Breast cancer-associated mitochondrial DNA haplogroup promotes neoplastic growth via ROS-mediated AKT activation.

In the last decade, mitochondrial DNA (mtDNA) haplogroups have been associated with the occurrence of breast cancer. However, the underlying mechanism is not known. Combining a case-control study with a large cohort of women from Southern China with breast cancer and functional analyses with trans-mitochondrial technology, we demonstrate that the D5 haplogroup is associated with an increased risk of breast cancer [odds ratio (OR) = 2.789; 95% confidence interval (CI) [1.318, 5.901]; p = 0.007]. Furthermore, mitochondrial respiration, mitochondrial ATP content and membrane potential, were lower in both bone osteosarcoma and breast cancer cell models of cytoplasmic hybrids (cybrids) containing the mtDNA D5 haplogroup than in those with non-D5 haplogroups. Using in vitro and in vivo tumorigenicity assays, we found that cells with the D5 haplogroup were more susceptible to tumorigenesis compared to cells with non-D5 haplogroups. Mechanistically, the D5 haplogroup may promote tumorigenesis at least partially through activation of the v-AKT murine thymoma viral oncogene (AKT) via phosphorylation of threonine 308, which is mediated by increased reactive oxygen species generation in D5 cybrids. Our findings demonstrate that there is decreased mitochondrial function in cells with the D5 haplogroup compared to cells with non-D5 haplogroups, which may be associated with increased neoplastic growth in breast cancer.

Identification of five novel SCN1A variants.

Background: Epilepsy is characterized by recurrent unprovoked seizures. Mutations in the voltage-gated sodium channel alpha subunit 1 (SCN1A) gene are the main monogenic cause of epilepsy. Type and location of variants make a huge difference in the severity of SCN1A disorder, ranging from the mild phenotype (genetic epilepsy with febrile seizures plus, GEFS+) to the severe phenotype (developmental and epileptic encephalopathies, DEEs). Dravet Syndrome (DS) is an infantile-onset DEE, characterized by drug-resistant epilepsy and temperature sensitivity or febrile seizures. Genetic test results reveal SCN1A variants are positive in 80% DS patients and DS is mainly caused by de novo variants. Methods: Trio-whole exome sequencing (WES) was used to detect variants which were associated with clinical phenotype of five probands with epilepsy or twitching. Then, Sanger sequencing was performed to validate the five novel SCN1A variants and segregation analysis. After analyzing the location of five SCN1A variants, the pathogenic potential was assessed. Results: In this study, we identified five novel SCN1A variants (c.4224G > C, c.3744_3752del, c.209del, c.5727_5734delTTTAAAACinsCTTAAAAAG and c.5776delT) as the causative variants. In the five novel SCN1A variants, four were de novo and the remaining one was inherited. All novel variants would be classified as "pathogenic" or "likely pathogenic." Conclusion: The five novel SCN1A variants will enrich the SCN1A mutations database and provide the corresponding reference data for the further genetic counseling.

Oncogenic HSP60 regulates mitochondrial oxidative phosphorylation to support Erk1/2 activation during pancreatic cancer cell growth.

HSP60 is a mitochondrial localized quality control protein responsible for maintaining mitochondrial function. Although HSP60 is considered both a tumor suppressor and promoter in different types of cancer, the role of HSP60 in human pancreatic ductal adenocarcinoma (PDAC) remains unknown. In this study, we demonstrated that HSP60 was aberrantly expressed in human pancreatic cancer tissues and cell lines. Analysis of the Cancer Genome Atlas database revealed that HSP60 expression is positively correlated with pancreatic cancer. Further, knockdown of HSP60 attenuated pancreatic ductal cancer cell proliferation and migration/invasion, whereas ectopic expression of HSP60 increased tumorigenesis. Using an in vivo tumorigenicity assay, we confirmed that HSP60 promoted the growth of pancreatic ductal cancer cells. Functional analyses demonstrated that HSP60 plays a key role in the regulation of mitochondrial function. Mechanistically, both HSP60 knockdown and oxidative phosphorylation (OXPHOS) inhibition by metformin decreased Erk1/2 phosphorylation and induced apoptosis and cell cycle arrest, whereas Erk1/2 reactivation with EGF promoted cell proliferation. Intriguingly, in vitro ATP supplementation partially restored Erk1/2 phosphorylation and promoted proliferation in PDAC cells with HSP60 knockdown and OXPHOS inhibition. These results suggest that mitochondrial ATP is an important sensor of Erk1/2 regulated apoptosis and the cell cycle in PDAC cells. Thus, our findings indicate for the first time that HSP60 may serve as a novel diagnostic target of human pancreatic cancer, and that inhibition of mitochondrial function using drugs such as metformin may be a beneficial therapeutic strategy targeting pancreatic cancer cells with aberrant function of the HSP60/OXPHOS/Erk1/2 phosphorylation axis.

mtDNA Haplogroup N9a Increases the Risk of Type 2 Diabetes by Altering Mitochondrial Function and Intracellular Mitochondrial Signals.

Mitochondrial DNA (mtDNA) haplogroups have been associated with the incidence of type 2 diabetes (T2D); however, their underlying role in T2D remains poorly elucidated. Here, we report that mtDNA haplogroup N9a was associated with an increased risk of T2D occurrence in Southern China (odds ratio 1.999 [95% CI 1.229-3.251], P = 0.005). By using transmitochondrial technology, we demonstrated that the activity of respiratory chain complexes was lower in the case of mtDNA haplogroup N9a (N9a1 and N9a10a) than in three non-N9a haplogroups (D4j, G3a2, and Y1) and that this could lead to alterations in mitochondrial function and mitochondrial redox status. Transcriptome analysis revealed that OXPHOS function and metabolic regulation differed markedly between N9a and non-N9a cybrids. Furthermore, in N9a cybrids, insulin-stimulated glucose uptake might be inhibited at least partially through enhanced stimulation of ERK1/2 phosphorylation and subsequent TLR4 activation, which was found to be mediated by the elevated redox status in N9a cybrids. Although it remains unclear whether other signaling pathways (e.g., Wnt pathway) contribute to the T2D susceptibility of haplogroup N9a, our data indicate that in the case of mtDNA haplogroup N9a, T2D is affected, at least partially through ERK1/2 overstimulation and subsequent TLR4 activation.