Whole Mitochondrial Genome Analysis in Non–Small Cell Lung Carcinoma Reveals Unique Tumor-Specific Somatic Mutations

Abstract

Context.— Mitochondria and mitochondrial DNA have been suggested to play a role in cancer initiation and progression. Knowledge of mitochondrial DNA could provide a breakthrough to advance cancer management. Objective.— To identify the mitochondrial DNA landscape in non–small cell lung carcinoma. Design.— The adenocarcinoma set consisted of 365 pairs of adenocarcinomas and normal lung tissues, whereas the metastasis set included 12 primary non–small cell carcinomas, 15 metastatic tumors, and their normal counterparts. Tumor-specific somatic variants were identified, and if a variant showed heteroplasmy, the proportion of minor alleles was evaluated. Variants with greater than 10% change in allele frequency between tumor and normal pairs were identified as “heteroplasmic shifts.” Results.— Tumor-specific variants appeared throughout the whole mitochondrial genome, without a common hot spot. Distinct variant profiles were seen in 289 (79.18%) of all individual adenocarcinomas. The presence of a unique profile and the number and loading of heteroplasmic shifts in tumors increased with higher stage or lymph node metastasis, and were related to shorter survival. In the metastasis set, the primary tumor variants were generally found in metastatic tumors. Conclusions.— This study shows that somatic mitochondrial DNA mutations present with diverse locations and unique profiles in each individual tumor, implying their clinicopathologic utility.