Expression kinetics of Ecat1, Dppa5, and GDF3 during tumorigenesis. B16-F1 and B16-F10 cells were injected subcutaneously into C57BL/6 mice. Tumors were excised on the indicated day. Total RNA was extracted from the tumor and RT-PCR (A-D) or RT-qPCR (E, F) was performed to detect Ecat1, Dppa5, and GDF3. (A, B) RT-PCR analyses revealed that mRNA of Eca1 and Dppa5 decreased during tumorigenesis. (C, E) In B16-F1 cells, GDF3 peaked at day 7 after tumor injection and then gradually decreased. (D, F). In contrast, GDF3 expression in B16-F10 cells increased 7 days after tumor injection and maintained a high level until 14 days after injection.