Objective: To investigate and compare the efficacy of all-trans retinoic acid (RA) and/or interferon-alpha (IFN-alpha) on premalignant and malignant models of cervical cancer.
Methods: Cell growth rate was examined after treatment for 4, 7, and 10 days with RA and/or IFN-alpha of human papillomavirus type 18 (HPV 18)-immortalized endo- and ectocervical cells, nontransformed serum-adapted cells, transformed cells, three adenocarcinoma, and three squamous cell carcinoma cell lines. The effect on epithelial differentiation by RA and IFN-alpha was examined in organotypic culture. Induction of apoptosis was examined by modified terminal transferase-mediated deoxyuridine triphosphate-biotin nick end-labeling (TUNEL) and DNA fragmentation.
Results: Cell growth rate was inhibited by RA, 84-96% in HPV 18-immortalized endocervical cells, SiHa, and ME180, 0% in OMC-4, and 18-62% in other cell lines; and by IFN-alpha about 75% in SiHa and ME180 and 14-40% in the other cell lines. Combining RA and IFN-alpha increased the antiproliferative effect in premalignant cell lines and some cancer cell lines except OMC-4, SiHa, and HT-3. In rafts, RA treatment reversed human endocervical cell metaplasia and HPV 18-immortalized endo- and ectocervical cell dysplastic epithelial differentiation. Interferon-alpha, not RA, treatment of HPV 18-immortalized endo- and ectocervical cells induced apoptosis.
Conclusion: Cell growth inhibition by treatment with RA, IFN-alpha, and their combination differentially depends on treatment type and time, cell origin, cell line, and oncogenic state. In a premalignant model of cervical carcinoma, RA reduces dysplastic differentiation and IFN-alpha induces apoptosis. These data confirm that these treatments may be effective for preventing or treating premalignant cervical lesions.