RAB5A and neoplasm: To this end, different tumor cell lines, including A549 human lung carcinoma, MDA-MB-231, ZR75 and MCF7 human breast cancer and B16-F10 mouse melanoma cells, were subjected to either normoxia (20% oxygen) or hypoxia (1% oxygen) for 24 hours, and Rab5-GTP levels were measured in pull-down assays.