GREM1 and neoplasm: The growth of tumors at the primary site showed that Grem1 knockdown cells grew much slower than control cells, leading to a dramatic reduction in tumor volume (mean ± SD (mm3): 1037.812 ± 677.76 (MTV/TM-011-shCtrl-luc) vs. 41.39 ± 69.33 (MTV/TM-011-shGrem1-luc), six mice/each group) (Figure 4B,C).