Haishi Zhang

Polymorphisms of LIG4 and XRCC4 Involved in the NHEJ Pathway Interact to Modify Risk of Glioma

Although the role of environmental risk factors in the etiology of gliomas remains to be elucidated, accumulative epidemiological evidence suggests that genetic factors, such as variants in genes involved in DNA repair, may also play an important role. LIG4 and XRCC4 are known to form a complex and are functionally linked in the repair of double‐stranded DNA breaks. To determine whether LIG4 and XRCC4 polymorphisms are associated with susceptibility to glioma and whether there are interactions between LIG4 and XRCC4, we conducted a case–control study of 771 glioma patients and 752 cancer‐free controls, assessed the associations between glioma risk and 20 tagging SNPs, and evaluated their potential gene–gene interactions using the multifactor dimensionality reduction (MDR), interaction dendrogram, and entropy analysis. In the single‐locus analysis, only one variant, the LIG4 SNP2 rs3093739:T>C (P‐permutation=0.009) was significantly associated with risk of developing glioma. Haplotype analysis revealed an association of glioma risk with genetic variants in LIG4 block 1 (global P=0.011), and XRCC4 blocks 2 and 4 (both global P<0.0001). Moreover, the MDR analysis suggested a significant three‐locus interaction model involving LIG4 SNP4 rs1805388:C>T, XRCC4 SNP12 rs7734849:A>T, and SNP15 rs1056503:G>T. Further dendrogram and graph analysis indicated a more‐than‐additive effect among these three loci. These results suggested that these variants may contribute to glioma susceptibility. Hum Mutat 29(3), 381–389, 2008.

XRCC3 haplotypes and risk of gliomas in a Chinese population: A hospital-based case-control study

In mammalian cells, X‐ray repair cross‐complementing group3 (XRCC3) plays an important role in the DNA double‐strand breaks (DSBs) repair by homologous recombination. Genetic polymorphisms in the XRCC3 gene may potentially affect the repair of DSBs and thus confer susceptibility to gliomas. In this study, we used a haplotype‐based approach to investigate whether 4 tagging single nucleotide polymorphisms of the XRCC3 gene are associated with risk of gliomas in 771 glioma patients and 752 cancer‐free controls. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated by the unconditional logistic regression, and haplotype associations were estimated using Haplo.Stat. After adjustment for age and sex, the variant G allele of rs861530 and T allele of rs3212092 were significantly associated with an increased risk of gliomas (AG/GG versus AA: adjusted OR = 1.44, 95% CI = 1.15–1.80, p = 0.001 and CT/TT versus CC: adjusted OR = 1.66, 95% CI = 1.12–2.46, p = 0.013, respectively). Consistent with these results, XRCC3 haplotype “GGCC” containing rs861530 G allele and haplotype “AGTC” containing rs3212092 T allele were also significantly associated with an elevated risk of gliomas compared with the common haplotype “AGCC” (adjusted OR = 1.35, 95% CI = 1.14–1.58, p = 0.000 and adjusted OR = 1.67, 95% CI = 1.11–2.52, p = 0.015, respectively). Our results suggest that common genetic variants in the XRCC3 gene may modulate glioma risk.

Discovery of serum biomarkers in astrocytoma by SELDI-TOF MS and proteinchip technology.

ObjectiveTo discover serum biomarkers in astrocytoma patients for early detection of glioma and evaluation of prognosis.MethodsA total of 140 serum samples were analyzed using the weak cation-exchange (WCX) chips. Among those, 73 were sera from astrocytoma patients, 56 from normal controls, and 11 from other brain tumors. For building a diagnosis model, the samples were randomly split into a training set and a test set with similar distribution of case and control samples. Proteomics profiles were obtained using a PBSII instrument and the data were analyzed with the accompanying software.ResultsSeven serum biomarkers were significantly deregulated in astrocytoma group comparing to the normal control group. Among them, four were up-regulated and three were down-regulated. A decision tree classification method were developed using these seven markers. A sensitivity of 84.6% and a selectivity of 84.6% were achieved to discriminate astrocytoma from normal controls. In addition, a correlation of these markers with the astrocytoma malignancy was observed.ConclusionsProteomics approaches such as SELDI–TOF mass spectrometry could greatly facilitate the discovery of serum biomarkers in astrocytoma. The discovered biomarkers might show great potential for early detection of astrocytoma and evaluation of prognosis for those clinical suspect astrocytoma patients. However, this need warrant further study.

