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Sponges are known to produce a series of compounds with bioactivities useful for human health. This study was conducted on four sponges collected in the framework of the XXXIV Italian National Antarctic Research Program (PNRA) in November-December 2018, i.e., Mycale (Oxymycale) acerata, Haliclona (Rhizoniera) dancoi, Hemimycale topsenti, and Hemigellius pilosus. Sponge extracts were fractioned and tested against hepatocellular carcinoma (HepG2), lung carcinoma (A549), and melanoma cells (A2058), in order to screen for antiproliferative or cytotoxic activity. Two different chemical classes of compounds, belonging to mycalols and suberitenones, were identified in the active fractions. Mycalols were the most active compounds, and their mechanism of action was also investigated at the gene and protein levels in HepG2 cells. Of the differentially expressed genes, ULK1 and GALNT5 were the most down-regulated genes, while MAPK8 was one of the most up-regulated genes. These genes were previously associated with ferroptosis, a programmed cell death triggered by iron-dependent lipid peroxidation, confirmed at the protein level by the down-regulation of GPX4, a key regulator of ferroptosis, and the up-regulation of NCOA4, involved in iron homeostasis. These data suggest, for the first time, that mycalols act by triggering ferroptosis in HepG2 cells.

Human anaplastic thyroid carcinoma (ATC) cells which stably express antisense construct against nuclear high-mobility group A (HMGA) proteins were used in a novel phenotypic assay for screening marine natural extracts. The rational search led to the isolation and identification of a novel polyoxygenated linear lipid (1) that showed important and selective cytotoxicity against ATC-derived tumor cell lines.

The marine metabolite mycalol (1) has a specific inhibitory activity on cells of anaplastic thyroid carcinoma (ATC), a very aggressive and rare cancer that does not have effective conventional therapy. In this study, we describe six new related analogues (2-7) that differ in the length of the terminal alkyl residue and the presence of acetate or 3S-hydroxybutyrate (3S)-3HB as a substituent at C-19. Despite the structural analogies, some of the new members were significantly more cytotoxic than 1 on cell lines derived from human ATC. Structures inclusive of the 2'R,3R,4S,7R,8S,19R absolute configuration were assigned to 2-7 on the basis of detailed spectroscopic analysis, synthesis of different isomers, and application of ECD and Mosher's methods. This work led to the identification of mycalol-578 (3) as the most potent analogue, with an IC50 of 2.3 muM on FRO cells.