Novel Prkaca Mutations in Adrenocortical Adenoma and Carcinomas

Presentation Number: MON 392
Date of Presentation: April 3rd, 2017

Rajani Maharjan*, Tobias Akerstrom, Samuel Backman, Per Hellman and Peyman Bjorklund
Uppsala University, Sweden

Abstract

Introduction
Mutation in PRKACA, p.L206R, is the most frequent alteration found in cortisol producing adenomas (CPAs). However PRKACA mutations have not been described in other adrenal tumours. Aim of this study was to determine overall PRKACA mutation status in a large cohort of adrenal tumours of 61 Adrenocortical Carcinomas (ACCs) and to determine mutations occurring outside the hotspot locus of PRKACAin 36 CPAs.

Methods

All the coding exons of PRKACA were re-sequenced in 61 ACCs and 36 CPAs. In silico analysis utilizing Polyphen-2 and PROVEAN were performed to predict the effect of the mutations. Chimera software was used to visualize the location of the mutation in the 3D structure of PRKACA. In vitro analysis of the impact of the mutation was performed by overexpression of the mutant and wildtype PRKACA. Western blot analysis on the tumour samples and the transfected cells were performed.

Results

Three novel mutations, a 15bp deletion (731_745.c.del, P244_E249delinsQ) in one CPA, a 3bp deletion (879_881.c.del, K293del) in one ACC and a missense mutation (305C>T, P102L) in another ACC sample were detected. In silico analysis predicted the mutations to have a damaging effect on the protein. 3D analysis revealed that the mutations were located at or near the critical residues of PRKACA. Increased phosphorylation of ATF1, PRKACA and Serine/Threonine substrates of PKA as a consequence of these mutations were observed. Similar effect was observed on HEK293 cells treated with mutant PRKACA compared to wildtype which demonstrates activating effect of these mutations in PKA/cAMP signalling and downstream pathway.

Conclusion

We have identified and characterized novel mutations in PRKACA. Molecular effects of these mutations were similar to L206R mutation. We conclude that PRKACAmutations are not restricted to the hotspot mutations identified in previous studies and might occur in ACCs.

 

Nothing to Disclose: RM, TA, SB, PH, PB