Puneet Singh, Patsy S H Soon and Stan B Sidhu

Cancer Genetics Unit, Hormones & Cancer Group, Kolling Institute of Medical Research, University of Sydney, Sydney, Australia

RE: Differential expression of microRNA-675, microRNA-139-3p and microRNA-335 in benign and malignant adrenocortical tumours. Schmitz et al. 64:529-535 doi:10.1136/jcp.2010.085621

To the Editor,

We noted with interest the study published by Schmitz and colleagues 1. The authors compared the microRNA (miRNA) expression profile of 4 adrenocortical carcinomas (ACCs) and 3 metastases to 9 adrenocortical adenomas (ACAs) and 4 normal adrenal tissue using Taqman low density array (TLDA). The results from the test cohort were confirmed on a validation cohort of 11 ACAs, 4 ACCs and 1 lung metastasis. Of 667 miRNAs analysed, the total number of differentially expressed miRNAs in ACCs as compared to ACAs was 248 (159 up-regulated and 89 down- regulated). This number is very high as compared to three previous studies, where differential expression of 14, 23 and 23 miRNAs, respectively, was found in ACCs compared to ACAs 2-4. Down-regulation of three of the differentially expressed miRNAs, miR-675, miR-139-3p and miR- 335, was confirmed using quantitative RT-PCR. In the validation cohort, however, only miR-139-3p was found to be down-regulated in ACCs as compared to ACAs, whereas, the other two miRNAs, miR-675 and miR-335, were up-regulated. miR-335 has been reported to be down-regulated in ACCs as compared to ACAs in two other studies.2,5 The lack of consistency in the results from the test cohort and the validation cohort in the present study need to be resolved. This might be done by further confirming the expression of these miRNAs in a larger sample size.

1. Schmitz KJ, Helwig J, Bertram S, et al. Differential expression of microRNA-675, microRNA-139-3p and microRNA-335 in benign and malignant adrenocortical tumours. J Clin Pathol 2011. 2. Soon PS, Tacon LJ, Gill AJ, et al. miR-195 and miR-483-5p Identified as Predictors of Poor Prognosis in Adrenocortical Cancer. Clin Cancer Res 2009;15(24):7684-7692. 3. Tombol Z, Szabo PM, Molnar V, et al. Integrative molecular bioinformatics study of human adrenocortical tumors: microRNA, tissue- specific target prediction, and pathway analysis. Endocr Relat Cancer 2009;16(3):895-906. 4. Patterson EE, Holloway AK, Weng J, Fojo T, Kebebew E. MicroRNA profiling of adrenocortical tumors reveals miR-483 as a marker of malignancy. Cancer 2011;117(8):1630-9. 5. Cherradi, N., Chabre, O., Feige, J.J., 2011. Role of miRNA in ACC [abstract]. Session: Molecular Pathogenesis of ACC-new insights from array studies. International Adrenal Cancer Symposium; Feb 18-19, 2011; Wurzburg, Germany.

Conflict of Interest:

None declared