Inhibition of GCK in MM cells abrogates tumor growth in vivo. Tet-on-shCNTL-MM.1S or Tet-On-shGCK-MM.1S cells were injected subcutaneously into SCID/bg mice. Sixteen days after implantation, all mice developed a subcutaneous tumor and were randomized to receive either vehicle (5% sucrose) or Dox (1 mg/mL in 5% sucrose) via drinking water for the duration of study. (A) Subcutaneous tumor growth was measured by using calipers and calculated with the volume formula: 0.5 × long diameter × short diameter.²  Each bar represents the mean ± standard error of the mean (SEM; n = 5). **Indicates significance with P < .01. (B) Mice were euthanized after 38 days. Tumors were excised and weighed. Tumor weights are reported as mean ± SEM (n = 5). **Indicates significance with P < .01. (C) Tumors harvested at the end of the study were fixed in 10% formalin and subsequently processed for immunohistochemical staining for GCK and IKZF1. The slides were scanned using a high-resolution scanner (Leica SCN400 Slide Scanner) at ×40 magnification. (D) SCID/bg mice were injected with Tet-On-shCNTL-MM.1S or Tet-On-shGCK-MM.1S cells expressing luciferase (n = 5). After 1, 2, and 3 weeks, mice received intraperitoneal (3 mg/mouse) d-luciferin 10 minutes before BLI. Bioluminescent signal and grayscale photographic images were acquired using the IVIS Spectrum Bioluminescence and Fluorescence Optical Imaging System and Living Image software.