Mitochondrial DNA haplogroups and somatic mutations are associated with lung cancer in patients from Southwest China.

Mitochondrial DNA mutations play crucial roles in the pathogenesis and progression of human malignancies. Therefore, to determine whether maternal background or mitochondrial DNA somatic mutations were essential cofactors in the lung cancer of Chinese patients as well, the complete mitochondrial DNA displacement loop of the primary cancerous, matched para-cancerous normal and distant normal tissues for 79 Chinese patients with lung cancer were analyzed in this study. Our results indicated that the higher detected frequency of haplogroups prevalent in southern East Asia (53.16%; 42/79) versus those of northern East Asia in the studied population supported the southern East Asian characteristics of the Chinese lung cancer group. Further statistical analysis revealed that the haplogroups F* and G* contributed to the susceptibility to lung cancer in Chinese patients. In addition, by comparing sequences from different tissues of the same patients, a total of eight somatic mutations from six patients were detected. Combined with the fourteen somatic mutations identified in our previous study, the somatic mutation spectrum of the 79 Chinese patients with lung cancer was 25.32% (20/79). Our results suggest that mitochondrial DNA haplogroups and somatic mutations are associated with lung cancer in patients from Yunnan, Southwest China, and that somatic mitochondrial DNA mutations in the displacement loop can serve as potential biomarkers for clinical utility.

Deciphering the spectrum of somatic mutations in the entire mitochondrial DNA genome.

The mitochondrion is a crucial intracellular organelle responsible for regulating cellular energy metabolism, producing free radicals, initiating and executing the apoptotic pathways. Previous studies have shown that somatic mutations in mitochondrial DNA are associated with various tumors, which may be involved during carcinogenesis and tumor progression. To examine the mutation pattern in cancer, 625 reported somatic mutations in the mitochondrial DNA genome were analyzed. We found that, except for deletions and insertions, most somatic mutations were point mutations, accounting for 89.44% of somatic mutations. Transition was the predominant form of somatic mutation in the entire mitochondrial DNA genome, accounting for 87.12% of point mutations, most of which were homoplastic. Frequency statistics analysis of point mutations indicated that, except for 3 tRNA genes, the mutations were distributed on all resting genes and in the D-loop region, with the latter showing the highest frequency of somatic mutation (19.34%), followed by the tRNA leucine 2 gene and non-coding regions between base pairs 5892 and 5903, while 13 coding-region genes and 2 rRNA genes showed a relatively lower frequency of somatic point mutations. Nonsynonymous mutations and terminal amino acid changes were the primary point somatic mutations detected from 13 coding-region genes, which may cause mitochondrial dysfunction in cancer cells. We found that the somatic mutations may affect the mitochondrial DNA genome; the non-coding region should be examined to identify somatic mutations as potential diagnostic biomarkers for early detection of cancer.

Identification of warm day and cool night conditions induced flowering-related genes in a Phalaenopsis orchid hybrid by suppression subtractive hybridization.

The influence of warm day and cool night conditions on induction of spikes in Phalaenopsis orchids has been studied with respect to photosynthetic efficiency, metabolic cycles and physiology. However, molecular events involved in spike emergence induced by warm day and cool night conditions are not clearly understood. We examined gene expression induced by warm day and cool night conditions in the Phalaenopsis hybrid Fortune Saltzman through suppression subtractive hybridization, which allowed identification of flowering-related genes in warm day and cool night conditions in spikes and leaves at vegetative phase grown under warm daily temperatures. In total, 450 presumably regulated expressed sequence tags (ESTs) were identified and classified into functional categories, including metabolism, development, transcription factor, signal transduction, transportation, cell defense, and stress. Furthermore, database comparisons revealed a notable number of Phalaenopsis hybrid Fortune Saltzman ESTs that matched genes with unknown function. The expression profiles of 24 genes (from different functional categories) have been confirmed by quantitative real-time PCR in induced spikes and juvenile apical leaves. The results of the real-time PCR showed that, compared to the vegetative apical leaves, the transcripts of genes encoding flowering locus T, AP1, AP2, KNOX1, knotted1-like homeobox protein, R2R3-like MYB, adenosine kinase 2, S-adenosylmethionine synthetase, dihydroflavonol 4-reductase, and naringenin 3-dioxygenase accumulated significantly higher levels, and genes encoding FCA, retrotransposon protein Ty3 and C3HC4-type RING finger protein accumulated remarkably lower levels in spikes of early developmental stages. These results suggested that the genes of two expression changing trends may play positive and negative roles in the early floral transition of Phalaenopsis orchids. In conclusion, spikes induced by warm day and cool night conditions were complex in Phalaenopsis orchids; nevertheless, several molecular flowering pathway-related genes were found. The acquired data form the basis for a molecular understanding of spike induction by warm day and cool night conditions in Phalaenopsis orchids.