MTH1 Expression In Breast Cancer And Inhibition Of MTH1 In The Treatment Of Different Subtypes Of Breast Cancer Exploratory Study

PartlThe Expression of MTH1 in Human Breast Cancer TissuesPurpose:To investigate the expression of MTH1 protein and mRNA in the human breast cancer tissues. To analyze the association of MTH1 expression and different clinicopathological characteristics such as molecular subtype, age, tumor size and lymph node status.Methods:30 cases of invasive breast cancer tissues(10 of each subtype from Luminal、Her-2 over-expression、Basal-like) and 10 cases of non-cancer breast tissues were tested to evaluate the expression of MTH1 protein by immunohistochemistry.30 pare of invasive breast cancer tissues and non-cancer breast tissues (10 of each subtype from Luminal、Her-2 over-expression、Basal-like) were tested to evaluate the expression of MTH1 mRNA by real time quantitative PCR.Resutls:The invasive breast cancer tissues, as compared to the non-cancer breast tissues, showed a significant higher middle/strong positive rate of MTH1 protein (93.3% vs.10.0%%, P<0.001). The invasive breast cancer tissues also showed a significant higher score in quantitative PCR which was 3.15(± 1.67) times of the score that the non-cancer breast tissues showed (P=0.003). There were no significant differences of MTH1 protein and mRNA expression in different clinicopathological characteristics such as molecular subtype, age, tumor size and lymph node status. (P>0.05)。Conclusion:The expression of MTH1 in human breast cancer tissues is significantly higher than that of non-cancer breast tissues. The high expression does not differed with different clinicopathological characteristics such as molecular subtype, age, tumor size and lymph node status.Part2MTH1 inhibition in different breast cancer cell lines in vitroPurpose:To investigate the expression of MTH1 protein in MCF-7、MDA-MB-231 and MDA-MB-453 breast cancer cell lines. To investigate the growth inhibition in different breast cancer cell lines with the treatment of MTH1 inhibitor.Methods:Western blot was applied to test the expression of MTH1 protein in different breast cancer cell lines. CCK-8 kit was applied to test the proliferation of different breast cancer cell lines with the treatment of MTH1 inhibitor. Clonogenic outgrowth assay was applied to test the clonogenic survival rate of different breast cancer cell lines with the treatment of MTH1 inhibitor.Resutls:MTH1 protein were highly expressed in different breast cancer cell lines. CCK-8 test showed that with the increasing concentrations of MTH1 inhibitor, the viability of breast cancer cell lines decreased. The IC50 value of CCK-8 test was observed in the MCF-7 and MDA-MB-231 cell lines (11.91umol/l and 12.86umol/l respectively) within the administered concentration but it was not observed in the MDA-MB-453 cell line. Clonogenic outgrowth assay showed that clonogenic survival rate decreased with the increasing concentrations of MTH1 inhibitor. The IC50 value of clonogenic outgrowth assay was observed within the admininstered concentration in all the three breast cancer cell lines (MCF-7 cell line 9.78umol/l, MDA-MB-231 cell line 6.96umol/l and MDA-MB-453 cell line 8.97umol/l).Conclusion:In Vitro, MTH1 inhibition significantly induces the supression of the growth in MCF-7 breast cancer cell line(Luminal subtype)、MDA-MB-231 breast cancer cell line(Basal-like subtype) and MDA-MB-453 breast cancer cell line(Her-2 over-expression subtype).Part3MTH1 inhibition in different breast cancer cell lines in vivoPurpose:To investigate the inhibition efficacy and drug safety of MTH1 inhibitor when it is administered to the nude mice xenograft tumor models of MCF-7、MDA-MB-231 and MDA-MB-453 human breast cancer cell lines.Methods:Different breast cancer cell lines were transplanted into immune-deficient nude mice to establish the human xenograft tumor models and control group. Tumor volume curves、body weight curves、blood tests were made to investigate the efficacy and safety of MTH1 inhibitor.Resutls:The nude mice xenograft tumor models of MCF-7、MDA-MB-231 和 MDA-MB-453 were set up successfully. The final tumor volumes were significant different between the treatment groups and control groups: MCF-7 (treatment vs. control,60.1mm3 vs.820.8mm3, P<0.05), MDA-MB-231 (treatment vs. control,30.1mm3 vs.313.5mm3, P<0.05), MDA-MB-453 (treatment vs. control,0mm3 vs.5.2mm3, P<0.05). There were no significant differences between the pre-treatment body weights and the post-treatment body weights in the treatment group:MCF-7(post vs. pre, 16.81g vs.17.44g, P>0.05), MDA-MB-231 (post vs. pre,17.42g vs.17.68g, P>0.05), MDA-MB-453 (post vs. pre,17.23g vs.17.69g, P>0.05). The body weight gain in the drug-only mice is 0.73(±0.34)g, which is significant lower than the value of 2.26 (±0.29) g in the normal mice. (P<0.05). There were no significant differences between the normal mice and drug-only mice in the blood test results such as blood routine、liver and kidney function (P>0.05).Conclusion:In nude mice xenograft tumor models, MTH1 inhibition significantly inhibits the tumor growth in MCF-7 breast cancer cell line(Luminal subtype)、MDA-MB-231 breast cancer cell line(Basal-like subtype) and MDA-MB-453 breast cancer cell line(Her-2 over-expression subtype). Short-time MTH1 inhibition in nude mice is safe.