Elevated expression of HR-related genes in MM cells. (A) Gene expression profile was measured in 3 normal plasma cell isolates (P₁, P₂, P₃), 6 myeloma cell lines (D indicates ARD; K, ARK; P, ARP; M, MM1s; U, U266; and 8, RPMI8226), and 15 purified myeloma cells from patient bone marrows (1-15) with the use of HG-U133 gene arrays. The color scale at the bottom of the figure represents fold change in recombination- and repair-associated genes in myeloma cells relative to average expression in 3 normal plasma cell samples. (B) Protein levels of HsRAD51 and its paralogs were detected by immunostaining, with either a polyclonal antibody against HsRAD51, also recognizing RAD51B and RAD51C or monoclonal antibodies recognizing HsRAD51 or its paralogs individually. (i) Normal plasma cells, no primary antibody control; (ii) normal plasma cells (donor 1), HsRAD51/51B/51C; (iii) normal plasma cells (donor 2), HsRAD51/51B/51C; (iv) ARP myeloma cell line, HsRAD51/51B/51C; (v) MM1S myeloma cell line, HsRAD51/51B/51C; (vi) U266 myeloma cell line, HsRAD51/51B/51C; (vii) patient myeloma cells, HsRAD51; (viii) patient myeloma cells HsRAD51B; (ix) patient myeloma cells, HsRAD51C; and (x) patient myeloma cells, HsRAD51D.