Reduced Autophagy in 5-Fluorouracil Resistant Colon Cancer Cells.

We investigated the role of autophagy in SNUC5/5-FUR, 5-fluorouracil (5-FU) resistant SNUC5 colon cancer cells. SNUC5/5- FUR cells exhibited low level of autophagy, as determined by light microscopy, confocal microscopy, and flow cytometry following acridine orange staining, and the decreased level of GFP-LC3 puncta. In addition, expression of critical autophagic proteins such as Atg5, Beclin-1 and LC3-II and autophagic flux was diminished in SNUC5/5-FUR cells. Whereas production of reactive oxygen species (ROS) was significantly elevated in SNUC5/5-FUR cells, treatment with the ROS inhibitor N-acetyl cysteine further reduced the level of autophagy. Taken together, these results indicate that decreased autophagy is linked to 5-FU resistance in SNUC5 colon cancer cells.