Inhibiting MCL1 suppresses the growth of the myeloma cell line AMO1 in vivo. (A) Expression of the MCL1-selective ligand BIM2A slows the growth of AMO1 myeloma cells in vivo. Here, 5 × 106 AMO1 cells engineered to coexpress the luciferase gene and the BIM variants were injected intravenously into female NSG mice. Ten days after tumor inoculation (indicated by an arrow, ↑), the mice were divided into those fed with DOX-containing (+: to induce expression of the BIM variant) or normal (−) food, and the mice then were imaged every 3 days afterward on days 3, 6, and 9. Compared with the mice expressing BIM4E or the control mice fed with normal food, significant suppression of tumor growth was observed in mice expressing BIM2A. The results are representative of 2 independent experiments (n = 3 mice in each group). The average luciferase activity was calculated from the dorsal, lateral, and ventral views of the mice. Detailed results are shown in supplemental Figure 18. (B) Representative of images of the mice described in A 9 days after commencing DOX treatment. (C) Expression of BIM2A slows disease progression in vivo. The infiltration of myeloma cells (CD38+) in the peripheral blood (upper), bone marrow (middle), or serum paraprotein (IgAκ) levels (bottom) were determined 0 to 10 days after the mice were commenced on treatment with DOX (n = 3 mice in each group). Note the delayed disease progression when expression of BIM2A was induced. (D) BIM2A ameliorates the infiltration of AMO1 myeloma cells into the bone marrow. Representative histological images (H&E staining; ×0.4 or ×5 magnification) for detection of bone marrow infiltration with myeloma cells (pale areas) taken from the legs of representative mice. The regions marked with an arrow (left) were enlarged for higher magnification (right; ×5 instead of ×0.4).
