Peritumoral CpG oligodeoxynucleotide treatment inhibits tumor growth and metastasis of B16F10 melanoma cells

Although melanoma mostly affects the skin, it is notorious for its propensity to easily develop metastasis. Metastatic melanoma is highly resistant to a variety of therapies. We examined the anti-metastatic potential of peritumoral monotherapy against murine cutaneous B16F10 melanoma with synthetic oligodeoxynucleotides (ODN) containing unmethylated CpG motifs. We demonstrated that repeated peritumoral injections of CpG ODN significantly reduced skin tumor size. Peritumoral CpG ODN-treatment of skin tumors prevented the development of pulmonary B16F10 colonies. Adoptive transfer of splenocytes obtained from CpG ODN-treated mice markedly reduced the number of previously established pulmonary colonies in recipient naive mice. T-lymphocyte depletion studies indicated that the anti-metastatic effect was dependent on both CD4(+) and CD8(+) T cells. These results suggest that CpG ODN are promising as a preventive and therapeutic anti-metastatic measure against melanoma.