SFTPC and lung cancer: The extracellular receptors pneumococcal surface protein C (PspC) and platelet-activating factor receptor (PAFR) help S. pneumoniae to enter host lung cancer cells, which subsequently activates the phosphoinositide-3-kinase/protein kinase B (PI3K/AKT) and NF-κB signaling pathways, and consequently, accelerates lung cancer progression and metastasis via exaggerating chronic inflammation in the microenvironment [21].