Abstract A049: Three-dimensional microfluidic platform mimicking the tumor microenvironment

Immunotherapy is currently a main breakthrough in cancer treatment, but therapeutic approaches for solid tumors still present limitations in the clinical scenario due to the challenges posed by the immunosuppressive tumor microenvironment (TME). Specifically, among immune cells recruited to the TME, monocytes/macrophages are especially abundant. Macrophages in vitro have been classified as classically activated M1 macrophages and alternatively activated M2 macrophages. However, macrophages are highly plastic cells and they often present mixed phenotypes in the in vivo TME. Monocytes/macrophages are involved in cancer cell proliferation, cell invasion, cell killing, vascular angiogenesis, T-cell immunosuppression, and are often correlated with a poor outcome in an extended range of cancers. However, disrupting the protumor activity of monocytes/macrophages and their interactions with the complex cellular system in the TME remains a challenge. Thus, a better understanding of the mechanisms that modulate monocyte/macrophage phenotype and their interactions with tumors may lead to make them a relevant therapeutic strategy. To study the immunosuppressive TME, we developed microfluidic-based integrated platforms with a 3-dimensional (3D) co-culture of tumor cells and immune cells to investigate how physical and molecular cues in the TME regulate the cellular interplay. Our 3D multicellular platforms offer considerable benefits and have already demonstrated in previous studies a clear advantage over classical 2D platforms to model the TME and to screen for different therapeutic approaches. Our previous studies demonstrated the crucial role of immune system interactions with cancer cells in metastasis either at a primary tumor site or at a secondary metastatic site. Further, we investigated the impact of monocytes and Programmed Death Ligand 1 (PD-L1) immune checkpoint on T-cell receptor (TCR)-engineered T-cells. We have now developed a new 3D microfluidic platform to study the effects of interstitial flow (IF), the flow of fluid through tumor stroma, which is an important component of the TME that may contribute to the polarization of macrophages toward a protumor phenotype. The microfluidic model allows the co-culture of tumor cells and monocytes/macrophages, to stimulate them with IF and to quantify cell migration in 3D. To the best of our knowledge, this study represents the first microfluidic tumor model that incorporates IF and both tumor and immune cells. Our preliminary results confirmed that the presence of tumor cells and hence tumor-cell secreted factors (TSF) increased the migration speed and directedness of macrophages toward cancer cells, potentially contributing to cancer cell dissemination. Interestingly, the presence of the IF-based mechanical cue (without tumor cells in culture) resulted in a similar increase in macrophage migration. Further, by combining both TSF and IF we observed no synergistic or additive effect on macrophage migration. A mixed population of macrophage phenotypes (M1 and M2) was observed with either the stimulus of TSF and/or IF while lower expression levels of M1 and M2 markers were observed without TSF or IF. Importantly, the understanding gained from this investigation can help in the design and functional testing of immunotherapeutic strategies to modulate macrophage polarization in the TME towards an antitumor phenotype. Citation Format: Andrea Pavesi, Siew Cheng Wong, Roger Kamm, Sharon Wei Ling Lee, Giulia Adriani. Three-dimensional microfluidic platform mimicking the tumor microenvironment [abstract]. In: Proceedings of the Fourth CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; Sept 30-Oct 3, 2018; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2019;7(2 Suppl):Abstract nr A049.