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Phospholipase A2-mediated inflammation induces regression of malignant gliomas
D H Goddard1, J S Bomalaski, S Lipper
1Long Island College Hospital, Brooklyn, NY, USA.
Abstract:
An ideal form of cancer therapy is the harnessing of innate immunity to eradicate spontaneously arising clones of malignant cells. To date, attempts to develop effective immunotherapies have met with limited success. Prostaglandins and leukotrienes, collectively known as eicosanoids, are important mediators of immune and inflammatory responses. Harnessing these compounds could be a method to treat cancers. Eicosanoids are formed after cleavage of fatty acids from phospholipids by phospholipase enzymes. We have previously described, characterized and cloned a naturally occurring mammalian activator of phospholipase A2. Injection of a 24 amino acid peptide from this phospholipase A2 activating protein (PLAP), resulted in induction of an acute inflammatory response, and a concomitant regression of gliomas in rats. Administration of 500 micrograms of this protein resulted in a 50% decrease of the tumor mass within 72 h. Tumor regression coincided with a greater than twenty-fold increase in levels of prostaglandin E2(PGE2) and leukotriene B4(LTB4), and a marked infiltration of natural killer(NK) cells. These data suggest that activation of phospholipase A2 and modulation of the eicosanoid biosynthetic pathway may provide a novel therapeutic strategy for the successful treatment of malignant tumors of the nervous system.
Insights
Harnessing innate immunity via phospholipase A2 activating protein (PLAP) peptide shows promise for cancer therapy. This approach induced glioma regression in rats by modulating eicosanoids and increasing natural killer cells.
Area of Science:
- Immunology
- Oncology
- Biochemistry
Background:
- Cancer immunotherapy aims to utilize the innate immune system to eliminate malignant cells.
- Current immunotherapies have limited success.
- Eicosanoids (prostaglandins and leukotrienes) are key mediators of immune and inflammatory responses.
Purpose of the Study:
- To investigate the therapeutic potential of activating the phospholipase A2 pathway for cancer treatment.
- To evaluate the efficacy of a specific phospholipase A2 activating protein (PLAP) peptide in a preclinical cancer model.
Main Methods:
- Characterization and cloning of a mammalian phospholipase A2 activating protein (PLAP).
- Administration of a 24 amino acid PLAP peptide to rats with gliomas.
- Measurement of tumor mass, eicosanoid levels (PGE2, LTB4), and natural killer (NK) cell infiltration.
Main Results:
- Injection of the PLAP peptide induced an acute inflammatory response and significant glioma regression in rats.
- A 500 microgram dose of the peptide reduced tumor mass by 50% within 72 hours.
- Tumor regression was associated with a >20-fold increase in PGE2 and LTB4 levels and increased NK cell infiltration.
Conclusions:
- Activation of phospholipase A2 and modulation of eicosanoid biosynthesis represent a novel therapeutic strategy for central nervous system malignancies.
- PLAP peptide therapy holds potential for treating malignant tumors of the nervous system by leveraging innate immunity.
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