Microarray Analysis in Cushing's Disease Reveals Differential Gene Expression Between Invasive and Non-Invasive Pituitary Corticotropinomas

Presentation Number: LBF-080
Date of Presentation: March 6th, 2015

Leonardo Tadeu Araújo1, Ericka Barbosa Trarbach2, Marcio Carlos Machado3, Marcello D Bronstein4, Antonio M Lerario5 and Maria Candida B V Fragoso*3
1Hospital das Clínicas da Faculdade de Medicina da USP, São Paulo, Brazil, 2Faculdade de Medicina da Universidade de Sao Paulo, Sao Paulo, Brazil, 3Hospital das Clinicas da Faculdade de Medicina da Universidade de Sao Paulo, Sao Paulo, Brazil, 4University of São Paulo Medical School, São Paulo, Brazil, 5Hospital das Clínicas, Faculdade de Medicina da Universidade de São Paulo, São Paulo, Brazil


Background: Corticotropinomas (ACTH-omas) are monoclonal tumors and represent around 10% of diagnosed intracranial tumors. Although considered benign, their biological behaviour is quite variable, ranging from indolent with an extremely slow growing potential, to recurrent, aggressive, and exceptionally malignant tumors, accounting 0.1-0.2% of all pituitary tumors. In some of these invasive adenomas, an effective surgical treatment is very difficult and neither remission nor recurrence are remarkable. Early prediction of invasiveness could be helpful for patients management, however, despite of the extensive tissue-based study on molecular markers for invasiveness and recurrence, it still remains challenging.

Objective: To determine the genome-wide transcriptional status of non-invasive versus invasive corticotrophinomas tumors in order to identify new potential marker for aggressiveness.

Methods: We evaluated mRNA extracted from frozen samples of corticotrophinomas: 4 microadenomas (mean tumor size, 7.5±1.29 mm, Grade I according to Hardy Classification); 5 macroadenomas (mean tumor size, 13.4±3.65 mm, Grade II according to Hardy Classification) and 3 invasive macroademonas (mean tumor size, 27.7±11.2 mm, Grade III and IV according to Hardy Classification). Imunohistochemistry was positive for ACTH stain for all tumor samples. Patients were female (mean age at diagnosis, 39.4 years; range, 14-70). All mRNA was processed on Affymetrix Exon 1.0 ST microarrays protocols and array data analysis was performed using pre-defined Exon expression workflow in Partek® Genomics Suite™ software 6.4. The Robust Multiarray Analysis (RMA) algorithm was used for global normalization and probe set summarization. Differentially expressed genes were determined using Student’s t test and DAVID Functional Gene Classification Tool was used for pathway analysis.

Results and Conclusion: We identified 236 genes that were differentially expressed between non-invasive and invasive corticotrophinomas. Of these, 111 were over-expressed and 120 were under-expressed in the invasive group compared to the noninvasive group. Hierarchical clustering demonstrated a strong tendency to categorize samples in two main classes according to their invasiveness, and the heat map clearly displays a different group of over- and under-expressed genes between them. DAVID pathway analysis of over-expressed gene showed enrichment of categories involved in cell proliferation and adhesion functions, response to hormonal stimulus and apoptosis. When samples were categorized only as macro or microadenomas, no statistical difference was observed.  In conclusion, our findings suggested a distinct transcriptional signature in invasive versus non-invasive corticotrophinomas. Ongoing bioinformatics analysis will possibly reveal candidate genes linked to aggressive behavior on ACTH-oma.


Disclosure: MDB: Advisory Group Member, Ipsen, Advisory Group Member, Novartis Pharmaceuticals, Advisory Group Member, Pfizer, Inc., Advisory Group Member, Chiasma, Speaker, Ipsen, Speaker, Novartis Pharmaceuticals, Principal Investigator, Ipsen, Principal Investigator, Novartis Pharmaceuticals. Nothing to Disclose: LTA, EBT, MCM, AML, MCBVF