The Effects Of Selenium Combined With Antitumor Drugs

Background:Breast cancer is a common malignant tumor among women, which morbidity andmortality are rising. The traditional surgical ablation cannot bring satisfactory survival rates,so the vast majority of patients still die of tumor recurrence and metastasis. Andchemotherapy is approved to be the available treatment in tumor, but the efficient of thechemotherapy treatment is not satisfactory. Breast cancer, of which biological processes isresult from the gene changes, is closely related to the occurrence and development ofcancer gene transient expression, and tumor gene inactivation. Therefore, the treatment ofbreast cancer based on gene targeting with new highly selective is an emergency toeffective control of breast cancer. Selenium (selenium, Se) is an essential element for thephysiological activities of the human body, as early as thirty years ago, some scholars hadconnected the risk of cancer to selenium together, but until recently, after years of research,Combs GF Jr thinks that selenium is an important new element to anticancer. Meanwhile,the NPC(The nutritional Prevention of Cancer) in the USA further confirms the seleniumhas anticancer activity in large clinical studies. The selenium anticancer activity is achievedby selenium and protein related conjugates. Selenium binding protein1(Seleium BindingProtein1SBP1) is a kind of selenium binding protein. Coding gene is located in1q21-22.The molecular weight is56KD, whose mRNA sequence (Gene bank seat number:NM-003944) is composed of1721nucleotides encoding640amino acids. Research showsthat prevention and anticancer effects of selenium is acted by the mediated bySBP1Selenium binding protein1(Seleium Binding Protein1SBP1) is a kind of selenium binding protein, coding gene is located in1q21-22, the molecular weight is56KD, itsmRNA sequence (Gene bank seat number: NM-003944) is composed of1721nucleotidesencoding640amino acids, research shows that prevention and anticancer effects ofselenium is acted by the mediated by SBP1. The selenium targeting SBP1gene expressionis activated to exert its anti-cancer effects. Studies have shown that selenium inhibit tumorrole of selenium in the form of preparation, the experiments show that the tumor suppressorrole of sodium selenite strongest.This study aims to probe the treatment effect of breast cancer through experiments ofvitro and animal model of nude mice induced by sodium selenite on SBP1(Na2SeO3) and5-fluorouracil chemotherapy drugs commonly used (5-Florouracil,5-Fu). Compared withthe use of Na2SeO3or5-Fu, it is analyzed that the feasibility and validity of breast cancermethod combining with element selenium and chemotherapy drugs in clinical anti-tumorand some molecular mechanism.Methods:1. Cultivation of breast cancer cell line MCF-71in vitro, were randomly divided into4groups, control group,5-FU, Na2SeO3and5-FU+Na2SeO3. According to our previouswork confirmed, combined with the literature5-Fu:10ug/ml; Na2SeO3:8umol/L and twodrug combination48h inhibited the MCF-7breast cancer cell survival rate, there wasstatistical significance. We select the dosage of the drug as a treatment concentrationexperiment experiment.it’s used the methods of MTT and clone formation assay cellgrowth; then Annexin V-FITC/PI double staining flow cytometry detects cell cycle.2. Construct the MCF-7tumor-bearing BALB/c-nude mice model about breast cancer,a week after inoculation of tumor cells, nude mice subcutaneous tumor nodules appearright gluteal region. The diameter of tumor grew to0.5cm, were randomly divided into4groups, each group has6mice, then the treatment starts, group I: control group, salineinjection (NS); group Ⅱ: injection of5-Fu (15mg/kg); group III: Na2SeO3(6mg/kg);group IV:5-Fu (15mg/kg)+Na2SeO3(6mg/kg) joint suitable for injection; above all byintraperitoneal injection of drugs for treatment of growth curve, calculate the tumorvolume and render tumor growth curve, weight and calculate the inhibition rate of tumor specimens at the end of treatment.3. Continuously observe groups for15days and then killed the BALB/c-nude mice.The routine paraffin embedding, slicing, HE staining was observed in tumor tissues.4. Remove paraffin preservation, conventional dewaxing to water, then SABCimmunohistochemical staining to detect