Unique Requirements for Clonal Growth

Summary

Experiments on the formation of colonies from single cells were divided into two categories: 1) cloning, in which a new culture consisting entirely of the descendants. of a single cell is established; and 2) clonal growth, in which colony formation is used to evaluate specific responses or to examine specialized properties of individual cells. The safest procedures for cloning isolat a single cell into a separate culture vessel and therefore allow no possibility of contamination with other cells. Such elaborate procedures are not usually needed in other types of clonal-growth experiments where greater emphasis is placed on convenient preparation of replicate cultures, reproducibility, and high plating efficiency. The two major difficulties associated with clonal growth are 1) obtaining viable single cells in adequate numbers, and 2) getting them to grow. Suggested procedures and the need for additional research in each of these areas are discussed. A most serious problem is our lack of knowledgeof the nutrient requirements of unaltered diploid vertebrate cells. Without such knowledge, we cannot accurately evaluate the nutrient differences between normal and cancerous cells. We must strive to understand precisely the growth requirements of normal and malignan t cells so that maximum advantage can be taken of the differences that we believe exist between them. Clonal growth techniques are particularly sensitive for investigation of those requirements and differences.