Molecular Mechanisms Driving Metastatic Progression Within the Aged Tumor Microenvironment

Metastasis remains the leading cause of cancer deaths, heavily influenced by aging-related biological processes. As global life expectancy increases, cancer incidence and progression complexity in older adults also rise, emphasizing the urgent need to understand how the aging tumor microenvironment (TME) promotes metastasis. This review explores the molecular and cellular mechanisms behind metastatic development in the aged TME, focusing on the combined impacts of cellular senescence, chronic inflammation (inflammaging), immune system decline, extracellular matrix (ECM) changes, and abnormal blood vessel growth. Aging causes an accumulation of senescent cells that secrete a range of cytokines, growth factors, and enzymes (SASPs), which remodel the ECM, making it stiffer and more degradable, and activate pro-metastatic pathways like TGF-β, STAT3, and MAPK, aiding processes like EMT and tumor invasion. Meanwhile, persistent low-grade inflammation attracts immunosuppressive cells, and immune decline hampers tumor surveillance, allowing cancer cells to evade immune detection. The aged TME also undergoes significant vascular and metabolic changes, such as abnormal angiogenesis and hypoxia, supporting the growth of more aggressive, treatment-resistant cancer clones and spreading metastases. These changes are driven by hallmarks of molecular aging, including telomere shortening, oxidative DNA damage, and epigenetic alterations, which lead to genetic instability and turn the aged stroma into fertile ground for metastasis. The review also discusses new therapeutic approaches, including senolytics, anti-inflammatory treatments, immune system rejuvenation, and metabolic strategies, highlighting the importance of age-specific models and precision medicine to enhance outcomes for the growing number of elderly cancer patients.