Letrozole-induced functional changes in carcinoma-associated fibroblasts and their influence on breast cancer cell biology
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Accumulating evidence suggests that carcinoma-associated fibroblasts (CAFs) influence the efficacy of endocrine therapy. Aromatase inhibitors inhibit the growth of breast tumors by inhibiting the synthesis of estrogen. However, it remains unknown whether the aromatase inhibitor letrozole has an additional impact on CAFs, which further influence the efficacy of endocrine therapy. Primary CAFs were isolated from primary estrogen receptor-positive human breast tumors. Estrogen-deprived culture medium was used to exclude the influence of steroids. In co-culture, primary cultured CAFs increased MCF7 cell adhesion, invasion, migration and proliferation, and letrozole treatment inhibited these increases, except for the increase in proliferation. In total, 258 up-regulated genes and 47 down-regulated genes with an absolute fold change >2 were identified in CAFs co-cultured with MCF7 cell after letrozole treatment. One up-regulated genes (POSTN) and seven down-regulated genes (CCL2, CCL5, CXCL1, IL-8, CXCL5, LEP and NGF) were further validated by real-time PCR. The changes in CCL2 and CXCL1 expression were further confirmed using an automated microscopic imaging-based, high content analysis platform. Although the results need further functional validation, this study is the first to describe the differential tumor-promoting phenotype of CAFs induced by letrozole and the associated gene expression alterations. Most importantly, our data revealed that down-regulation of several secreted factors (CCL2, CCL5, CXCL1 etc.) in CAFs might be partially responsible for the efficacy of letrozole.
KeywordsBreast cancer Carcinoma-associated fibroblasts Endocrine therapy Aromatase inhibitors
This work was supported by the National Natural Science Foundation of China (No. 81172517), the Specialized Research Fund for the Doctoral Program of Higher Education of China (No. 20111107110001), the China Medical Fund (No. 313.2233) and the Beijing Municipal Health System Academic Leaders of High-Level Health Personnel Program (No. 2011-2-28).
H Kang designed experiments, provided critical reagents and experimental expertise and supervised the study; KF Li designed experiments, performed the experiments, made the figures and wrote the manuscript; YJ Wang and T Hai collected the tumor tissues; and HC Sun and GH Rong performed some of the experiments.
Compliance with ethical standards
Conflict of interest
The authors declare that there are no competing financial interests.
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