Virtual mutagenesis of isocitrate dehydrogenase 1 involved in glioblastoma multiforme

Background Site A132Arg mutations potentially impair the affinity of isocitrate dehydrogenase 1 （IDH1） for its substrate isocitrate （ICT）, consequently reducing the production of a-ketoglutarate and leading to tumor growth through the induction of the hypoxia-inducible factor-1 （HIF-1） pathway. However, given that the roles of other active sites in IDH1 substrate binding remain unclear, we aimed to investigate IDH1 mutation pattern and its influence on enzyme function. Methods Fifteen IDH1 catalytic active site candidates were selected for in silico mutagenesis and protein homology modeling. Binding free energy of the IDH1/ICT complexes with single-site mutations was compared with that of the wild type. The affinity of 10 IDH1 catalytic active sites for the ICT substrate was further calculated. Results The IDH1 active site included seven residues from chain A （A77Thr, A94Ser, A100Arg, A132Arg, A109Arg, A275Asp, and A279Asp） and three residues from chain B （B214Thr, B212Lys, and B252Asp） that constituted the substrate ICT-binding site. These residues were located within 0.5 nm of ICT, indicating a potential interaction with the substrate. IDH1 changes of binding free energy （AE） suggested that the A132Arg residue from chain A contributes three hydrogen bonds to the ICT a-carboxyl and 13-carboxyl groups, while the other nine residues involved in ICT binding form only one or two hydrogen bonds. Amino acid substitutes at A132Arg, A109Arg, and B212Lys sites, had the greatest effect on enzyme affinity for its substrate. Conclusions Mutations at sites A132Arg, A109Arg, and B212Lys reduced IDH1 affinity for ICT, indicating these active sites may play a central role in substrate binding. Mutations at sites A77Thr, A94Ser, and A275Asp increased the affinity of IDH1 for ICT, which may enhance IDN1 catalytic activity. Mutant IDH1 proteins with higher catalytic activity than the wild-tvDe IDH1 could potentially be used as a novel qene therapy for qlioblastoma multiforme.

Paradigm shift of chemotherapy and systemic treatment for biliary tract cancer

Biliary tract cancers(BTC)are frequently identified at late stages and have a poor prognosis due to limited systemic treatment regimens.For more than a decade,the combination of gemcitabine and cis-platin has served as the first-line standard treatment.There are few choices for second-line chemo-therapy.Targeted treatment with fibroblast growth factor receptor 2 inhibitors,neurotrophic tyrosine receptor kinase inhibitors,and isocitrate dehydrogenase 1 inhibitors has had important results.Immune checkpoint inhibitors(ICI)such as pembrolizumab are only used in first-line treatment for microsatellite instability high patients.The TOPAZ-1 trial's outcome is encouraging,and there are several trials underway that might soon put targeted treatment and ICI combos into first-line options.Newer targets and agents for existing goals are being studied,which may represent a paradigm shift in BTC management.Due to a scarcity of targetable mutations and the higher toxicity profile of the current medications,the new category of drugs may occupy a significant role in BTC therapies.

A potential role of karyopherin a2 in the impaired maturation of dendritic cells observed in glioblastoma patients

Aim:Patients with glioblastomas demonstrate well‑documented immunological impairments including decreased numbers of mature dendritic cells(DCs).Recent data identified karyopherin a2(KPNA2),a nucleocytoplasmic shuttling receptor,as diagnostic and prognostic biomarker for gliomas.The aim of this ongoing study is to correlate parameters of immunity and nucleocytoplasmic transport in glioblastoma patients.Methods:We preoperatively collected serum from 17 patients with glioblastomas and determined DC subsets(HLA DR+Lin-,CD34-,CD45+,CD123+,CD11+were analyzed)using a 6‑color flow cytometry panel.Expression levels of KPNA2 and nuclear accumulation of p53 were evaluated semi‑quantitatively by immunohistochemistry.O6‑methylguanine DNA methyltransferase(MGMT)and isocitrate dehydrogenase‑1(IDH‑1)status were assessed by pyrosequencing and immunohistochemistry,respectively.Results:Median expression levels for both KPNA2 and p53 were 5-10%.IDH‑1‑R132H mutation and MGMT promoter hypermethylation was detected in 3/16 and 1/9 patients,respectively.Mean counts of total mature DCs,myeloid DCs and plasmacytoid DCs were 9.6,2.1,3.4 cells/μL.A preliminary analysis suggests an association between low KPNA2 nuclear expression and increased numbers of mature DCs.However,this correlation did not reach statistical significance so far(P=0.077).Conclusion:Our preliminary data may indicate a role of KPNA2 in the impaired maturation of DCs observed in glioblastoma patients.