Black bars mark the averaged percentage of cells for each subgroup

al regulation of Drp1 have been reported; it is possible that in oncocytic tumors, Drp1 could be stabilized, namely by Ser-616 phosphorylation or Ser-637 dephosphorylation, and translocated to mitochondria, thus promoting an unbalanced organelle division as previously described. We saw that the oncocytic cell line displays mitochondria which are Luteolin 7-O-β-D-glucoside supplier particularly small and often with an aberrant shape. We also observed a significant co-localization of Drp1 with the mitochondrial membrane upon heavy membrane fraction analysis in the same model. We then logically went on to investigate on these cells’ migratory capability. By scratch-wound and transwell assay we observed that oncocytic XTC.UC1 cells have higher migration/invasion capacity. XTC.UC1 being a cell line derived from a metastatic tumor, it makes sense that it has a higher motility and migration ability than TPC1. These observations are not biased by differences in cell proliferation rates since the proliferation rate is higher in TPC1 than in XTC.UC1 cell line. Given that we observed Drp1 overexpression in the oncocytic cell line as well in the oncocytic tumors, where it associates with malignancy, we hypothesize that the Drp1 protein may have a role in the observed higher migration/invasion abilities of the PubMed ID:http://www.ncbi.nlm.nih.gov/pubmed/19763407 XTC.UC1 cells. Our hypothesis was supported by the observation that the inhibition of Drp1 function, both pharmacologically and genetically, leads to a decrease in the migration/invasion capacity of the oncocytic XTC.UC1 cells. Our results match previously published data showing that mitochondrial dynamics regulates lymphocyte and breast cancer cell migration. In both these experimental models, either inhibiting the fission process by Drp1 downregulation or promoting a hiperfused mitochondrial network phenotype, by overexpressing Mfn1, led to limited cell migration or invasion. In our case also, a block of Drp1 was sufficient to reduce the oncocytic cell migration. Our hypothesis would be better verified if we could use other cell lines, namely a cell line derived from an oncocytic adenoma and one from a non-metastatic primary oncocytic carcinoma. However these cell lines do not exist. Alternatively, we cannot rely on primary cultures of oncocytic and non-oncocytic, benign or malignant thyroid tumors, since unfortunately the culture of primary thyroid cells has been very difficult to obtain and do not last in the laboratory long enough for us to perform the studies. Those cell lines, if available, would be valuable tools for understanding not only thyroid tumors’ oncocytic transformation, but also their malignant transformation. To sum up, our data show that the mitochondrial PubMed ID:http://www.ncbi.nlm.nih.gov/pubmed/19762491 fission proteins, Drp1 and Fis1, are overexpressed in thyroid oncocytic cell tumors. This suggests that the mitochondrial fission process upregulation might contribute to mitochondrial accumulation in tumor cells and thus be responsible, at least partially, for the oncocytic cell phenotype. Furthermore, we found that mitochondrial fission protein expression, in particular Drp1 overexpression, correlates with oncocytic thyroid tumor malignancy ex vivo and also with a higher migration/invasion ability of the XTC.UC1 cell line, an oncocytic cell line derived from a metastatic malignant thyroid tumor. Further studies on the mitochondrial dynamics are needed to better dissect some of the cellular dysfunctions observed in tumor cells in general and in oncocytic tumor cells in particular. 14 / 17 Mitochondrial Dyn