A very low toxic agent induces apoptosis and reduces growth of human hepatocellular carcinoma cells

2-Methoxyestradiol blocks cell-cycle progression at the G2/M phase and induces apoptosis in human acute T lymphoblastic leukemia CEM cells

2-Methoxyestradiol (2-ME2) is an endogenous metabolite of 17beta-estradiol (E2) with estrogen receptor-independent anti-cancer activity. The current study sought to determine the mechanism of anti-cancer activity of 2-ME2 in human acute T lymphoblastic leukemia CEM cells. Results showed that 2-ME2 markedly suppressed proliferation of CEM cells in a time- and dose-dependent manner. 2-ME2-treated CEM cells underwent typical apoptotic changes. Exposure to 2-ME2 led to G(2)/M phase cell-cycle arrest, which preceded apoptosis characterized by the appearance of a sub-G(1) cell population. In addition, cytosolic cytochrome c release, increased procaspase-9 and -3 expressions, poly(ADP-ribose) polymerase (PARP) cleavage, and induced expression of caspase-8 were detected, suggesting that both the intrinsic apoptotic pathway and extrinsic apoptotic pathway were involved in 2-ME2-induced apoptosis. Moreover, the expression level of p21 protein was upregulated, whereas Bcl-2 and dysfunctional p53 protein were downregulated, which also contributed to 2-ME2-induced apoptosis. Our findings revealed that 2-ME2 might be a potent natural candidate for chemotherapeutic treatment of human acute T lymphoblastic leukemia when the precise effects of 2-ME2 were investigated further in other T leukemia cell lines and in primary T-cell leukemias.

2-methoxyestradiol-induced cell death in osteosarcoma cells is preceded by cell cycle arrest

2-Methoxyestradiol (2-ME), a naturally occurring mammalian metabolite of 17beta-Estradiol (E2), induces cell death in osteosarcoma cells. To further understand the molecular mechanisms of action, we have investigated cell cycle progression in 2-ME-treated human osteosarcoma (MG63, SaOS-2 and LM7 [corrected]) cells. At 5 microM, 2-ME induced growth arrest by inducing a block in cell cycle; 2-ME-treatment resulted in 2-fold increases in G1 phase cells and a decrease in S phase cells in MG63 and SaOS-2 osteosarcoma cell lines, compared to the appropriate vehicle controls. 2-ME-treatment induced a threefold increase in the G2 phase in LM7 [corrected] osteosarcoma cells. The results demonstrated steroid specificity, as the tumorigenic metabolite, 16alpha-hydroxyestradiol (16-OHE), did not have any effect on cell cycle progression in osteosarcoma cells. The cell cycle arrest coincided with an increase in expression of the cell cycle markers p21, p27 and p53 proteins in 2-ME-treated osteosarcoma cells. Also, MG63 cells, transiently transfected with cDNA for a 'loss of function mutant' RNA-dependent protein kinase (PKR) protein, were resistant to 2-ME-induced cell cycle arrest. These results suggest that 2-ME works in concert with factors regulating cell cycle progression, and cell cycle arrest precedes cell death in 2-ME-treated osteosarcoma cells.

Antineoplastic activity of 2-methoxyestradiol in human pancreatic and gastric cancer cells with different multidrug-resistant phenotypes

BACKGROUND AND AIM

Chemoresistance often leads to loss of the last treatment option for cancer. 2-Methoxyestradiol (2-ME2) has been shown to inhibit tumor growth. The aim was to examine the efficacy of 2-ME2 on multidrug-resistant human cells from pancreatic and gastric cancer.

METHODS

We investigated the impact of 2-ME2 on multidrug-resistant cells derived from human pancreatic and gastric cancer cells that were positive or negative for the MDR1-gene.

RESULTS

In pancreatic cancer cells, growth inhibition was 57% in parental, 72% in MDR1-negative and 87% in MDR1-positive cells after 1 micromol/L 2-ME2. In gastric cancer cells we found a growth inhibition of 75% in parental, 82% in MDR1-positive and 95% in MDR1-negative cells. Strong induction of apoptosis was induced after a low dose of 2-ME2. No significant difference in the amount of apoptotic cells was observed between parental and multidrug-resistant cells of both tumor types. The number of apoptotic cells after 2-ME2 ranged from 7.5% in parental gastric cancer cells to 20.1% in MDR1-negative gastric cancer cells.

CONCLUSION

2-ME2 may therefore have clinical application for chemoresistant cancer.

Influence of 2-methoxyestradiol on cell morphology and Cdc2 Kinase activity in WHCO3 esophageal carcinoma cells

The influence of 1 x 10(-6) M exogenous 2-methoxyestradiol (2ME) was investigated on nuclear and cytoplasmic morphology, as well as Cdc (cell division cycle) 2 kinase activity in WHCO3 esophageal carcinoma cells. Mitotic indices after 18 h of 2ME exposure revealed an increase in metaphase cells (9.0%) when compared to the vehicle-treated cells (0.9%). 2ME-treated cells showed apoptotic cells at 5.6% after 18 h of exposure to dimethyl sulphoxide, compared to 0.9% in vehicle-treated cells. Increased morphological characteristics of apoptosis were observed in 2ME-treated cells after 21.5 h of exposure. Twelve percent of cells were in apoptosis when compared to the 1.6% of vehicle-treated cells. Furthermore, 42.4% of cells were arrested in metaphase after 21.5 h of 2ME exposure compared to 2.9% of vehicle-control cells present in metaphase. Cdc2 kinase activity was statistically significantly increased (1.7-fold) (P < 0.005) after 18 h of 2ME exposure when compared to vehicle-treated controls. Although the mechanism of 2ME's action on esophageal carcinoma cells is not yet elucidated, the present study revealed that 2ME caused metaphase arrest, as well as an increase in Cdc2 kinase activity that culminated in the induction of apoptosis in these cells.