Tumor-associated macrophage-derived CCL5 promotes chemotherapy resistance and metastasis in prostatic cancer

The crosstalk between tumor microenvironment and cancer cells is emerging as a critical determinant in tumor progression. However, the underlying mechanism of tumor microenvironment-induced cancer development remains controversial. Here, our study provides evidence to suggest that tumor-associated macrophage (TAM) enrichment is found in chemo-resistant prostatic tumor tissues. Those TAMs are demonstrated to promote chemo-resistance and distant metastasis in prostatic cancer through secretion of CCL5. Mechanistically, TAM co-culture or additional CCL5 can mediate the STAT3-dependent epithelial-mesenchymal transition (EMT) process, resulting in distant metastasis in prostatic cancer. Meanwhile, activation of STAT3 induced by CCL5 can mediate up-regulation of the transcription factor Nanog, leading to drug resistance. In vivo study further demonstrated that blockade of STAT3 signals significantly reverses chemo-resistance and suppresses lung metastasis in colorectal tumor-bearing mice, suggesting a novel strategy for clinical prostatic cancer treatment. This article is protected by copyright. All rights reserved.