Breast cancer cells are arrested at different phases of the cell cycle following the re-expression of ARHI

Abstract

Abstract. ARHI is a maternally imprinted tumor suppressor gene that is expressed in normal breast epithelial cells but not in most breast cancer cells. Aberrant methylation and hypernomic histone deacetylation have been implicated in the silencing of ARHI. To investigate the mechanism of ARHI induction, MDA-MB-231 breast cancer cells were either transfected with the eukaryotic expression vector, pcDNA3.1(+)-ARHI, or were simultaneously treated with a histone deacetylase inhibitor, [trichostatin A, (TSA)] and the methyltransferase inhibitor, 5-aza-2'-deoxycytidine (DAC). The latter treatment group also included the targeting of ARHI by small interfering RNA (siRNA) to further examine interactions between ARHI and the drugs applied. Levels of ARHI were detected by western blotting, MTT assays were used to evaluate cell proliferation, and both cell cycle progression and apoptosis were detected using flow cytometry. Both the transfection of pcDNA3.1(+)-ARHI and the application of TSA+DAC induced the expression of ARHI. Furthermore, reduced cell proliferation, cell cycle arrest and enhanced apoptosis were observed for both groups compared to controls. However, a G1/S cell cycle arrest was observed for the pcDNA3.1(+)-ARHI group, while a G2 cell cycle arrest was observed for the TSA+DAC group. The latter effect was reversed with the introduction of ARHI-targeted siRNA in combination with TSA+DAC treatment. To further clarify these observations, expression levels of several key cell cycle regulators were analyzed by western blotting. The pcDNA3.1(+)-ARHI group exhibited higher expression levels of p53, p21 and p27, and lower levels of cyclin D1, CDK4 and CDK6 when compared to the control group (P<0.05). For the TSA+DAC group, higher levels of p53, p21, cyclin B1 and Chk1 were detected, concomitant with lower levels of CDK1, when compared to the control group. Taken together, these results suggest that ARHI acts as a tumor suppressor gene in MDA-MB-231 cells and, although TSA+DAC can block the cells at different cell cycle phage, the antitumor effect is ARHI-dependent.

Aplasia Ras homologue member I overexpression inhibits tumor growth and induces apoptosis through inhibition of PI3K/Akt survival pathways in human osteosarcoma MG-63 cells in culture

“…Evidence suggests that the therapeutic options for OS have not improved over the past four decades (7,8); thus, novel approaches to OS are required. Efforts to identify new genes and signaling pathways that affect tumor progress have suggested that the aplasia Ras homologue member Ⅰ (ARHI) gene (also known as DIRAS3) has a crucial role in numerous types of cancer, such as breast cancer (9,10), ovarian cancer (11,12), hepatocellular carcinoma (13), lung cancer (14) and glioma (15). Additionally, it has been reported that the ARHI protein is downregulated in multiple myeloma endothelial cells and is involved in proliferation and signal transduction in these cells (16).…”

Oncogenic PAX6 elicits CDK4/6 inhibitor resistance by epigenetically inactivating the LATS2‐Hippo signaling pathway

“…The DNA methylation level is a marker of the CDK4/6 inhibitor response 50 . Treatment with a histone deacetylase inhibitor and a methyltransferase inhibitor resulted in increased levels of p21 and p53 and lower levels of CDK1, 73 suggesting that methyltransferase inhibitors can affect CDK activity. Furthermore, a recent study indicated that metformin, a widely used anti‐diabetic drug, can mediate tumor suppression in an epigenetic pathway, 74 and it has been reported that metformin can overcome CDK4/6 inhibitor resistance, and the addition of a methyltransferase inhibitor to CDK4/6i is likely to benefit patients with carcinomas 75 .…”

OPA1 supports mitochondrial dynamics and immune evasion to CD8+ T cell in lung adenocarcinoma

“…150 µl RNase A and PI staining solution were then added to each tube and were then incubated at 4 °C. 20 min later, the results were analyzed by using flow cytometry and the ratio of cell among the G1, S and G2/M phases were analyzed ( Zuo et al, 2014 ).…”