PITX1 and head and neck squamous cell carcinoma: For patients with HNSCC, low levels of PITX1 are a possible predictive biomarker of chemosensitivity: immunohistochemical analysis performed to examine the expression levels of PITX1 in 47 cases of HNSCC showed that the lowest level of PITX1 production was observed in the group of patients with stable or progressive disease, and the highest in the complete response group [48].