RB1 and plasma cell myeloma: Studies examining the RB1 gene transcription and pRB expression in 22 human myeloma cell lines (HMCLs) and in 10 advanced-stage patients did not identify changes in the expression of pRB during the transition from the IL-6 paracrine to autocrine states, suggesting a lack of association between pRB deletion and IL-6 expression in MM.