The loss-of-function of DNA methyltransferase 1 by siRNA impairs the growth of non-small cell lung cancer with alleviated side effects via reactivation of RASSF1A and APC in vitro and vivo

Histone methyltransferase SETD1A participates in lung cancer progression

Lung cancer is the leading cause of cancer‐related death worldwide, with an estimated 1.2 million deaths each year. Despite advances in lung cancer treatment, 5‐year survival rates are lower than ~15%, which is attributes to diagnosis limitations and current clinical drug resistance. Recently, more evidence has suggested that epigenome dysregulation is associated with the initiation and progress of cancer, and targeting epigenome‐related molecules improves cancer symptoms. Interestingly, some groups reported that the level of methylation of histone 3 lysine 4 (H3K4me3) was increased in lung tumors and participated in abnormal transcriptional regulation. However, a mechanistic analysis is not available. In this report, we found that the SET domain containing 1A (SETD1A), the enzyme for H3K4me3, was elevated in lung cancer tissue compared to normal lung tissue. Knockdown of SETD1A in A549 and H1299 cells led to defects in cell proliferation and epithelial‐mesenchymal transition (EMT), as evidenced by inhibited WNT and transforming growth factor β (TGFβ) pathways, compared with the control group. Xenograft assays also revealed a decreased tumor growth and EMT in the SETD1A silenced group compared with the control group. Mechanistic analysis suggested that SETD1A might regulate tumor progression via several critical oncogenes, which exhibited enhanced H3K4me3 levels around transcriptional start sites in lung cancer. This study illustrates the important role of SETD1A in lung cancer and provides a potential drug target for treatment.

Targeting Epigenetics in Lung Cancer

The epigenetic landscape, which in part includes DNA methylation, chromatin organization, histone modifications, and noncoding RNA regulation, greatly contributes to the heterogeneity that makes developing effective therapies for lung cancer challenging. This review will provide an overview of the epigenetic alterations that have been implicated in all aspects of cancer pathogenesis and progression as well as summarize clinical applications for targeting epigenetics in the treatment of lung cancer.

Resistance to Targeted Therapy and RASSF1A Loss in Melanoma: What Are We Missing?

Melanoma is one of the most aggressive forms of skin cancer and is therapeutically challenging, considering its high mutation rate. Following the development of therapies to target BRAF, the most frequently found mutation in melanoma, promising therapeutic responses were observed. While mono- and combination therapies to target the MAPK cascade did induce a therapeutic response in BRAF-mutated melanomas, the development of resistance to MAPK-targeted therapies remains a challenge for a high proportion of patients. Resistance mechanisms are varied and can be categorised as intrinsic, acquired, and adaptive. RASSF1A is a tumour suppressor that plays an integral role in the maintenance of cellular homeostasis as a central signalling hub. RASSF1A tumour suppressor activity is commonly lost in melanoma, mainly by aberrant promoter hypermethylation. RASSF1A loss could be associated with several mechanisms of resistance to MAPK inhibition considering that most of the signalling pathways that RASSF1A controls are found to be altered targeted therapy resistant melanomas. Herein, we discuss resistance mechanisms in detail and the potential role for RASSF1A reactivation to re-sensitise BRAF mutant melanomas to therapy.

Targeting DNA methyltransferases in non-small-cell lung cancer

Despite the advances in treatment using chemotherapy or targeted therapies, due to static survival rates, non-small cell lung cancer (NSCLC) is the major cause of cancer-related deaths worldwide. Epigenetic-based therapies have been developed for NSCLC by targeting DNA methyltransferases (DNMTs) and histone-modifying enzymes. However, treatment using single epigenetic agents on solid tumours has been inadequate; whereas, treatment with a combination of DNMTs inhibitors with chemotherapy and immunotherapy has shown great promise. Dietary sources of phytochemicals could also inhibit DNMTs and cancer stem cells, representing a novel and promising way to prevent and treat cancer. Herein, we will discuss the different DNMTs, DNA methylation profiling in NSCLC as well as current demethylating agents in ongoing clinical trials. Therefore, providing a concise overview of future developments in the field of epigenetic therapy in NSCLC.

Methylation of RILP in lung cancer promotes tumor cell proliferation and invasion

Rab-interacting lysosomal protein (RILP) has been suggested to perform as a tumor suppressor in breast and prostate cancer cell lines. However, its expression profile and functional role in lung cancer have never been investigated. We applied the well-established cancer genomic database-The Cancer Genome Atlas to compare the RILP expression and methylation between lung cancer tissues and normal tissues. The potential correlation of RILP with clinical characteristics of lung cancer patients (e.g., stages, smoking, TP53, and methylation) was also be explored. Our results showed that the downregulation of RILP and upregulation of RILP methylation were identified in lung cancer tissues compared to normal healthy tissues. Downregulation of RILP was positively associated with lung cancer later stage (N3), smoking history, TP53 mutation, and poor prognosis, as well as inversely correlated with DNA (cytosine-5)-methyltransferase 1 (DNMT1) expression. Demethylation treatment enhanced RILP expression in lung cancer cells, suggesting hypermethylation is responsible for RILP silencing in lung cancer. We further found that RILP depletion promoted lung cancer cell proliferation, migration, and invasion. We concluded that RILP acts as a tumor suppressor in lung cancer cells. Our results provided the theoretical basis for developing RILP-targeting or demethylating agents for lung cancer treatment.

