Focal Adhesion Kinase inhibition for dual targeting of osteosarcoma cells and the tumor microenvironment to prevent metastasis - Project Summary. Despite intensive efforts, outcomes for patients with osteosarcoma (OS), the most common primary malignant pediatric bone tumor, have not improved since the advent of multi-drug chemotherapy in the 1980s. This clinical failure is attributable to our inability to overcome intrinsic or adaptive resistance in the >30% of OS patients who fail frontline chemotherapy and develop tumor recurrence, nearly always in the form of lung metastasis. The tumor microenvironment (TME) is recognized as a key barrier to therapeutic efficacy in solid tumors. Our overall goal is to understand how cell intrinsic molecular drivers regulate immunologic mechanisms that shape a metastasis permissive environment in the lung to inform development of both primary anti- metastatic drugs and co-targeting approaches to potentiate other cancer therapies in OS. We previously developed a strategy for depletion of metastasis associated macrophages, via blockade of monocyte migration with oral dosing of a repurposed CCR2 antagonist (losartan), combined with a multi-kinase inhibitor (toceranib), which resulted in significant clinical benefit (50% response rate) in dogs with spontaneous metastatic OS. Based on this canine data, this drug combination is currently in a Phase I trial in pediatric OS (NCT03900793). Our preliminary data suggest focal adhesion kinase (FAK) signaling 1) is an OS cell intrinsic dependency, 2) promotes fibroblast enrichment and pro-tumorigenic function in the OS TME, and 3) that fibroblasts mediate OS cell resistance to platinum therapy. Therefore, the objective of this proposal is to define the mechanisms by which FAK signaling in OS tumor cells and lung fibroblasts shapes immune composition of the lung metastatic TME, and to test whether molecular targeting of FAK improves standard-of-care platinum chemotherapy (SOCC) response. We hypothesize that a combination of tumor cell intrinsic and lung fibroblast FAK signaling drives a chemokine secretion profile that mediates a feed-forward loop of increased macrophage recruitment, fibroblast proliferation, and subsequent T cell exclusion to promote OS metastasis. In Aim 1, we will use a combination of wild-type and FAK-/- syngeneic and patient-derived OS cells, and fibroblast specific FAK knockout mouse metastasis models, in parallel with clinically annotated human OS tumors, to define the contributions of tumor intrinsic and lung fibroblast FAK signaling on chemokine expression, TME composition, and progression of OS lung metastasis. In Aim 2a, we will leverage dogs with spontaneous OS, the most faithful model of a pediatric solid tumor, to determine if dual compartment OS cell and TME targeting of lung fibroblasts with a FAK inhibitor significantly improves the response rate to SOCC. In Aim 2b, we leverage bronchoalveolar lavage, a novel lung TME monitoring approach developed in our lab and uniquely employable in dogs, and primary tumor multi-omic profiling, to identify mechanistic predictors of canine patient response to this immunotherapy. Completion of these studies will inform basic immuno-oncology research in pediatric OS and generate readily translatable data leading to deployment of this orally administered and clinically well tolerated immunotherapy in a human OS trial.
