Myeloid-derived suppressor cells secrete IL-10, IL-6, TNF-Alfa, IL-1 beta, COX-2, IFN-Gama,HIF-1 Alfa and ROS, skew the CD4+ T Cells to Tregs and suppress the antitumour immunity of CD4+, CD8+, and NK cells, resulting in the suppressive and tolerogenic environment and M2 phenotypic polarisation of tumour-associated macrophages favouring tumour progression. The gene discussed is PTGS2; the disease is neoplasm.