Fig. 1. Prak deficiency impairs distant metastases but not the growth of primary tumors.

a, b Prak knockout mice were crossbred with MMTV-PyMT mice. The development of mammary tumors and lung metastases were compared among the wild type, Prak^−/−, and PRAK inhibitor-treated PyMT mice at week 16. Data are presented as the ratio of mammary tumor vs. body weight (a) or the number of metastatic colonies in the lung (b). Each symbol represents an individual mouse. c–f Prak knockout (KO) clones were generated from the parent B16 melanoma line using CRISPR/Cas9. Loss of PRAK protein expression was confirmed by Immunoblotting (c). The volume of tumors formed by subcutaneously inoculated B16 clones was recorded at different time points. n = 7 biologically independent animals were examined. Data are presented as mean ±  s.d. with seven mice for each group (d). Tumor colonization in the lung was examined at day 16 after intravenous injection. Representative images (e, left) and quantification of tumor colonies (e, right) are shown. Survival rate was also monitored after intravenous injection of the parent or Prak knockout B16 clones (f). The histogram bars displayed as mean ± s.d. **p < 0.01, ***p < 0.001, ****p < 0.0001. p-value was determined by two-tailed, unpaired t-test (a, b, e) or Log-rank test (f).