Association of acetylcholine receptor α-subunit gene expression in mixed thymoma with myasthenia gravis

Objective: To investigate the association of MG with the transcription of muscular or neuronal acetylcholine receptor (AChR) subunit genes in thymomas. Background: Many steps in the pathogenesis of MG have been elucidated but, with rare exceptions, its etiology is unknown. In patients with MG with thymoma, the tumor probably elicits autoimmunity to AChR, but it is enigmatic why MG develops in some patients but not in others. Methods: Reverse transcriptase (RT)-PCR, immunohistochemistry, and immunofluorescence studies were carried out to investigate AChR expression in 35 patients with thymoma. Statistical analysis was used to specify significant differences between thymoma subtypes. Results: Considering all thymomas (n = 35), no correlation was found between MG status and AChR gene expression as detected by RT-PCR. However, when histologically defined thymoma subtypes were studied separately, transcription of the muscular AChR P3A − α-subunit gene was significantly associated (α + α isoform, β, γ, δ, and e) and the α 2 and β 4 neuronal AChR subunits, no such correlation was detected. Conclusions: Expression of the P3A − AChR α-subunit gene might be important for the pathogenesis of MG in mixed thymomas, suggesting etiologic heterogeneity of paraneoplastic MG among patients with histologically different thymoma subtypes.