Do locally advanced and metastatic human epithelial cancers evolve in ‘placental/decidual-like microenvironments’?

Successful tumor microenvironments eventually kill the host. They are not only meant to nourish and protect tumor development, but to give them the right “soil” for perpetual malignant properties such as tissue invasion and metastasis. This can only be achieved if cancers avoid immune vigilance. A similar situation occurs in mammalian placental pregnancy but feto-maternal tolerance is required for a correct physiological process only until birth. Once a cancer microenvironment has acquired the genetic and epigenetic “placental immune editing switches” (PIES) phenotype, it seems likely that it will keep them “available”, whenever needed, for the rest of its development, because it gives cellular clones a competitive advantage to pass unnoticed by the host’s immune system. This allows primary cancers and their metastasis to continue growing in spite of new and changing antigenic landscapes.