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NK-92
NK-92 is a continuously growing cell line that has features and characteristics of natural killer (NK) cells that every person has circulating in the blood. Blood NK cells and NK-92 recognize "invaders" such as viruses and fungus. Most importantly, NK-92, like blood NK cells, can attack cancer cells as long as the tumor has not grown out of control. NK-92 cells were isolated and characterized by the laboratory of Dr. H. Klingemann - at that time at the British Columbia Cancer Control Agency in Vancouver, Canada.〔Gong J, Maki G, Klingemann H. Characterization of a human cell line (NK-92) with phenotypical and functional characteristics of activated natural killer cells. Leukemia 1994; 8: 652-58〕 The cells came from a patient who had a NK cell lymphoma, a rare lymphoma type. Although several other NK cell lines have been cloned, only NK-92 can be expanded to larger numbers and consistently kill tumor cells vigorously.〔Klingemann H-G. Development and testing of NK cell lines. In Lotze MT & Thompson AW (eds): Natural killer cells - Basic Science and Clinical applications 2010; pp169 – 75.〕 When NK-92 cells bind to a cancer or infected cell, they secrete ''perforin'' which punches holes in target cells followed by release of ''granzymes'' which induce ''apoptosis'' in the target cells. NK-92 cells also attack cancer cells through the Fas-Fas Ligand system and are capable of producing cytokines that by themselves can kill cancer cells (such as TNF-alpha) or stimulate and expand other immune cells such as interferon.〔Maki G, Klingemann HG, Martinson JA, Tam YK. Factors regulating the cytotoxic activity of the human natural killer cell line, NK-92. J Hematother Stem Cell Res 2001;10:369-83〕
Over the past 2 decades (the cell line was established in 1992) researchers worldwide have used NK-92 cells to test their anti-cancer activity in mouse models.〔Tam YK, Miyagawa B, Ho VC, Klingemann H-G. Immunotherapy of malignant melanoma in a SCID mouse model using the highly cytotoxic natural killer cell line NK-92. J Hematother 1999; 8: 281-90〕 and also use it as a model to learn more about the biology of NK cells. NK-92 cells are a very close match with blood NK cells: they express on their surface the characteristic CD56 antigen and are negative for CD3 which is typical for T-lymphocytes. In addition they express a number of adhesion molecules such as ICAM and LFA that facilitates binding to infected and cancer cells. Blood NK cells, NK-92 recognize "invaders" or foreign cells only if those cells do not express self MHC molecules. This means if cancer cells maintain their MHC phenotype they may go unnoticed by NK cells but not of NK-92 cells. The reason for this difference in target cell recognition relates to the fact that NK-92 cells do not express killer cell immunoglobulinlike receptors (KIR) that are negative regulators of NK cell activity through interaction with self-MHC.
==NK-92 in clinical trials==
Three phase I clinical trials, led by experts in adoptive immunotherapy of cancer, have so far yielded excellent results. Hans Klingemann, MD, PhD and Sally Arai, MD completed the US trial at Rush University Medical Center (Chicago) in renal cell and melanoma patients,〔Arai S, Meagher R, Swearingen M, et al. Infusion of the allogeneic cell line NK-92 in patients with advanced renal cell cancer or melanoma: a phase I trial. Cytotherapy 2008;10:625-32〕 and Torsten Tonn, MD and Oliver Ottmann, MD completed the European trial at the University of Frankfurt in patients with various solid and hematological malignancies.〔Tonn T, Becker S, Esser R, Schwabe D, Seifried E. Cellular immunotherapy of malignancies using the clonal natural killer cell line NK-92. J Hematother Stem Cell Res 2001;10:535-44.〕 Armand Keating, MD is completing the last cohort of patients in the Canadian trial at Princess Margaret Hospital in Toronto in lymphoma patients after autologous bone marrow transplants. In all three programs, NK-92 cells were administered as a simple intravenous infusion, dosed two or three times per treatment course and given in the outpatient setting.
Most importantly, there were no grade ≥ 2 side-effects during or after the short infusion of NK-92 cells. The maximum dose given in the Frankfurt trial was 10e10 cells/me2 x 2 infusions, each 48 hours apart. The Chicago study infused NK-92 at a maximum of 5 x 10e cells/me2 x 3 infusions, each 48 hours apart. This was not the MTD but rather the number of cells that could be expanded in culture bags over a three-week culture period. Alternative cell expansion technologies (bioreactors) will make it possible to further expand the numbers of NK-92 on a smaller 'footprint'. Anecdotal reports of antitumor activity in the two completed phase I studies have been observed in 6/11 patients with renal cancer, 3/4 patients with lung cancer, and 1/1 patient with melanoma, all with very advanced disease. In addition to disease stabilization and regression of metastases in lung and lymph nodes, the severe pain associated with tumor metastases in several patients, which had been refractory to standard chemotherapy, was remarkably lessened. The ongoing trial in Toronto treats patients with lymphoma who have relapsed after an autologous stem cell transplant. Preliminary results suggest a significant benefit in several patients.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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