In vitro study of natural compounds and their semi-synthetic derivatives as inducers of non-canonical cell death

The ability of cancer cells to evade apoptosis and become resistant to pro-apoptotic antitumor agents is well documented. Non-apoptotic (or non-canonical) programmed cell death pathways, as ferroptosis and necroptosis, are increasingly recognized as novel potential intervention targets that could improve anticancer treatments. Several natural compounds exert their antitumor activity by triggering non-canonical cell death. In this thesis, the natural isothiocyanate sulforaphane (SFN), two semi-synthetic isothiocyanate derivatives (MG28 and MG46), and one semi-synthetic indole derivative (AD05) were evaluated for their in vitro anticancer activity, including the ability to elicit non-canonical cell death, on multiple leukemia cancer cell lines. MG28 and MG46 exhibited a more marked cytotoxic effect than SFN but prompted exclusively caspase-dependent apoptosis. Conversely, SFN promoted different cell death modalities in a dose-dependent manner. At relatively low doses, it induced caspase-dependent apoptosis; at higher concentrations, it triggered ferroptosis, necroptosis, parthanatos, and MPT-driven necrosis. Also, we demonstrated that SFN, but not MG28 and MG46, promotes the extracellular release of HMGB1 (High Mobility Group Box 1) that could be primordially attributed to its ability to induce non-canonical cell death. Regarding AD05, its cytotoxic potential was associated with a block in cell-cycle progression at the G2/M phase. Moreover, AD05 triggered both intrinsic and extrinsic apoptosis, an event closely associated with its ability to block cancer cells’ proliferation. Apoptosis, however, was the unique mechanism of cell death activated by AD05. From a toxicological perspective, we proved that MG28 and MG46 were able to induce DNA damage, while AD05 lacked any genotoxic effect. In conclusion, our results indicate that only SFN triggers multiple forms of non-canonical cell death. Conversely, MG28, MG46 and AD05, despite having exhibited a marked antitumor activity, induce exclusively caspase-dependent apoptosis in leukemia cancer cells.