PLK1 and kidney neoplasm: The relationship between hypoxia and Plk1 expression was further assessed in human RCC kidney tumor cell lines (RCC4 (R4), RCC10 (R10), 786-O (786), A498 (498), ACHN (A), Caki2 (C2); Fig. 2a) and human primary normal (15S) and human primary confirmed RCC cells (TF, MM, CC; Fig. 2b)19.