|M.Sc Student||Krayzler Ella|
|Subject||TSPO as a Marker of Oral Cancer Progression|
|Department||Department of Medicine||Supervisors||Professor Rafael M. Nagler|
|Professor Emeritus Moshe Gavish|
|Full Thesis text|
Translocator protein 18kDa (TSPO), previously called peripheral benzodiazepine receptor (PBR) has been known to the scientific community since 1977. It has been associated with a 32 kDa voltage-dependent anion channel (VDAC), and a 30 kDa adenine nucleotide transporter (ANT). Those proteins are a crucial part of the mitochondrial permeability transport pore (MPTP). Over the years, these proteins have been associated with numerous cellular functions such as steroidogenesis, cell proliferation and apoptosis. Studies found increased TSPO levels in different type of cancers.
Oral cancer is the most common malignancy of the head and neck. This cancer is characterized by a high rate of morbidity and high levels of mortality (about 50%). The aim of the present study was to examine a putative involvement of TSPO in oral cancer and to characterize 2 oral cancer cell lines (SCC-25 and SCC-15) in context of TSPO density and affinity. Another aim of this research was to see correlations between cigarette smoke (CS) exposure as model of reactive oxygen species (ROS) and TSPO characteristics.
We found different patterns of [3H]PK 11195 binding to TSPO. We also found that different TSPO densities among the cell lines, correlated with doubling time measurement in vitro and in situ. The SCC-15 cell line exhibits two different population of TSPO with different binding characteristics (Bmax and Kd), while SCC-25 cell line consisted of only one population showing high affinity to [3H]PK 11195.
Our project also included the building of a device to expose cells in culture to CS, and evaluate changes regarding TSPO and its associated proteins. We confirm that CS mediates its damage via reactive oxygen species by performing carbonyl assays. This assay measures the oxidative specific damage to proteins. We found that CS causes specific decreases in TSPO binding activity as well as increases in TSPO and VDAC proteins. This contradiction may be explained by the fact that increases in protein amount may not be equivalent to increases in protein activity. Another possible explanation is desensitization or inhibition by molecules present in CS. We also found that CS caused decreases in the G2/M fraction in the cells. These CS induced changes may lead to increased cell tumorigenicity which then could lead to oral cancer progression.
This study suggests that higher levels of TSPO in oral tumorigenic cells could be responsible for greater cell proliferation levels in vitro and in situ. Furthermore, this study could provide a possible explanation for oral cancer progression that involves the TSPO protein.