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The effect of blockage of macrophage on tumor-suppressive activity of polyactin B
Objective:
To investigate the tumor-suppressive activity of polyactin B (PB) and the life-span of tumor bearing mice treated with PB and the anti-tumor mechanisms of PB by blockage of macrophage in vivo.
Methods:
Thirty-two S180 sarcoma-bearing (s.c.) BALB/c inbred mice were divided into 4 groups, i.e., control group (8 mice), PB group (8), Trypan blue (TrB) group (8) and PB + TrB group (8). Five days after PB injection (i.p.), the tumor size of the mice was measured, and the ratio of TNA to TTA in HE section of the tumor maximal area was calculated and the pathological features of the tumors were observed. Forty S180 sarcoma-bearing (i.p.) ICR mice, which were randomly divided into 4 groups as above, were used for observation of the life-span.
Results:
PB could strongly inhibit the growth of S180 sarcoma with the tumors regressing completely in 3 of 8 mice, prolong the life-span of mice bearing S180 sarcoma, increase the infiltration of macrophages and lymphocytes in the periphery and inside of the tumors. In addition, there were more prominent hemorrhagic necrosis, neutrophil infiltration and microthrombi in small vessels around the necrotic areas in the tumors of PB treated group. The tumor-suppressive effect of PB disappeared after macrophage system blockage with TrB. In PB + TrB, TrB, control and PB groups, the size of tumors reduced, and the life-span of mice increased in successive order.
Conclusions:
(1) PB is a strong activator of macrophage. (2) In vivo the tumor-suppressive effect of PB is initially mediated by PB activated macrophage system. Then other immunocompetent cells, e.g., T-cells, NK-cells, etc, activated directly and/or indirectly by PB, may play a very important role in tumor suppression. (3) PB-activated macrophages are more sensitive to TrB blockage. Therefore, using TrB + PB to block macrophage system is more effective than TrB alone. (4) Blockage of macrophage function might influence the life-span of the mice.
Insights
Polyactin B (PB) demonstrates significant tumor-suppressive activity by activating macrophages, which are crucial for its anti-tumor effects in S180 sarcoma-bearing mice. Blocking macrophages diminishes PB
Area of Science:
- Immunology
- Oncology
- Pharmacology
Background:
- Polyactin B (PB) is investigated for its potential tumor-suppressive properties.
- The study aims to elucidate the anti-tumor mechanisms of PB, focusing on its interaction with the macrophage system in vivo.
Observation:
- PB treatment led to significant inhibition of S180 sarcoma growth, with complete tumor regression in some mice.
- PB administration increased macrophage and lymphocyte infiltration within tumors and prolonged the lifespan of tumor-bearing mice.
- Macrophage system blockage with Trypan blue (TrB) abolished the tumor-suppressive effect of PB.
Findings:
- Polyactin B (PB) is identified as a potent macrophage activator.
- The primary anti-tumor mechanism of PB involves the activation of the macrophage system, with subsequent roles for other immune cells like T-cells and NK-cells.
- PB-activated macrophages exhibit increased sensitivity to Trypan blue (TrB) blockage, suggesting a synergistic effect when combined.
Implications:
- PB holds promise as an anti-cancer agent, primarily through immune system modulation.
- Understanding PB's mechanism involving macrophages provides insights for developing novel immunotherapies.
- Targeting macrophage function could be a viable strategy to enhance anti-tumor responses and improve survival in cancer patients.
