The majority of precancerous lesions of the uterine cervix are treated with surgery or ablative therapy; however, these treatments may have negative reproductive consequences in young women and may fail to remove all affected areas. Prior work from our group has indicated that treatment with a naturally occurring compound, Indole-3-carbonol (I3C) induces regression of cervical intraepithelial neoplasia (CIN). Therefore, the use of chemopreventive agents in healthy women at high risk for developing cervical cancer (women with a pre-malignant lesion or infection with high risk HPV) may be a non-invasive and cost effective method for the treatment of CIN. This study determined the effects of potential chemopreventive compounds on the proliferation of cervical cancer cells and analyzed the effect of I3C on E-Cadherin expression in samples obtained from the I3C clinical trial.
Methods: We have assessed the effects of 4 naturally occurring compounds on a panel of cervical cancer cell lines. I3C, diindolylmethane (DIM, a condensation product of I3C) and benzyl isothiocyanate (BITC) are each found in cruciferous vegetables (such as cabbage and broccoli) and Curcumin is the active ingredient in the Indian curry spice tumeric. Proliferation assays using the CellTiter96 Aqueous One Solution (Promega) were performed with cervical cancer cell lines that were exposed to biologically relevant concentrations of I3C, DIM, BITC and Curcumin for 24, 48 and 72 hours. The expression pattern of E-Cadherin (as determined by immunohistochemistry) was analyzed in paired cervical tissue samples (before and after treatment from placebo and I3C treatment groups) obtained from the I3C clinical trial.
Results: Each compound showed a time and dose dependent inhibition of proliferation in HeLa, SiHa, CaSki and C33A cell lines, with Curcumin being the most inhibitory at a low concentration (15µM). Additionally, when used in combination (BITC + Curcumin, I3C + Curcumin and DIM + Curcumin) the compounds were more effective as they showed a more pronounced inhibititory effect on cellular proliferation. In a phase II clinical trial, treatment with I3C induced the regression of CIN. E-Cadherin is known to be aberrantly expressed in dysplastic cells, and immunohistochemical analysis of cervical tissues revealed that I3C treatment was associated with modulation of E-Cadherin towards a more normal expression pattern.
Conclusion: We have shown that BITC, DIM, I3C, and Curcumin each inhibit cellular proliferation of cervical cancer cell lines. Additionally, the inhibition was greater when the compounds were used in combination; therefore, we predict that curcumin prevents proliferation through a different mechanism than BITC, DIM or I3C. Our results indicate that these chemopreventive compounds may successfully treat women with precancerous lesions of the cervix.
98th AACR Annual Meeting-- Apr 14-18, 2007; Los Angeles, CA