S. Ammar1, L. Xu1, W. Alobuia1, M. Tyagi1, C. Ghosh1, S. K. Gara2, E. Kebebew1 1Stanford University,General Surgery/Surgery/School Of Medicine,Palo Alto, CA, USA 2National Cancer Institute,Endocrine Oncology Branch,Bethesda, MD, USA
Introduction:
Adrenocortical carcinoma (ACC) is a rare malignancy with a poor prognosis. There are no effective therapeutic agents for unresectable ACC. Unfortunately, most therapeutic targets for ACC have been evaluated in primary ACC but most cancer deaths are due to recurrent/metastatic ACC. A recent study comparing primary ACC with recurrent and metastatic ACC reported marked tumor heterogeneity and greater mutation rate in recurrent/metastatic tumors compared to primary tumors. One gene, WDR66, had a high prevalence of damaging recurrent mutations (present in 28% of samples) in recurrent/metastatic ACC. Therefore, the aim of this study was to characterize the expression and diagnostic/prognostic utility of WDR66 in ACC.
Methods:
We used RT quantitative PCR (qPCR) and immunohistochemistry (IHC) to characterize the expression of WDR66 mRNA and protein in 61 ACC patient tissue samples (45 metastatic ACC, 12 recurrent ACC and 4 primary ACC), 11 benign adrenocortical tumor samples and 28 normal adrenocortical tissue samples. H-scores of IHC staining were calculated for WDR66. In addition, data from 78 ACC were analyzed to evaluate WDR66 gene expression and survival using the cBioportal database.
Results:
WDR66 mRNA level was higher (7-fold) in benign and normal adrenal tissues than that in primary, recurrent, and metastatic ACC (p<0.0001). There was no significant difference in WDR66 mRNA levels between benign and normal adrenal tissues. There was no significant difference in WDR66 mRNA levels in ACC by WDR66 mutation status. IHC staining revealed that WDR66 protein was predominantly located in the cytoplasm with sparse distribution in the nuclei of some cells. However, WDR66 protein staining pattern was predominantly distributed in the in nuclei in ACC tissue samples. WDR66 protein staining was significantly higher in both normal and benign adrenocortical tissue samples as compared to ACC, consistent with WDR66 mRNA expression profile. WDR66 RNA expression level in primary ACC was not associated with overall survival.
Conclusion:
WDR66 gene expression is downregulated in ACC. Our findings suggested that WDR66 may function as a tumor suppressor in ACC and should be evaluated as a therapeutic target.