Biologic Activity of Oligonucleotides with Polarity and Anomeric Center Reversal

Abstract

Human papillomavirus (HPV) type 16 E6 and E7 inactivate the tumor suppressors p53 and pRB, respectively. Both viral oncoproteins play important roles in maintaining the transformed phenotype of cells. In this study, we examine the effects of antisense oligodeoxynucleotides with polarity and anomeric center reversal (α/β-ODNs). ODNs of the general structure 5′αN3′3′NNN5′5′αN3′3′NNNN5′5′αN3′3′NNNN5′5′αN3′3′N5′ were synthesized using phosphoramidite DNA chemistry. These α/β-ODNs were complementary in sequence to regions flanking the start codons of HPV type 16 E6 and E7 genes. The anti-HPV type 16 α/β-OONs were able to form stable duplexes with their complementary RNA, which then serve as substrates for RNase H hydrolysis. Anti-HPV type 16 α/β-ODNs also specifically inhibited the growth of two cervical carcinoma cell lines, CaSki and SiHa, both of which harbor HPV type 16 DNA. A decrease in E7 protein expression was also observed. Injection of nude mice with SiHa cells induces tumors. Treatment of these tumor-bearing mice with anti-HPV type 16 α/β-ODNs led to substantially smaller tumors. These results show that α/β-ODNs can exert antisense activities both in vitro and in vivo on the E6 and E7 genes of HPV type 16.