Emerging New Pathways in Malignant Neoplasms and Neurodegenerative Disorders: Perspectives for Therapeutics.

Neurodegenerative disorders such as Alzheimer's disease (AD) and malignant neoplasms are among the most prevalent age-associated diseases worldwide. Although cancer is characterized by uncontrolled proliferation, resistance to apoptosis, and metabolic reprogramming, AD and other neurodegenerative disorders such as Lewy body disease (LBD) including Parkinson's Disease (PD) and fronto-temporal lobar degeneration (FTLD) are defined by synaptic dysfunction, neuronal loss, neuroinflammation, and impaired proteostasis with misfolded protein aggregates. Despite these contrasting phenotypes, converging epidemiological and molecular data support an inverse relationship between cancer and neurodegenerative disorders, whereby a history of cancer is associated with reduced AD risk, whereas AD is linked to a lower incidence of multiple malignancies. These observations suggest that oncogenesis and neurodegeneration may represent divergent outcomes of shared biological processes dysregulated during aging. This conundrum likely reflects differential regulation of core cellular pathways governing cell survival, stress responses, metabolism, and genomic integrity but could also reflect the differential influence of aging pathways and secreted growth factors. Pro-survival and proliferative signaling pathways commonly activated in cancer, including PI3K-AKT-mTOR signaling, altered p53 function, enhanced DNA damage tolerance, and anabolic metabolism, are often impaired in AD, LBD and FTLD, where neurons exhibit heightened vulnerability to stress, mitochondrial dysfunction, defective autophagy, and activation of pro-apoptotic cascades. Conversely, tumor-suppressive mechanisms that restrain proliferation may protect against malignancy but increase susceptibility to degeneration in post-mitotic neurons. Aging-related processes such as cellular senescence, immune dysregulation, and loss of proteostasis may further exert divergent effects in oncogenesis and neurodegeneration. This review aims to clarify associations between specific cancer types and neurodegenerative disorders, examine shared and opposing selected molecular mechanisms linking specific cancers and neurodegeneration, and contextualize these relationships within broader aging pathways (e.g., cell senescence, proteostasis). By integrating epidemiological, mechanistic, and therapeutic perspectives, we highlight unifying biological principles and translational opportunities at the intersection of cancer, neurodegeneration, and aging.