STC1 and airway hyperresponsiveness: STC1 has been for most part studied in the setting of cellular inflammation and carcinogenesis (Yeung et al., 2012; Zhao et al., 2020); however, a recent study found that STC1 is detectable in human blood serum, its level is significantly lower in asthmatics compared with healthy control subjects, and intranasal administration of recombinant human STC1 reduces airway hyperresponsiveness and inflammation in mice (Xu et al., 2020).