Variable alterations of mitochondrial microsatellite instability and DNA copy number in pulmonary hamartomas

BACKGROUND: The genetic alteration of mitochondrial DNA has been regarded as an important step in the development of several human tumors. OBJECTIVE: The purpose of this study was to identify frequency of mitochondrial microsatellite instability (mtMSI) and alterations in mitochondrial DNA copy number (mtCN) in pulmonary hamartoma. METHODS: DNA was isolated from tumor tissue and matched non-tumor tissue in 30 patients with pulmonary hamartoma. BAT 25 and 26 were used as nucleus MSI (nMSI) markers, and (C)n and (CA)n in D-loop were used as mtMSI markers. MtCNs were quantified using a competitive quantitative real-time polymerase chain reaction. RESULTS: nMSI was detected in 5 patients (23.8%) and mtMSI was detected in 2 patients (9.5%) of total 21 hamartoma. There were 14 patients (46.7%), 2 patients (6.7%), and a further 14 patients (46.7%) in the decreased, no change, and increased mtCN groups, respectively. The mean relative mtCN were 0.4 ± 0.3 in the decreased and 3.9 ± 5.1 in the increased mtCN groups, respectively. CONCLUSIONS: nMSI was more frequently appeared than mtMSI in hamartomas, and we also found measurements of mtCNs in patients with pulmonary hamartoma to be extremely variable without any characteristic pattern.