Local inhibition of natural killer cell activity promotes the progressive growth of intraocular tumors.
OBJECTIVE
To study the effect of aqueous humor (AH)-mediated inhibition of natural killer (NK) cell activity on intraocular tumor progression.


METHODS
Two NK-sensitive tumors, RMA-S lymphoma and OCM-3 uveal melanoma, were tested in vitro for susceptibility to NK cell-mediated lysis in the presence or absence of AH in conventional cytotoxicity assays. Various numbers of RMA-S and OCM-3 tumor cells were injected either subcutaneously or intracamerally into C57BL/6 severe combined immunodeficiency mice and BALB/c nude mice respectively and tumor growth was monitored. The role of NK cell-mediated cytotoxicity in controlling tumor growth was confirmed by depleting NK cells in severe combined immunodeficiency mice by administering anti-asialo GM1 antibodies before subcutaneous tumor injection.


RESULTS
AH significantly inhibited NK cell-mediated lysis of RMA-S and OCM-3 tumor cells in vitro and in vivo. NK sensitive RMA-S (1 x 10(4) cells) and OCM-3 tumors (1 x 10(6), 5 x 10(6) cells) were rejected after subcutaneous injection in C57BL/6 mice, whereas the same or even lower numbers of cells grew progressively in the eye. In vivo NK cell depletion resulted in progressive growth of subcutaneously injected RMA-S tumors at a dose rejected by mice with normal NK cell activity.


CONCLUSIONS
AH inhibits NK cell activity in vitro and within the interior of the eye and prevents the rejection of NK-sensitive intraocular tumors.
Apte
R S
RS
Graduate Program in Immunology, University of Texas Southwestern Medical Center, Dallas 75235-9057, USA.
Mayhew
E
E
Niederkorn
J Y
JY
D000818:Animals; D001082:Aqueous Humor / Q000502:physiology*; D002455:Cell Division; D003603:Cytotoxins / Q000502:physiology; D018450:Disease Progression; D005123:Eye; D005134:Eye Neoplasms / Q000473:pathology*; D006084:Graft Rejection; D007267:Injections; D007279:Injections, Subcutaneous; D007694:Killer Cells, Natural / Q000502:physiology*; D051379:Mice; D008807:Mice, Inbred BALB C; D016513:Mice, SCID; D009368:Neoplasm Transplantation; D011817:Rabbits; D014407:Tumor Cells, Cultured
D003603:Cytotoxins