Tumor-associated macrophages in human breast cancer produce new monocyte attracting and pro-angiogenic factor YKL-39 indicative for increased metastasis after neoadjuvant chemotherapy

Abstract

In breast cancer, the tumor microenvironment plays a critical role in the tumor progression and responses to therapy. Tumor-associated macrophages (TAMs) are major innate immune cells in tumor microenvironment that regulate intratumoral immunity and angiogenesis by secretion of cytokines, growth factors as well as chitinase-like proteins (CLPs), that combine properties of cytokines and growth factors. YKL-39 is a chitinase-like protein found in human and absent in rodents, and its expression in TAMs and role in breast cancer progression was not studied to date. Here for the first time we demonstrate that YKL-39 is expressed on TAMs, predominantly positive for stabilin-1, but not by malignant cells or other stromal cells in human breast cancer. TGF-beta in combination with IL-4, but not IL-4 alone was responsible of the stimulation of the production of YKL-39 in human primary macrophages. Mechanistically, stabilin-1 directly interacted with YKL-39 and acted as sorting receptor for targeting YKL-39 into the secretory pathway. Functionally, purified YKL-39 acted as a strong chemotactic factor for primary human monocytes, and induced angiogenesis in vitro. Elevated levels of YKL-39 expression in tumors after neoadjuvant chemotherapy (NAC) were predictive for increased risk of distant metastasis and for poor response to NAC in patients with nonspecific invasive breast carcinoma. Our findings suggest YKL-39 as a novel therapeutic target, and blocking of its activity can be combined with NAC in order to reduce the risk of metastasis in breast cancer patients.

Chitinase-Like Proteins as Promising Markers in Cancer Patients

“…The angiogenesis assay showed that recombinant YKL-39 induced tube formation of HUVEC cells 6 times higher than that observed in the negative control group, and this induction was more than 60% of positive control. The chemotactic effect of YKL-39 on primary monocytes was approximately 2 times higher after 1 h and more than 5 times higher after 3 h compared to control, and this effect was comparable with the effect of MCP-1/CCL2 chemokines [25].…”

“…In our study we showed that the elevated levels of YKL-39 expression in tumors after neoadjuvant chemotherapy (NAC) were associated with increased risk of distant metastasis and poor response to NAC in patients with nonspecific invasive breast carcinoma [25]. Moreover, in the study of gene expression of M2 macrophage markers (YKL-39 and CCL18) we found that in breast cancer patients, who received anthracycline-containing NAC, the absence of clinical response was associated with the presence of M2+ macrophage phenotype (YKL-39-CCL18 + or YKL-39 + CCL18-) [38].…”

“…Analysis of biological functions of YKL-39 demonstrated that it is unique that CLP combines monocyte attracting and pro-angiogenic activities, which essential for tumor progression [25]. The angiogenesis assay showed that recombinant YKL-39 induced tube formation of HUVEC cells 6 times higher than that observed in the negative control group, and this induction was more than 60% of positive control.…”

“…For YKL-39, no specific effects of IFNgamma, IL-4 or dexamethasone were detected, but YKL-39 was upregulated in macrophages differentiated in the presence of IL-4+TGF-beta, but not IL-4 alone [25].…”

“…Endogenous YKL-39 was found in the trans-Golgi network, where it was partially co-localized with stabilin-1. Using GST pulldown assay we showed that stabilin-1 can act as an intracellular sorting receptor for YKL-39 [25].…”