Abstract
Pleiotrophin (PTN) is a secreted cytokine that is expressed in various cancer cell lines and human tumor such as colon cancer, lung cancer, gastric cancer and melanoma. It plays significant roles in angiogenesis, metastasis, differentiation and cell growth. The expression of PTN in the adult is limited to the hippocampus in an activity-dependent manner, making it a very attractive target for cancer therapy. RNA interference (RNAi) offers great potential as a new powerful therapeutic strategy based on its highly specific and efficient silencing of a target gene. However, efficient delivery of small interfering RNA (siRNA) in vivo remains a significant hurdle for its successful therapeutic application. In this study, we first identified, on a cell-based experiment, applying a 1:1 mixture of two PTN specific siRNA engenders a higher silencing efficiency on both mRNA and protein level than using any of them discretely at the same dose. As a consequence, slower melanoma cells growth was also observed for using two specific siRNA combinatorially. To establish a robust way for siRNA delivery in vivo and further investigate how silence of PTN affects tumor growth, we tested three different methods to deliver siRNA in vivo: first non-targeted in-vivo delivery of siRNA via jetPEI; second lung targeted delivery of siRNA via microbubble coated jetPEI; third tumor cell targeted delivery of siRNA via transferrin-polyethylenimine (Tf-PEI). As a result, we found that all three in-vivo siRNAs delivery methods led to an evident inhibition of melanoma growth in non-immune deficiency C57BL/6 mice without a measureable change of ALT and AST activities. Both targeted delivery methods showed more significant curative effect than jetPEI. The lung targeted delivery by microbubble coated jetPEI revealed a comparable therapeutic effect with Tf-PEI, indicating its potential application for target delivery of siRNA in vivo.
Highlights
Melanoma is the deadliest skin cancer, which is an increasing worldwide health problem because of its highly aggressive and drug-resistant nature
The growth curve revealed the addition of the recombinant PTN enhanced B16-F10 cells proliferation (Fig 1B), suggesting B16-F10 cell growth was still responsive to PTN stimulation and could employ it for autocrine signaling
Several studies reported about the off-target effects of the highly specific small interfering RNA (siRNA)[29,30,31], which arises from the partial sequence complementarity of the siRNA used with non-targeted mRNA and competition with cellular micro RNA processes
Summary
Melanoma is the deadliest skin cancer, which is an increasing worldwide health problem because of its highly aggressive and drug-resistant nature. A major biological characteristic of metastatic melanomas is their ability to survive in a growth factor lacking environments. They used the autocrine signalling to secret cytokines and growth factor for self-stimulation[2]. PTN is highly expressed in the central and peripheral nervous system during embryonic and early postnatal development[5]. It plays multiple roles in neuronal development, hepatic regeneration, bone repair, skeletal remodeling and other physiological processes[6,7,8,9]. PTN becomes an attractive target for cancer gene therapy
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