Sequence analysis of the catalytic subunit of PKA in somatotroph adenomas

Abstract

Objective: The pathogenetic mechanisms of sporadic somatotroph adenomas are not well understood, but derangements of the cAMP pathway have been implicated. Recent studies have identified L206R mutations in the alpha catalytic subunit of protein kinase A (PRKACA) in cortisol-producing adrenocortical adenomas and amplification of the beta catalytic subunit of protein kinase A PRKACB in acromegaly associated with Carney complex. Given that both adrenocortical adenomas and somatotroph adenomas are known to be reliant on the cAMP signalling pathway, we sought to determine the relevance of the L206R mutation in both PRKACA and PRKACB for the pathogenesis of sporadic somatotroph adenomas. Design: Somatotroph adenoma specimens, both frozen and formalin-fixed, from patients who underwent surgery for their acromegaly between 1995 and 2012, were used in the study. Methods: The DNA sequence at codon 206 of PRKACA and PRKACB was determined by PCR amplification and sequencing. The results were compared with patient characteristics, the mutational status of the GNAS complex locus and the tumour granulation pattern. Results: No mutations at codon 206 of PRKACA or PRKACB were found in a total of 92 specimens, comprising both WT and mutant GNAS cases, and densely, sparsely and mixed granulation patterns. Conclusions: It is unlikely that mutation at this locus is involved in the pathogenesis of sporadic somatotroph adenoma; however, gene amplification or mutations at other loci or in other components of the cAMP signalling pathway, while unlikely, cannot be ruled out.

Landscape of somatic mutations in sporadic GH-secreting pituitary adenomas

“…In particular, no somatic mutations have been also detected at the gene GPR101, probably due to the low reported frequency of this mutations (11/248 cases) (33), and, at both the exome sequencing and the targeted sequencing, we did not find any mutations of the PRKACA and USP8 genes. These findings further confirm that both these genetic alterations are not involved in the pathogenesis of GH-secreting adenomas (32,36). Interestingly, several non-recurrent alterations affected other genes involved in the cAMP signaling besides GNAS (see Table 2).…”

“…Recently, mutations affecting the gene encoding the catalytic subunit a of the PKA (PRKACA) have been reported in a large proportion of cortisol-secreting adrenocortical adenomas (26,27,28,29,30), resulting in an increased PKA activity (31). Nevertheless, no hot spot mutations of PRKACA have been identified in a large cohort of GH-secreting adenomas (32). Finally, a recurrent somatic mutation in the GPR101 gene, which encodes an orphan G-protein-coupled receptor (GPCR), has been recently reported in some adults with acromegaly (4% of cases) (33).…”

Germline PRKACA amplification causes variable phenotypes that may depend on the extent of the genomic defect: molecular mechanisms and clinical presentations

“…In addition, 92 specimens from sporadic somatotroph adenomas were screened for mutations at codon 206 of PRKACA or PRKACB, and none were identified. 27 …”

Double adrenocortical adenomas harboring independent KCNJ5 and PRKACA somatic mutations

“…Bidirectional Sanger sequencing analyses of KCNJ5 and PRKACA gene for DNA samples isolated from each tumor piece were performed using primers as follows: KCNJ5 forward 5′-GGACCATGTTGGCGACCAAGAGTG-3′, reverse 5′-GACAAACATGCACCCCACCATGAAG-3′; PRKACA forward 5′-GGTGACAGACTTCGGTTTCGC-3′, reverse 5′- CCTTGTTGTAGCCCTGGAGCA-3′ (14). For each PCR reaction, 20 ng of template gDNA was used.…”