Cancer Immunity 4:6 (2004)

RNA interference of IL-10 in leukemic B-1 cells

Brian A. McCarthy, Amal Mansour, Yi-Chu Lin, Sergei Kotenko, and Elizabeth Raveche

UMDNJ-New Jersey Medical School, Department of Pathology and Laboratory Medicine, Newark, NJ, USA

Keywords: chronic lymphocytic leukemia, B-1 cell line, RNA interference, IL-10, cell cycle, apoptosis

Abstract

RNA interference, or RNAi, is designed to work by Watson-Crick base pairing and to result in a posttranscriptional block in protein synthesis. Antiapoptotic proteins are a major focus of cancer therapy and make attractive targets for RNAi. An IL-10 RNAi sequence was designed in accordance with Tuschl rules and was modeled to a hairpin configuration. In chronic lymphocytic leukemia (CLL), the most common leukemia in the Western world, the failure to undergo apoptosis may be responsible for the accumulation of malignant B-1 cells. Interleukin-10, despite controversy, has been shown to have antiapoptotic properties, and increased endogenous IL-10 production has been found in CLL by several labs. A malignant B-1 cell line, LNC, derived from an NZB mouse (a murine model for CLL) was utilized as a target for IL-10 RNAi. Our earlier studies of antisense IL-10 resulted in antiproliferative and proapoptotic effects. The cytotoxic effects of IL-10 RNAi were dose- and time-dependent, with an optimal dose 10-fold lower than that of antisense IL-10. IL-10 RNAi lowered IL-10 protein as measured by ELISA. 2 µM IL-10 RNAi initiated a G2/M block and a decrease in the message for cdc25C, the M-phase inducer phosphatase. IL-10 RNAi efficiently induced apoptosis. Bcl7C, a member of the antiapoptotic Bcl family, was significantly down-regulated. IL-10 modulating Bcl7C expression represents a novel mechanism in the evasion of apoptosis. This approach, by itself or in conjunction with current therapies, merits consideration in similar B-cell malignancies.