Extracellular matrix mediators of metastatic cell colonization characterized using scaffold mimics of the pre-metastatic niche

Abstract

Metastatic tumor cells colonize the pre-metastatic niche, which is a complex microenvironment consisting partially of extracellular matrix (ECM) proteins. We sought to identify and validate novel contributors to tumor cell colonization using ECM coated poly(ε-caprolactone) (PCL) scaffolds as mimics of the pre-metastatic niche. Utilizing orthotopic breast cancer mouse models, fibronectin and collagen IV-coated scaffolds implanted in the subcutaneous space captured colonizing tumor cells, showing a greater than 2-fold increase in tumor cell accumulation at the implant site compared to uncoated scaffolds. As a strategy to identify additional ECM colonization contributors, decellularized matrix (DCM) from lungs and livers containing metastatic tumors were characterized. In vitro, metastatic cell adhesion was increased on DCM coatings from diseased organs relative to healthy DCM. Furthermore, in vivo implantations of diseased DCM-coated scaffolds had increased tumor cell colonization relative to healthy DCM coatings. Mass-spectrometry proteomics was performed on healthy and diseased DCM to identify candidates associated with colonization. Myeloperoxidase was identified as abundantly present in diseased organs and validated as a contributor to colonization using myeloperoxidase-coated scaffold implants. This work identified novel ECM proteins associated with colonization using decellularization and proteomics techniques and validated candidates using a scaffold to mimic the pre-metastatic niche.

Microporous scaffolds loaded with immunomodulatory lentivirus to study the contribution of immune cell populations to tumor cell recruitment in vivo

“…PCL scaffolds have been employed as a synthetic premetastatic niche (Aguado et al, ; Bushnell et al, ; Rao et al, ), and here, we investigated the ability to deliver lentivirus to achieve sustained transgene expression as outlined in the experimental platform and timeline in Figure . Transgene expression was analyzed after implantation into the fat pad via delivery of FLUC lentivirus and bioluminescence imaging (Figure a).…”

“…We hypothesized that delivery of these cytokines would alter the recruitment of circulating tumor cells. Thus, we next investigated the effect of immunomodulatory cytokine delivery on tumor cell abundance in implanted scaffolds (Figure ) that have previously been shown to recruit tumor cells at this implant site and time scale (Aguado et al, ; Aguado et al, ; Aguado et al, ; Aguado et al, ; Azarin et al, ; Rao et al, ) with an experimentally determined detection limit of five tumor cells in 250,000 total cells (0.002%) by flow cytometry (Azarin et al, ). We found that IL10 significantly reduced the percentage of tdTomato+4T1 metastatic tumor cells spontaneously arriving at the scaffold relative to FLUC (0.06 ± 0.03% tdTomato+ of total cells for IL10, 0.13 ± 0.04% tdTomato+ for FLUC, 0.09 ± 0.02% tdTomato+ for CCL2, and 0.11 ± 0.04% tdTomato+ for CXCL12).…”

“…In this report, we hypothesized that local modulation of the immune microenvironment could serve as a means to influence tumor cell abundance and to dissect the contribution of specific immune cell populations to the recruitment of tumor cells to a metastatic site. Biomaterials that recruit metastatic cancer cells in vivo are an emerging technology to investigate tumor cell abundance and phenotype at a premetastatic niche (Aguado et al, ; Aguado et al, ; Aguado et al, ; Aguado et al, ; Azarin et al, ; Bersani et al, ; Ko et al, ; J. Lee et al, ; Rao et al, ). First, they provide a defined site in vivo to which tumor cells are recruited.…”

Recent advances in understanding the complexities of metastasis

“…For example, pancreatic cancer cell-secreted exosomes have been shown to accumulate in secondary tissues such as the liver and lead to the generation of pre-metastatic niches through activating hepatic stellate cells and Kupffer cells to drive ECM remodelling 243 and can be detected in the circulating blood, offering promise of potential biomarker applications. Given the technical limitations of studying these early pre-metastatic events in vivo and in the clinic, there has recently been a push to develop engineered niche-mimicking biomaterials to better study this process 247, 248 .…”

Biomimetic strategies to recapitulate organ specific microenvironments for studying breast cancer metastasis

“…To closely recapitulate BCLM, hybrid in vivo models have also been devised wherein PCL scaffolds coated with decellularized liver matrix were subcutaneously implanted in murine models followed by orthotopic injection of BCCs (Fig. c ).…”