Search

Acute myeloid leukemia (AML) cells induce, in vitro, NK cell abnormalities (NKCAs) including apoptosis and activating receptor down-regulation. The potential negative impact of AML cells on the therapeutic efficacy of NK cell-based strategies prompted us to analyze the mechanisms underlying NKCAs and to develop approaches to protect NK cells from NKCAs. NKCA induction by the AML leukemia cells target a subpopulation of peripheral blood NK cells and is interleukin-2 independent but is abrogated by a long-term culture of NK (LTNK) cells at 37°C. LTNK cells displayed a significantly enhanced ability to damage AML cells in vitro and inhibited the subcutaneous growth of ML-2 cells grafted into CB17 SCID mice. Actinomycin D restored the susceptibility of LTNK cells to NKCAs while TAPI-0, a functional analog of the tissue inhibitor of metalloproteinase (TIMP) 3, inhibits ML-2 cell-induced NKCAs suggesting that the generation of NK cell resistance to NKCAs involves RNA transcription and metalloproteinase (MPP) inactivation. This conclusion is supported by the reduced susceptibility to AML cell-induced NKCAs of LTNK cells in which TIMP3 gene and protein are over-expressed. This information may contribute to the rational design of targeted strategies to enhance the efficacy of NK cell-based-immunotherapy of AML with haploidentical NK cells.

The goal of this study was to determine the frequency of HLA class II antigen expression in colorectal carcinoma (CRC) tumors, its association with the clinical course of the disease, and the underlying mechanism(s). Two tissue microarrays constructed with 220 and 778 CRC tumors were stained with HLA-DR, DQ, and DP antigen-specific monoclonal antibody LGII-612.14, using the immunoperoxidase staining technique. The immunohistochemical staining results were correlated with the clinical course of the disease. The functional role of HLA class II antigens expressed on CRC cells was analyzed by investigating their in vitro interactions with immune cells. HLA class II antigens were expressed in about 25% of the 220 and 21% of the 778 tumors analyzed with an overall frequency of 23%. HLA class II antigens were detected in 19% of colorectal adenomas. Importantly, the percentage of stained cells and the staining intensity were significantly lower than those detected in CRC tumors. However, HLA class II antigen staining was weakly detected only in 5.4% of 37 normal mucosa tissues. HLA class II antigen expression was associated with a favorable clinical course of the disease. In vitro stimulation with interferon gamma (IFNγ) induced HLA class II antigen expression on two of the four CRC cell lines tested. HLA class II antigen expression on CRC cells triggered interleukin-1β (IL-1β) production by resting monocytes. HLA class II antigen expression in CRC tumors is a favorable prognostic marker. This association may reflect stimulation of IL-1β production by monocytes.