To assess whether the combination of butyrate and doxorubicin potentiate apoptosis at their IC50 or sub-IC50 concentrations, five myeloma cell lines carrying wild-type or mutant p53 alleles were treated with either butyrate, doxorubicin alone or with their combination for 48 h, and apoptotic indices were assessed by TUNEL assay (Figure 1A). This evidence concerns the gene TP53 and plasma cell myeloma.