INI1 immunohistochemical expression in glioblastoma: correlation with MGMT gene promoter methylation status and patient survival

Aims: INI1 expression and its correlation with MGMT gene promoter methylation status and follow-up was investigated in 77 surgically removed glioblastomas then treated with radiotherapy (RT) or AT plus temozolomide (RT+TMZ). Methods: INI1 was determined by immunohistochemistry and MGMT by methylation-specific PCR. Results: INI1 was expressed in 83.1% of cases. The median overall survival (OS) was 13.6 months in INI1 positive tumours and 7.2 months in INI1 negative tumours; 31.3% of patients with INI1 positive tumours were alive compared with 15.4% of patients with INI1 negative tumours. MGMT methylation was detected in 31.2% of cases. OS was significantly different between patients with methylated tumours and unmethylated tumours (p<0.04), and between patients with RT+TMZ and AT alone (p<0.001). Considering both treatment and MGMT, the difference in OS was significant (p<0.002). The difference in OS according to MGMT and INI1 was significant (p<0.04). The longest median OS was recorded among methylated and INI1 positive tumours. Among unmethylated tumours, the median OS was 11.1 months in INI1 positive and 6.5 months in INI1 negative tumours. No patients were alive with unmethylated and INI1 negative tumours. Conclusions: Loss of INI1 immunohistochemical expression in glioblastoma may be indicating an underlying molecular aberration accounting for the more aggressive clinical behaviour.