Glucose transporter GLUT1 expression is an stage-independent predictor of clinical outcome in adrenocortical carcinoma

Owing to the rarity of adrenocortical carcinoma (ACC) no prognostic markers have been established beyond stage and resection status. Accelerated glycolysis is a characteristic feature of cancer cells and in a variety of tumour entities key factors in glucose metabolism like glucose transporter 1 and 3 (GLUT1 and -3), transketolase like-1 enzyme (TKTL1) and pyruvate kinase type M2 (M2-PK) are overexpressed and of prognostic value. Therefore, we investigated the role of these factors in ACC. Immunohistochemical analysis was performed on tissue microarrays of paraffin-embedded tissue samples from 167 ACCs, 15 adrenal adenomas and 4 normal adrenal glands. Expression was correlated with baseline parameters and clinical outcome GLUT1 and -3 were expressed in 33 and 17% of ACC samples respectively, but in none of the benign tumours or normal adrenals glands. By contrast, TKTL1 and M2-PK were detectable in all benign tissues and the vast majority of ACCs. GLUT1 expression was strongly associated with prognosis in univariate and multivariate analysis (P<0.01), whereas GLUT3, TKTL1 and M2-PK did not correlate with clinical outcome. Patients with strong GLUT1 staining showed a considerably higher overall mortality (hazard ratio (HR) 6.34 (95% confidence interval 3.10-12.90) compared with patients with no GLUT1 staining When analysing patients in their early stages and advanced disease separately, similar results were obtained HR for survival was 5.31 (1.80-15.62) in patients with metatastic ACC and in patients after radical resection the HR for disease-free survival was 6.10 (2.16-16.94). In conclusion, GLUT1 is a highly promising stage-independent, prognostic marker in ACC.