BMP4 and cancer: It is noteworthy that HIF1α and BMP4 have both been reported not only to promote MUC5AC expression, but also to upregulate expression of OCT4 (Qi et al., 2004; Zhang K. et al., 2010; Chen et al., 2011; Mathieu et al., 2011; Iida et al., 2012; Li et al., 2016; Liu et al., 2020), which is a pluripotency gene and a marker for lung and cancer stem cells (Ling et al., 2006; Chen Y. et al., 2007; Chen et al., 2008; Gonzalez et al., 2009; Karoubi et al., 2009; Chiou et al., 2010; Zhang X. et al., 2010; Khatri et al., 2012; Bora-Singhal et al., 2015; Jen et al., 2017).