Small interfering RNAs targeting cyclin D1 and cyclin D2 enhance the cytotoxicity of chemotherapeutic agents in mantle cell lymphoma cell lines

Abstract

Cyclin D1 (CCND1) is a known cell cycle regulator whose overexpression is a hallmark of mantle cell lymphoma (MCL). Although molecular techniques have unified the diagnostic approach to MCL, no therapeutic advances have been made to target this particular pathway. The significance of CCND1 in the pathogenesis and treatment of MCL has yet to be defined. We have taken advantage of RNA interference (RNAi) to down-regulate CCND1 expression in two MCL cell lines (Granta-519 and Jeko-1) to investigate the cytotoxic effect of combining RNAi with conventional chemotherapeutic agents. We designed four small interfering RNAs (siRNAs) specific to CCND1, one specific to CCND2, and one dual-targeting siRNA that simultaneously down-regulates CCND1 and CCND2. Etoposide and doxorubicin were used as chemotherapeutics in combination with the siRNAs. The transfected siRNAs in MCL cell lines triggered 40–60% reduction in target mRNA and protein levels. Importantly, the siRNA-mediated reduction in cyclins resulted in decreased IC₅₀ (50% inhibitory concentration) values for both doxorubicin and etoposide. The combination of siRNA-mediated inhibition of the cyclins along with chemotherapeutic agents could potentially be used to lower the effective doses of the chemotherapeutic agents and reduce drug-related toxicities.

Keywords::

• Cell cycle and apoptosis changes
• cell lines and animal models
• gene therapy
• lymphoma and Hodgkin disease

Acknowledgements

The authors would like to thank Britta Hoehn for her help in designing the cyclin D1 siRNAs, John Burnett for providing the cyclin D2 siRNA and helpful discussions, Pål Sætrom for designing the dual-targeting cyclin D1/D2 siRNA, and Ka-Ming Pang for helpful suggestions in problem solving.

This work was supported by grants from the National Cancer Institute (P30 CA33572), Think Cure, by the Keck Foundation. The Tim Nesvig Lymphoma Fellowship and Research Fund and the Tower Cancer Research Foundation.

Potential conflict of interest:

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