Extracellular Matrix Deposition Drives Disease Progression and Reduces Rapamycin Response in LAM.
Abstract
RATIONALE
LAM is a rare cystic lung disease driven by nodules containing “LAM cells” and recruited LAM associated fibroblasts. Although rapamycin reduces lung function loss, some patients continue to decline, meaning additional therapies are needed.
OBJECTIVES
To investigate how the LAM nodule environment affects LAM cell proliferation and the response to rapamycin.
METHODS
Proteins altered in advanced LAM were identified using shotgun proteomics and immunohistochemistry in tissue from closely phenotyped patients. Genes associated with rapamycin insensitivity on LAM derived extracellular matrix were identified by RNA sequencing and validated using pharmacologic inhibitors.
MEASUREMENTS AND MAIN RESULTS
More advanced disease was associated a greater decline in FEV when treated with rapamycin (p=0.005). In advanced LAM, using proteomics analysis, an upregulation of protein clusters comprising extracellular matrix, glucose metabolism and the actin cytoskeleton was identified. RNA sequencing and immunohistochemistry confirmed expression of collagens I and VI in LAM associated fibroblasts and LAM nodules, and increased markers of collagen turnover in patient serum (p=0.0048). Growth of LAM patient-derived cells was faster on LAM associated fibroblast-derived extracellular matrix (p<0.0001) and incompletely suppressed by rapamycin. RNA sequencing identified upregulation of pathways driving cell cycle control, transcription and metabolism by extracellular matrix. Tractable, pro-proliferative, upregulated genes included , and Inhibitors of these pathways reduced LAM cell proliferation and enhanced the anti-proliferative effect of rapamycin.
CONCLUSIONS
Extracellular matrix deposition upregulates the expression of genes which may blunt the response to rapamycin but offer additional therapeutic opportunities for patients with established LAM.
