Terpenoids and Steroids from Marine Invertebrates: Emerging Anti-metastatic Agents in Cancer Therapy

Metastasis is the principal cause of cancer-related mortality, and existing therapeutic strategies are ineffective in preventing tumour dissemination and metastatic colonisation. Therefore, it is essential to identify drugs that target the molecular processes regulating metastatic progression. Marine invertebrates serve as a remarkably rich source of structurally diverse secondary metabolites, including terpenoids and steroids, many of which exhibit distinctive biological activities unseen in terrestrial natural products. In recent years, increasing evidence has demonstrated that these terpenoids and steroids can suppress metastatic traits by modulating key signalling pathways at non-cytotoxic concentrations. This review offers a comprehensive and critical overview of the anti-metastatic potential of terpenoids and steroids derived from marine invertebrates, with particular emphasis on their ability to regulate epithelial-mesenchymal transition signalling, matrix metalloproteinase-mediated invasion, phosphoinositide 3-kinase and protein kinase B signalling, mitogen-activated protein kinase pathways, nuclear factor kappa B-dependent inflammatory signalling and vascular endothelial growth factor-mediated angiogenesis. In addition, the current challenges in marine anti-metastatic drug discovery are discussed, and future perspectives are outlined. This review highlights marine invertebrate terpenoids and steroids as promising, but underexplored, scaffolds for the development of novel metastasis-modulating therapeutics.