MAPK1 and cancer: In conclusion, our finding that CHST15, which seems to be unfavorable for most human cancers, is a positive target of ERK in oncogenic conditions, and is transcriptionally reversed by the HOXB8 transcription factor gain of function, underlines the relevance of the chicken MEK1ca/HOXB8 in vivo model to identify new key oncogenes and tumor suppressors, pertinent in human pathologies.