Iansavitchous, J. | Search bioRxiv

bioRxiv2024

T505A variant of ETV5 promotes proliferation of precursor B cells in a mouse model of acute lymphoblastic leukemia

Precursor B cell acute lymphoblastic leukemia (pre-B-ALL) arises as a result of precursor B cells acquiring driver mutations that lead to arrested differentiation and increased proliferation. Identification of driver mutations and understanding their biological function is critical to understanding pre-B-ALL development and advancing disease treatment. Using a mouse model of pre-B-ALL driven by deletion of genes encoding the related E26-transformation-specific (ETS) transcription factors PU.1 and Spi-B, we performed whole exome sequencing to identify secondary driver mutations. We identified recurrent variants in E26 transformation-specific transcription variant 5 (ETV5) resulting in R392P, V444I, and T505A amino acid changes. We found that the R392P and V444I variants altered the ability of ETV5 to bind to DNA using electrophoretic mobility shift assay. R392P and V444I variants did not activate a Dual-Specificity-Phosphatase 6 (DUSP6) reporter. In contrast, T505A ETV5 could interact with DNA and activate the DUSP6 promoter. To determine biological function, we forced expression of wild type, R392P, V444I, or T505A ETV5 in an interleukin-7-dependent pre-B cell line. Proliferation and apoptosis assays showed that T505A ETV5 conferred a proliferative advantage to pre-B cells. RNA sequencing showed that expression of ETV5 variants significantly altered gene expression in cultured cells. Through gene set enrichment analysis, T505A was suggested to downregulate the p53 pathway and the anti-proliferative protein, B cell translocation gene 2 (encoded by Btg2). In summary, these data suggest that ETV5 mutations play a role in pre-B-ALL by affecting proliferation and cell survival.

immunology↗

bioRxiv2023

N-Acetylcysteine alters disease progression and increases Janus Kinase mutation frequency in a mouse model of precursor B cell acute lymphoblastic leukemia

B cell acute lymphoblastic leukemia (B-ALL) is the most prevalent type of cancer in young children and is associated with high levels of reactive oxygen species (ROS). The antioxidant N-acetylcysteine (NAC) was tested for its ability to alter disease progression in a mouse model of B-ALL. Mb1-Cre{Delta}PB mice have deletions in genes encoding PU.1 and Spi-B in B cells and develop B-ALL at 100% incidence. Treatment of Mb1-Cre{Delta}PB mice with NAC in drinking water significantly reduced the frequency of CD19+ pre-B ALL cells infiltrating the thymus at 11 weeks of age. However, treatment with NAC did not reduce leukemia progression or increase survival by median 16 weeks of age. NAC significantly altered gene expression in leukemias in treated mice. Mice treated with NAC had increased frequencies of activating mutations in genes encoding Janus Kinases 1 and 3. In particular, frequencies of Jak3 R653H mutations were increased in mice treated with NAC compared to control drinking water. NAC opposed oxidization of PTEN protein ROS in cultured leukemia cells. These results show that NAC alters leukemia progression in this mouse model, ultimately selecting for leukemias with high Jak3 R653H mutation frequencies.

cancer biology↗