Chronic myelogenous leukemia (CML) is characterized by the Philadelphia chromosome resulting from the translocation t(9-22) producing the chimeric 190 and 210 kDa BCR ± ABL fusion proteins. Evolution of the CML to the more agressive acute myelogenous leukemia (AML) is accompanied by increased cellular proliferation and genomic instability at the cytogenetic level. We hypothezised that genomic instability at the nucleotide level and spontaneous error in DNA replication may also contribute to the evolution of CML to AML. Murine Ba/F3 cell line was transfected with the p190 and p210-encoding BCR ± ABL oncogenes, and spontaneous mutation frequency at the Na-K-ATPase and the hypoxanthine guanine phosphoribosyl transferase (HPRT) loci were measured. A signi®cant 3 ± 5-fold increase in mutation frequency for the transfected cells relative to the untransfected control cells was found. Furthermore, we observed that BCR ± ABL transfection induced an overexpression of DNA polymerase b, the most inaccurate of the mammalian DNA polymerases, as well as an increase in its activity, suggesting that inaccuracy of DNA replication may account for the observed mutator phenotype. These data suggest that the Philadelphia abnormality confers a mutator phenotype and may have implications for the potential role of DNA polymerase b in this process.

No abstract

We aim to establish that accelerated aging and premature cellular senescence seen in individuals with Down syndrome is related to reduced DNA polymeraseβ. We report here that primary fibroblasts from Down syndrome individuals exhibit greater SA-β-gal staining (fourfold increase, P < 0.001), increased p16 transcript abundance (threefold increase, P < 0.01), and reduced HMGB1 nuclear localization (1.5-fold lower, P < 0.01). We also find that DNA polymerase β expression is significantly reduced in Down syndrome primary fibroblasts (53% decline, P < 0.01). To evaluate whether DNA polymerase β might be causative in senescence induction, we evaluated the impact of murine DNA polymerase β nullizygosity on senescence. We find that unexposed DNA polymerase β -null primary fibroblasts exhibit a robust increase in the number of senescent cells compared to wild-type (11-fold, P < 0.001), demonstrating that loss DNA polymerase β is sufficient to induce senescence. We also see an additional increase in response to hydroxyurea (threefold greater than WT-HU, P < 0.05). These data demonstrate that loss of DNA polymerase β is sufficient to induce senescence. Additionally, we report a significant induction in spontaneous DNA double strand breaks in DNA polymerase β null MEFs (fivefold increase from wild-type, P < 0.0001). Our findings strongly suggest that DNA polymerase β is causative in senescence induction, reasonably pointing to DNA polymerase β as a likely factor driving the premature senescence in Down syndrome. Environ. Mol. Mutagen. 59:603-612, 2018. © 2018 Wiley Periodicals, Inc.

Background Overcoming drug resistance is critical for increasing the survival rate of prostate cancer (PCa). Docetaxel is the first cytotoxic chemotherapeutical approved for treatment of PCa. However, 99% of PCa patients will develop resistance to docetaxel within 3 years. Understanding how resistance arises is important to increasing PCa survival. Methods In this study, we modeled docetaxel resistance using two PCa cell lines: DU145 and PC3. Using the Passing Attributes between Networks for Data Assimilation (PANDA) method to model transcription factor (TF) activity networks in both sensitive and resistant variants of the two cell lines. We identified edges and nodes shared by both PCa cell lines that composed a shared TF network that modeled changes which occur during acquisition of docetaxel resistance in PCa. We subjected the shared TF network to connectivity map analysis (CMAP) to identify potential drugs that could disrupt the resistant networks. We validated the candidate drug in combination with docetaxel to treat docetaxel-resistant PCa in both in vitro and in vivo models. Results In the final shared TF network, 10 TF nodes were identified as the main nodes for the development of docetaxel resistance. CMAP analysis of the shared TF network identified trichostatin A (TSA) as a candidate adjuvant to reverse docetaxel resistance. In cell lines, the addition of TSA to docetaxel enhanced cytotoxicity of docetaxel resistant PCa cells with an associated reduction of the IC50 of docetaxel on the resistant cells. In the PCa mouse model, combination of TSA and docetaxel reduced tumor growth and final weight greater than either drug alone or vehicle. Conclusions We identified a shared TF activity network that drives docetaxel resistance in PCa. We also demonstrated a novel combination therapy to overcome this resistance. This study highlights the usage of novel application of single cell RNA-sequencing and subsequent network analyses that can reveal novel insights which have the potential to improve clinical outcomes.