To evaluate the tumor-targeting ability of GCD, we labeled GCD with Cy5 and incubated mice breast cancer cell line 4T1, human breast cancer cell line MDA-MB-231, human normal mammary epithelial cell line MCF-10A, human differentiated thyroid cancer cell line TPC1, and human normal thyroid epithelial cell line Nthy-ori 3.1 with Cy5-GCD (red) and then LysoTracker (green). This evidence concerns the gene GCDH and thyroid cancer.