Enhanced apoptotic effects of novel paclitaxel analogs on NCI/ADR-RES breast cancer cells
Li-Xi Yang1, Jun Zhu, Hui-Juan Wang
1Radiobiology Laboratory, California Pacific Medical Center Research Institute, St. Mary's Medical Center, San Francisco, CA 94118, USA. Yang@cooper.cpmc.org
Abstract:
This study aimed to investigate the apoptotic effects of novel paclitaxel analogs on NCI/ADR-RES breast cancer cells. Using the colony formation assay, the cytotoxicity of three novel paclitaxel analogs were evaluated on NCI/ADR-RES cells which overexpress multidrug-resistant gene (MDR1). All three novel paclitaxel analogs exhibited significantly higher cytotoxicity on NCI/ADR-RES cells than paclitaxel. One analog, TL139, was 140 times more effective than paclitaxel. Using TUNEL and DNA fragmentation assay, remarkably increased apoptosis in the paclitaxel analog-treated cells was observed at 48-72 hours, but not in paclitaxel-treated cells. Caspases-3/7 were dramatically activated at 48-72 hours by the novel paclitaxel analogs. The enhanced activity of caspases-3/7 was evidently verified by the measurement of the cleavage of poly(ADP-ribose) polymerase (PARP). The increased activity of caspases-3/7 significantly correlated with the enhanced apoptosis and cell survival data. Treatment with paclitaxel analogs resulted in a significant amount of mitotic arrest. Using Western blot, the phosphorylation of Bcl-2 protein was found in palictaxel analog-treated cells in a time-dependent manner similar to that of mitotic arrest, thereby indicating that there existed a close correlation between Bcl-2 phosphorylation and mitotic arrest that preceded apoptosis. We conclude that novel taxane analogs could effectively kill MDR1-positive breast cancer cells via the mode of apoptosis.
Insights
Novel paclitaxel analogs show potent anti-cancer effects against multidrug-resistant breast cancer cells. These analogs induce apoptosis and mitotic arrest, offering a promising therapeutic strategy for resistant tumors.
Area of Science:
- Pharmacology
- Oncology
- Molecular Biology
Background:
- Multidrug resistance (MDR1) in breast cancer limits the efficacy of standard chemotherapy.
- Paclitaxel is a key chemotherapeutic agent, but resistance can develop.
- Novel drug development is crucial to overcome treatment resistance in breast cancer.
Purpose of the Study:
- To evaluate the efficacy of novel paclitaxel analogs against NCI/ADR-RES breast cancer cells.
- To investigate the mechanism of action, including apoptosis induction and cell cycle effects.
- To compare the potency of novel analogs with conventional paclitaxel.
Main Methods:
- Cytotoxicity assessed using colony formation assays.
- Apoptosis evaluated via TUNEL and DNA fragmentation assays.
- Caspase activity (caspase-3/7) and PARP cleavage measured.
- Mitotic arrest and Bcl-2 phosphorylation analyzed by Western blot.
Main Results:
- Three novel paclitaxel analogs demonstrated significantly higher cytotoxicity than paclitaxel against MDR1-overexpressing cells.
- One analog, TL139, was 140 times more potent than paclitaxel.
- Paclitaxel analogs induced significant apoptosis and caspase-3/7 activation, unlike paclitaxel.
- Treatment led to mitotic arrest and time-dependent Bcl-2 phosphorylation, preceding apoptosis.
Conclusions:
- Novel taxane analogs are effective against MDR1-positive breast cancer cells.
- The mechanism involves the induction of apoptosis through caspase activation and mitotic arrest.
- These findings suggest potential for new therapeutic agents in overcoming paclitaxel resistance.
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