Role And Mechanism For PTP1B/STAT3 Signal Pathway In Endoplasmic Reticulum Stress-Induced Expression Of CCL5 In Breast Cancer Cells

Background Breast cancer is one of the most common female cancers in the world. The poor prognosis of patients with breast cancer is related to tumor metastasis. Metastasis, as a result of several sequential steps, represents a highly organized and organ-selective process. In recent years, the incidence of breast cancer is significantly raised. Now it is one of malignant tumors threaten the healthy and life of women. The recurrence and metastasis of breast cancer is main reason which caused the patients' death. CCL5,which has a closely relationship with metastasis and recurrence of breast cancer, is regarded have a positively correlated with the severity of breast cancer. Previous studies showed that the main mechanism for generating CCL5 is endoplasmic reticulum stress(ER stress) can stimulate the expression of U-STAT3. But the mechanism of over expression U-STAT3 is still lack of adequate understanding. PTP1B in breast cancer is also highly expressed,the main function of which is promote the tyrosine phosphorylation dephosphorylation. The phosphorylation site of activation of STAT3 is Tyr705, which may be the substrate of PTP1B. It suggests that there may exist a signaling pathway of PTP1B/STAT3 in breast cancer activated by endoplasmic reticulum stress. We will explore the function of PTP1B on the pathway for generate CCL5 in this article.Methods 1. Use RT-PCR and Western blot to detect the expression of CHOP in human breast cancer. Use Western blot to detect the changement of CHOP when treated with Tunicamycin of Omg/L,2.5mg/L,5mg/L,10mg/L,20mg/L. Use Western blot to detect the changement of CHOP when treated with Tunicamycin after 0h,6h,12h,18h,24h. Use Western blot to detect the changement of CCL5 when treated with Tunicamycin and 4-PBA respectively. Calculate the proliferation rate of MCF-7 by the MTT assay.2. Use RT-PCR and Western blot to detect the expression of PTP1B,U-STAT3 and CCL5 in human breast cancer; Detect the enzyme activity of PTP1B in human breast cancer and MCF-7 cell line; Use Western blot to detect the changement of PTP1B,U-STAT3.CCL5 when treated with Tunicamycin and CinnGEL 2Me respectively. Use gene silence to reduce the expression of PTPlB,and then detect the expression of P-STAT3,USTAT3 and CCL5.Calculate the proliferation rate of MCF-7 by the MTT assay.Results 1. The expression of CHOP is much higher in human breast cancer tissue than normal tissue. The results demonstrate that Tunicamycin induces the expression of CHOP in a dose and gradient-dependent manner, with maximal expression observed with a concentration of 10mg/L. After treated with Tunicamycin for a ladder time, the expression of CHOP was markedly increased. When MCF-7 cell is stimulated by Tunicamycin, and the expression of CCL5 is also increased. When MCF-7 cell is stimulated by 4-PBA, and the expression of CCL5 is also decreased. And we also found that the proliferation rate of MCF-7 increased when the cells were stimulated by Tunicamycin,and decreased the cells were inhibited by 4-PBA.2. The expression and enzyme activity of PTP1B is much higher in human breast cancer tissue than normal tissue, and it also exist when MCF-7 cell is stimulated by endoplasmic reticulum stress,and the expression of U-STAT3 and CCL5 is also increased. When using the PTP1B inhibitors, the expression of U-STAT3 and CCL5 will decreased.The expression of U-STAT3 and CCL5 decreased and the expression of P-STAT3 increased will under the condition that the geneof PTP1B was silenced. And we also found that the proliferation rate of MCF-7 increased when PTP1B was activated,and decreased when PTP1B was inhibited. Scratch test also proved PTP1B has positive correlation with cellular invasion.Conclusion Our results indicate that endoplasmic reticulum stress can stimulate the expression of PTP1B/STAT3 signal path in human breast cancer, resulting in the surprising high expression of U-STAT3. However, the U-STAT3 may combite with the U-NF-κB, resulting in the high expression of CCL5. Under the endoplasmic reticulum stress, PTP1B/STAT3 pathway is an important channels in over expression of CCL5 under endoplasmic reticulum stress.