Myogenin promoter-controlled oncolytic adenovirus selectively kills rhabdomyosarcoma cells

Abstract

The specific cytogenetic abnormality in about 60% of patients with alveolar rhabdomyosarcoma (RMS) is the fusion gene PAX3-FOXO1 (P3F), and the prognosis of P3F-positive RMS is much worse than those of P3F-negative RMS. Thus, novel therapeutics for the treatment of P3F-positive RMS are desperately needed. Myogenic differentiation 1 (MyoD) and myogenin (MYOG) play important roles in skeletal muscle differentiation. Both MyoD and P3F are upstream regulators of MYOG. Interestingly, it was reported that when the MEF2 binding site in the MYOG promoter (pMYOG) was mutated (mMEF2), MyoD transactivation was abolished, but the P3F transactivation was not affected. Two RMS cell lines, Rh30 (P3F-positive) and RD (P3F-negative), and normal skeletal muscle cells (SkMC) were used in the following experiment. We prepared pMYOG-controlled OAd (M-OAd) with and without mMEF2 (M-OAd-WT and M-OAd-m, respectively) and evaluated their characteristics. In the comparison of the cytolytic effect of M-OAd on RMS cells, both M-OAds were found to kill Rh30 cells under a low titer condition that can be used clinically, whereas M-OAd-m showed a one order of magnitude lower cytolysis in RD than M-OAd without mMEF2. Neither M-OAds replicated nor killed SkMC. In an in vivo study, both M-OAds strongly suppressed tumor growth derived from Rh30 regardless of the presence or absence of mMEF2, and they could spread intratumorally as much as the multitargeted positive control virus. Our findings indicated the applicability of the MYOG promoter to the design of the oncolytic adenovirus for RMS. Additionally, M-OAd might be useful for enhancing its specificity and safety with mutation in the MEF2 binding site.