Influence of prostaglandin A2 on Bax, Bcl-2 and PCNA expression in MCF-7 cells

Abstract

The effects of 20 μg/mL exogenous prostaglandin A 2 (PGA 2 ) were determined on Bax, Bcl-2 and proliferating cell nuclear antigen (PCNA) expression levels in MCF-7 cells. Flow cytometric analysis indicated a pronounced increase in the S phase and a decrease in the G 1 phase, whereas a significant increase in the DNA content preceding the G 0 /G 1 peak was also observed after 48 h of exposure to PGA 2 . Confirmation of apoptosis was determined after 12 h, 36 h and 48 h of PGA 2 exposure employing the mitosensor reagent that detects potential changes in the mitochondrial membrane. Twenty-eight percent of PGA 2 -exposed cells were in apoptosis when compared to the 7.1% vehicle-treated cells after 48 h. PGA 2 exposure led to statistically significant increase (1.25-fold) over vehicle-treated controls in Bax expression levels. Decreases in Bcl-2 (0.79-fold), as well as PCNA (0.69-fold) expression levels over vehicle-treated controls were observed. The Bax/Bcl-2 ratio for PGA 2 -exposed cells was 2.7. The present study suggests that an accumulation in the S phase, a decrease in expression levels of PCNA, as well as an altered ratio in favor of Bax, could lead to the induction of apoptosis in these cells.Research has shown that prostaglandin A 2 (PGA 2 ), a cyclopentenone and endogenous metabolite derived from arachidonic acid, exhibits potent anti-proliferative activity in vivo (5,14,20,22) and in vitro (1, 17-19, 21, 23). Concentration-dependent studies from previous research (12) revealed that 20 μg/mL results in optimal growth inhibition in vitro. This was confirmed in our laboratory where IC 50 = 20 μg/ mL was determined (results not shown). PGA 2 inhibited proliferation of tumor cells depending on dose, duration of exposure and cell type (12). In addition, we have demonstrated that the breast adenocarcinoma cells, MCF-7, were more susceptible to the anti-mitogenic effects of PGA 2 when compared to human epithelial cervix carcinoma (HeLa) cells (11). Furthermore, degree of differentiation of oesophageal carcinoma cells was also shown to influence tumor cell susceptibility to the anti-mitogenic effects of PGA 2 . More differentiated and normal cells appeared to be less affected, while more pronounced effects were observed in less differentiated cell lines (12).Since PGA 2 targets active proliferating cells and plays an active role in the induction of apoptosis, especially in cells that present with carcinogenic properties (12,25), the aim of this study was to confirm the anti-mitogenic effects of PGA 2 and to investigate the influence of PGA 2 on Bax, Bcl-2 and PCNA expression in MCF-7 cells in order to suggest a possible mechanism for induction of apoptosis.

Perichondrium mesenchymal stem cells inhibit the growth of breast cancer cells via the DKK-1/Wnt/β-catenin signaling pathway

“…The Wnt/β-catenin pathway is related to the efficacy of MSCs in suppressing hepatoma and breast cancer (18,28,35). The Bcl-2, c-Myc, PCNA and survivin genes are all targets of the Wnt/β-catenin signaling pathway (36,37). In the present study, western blot analyses confirmed that the Wnt/β-catenin signaling pathway in SHZ-88 cells was blocked by PMSC-conditioned medium.…”

Suppression of tumorigenesis by human mesenchymal stem cells in a hepatoma model

“…Wnt signaling regulates genes that are involved in cell metabolism, proliferation, cell-cycle regulation and apoptosis [30,31]. The PCNA, c-Myc, survivin and Bcl-2 genes are all targets of Wnt signaling [32,33].…”

Effect of human mesenchymal stem cells on hepatoma cell line

“…27,28 The PCNA, survivin and β-Catenin genes are all targets of Wnt signaling. 29,30 Zhu et al 31 demonstrated that MSCs have an inhibitory effect on tumor proliferation by identifying that DKK-1 (dickkopf-1) which was secreted by MSCs, acts as a negative regulator of Wnt signaling pathway and is one of the molecules responsible for the inhibitory effect of MSCs on tumor. MSCs also up regulate the mRNA expression of cell-cycle negative regulator p21 and apoptosis-associated protease caspase-3, resulting in a G0/G1 phase arrest and apoptotic cell death of tumor cells.…”