Project Summary
Osteosarcoma (OSA), the most common primary malignant tumor of bone, has seen almost no improvement in
patient overall survival rates since the 1980s. Approximately 30-40% of OSA patients develop tumor recurrence,
with metastasis to the lung, occurring on average 1.6 years after diagnosis, accounting for 75-90% of
recurrences. Once present, initially effective first-line therapies no longer provide clinical benefit in the metastatic
setting, and only ~20% of these patients remain alive 4 years after recurrence. More concerning, there are no
diagnostic methods which effectively identify those 30-40% of OSA patients at high risk for developing lung
metastasis at time of initial diagnosis. While intensive investigation continues on intrinsic properties of tumor
cells which confer their metastatic ability, emerging research has highlighted a critical role for non-malignant
stromal cells of the host in extrinsic promotion of metastasis. Termed the pre-metastatic niche, studies in certain
cancers have shown that tumor-derived soluble factors, including cytokines and exosomes, prime stromal cells
of distant organs to generate microenvironments conducive to tumor cell outgrowth upon their subsequent
arrival. Despite a significantly high and rapid rate of lung metastasis in OSA, little is known about the extrinsic,
host-mediated mechanisms which govern this process. Interestingly, the group of pulmonary disorders termed
interstitial lung disease (ILD) share significant overlap in their molecular pathogenesis of fibroblast-mediated
lung remodeling with those of pre-metastatic niche formation. In both ILD and pre-metastatic niche formation,
cytokines drive activation of a synthetic phenotype in resident lung fibroblasts, interestingly which is associated
with transcriptomic changes in ILD patient-derived alveolar macrophages (AMs) predictive of this remodeling.
Based on these observations, we hypothesize that OSA-derived soluble factors prime lung fibroblasts to foster
metastasis, and that AMs can serve as effective sentinels of this priming via manifestation of a unique,
metastasis-indicative molecular signature. To investigate this, we will utilize 3D organotypic co-culture of human
OSA cells and primary lung fibroblasts as an in vitro model to recapitulate OSA lung micro-metastasis. We aim
to compare differences in the secretome of paired high and low-metastatic phenotype human OSA cells cultured
in standard 2D and 3D monoculture, versus co-culture with lung fibroblasts, via multiplex cytokine analysis, and
quantitative mass spectrometry of exosomal protein cargo. Subsequently, we will determine the effects of these
differentially generated tumor or tumor-fibroblast soluble factors on transcriptional changes in primary human
AMs via RNA sequencing and differential gene expression profiling. Identification of the soluble factors and host
cellular responses extrinsically driving OSA lung metastasis will provide the foundation for development of both
biomarkers and novel therapies which identify and treat OSA patients at high-risk for lung metastasis.