Imaging techniques based on fluorescence and bioluminescence have been important tools in visualizing
tumor progression and studying the effect of drugs and
immunotherapies on
tumor immune microenvironment in animal models of
cancer. However, transgenic expression of foreign
proteins may induce immune responses in immunocompetent syngeneic
tumor transplant models and augment the efficacy of experimental drugs. In this study, we show that the growth rate of
Lewis lung carcinoma (LL/2)
tumors was reduced after transduction of
tdTomato and
luciferase (
tdTomato/Luc) compared to the parental cell line.
tdTomato/Luc expression by LL/2 cells altered the tumor microenvironment by increasing tumor-infiltrating lymphocytes (TILs) while inhibiting
tumor-induced myeloid-derived suppressor cells (MDSCs). Interestingly,
tdTomato/Luc expression did not alter the response of LL/2
tumors to anti-PD-1 and anti-CTLA-4
antibodies. These results suggest that the use of
tdTomato/Luc-transduced
cancer cells to conduct studies in immune competent mice may lead to cell-extrinsic
tdTomato/Luc-induced alterations in
tumor growth and
tumor immune microenvironment that need to be taken into consideration when evaluating the efficacy of anti-
cancer drugs and
vaccines in immunocompetent animal models.