National Institutes of Health and the St. Baldrick's Foundation.

Methotrexate is a dihydrofolate reductase inhibitor widely employed in curative treatment for children with acute lymphoblastic leukemia (ALL). However, methotrexate administration is also associated with persistent cognitive deficits among long-term childhood cancer survivors. Animal models of methotrexate-induced cognitive deficits have primarily utilized adult animals. The purpose of present study is to investigate the neurotoxicity of methotrexate in juvenile rats and its relevant mechanisms. The doses and schedule of systemic and intrathecal methotrexate, given from post-natal age 3-7 weeks, were chosen to model the effects of repeated methotrexate dosing on the developing brains of young children with ALL. This methotrexate regimen had no visible acute toxicity and no effect on growth. At 15 weeks of age (8 weeks after the last methotrexate dose) both spatial pattern memory and visual recognition memory were impaired. In addition, methotrexate-treated animals demonstrated impaired performance in the set-shifting assay, indicating decreased cognitive flexibility. Histopathological analysis demonstrated decreased cell proliferation in methotrexate-treated animals compared to controls, as well as changes in length and thickness of the corpus callosum. Moreover, methotrexate suppressed microglia activation and RANTES production. In conclusion, our study demonstrated that a clinically relevant regimen of systemic and intrathecal methotrexate induces persistent deficits in spatial pattern memory, visual recognition memory and executive function, lasting at least 8 weeks after the last injection. The mechanisms behind methotrexate-induced deficits are likely multifactorial and may relate to suppression of neurogenesis, alterations in neuroinflammation and microglial activation, and structural changes in the corpus callosum.

INI1/SMARCB1 binds to HIV-1 integrase (IN) through its Rpt1 domain and exhibits multifaceted role in HIV-1 replication. Determining the NMR structure of INI1-Rpt1 and modeling its interaction with the IN-C-terminal domain (IN-CTD) reveal that INI1-Rpt1/IN-CTD interface residues overlap with those required for IN/RNA interaction. Mutational analyses validate our model and indicate that the same IN residues are involved in both INI1 and RNA binding. INI1-Rpt1 and TAR RNA compete with each other for IN binding with similar IC50 values. INI1-interaction-defective IN mutant viruses are impaired for incorporation of INI1 into virions and for particle morphogenesis. Computational modeling of IN-CTD/TAR complex indicates that the TAR interface phosphates overlap with negatively charged surface residues of INI1-Rpt1 in three-dimensional space, suggesting that INI1-Rpt1 domain structurally mimics TAR. This possible mimicry between INI1-Rpt1 and TAR explains the mechanism by which INI1/SMARCB1 influences HIV-1 late events and suggests additional strategies to inhibit HIV-1 replication.

Background/objectives Although thromboembolism (TE) is a serious complication in patients with acute lymphoblastic leukemia (ALL), thromboprophylaxis is not commonly used due to the inherent bleeding risk in this population. Identifying prothrombotic risk factors will help target thromboprophylaxis to those at highest thrombotic risk. We aimed to define predictors and the impact of TE on ALL outcome in children (1‐18 years) treated on the Dana‐Farber Cancer Institute ALL 05‐001 trial. Methods Clinical and laboratory data including TE events were prospectively collected. PCR‐based allelic discrimination assay identified single‐nucleotide polymorphisms (SNP) for prothrombin G20210A (rs1799963) and Factor V G1691A (rs6025). Univariate and multivariable competing risk regression models evaluated the effect of diagnostic clinical (age, sex, body mass index, ALL‐immunophenotype, risk group) and laboratory variables (presenting leukocyte count, blood group, SNPs) on the cumulative incidence of TE. Cox regression modeling explored the impact of TE on survival. Results Of 794 patients [median age 4.97 (range, 1.04‐17.96) years; males 441], 100 developed TE; 25‐month cumulative incidence 13.0% (95% CI, 10.7%‐15.5%). Univariate analyses identified older age (≥10 years), presenting leucocyte count, T‐ALL, high‐risk ALL, and non‐O blood group as risk factors. Age and non‐O blood group were independent predictors of TE on multivariable regression; the blood group impact being most evident in patients 1‐5 years of age (P = 0.011). TE did not impact survival. Induction TE was independently associated with induction failure (OR 6.45; 95% CI, 1.64‐25.47; P = 0.008). Conclusion We recommend further evaluation of these risk factors and consideration of thromboprophylaxis for patients ≥10 years (especially those ≥15 years) when receiving asparaginase.

These results suggest a positive family history of MPNST represents a risk factor for the development and early onset of MPNST in individuals with NF-1.