Objective: Cell-free DNA fragments (cf-DNA) of tumour cells are often found in the blood downstream to the tumour due to the high apoptosis or necrosis rate of the cells. Primary aldosteronism (PA), a curable cause of secondary hypertension, are commonly due to an autonomous aldosterone-producing adenoma that harbours a somatic mutation in an aldosterone-driver gene. We thus aimed to see if genotyping of cf-DNA for mutations in aldosterone-driver genes could be used as a biomarker for APA. Design and Methods: Genotyping of cf-DNA from the adrenal vein samples (AVS) of PA patients was performed using the Agena MassARRAY platform and validated by Sanger sequencing. In this study, six samples of cf-DNA from the left and right adrenals of three PA patients were interrogated. Results: Of the three PA patients, two had left adrenalectomy and one had right adrenalectomy. CTNNB1 S45 mutation was detected by the Agena MassArray platform in the cf-DNA of both right adrenal and left adrenal vein samples of all patients (Patient 1, Patient 2 and Patient 3). In Patient 1, Sanger sequencing confirmed a CTNNB1 S45del mutation in both cf-DNA of right adrenal and left adrenal vein samples. In Patient 3, who was found to have left adrenal hyperplasia, the cf-DNA of the right adrenal and left adrenal vein samples was also detected to have a KCNJ5 G151R mutation by the Agena MassArray platform which was confirmed by Sanger sequencing. Interestingly, only the cf-DNA of the left adrenal was found to have a CACNA1D S672L mutation in Patient 3. Conclusion: These results suggest that genotyping cf-DNA from AVS samples are able to detect aldosterone-driver mutations present in the APA. However, as AVS is an invasive procedure, it would be best if genotyping of cf-DNA from periphery blood can be performed. Therefore, further work is needed to ensure this strategy can be non-invasive as then it can be used as a screening method before AVS.
Read full abstract