Flow cytometric enumeration of colonies for in vitro chemotherapeutic drug evaluation

The percentage of 50-100 micron colonies formed by LX-T cells in medium containing agarose was determined microscopically, and this value was compared with the percentage determined by a flow cytometric method based on the forward and 90 degree light scatter of the colonies. As assessed by both in vitro methods, LX-T cells exposed to chemotherapeutic agents formed fewer colonies as the drug concentration increased. However, flow cytometric analysis indicated that a change in the number of colonies formed was a consequence of changing chemotherapeutic drug concentration, whereas microscopic colony counting did not always detect the corresponding change in colony number. These experiments demonstrate that measurement of a drug's chemotherapeutic potential by flow cytometric counting of colonies is an alternative to the enumeration of colonies microscopically.