American Association of Endocrine Surgeons- Annual Meeting Abstract Papers

DIFFERENTIAL RNA EXPRESSION PROFILE BY cDNA MICROARRAY OF SPORADIC ADRENOCORTICAL TUMORS ALLOWS IDENTIFICATION OF THE MALIGNANT PHENOTYPE.
Velázquez D , Laurell C, Geli J, Kjellman M, Höög A, Hamberger B,, Nilsson P and Bäckdahl M.
Karolinska University Hospital, Stockholm, Sweden.

Background: To investigate with a human cDNA microarray the differences in transcriptional profiles between benign and malignant adrenocortical tumors in order to discover molecular markers and genes involved in malignant transformation.
Methods: We included 13 patients with adrenocortical cancers (ACC) and 13 with adrenocortical adenomas (ACA) who were operated at our Institution. Histopathology was reviewed in all cases and clinical follow up was at least 1 year. Hybridizations were performed in duplicates against human reference RNA on a microarray with 29 800 human cDNA clones representing 16 273 unique UniGene clusters. Expression levels were analyzed using the Aroma, LIMMA, Cluster and PAM statistical packages. Clustering and Gene Ontology analysis were additionally performed in MeV. Gene expression profiles were compared with previous CGH and LOH studies in the same patients.
Results: Median size was 2.75 cm in ACA and 11 cm in ACC. Symptomatic hormonal production was present in 39% of ACA. 8/13 patients died from ACC. All ACC showed chromosomal losses and/or gains in our previous CGH study. Transcriptional profiles were homogeneous among ACA, while ACC were quite heterogeneous and different from ACA. Hierarchical clustering and self organizing maps could separate ACC and ACA into separate clusters using the entire gene set. A minimal subset of gene expression profiles for classification was selected using nearest centroid classification with the PAM algorithm. The most significant differentially expressed genes were obtained by an empirical bayesian statistical test.
Conclusions: About 30 genes were upregulated in ACC by at least a 10 fold differential expression (M>3,1, p<0.001) including the insulin-like growth factor 2 (IGF2), H3 histone and the homeobox D9 (HOXD9). Other 13 genes were downregulated in ACC by at least 10 fold when compared to ACA (M>-3, p<0.001) including aldehyde oxidase 1 (AOX1), cytochrome b reductase (CYBR) and H19. These genes could play a significant role in the malignant transformation of adrenocortical tumors.