| Transmembrane protein TMEM 56 was first identified as an IKK-associated protein by mass spectrometry in Dr. Ebrahim Zandi's lab. This 263AA protein was found to be localized in mitochondria and interacts with alpha and beta subunit of ATPase. In some lung, head and neck cancer cells, TMEM 56 was shown to have a correlation with mitochondrial abundance. In addition, it could act as a potential tumor suppressor in HEK 293T cells. This thesis was based on the conclusion of previous studies to research the function of TMEM 56 protein on tumorigenic growth of MCF-7 human breast cancer cell line. Stable cell lines (CON-shRNA, TM-shRNA, GFP-control, and GFP-TM MCF-7) were established to knock-down and over-express TMEM 56 expression. Xenograft assay in immune-deficient mice showed that tumors formed by both GFP-TM and TM-shRNA MCF-7 cells were smaller than GFP-control and CON-shRNA cells, respectively. This indicated that a deviation from the basal expression level of TMEM 56 would inhibit tumor progression in MCF-7 cells. Immunohistochemistry and Western Blot with ATPase beta antibody showed that over-expressing or down-regulating TMEM 56 did not change ATPase beta expression, suggesting that TMEM 56 protein will not influence ATPase beta level. In summary, data in this study suggest that the difference in cell type is an important determinant for the function of TMEM 56 protein. Specifically, in MCF-7 cells, the abnormal TMEM 56 protein level might result in the inhibition of tumor progression without influencing ATPase â expression. |
