Impact of decitabine on immunohistochemistry expression of the putative tumor suppressor genes FHIT, WWOX, FUS1 and PTEN in clinical tumor samples

Stochastic demethylation and redundant epigenetic suppressive mechanisms generate highly heterogeneous responses to pharmacological DNA methyltransferase inhibition

BACKGROUND

Despite promising preclinical studies, the application of DNA methyltransferase inhibitors in treating patients with solid cancers has thus far produced only modest outcomes. The presence of intratumoral heterogeneity in response to DNA methyltransferase inhibitors could significantly influence clinical efficacy, yet our understanding of the single-cell response to these drugs in solid tumors remains very limited.

METHODS

In this study, we used cancer/testis antigen genes as a model for methylation-dependent gene expression to examine the activity of DNA methyltransferase inhibitors and their potential synergistic effect with histone deacetylase inhibitors at the single-cancer cell level. The analysis was performed on breast cancer patient-derived xenograft tumors and cell lines, employing a comprehensive set of techniques, including targeted single-cell mRNA sequencing. Mechanistic insights were further gained through DNA methylation profiling and chromatin structure analysis.

RESULTS

We show that breast cancer tumors and cell cultures exhibit a highly heterogenous response to DNA methyltransferase inhibitors, persisting even under high drug concentrations and efficient DNA methyltransferase depletion. The observed variability in response to DNA methyltransferase inhibitors was independent of cancer-associated aberrations and clonal genetic diversity. Instead, these variations were attributed to stochastic demethylation of regulatory CpG sites and the DNA methylation-independent suppressive function of histone deacetylases.

CONCLUSIONS

Our findings point to intratumoral heterogeneity as a limiting factor in the use of DNA methyltransferase inhibitors as single agents in treatment of solid cancers and highlight histone deacetylase inhibitors as essential partners to DNA methyltransferase inhibitors in the clinic.

Exosomal circRNA BTG2 derived from RBP-J overexpressed-macrophages inhibits glioma progression via miR-25-3p/PTEN

Macrophage-derived exosomes (Mφ-Exos) are involved in tumor progression, but its role in glioma is not fully understood. RBP-J is related to macrophage activation. In this study, we assess the role of exosomes derived from RBP-J-overexpressed macrophages (RBP-J OE Mφ-Exos) in glioma. The circular RNA (circRNA) profiles in RBP-J OE Mφ-Exos and THP-1-like macrophages (WT Mφ)-Exos were evaluated using circRNA microarray. Then the functions of Mφ-Exo-circRNA in glioma cells were assessed via CCK-8, EdU, Transwell invasion, and nude mouse assays. Besides, luciferase reporter assay, RNA immunoprecipitation, and Pearson's correlation analysis were adopted to confirm interactions. We found that circRNA BTG (circBTG2) is upregulated in RBP-J OE Mφ-Exos compared to WT Mφ-Exos. RBP-J OE Mφ-Exos co-culture and circBTG2 overexpression inhibited proliferation and invasion of glioma cells, whereas circBTG2 knockdown promotes tumor growth in vivo. The effects of RBP-J OE Mφ-Exos on glioma cells can be reversed by the circBTG2 knockdown. In conclusions, Exo-circBTG2 secreted from RBP-J OE Mφ inhibits tumor progression through the circBTG2/miR-25-3p/PTEN pathway, and circBTG2 is probably a diagnostic biomarker and potential target for glioma therapy.

High Histone Deacetylase 2/3 Expression in Non-Functioning Pituitary Tumors

Epigenetic modification of chromatin is involved in non-malignant pituitary neoplasia by causing abnormal expression of tumor suppressors and oncogenes. These changes are potentially reversible, suggesting the possibility of targeting tumor cells by restoring the expression of epigenetically silenced tumor suppressors. The role of the histone deacetylase (HDAC) family in pituitary tumorigenesis is not known. We report that HDAC2 and 3, Class I HDAC members, are highly expressed in clinically non-functioning pituitary adenomas (NFPAs) compared to normal pituitary (NP) samples as determined by RT-PCR and immunohistochemical staining (IHC). Treatment of a human NFPA derived folliculostellate cell line, PDFS, with the HDAC3 inhibitor RGFP966 for 96 hours resulted in inhibition of cell proliferation by 70%. Furthermore, the combination of RGFP966 with a methyltransferase/DNMT inhibitor, 5’-aza-2’-deoxycytidine, led to the restoration of the expression of several tumor suppressor genes, including STAT1, P16, PTEN, and the large non-coding RNA tumor suppressor MEG3, in PDFS cells. Our data support the hypothesis that both histone modification and DNA methylation are involved in the pathogenesis of human NFPAs and suggest that targeting HDACs and DNA methylation can be incorporated into future therapies.

