microinvasive carcinoma of the breast.

Patients with microinvasive carcinoma often have favorable prognosis, but it remains unclear whether this special type of breast cancer represents a distinct morphological entity with its own biological features and clinical behavior distinct from those of ductal carcinoma in situ (DCIS). The study is a retrospective analysis of a large patient cohort from a single institution. One hundred and thirty one microinvasive carcinoma and 451 DCIS cases were collected. ER, PR, HER2, and Ki67 were examined by immunohistochemistry in pathological sections. We assessed the clinicopathologic characteristics, molecular features, and survival status of microinvasive carcinoma and compared to those of DCIS. Microinvasive carcinoma differed from DCIS with respect to tumor size, lymph node status, and initial presentation (P < 0.05). There was a significant difference in nuclear grade among microinvasive carcinoma of different molecular subtype (P < 0.05). The clinicalpathologic features and outcomes of patients with microinvasive carcinoma were similar to those with DCIS. The 5-year OS rate for microinvasive carcinoma and DCIS patients was 99.0 and 99.2%, respectively. A combination of pathologic, clinical, and molecular factors may ultimately reveal more powerful and robust measures for disease classification than any one modality alone. Microinvasive carcinoma does not significantly predict for worse DFS or OS in comparison with patients with DCIS.

[Value of CK5/6, CK14, ER and PR detection in differential diagnosis of intraductal proliferative lesions of the breast].

OBJECTIVE: To investigate the expression of high-molecular-weight keratins CK5/6, CK14, estrogen receptor (ER) and progesterone receptor (PR) in differential diagnosis of simple ductal hyperplasia (UDH), atypical ductal hyperplasia (ADH) and low-grade ductal carcinoma in situ (low-grade DCIS) . METHODS: The clinicopathological data of twenty cases of atypical ductal epithelial hyperplasia (ADH) with focal cancerization changed into low-grade DCIS diagnosed at Tianjin Medical University Cancer Institute and Hospital between January 2013 and February 2014 were reviewed and analyzed. The expressions of CK5/6, CK14, ER and PR were detected by immunohistochemistry. RESULTS: Positive expressions of CK5/6 and CK14 were seen in UDH showing a mosaic pattern, while negative expression in ADH and low-grade DCIS. In addition, CK5/6 and CK14 were positively expressed in the myoepithelial cells of UDH, ADH and low-grade DCIS. Positive expressions of ER and PR were observed in UDH, ADH and low-grade DCIS. But they presented diffuse and homogeneous strong positive expression in ADH and variable positive expression in UDH. CONCLUSION: In the intraductal proliferative lesions of the breast, the use of combined detection of the expression of CK5/6, CK14, ER and PR is of practical significance in the differential diagnosis of UDH, ADH and low-grade DCIS.

Androgen receptor decreases CMYC and KRAS expression by upregulating let-7a expression in ER-, PR-, AR+ breast cancer.

It is generally known that the decision to use anti-estrogen therapy is based on the expression of estrogen and progesterone receptors in breast cancers. Recent studies have shown that androgen receptor (AR) is frequently expressed in ER-, PR- breast cancer and plays an important role in the prognosis of breast cancer patients. Furthermore, AR can increase the global expression of microRNAs, post-transcriptional gene regulators that play a crucial role in the initiation and progression of breast cancer. In this study, we investigated the functions and relations of AR, related miRNAs and target proteins in ER-, PR-, AR+ breast cancer. The results showed that androgen-induced AR activating signal directly upregulates let-7a expression, downregulates CMYC and KRAS protein expression, and inhibits cell proliferation in ER-, PR-, AR+ breast cancer cells. Overexpression of let-7a inhibits cell proliferation and downregulates CMYC and KRAS protein expression, whereas inhibition of let-7a expression by specific antisense oligonucleo-tides increases cell growth and upregulates CMYC and KRAS protein expression. We performed in situ hybridization for let-7a and immunohistochemical staining for CMYC and KRAS using sequential sections obtained from surgically-resected breast cancer tissues and observed an inverse correlation between the staining pattern of let-7a and its target proteins. Androgen-induced AR activating signal upregulates let-7a that targets CMYC and KRAS and contributes to ER-, PR-, AR+ breast cancer pathogenesis. Elucidation of this pathway will help develop new therapies.