Abstract PL04-02: Microenvironments of carcinoma cell dissemination and metastasis: Insights derived in vivo

Abstract

Abstract The in vivo invasion assay (reviewed in [1]) was developed to collect the tumor cells observed in the multiphoton microscope to migrate toward and intravasate into blood vessels [2, 3]. The in vivo invasion assay has been coupled to expression profiling of small numbers of invasive cells to reveal the identities of the genes correlated with the survival, adjuvant-resistance and chemotaxis to macrophage supplied EGF, all phenotypes of these migratory tumor cells [4-6]. These genes fall into well defined pathways and are coordinately regulated in metastatic tumor cells [6-8]. These pathways are collectively called the Invasion Signature. Multi-photon microscopy (MPM) has been used to test the importance, in invasion and metastasis, of the pathways identified in the Invasion Signature including the ZBP1 [5, 9], ROCK [10], Mena [11], cofilin [12, 13] and EGF receptor [14, 15] pathways. The results of these studies confirm that the motility pathways are synergistic to create tumor cells that have passed through EMT and are capable of chemotaxis to EGF and penetration of basement membrane barriers using invadopodia (reviewed in [16, 17]). They also lead to a new insight that the motility pathways of invasive mammary tumor cells converge through the Mena pathway making the protein Mena a potentially important marker for prognosis and therapy [11, 18]. As described above, MPM had demonstrated that invasive carcinoma cells in mouse and rat mammary tumors intravasate when associated with peri-vascular macrophages thereby identifying a tumor microenvironment of intravasation as an anatomical landmark in tumors [19, 20]. Using this multiphoton imaging-defined anatomical landmark composed of an invading carcinoma cell marked by Mena over-expression, and a peri-vascular macrophage as a guide, it was possible to define a triple stain marker for use in anatomic pathology with anti-bodies against Mena, macrophages and endothelial cells to find the same landmark in human breast tumors [21]. In humans this landmark for intravasation is called TMEM (Tumor Microenvironment of Metastasis) and its density is correlated with metastatic risk in breast cancer patients [21]. This work illustrates the power of combining multi-photon imaging at single cell resolution with mouse models of breast cancer to develop new insights into the mechanisms of human breast cancer metastasis, and new prognostic markers for clinical use.