The Synthetic Parasite-Derived Peptide GK1 Increases Survival in a Preclinical Mouse Melanoma Model

Purpose: The therapeutic efficacy of a synthetic parasite-derived peptide GK1, an immune response booster, was evaluated in a mouse melanoma model. This melanoma model correlates with human stage IIb melanoma, which is treated with wide surgical excision; a parallel study employing a surgical treatment was carried out as an instructive goal. Experimental Design: C57BL/6 mice were injected subcutaneously in the flank with 2x10(5) B16-F10 murine melanoma cells. When the tumors reached 20mm(3), mice were separated into two different groups; the GK1 group, treated weekly with peritumoral injections of GK1 (10g/100L of sterile saline solution) and the control group, treated weekly with an antiseptic peritumoral injection of 100L of sterile saline solution without further intervention. All mice were monitored daily for clinical appearance, tumor size, and survival. Surgical treatment was performed in parallel when the tumor size was 20mm(3) (group A), 500mm(3) (group B), and >500mm(3) (group C). Results: The GK1 peptide effectively increased the mean survival time by 9.05 days, corresponding to an increase of 42.58%, and significantly delayed tumor growth from day 3 to 12 of treatment. In addition, tumor necrosis was significantly increased (p<0.05) in the treated mice. The overall survival rates obtained with surgical treatment at 6 months were 83.33% for group A, 40% for group B, and 0% for group C, with significant differences (p<0.05) among the groups. Conclusions: The GK1 peptide demonstrated therapeutic properties in a mouse melanoma model, as treatment resulted in a significant increase in the mean survival time of the treated animals (42.58%). The potential for GK1 to be used as a primary or adjuvant component of chemotherapeutic cocktails for the treatment of experimental and human cancers remains to be determined, and surgical removal remains a challenge for any new experimental treatment of melanoma in mouse models.