TLR3 and neoplasm: Interestingly, tumor exosomal RNAs activate alveolar epithelial toll-like receptor 3 (TLR3) to induce chemokines (CXCL1, CXCL2, CXCL5, and CXCL12) that are critical for neutrophil recruitment and lung pre-metastatic niche formation (111).