Background:  The presence of immune infiltrate in tumor sites has been thought to represent an immune response against the tumor. However, new evidences indicate that these immune cells may be supporting tumor growth rather than inhibiting it. Previously, we described a sub-group of epithelial ovarian cancer (EOC) cells that express TLR-4 and MyD88 and produce several cytokines and chemokines. We hypothesize that EOC cells could recruit immune cells and induce their differentiation toward tumor-supporting immune cells. The objective of this study is to determine the consequence of an activated TLR-4-MyD88 signaling pathway on migration and differentiation of the monocyte-like THP-1 cells.

Materials and Methods:  R182 (MyD88-positive) and CP70 (MyD88-negative) EOC cells were incubated in the presence or absence of 10 μg/mL LPS for 48 hr and cell-free conditioned media (CM) was prepared. THP-1 cells were incubated in 50% CM for 24 hr. Cytokine profile (IL-6, IL-8, IL-10, IL-12, MIF, MCP-1, GROα, RANTES, IFNγ, and TNFα) of cell-free supernatants and THP-1 lysates was characterized using Beadlyte Human Multicytokine kit and xMAP technology. Migration assay was performed using QCM 24-well Colorimetric Cell Migration Assay kit.

Results:  THP-1 cells migrate towards R182- and CP70-CM equally. However, enhanced migration was observed towards CM from LPS-treated-R182 (45%) than towards CM from LPS-treated CP70 (9%). When incubated with CM from LPS-treated-R182, THP-1 cells express a cytokine profile characteristic of M2 macrophages (high levels of MCP-1, MIF and IL-6). This was not observed when THP-1 was incubated with LPS alone or with CM from LPS-treated–CP70.

Conclusion:  In the present study we demonstrate that EOC cells have the capacity to attract THP-1 cells. Furthermore, we demonstrate that MyD88+ EOC cells are able to differentiate THP-1 cells into growth-promoting macrophages and establish a pro-tumor environment that can induce cancer cell proliferation. Our data suggest that cancer cells have the ability to attract and ‘educate’ immune cells to support its growth.