Aging is one of the biggest risk factors for cancer development. Over 85% of all cancers occur in individuals aged over 55 years, often accompanied by age-associated immune defects. Previous studies on the tumor microenvironment (TME) during aging have identified several factors, such as the roles of fibroblasts, immunosuppression, and metastasis. However, the aging-associated defects in anti-tumor immunity, particularly regarding T cells, remain underexplored. Recent findings by Zhivaki and colleagues suggest that age-related immune defects affecting anti-tumor responses involve reduced levels of CD8+ T cells and compromised dendritic cell (DC) functions such as antigen presentation and migration. Their study demonstrates that a hyperactive DC vaccine can restore DC functions in older mice. Furthermore, these hyperactive DCs, characterized by increased IL-1β production and better migratory capability to the lymph node, promote the development of cytolytic CD4+ T cells exhibiting Th1-like phenotypes. This research reveals mechanisms underlying the response to hyperactive DC vaccines in older mice and highlights the critical role of cytolytic CD4+ T cells as substitutes for CD8+ T cells in driving anti-tumor immunity and achieving long-term tumor control in older mice.