SP94-Targeted Triblock Copolymer Nanoparticle Delivers Thymidine Kinase-p53-Nitroreductase Triple Therapeutic Gene and Restores Anticancer Function against Hepatocellular Carcinoma in Vivo.

Gene-directed enzyme-prodrug therapy (GDEPT) is a promising approach for cancer therapy, but it suffers from poor targeted delivery in vivo. Polyethylenimine (PEI) is a cationic polymer efficient in delivering negatively charged nucleic acids across cell membranes; however, it is highly toxic in vivo. Hence, we efficiently reduced PEI toxicity without compromising its transfection efficiency by conjugating it with poly(d,l-lactic--glycolic acid) (PLGA) and poly(ethylene glycol) (PEG) as triblock copolymers through a multistep synthetic process. The synthesized nanoparticles showed efficient delivery of loaded nucleic acids to tumor cells in vitro and in vivo in mice. We used this nanoparticle to deliver a rationally engineered thymidine kinase (TK)-p53-nitroreductase (NTR) triple therapeutic gene against hepatocellular carcinoma (HCC), where p53 tumor suppressor gene is mutated in more than 85% of cancers. TK-p53-NTR triple gene therapy restores p53 function and potentiates cancer cell response to delivered prodrugs (ganciclovir (GCV) and CB1954). We used SP94 peptide-functionalized PLGA-PEG-PEI nanoparticles for the optimal delivery of TK-p53-NTR therapeutic gene in vivo. The nanoparticles prepared from the conjugated polymer showed high loading efficiency for the DNA and markedly enhanced TK-NTR-mediated gene therapy upon the simultaneous coexpression of p53 by the concurrent rescue of the endogenous apoptotic pathway in HCC cells of both p53-mutant and wild-type phenotypes in vitro. In vivo delivery of TK-p53-NTR genes by SP94-targeted PLGA-PEG-PEI NP in mice resulted in a strong expression of suicide genes selectively in tumors, and subsequent administration of GCV and CB1954 led to a decline in tumor growth, and established a superior therapeutic outcome against HCC. We demonstrate a highly efficient approach that exogenously supplements p53 to enable synergy with the outcome of TK-NTR suicide gene therapy against HCC.