COL4A1 and head and neck squamous cell carcinoma: and also the COL4A1 was also identified as the potential therapeutic target genes in head and neck squamous cell carcinoma [25], colorectal carcinoma [26] and thyroid papillary carcinoma [27], it was also found that COL4A1 was the most significantly upregulated genes during the formation of the avian blood-gas barrier.