Project description:Background: TP53, the most frequently mutated gene in human cancers, orchestrates a complex transcriptional program crucial for cancer prevention. While certain TP53-dependent genes have been extensively studied, others, like the recently identified RNF144B, remained poorly understood. This E3 ubiquitin ligase has shown potent tumor suppressor activity in murine Eμ Myc-driven lymphoma, emphasizing its significance in the TP53 network. However, little is known about its targets and its role in cancer development, requiring further exploration. In this work, we investigate RNF144B's impact on tumor suppression beyond the hematopoietic compartment in human cancers. Methods: Employing TP53 wild-type cells, we generated models lacking RNF144B in both non-transformed and cancerous cells of human and mouse origin. By using proteomics, transcriptomics, and functional analysis, we assessed RNF144B's impact in cellular proliferation and transformation. Through In vitro and in vivo experiments, we explored proliferation, transformation potential, DNA repair, cell cycle control, mitotic progression, and treatment resistance. Findings were contrasted with clinical datasets and bioinformatics analysis. Results: Our research underscores RNF144B's pivotal role as a tumor suppressor, particularly in lung adenocarcinoma. In both human and mouse oncogene-expressing cells, RNF144B deficiency heightened cellular proliferation and transformation. Proteomic and transcriptomic analysis revealed RNF144B's novel function in mediating protein degradation associated with cell cycle progression, DNA damage response and genomic stability. RNF144B deficiency induced chromosomal instability, mitotic defects, and correlated with elevated aneuploidy and worse prognosis in human tumors. Furthermore, RNF144B-deficient lung adenocarcinoma cells exhibited resistance to cell cycle inhibitors that induce chromosomal instability. Conclusions: PRJNA1092607Supported by clinical data, our study suggests that RNF144B plays a pivotal role in maintaining genomic stability during tumor suppression.

Project description:Acute Myeloid Leukemia (AML) which occurs after an antecedent myeloproliferative neoplasm (MPN) has a dismal clinical prognosis and is not curative outside of the rare subset of patients who undergo successful allogeneic stem cell transplantation. As such, there is a pressing need for new mechanistic insights into how MPNs transform into AML and to use these insights to credential novel therapeutic approaches. The most common somatic mutational event which occurs in transformation from MPN to AML is mutation in TP53. However, the impact of TP53 allelic state on the ability to potentiate leukemic transformation, as well as the pathways involved in this process, have largely remained unresolved. Here we report the development of genetically accurate models of Jak2/Tp53 mutant MPN which undergoes progressive leukemic transformation with chromosomal instability similar to that observed in the clinical context. These models result in a fulminant erythroleukemia phenotype. We identify that leukemic transformation requires homozygous inactivation of TP53, and does not occur with heterozygous loss of Tp53. We further identify that the megakaryocyte erythroid progenitor (MEP) population is expanded prior to and after leukemic transformation, is characterized by progressive genomic instability (compared to other stem/progenitor compartments), and is capable of propagating the disease in vivo. Thus, the leukemia-initiating population is contained in the MEP compartment. Using gene-expression profiling we demonstrate that the BMP2/SMAD pathway (which is involved in self-renewal and DNA damage repair) is aberrantly activated in the leukemic phase of the disease. Importantly, attenuation of Bmp2 results in decreased self-renewal of leukemic cells in vitro and increased survival of leukemic mice in vivo, thus credentialing a biologic role for this pathway in leukemic transformation. Finally, given the loss of Tp53 function and associated disruption of DNA repair pathways, we hypothesized and subsequently identified that leukemic transformation is characterized by increased DNA damage. Using a synthetic-lethality strategy of targeting remaining DNA-repair pathways, using small-molecule inhibitors, in order to provoke biologically intolerable DNA damage and mitotic catastrophe, we demonstrate that Jak2/Tp53 mutant is highly sensitive to combined inhibition of WEE1 and PARP. This combination results in prolonged survival of mice and attenuates the leukemic phenotype. Collectively, these observations yield new mechanistic insights into the process of leukemic transformation resulting from TP53 alterations, and offer new, clinically-translatable, therapeutic options.

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The TP53-activated E3 ligase RNF144B is a tumour suppressor that prevents genomic instability

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