|MadSci Network: Cell Biology|
Short answer: yes you can!
The purpose of CO2 (typically 5% by volume) in incubators is to maintain the pH of the culture medium at an acceptable level. Cell culture media typically contain sodium bicarbonate as a buffering agent, but a bicarbonate system loses its buffering capacity above pH 7.4, which is in the range typically desired for cells. The CO2 dissolves in the water of the medium and reacts to form carbonic acid (H2CO3), which is in equilibrium with the bicarbonate (HCO3-) and carbonate ions (CO3(2-)). Therefore, the addition of CO2 releases hydrogen ions and helps to keep the pH of the medium from climbing too high.
This limitation of the bicarbonate buffering system can be overcome with the use of other buffers; the most commonly used is HEPES. Using HEPES can allow you to maintain an acceptable pH in the culture medium without the use of CO2. HEPES is not used routinely because of its greater cost and toxicity in some cells. Make sure to test for toxicity in your cancer cells before beginning to use HEPES routinely.
For more information, I suggest you check the Sigma Cell Culture Handbook and the references listed in their product literature for HEPES.
One other note: even if you're not using a CO2 incubator, you will still need an environment that maintains the temperature at 37 degrees (assuming these are human cancer cells).
Try the links in the MadSci Library for more information on Cell Biology.