Characterization of a human colorectal carcinoma cell line with acquired resistance to flavopiridol
V Smith1, F Raynaud, P Workman
1CRC Centre for Cancer Therapeutics, the Institute of Cancer Research, Sutton, Surrey, United Kingdom.
Abstract:
Flavopiridol is a broad-spectrum inhibitor of cyclin-dependent kinases (cdks) and represents the first in this anticancer class to enter clinical trials. In anticipation of the likelihood that, as with other cancer drugs, acquired resistance may limit the drug's efficacy, an acquired resistance model has been established by in vitro drug exposure of the human colon carcinoma cell line HCT116. This stably resistant line, possessing 8-fold resistance to flavopiridol, showed a lack of cross-resistance to the anticancer agents etoposide, doxorubicin, paclitaxel, topotecan, and cisplatin, and notably to other chemical classes of cdk inhibitors: the aminopurines roscovitine and purvalanol A, 9-nitropaullone, and hymenialdisine. Resistance did not seem to be related to differences in the levels of multidrug resistance drug efflux proteins, P-glycoprotein, and MRP1. Moreover, there were no changes in overall drug accumulation between the resistant and sensitive cell lines. Flavopiridol induced cell cycle arrest, apoptosis, and inhibition of retinoblastoma gene product phosphorylation on serine 780 in both parental and resistant lines, but the latter required 8-fold higher concentrations to achieve these effects. Cyclin E protein levels and cyclin E-associated kinase activity were increased in the resistant line, suggesting that overexpression of cyclin E may be the mechanism of resistance to flavopiridol. However, transfection of cyclin E to increase expression of this protein did not result in an increase in resistance to flavopiridol. Thus, up-regulation of cyclin E alone does not seem to cause resistance to this cdk inhibitor.
Insights
Researchers developed a resistant colon cancer cell line to study flavopiridol resistance. While cyclin E levels increased, they alone did not cause resistance to this cyclin-dependent kinase inhibitor.
Area of Science:
- Oncology
- Molecular Biology
- Pharmacology
Background:
- Flavopiridol is a novel cyclin-dependent kinase (CDK) inhibitor used in cancer therapy.
- Acquired resistance can limit the efficacy of anticancer drugs.
- Understanding resistance mechanisms is crucial for optimizing cancer treatment.
Purpose of the Study:
- To establish and characterize an in vitro acquired resistance model for flavopiridol.
- To investigate the mechanisms underlying flavopiridol resistance in cancer cells.
- To assess cross-resistance patterns with other anticancer agents and CDK inhibitors.
Main Methods:
- Developed a flavopiridol-resistant HCT116 colon carcinoma cell line through in vitro drug exposure.
- Assessed cross-resistance to various chemotherapy drugs and other CDK inhibitors.
- Analyzed drug efflux proteins (P-glycoprotein, MRP1) and overall drug accumulation.
- Evaluated flavopiridol's effects on cell cycle arrest, apoptosis, and retinoblastoma protein phosphorylation.
- Investigated the role of cyclin E expression and activity in resistance.
Main Results:
- The resistant cell line exhibited 8-fold resistance to flavopiridol with no cross-resistance to other tested agents.
- Resistance was not mediated by P-glycoprotein or MRP1, nor by altered drug accumulation.
- Flavopiridol induced cell cycle arrest and apoptosis in both cell lines, but required higher concentrations in the resistant line.
- Cyclin E protein levels and kinase activity were elevated in the resistant line.
- Transfection studies indicated that cyclin E overexpression alone does not confer flavopiridol resistance.
Conclusions:
- Flavopiridol resistance can be acquired in colon cancer cells.
- Elevated cyclin E levels are associated with, but not the sole cause of, flavopiridol resistance.
- Further research is needed to elucidate the complete mechanism of flavopiridol resistance.
