MGMT promoter methylation is not correlated with integrin expression in malignant gliomas: clarifying recent clinical trial results.

Integrin alpha-v-beta-3 (αvβ3) is important for invasive tumor growth and angiogenesis in glioblastomas (GBM). However, recent clinical trials on inhibition of this integrin led to ambiguous results whether patients with methylated or unmethylated 6O-methylguanine methyltransferase (MGMT) promoter might profit from this kind of therapy. Therefore, we addressed the still unanswered question about a possible correlation between integrin αvβ3 expression and MGMT promoter methylation in GBM. For this purpose, tumor samples from newly diagnosed and untreated GBM patients with methylated (n = 22) or unmethylated (n = 17) MGMT promoter were simultaneously analyzed for integrin αvβ3 expression by an automated immunohistochemical staining platform. Interestingly, subsequent semi-quantitative analysis by a special imaging software did not show any difference in integrin expression between patients with methylated or unmethylated MGMT promoter status. Moreover, further analysis of the integrin subunits via ELISA from histologic sections revealed that there is no difference in integrin subunit expression between these patients. Hence, our results are important for designing future clinical trials with respect to treatment stratification, while it still has to be identified which other molecular factors determine differential responses to targeted anti-integrin αvβ3 treatment.