The key feature that distinguishes myeloma cells from normal plasma cells i
s the tumor cell's failure to lose proliferative potential. This article di
scusses the effects of a number of molecules that have been shown to impact
myeloma cell biology. On the basis of the differential effects of some of
these molecules on myeloma cells versus normal counterpart cells, a number
of key questions are raised, and several speculative models are proposed an
d discussed. Finally, this article highlights the need to understand intrac
ellular mechanisms of growth regulation in malignant plasma cells.