Systemic delivery of HK Raf-1 siRNA polyplexes inhibits MDA-MB-435 xenografts

Area of Science:

• Biotechnology
• Nanotechnology
• Molecular Biology

Background:

• Histidine-lysine-rich (HK) polymers are investigated as carriers for nucleic acid delivery.
• Previous in vitro studies showed branched HK polymers complexed with Raf-1 siRNA reduced Raf-1 mRNA and induced apoptosis.

Purpose of the Study:

• To evaluate the in vivo efficacy of HK polymers for systemic siRNA delivery to tumor xenografts.
• To determine if a specific branched HK polymer, H3K(+H)4b, can inhibit MDA-MB-435 xenograft growth when complexed with Raf-1 siRNA.

Main Methods:

• Comparison of HK:Raf-1 polyplexes for in vivo efficacy in a mouse model.
• Administration of H3K(+H)4b:Raf-1 siRNA via tail-vein injection.
• Assessment of tumor size, histological changes, apoptosis, vascularization, and Raf-1 protein levels.

Main Results:

• Statistically significant tumor size reduction after the first tail-vein injection of H3K(+H)4b:Raf-1 siRNA (P<0.01).
• Nearly 50% tumor reduction by the third injection compared to controls.
• Increased apoptosis, decreased vascularization, and reduced Raf-1 protein in tumors.
• Minimal toxicity observed in normal tissues.

Conclusions:

• Branched HK polymer H3K(+H)4b is an effective carrier for systemic delivery of Raf-1 siRNA in vivo.
• This siRNA delivery strategy significantly inhibits tumor growth and reduces Raf-1 protein levels.
• HK polymers show potential for developing targeted cancer therapies with low toxicity.