Small interfering RNA targeting Raf-1 inhibits tumor growth in vitro and in vivo

Abstract

Raf-1 is a cytosolic serine-threonine kinase that plays an important role in tumor cell growth, proliferation, and apoptosis. Upregulated Raf-1 activity has also been implicated in tumor angiogenesis and metastasis. In this study, we used a promising new RNA interfering technology that targets Raf-1 mRNA both in vitro and in vivo. We initially found that Raf-1 siRNA markedly reduced Raf-1 mRNA in MDA-MB-435 cells in vitro by approximately 75% compared to control siRNA treatment groups. Raf-1 siRNA also reduced cell number by inducing apoptosis in a number of cell lines including HUVEC, MDA-MB-435, and C6 cells. After screening several histidine-lysine polymers in complex with Raf-1 siRNA to reduce tumor growth, we further evaluated the efficacy of this siRNA in complex with the optimal histidine-lysine carrier to reduce the tumor growth in vivo. MDA-MB-435 xenografts treated by intratumoral injections of Raf-1 siRNA were significantly reduced compared with the control groups. By the fourth measurement, tumor growth was reduced by nearly 60% in the Raf-1 siRNA treatment group compared with the untreated group (Po.02). Taken together, our data provide evidence that Raf-1 siRNA may be an effective strategy for reducing tumor growth.

The silent treatment: siRNAs as small molecule drugs

“…In the lung and vagina, siRNA uptake is extremely efficient and occurs even in the absence of transfection reagents. 42 For clinical indications where siRNAs only need to be delivered to a localized region, such as the eye, 71,72 pulmonary 73 or vaginal mucosa, 74 or superficial tumors, [75][76][77][78] efficient siRNA delivery and silencing can be achieved by mixing siRNAs with cationic lipid transfection reagents used for in vitro transfection and directly injecting the siRNAlipid complexes into the relevant tissue or instilling it into the body cavity. A similar approach is certain to apply to the skin.…”

Raf kinases: Oncogenesis and drug discovery

“…149 Reduction of in vivo tumor growth by application of C-RAF siRNA was also reported in xenograft models of human prostate 150 and also breast cancer. 151 The benzoquinone ansamycin Geldanamycin (GA) was originally isolated as compound with antifungal activities and was later found to reduce oncogene-dependent proliferation of tumor cells; for review see Ref. 152.…”

In vivo gene silencing in solid tumors by targeted electrically mediated siRNA delivery

“…7,18 However, few data have been published reporting the successful use of siRNA for gene silencing in developing tumors in vivo in rodent model systems. 14,[19][20][21][22][23][24] Surprisingly, Filleur et al 22 found that in mice direct microinjection of the siRNA solution into the tumor was ineffective whereas systemic administration methods induced significant gene knockdown in the tumor tissue. In contrast, Takahashi et al 23 suggested that effective gene suppression could be obtained after direct intratumoral microinjection of the siRNAs followed by in situ electroporation.…”