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Immunotherapy of B-16 melanoma with peptidoglycan monomer
Abstract:
B-16 melanoma-bearing mice received intravenously or intratumorally one or multiple injections of peptidoglycan monomer (PGM) derived from Brevibacterium divaricatum cell wall. Multiple injections of this non-toxic, water-soluble, low-molecular-weight peptidoglycan reduced the growth rate of tumor nodule on the leg, but did not significantly prolong the survival of tumor-bearing mice. One milligram of PGM administered 3 or 7 days after tumor inoculation inhibited formation of pulmonary metastases, induced either by intravenous injection of malignant cells or seeded spontaneously from tumor nodules in the legs before amputation. The inhibition reached about 50% of control values in saline-treated mice. Addition of PGM to in vitro cultures of B-16 melanoma cells did not change their growth rate. The phagocytic activity in the lungs, but not in the spleen and liver, was significantly augmented 3 and 7 days after treatment with PGM. These data indicate that the antimetastatic potency of PGM is probably due to activation of local (pulmonary) macrophages and not due to direct cytotoxic effects on B-16 melanoma cells or to activation of systemic antineoplastic defence.
Insights
Peptidoglycan monomer (PGM) reduced melanoma growth and inhibited pulmonary metastases in mice. This antimetastatic effect is likely due to enhanced lung macrophage activity, not direct tumor cell toxicity.
Area of Science:
- Immunology
- Oncology
- Pharmacology
Background:
- B-16 melanoma is an aggressive cancer model.
- Peptidoglycan monomer (PGM) is a non-toxic compound derived from bacterial cell walls.
Purpose of the Study:
- To investigate the antimetastatic effects of PGM on B-16 melanoma in mice.
- To elucidate the mechanism of PGM's antimetastatic action.
Main Methods:
- B-16 melanoma-bearing mice were treated with PGM intravenously or intratumorally.
- Tumor growth, pulmonary metastasis formation, and macrophage phagocytic activity were assessed.
- In vitro cultures of B-16 melanoma cells were treated with PGM.
Main Results:
- Multiple PGM injections reduced tumor nodule growth but did not significantly prolong survival.
- A single PGM dose inhibited pulmonary metastases by approximately 50%.
- PGM treatment significantly augmented phagocytic activity in mouse lungs.
Conclusions:
- PGM exhibits significant antimetastatic potential against B-16 melanoma.
- The antimetastatic effect of PGM is likely mediated by the activation of pulmonary macrophages.
- PGM does not directly affect melanoma cell growth in vitro.