CEACAM1 and lymphoma: However, PtdSer is present in multiple viable tumor cells, and its exposure is significantly increased on the surface of tumor cells or tumor cell-derived microvesicles in the tumor microenvironment, which have intrinsic immunosuppressive properties and facilitate tumor growth and metastasis.60 61 Our data showed that lymphoma cells expressed lower levels of Gal-9 and CEACAM1, and only moderately expressed PtdSer (online supplemental figure S3).