Figure 4. Surgery promotes BC growth and inhibits antitumor immunity in mice.

(A-B) C57Bl/6 (BL6) male mice (n=6/group) were challenged intravenously with MB49 tumor cells then anesthetized and subjected to 3 cm ventral laparotomy (surgery) versus no surgery. Mice were followed for cancer-specific survival (CSS, metastasis confirmed by necropsy) or sacrificed on day 14. (A) Lungs were analyzed for the presence of tumors (mean±SEM on y-axis), quantified by gross examination (representative samples of lung sections from one control and surgery mice shown), and confirmed with histopathology. CSS with and without surgery shown. (B) Cell surface exhaustion markers were detected and measured for splenic T cells. N=7-10 mice/group. P: two-tailed t test. (C) BL6 female mice were challenged orthotopically with MB49 tumor cells then subjected to surgery versus no surgery and given anti–PD-L1 or isotype control antibody on days 7, 12, and 17. N=6-8 mice/group. Survival compared between surgery + anti–PD-L1 versus no surgery + anti–PD-L1 treated mice using log-rank test (significance shown as P). (D) In similar experiments with n=5 mice/group, bladder tumor-draining lymph nodes (TDLNs) were harvested on day 15 after tumor challenge. TDLN cells (0.25 x 10⁶ cells per well) were recalled ex vivo by incubating with irradiated MB49 cells in 1:1 cell TDLN to MB49 cell ratio, and absolute number (AN) of tumor-specific IFNγ-producing cells per TDLN were quantified by ELISPOT assay. Numbers under arrows represent median log-fold change between groups. P indicates the significance of the difference in fold change between surgery and no surgery assessed with two-sided testing on the group (surgery, no surgery) by condition (IgG control, anti–PD-L1) interaction term in a linear model of the number of tumor-specific IFNγ in log units. All other p values represent two-tailed t-tests. Data are from a representative experiment that was repeated with similar results.