RASSF1A: A promising target for the diagnosis and treatment of cancer

The Ras association domain family 1 isoform A (RASSF1A), a tumor suppressor, regulates several tumor-related signaling pathways and interferes with diverse cellular processes. RASSF1A is frequently demonstrated to be inactivated by hypermethylation in numerous types of solid cancers. It is also associated with lymph node metastasis, vascular invasion, and chemo-resistance. Therefore, reactivation of RASSF1A may be a viable strategy to block tumor progress and reverse drug resistance. In this review, we have summarized the clinical value of RASSF1A for screening, staging, and therapeutic management of human malignancies. We also highlighted the potential mechanism of RASSF1A in chemo-resistance, which may help identify novel drugs in the future.

Decitabine reverses gefitinib resistance in PC9 lung adenocarcinoma cells by demethylation of RASSF1A and GADD45β promoter

The acquired resistance to epidermal growth factor receptor tyrosine kinase inhibitor (EGFR-TKI) is the major reason for the failure of target therapy in advanced non small cell lung cancer (NSCLC) patients, the mechanism of which has not been fully elucidated yet. The present study aimed to investigate the different DNA methylation profile before and after acquired EGFR-TKI resistance, and explore the influence of the DNA demethylater, decitabine, on EGFR-TKI resistance. The DNA methylation chip was used to screen the genes whose DNA methylation status were changed in the EGFR-TKI sensitive human NSCLC cell line PC9, and the induced EGFR-TKI resistant NSCLC cell line PC9/GR (harboring T790M mutation). According to the results and literature reports, the tumor suppressor genes, RASSF1A and GADD45β were selected for further research. Methylation specific PCR (MSP) and western blot further confirmed that the promoters of these two genes were methylated, and the protein expressions were significantly inhibited in PC9/GR cells. Additionally, decitabine, the DNA methyl transferase inhibitor, could reverse the methylation status of RASSF1A and GADD45β promoters, elevate protein expression, and partially restore the sensitivity of PC9/GR cells to EGFR-TKI. To conclude, our results suggested that the DNA methylation of RASSF1 and GADD45β may play a role in EGFR-TKI resistance, and epigenetic intervention might be an effective strategy to reverse EGFR-TKI resistance, suggesting further study.

The repression and reciprocal interaction of DNA methyltransferase 1 and specificity protein 1 contributes to the inhibition of MET expression by the combination of Chinese herbal medicine FZKA decoction and erlotinib

ETHNOPHARMACOLOGICAL RELEVANCE

The Chinese herbal medicine Fuzheng Kang-Ai (FZKA) decoction obtained from Guangdong Kangmei Pharmaceutical Company, which contains 12 components with different types of constituents, has been used as part of the adjuvant treatment of lung cancer for decades. We previously showed that FZKA decoction enhances the growth inhibition of epidermal growth factor receptor-tyrosine kinase inhibitor (EGFR-TKI)-resistant non-small cell lung cancer (NSCLC) cells by suppressing glycoprotein mucin 1 (MUC1) expression. However, the molecular mechanism underlying the therapeutic potential, particularly in sensitizing or/and enhancing the anti-lung cancer effect of EGFR-TKIs, remains unclear.

MATERIALS AND METHODS

Cell viability was measured using 3-(4, 5-diMEThylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) and 5-ethynyl -2'-deoxyuridine (EdU) assays. Western blot analysis was performed to examine the protein expressions of DNA methyltransferase 1 (DNMT1), specificity protein 1 (SP1), and MET, an oncogene encoding for a trans-membrane tyrosine kinase receptor activated by the hepatocyte growth factor (HGF). The expression of MET mRNA was measured by quantitative real-time PCR (qRT-PCR). Exogenous expression of DNMT1 and SP1, and MET were carried out by transient transfection assays. The promoter activity of MET was tested using Dual-luciferase reporter assays. A nude mouse xenografted tumor model further evaluated the effect of the combination of FZKA decoction and erlotinib in vivo.

RESULTS

The combination of FZKA and erlotinib produced an even greater inhibition of NSCLC cell growth. FZKA decreased the expressions of DNMT1, SP1, and MET (c-MET) proteins, and the combination of FZKA and erlotinib demonstrated enhanced responses. Interestingly, there was a mutual regulation of DNMT1 and SP1. In addition, exogenously expressed DNMT1 and SP1 blocked the FZKA-inhibited c-MET expression. Moreover, excessive expressed MET neutralized FZKA-inhibited growth of NSCLC cells. FZKA decreased the mRNA and promoter activity of c-MET, which was not observed in cells with ectopic expressed DNMT1 gene. Similar findings were observed in vivo.

