GPD1L and head and neck squamous cell carcinoma: For example, Liu et al. discovered that the mRNA expression of GPD1L, which was found to be downregulated, and HIF1, which was found to be upregulated, exhibited a negative association (r = −.496, p = .001) in cT1-2 N0 head and neck squamous cell carcinoma (HNSCC) [17].