Peptides derived from the POU domain of BRN2 show antitumor activity against murine melanoma model cells in vitro and in vivo.

The BRN2 transcription factor controls the protein expression involved in cell motility and is overexpressed in melanoma. Gene mutations involved in cell signaling pathways lead to BRN2 overexpression, tumor formation and metastasis. Peptides derived from the DNA binding domain of transcription factors can compete for the transcription binding and regulate protein expression. In this work, the antitumor activity in vitro and in vivo of the peptide E24G, derived from the DNA-binding POU domain of the BRN2 transcription factor was investigated. This peptide was fragmented into two smaller peptides E12F and A12G, their antitumor activities were characterized and compared with E24G. The E24G at 1 mM significantly reduced cell motility in vitro of B16F10-Nex2 melanoma cells. E12F peptide also inhibited cell motility at a concentration eight times smaller than E24G in murine and human melanoma cells. We observed that the antitumor activity of both E24G and E12F peptides depends on the macropinocytosis displayed by tumor cells. Also, the E24G and E12F peptides induced an increase of the CDH13 expression in 50%, however the treatment with E12F increased the expression already after 12 h by 100%. In vivo assays showed that both peptides reduced the development of metastatic lung nodules without presenting toxicity to normal organs. Our results indicate that E12F and E24G peptides can restore normal expression of BRN2 target genes at the molecular level, inhibiting the cell motility. In addition, we confirmed that the peptide binds to the DNA binding site of the BRN2 transcription factor. Further studies will elucidate their mechanisms of antitumor activity, so far our results pointed out the potential application of E12F and E24G peptides as innovative treatments for metastatic melanoma.