p53, Aging, and Cancer

Division Of Basic Sciences - Nci

Investigators

Linked publications, trials & patents

Abstract

The CAR-T cells with the delta133p53alpha expression cassette have been examined for anti-tumor activity in an established CD19+ leukemia model. The delta133p53alpha-CAR-T cells showed superior tumor killing activity, compared with the control CAR-T cells, both in a co-culture experiment in vitro and in a mouse injection experiment in vivo. This superior activity was revealed to be associated with inhibition of p53-mediated senescence and apoptosis (while p53-mediated DNA repair was maintained) and metabolic shifts such as increased mitochondrial oxidative phosphorylation and ribosome biogenesis, which both favor T cell stemness, proliferation, and sustained activity. Importantly, we observed the delta133p53alpha-induced functional improvement not only in CAR-T cells derived from normal donors but also in those derived from CLL (chronic lymphocytic leukemia) patients who did not respond to the current CAR-T cell therapy, supporting its clinical therapeutic value. These data warrant further investigation of this novel CAR-T cell strategy toward treatment of current non-responders and patients with currently hard-to-treat solid tumors. To investigate in vivo therapeutic effects of delta133p53alpha, we have generated multiple mouse models that express the human/primate-specific delta133p53alpha isoform. Since modest expression of delta133p53alpha in human p53-knocked-in mice (hupki) did not show any effects on accelerated aging phenotypes in progeria model mice, we generated the safe-harbor transgenic mice in which delta133p53alpha under the control of the synthetic CAG promoter (strong) or the endogenous ROSA26 promoter (intermediate) can be induced via a Cre/ERT2-loxP system. These transgenic mice were confirmed to express delta133p53alpha in various organs upon tamoxifen treatment. They are currently under the aging study to examine physiological aging processes and spontaneous tumor incidence and spectrum, and also being bred with the progeria model mice to examine an effect on accelerated aging phenotypes. These mice are also an essential material for our study on neurodegenerative diseases, through breeding with Alzheimer's disease model mice and applying disease-causing protocols such as cranial irradiation (mimicking radiotherapy-induced late cognitive impairment in cancer survivors) and head trauma (mimicking chronic traumatic encephalopathy in contact sports athletes and military veterans). We have performed high-throughput screening of small molecule libraries, repurposed drugs and natural products to identify drug candidates that can enhance the expression of delta133p53alpha, leading to the two candidates (compound 'A' and compound 'C', whose identities cannot be disclosed here). They were confirmed to increase the delta133p53alpha expression and inhibit senescence-associated secretory phenotype in otherwise senescent astrocytes and progeria-derived fibroblasts. Other human cell types we previously used (e.g., CAR-T cells and endogenous CD8+ T cells) and the delta133p53alpha-humanized mouse models, as mentioned above, are being treated with these compounds to further confirm their activity and therapeutic potential. Since these compounds have already been used in clinical trials for safety and other diseases, they could significantly facilitate the translation of our laboratory findings to the clinic. We have pioneered a new area of p53 research by investigating cancer-associated mutant versions of the p53 isoforms p53beta and delta133p53alpha. While siRNA knockdown of a splicing factor SRSF3 was previously shown to induce p53beta (via alternative splicing switching from full-length p53 to p53beta) and cellular senescence in p53-wild-type normal human cells, we have recently discovered that, also in p53-mutant GBM and lung cancer cells, SRSF3 knockdown induces p53beta (with a cancer-associated mutation) and causes cellular senescence and apoptosis. These data suggest that SRSF3 knockdown can convert the oncogenic mutant full-length p53 to the tumor-suppressive mutant p53beta isoform, prompting us to develop a method of cancer-specific delivery of SRSF3 siRNA that aims at cancer-specific senescence and apoptosis with no or minimal adverse effect on normal cells. We have also revealed that wild-type and mutant delta133p53alpha isoforms are functionally distinct in GBM cells. Mutant delta133p53alpha functions oncogenic through increased cell proliferation and invasion, impaired DNA repair, and activated IL4I1/IDO1/AHR pathway, which can be a therapeutic target in p53-mutant GBM. [Publications] Muys BR, Shrestha RL, Anastasakis DG, Pongor L, Li XL, Grammatikakis I, Polash A, Chari R, Gorospe M, Harris CC, Aladjem MI, Basrai MA, Hafner M, Lal A. Matrin3 regulates mitotic spindle dynamics by controlling alternative splicing of CDC14B. Cell Rep. 42: 112260, 2023.