Fig. 4

LOC606724 enhances c-Myc protein synthesis in MM cells. a. Western blotting shows the levels of oncogenic or tumor suppressive proteins in ARP-1 and MM.1S cells cultured with shLOC MMAD-derived exosomes. Treatment of PBS or exosomes from shCtrl MMADs served as control. b & c. The levels of c-Myc proteins (b) and mRNAs (c) in ARP-1 or MM.1S cells overexpressed with empty vector (Vec) or LOC606724 (LOC). d. Western blots show the levels of c-Myc protein in ARP-1 or MM.1S cells overexpressed with Vec or LOC treated with 100 µM cycloheximide (CHX) for various length of time. e. Western blots show the levels of c-Myc protein in ARP-1 or MM.1S cells overexpressed with Vec or LOC treated with 10 µM MG132 for 0, 60, and 120 min. f & g. Cell lysates of MM cell ARP-1 (f) or MM.1S (g) overexpressed with Vec or LOC were pulled down by an anti-Eif4E antibody, and RIP assay shows the relative enrichment of LOC and c-Myc in those cells. Cell lysates pulled by IgG served as control. h & i. ARP-1 cells overexpressing empty vector or c-Myc were treated with 5 nM bortezomib in the presence of vehicle or exosomes derived from shCtrl or shLOC606724 MMADs for 24 h. Western blotting shows the levels of c-Myc (h) and Annexin V-binding assay shows the percentages of apoptotic ARP-1 cells (i). For western blotting, GAPDH served as loading control. Data shown as mean ± SD. ns, non-significant; **P < 0.01; ***P < 0.001; ****P < 0.0001. P values were determined by Student t-tests for comparison of two groups and one-way ANOVA for comparison of more than two groups