Abstract：OBJECTIVE: To evaluate two small interfering RNAs (siRNAs) on the NPM-ALK fusion gene expression in anaplastic large-cell lymphoma cell line Karpas299, and to study the effect of RNA interference on Karpas299 cells proliferation. METHODS: Two siRNAs sequences (siRNA- I and siRNA-II) were designed to target the NPM-ALK fusion site in anaplastic large-cell lymphoma cell line Karpas299. An siRNA U6 expression system including U6 RNA-based polymerase III promoter was set up. The two siRNAs designed for down-regulation of the NPM-ALK fusion mRNA were transfected into Karpas299 cells by liposomal transfection reagents. The effect of RNAi on NPM-ALK mRNA expression was detected by real-time RT-PCR and Western blot. The anti-proliferative effects of the siRNA U6 system were assessed using MTT. Apoptosis was observed by fluorescence microscopy. RESULTS: The mRNA level of NPM-ALK in Karpas299 cells transfected with siRNA-I and siRNA-II decreased by approximately 75% and 35% respectively. The NPM-ALK protein expression was inhibited in Karpas299 cells at 72 hrs of siRNA-I transfection. The siRNA-II treatment had no effect on NPM-ALK protein expression. siRNA-I had inhibitory effects on Karpas299 cells proliferation and induced the cells apoptosis, while siRNA-II did not. CONCLUSIONS: Sequence specific siRNAs targeting NPM-ALK was capable of suppressing NPM-ALK expression and inhibiting cellular proliferation. RNA interference may be a suitable technique for studying the function of NPM-ALK gene and may be used to develop siRNA-based targeted gene therapeutic approaches against NPM-ALK-positive lymphomas.
