Effect of oxygen concentration on the growth and drug sensitivity of human melanoma cells in soft-agar clonogenic assay.

Tumor cells from a human melanoma xenograft show better colony growth and plating efficiency in soft agar when incubated in a 5% O2 atmosphere that at a higher concentration of 20% O2. Exposure to low drug concentrations under a 20% (but not 5%) O2 atmosphere stimulated plating efficiency. Enhanced sensitivity (4- to 20-fold) to a variety of chemotherapeutic agents was seen in cells incubated under low but not the higher O2 concentration. These studies suggest the important role of O2 concentration in tumor colony growth, plating efficiency, and drug cytotoxicity for human solid tumors in vitro.