Ps-bpb06-10: distribution of cacna1d somatic mutations among cyp11b2 immunohistochemistry-guided samples of aldosterone-producing adenoma (apa)

Objectives: Past studies in Afro-Caribbean primary aldosteronism (PA) patients have found CACNA1D mutations to be the most common aldosterone-driving mutation among their cohort; a striking difference to Caucasian and Oriental cohorts where KCNJ5 mutations are reported to be the most common. However not many studies had used aldosterone synthase (CYP11B2) immunohistochemistry (IHC)-guided sequencing approach of the whole CACNA1D gene, performing instead unguided adenoma sampling and hotspot sequencing. We thus performed CYP11B2 IHC-guided whole gene sequencing on APAs from an Oriental cohort (Malaysia) and a Caucasian cohort (Czech Republic) for comparison. Design and method: Surgically removed adrenals from 100 Malaysian and Czech PA patients with unilateral disease were studied. Genomic DNA was isolated from adenoma FFPE sections that had a positive CYP11B2 IHC staining and somatic mutations analysis were performed by next generation sequencing (NGS) of known aldosterone-driver genes. Predicted pathogenic mutations were verified by Sanger Sequencing. Results: Out of 100 FFPE samples sent for NGS, 36 were excluded due to the quality of the data. In total 58 of 64 APAs (87.5%) had a pathogenic aldosterone-driver somatic mutation. KCNJ5 mutations were the most common (n = 37, 57.8%), followed by CACNA1D (n = 11, 20.3%), ATP1A1 (n = 6, 9.4%), ATP2B3 (n = 3, 4.7%) and CTNNB1 (n = 2, 3.1%) mutations. Of particular interest, one APA sample had two pathogenic somatic mutations, CACNA1D p.Val1373Met and CTNNB1 : p.Thr41Ala. SIFT and Polyphen2 scores predicted both mutations to be deleterious. Both mutations have previously been reported separately to cause APAs. The CACNA1D/CTNNB1 mutant APA, was solitary, with homogeneous CYP11B2 expression while negative for CYP17A1 expression. The APA was adrenalectomized from a 53-year-old male Czech patient. The majority of patients with APAs harboring CACNA1D mutations were male (n = 8, 72.7%) and from the Czech cohort (n = 7, 64%). There were no significant differences in age at adrenalectomy between patients harboring a CACNA1D mutant APA (45 ± 3) and those with a non- CACNA1D mutant APA (48 ± 2). Conclusions: Solitary ZG APAs can harbor both a CACNA1D and a CTNNB1 mutation. The prevalence of CACNA1D in this CYP11B2-IHC guided study is consistent with previous results reported in Oriental and Caucasian cohorts. Although CACNA1D is not the top genetic alteration responsible for APAs in these cohorts, CACNA1D may still be a potential key player in idiopathic hyperaldosteronism and aldosterone-producing micronodules. Thus further study is required to characterize the distribution of CACNA1D pathogenic mutations in bilateral PA.