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Production by Invariant NK T Cells in Advanced Cancer1


*
Cancer Biology Program, Hematology/Oncology Division, Department of Medicine, Beth Israel-Deaconess Medical Center and Harvard Medical School, Boston, MA 02215;
Pharmaceutical Research Laboratory, Kirin Brewery, Gunma, Japan; and
Cancer Immunology and AIDS, Dana-Farber Cancer Institute, Boston, MA 02115
| Abstract |
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chain specific for the MHC class I-like CD1d protein.
These invariant NK T cells can regulate diverse immune responses in
mice, including antitumor responses, through mechanisms including rapid
production of IL-4 and IFN-
, but their physiological functions
remain uncertain. Invariant NK T cells were markedly decreased in
peripheral blood from advanced prostate cancer patients, and their ex
vivo expansion with a CD1d-presented lipid Ag (
-galactosylceramide)
was diminished compared with healthy donors. Invariant NK T cells from
healthy donors produced high levels of both IFN-
and IL-4. In
contrast, whereas invariant NK T cells from prostate cancer patients
also produced IL-4, they had diminished IFN-
production and a
striking decrease in their IFN-
:IL-4 ratio. The IFN-
deficit was
specific to the invariant NK T cells, as bulk T cells from prostate
cancer patients produced normal levels of IFN-
and IL-4. These
findings support an immunoregulatory function for invariant NK T cells
in humans mediated by differential production of Th1 vs Th2 cytokines.
They further indicate that antitumor responses may be suppressed by the
marked Th2 bias of invariant NK T cells in advanced cancer
patients. | Introduction |
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chain, generated by precise
V
14-J
281 rearrangements with no N region diversity. These
invariant NK T cells are CD4+ or
CD4-CD8- and they
specifically recognize the MHC class I-like CD1d protein (1, 2). Humans similarly have a population of
CD161+, CD4+, or
CD4-CD8-, CD1d-reactive T
cells that use a homologous invariant TCR
chain (V
24-J
Q)
associated with V
11-encoded TCR
chains (3, 4, 5, 6). The
physiological CD1d-presented Ag recognized by these cells has not been
identified, but human and mouse invariant NK T cells can be
specifically activated by a CD1d-presented synthetic glycolipid,
-galactosylceramide
(
-GalCer),3 which
was originally isolated from marine sponges in a screen for novel
antitumor agents (7, 8). Invariant NK T cells are the source of IL-4 produced rapidly in response to T cell activation in vivo by anti-CD3 and they may contribute to the initiation of Th2-like immune responses (9, 10, 11, 12). These cells are also required for the induction of immune tolerance in response to Ags administered into the anterior chamber of the eye, an immune-privileged site (13), and for induction of allograft tolerance (14, 15). Reductions in the number of circulating NK T cells and loss in their IL-4 production have been reported in certain human and murine autoimmune diseases, including type 1 diabetes mellitus, that are linked to relative increases in cellular Th1-like immune responses vs humoral Th2 responses (16, 17, 18, 19, 20). Recent murine studies further suggest that NK T cells can suppress antitumor immune responses (21, 22).
In contrast to this evidence for roles in promoting Th2 immunity and
tolerance, other data strongly support a role for NK T cells in
stimulating Th1-like responses. Results in several murine infection
models indicate that invariant NK T cells augment protective cellular
Th1-like immune responses (23, 24, 25, 26, 27). Studies with J
281
knockout mice, which specifically lack invariant NK T cells, indicate
that invariant NK T cells contribute to antitumor immunity and the
antitumor effects of IL-12 (28, 29, 30, 31). Moreover, in vivo
stimulation of invariant NK T cells with
-GalCer stimulates IL-12
production, NK cell activation, and augments antitumor responses
(32, 33, 34, 35). Murine and human invariant NK T cells may also
have NK-like cytotoxicity and can function as CD1d-specific cytolytic T
cells (36, 37, 38), although it is not clear to what extent
they function in vivo as direct effectors of antitumor responses vs
functioning through cytokine production and activation of other
effector cells.
