Fig. 4: M1 acts as an immunostimulatory agent and induces T-cell recruitment and activation in tumor microenvironment (TME).

A C57BL/6 mice were implanted subcutaneously in the right flank with B16F10 cells on day 0 and treated intravenously with ctrl (n = 3) or M1 (n = 3) (1 × 10⁷ pfu) once per day on days 6–8. The tumors were harvested on day 9, the total RNA was isolated, and qRT-PCR was performed to detect the expression of chemokines. The P value was determined by a two-tailed Student’s t test. B–D C57BL/6 mice were implanted subcutaneously in the right flank with B16F10 cells on day 0 and treated intravenously with ctrl (n = 6) or M1 (n = 6) (1 × 10⁷ pfu) once per day on days 6–10. The tumors were harvested on day 13 and analyzed by flow cytometry to assess intratumoral T cells (B), the percentages of CD8⁺ and CD4⁺ T cells in the total T-cell population (C) and T_reg in the CD4⁺ T-cell population (D). The P value was determined by a two-tailed Student’s t test. E, F the expression of CD69, CD44, and PD-1 on CD4⁺ T cells (E) and CD8⁺ T cells (F) gated from B to D was detected by flow cytometry. The P value was determined by a two-tailed Student’s t test. Data are shown as the mean ± SD. n.s. not significant; *P < 0.05; **P < 0.01; ***P < 0.001; ****P < 0.0001.