CONCLUSION

FZKA decreases MET gene expression through the repression and mutual regulation of DNMT1 and SP1 in vitro and in vivo. This leads to inhibit the growth of human lung cancer cells. The combination of FZKA and EGFR-TKI erlotinib exhibits synergy in this process. The regulatory loops among the DNMT1, SP1 and MET converge in the overall effects of FZKA and EGFR-TKI erlotinib. This in vitro and in vivo study clarifies an additional novel molecular mechanism underlying the anti-lung cancer effects in response to the combination of FZKA and erlotinib in gefitinib-resistant NSCLC cells.

Promoter methylation as biomarkers for diagnosis of melanoma: A systematic review and meta-analysis

Melanoma is one of the most common skin cancer that is characterized by rapid growth, early metastasis, high malignant, and mortality. Accumulating evidence demonstrated that promoter methylation of tumor-suppressor genes is implicated in the pathogenesis of melanoma. In the current study, we performed a meta-analysis to identify promising methylation biomarkers in the diagnosis of melanoma. We carried out a systematic literature search using Pubmed, Embase, and ISI web knowledge database and found that gene promoter methylation of 50 genes was reported to be associated with the risk of melanoma. Meta-analysis revealed that hypermethylation of claudin 11 (CLDN11; odds ratio [OR], 16.82; 95% confidence interval [CI], 1.97-143.29; p = 0.010), O-6-methylguanine-DNA methyltransferase (MGMT; OR, 5.59; 95% CI, 2.51-12.47; p < 0.0001), cyclin-dependent kinase inhibitor 2A (p16; OR, 6.57; 95% CI, 2.19-19.75; p = 0.0008), retinoic acid receptor β (RAR-β2; OR, 24.31; 95% CI, 4.58-129.01; p = 0.0002), and Ras association domain family member (RASSF1A; OR, 9.35; 95% CI, 4.73-18.45; p < 0.00001) was significantly higher in melanoma patients compared with controls. CLDN11 (OR, 14.52; 95% CI, 1.84-114.55; p = 0.01), MGMT (OR, 8.08; 95% CI, 1.84-35.46; p = 0.006), p16 (OR, 9.44; 95% CI, 2.68-33.29; p = 0.0005), and RASSF1A (OR, 7.72; 95% CI, 1.05-56.50; p = 0.04) hypermethylation was significantly increased in primary melanoma compared with controls. Methylation frequency of CLDN11 (OR, 25.56; 95% CI, 2.32-281.66; p = 0.008), MGMT (OR, 4.64; 95% CI, 1.98-10.90; p = 0.0004), p16 (OR, 4.31; 95% CI, 1.33-13.96; p = 0.01), and RASSF1A (OR, 10.10; 95% CI, 2.87-35.54; p = 0.0003) was significantly higher in metastasis melanoma compared with controls. These findings indicated that CLDN11, MGMT, p16, RAR-β2, and RASSF1A hypermethylation is a risk factor and a potential biomarker for melanoma. CLDN11, MGMT, p16, and RASSF1A promoter methylation may take part in the development of melanoma and become useful biomarkers in the early diagnosis of the disease.

Curcumol Controls Choriocarcinoma Stem-Like Cells Self-Renewal via Repression of DNA Methyltransferase (DNMT)- and Histone Deacetylase (HDAC)-Mediated Epigenetic Regulation

BACKGROUND Cancer stem cells (CSCs), in choriocarcinoma and other carcinomas, possess the ability of self-renewal and multilineage differentiation potential. We previous isolated choriocarcinoma cancer stem-like cells (CSLCs), which hold the stemness characteristics of CSCs. Epigenetic modifications have emerged as drivers in tumorigenesis, but the mechanisms of CSCs are largely unknown, and new drug therapies are needed to break the persistence of CSCs. MATERIAL AND METHODS Quantitative real-time PCR (qRT-PCR) and Western blot analysis were performed to detect the expression of DNMTs, HDACs, and stemness-genes. DNMTs and HDACs silencing and overexpressing lentivirus were transfected into JEG-3 cells to investigate the epigenetic functions in CSLCs. In vivo expression of curcumol effects of CSLCs on DNMTs and HDACs were analyzed by immunohistochemistry. RESULTS Expression of DNMT1, DNMT3b, HDAC1, and HDAC3 were increased in choriocarcinoma CSLCs. Consistent with the inhibitory effect of 5-AzaC and TSA on CSLCs, DNMT/HDAC knockdown displayed significant repression of self-renewal in CSLCs. Curcumol inhibited the stemness ability of CSLCs in vitro and in vivo, and the inhibitory effect we observed was mediated in part through repressing activity of DNMTs and HDACs. Importantly, curcumol showed a better effect than DNMT and HDAC inhibitors combined in eliminating CSLCs. CONCLUSIONS These findings indicate that DNMT- and HDAC-mediated epigenetic regulation plays an important role in the biology of choriocarcinoma CSLCs, and curcumol has the potential to be a new drug to fight CSLCs, warranting further investigation of epigenetic-based therapies.