BackgroundMiR-155 has emerged as an “oncomiR”, which is the most significantly up-regulated miRNA in breast cancer. However, the mechanisms of miR-155 functions as an oncomiR are mainly unknown. In this study, the aims were to investigate the effects of miR-155 on cell proliferation, cell cycle, and cell apoptosis of ERalpha (+) breast cancer cells and to verify whether TP53INP1 (tumor protein 53-induced nuclear protein 1) is a target of miR-155, and tried to explore the mechanisms of miR-155 in this process.ResultsThe expression of miR-155 is significantly higher in MCF-7 cells compared with MDA-MB-231 cells. Ectopic expression of TP53INP1 inhibits growth of MCF-7 cells by inducing cell apoptosis and inhibiting cell cycle progression. Overexpression of miR-155 increases cell proliferation and suppress cell apoptosis, whereas abrogating expression of miR-155 suppress cell proliferation and promotes cell apoptosis of MCF-7 cells. In addition, miR-155 negatively regulates TP53INP1 mRNA expression and the protein expression of TP53INP1, cleaved-caspase-3, -8, -9, and p21, and luciferase reporter reveals that TP53INP1 is targeted by miR-155.ConclusionsTP53INP1 is the direct target of miR-155. MiR-155, which is overexpressed in MCF-7 cells, contributes to proliferation of MCF-7 cells possibly through down-regulating target TP53INP1.

In estrogen responsive breast cancer cells, estradiol (E2) is a key regulator of cell proliferation and survival. MiR-155 has emerged as an "oncomiR", which is the most significantly up-regulated miRNA in breast cancer. Moreover, miR-155 is higher in ERα (+) breast tumors than ERα (-), but no one has examined whether E2 regulates miR-155 expression in MCF-7 cells. In this study, the aim was to explore whether miR-155 involved in E2 regulated expression of estrogen responsive genes. We evaluated miR-155 expression in human breast cancer cells by real-time PCR, finding out miR-155 was overexpressed in MCF-7 cells compared with MDA-MB-231 cells. Treatment with E2 in MCF-7 cells increased miR-155 expression, promoting proliferation and decreasing apoptosis, similarly, transfection of miR-155m to MCF-7 cells gave the similar results. In contrast, inhibited miR-155 expression by transfection with miR-155 inhibitors reduced proliferation and promoted apoptosis of MCF-7 cells. Moreover, TP53INP1 is one of the targets of miR-155. E2 negatively regulated TP53INP1 mRNA expression and the protein expression of TP53INP1, cleaved-caspase-3, -8, -9, and p21, whereas transfection with miR-155 inhibitors increased TP53INP1, cleaved-caspase-3, -8, -9, and p21 protein level. These results demonstrated that E2 promoted breast cancer development and progression possibly through increasing the expression of miR-155, which was overexpressed in MCF-7 cells, contributes to proliferation of MCF-7 cells possibly through down-regulating TP53INP1.

Cytochrome P4501B1 (CYP1B1) is responsible for tumor progression in estrogen receptor-positive breast cancer due to its key role in estrogen metabolism, which is upregulated by PGE2, the main product of COX-2 that is found to be overexpressed in many breast tumors. Previous studies reported that inhibition of the COX-2/PGE2 pathway, by 1,25-dihydroxyvitamin D3 in MCF-7 breast cancer cells. The aim of this study was to investigate if the CYP1B1 protein expression shows covariation with the COX-2 and phosphorylated ERα (p-ERα) in human breast cancer. We also investigated whether 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] downregulates CYP1B1 via the COX-2/PGE2 pathway in MCF-7 cells. We analyzed the expression of COX-2, p-ERα and CYP1B1 using an immunohistochemical staining assay. In the present study, COX-2 was correlated to p-ERα (P<0.001) and CYP1B1 (P=0.001), p-ERα was correlated to CYP1B1 (P=0.012). We assessed the effects of 1,25(OH)2D3 on MCF-7 cells. 1,25(OH)2D3 treatment inhibited MCF-7 cell growth in a time-and dose-dependent manner; the cell cycle was arrested in the G0/G1 phase. Treatment with 100 nmol/l 1,25(OH)2D3 for 72 h significantly decreased the expression of COX-2 mRNA in MCF-7 cells (P<0.05), decreased the levels of PGE2 in cell culture supernatant (P<0.01), and downregul-ated p-ERK, p-ERα and CYP1B1 protein expression (P<0.05). Taken together, these results suggest that the COX-2/PGE2 pathway positively regulates the expression of CYP1B1 in breast cancer. 1,25-Dihydroxyvitamin D3 inhibits the growth of MCF-7 cells and downregulates CYP1B1 mediated by the COX-2/PGE2 pathway.

These data indicate that HDAC inhibitor TSA effectively attenuates liver injury during sepsis and these effects seem to rely on reduced inflammatory mediator production. These findings suggest that novel anti-inflammatory drugs targeting HDAC might offer promising therapeutic intervention for controlling the dysregulated inflammation.

The acetyltransferase inhibitor garcinol, a polyisoprenylated benzophenone, is extracted from the rind of the fruit of Garcinia indica, a plant found extensively in tropical regions. Anti-cancer activity has been suggested but there is no report on its action via inhibiting acetylation against cell proliferation, cell cycle progression, and apoptosis-inhibtion induced by estradiol (E 2 ) in human breast cancer MCF-7 cells. The main purposes of this study were to investigate the effects of the acetyltransferase inhibitor garcinol on cell proliferation, cell cycle progression and apoptosis inhibition in human breast cancer MCF-7 cells treated with estrogen, and to explore the significance of changes in acetylation levels in this process. We used a variety of techniques such as CCK-8 analysis of cell proliferation, FCM analysis of cell cycling and apoptosis, immunofluorescence analysis of NF-κB/ p65 localization, and RT-PCR and Western blotting analysis of ac-H3, ac-H4, ac-p65, cyclin D1, Bcl-2 and Bclxl. We found that on treatment with garcinol in MCF-7 cells, E 2 -induced proliferation was inhibited, cell cycle progression was arrested at G0/G1 phase, and the cell apoptosis rate was increased. Expression of ac-H3, ac-H4 and NF-κB/ac-p65 proteins in E 2 -treated MCF-7 cells was increased, this being inhibited by garcinol but not ac-H4.The nuclear translocation of NF-κB/p65 in E 2 -treated MCF-7 cells was also inhibited, along with cyclin D1, Bcl-2 and Bcl-xl in mRNA and protein expression levels. These results suggest that the effect of E 2 on promoting proliferation and inhibiting apoptosis is linked to hyperacetylation levels of histones and nonhistone NF-κB/ p65 in MCF-7 cells. The acetyltransferase inhibitor garcinol plays an inhibitive role in MCF-7 cell proliferation promoted by E 2 . Mechanisms are probably associated with decreasing ac-p65 protein expression level in the NF-κB pathway, thus down-regulating the expression of cyclin D1, Bcl-2 and Bcl-xl.