Foxo3a-Mediated DNMT3B Impedes Cervical Cancer Cell Proliferation and Migration Capacities through Suppressing PTEN Promoter Methylation

Effect of 5-Aza-2'-deoxycytidine on T-cell acute lymphoblastic leukemia cell biological behaviors and PTEN expression

Objective

We currently face a sharp increase of T-cell acute lymphoblastic leukemia (T-ALL) incidence and a challenge of unmasking its complex etiology. The deoxycytidine analog 5-Aza-2'-deoxycytidine (5-Aza-dC) is currently the most common nucleoside methyltransferase inhibitor. The objective of this study was to clarify the role of 5-Aza-dC in T-ALL cell biological behaviors and phosphatase and tensin homolog deleted on chromosome ten (PTEN) expression.

Material and Methods

T-ALL cell lines were divided into the experimental group with 5-Aza-dC solution treatment, and the control group without treatment. PTEN methylation was detected using methylation-specific polymerase chain reaction (MS-PCR). Following the measurement of cell proliferation, viability, apoptosis, invasion, migration, etc., quantitative reverse transcription-polymerase chain reaction (PCR) was conducted to detect PTEN, DNA methyl-transferases (DNMT1), DNMT3a, MBD2, and MeCP2 expressions; Western blot to detect PTEN, PI3K, AKT, and mTOR protein expressions. In addition, rescue experiments to inhibit and restore the expression of PTEN in different groups were performed for further identification of the results in the former parts.

Results

MS-PCR results showed that in Jurkat cells, the target band was amplified using methylated primers for the PTEN gene promoter region; moreover, at 10 μmol/L of 5-Aza-dC for 24 h, PTEN methylation was completely removed without any un-methylated band observed. The experimental group had significantly lower cell proliferation and viability rates, higher apoptosis rates, decreased cell proportion in S phase, reduced invasion and migration; increased PTEN expression, decreased DNMT1, DNMT3a, MBD2, and MeCP2 mRNA expressions; and decreased PI3K, AKT, and mTOR protein expressions than those in the control group (all P < 0.05). Furthermore, according to the rescue experiment, silenced PTEN expression weakened the beneficial roles of 5-Aza-dC treatment, and resulted in significantly higher cell proliferation and viability rates, lower apoptosis rates, increased cell proportion in S phase, increased cell invasion and migration; decreased PTEN expression, elevated DNMT1, DNMT3a, MBD2, and MeCP2 mRNA expressions, and higher PI3K, AKT, and mTOR protein expressions (all P < 0.05). While restored PTEN expression enhanced functions of 5-Aza-dC treatment, leading to obviously lower cell proliferation and viability rates, higher apoptosis rates, increased cell proportion in G1 phase, and reduced cell invasion and migration; as well as increased PTEN expression, decreased DNMT1, DNMT3a, MBD2, and MeCP2 mRNA expressions, and lower PI3K, AKT, and mTOR protein expressions (all P < 0.05).

Conclusion

Demethylation treatment with 5-Aza-dC can inhibit T-ALL cell malignant biological behaviors and enhance the sensitivity to chemotherapy agents possibly, which may be related to the inhibited expressions of DNMT1, DNMT3a, MBD2, and MeCP2, and restored expression activity of PTEN to negatively regulate the PI3K/AKT signal transduction. Our silencing and restoration of PTEN expressions further support our findings, highlighting that demethylation with 5-Aza-dC to restore the anti-tumor activity of the tumor suppressor gene PTEN may be a promising therapeutic option for treating T-ALL.

Methyltransferase DNMT3B promotes colorectal cancer cell proliferation by inhibiting PLCG2

Aberrant DNA methylation patterns in the promoter region of PLCG2 are associated with dysregulated signaling pathways and cellular functions. Its role in colorectal cancer cells is still unknown. In this study, qRT-PCR is used to measure DNMT3B expression in colorectal cancer. Western blot analysis and immunohistochemistry are used to analyze DNMT3B and PLCG2 protein levels in colorectal tissues and cell lines. Cell Counting Kit-8 (CCK-8) and colony formation assays are used to assess the proliferation of colorectal cancer cells. Methylation-specific PCR (MSP) and bisulfite-sequencing PCR (BSP) are used to measure DNA methylation level. Our results show that DNMT3B is overexpressed in colorectal cells in the TCGA datasets according to Kaplan-Meier plots. DNMT3B is significantly overexpressed in tumor tissues compared to that in adjacent nontumor tissues. Western blot analysis results demonstrate high expression of DNMT3B in tumor tissues. Compared to normal colonic epithelial cells, colorectal cancer cell lines exhibit elevated level of PLCG2 methylation. Overexpression of PLCG2 effectively prevents the growth of colorectal cancer xenograft tumors in vivo. PLCG2 is identified as a key downstream regulatory protein of DNMT3B in colorectal cancer. DNMT3B inhibits PLCG2 transcription through methylation of the PLCG2 promoter region. DNMT3B controls colorectal cancer cell proliferation through PLCG2, which is useful for developing therapeutic approaches that target PLCG2 expression for the treatment of colorectal cancer.