Although these studies in murine model systems support an
immunoregulatory function for invariant NK T cells, the role they play
in augmenting or suppressing human immune responses, and in particular
antitumor immune responses, remains to be determined. One study found
that CD161+V
24+ T cells
were decreased in patients with melanoma, but could be activated by
-GalCer (38). We report in this study that invariant NK
T cells are markedly decreased in patients with advanced prostate
cancer. Moreover, although the remaining invariant NK T cells could
produce high levels of IL-4, they were strikingly deficient in their
production of IFN-
. These findings strongly support an
immunoregulatory function for invariant NK T cells in human cancer. The
marked Th2-like bias of invariant NK T cells in advanced cancer further
indicates that this immunoregulatory function is compromised and may
contribute to ineffective endogenous antitumor responses and decreased
responses to vaccines and other immunotherapies.
| Materials and Methods |
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Patients in this study had advanced androgen-independent prostate cancer (39, 40). All were treated previously with androgen ablation therapy by orchiectomy or administration of a leutinizing hormone releasing hormone agonist. At the time of study, all had positive bone scans and rising levels of prostate-specific Ag (PSA; >10 ng/ml), indicative of progressive metastatic disease. All but one patient had not received cytotoxic chemotherapy. Prostate cancer patients in remission were similarly treated with androgen ablation therapy, but had negative bone scans and stable low (<10 ng/ml) levels of PSA.
In vitro expansion of V
24-positive T cells
Peripheral blood (1020 ml) was drawn in heparin-containing
tubes from healthy donors and prostate cancer patients, after obtaining
informed consent. PBMCs were isolated using Ficoll-Paque (Amersham
Pharmacia, Uppsala, Sweden) and V
24-positive T cells were stained
with an anti-V
24 mAb (C15; Coulter, Miami, FL) (4)
followed by a goat anti-mouse IgG (H + L) FITC conjugate
(Kirkegaard & Perry Laboratories, Gaithersburg, MD), and were sorted by
high speed FACS (Modular Flow FACS; Cytomation, Fort Collins, CO).
Autologous PBMCs were irradiated (5000 rads) and used as APCs. The
FACS-purified V
24+ cells were initially
cocultured in 96-well flat-bottom plates (
20,000 per well) with
equal numbers of autologous irradiated PBMCs in the presence of
-GalCer (50 ng/ml, KRN7000; Kirin Brewery, Gunma, Japan) and rIL-2
(100 U/ml; National Cancer Institute, Bethesda, MD). Cultures were then
gradually expanded into 24-well plates, using the same medium. In some
cultures, human rIL-12 (1 ng/ml; Genetics Institute, Cambridge, MA) was
added during the last week of culture.
Flow cytometry
Phenotypic analysis of
-GalCer expanded cells was performed
by two- or three-color flow cytometry after 34 wk in culture.
Previous reports have shown that dual staining for V
24 and V
11 is
a marker of invariant NK T cells, as V
24 and V
11 are used very
infrequently by bulk T cells (4, 5, 6). Abs used were
anti-V
24 PE, anti-V
11 FITC, anti-CD8
PE
(Immunotech, Westbrook, ME), anti-CD3 CyChrome, anti-CD161 PE,
and anti-CD4 CyChrome (BD PharMingen, La Jolla, CA). As described
previously (5, 36),
1 x 106
cells were suspended in 50 µl of FACS buffer (PBS with 1% FBS and
0.1% NaN3) in single wells of 96-well plates.
Nonspecific Ab binding was blocked by preincubating cells with 10%
human serum for 15 min on ice. Abs were then added to cell suspensions
and incubated for 20 min on ice. Cells were then washed twice with FACS
buffer, and analyzed using a FACScan (BD Biosciences, Mountain View,
CA) with CellQuest Software.
The analysis of invariant NK T cells in freshly isolated PBMC from
healthy donors and cancer patients used an additional invariant
TCR-specific mAb, 6B11, which was raised in CD1d knockout mice against
a cyclic peptide based upon the human invariant TCR
chain, CDR3
(M. A. Exley et al., manuscript in preparation). In these
experiments, cells were stained with 6B11-FITC and anti-V
24-PE
(which did not cross-compete) to detect cells expressing the invariant
TCR. Due to the low frequency of these cells in cancer patients,
between 105 and 106 total
cells were analyzed.
Measurement of cytokine production and CD1d reactivity
For cytokine production, 1 x 105
cells/well in 96-well plates were cocultured with an equal number of
CD1d or mock-transfected C1R cells in RPMI 1640 medium with 10% FBS,
20 U/ml IL-2, and 1 ng/ml PMA, as described previously
(5). Cellular responses to CD1d were blocked with an
anti-CD1d Ab, 51.1 at 10 µg/ml (5, 41). Supernatants
were collected at 48 and 72 h for IL-4 and IFN-
measurements,
respectively. Released cytokine levels were determined in
triplicates by capture ELISA with matched Ab pairs in relation to
cytokine standards (Endogen, Cambridge, MA). The limit of detection
range of these assays for both IFN-
and IL-4 was 1050 pg/ml.
| Results |
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Invariant NK T cells in the peripheral blood of healthy donors and
cancer patients were quantitated by two-color flow cytometry with a
V
24 mAb and a V
11 mAb or the 6B11 mAb against the invariant
V
24-J
Q TCR (M. A. Exley et al., manuscript in
preparation). Invariant NK T cell lines, generated by
-GalCer
expansion of V
24+ T cells from healthy donors,
were reactive with V
24, V
11, and 6B11 mAbs (Fig. 1
, NK T cell line). The observation that
V
11 was expressed by virtually all of the
-GalCer-expanded
V
24+ T cells from this and multiple other
healthy donors (see below) further indicated that this V
was
necessary to generate
-GalCer-reactive invariant NK T cells.
