Lentivirus-mediated RNA interference targeting the ObR gene in human breast cancer MCF-7 cells in a nude mouse xenograft model

Background There is a significant association between obesity and breast cancer, which is possibly due to the expression of leptin. Therefore, it is important to clarify the role of leptin/ObR （leptin receptor） signaling during the progression of human breast cancer. Methods Nude mice with xenografts of MCF-7 human breast cancer cells were administered recombinant human leptin subcutaneous via injection around the tumor site. Mice in the experimental group were intratumorally injected with ObR-RNAi-lentivirus, while negative control group mice were injected with the same dose of negative-lentivirus. Tumor size was blindly measured every other day, and mRNA and protein expression levels of ObR, estrogen receptor a （ERa）, and vascular endothelial growth factor （VEGF） for each group were determined.Results Knockdown of ObR-treated xenografted nude mice with a high leptin microenvironment was successfully established. Local injection of ObR-RNAi-lentivirus significantly suppressed the established tumor growth in nude mice. ObR level was significantly lower in the experimental group than in the negative control group, while the amounts of ERα and VEGF expression were significantly lower in the leptin group than in the control group （P 〈0.01 for all）.Conclusions Inhibition of leptin/ObR signaling is essential to breast cancer proliferation and possible crosstalk between ObR and ERa, and VEGF, and may lead to novel therapeutic treatments aiming at targeting ObR in breast cancers.

Effects of exogenous human leptin on heat shock protein 70 expression in MCF-7 breast cancer cells and breast carcinoma of nude mice xenograft model

Background It is important to identify the multiple sites of leptin activity in obese women with breast cancer.In this study,we examined the effect of exogenous human leptin on heat shock protein 70 （HSP70） expression in MCF-7 human breast cancer cells and in a breast carcinoma xenograft model of nude mice.Methods We cultured MCF-7 human breast cancer cells and established nude mice bearing xenograffs of these cells,and randomly divided them into experimental and control groups.The experimental group was treated with human leptin,while the control group was treated with the same volume of normal saline.A real-time reverse transcriptase-polymerase chain reaction （RT-PCR） assay was developed to quantify the mRNA expression of HSP70 in the MCF-7 human breast cancer cells and in tumor tissues.Western blotting analysis was applied to quantify the protein expression of HSP70 in the MCF-7 cells.Immunohistochemical staining was done to assess the positive rate of HSP70 expression in the tumor tissues.Results Leptin activated HSP70 in a dose-dependent manner in vitro：leptin upregulated significantly the expression of HSP70 at mRNA and protein levels in MCF-7 human breast cancer cells （P 〈0.001）.There was no significant difference in expression of HSP70 mRNA in the implanted tumors between the leptin-treated group and the control group （P〉0.05）.Immunohistochemical staining revealed no significant difference in tumor HSP70 expression between the leptin-treated group and the control group （P〉0.05）.Conclusions A nude mouse xenograft model can be safely and efficiently treated with human leptin by subcutaneous injections around the tumor.HSP70 may be target of leptin in breast cancer.Leptin can significantly upregulate the expression of HSP70 in a dose-dependent manner in vitro.