Chapter 23 Instability and Stabilization in Melanoma Cell Differentiation

Abstract

Publisher Summary Experimental embryology and cell biology have led to several different and even conflicting concepts or definitions of “cell types”, and different uses of the same term can cause misunderstandings. Some of these definitions are, therefore, considered briefly in this chapter. It reviews evidence is reviewed from mouse melanoma (pigment tumor) cells and other systems, leading to the idea that a change in cell type (differentiation) may be unstable before becoming stable. The disparate definitions of “cell type” apply less to mature cells (like adult liver or nerve cells) than to immature cell types (like ectoderm) and to cell lineages—that is, the branching successions of immature cell types through which mature types develop. A lineage step is defined as a change in cell type. The problem is to detect such a step in practice, when one cell type changes into the next. Potency may be defined to include only mature cell types or also immature types. If potency is defined to include immature cell types, then the potency to produce myoblasts is lost here and commitment occurs; this illustrates an unbranching lineage step. Otherwise, if potency is taken to include only mature cell types, then the change from myoblast to muscle does not in itself constitute commitment. The latter view seems unduly narrow, although it is possible that the loss of potency to remain immature differs at a molecular level from loss of potency to produce a mature cell type.