Naturally-derived phenethyl isothiocyanate modulates apoptotic induction through regulation of the intrinsic cascade and resulting apoptosome formation in human malignant melanoma cells

Abstract

Malignant melanoma is the most aggressive type of skin cancer with increasing incidence rates worldwide. On the other hand, watercress is a rich source of phenethyl isothiocyanate (PEITC), among others, which has been widely investigated for its anticancer properties against various cancers. In the present study, we evaluated the role of a watercress extract in modulating apoptotic induction in an in vitro model of human malignant melanoma consisting of melanoma (A375, COLO-679, COLO-800), non-melanoma epidermoid carcinoma (A431) and immortalized, non-tumorigenic keratinocyte (HaCaT) cells. Moreover, the chemical composition of the watercress extract was characterized through UPLC MS/MS and other analytical methodologies. In addition, cytotoxicity was assessed by the alamar blue assay whereas apoptosis was determined, initially, by a multiplex activity assay kit (measuring levels of activated caspases −3, −8 and −9) as well as by qRT-PCR for the identification of major genes regulating apoptosis. In addition, protein expression levels were evaluated by western immunoblotting. Our data indicate that the extract contains various phytochemicals (e.g. phenolics, flavonoids, pigments, etc.) while isothiocyanates (ITCs; especially PEITC) were the most abundant. In addition, the extract was shown to exert a significant time- and dose-dependent cytotoxicity against all malignant melanoma cell lines while non-melanoma and non-tumorigenic cells exhibited significant resistance. Finally, expression profiling revealed a number of genes (and corresponding proteins) being implicated in regulating apoptotic induction through activation of the intrinsic apoptotic cascade. Overall, our data indicate the potential of PEITC as a promising anti-cancer agent in the clinical management of human malignant melanoma.

Keywords:

• Watercress
• isothiocyanates
• phenethyl isothiocyanate
• glucosinolates
• malignant melanoma
• apoptosis

Acknowledgments

The human immortalized keratinocyte (HaCaT) cell line was kindly provided by Dr. Sharon Broby (Dermal Toxicology & Effects Group; Centre for Radiation, Chemical and Environmental Hazards; Public Health England, Didcot, UK).

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

All data generated and analyzed in this work are included in this manuscript. Additional data are freely available in the Supplementary materials section.

Additional information

Funding

This research was funded by a grant provided by the (i) Cyprus Institute of Neurology and Genetics, Nicosia, Cyprus under Telethon Cyprus (M.I.P.), (ii) Hellenic Foundation for Research and Innovation (H.F.R.I.) under the ‘First call for H.F.R.I. research projects to support faculty members and researchers and the procurement of high-cost research equipment; Project Number: HFRI-FM17C3-2007’ (A.P and M.I.P) and (iii) ‘OPENSCREEN-GR: An Open-Access Research Infrastructure of Target-Based Screening Technologies and Chemical Biology for Human and Animal Health, Agriculture and Environment’ [MIS 5002691] which is implemented under the Action ‘Reinforcement of the Research and Innovation Infrastructure’, funded by the Operational Programme ‘Competitiveness, Entrepreneurship and Innovation’ [NSRF 2014-2020] and co-financed by Greece and the European Union (European Regional Development Fund) (A.P.).