Cuban Brown Propolis Interferes in the Crosstalk between Colorectal Cancer Cells and M2 Macrophages

Abstract

<jats:p>Tumor-associated macrophages (TAMs), primarily the M2 phenotype, are involved in the progression and metastasis of colorectal cancer (CRC). Cuban brown propolis (Cp) and its main component Nemorosone (Nem) displays an antiproliferative effect on different cancer cells, including CRC cell lines. However, whether Cp and Nem could exploit its effect on CRC cells by targeting their relationship with TAMs remains to be elucidated. In this study, we differentiated the human monocytic THP-1 cells to M2 macrophages and confirmed this transition by immunofluorescence (IF) staining, qRT-PCR and zymography. An MTT assay was performed to determine the effect of Cp and Nem on the viability of CRC HT-29 cells co-cultured with M2 macrophages. Furthermore, the migration and invasion abilities of HT-29 cells were determined by Transwell assays and the expression levels of epithelial–mesenchymal transition (EMT) markers were analyzed by IF staining. We demonstrated that Cp and Nem reduced the viability of M2 macrophages and, accordingly, the activity of the MMP-9 metalloprotein. Moreover, we demonstrated that M2 macrophages produce soluble factors that positively regulate HT-29 cell growth, migration and invasion. These M2-mediated effects were counteracted by Cp and Nem treatments, which also played a role in regulating the expression of the EMT markers E-cadherin and vimentin. Taken together, our results indicate that Nem contained in Cp interferes in the crosstalk between CRC cells and TAMs, by targeting M2 macrophages.</jats:p>

Anticancer Activity of Propolis and Its Compounds

“…Some of the published research papers only state the effect of propolis and its components on the inhibition of the proliferation process without penetrating the molecular mechanism [ 9 , 16 , 55 , 56 , 57 , 58 , 59 , 60 , 61 , 62 , 63 , 64 , 65 ]. Nevertheless, there are also research results that bring these mechanisms closer.…”

“…Treatment of HepG2 (hepatocellular carcinoma cells) with supernatant of human monocytic THP-1 cells and HT-29 (colorectal adenocarcinoma cells) with supernatant of M2-like macrophages or co-culturing both types of cells stimulated migration and invasion of studied cancer cells. Interestingly, nemorosone and/or Cubian brown propolis extract treatments decreased migration and invasion, both in the presence and absence of conditioned medium or M2-like macrophages [ 46 , 64 ]. Cuban propolis and nemorosene treated M2-like macrophages were characterized by reduced mRNA levels of proinflammatory factors, such as IL-8, IL-10, CCL2 and VEGF.…”

“…Additionally, the treatment with Nem and Cuban propolis significantly downregulated the activity of MMP-9, which is released by M2-like macrophages. MMP-9 contributes to cancer cell infiltration and invasiveness [ 64 ].…”

Experimental Evidence for Therapeutic Potentials of Propolis

“…Furthermore, multimodal mechanisms of action for different propolis types and their components have been reported. These include immunomodulation and antitumor resistance [ 70 , 146 , 147 ], activation of apoptotic signaling [ 80 , 83 , 143 , 148 , 149 , 150 ], inhibition of cancer cell migration and invasion [ 143 , 151 , 152 , 153 ] and drug resistance [ 154 , 155 ].…”

“…CAPE was shown to inhibit 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced tumors and therefore proposed as an anticancer drug for the treatment of gastric carcinoma, hepatoma and colorectal carcinoma [ 138 , 158 ]. The studies on a wide range of human cancer cell lines have reported that CAPE causes cytotoxicity to most with IC50 of 10–20 μM; some cell lines showed high sensitivity (IC50 1–5 μM), whereas some others showed low sensitivity (IC50 70–100 μM) [ 143 , 150 , 151 , 152 ].…”