Fig. 1.

Antitumor effects of low-dose P₄N in immune-competent and -deficient mice. (A) BALB/c (n = 10 per group) and nude mice (n = 10 per group) bearing CT26 tumors were treated with a single intratumoral injection of 2.5 or 5.0 mg/kg of P₄N. (B) B-cell– or CD8⁺ T-cell–depleted BALB/c mice (n = 9 per group) bearing CT26 tumors were treated with 5 mg/kg of P₄N by intratumoral injection every week. Tumor volumes were measured every 2 d after treatment. Significant differences between the P₄N groups and the PBS group were identified and labeled with *P < 0.05 and **P < 0.01. (C) IHC staining was used to monitor the infiltration of macrophages (F4/80), DCs (CD11c), T cells (CD3), and B cells (CD20) in the tumor area after a single intratumoral injection of PBS or 5 mg/kg of P₄N. The photographs are representative of the mice killed on day 7 after the treatments. (D) Expression of TNF-α and IL-8 in the tumors was also observed by IHC staining. (Magnification: C and D, 400×.)