SLC2A1 and thyroid gland carcinoma: For example, in human endometrial tumors, elevated levels of ascorbic acid within the tumor have been shown to correlate with decreased expression of HIF-1α, VEGF, and GLUT1 proteins, leading to a marked reduction in malignancy.300 Furthermore, ascorbic acid has been shown to induce a dose-dependent decrease in the expression of HIF-1α and GLUT1, both identified as downstream targets of HIF-1, in thyroid cancer cells in vitro.