Multiple Recurrent Cardiac Myxomas With Protein Kinase A Regulatory Subunit 1α Gene Mutation

Misattribution of Dyspnea: Unveiling Atrial Myxoma as the True Culprit

Cardiac myxomas are the most common primary tumors of cardiac neoplasm, predominantly originating within the left atrium (LA). In the present case, a 41-year-old male, identified as a heavy smoker for 15 years, previously diagnosed with chronic obstructive pulmonary disease (COPD) and currently undergoing treatment, presented with a history of dyspnea persisting for one year. Initially, the patient presented to the internal medicine outpatient clinic and was diagnosed with an exacerbation of COPD, but subsequent evaluation revealed the presence of a large mobile pedunculated mass situated in the LA using echocardiography. Subsequently, the mass was surgically excised using a median sternotomy approach. The histopathological examination confirmed cardiac myxoma. This occurrence underscores the significance of considering cardiac myxoma as a plausible differential diagnosis in instances of dyspnea to avert potential complications.

Crosstalk between KIF1C and PRKAR1A in left atrial myxoma

Cardiac myxoma (CM) is the most common benign cardiac tumor, and most CMs are left atrial myxomas (LAMs). Six variations of KIF1C, c.899 A > T, c.772 T > G, c.352 A > T, c.2895 C > T, c.3049 G > A, and c.*442_*443dup in left atrial myxoma tissues are identified by whole-exome sequencing (WES) and Sanger sequencing. RNA-seq and function experiments show the reduction of the expression of KIF1C and PRKAR1A caused by rare variations of KIF1C. KIF1C is observed to be located in the nucleus, bind to the promoter region of PRKAR1A, and regulate its transcription. Reduction of KIF1C decreases PRKAR1A expression and activates the PKA, which causes an increase in ERK1/2 phosphorylation and SRC-mediated STAT3 activation, a reduction of CDH1, TP53, CDKN1A, and BAX, and eventually promotes tumor formation both in vitro and in vivo. The results suggest that inhibition of KIF1C promotes the pathogenesis of LAM through positive feedback formed by the crosstalk between KIF1C and PRKAR1A.