DKK1 and neoplasm: DKK1, one of the top four downregulated genes in our study, has been found to signal to myeloid-derived suppressor cells in order to promote tumor growth in murine syngeneic models and to signal to CD4+ T cells to inhibit Th1 polarization and suppress the secretion of IFN-γ [10], and RPPH1, another downregulated gene, promotes EMT and macrophage M2 polarization in colorectal cancer [11].