Sodium Selenite Induces Apoptosis In Colorectal Cancer SW480 Cells Via ROS/JNK Nuclear Transcription Factor And Cyclin

The essential trace element, selenium, is of fundamental importance to human health and the prevention of tumors. Mounting epidemiological and clinical evidence indicate that ultra doses of selenium could effectively induce tumor cells apoptosis,including prostate cancer, bladder cancer, thyroid cancer, esophageal cancer, liver cancer, colon cancer, lung cancer and colorectal cancer. Exploring the molecular mechanisms underlying the anti-cancer effect of selenium became a hot spot of current research. A growing number of people are diagnosed with colorectal cancer in China and the cure rate is very low. But there are all some limitations in the current treatment plan. Therefore, making a thorough inquiry into the molecular mechanisms of selenium induced colorectal cancer cell apoptosis would be of great significance for the development of drugs containing selenium and the treatment of colorectal cancer with new ideas and theoretical basis.Our previous data show that supranutritional doses of selenite can inhibit proliferation and induce apoptosis in multiple colorectal cancer cell lines, and in xenograft mouse model, sodium selenite can inhibit tumor growth and induce apoptosis of tumor tissue. But the types of signaling pathways involved and the detailed mechanism is unclear.In this experiment, we used the colorectal cancer cell SW480 and sodium selenite as the research object, to studied the intracellular signaling molecules and regulatory proteins which have played a role in the process of colorectal cancer cell apoptosis that induced by sodium selenite. SW480 cells were treated with supranutritional dose of selenite (10μmol/L) for different times, the expression of bcl-2 and cleaved parp,cleaved caspase-3 were detected by western blot, we found decreased protein expression on bcl-2, the cutting level of cleaved parp and cleaved caspase-3 had risen, showed that sodium selenite did induced the apoptosis of SW480 cells, and incubated SW480 cells with ROS detection probe and continuous real-time monitoring, the results showed that the ROS content increased over time. It indicated that in the SW480 cells treated with sodium selenite, there was a certain relevance between the apoptosis and the intracellular ROS that we unknown.In order to verified the above speculation, SW480 cells were pretreated with MnTMPyP for 1.5 h, followed by selenite or PBS solution treatment for 24 h, total lysates were prepared and subjected to immunoblot analysis,apoptosis related proteins including cleaved parp and bcl-2 were detectd, we found the change that caused by sodium selenite about bcl-2 and cleaved parp, cleaved caspase-3 were all reversed, the result of flow cytometry assay did the same. There were not much difference between the cells pretreated with MnTMPyP and the double negative control group, it showed that the direct factor induced apoptosis in SW480 cells was ROS, rather than sodium selenite. In order to further explore which proteins have involved in the regulation of ROS on the apoptosis of colorectal cancer, SW480 cells were treated with supranutritional dose of selenite (10μmol/L) for different times, blot western detection found some signal transduction proteins involved in this process, including P-JNK, P-ATF-2, c-myc, c-jun, c-fos, cyclinD1 and cyclinA2 were all inhibitied, these changes lead to apoptosis. After this experiment, we pretreated SW480 Cells with MnTMPyP for 1.5 h, followed by selenite or PBS solution treatment for 24 h, total lysates were prepared and subjected to immunoblot analysis. The signal transduction proteins which have changed in the previous experiment were detectd. We also found the change that caused by sodium selenite about P-JNK, P-ATF-2, c-myc, c-jun, c-fos, cyclinD1 and cyclinA2 were all reversed. These results have proved the core role of ROS in the process of sodium selenite induced colon cancer cell apoptosis from two levels, cytology and protein molecules.The above findings have provided an important theoretical and experimental basis for the screening of molecular targets about sodium selenite specific killing of colorectal cancer cells, also for the prevention and treatment of selenium on the role of cancer.