Abstract 4150: TNFα and TGFβ1 secreted by macrophages enhance breast cancer cell migration dynamics via the induction of NF-κB dependent MMP-1 expression
Authors: Li Ran , Lee Tara , Kamm Roger D. 
Published: August 2015

Abstract
Metastasis, which is a major cause of cancer death, depends on cancer cell's ability to migrate through the dense extracellular matrix (ECM) within the solid tumor. Recent studies have revealed that macrophages within the breast tumor microenvironment could promote tumor metastasis. However, it is still unclear how macrophages affect the migration dynamics (e.g. total speed and directedness) of cancer cells in 3D ECM that mimics the in vivo environment. To address this question, we co-cultured MDA-MB-231 breast cancer cells with Raw 264.7 macrophages inside a collagen I ECM embedded in a microfluidic device. Time-lapse microscopy was used to quantify the effects of macrophages on the total speed and directedness of cancer cell 3D migration. Various biochemical assays were also performed to investigate the mechanisms underlying the observed effects. We found that macrophages enhanced both cancer cell migration total speed and directedness, allowing cancer cells to migrate faster and more persistently. Since macrophages are the major producers of TNFα and TGFβ1, we used blocking antibodies against these two factors to investigate their contribution to macrophage-assisted cancer cell migration. We found that inhibiting macrophage-secreted TNFα or TGFβ1 alone only slightly diminished cancer cell migration directedness. In contrast, simultaneous inhibition of both TNFα and TGFβ1 completely abolished macrophage-enhanced cancer cell migration directedness. To investigate this result further, we quantified the migration directedness of cancer cells treated with TNFα and/or TGFβ1. We found that the treatment of cancer cells with TNFα or TGFβ1 alone did not significantly increase their migration directedness. However, treatment of cancer cells with both TNFα and TGFβ1 synergistically enhanced the migration directedness of cancer cells to the level when cancer cells were co-cultured with macrophages. This result suggests that macrophage-released TNFα and TGFβ1 are the main contributors to the increase in cancer cell migration directedness. Furthermore, using a MMP inhibitor, we found that the inhibition of cancer cells’ ability to breakdown ECM led to reduced migration directedness. Therefore, we showed, using western blotting, that macrophage-released TNFα and TGFβ1 synergistically induced the nuclear localization of NF-κB in cancer cells, leading to a synergistically enhanced expression of MMP-1. Taken together, our results indicate that macrophage-secreted TNFα and TGFβ1 could enhance cancer cell migration directedness via the induction of NF-κB nuclear localization and MMP-1 expression within cancer cells. Our results further suggest that both macrophage-released TNFα and TGFβ1 need to be simultaneously inhibited in order to effectively neutralize macrophage-enhanced cancer cell migration and metastasis.
Citation Format: Ran Li, Tara Lee, Roger D. Kamm. TNFα and TGFβ1 secreted by macrophages enhance breast cancer cell migration dynamics via the induction of NF-κB dependent MMP-1 expression. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4150. doi:10.1158/1538-7445.AM2015-4150