P301L tau mutation leads to alterations of cell cycle, DNA damage response and apoptosis: Evidence for a role of tau in cancer.

Tau is a microtubule-associated protein, coded by the MAPT gene, which regulates microtubule (MT) polymerization and dynamics. Due to its key role in neurons, it is a major player in neurodegenerative diseases known as "tauopathies". Since tau has emerged as a multitasking protein with a role in genome stability, it may act both in neurodegeneration and cancer. After demonstrating that tau can be considered as a risk factor for cancer, here we explored the mechanisms linking mutated tau to dysregulation of cancer-relevant processes, by employing lymphoblastoid cell lines (LCL) from patients affected by genetic tauopathy carrying the MAPT P301L mutation and healthy controls (wild-type, wt). In mutated LCL, we found reduced sensitivity to MT perturbation, along with decreased G2/M accumulation and cyclin B1 levels. Furthermore, mutated LCL displayed lower levels of phospho-Chk1 and phospho-Chk2 following hydrogen peroxide-induced oxidative stress, indicating a poorly effective DNA damage checkpoint, as well as reduced basal levels of p53. Such cells also exhibited lower levels of Bax and cleaved caspase-3, and increased levels of Cdc25A, upon oxidative stress, accounting for diminished apoptosis. Overall, these findings point to tau as a key player in biological pathways relevant for cancer, as evidenced by the differential response of mutated and wt cells to MT and DNA perturbation. The modulation of p53 is intriguing given its function as guardian of the genome.