The Immmonoproapoptotic Molecule ScFv-Fdt-tBid Modified Mesenchymal Stem Cells For Prostate Cancer Dual-targeted Therapy

Prostate cancer is the second common cancer affecting men around the world and the incidence of prostate is increasing steadily in developing countries. A t present a variety of treatments existed for prostate cancer, while for metastatic and hormone- independent prostate cancer there are no effective standard therapy strategies. Our group focuss on the target therapy strategies for prostate cancer, and we designed a signal chain antibody gene for prostate specific antigen(PSA). Here we designed a recombinant targeted gene sc Fv-Fdt-t Bid. The sc Fv-Fdt-t Bid consists of three ingredients, the signal chain antibody against PSA, the translocation domain Fdt, and the apoptosis induction t Bid. To our knowledge, this is the first immunoproapoptotic molecule which combined PSA-specific antibody with endogenous apoptotic-inducing protein molecule.However, multiple factors such as the long diatance of circulation, poor penetration through the tumor and the short half life in plasma of recombinant molecule influence the in vivo antitumor activity of recombinant immunoproapoptotic molecules.Mesenchymal stem cells is a kind of adult stem cell, because of their specific tumor tropism, the feasibility of self- transplantation and the stability of gene modify, MSCs were selected as a cell vehicle for gene therapy. MSCs also make an attractive choice for cell vehicle as their easy acquisition, amplification. Thus, we conceived to combine recombinant PSA-targeted killing molecule sc Fv-Fdt-t Bid with MSC tumor tropism to constructe a dual-target therapeutic system for prostate cancer. In this system, MSC can effectively and specifically tend to the tumor sites and lasting secreted recombinant protein result in a powerful PSA-restricted antitumor effect with no toxic effects on normal cells.In vitro, the sc Fv-Fdt-t Bid can effectively produce and secret the fusion protein in MSC and showed considerable PSA-restricted inhibitory on cell viabilities. The MSC modified by sc Fv-Fdt-t Bid did not show significant changes in their proliferation and tumor tropism, while the powerful apoptosis-inducing effects on PSA-positive cells were detected. The intrinsic apoptosis were induced with the cleavage and activity of caspases-3.In vivo, the MSC could effectively target to tumor sites and release the recombinant protein constantly. As a result, localized high concentrations of sc Fv-Fdt-t Bid exhibited powerful anticancer potential. The size of tumor in MSC.sc Fv-Fdt-t Bid treated mice was smaller than that of MSC.sc Fv-t Bid or MSC.EGFP treated mice and significant differences were tested at last. Meanwhile, no difference about the tumor size was founded between MSC group and PBS group. The live enzymes also detected and no changes were found among all groups, which indicate a good safety profile with this dual-target system for prostate therapy.In summary, our dual- target system has shown a potent inhibiting effect on prostate cancer. This dual-target system is an important complement to convent ional antibody targeting molecules therapeutic strategies, and it laid an important theoretical and experimental basis for the clinical application of recombinant targeted killing molecules.