Weakened spindle checkpoint with reduced BubR1 expression in paclitaxel-resistant ovarian carcinoma cell line SKOV3-TR30.

OBJECTIVE: Paclitaxel sensitivity has recently been associated with the spindle checkpoint. The aim of our study is to investigate the status of spindle checkpoint and the alteration of its major components in phenotype with acquired paclitaxel resistance in ovarian carcinoma.

METHODS: A paclitaxel-resistant ovarian carcinoma cell line, SKOV3-TR30, with the resistant ability of 27-fold greater than its parental cell line, was derived from SKOV3 cell line. The competence of spindle checkpoint and the expression of the major spindle checkpoint proteins (BubR1 and Mad2) in SKOV3-TR30 cells were investigated.

RESULTS: Mitotic index and flow cytometric analysis revealed that SKOV3-TR30 cells were not arrested in M phase in contrast to SKOV3, which showed a clear mitotic arrest in the presence of paclitaxel or nocodazole. The expressions of securin and cyclin B in SKOV3-TR30 cells were significantly lower than those in SKOV3 cells, indicating the premature degradation of APC substrates in SKOV3-TR30 cells in response to spindle damagers. Chromosome spread analysis showed increased rate of premature sister chromatid segregation in SKOV3-TR30 cells. The expression of spindle checkpoint protein BubR1 was evidently lower in SKOV3-TR30 cells than that in SKOV3 cells. However, there was no significant difference in Mad2 expression between SKOV3-TR30 and SKOV3 cells.

CONCLUSIONS: This study demonstrates that weakened spindle checkpoint with reduced expression of BubR1, but not Mad2, is associated with acquired paclitaxel resistance in ovarian carcinoma cells.