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The cytotoxicity of the diterpene alcohol, phytol, was evaluated by using the MTT assay in vitro against seven tumour cells and one normal cell of human origin. The compound tested induced concentration-dependent cytotoxic response in all cell lines, demonstrating to be most and least effective against the breast adenocarcinoma MCF-7 and the prostate adenocarcinoma PC-3 cells, respectively (IC50 8.79 ± 0.41 μM and 77.85 ± 1.93 μM). The IC50 values towards the other five tumours (HeLa, HT-29, A-549, Hs294T and MDA-MB-231) ranged from 15.51 to 69.67 μM. However, mild toxicity was detected against the foetal lung fibroblast MRC-5 cells at the concentrations used (IC50 124.84 ± 1.59 μM). According to the experimental data obtained, this cost-effective natural product widely present in the biosphere may inspire the development of new drug-like substances with improved cytotoxic activity on breast cancer.

TNF-α can induce cell death (apoptosis and necrosis), and these effects mostly depend on expression of TNF-receptor superfamily molecules. As determination of certain intracellular enzymes like LDH, released from cultured tumor cells, reflects early membrane alterations, we compared LDH release with changes in cell surface membrane molecule expression during culture of K-562 cells in the presence of TNF-α. TNF-α-mediated CD45 and CD30 shedding is shown to be to be time- and dose-dependent and associated with significant increase in LDH release, with maximal effects after 24 h of treatment. The percentage of decrease of all examined cell surface molecules on K-562 cells after TNF-α treatment was not uniform and appeared to depend on the respective constitutive level of expression and molecule type. The presence of these molecules was confirmed in supernatants using Western blot analyses. These results indicated the complexity of events on the cell membrane, including early LDH release that is associated with a difference in shedding of CD30 and CD45. Shedding of CD30 occurs before apoptosis induction, while shedding of CD45 is associated with apoptosis.