Exosomal proteins as drivers of metastasis to distant organs

Metastasis to distant organs remains the primary cause of cancer-related death worldwide. Although progress has been made in understanding the mechanisms behind metastasis, the processes that drive tumor cells to invade and colonize distant organs remain incompletely understood. Increasing evidence highlights the critical role of exosomal proteins as key regulators in the complex molecular events that facilitate metastatic spread. Tumor-derived exosomes, which contain specific protein cargos, promote invasive behavior, modulate immune responses, increase blood vessel permeability, create a pre-metastatic niche, and support organotropism. Exosomal proteins, such as CEMIP, ITGBL1, integrins (α6β4 and αvβ5), and PD-L1, have been linked to the colonization of distant secondary organs, including the brain, liver, and lungs. Proteomic analysis of circulating exosomal proteins also shows their potential as minimally invasive biomarkers for predicting metastatic potential and disease progression. This review examines the role of exosomal proteins in key mechanisms that directly contribute to cancer dissemination to distant organs. This review also highlights the emerging relevance of exosomal proteins as diagnostic indicators of metastasis and as potential therapeutic targets, positioning them as future dual-purpose tools to improve both detection and intervention strategies in metastatic disease.