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- Creators: Barrett, The Honors College
- Creators: Kodibagkar, Vikram
Using in vitro experimental models of both SAOS-2 (non-metastatic) and 143-b (metastatic) osteosarcoma cell lines and Western blot analysis, we have demonstrated that basal levels of molecular chaperone BiP (Binding immunoglobulin protein, or GRP-78) and peIF2α (phospho-eukaryotic initiation factor 2 alpha), both markers of the UPR, were higher in SAOS-2 than 143-b cells. We also show that both these markers were further up-regulated upon exposure to hypoxia, as evidenced by the increase in banding intensity in both SAOS-2 and 143-b cells. Furthermore, analysis of another UPR marker, ATF6 (activating transcription factor 6) showed that basal levels of active nuclear ATF6 were slightly higher in SAOS-2 cells than in 143-b cells. However, unlike the other UPR markers these levels were significantly reduced upon exposure to hypoxia (0.1% O2). In addition to hypoxia, treatment with Cisplatin also had similar effects on the expression of aforementioned UPR markers: BiP and peIF2α. We found that the 143-b OS cells were more sensitive to the Cisplatin treatment than the SAOS-2 OS cells, and thus more prone to cell-mediated death.
Our findings shed light on the unknown mechanisms underlying chemotherapeutic drug resistance in osteosarcoma patients. Our research may lead to novel therapies that seek out and destroy the chemoresistant OS cells within the hypoxia core of tumors, thereby preventing survival and metastasis, and ultimately improving the chances of survival amongst OS patients.
Our cells need constant fuel and oxygen for the body to work properly and maintain cellular function. In high altitudes tissue oxygen levels fall and the body must work against this hypoxic challenge to maintain energetics and limit oxidative stress. Mammals living at high altitudes are challenged to sustain thermogenesis and aerobic exercise despite reduced amounts of available oxygen. Enhancements in oxidative capacity and oxygen diffusion capacity of skeletal muscle may be necessary to compensate for insufficient oxygen supply in tissues. Hypoxic conditions can cause a switch from aerobic metabolism to anaerobic metabolism. Due to previous research of Graham Scott and colleagues on “Adaptive Modifications of Muscle Phenotype in High-Altitude Deer Mice” and the SMack Lab at Arizona State University, the question of how low atmospheric oxygen levels affects the enzymatic activity in the gastrocnemius muscle of Gelada Monkeys compared to Rhesus Macaque Monkeys was researched. Lactate Dehydrogenase (LDH) activity was measured in the gastrocnemius tissue of 6 Gelada Monkeys (highland) and 6 Rhesus Macaque monkeys (lowland). LDH was expected to be greater in Gelada tissue samples due to heightened anaerobic metabolism in the presence of limited available oxygen in high altitude environments. Results showed higher LDH in Rhesus Macaque samples compared to Gelada samples, but this difference was not statistically significant. Despite nonsignificant data, this experiment is insightful into the effects of Hypoxic adaptation in skeletal muscle enzymatic activity in primates.