microRNA-664 enhances proliferation, migration and invasion of lung cancer cells

Altered microRNA (miR) expression serves an important role in the development and progression of lung cancer. In the present study, the effect of miR-664 on proliferation, migration and invasion of lung cancer cells was assessed. The proliferation of lung cancer cells with an overexpression of miR-664 was examined via MTT assay. The Caspase-Glo3/7 assay was used to examine the effect of miR-664 on cisplatin-induced apoptosis in lung cancer cells. The migration and invasion of lung cancer cells were assessed by Transwell migration and matrigel invasion assays. Western blot analysis was used to examine the protein expression levels. miR-664 improved the proliferation of lung cancer cells and inhibited cisplatin-induced apoptosis of A549 and A427 cells. Furthermore, altered expression of miR-664 affected migration and invasion of lung cancer cells. In addition, a miR-664 mimic decreased E-cadherin expression and increased vementin and Snail expression in lung cancer cells. Notably, the expression level of protein kinase B in A549 cells was changed following altered expression of miR-664. The results of the present study suggest that miR-664 serves an essential role in tumor development and progression in lung cancer.

Expression of PTEN and KAI1 tumor suppressor genes in pancreatic carcinoma and its association with different pathological factors

Pancreatic carcinoma is a common cancer type with a poor prognosis. The aim of the present study was to examine the expression of tumor suppressor genes phosphatase and tensin homolog deleted in chromosome 10 (PTEN) and KAI1 in pancreatic carcinoma and its association with clinical pathological factors. A total of 50 hospitalized cases of pancreatic cancer including 28 males and 22 females aged 31-82 years were included in the present study. Ten cases of normal pancreatic tissue were obtained from cadavers and served as the controls. The pancreatic specimens were embedded in paraffin blocks and slides were prepared for immunohistochemical analysis to determine the expression of PTEN and KAI1 in normal pancreatic tissue and pancreatic carcinoma samples. The positive expression rate of PTEN in the normal pancreatic tissue was higher than that in pancreatic carcinoma (P<0.05), while the positive expression rate of KAI1 in the normal pancreatic tissue was lower than that in pancreatic carcinoma (P<0.05). Pathological factors such as clinical stage of disease, histological grade and the presence or absence of lymphatic metastasis significantly affected the expression of PTEN and KAI1 (P<0.05). In conclusion, the positive expression of PTEN and KAI1 in pancreatic carcinoma is closely associated with the development of pancreatic carcinoma.

MicroRNA-17-5p induces drug resistance and invasion of ovarian carcinoma cells by targeting PTEN signaling

Background

The miR-17-5p was overexpressed in ovarian cancer cells, and those cells were treated with paclitaxel. The proliferation of ovarian cancer cells was assessed by MTT assay. The Caspase-Glo3/7 and TUNEL assay were used to examine the effect of miR-17-5p on paclitaxel-induced apoptosis in ovarian cancer cells. The migration and invasion of ovarian cancer cells were analyzed by BD matrigel assays. Western blot was performed to evaluate the expression of apoptotic proteins and epithelial-mesenchymal transition markers in ovarian cancer cells.

Results

The survival rate of ovarian cancer cells was increased after overexpression of miR-17-5p. The apoptosis decreased in miR-17-5p overexpressed ovarian cancer cells. Altered miR-17-5p expression affected migration and invasion of ovarian cancer cells. The overexpression of miR-17-5p altered the expression of EMT markers. miR-17-5p activates AKT by downregulation of PTEN in ovarian cancer cells.

Conclusion

Our results indicate that miR-17-5p might serve as potential molecular therapeutic target.

The clinicopathological significance and drug target potential of FHIT in breast cancer, a meta-analysis and literature review

FHIT is a bona fide tumor-suppressor gene and its loss contributes to tumorigenesis of epithelial cancers including breast cancer (BC). However, the association and clinicopathological significance between FHIT promoter hypermethylation and BC remains unclear. The purpose of this study is to conduct a meta-analysis and literature review to investigate the clinicopathological significance of FHIT methylation in BC. A detailed literature search was performed in PubMed, EMBASE, Web of Science, and Google Scholar databases. The data were extracted and assessed by two reviewers independently. Odds ratios with 95% corresponding confidence intervals were calculated. A total of seven relevant articles were available for meta-analysis, which included 985 patients. The frequency of FHIT hypermethylation was significantly increased in invasive ductal carcinoma compared to benign breast disease, the pooled odds ratio was 8.43, P<0.00001. The rate of FHIT hypermethylation was not significantly different between stage I/II and stage III/IV, odds ratio was 2.98, P=0.06. In addition, FHIT hypermethylation was not significantly associated with ER and PR status. FHIT hypermethylation was not significantly correlated with premenopausal and postmenopausal patients with invasive ductal carcinoma. In summary, our meta-analysis indicated that the frequency of FHIT hypermethylation was significantly increased in BC compared to benign breast disease. The rate of FHIT hypermethylation in advanced stages of BC was higher than in earlier stages; however, the difference was not statistically significant. Our data suggested that FHIT methylation could be a diagnostic biomarker of BC carcinogenesis. FHIT is a potential drug target for development of demethylation treatment for patients with BC.