Differential effects of doxorubicin treatment on cell cycle arrest and Skp2 expression in breast cancer cells

Abstract

Overexpression of Skp2, the ubiquitin ligase subunit that targets p27 for degradation, is often observed in cancers, and is associated with aggressive tumor proliferation and poor prognosis. As there is no drug at present that specifically targets Skp2, studies were undertaken to examine the effects of commonly used drugs on Skp2 regulation. Doxorubicin is among the most effective antitumor agents used for the management of breast cancer, but its effect on Skp2 expression is unknown. The objective of this study was to examine the effect of doxorubicin on Skp2 expression regulation in breast cancer cell lines. The expression of Skp2 mRNA and the protein levels of Skp2, p27, p21 and cyclin B were examined in doxorubicin-treated MCF-7 and MDA-MB-231 breast cancer cells. The effect of doxorubicin on the cell cycle profile was assessed by fluorescence-activated cell sorting analysis. Doxorubicin decreased Skp2 mRNA and protein levels in MCF-7 cells, but had the opposite effect in MDA-MB-231 cells. p27 levels were slightly decreased, whereas p53 and p21 levels were significantly upregulated in doxorubicin-treated MCF-7 cells. In contrast, p27 levels were unaffected by doxorubicin treatment in MDA-MB-231 cells, but cyclin B levels were markedly increased. Doxorubicin arrested MCF-7 cells at G1/S and G2/M checkpoints, whereas MDA-MB-231 cells were arrested at G2/M only. The differential effects of doxorubicin on Skp2 expression in breast cancer cells depend upon the specific cell cycle checkpoints activated by the drug. These changes induced by doxorubicin, however, do not significantly affect p27 expression in these cell lines, suggesting that the potential of a given drug to alter p27 expression through Skp2 modulation might depend on its specific action on cell cycle arrest.

Anticancer mechanisms of doxorubicin and zoledronic acid in breast cancer tumor growth in bone

“…Doxorubicin inhibits cellular proliferation via p53-dependent and p53-independent mechanisms (43)(44)(45). In p53 wild-type MCF7 breast cancer cells, doxorubicin treatment causes an accumulation of p53 (45)(46)(47)(48), p53 recruits p21 (46) leading to decreased expression of cyclin B and cdc2 resulting in a cell cycle block at G 2 -M (47, 48). However, MDA-MB-436 cells express mutated p53 and it is unlikely that increases in p53 expression seen in these tumors are capable of recruiting p21 (49).…”

Synergistic antitumor effect of TRAIL and adriamycin on the human breast cancer cell line MCF-7

“…Worldwide, breast cancer is the most common form of malignancy in women, with high incidence and mortality rates (1). Adriamycin (ADM) is among the most effective antitumor drugs used for the management of breast cancer.…”

In vivostudy of effects of artesunate nanoliposomes on human hepatocellular carcinoma xenografts in nude mice

“…The antihepatoma effect of artesunate API and artesunate nanoliposomes was concentration-dependent within a certain concentration range (Bar-On et al, 2007;Lu et al, 2011;Chernysh et al, 2012). Experimental screening concentrations were 6.25-200 mg ml.…”

“…The in vitro hepatoma HepG-2 cells in the log phase were harvested, single-cell suspensions were prepared at a concentration of 1 Â 10 7 viable cells/ml, and the mice were injected subcutaneously in the left flank with 0.2 ml of the cell suspension (Bar-On et al, 2007;Shen et al, 2010;Chernysh et al, 2012). The mice were observed everyday.…”