Delineating the effect of demethylating agent 5-aza-2'-deoxycytidine on human Caco-2 colonic carcinoma cells

The Effects of 5-Aza-2'-Deoxycytidine and Valproic Acid on Apoptosis Induction and Cell Growth Inhibition in Colon Cancer HT 29 Cell Line

Background:

Epigenetic changes, including DNA methylation and histone modification, alter gene expression without the nucleotide template alterations and are associated with all stages of tumor formation and progression. Previously, we investigated the effects of DNA demethylating agents and histone deacetylase inhibitors on hepatocellular carcinoma and colon cancers. The current study aimed to investigate the effects of 5-aza-2'-deoxycytidine (5-AZA-CdR, decitabine) and valproic acid (VPA), individually as well as combined on apoptosis induction and cell growth inhibition in colon cancer HT 29 cell line.

Methods:

The effect of the compounds on the cell viability was measured by MTT assay. To determine cell apoptosis, the cells were treated with 5-aza-CdR and VPA. Propidium iodide was used for staining and the cells were analyzed using flow cytometry.

Results:

Both agents decreased cell viability in a time and dose-dependent manner significantly (P < 0.002). The results of flow cytometry demonstrated that 5-aza-CdR and VPA induced apoptosis significantly as opposed to control groups. Maximal percentage of apoptotic cells was obtained after 48 h with combined treatment.

Conclusions:

Our findings suggest that 5-aza-CdR and VPA can significantly inhibit cell growth and induce apoptosis in colon cancer HT 29 cell line.

Effect of 5-Aza-2'-Deoxycytidine in Comparison to Valproic Acid and Trichostatin A on Histone Deacetylase 1, DNA Methyltransferase 1, and CIP/KIP Family (p21, p27, and p57) Genes Expression, Cell Growth Inhibition, and Apoptosis Induction in Colon Cancer SW480 Cell Line

BACKGROUND

Cancer initiation and progression depends on genetic and epigenetic alterations such as DNA methylation and histone modifications. Hypermethylation and deacetylation of the CIP/KIP family (p21, p27, and p57) lead to tumorigenesis. Our previous study indicated that DNA methyltransferase (DNMT) inhibitor and histone deacetylase (HDAC) inhibitors can inhibit cell growth and induce apoptosis. The aim of the present study was to investigate the effect of 5-Aza-2'-deoxycytidine (5-Aza-CdR) in comparison to valproic acid (VPA) and trichostatin A (TSA) on HDAC1, DNMT1, and CIP/KIP family (p21, p27, and p57) genes expression, cell growth inhibition, and apoptosis induction in colon cancer SW480 cell line.

MATERIALS AND METHODS

The effect of the compounds on the cell viability was measured by MTT assay. The expression of HDAC1, DNMT1, and CIP/KIP family (p21, p27, and p57) genes was evaluated by real-time quantitative reverse transcription-polymerase chain reaction (RT-PCR). For the detection of cell apoptosis, apoptotic cells were examined by the Annexin V-FITC/PI detection kit.

RESULTS

The results of MTT assay indicated that 5-Aza-CdR, VPA, and TSA significantly inhibited cell growth (P < 0.002, P < 0.001, and P < 0.001, respectively). The results of real-time RT-PCR demonstrated that all compounds significantly down-regulated DNMT1 and HDAC1, and up-regulated p21, p27, and p57 genes expression. The result of flow cytometry assay revealed that all agents induced apoptosis significantly.

CONCLUSION

5-Aza-CdR, VPA, and TSA can significantly downregulate DNMT1 and HDAC1 and up-regulate p21, p27, and p57 genes expression through which enhance cell apoptosis and cell growth inhibition in colon cancer.

MicroRNA-193b acts as a tumor suppressor in colon cancer progression via targeting RAB22A

To explore microRNA (miR)-193b expression and its potential role in colon cancer, reverse transcription-quantitative polymerase chain reaction was performed to detect the miR-193b expression levels in 62 colon cancer tissues and normal adjacent tissues. The miR-193b-overexpressed cell line SW620 was used to study the role of miR-193b in colon cancer. Subsequently, a Transwell assay and cell cycle assay were performed to observe the functional cell changes in the in vitro expression levels of miR-193b. Results indicated that miR-193b expression levels were significantly decreased in colon cancer tissues compared with adjacent normal tissue (P<0.001) and the expression of miR-193b was significantly correlated with TNM staging (P=0.03) and lymph node invasion (P=0.007). Furthermore, overexpression of miR-193b significantly decreased colon cancer cell cycle progression and its migration ability. In addition, the present findings suggested that the increased expression of miR-193b by RAB22A, inhibited downstream proteins involved in the Ras signaling pathway, including the Ras and extracellular signal-related kinase which may inhibit cancer proliferation and migration. In conclusion, the aim was to clarify the association of miR-193b expression with colon cancer, and to explore the mechanism of miR-193b in colon cancer proliferation and cell migration. The preliminary findings revealed that miR-193b may have an important role in the process in colon cancer cell cycle and migration by the RAB22A-Ras signaling pathway, thus providing a theoretical basis for miR-193b as a potential molecular target for colon cancer treatment.

DNA methylation-regulated and tumor-suppressive roles of miR-487b in colorectal cancer via targeting MYC, SUZ12, and KRAS

Human colorectal cancer (CRC), characterized by its high morbidity and lethality, seriously threatens human health and lives. MicroRNA‐487b (miR‐487b) is currently reported to be aberrantly expressed in several tumors, but the detailed functions and underlying mechanisms of miR‐487b in CRC remain unclear. Here, we found that miR‐487b is downregulated in CRC cell lines and is markedly decreased in tumor specimens derived from CRC patients. MiR‐487b inhibits cell proliferation, migration and invasion and promotes the apoptosis of CRC cells in vitro. Statistical analysis of clinical samples indicates that miR‐487b may serve as a biomarker for early CRC diagnosis. Inverse correlations between the expression levels of MYC, SUZ12, and KRAS and that of miR‐487b exist in vitro and in CRC patient tissue specimens. Further experiments demonstrated the regulatory effects of miR‐487b on MYC, SUZ12, and KRAS, and the disruption of these genes partially restores the miR‐487b inhibitor‐induced phenotype. Additionally, miR‐487b promoter region is in a DNA hypermethylated condition and the DNA methyltransferase inhibitor 5‐aza‐2’‐deoxycytidine (5‐Aza) increases the levels of miR‐487b but suppresses the expression of MYC, SUZ12, and KRAS in a time‐ and concentration‐dependent manner in CRC cells. Collectively, miR‐487b is regulated by DNA methylation and it functions as a tumor suppressor in CRC mainly through targeting MYC, SUZ12, and KRAS. Our study provides insight into the regulatory network in CRC cells, offering a new target for treating CRC patients.