Virtual screening of FOXO3a activators from natural product-like compound library

FOXO3a is an inevitable transcription factor, which is involved in the regulation of biological processes such as proliferation, DNA damage repair, cell cycle arrest and cell death. Previous studies confirmed that FOXO3a is an excellent tumor suppressor and in cancer cells, it gets phosphorylated followed by proteasomal degradation. FOXO3a is found to be inactivated in cancer cells, whereas in normal cells it gets activated and upregulates its downstream targets, which induces apoptotic pathways. Hence, activation of FOXO3a can be implicated in cancer prevention and treatment. A variety of commercially available FOXO3a activators such as doxorubicin and metformin possess undesirable adverse effects to normal cells and tissues, which are their major limitations. Natural bioactive compounds, eliminating the limitations of such compounds, become an excellent choice for the treatment and prevention of cancer. In this study, a library of natural product-like compounds was screened for their FOXO3a activation potential through in silico approach, which included the use of several bioinformatics tools and processes. Other molecular interaction studies as well as binding and specificity studies were carried out with the help of molecular dynamics simulation. Virtual screening of 7700 small molecules from the Natural Products-like Compound Library revealed the top three FOXO3a activators F3385-6269, F2183-0033 and F3351-0330. Further validation studies are warranted to confirm these findings.

LncRNA ABHD11-AS1 activates EGFR signaling to promote cervical cancer progression by preventing FUS-mediated degradation of ABHD11 mRNA

Cervical cancer is one of the most common gynecological cancers with high metastasis, poor prognosis and conventional chemotherapy. The long non-coding RNA (lncRNA) ABHD11 antisense RNA 1 (ABHD11-AS1) plays a vital role in tumorigenesis and is involved in cell proliferation, differentiation, and apoptosis. Especially for cervical cancer, the functions and mechanisms of ABHD11-AS1 are still undetermined. In this study, we explored the role and underlying mechanism of ABHD11-AS1 in cervical cancer. We found that ABHD11-AS1 is highly expressed in cervical cancer tissue. The roles of ABHD11-AS1 and EGFR have investigated the loss of function analysis and cell movability in SiHa and Hela cells. Knockdown of ABHD11-AS1 and EGFR significantly inhibited the proliferation, migration, and invasion and promoted apoptosis of SiHa and Hela cells by up-regulating p21 and Bax and down-regulating cyclin D1, Bcl2, MMP9, and Vimentin. ABHD11-AS1 knockdown could decrease the expression of EGFR. In addition, ABHD11-AS1 could regulate the EGFR signaling pathway, including p-EGFR, p-AKT, and p-ERK. Spearman's correlation analysis and cell experiments demonstrated that ABHD11 was highly expressed in tumor tissue and partially offset the effect of shABHD11-AS1 on the proliferation, migration, and invasion of SiHa and Hela cells. Then, RNA pulldown was used to ascertain the mechanisms of ABHD11-AS1 and FUS. ABHD11-AS1 inhibited ABHD11 mRNA degradation by bounding to FUS. A subcutaneous xenograft of SiHa cells was established to investigate the effect of ABHD11-AS1 in tumor tissue. Knockdown of ABDH11-AS1 inhibited tumor growth and decreased the tumor volume. ABHD11-AS1 knockdown inhibited the expression of Ki67 and Vimentin and up-regulated the expression of Tunel. Our data indicated that ABHD11-AS1 promoted cervical cancer progression by activating EGFR signaling, preventing FUS-mediated degradation of ABHD11 mRNA. Our findings provide novel insights into the potential role of lncRNA in cervical cancer therapy.

Advances in epigenetic modifications and cervical cancer research

Cervical cancer (CC) is an important public health problem for women, and perspectives and information regarding its prevention and treatment are quickly evolving. Human papilloma virus (HPV) has been recognized as a major contributor to CC development; however, HPV infection is not the only cause of CC. Epigenetics refers to changes in gene expression levels caused by non-gene sequence changes. Growing evidence suggests that the disruption of gene expression patterns which were governed by epigenetic modifications can result in cancer, autoimmune diseases, and various other maladies. This article mainly reviews the current research status of epigenetic modifications in CC based on four aspects, respectively DNA methylation, histone modification, noncoding RNA regulation and chromatin regulation, and we also discuss their functions and molecular mechanisms in the occurrence and progression of CC. This review provides new ideas for early screening, risk assessment, molecular targeted therapy and prognostic prediction of CC.