Development of a novel experimental in vitro model of isothiocyanate-induced apoptosis in human malignant melanoma cells

Background: Isothiocyanates are constituents of cruciferous vegetables which have been associated with reduced cancer risk partially through their ability to induce apoptosis in malignant cells including melanoma. Materials and Methods: We have utilized human malignant melanoma (A375), epidermoid carcinoma (A431) and immortalized keratinocyte (HaCaT) cells exposed to various isothiocyanates, under different experimental conditions. Results: An experimental in vitro model utilizing low isothiocyanate concentrations (0.1-5 μM for 48 h with all treatments being refreshed after 24h) was shown to be (i) most efficient in exerting an anti-cancer effect when compared to higher concentrations (5-100 μM for 24 or 48 h added as a single bolus) and (ii) specific to A375 cells while A431 and HaCaT cells remained unaffected. Such effect involved the activation of several caspases including (iii) initiator caspases 8, 9, 4 (indicating the involvement of intrinsic, extrinsic and endoplasmic reticulum-based pathways) and (iv) effector caspases 3, 7 and 6. Conclusion: Utilization of low isothiocyanate concentrations (under the conditions described herein) exerts an anti-cancer effect specific to human malignant melanoma cells thus providing a therapeutic basis for their utilization in management of the disease.