The Effect Of Lapatinib On Breast Cancer Cells Proliferation By Influencing PKM2 Expression

Objective:To study the correlation between M2 type pyruvate kinase and epidermal growth factor receptor expression; to study the effect of Lapatinib on PKM2 expression and proliferation in breast cancer cells; to study the effect of PKM2 on transcription factor Stat3 and p Stat3.Methods:1. Cancer tissues and adjacent tissues of 82 cases breast cancer patients were chosen. PKM2 expression of cancer tissues and adjacent tissues was detected by Immunohistochemistry and tissue protein electrophoresis. The correlation of PKM2 with EGFR and PKM2 with HER2 were analysed by chi-square test.2. MDA-MB-231 and SK-BR-3 breast cancer cell lines were chosen. PKM2, EGFR and HER2 expression was analysed by Western blot. MDA-MB-231 in which EGFR was high expressed was chosen. Si RNA EGFR knock down methods were experimented to detect correlation of EGFR and PKM2. SK-BR-3 in which HER2 was high expressed was chosen. Si RNA HER2 knock down methods were experimented to detect correlation of HER2 and PKM2.3. MDA-MB-231 and SK-BR-3 breast cancer cell lines were chosen. Effect of Lapatinib on PKM2 was analysed by Western blot and RT-PCR. Each cell lines were divided into two groups: Lapatinib treatment group and DMSO treatment group. Every group was stimulated with EGF. After stimulating 24 h and 48 h, PKM2 and PKM2(Tyr(P)-105) expression in every group was detected by Western blot. 120 cases breast cancer patients whose tissues were detected by immunohistochemistry indicating HER2(+++) or detected by FISH suggesting HER2 gene amplification were chosen. The patients were divided into two groups: Lapatinib adjuvant chemotherapy group and chemotherapy group. Plasmatic PKM2 level was detected by ELISA to analyse effect of Lapatinib on PKM2.4. MDA-MB-231 and SK-BR-3 breast cancer cell lines were divided into three groups: Lapatinib treatment group, DMSO treatment group, untreated group. Stable breast cancer cell lines which were over expressing PKM2 were established. Cells proliferation was detected by CCK8 experiments to determinate effect of PKM2 on cells proliferation in breast cancer cell lines.5. Si RNA PKM2 knock down was experimentized in MDA-MB-231 and SK-BR-3 breast cancer cell lines, to compare Stat3 and Stat3(Tyr(P)-705) expression in knock down group with control group.Results:1. PKM2 expression is increased in breast cancer tissues compared with adjacent normal tissues. There has a positive relationship between PKM2 and HER2 expressions in breast cancer tissues. There has a positive relationship between PKM2 and EGFR expressions in breast cancer tissues.2. PKM2 expression is significantly decreased in Lapatinib treatment group compared with DMSO treatment.3. Plasmatic PKM2 level in breast cancer patients who were treated with Lapatinib adjuvant chemotherapy is signigicantly decreased compared with chemotherapy group.4. Lapatinib treatment group cells grew significantly slower than control group. PKM2 over-expression group cells grew significantly faster than control group.5. PKM2 regulates Stat3 and Stat3(Tyr(P)-705) expression in breast cancer cell lines. The inhibition of Lapatinib to PKM2 induces Stat3 and phosphorylated Stat3 level reduction.Conclusions:1. PKM2 expression is upregulated in breast cancer tissues and positively correlates with EGFR and HER2 expressions in breast cancer tissues.2. Lapatinib inhibites PKM2 expression in breast cancer.3. Lapatinib inhibits breast cancer cells proliferation by influencing PKM2 expression.4. Lapatinib inhibits breast cancer cells proliferation by influencing PKM2 expression which results in Stat3 and phosphorylated Stat3 level reduction.