Plek2 as a novel downstream effector of p53: Targeting Plek2 ameliorates disease progression in p53-deficient myeloid malignancies Free

TP53 mutations are common in myeloid malignancies and are associated with poor prognosis and therapeutic resistance. However, the downstream mediators of p53 loss remain incompletely understood. Pleckstrin-2 (PLEK2), a cytoskeletal adaptor protein, has previously been identified as a critical downstream effector of the JAK2–STAT5 signaling axis in myeloproliferative neoplasms (MPNs). Plek2 deletion reduces thrombosis and extends survival in Jak2^V617F mice, with minimal impact on normal hematopoiesis. PLEK2 small-molecule inhibitors block the PLEK2–AKT interaction and suppress MPN cell proliferation.

To further explore the regulatory mechanisms of PLEK2, we performed a DNA pulldown–mass spectrometry screen using the PLEK2 promoter and identified p53 as a hit. Direct interaction of p53 with the Plek2 promoterwas confirmed by biotin-labeled DNA pulldown and luciferase reporter assays. Motif analysis and UCSC genome browser identified two p53 binding sites; mutation of these sites reduced p53 binding and promoter activity. ChIP-qPCR showed p53 enrichment at both sites in wild-type mouse spleens but not in p53-KO mice. Overexpression of p53 decreased Plek2 mRNA and protein, whereas p53 loss increased its expression in cell lines and mouse tissues. These results establish Plek2 as a direct transcriptional target negatively regulated by p53.

To investigate the functional significance of this regulation, we generated Plek2/p53 double-knockout (DKO) mice. Compared to p53^KO mice, DKO animals showed partial normalization of peripheral blood counts and significantly prolonged survival, indicating Plek2's role in mediating p53 loss–associated hematologic defects and lethality. We also established several disease models that mimic high-risk and leukemia-phase MPNs with JAK2 mutation and p53 loss. In these models, Plek2 expression progressively increased in megakaryocyte-erythroid progenitors (MEPs) from wild-type, Jak2^V617F, Jak2^V617F-p53^KO, to leukemic-phase Jak2^V617F-p53^KO mice. Jak2^V617F-p53^KO mice developed aggressive phenotypes, including splenomegaly, marrow hypercellularity, extramedullary erythropoiesis, and pulmonary thrombosis, which were markedly reversed by pharmacologic inhibition of Plek2, accompanied by extended survival and improved marrow and thrombotic pathology. Consistent with these studies, we also found elevated PLEK2 expression in induced pluripotent stem cells (iPSCs) derived from TP53-mutated patients and p53^R248Wmutant mice.

Together, we identify PLEK2 as a direct transcriptional target of p53. Genetic or pharmacologic targeting of Plek2 ameliorates hematologic abnormalities and significantly extends survival in p53-deficient mouse models. These findings uncover a novel p53-PLEK2 regulatory axis and provide compelling preclinical evidence supporting PLEK2 as a promising therapeutic target in TP53-mutated myeloid malignancies.