Novel oncolytic adenovirus selectively targets tumor-associated polo-like kinase 1 and tumor cell viability.

PURPOSE: Polo-like kinase 1 (plk1) is a serine/threonine protein kinase essential for multiple mitotic processes. Previous observations have validated plk1 as a promising therapeutic target. Despite being conceptually attractive, the potency and specificity of current plk1-based therapies remain limited. We sought to develop a novel plk1-targeting strategy by constructing an oncolytic adenovirus to selectively silence plk1 in tumor cells. EXPERIMENTAL DESIGN: Two artificial features were engineered into one wild-type adenovirus type 5 (wt-Adv5) genome to generate a new oncolytic adenovirus (M1). First, M1 contains a 27-bp deletion in E1A region, which confers potent, oncolytic efficacy. Second, M1 is armed with a fragment of antisense plk1 cDNA that substitutes the E3 region encoding 6.7K and gp19K. In this design, tumor-selective replication of M1 would activate the native adenovirus E3 promoters to express the antisense plk1 cDNA preferentially in tumor cells and silence tumor-associated plk1 protein. RESULTS: By virtue of combining oncolysis with plk1 targeting, M1 exhibited potent antitumoral efficacy in vitro and in vivo. Systemic administration of M1 plus cisplatin induced complete tumor regression in 80% of orthotopic hepatic carcinoma model mice that were otherwise resistant to cisplatin and disseminated metastases. CONCLUSIONS: Coupling plk1 targeting with oncolysis had shown superior antitumor efficacy. Present findings would benefit the development of novel oncolytic adenoviruses generally applicable to a wide range of molecule-based therapeutics.

Selective targeting of checkpoint kinase 1 in tumor cells with a novel potent oncolytic adenovirus.

DNA-damage checkpoints are activated to arrest cells and promote survival upon genotoxic challenge. Efforts have been taken to target checkpoint kinase 1 (chk1; approved gene symbol CHEK1), a crucial checkpoint modulator, for therapeutic intervention. However, improvement of the potency and specificity of such therapeutics remains a major challenge. This prompted us to develop a novel chk1-targeting strategy by constructing a potent oncolytic adenovirus (M2). M2 was generated by combining two artificial features into a wild-type adenovirus type 5 genome. First, M2 was engineered with a 27-bp deletion in the E1A region to confer tumor-selective replication. Second, an antisense chk1 cDNA was substituted for viral E3 6.7K and gp19K genes. In this design, M2 exploited the adenovirus E3 promoters to express antisense chk1 cDNA in a viral replication-dependent fashion and preferentially silenced the chk1 gene in tumor cells. By virtue of combining oncolysis with chk1 targeting, M2 exhibited potent antitumoral efficacy in vitro and in vivo. Systemic administration of M2, plus a low dose of cisplatin, cured 80% of orthotopic hepatic carcinoma mouse models that were otherwise resistant to cisplatin. These findings have directed us toward the development of novel oncolytic adenoviruses that will be potentially applicable to a wide range of molecular-based therapeutics.