Proliferative response of MM cell line ANBL-6 to exogenous IL-6, stromal cell interactions, and activating N-ras mutations. Cell cycle analysis of ANBL-6.plxsn cells in the absence or presence of recombinant IL-6, after coculture with MM stromal cells, or stably transfected with a mutant N-ras gene. Numbers on the left indicate the percentage of subdiploid nuclei. Numbers on the right indicate percentage of nuclei in S/G₂/M phases of the cell cycle.