Cancer Biology

Ovarian cancer is fairly unique in that ovarian carcinoma cells can detach and spread directly through peritoneal cavity. It has been unclear, however, how detached cancer cells survive in the peritoneum and form spheroid structure. We have recently reported that there is a strong correlation between Tumor-associated macrophages (TAMs)-associated spheroid and clinical pathology of ovarian cancer, and that TAMs promote spheroid formation and tumor growth at early stages of transcoelomic metastasis in orthotopic mouse models. We have established an in vitro spheroid formation assay using a 3D co-culture system in which mouse GFP⁺F4/80⁺CD206⁺ TAMs isolated from spheroids of ovarian cancer-bearing donor tomato^lysM-cre mice were mixed with ID8 cells (TAM:ID8 at a ratio of 1:10) in medium containing 2% Matrigel and seeded onto the 24-well plate precoated with Matrigel. As transcoelomic metastasis is also associated with many other cancers such as pancreatic and colon cancers, TAM-mediated spheroid formation assay would provide a useful approach to define the molecular mechanism and therapeutic targets for ovarian cancer and other transcoelomic metastasis cancers.

Understanding how immune cells such as macrophages interact with cancer cells is of increasing interest, as cancer treatments move towards combing both targeted- and immuno-therapies in new treatment regimes. This protocol is using THP-1 cells, a human leukemia monocytic cell line that can be differentiated into macrophages. This allows studying the effects of the macrophage secretome on cancer cells (on e.g., growth, drug response or gene expression) in co-cultures without direct cell contact interactions. This is an important aspect as it removes the presence of any phagocytic aspect to changes in the cancer cell number and behaviour. The in vitro THP-1 monocyte differentiation into polarized macrophages was used to study the effects of both M1 and M2 type populations of macrophages on melanoma cells (Smith et al., 2014; Tsuchiya et al., 1980). M1 type macrophages are classically thought to be tumour suppressing as opposed to M2 type macrophages, which are thought to possess tissue repairing and tumour growth promoting activities.

In the past years, a subset of regulatory T cells (Tregs) expressing CD4, CD25 and the transcription factor FoxP3 has gained considerable attention as key regulators of T-cell tolerance and homeostasis (Sakaguchi, 2004). This population of T cells is specifically engaged in the maintenance of immune self-tolerance and the control of aberrant immune responses to foreign antigens. Remarkably, regulatory T cells have been implicated in tumor cell evasion of immune responses (Curiel et al., 2004; Zou, 2006) by suppressing T cell mediated antitumor immunity. The study of the signals that promote the differentiation of this suppressive population in the tumor microenvironment has become a central issue. Here we described a detailed method to in vitro differentiate Tregs using tumor cells conditioned media from mouse naïve T cells and to identify them based on their specifics markers (Dalotto-Moreno et al., 2013).