BackgroundMitochondria are highly dynamic organelles which remain in a continuous state of fission/ fusion dynamics to meet the metabolic needs of a cell. However, this fission/fusion dynamism has been reported to be dysregulated in most cancers. Such enhanced mitochondrial fission is demonstrated to be positively regulated by some activating oncogenic mutations; such as those of KRAS (Kristen rat sarcoma viral oncogene homologue) or BRAF (B- rapidly accelerated fibrosarcoma), thereby increasing tumor progression/ chemotherapeutic resistance and metabolic deregulation. However, the underlying mechanism(s) are still not clear, thus highlighting the need to further explore possible mechanism(s) of intervention. We sought to investigate how BRAFV600E driven CRC (colorectal cancer) progression is linked to mitochondrial fission/fusion dynamics and whether this window could be exploited to target CRC progression.MethodsWestern blotting was employed to study the differences in expression levels of key proteins regulating mitochondrial dynamics, which was further confirmed by confocal microscopy imaging of mitochondria in endogenously expressing BRAFWT and BRAFV600E CRC cells. Proliferation assays, soft agar clonogenic assays, glucose uptake/lactate production, ATP/ NADPH measurement assays were employed to study the extent of carcinogenesis and metabolic reprograming in BRAFV600E CRC cells. Genetic knockdown (shRNA/ siRNA) and/or pharmacologic inhibition of Dynamin related protein1/Pyruvate dehydrogenase kinase1 (DRP1/PDK1) and/or BRAFV600E were employed to study the involvement and possible mechanism of these proteins in BRAFV600E driven CRC. Statistical analyses were carried out using Graph Pad Prism v 5.0, data was analyzed by unpaired t-test and two-way ANOVA with appropriate post hoc tests.ResultsOur results demonstrate that BRAFV600E CRC cells have higher protein levels of mitochondrial fission factor- DRP1/pDRP1S616 leading to a more fragmented mitochondrial state compared to those harboring BRAFWT. This fragmented mitochondrial state was found to confer glycolytic phenotype, clonogenic potential and metastatic advantage to cells harboring BRAFV600E. Interestingly, such fragmented mitochondrial state seemed positively regulated by mitochondrial PDK1 as observed through pharmacologic as well as genetic inhibition of PDK1.ConclusionIn conclusion, our data suggest that BRAFV600E driven colorectal cancers have fragmented mitochondria which confers glycolytic phenotype and growth advantage to these tumors, and such phenotype is dependent at least in part on PDK1- thus highlighting a potential therapeutic target.

Globally, colorectal cancer is the third most common type of cancer. Genetic instability leading to cancer development is one of the major causes for development of cancer. Alterations in mitochondrial genome, that is, mutations, single-nucleotide polymorphisms, and copy number variations are known to contribute in cancer development. The aim of our study was to investigate association of mitochondrial T16189C polymorphism and copy number variation with colorectal cancer in North Indian population. DNA isolated from peripheral blood of 126 colorectal cancer patients and 114 healthy North Indian subjects was analyzed for T16189C polymorphism and half of them for mitochondrial copy number variation. Genotyping was done using polymerase chain reaction-restriction fragment length polymorphism, and copy number variation was estimated using real-time polymerase chain reaction, numbers of mitochondrial copies and found to be significantly higher in colorectal cancer patients than healthy controls (88 (58-154), p = 0.001). In the regression analysis, increased mitochondrial copy number variation was associated with risk of colorectal cancer (odds ratio = 2.885, 95% confidence interval = 1.3-6.358). However, T16189C polymorphism was found to be significantly associated with the risk of rectal cancer (odds ratio = 5.213, p = 0.001) and non-significantly with colon cancer (odds ratio = 0.867, p = 0.791). Also, false-positive report probability analysis was done to validate the significant findings. Our results here indicate that mitochondrial copy number variation may be playing an important role in the development of colorectal cancer, and detection of mitochondrial copy number variation can be used as a biomarker for predicting the risk of colorectal cancer in North Indian subjects.

The recent investigation on PARK-2, a putative tumor suppressor gene, has found that it has been altered in multiple human malignancies. However, the clinical impact of PARK-2 alteration in uterine cervix carcinoma has not yet been studied. Therefore, we aimed to examine mutations, promoter hypermethylation, and protein expression of PARK-2 among the North Indian patients and their association with clinical parameters to evaluate the implication of PARK-2 in the genesis of cervical cancer. A total of 168 patient samples were processed for mutational analysis by single-strand conformation polymorphism, sequencing, and further in silico analysis of the identified mutations. Promoter hypermethylation by methylation-specific polymerase chain reaction and expression of PARK-2 were performed using immunohistochemistry. Statistical correlation between molecular findings and the clinicopathological parameters was taken to figure out the meaningful outcome. As per our findings, 3.5% (6/168) tumors showed novel missense mutations in exon 11 of PARK-2. In silico analysis showed high structural deviations manifested by mutations, A398D and Y391N, in both mutant proteins as compared to wild type. Promoter hypermethylation was observed in total of 29% of (48/168) tumor samples. Furthermore, 46.43% tumors (78/168) exhibited loss of PARK-2 expression in cervical carcinoma. The loss of expression of PARK-2 when correlated with clinical parameters resulted in significant association with tumor stage (p = 0.002) and with histological grade (p = 0.025). However, only clinical stage remained significant after Bonferroni correction (p < 0.007). A trend was observed between PARK-2 promoter hypermethylation and its protein expression. Our study provided sufficient information and insight for investigation of PARK-2 and highlighted its role as a tumor suppressor gene in cervical cancer in North Indian population.

Background Progression of breast cancer involves both genetic and epigenetic factors. Parkin gene has been identified as a tumor suppressor gene in the pathogenesis of various cancers. Nevertheless, the putative role of Parkin in breast cancer remains largely unknown. Therefore, we evaluated the regulation of Parkin through both genetic and epigenetic mechanisms in breast carcinoma. Method A total of 156 breast carcinoma and their normal adjacent tissue samples were included for mutational analysis through SSCP, and sequencing. MS-PCR was employed for methylation study whereas Parkin protein expression was evaluated using immunohistochemistry and western blotting. For the survival analysis, Kaplan–Meier curve and Cox’s proportional hazard model were used. Results In expression analysis, Parkin protein expression was found to be absent in 68% cases of breast cancer. We found that aberrant promoter methylation of Parkin gene is a frequent incident in breast cancer tumors and cell lines. Our MS-PCR result showed that Parkin promoter methylation has a significant role ( p = 0.0001) in reducing the expression of Parkin protein. Consistently, expression of Parkin was rectified by treatment with 5-aza-2-deoxycytidine. We also found significant associations of both Parkin negative expression and Parkin promoter methylation with the clinical variables. Furthermore, we found a very low frequency (5.7%) of Parkin mutation with no clinical significance. In survival analysis, patients having Parkin methylation and Parkin loss had a worse outcome compared to those harboring none of these events. Conclusion Overall, these results suggested that promoter methylation-mediated loss of Parkin expression could be used as a prognostic marker for the survival of breast cancer. Electronic supplementary material The online version of this article (10.1186/s12885-019-6013-6) contains supplementary material, which is available to authorized users.

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