MUC5B and idiopathic pulmonary fibrosis: Besides the promoter variant rs35705950, which definitely causes an overexpression of MUC5B and appears to be predictive of IPF, some transcriptional factors, inflammatory mediators, and associated signaling pathways may also mediate MUC5B overexpression, providing clues for further research regarding the mechanisms of MUC5B overexpression in IPF, and may facilitate development of novel treatments for this fatal disease with limited treatment options.