WT1 in astrocytomas: Comprehensive evaluation of immunohistochemical expression and its potential utility in different histological grades

Sensitivity Assessment of Wilms Tumor Gene (WT1) Expression in Glioblastoma using qPCR and Immunohistochemistry and its Association with IDH1 Mutation and Recurrence Interval

Purpose

Wilms tumor 1 (WT1) gene has recently shown a role in gliomagenesis, making it a potential immunotherapy target in glioblastomas. We aimed to investigate the most sensitive method to detect WT1 expression in glioblastoma and explore the relationship between WT1 expression, IDH1 mutation and recurrence interval.

Patients and Methods

Clinical data were collected from 44 patients with glioblastomas, treated with adjuvant therapies. WT1 expression was assessed in all cases using immunohistochemistry (IHC), while its gene expression was assessed in 13 clustered samples using polymerase chain reaction (qPCR). IDH1 mutation was assessed using IHC. The sensitivity between IHC and RT-qPCR was examined. Kaplan–Meier curves were used to compare the recurrence-free interval (RFI) between IDH1 and WT1 expression groups.

Results

IDH1^wildtype was found in 26 cases (59.1%) and the remaining 18 cases (40.9%) were IDH1^mutant. Through IHC, WT1 was overexpressed in 32 cases (72.7%), partially expressed in 9 cases (20.5%) and not expressed in only 3 cases. For the 13 cases tested by qPCR, 6 cases showed WT1 upregulation and 7 cases showed WT1 downregulation. There was no significant difference in WT1 expression among cases with different RNA concentrations regardless the testing method (p-value >0.05). However, the difference between IHC and qPCR was significant. IDH1^mutant cases with WT1 overexpression showed significant difference in RFI (p-value =0.048).

Conclusion

Parallel testing for WT1 expression using IHC and qPCR is not reliable. However, IHC provides more accurate results. Moreover, IDH1^mutant glioblastomas with WT1 overexpression are associated with late RFI particularly if temozolomide with additional chemotherapies are used.

WT1 Clone 6F-H2 Cytoplasmic Expression Differentiates Astrocytic Tumors from Astrogliosis and Associates with Tumor Grade, Histopathology, IDH1 Status, Apoptotic and Proliferative Indices: A Tissue Microarray Study

OBJECTIVES

This tissue microarray (TMA) immunohistochemical (IHC) study elucidates the role of Wilms' tumor 1 protein (WT1) in diagnosis and prognostication of astrocytic tumors.

METHODS

IHC was applied to 75 astrocytic lesions (18 astrogliosis and 57 astrocytic tumors) using antibodies directed against WT1 clone 6F-H2, isocitrate dehydrogenase 1(IDH1), Bcl2 and Ki67. WT1 IHC staining was evaluated and scored blindly by 2 pathologists. Bcl2 and Ki67 scores and labelling indices were assessed and IDH1 status determined. Statistical analysis was performed using the appropriate methodology.

RESULTS

WT1 cytoplasmic expression was detected in 89.5% of astrocytic tumors but not in astrogliosis. Positive WT1 differentiated astrocytic tumors (92.6% accuracy) and grade II diffuse astrocytomas (93.5% accuracy) from astrogliosis with high sensitivity, specificity and positive predictive values (p<0.001). Increased WT1 score significantly associated higher Bcl2 and Ki67 labelling indices, increasing WHO tumor grade and tumor's histopathologic type (p<0.05) showing staining pattern variability by tumor entity and cell type. Glioblastomas, gliosarcomas and subependymal giant cell astrocytomas were the most frequently WT1 expressing tumors with frequent +3 WT1 score. About 21.4% of pilocytic astrocytomas had +3WT1 score in association with increased Bcl2 and Ki67 indices. Low WT1 scores in grade II and III diffuse astrocytomas were linked to the high frequency of IDH1 positivity, and were associated with low Bcl2 and Ki67 labelling indices. In glioblastomas, WT1 significantly associated poor prognostic variables: older age, negative-IDH1 status, high Bcl2 and Ki67 labelling indices (p=0.04, <0.001, =0.001 and.