the expression of apoptosis related protein,Caspase-3and Bcl-2.5. Use western blot technique to detect the expression value of Caspase-3, Bax andBcl-2in experimental groupsResults:1. Experiment in vitro showed that5-Fu and Na2SeO3could inhibit the growth ofMCF-7cells, the combined application of5-Fu and Na2SeO3was more sensitive thansingle application, cell survival rate decreased significantly, which showed that5-Fu andNa2SeO3combination could play a synergistic inhibitory effect on MCF-7cells.2. In vivo experimental results results, subcutaneous tumor nodules of BALB/c-nudemice appeared in right buttoct after inoculated the tumor cells in about one week. When thetumorigenicity up to0.5cm size, the BALB/c-nude mice would be started to cure andcalculated the tumor volume and draw tumor growing curve. At the end of treatment,weighing tumor specimens and calculated the tumor inhibitory rate: group Ⅰ:(0.469±0.072); group Ⅱ:(0.204±0.02556.44%); group:(0.244±0.01348.05%); group IV:(0.170±0.02163.74%); all animal subcutaneous transplantation tumor are round, ovaland irregular nodular, with poor activity. After the experiment, based on routine paraffinsection, HE staining, morphological observation. The results showed that in tumor tissuesof all subcutaneous cells were irregular change, cell sizes were different, and most cellwere active growing and display in mitotic phase.3. Immunohistochemistry results showed that under light microscope condition,allpositive cells were brown or tan. Caspase-3was mainly expressed in the cancer cellnucleus, but cytoplasm was weakly positive. The average optical density combinedexpression of group Caspase-3was obviously stronger than the other three groups, therewere significant differences; expression intensity of NS group was significantly weaker than the rest three groups, there was significant difference; there was no significantdifference between Na2SeO3and5-Fu. The Bcl-2positive substance was mainly expressedin the cytoplasm and nuclear membrane, nuclear weakly positive expression, thecombination group the expression of the average optical density significantly weaker thanthe other three groups, there were significant differences; expression intensity of NS wasstronger than in the rest of the three groups, there was significant difference; there was nosignificant difference between Na2SeO3and5-Fu.4. Western blot showed that the expression of the combination group Caspase-3andBax protein content was much higher than the other three groups; expression value of NSgroup was significantly less than the other three groups, but there was no significantdifference between Na2SeO3and5-Fu. Combination group, the protein expression of Bcl-2was lower than the other three groups, there were significant differences; expression of NSgroup was significantly higher than other three groups, there was significant difference;there was no significant difference between Na2SeO3and5-Fu. Expression of thecombination group and the Na2SeO3group of SBP1protein was higher than that in NS and5-Fu group, but no significant differences between the two groups. Also, there is nosignificant difference between NS and5-Fu group.Conclusions:1. Both Na2SeO3and5-Fu, co-administration of which can generate significantsynergies, kill MCF-7cells in vitro. Also, co-administration can produce apparentapoptosis.2. The application of MCF-7cells can be successfully established transplantationtumor of breast cancer in nude mice animal models, which will be provided reference toolsfor the human breast cancer treatment.3. The combination with Na2SeO3and5-Fu plays a joint inhibitory action on breastcancer cell. This inhibition is related to apoptosis regulatory proteins, which plays a role byenhancing the expression of Caspase-3and Bax, and inhibiting the expression of Bcl-2.4. The combination therapy has a satisfactory anti-tumor effect in vivo, which showsinhibition of tumor growth and induce apoptosis of tumor cells in nude mice. 5. The combination with sodium selenite and fluorouracil may effectively reduce theside effects of the chemotherapy drugs.6. The combination therapy of Sodium selenite and fluorouracil in the treatment ofanti-breast cancer is significantly superior than single drug effects. It provides anexperimental basis for selenium in the research of anti-tumor.