Ribozyme targeting HPV16 E6E7 transcripts in cervical cancer cells suppresses cell growth and sensitizes cells to chemotherapy and radiotherapy

Human Papillomavirus (HPV) is related to more than 90% of cervical cancer. The virus is shown to be essential for the induction and maintenance of the malignant phenotype in cervical cancer. In this report, we designed a hammerhead ribozyme Rz170 to specifically target the HPV16 E6E7 transcripts, and our results demonstrated that Rz170 can cleave HPV16 E61E7 transcripts effectively and with high specificity. When transfected into a HPV 16 positive cervical cancer cell, CaSKi, the ribozyme reduced the expression of HPV16 E6 and E7 mRNA, and inhibited cell growth both in vitro and in vivo. The percentage of apoptosis cells was also increased. We found that Rz170 reduced the expression of the viral E6 and E7 proteins, and cellular c-myc, bcl-2 proteins, but increased the expression of p53 and Rb proteins. It is likely that the ribozyme inhibited cervical cancer cell growth by reducing the expression of the HPV16 E6 and E7gene, which may alter the expression of p53, Rb, c-myc and bcl-2, and led to apoptosis in cancer cells. We also found that CaSKi cells transfected with Rz170 showed increased sensitivity to cisplatin and radiation. Our study demonstrated the potential of Rz170 for treating cervical cancer, and the possibility of using a combined therapeutic strategy involving ribozyme, chemotherapy or radiotherapy.