Cationic core–shell nanoparticles with carmustine contained within O6-benzylguanine shell for glioma therapy

The application of carmustine (BCNU) for glioma treatment is limited due to its poor selectivity for tumor and tumor resistance caused by O⁶-methylguanine-DNA-methyl transferase (MGMT). To improve the efficacy of BCNU, we constructed chitosan surface-modified poly (lactide-co-glycolides) nanoparticles (PLGA/CS NPs) for targeting glioma, loading BCNU along with O⁶-benzylguanine (BG), which could directly deplete MGMT. With core-shell structure, PLGA/CS NPs in the diameter around 177 nm showed positive zeta potential. In vitro plasma stability of BCNU in NPs was improved compared with free BCNU. The cellular uptake of NPs increased with surface modification of CS and decreasing particle size. The cytotoxicity of BCNU against glioblastoma cells was enhanced after being encapsulated into NPs; furthermore, with the co-encapsulation of BCNU and BG into NPs, BCNU + BG PLGA/CS NPs showed the strongest inhibiting ability. Compared to free drugs, PLGA/CS NPs could prolong circulation time and enhance accumulation in tumor and brain. Among all treatment groups, F98 glioma-bearing rats treated with BCNU + BG PLGA/CS NPs showed the longest survival time and the smallest tumor size. The studies suggested that the co-encapsulation of BCNU and BG into PLGA/CS NPs could remarkably enhance the efficacy of BCNU, accompanied with greater convenience for therapy.

Serum GFAP autoantibody as an ELISA-detectable glioma marker

Glioma is the most common primary brain tumor, yet the high cost of diagnostic imaging has made early detection of asymptomatic glioma a formidable challenge. Thus, the development of a convenient, sensitive, and cost-effective diagnostic strategy, such as enzyme-linked immunosorbent assay (ELISA) based on glioma-specific and World Health Organization (WHO) grade-specific autoantibody serum markers, is necessary. To this end, a comparative proteomic analysis based on two-dimensional western blotting was carried out with the sera of glioma patients and normal controls. Of the 11 novel glioma-expressed autoantibodies, the autoantibody against glial fibrillary acidic protein (GFAP) showed the highest differential expression. To investigate the potential clinical utility of the GFAP autoantibody as an early diagnostic marker for glioma, an ELISA-based assay was developed and validated with sera from glioma patients with WHO grades II (n = 19), III (n = 17), and IV (n = 24). The GFAP autoantibody level directly correlated with WHO grade and tumor volume. Sera from patients of non-glioma brain tumors, as well as non-brain tumors, showed much lower levels of GFAP autoantibody than those of the glioma patients, indicating that elevated GFAP autoantibody is specific to glioma patients. Analysis of the receiver operating characteristics curve suggested that the new ELISA has good distinguishing power and sensitivity for diagnosing glioma patients. This is the first ELISA assay developed for an autoantibody of a glioma antigen and may prove valuable for the clinical detection of glioma.

TMZ-induced PrPc/par-4 interaction promotes the survival of human glioma cells

Malignant gliomas recur even after extensive surgery and chemo‐radiotherapy. Although a relatively novel chemotherapeutic agent, temozolomide (TMZ), has demonstrated promising activity against gliomas, the effects last only a few months and drug resistance develops thereafter in many cases. It has been acknowledged that glioma cells respond to TMZ treatment by undergoing G2/M arrest, but not apoptosis. Here we demonstrate a phase‐specific chemotherapy resistance due to cellular prion protein (PrPc) in human glioma cells upon TMZ treatment. TMZ‐induced G2/M‐arrested cultures show an upregulation of PrPc expression and are more resistant, whereas G1/S‐phase cells that show decreased levels of PrPc are more sensitive to apoptosis. Furthermore, an investigation into the biological significance of PrPc association with par‐4 provided the first evidence of a relationship between the endogenous levels of PrPc and the resistance of glioma cells to the apoptotic effects of TMZ. Upon TMZ treatment, PrPc exerts its antiapoptotic activity by inhibiting PKA‐mediated par‐4 phosphorylation that are important for par‐4 activation, nuclear entry and initiation of apoptosis. In context with cell cycle‐dependent responses to chemotherapy, the data from this study suggest the possibility of exploiting the PrPc‐dependent pathway to improve the efficacy of TMZ‐based regimen for patients with gliomas.