Reversal of tumor growth by gene modification of mesenchymal stem cells using spermine-pullulan/DNA nanoparticles.

Mesenchymal stem cells (MSCs) are a promising tool for delivering of therapeutic agents in cancer treatment. In the present study, our findings suggested that both i.v. and intratumoral injection of MSCs could favor tumor growth under physiologic conditions. However, the anti-tumor effects of MSC-IL-12 were achieved using our strategy. Unlike the previously reported method, the genetic engineering of MSCs was conducted by non-viral transfection using the new vector, spermine-pullulan. The transfection, cytotoxicity, and the cellular internalization of this vector were evaluated. Then, the therapeutical gene, IL-12, was delivered to the MSCs using this vector. The in vitro secretions of IL-12 by MSC-IL-12 confirmed the success of using spermine-pullulan/DNA nanoparticles for the gene transfection. We used the MSC-IL-12 for the in vivo treatment of both B16F10 metastasis tumor and the established subcutaneous B16BL6 tumor. For the B16F10 metastasis tumor, treatment with MSC-IL-12 significantly reduced lung metastases. For the established subcutaneous B16BL6 tumor, intratumoral injected MSC-IL-12 cells considerably retarded tumor growth. Prolonged survival was observed when MSC-IL-12 cells were injected through the tail vein or intratumorally, indicating that the MSCs engineered with the therapeutic gene could reverse the tumor-promoting effects of MSCs using the nonviral transduction method. However, the intravenous injected MSC-IL-12 did not prevent the tumor growth of the established subcutaneous B16BL6 tumor. Thus, we examined the the in vivo distribution of MSCs in different organs and it was found that MSCs were mainly distributed in the lungs, which may explain the inability of intravenously injected MSC-IL-12 to inhibit the growth of the established subcutaneous tumor.