An ecosystem mimicking brain development promotes metastatic growth of SCLC in the brain

Small cell lung cancer (SCLC) is a fatal form of cancer that frequently metastasizes to the brain. Here we investigated the mechanisms allowing SCLC cells to grow in the unique brain microenvironment. We found that neuronal programs upregulated in SCLC cells during tumor progression and upon growth in the brain are critical for SCLC growth in the brain. Mechanistically, the presence of SCLC cells in the brain re-activates astrocytes, which in turn promote the survival of SCLC cells by secreting neuronal pro-survival factors such as SERPINE1. We also identified Reelin, a molecule produced by developing neurons to recruit astrocytes, as a molecule secreted by SCLC cells to recruit astrocytes to the tumor site and promote SCLC growth in the brain. Thus, SCLC cells co-opt mechanisms normally at play between astrocytes and neurons to promote SCLC growth in the brain. Targeting such developmental neuronal programs may help treat brain metastases. 6 samples were analyzed: brain stromal cells isolated from different regions of SCLC brain allografts (2 replicates) and sham injection control (2 replicates)