Abstract 5171: Restoration of fibronectin matrix assembly impedes invasion and reduces tumor-stromal cell affinity in prostate cancer

Cell-cell and cell-ECM interactions are important regulators of cohesion, a property previously demonstrated to mediate malignant invasion. Intermixing of the epithelial and stromal compartments is often associated with increased invasive capacity and poor prognosis. The studies reported here propose a novel role for α5β1 integrin, the principle mediator of fibronectin matrix assembly (FNMA), as an invasion suppressor in prostate cancer cells. Employing a combination of biophysical and cell biological techniques we explore the relationship between cohesion, invasion, FNMA and tumor-stromal interactions, using a well-characterized prostate cancer model. We show that cohesion is inversely proportional to invasive capacity. We also show that the most invasive cells are deficient in FNMA and express reduced levels of α5β1 integrin. We generated cells over-expressing either wild-type α5 integrin or a non-functional α5 in which the cytoplasmic domain was replaced with that of α2. We show that only wild-type α5 was able to increase cohesion and reduce the invasiveness of aggressive cells. In order to further explore the influence of FNMA on tumor-stromal cell interaction we employed a liquid miscibility model in which interactions between tumor and stroma are rooted in the same thermodynamic principles that govern the mixing of simple fluids. In this model, whether tumor and stromal cells segregate or intermix depends on the ratio of the strength of self-cohesion to cross-adhesion; a high ratio corresponds with segregation, whereas a lower ratio denotes intermixing. We hypothesized that segregation between tumor and stroma can be promoted by increasing the strength of tumor cell cohesion. To test this hypothesis, we first showed that aggressive prostate cancer cells intermix with prostate fibroblasts. We then treated the cancer cells with MEK inhibitors (MEKi) and showed that treatment restored FNMA, leading to increased cell-cell cohesion. When mixed with prostate stromal cells, MEKi-treated cells segregated, suggesting that increasing cohesion between tumor cells is sufficient to reduce their affinity for stromal cells. These data suggest that by increasing tumor cell cohesion through a fibronectin matrix mediated adhesion mechanism, it may be possible to effectively reduce affinity of tumor cells for stroma, thus inhibiting invasion. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association