BAP1 mutations define a homogeneous subgroup of hepatocellular carcinoma with fibrolamellar-like features and activated PKA

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Decabromodiphenyl ether-induced PRKACA hypermethylation contributed to glycolipid metabolism disorder via regulating PKA/AMPK pathway in rat and L-02 cells

BDE-209 is the most prevalent congener of polybrominated diphenyl ethers and has high bioaccumulation in humans and animals. BDE-209 has been reported to disrupt glycolipid metabolism, but the mechanisms are still unclear. In this study, we found that BDE-209 induced liver tissue injury and hepatotoxicity, increased the glucose and total cholesterol levels in the serum of rats, and increased glucose and triglyceride levels in L-02 cells. BDE-209 exposure changed the PKA, p-PKA, AMPK, p-AMPK, ACC, and FAS expression in rats’ liver and L-02 cells. Moreover, BDE-209 induced PRKACA-1 hypermethylation in L-02 cells. AMPK activator (AICAR) inhibited the changes of p-AMPK, ACC, and FAS expression and elevation of glucose and triglyceride levels induced by BDE-209. DNA methylation inhibitor (5-Aza-CdR) reversed BDE-209 induced alters of PKA/AMPK/ACC/FAS signaling pathway. These results demonstrated that BDE-209 could disrupt the glycolipid metabolism by causing PRKACA-1 hypermethylation to regulate the PKA/AMPK signaling pathway in hepatocytes.     

Microinsertions in PRKACA cause activation of the protein kinase A pathway in cardiac myxoma

Cardiac myxoma is the most common cardiac tumour. Most lesions occur sporadically, but occasional lesions develop in patients with Carney complex, a syndrome characterized by cardiac myxoma, spotty pigmentation, and endocrine overactivity. Two‐thirds of patients with Carney complex harbour germline mutations in PRKAR1A, which encodes the type I regulatory subunit of protein kinase A (PKA). Most studies have not found a mutation in PRKAR1A in sporadic cardiac myxoma cases. Recent studies identified frequent mutations in PRKACA, which encodes the catalytic subunit of PKA, in cortisol‐secreting adrenocortical adenoma cases. To determine whether the PRKACA mutation is involved in the tumourigenesis of cardiac myxoma, we performed Sanger sequencing of 41 specimens of sporadic cardiac myxoma to test for the presence of mutations in the coding regions and intron–exon boundaries of PRKACA. Mutations were identified in four cases (9.7%). In contrast to the point mutations identified in adrenocortical adenoma, all mutations were in‐frame microinsertions of 18–33 bp clustered in exons 7 and 8. The mutated PRKACA proteins lost their ability to bind to PRKAR1A, and thereby lead to constitutive activation of the PKA pathway. Together with previous reports of PRKAR1A mutations in syndromic cardiac myxoma, our study demonstrates the importance of the PKA pathway in the tumourigenesis of cardiac myxoma. Copyright © 2017 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

Fibrolamellar carcinoma: A histologically unique tumor with unique molecular findings

Fibrolamellar carcinoma is a unique type of hepatocellular carcinoma with a distinctive predilection for young patients without underlying liver disease, characteristic large neoplastic cells with intervening, dense fibrosis, co-expression of keratin 7 and CD68 and activation of protein kinase A (most often by formation of DNAJB1-PRKACA). Fibrolamellar carcinoma has a similar prognosis to conventional hepatocellular carcinomas arising in non-cirrhotic livers. The current American Joint Cancer Committee staging system does not provide optimal stratification of patients with fibrolamellar carcinoma and an alternate systems should be considered in the future. The only effective treatment for fibrolamellar carcinoma is complete resection. Novel therapies may be on the horizon as investigation into the molecular biology of fibrolamellar carcinoma continues.