MKI67 and neoplasm: Immunohistochemical analysis of tumor tissues for proliferation marker Ki-67 revealed that tumor cell proliferation was significantly decreased by Nintedanib compared to vehicle controls when the mice were exposed to the drug early-on, as in Experiment 1; though there was some decrease in tumor proliferation by Nintedanib in Experiment 2 as well, but it was not statistically significant (Fig. 6a).