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24+V
11+-double-positive
T cells were found in the peripheral blood of healthy donors in numbers
that were comparable with
V
24+6B11+ cells,
consistent with a large fraction of
V
24+V
11+ cells being
invariant NK T cells (Fig. 1
24+6B11+ cells in a
series of healthy donors was 0.11%. Smaller numbers of
V
24+V
11+ T cells were
found in the peripheral blood of advanced prostate cancer patients.
Moreover, there were no detectable
V
24+6B11+ cells in five
of six patients examined (Fig. 1Expansion of invariant NK T cells from healthy donors
Due to the small numbers of invariant NK T cells in peripheral
blood, one round of ex vivo expansion was conducted to further assess
the frequency and function of these cells. Invariant NK T cells from
healthy donors and advanced prostate cancer patients were isolated from
peripheral blood through an initial FACS purification with a
V
24-specific mAb, followed by selective expansion in vitro for 34
wk with
-GalCer and autologous-irradiated PBMCs as a source of APCs.
T cells were then analyzed by dual staining with V
24 and V
11 or
6B11 mAbs.
FACS-purified V
24+ T cells stimulated in vitro
with a T cell mitogen, PHA, yielded only a minor population of
V
24+V
11+ T cells,
which varied in number with different donors (Fig. 2
A). In contrast, stimulation
of the purified V
24+ T cells from healthy
donors with
-GalCer and autologous-irradiated PBMCs yielded a major
V
24+V
11+ population
(Fig. 2
A, 94.4% of total cells). Additional phenotypic
analyses of these
-GalCer-expanded
V
24+V
11+ T cells from
a series of healthy donors demonstrated major
CD4+ and
CD4-CD8- populations, and
showed that the majority from each donor (>70%) expressed CD161 (data
not shown).
|
-GalCer-expanded V
24+
V
11+ T cells from healthy donors were assessed
for CD1d recognition and cytokine production. Consistent with many of
the cells being CD1d-reactive invariant NK T cells, the cells produced
substantial quantities of both IL-4 and IFN-
in response to
CD1d-transfected C1R cells, but not mock-transfected C1R cells (Fig. 2Decreased expansion of invariant NK T cells from advanced prostate cancer patients
Invariant NK T cells from patients with advanced
androgen-independent prostate cancer were examined similarly. Relative
to the healthy donors, there was a consistent decrease of
5-fold in
the total number of cultured cells recovered from patients with
advanced androgen ablation refractory prostate cancer (not shown).
Moreover, there was a marked decrease in the fraction of expanded cells
that were
V
24+V
11+-invariant NK
T cells (Fig. 3
A, 98.5 vs
13.6% invariant NK T cells in a healthy donor and androgen ablation
refractory prostate cancer patient, respectively). Also shown are
-GalCer expanded-V
24+ T cells from an
androgen ablation-treated prostate cancer patient in remission (75%
invariant NK T cells), indicating that the androgen ablation therapy
did not account for the decreased expansion of invariant NK T
cells.
|
24+V
11+-invariant NK
T cells (mean of 10% from prostate cancer patients vs >80% from
healthy donors; Fig. 3
24 and
V
11 or 6B11 staining in peripheral blood of the advanced prostate
cancer patients, but other factors, including decreased proliferation
or increased apoptosis during the in vitro stimulations, could have
contributed to the lower recovery. In contrast, the recovery of
V
24+ V
11+-invariant
NK T cells from prostate cancer patients receiving androgen ablation
therapy, but who were in remission, was closer to the healthy donors
(Fig. 3
Loss of IFN-
production by invariant NK T cells from cancer
patients
CD1d-specific responses and cytokine production by
-GalCer-expanded invariant NK T cells from prostate cancer patients
were next assessed. Similar to healthy donors, prostate cancer
patient-derived invariant NK T cell lines proliferated (data not shown)
and produced IL-4 in response to CD1d-transfected cells (Fig. 4
A, left panel).
Basal IL-4 production was also observed in some lines, but the level
was augmented by CD1d. In contrast to the IL-4 results, production of
IFN-
was markedly reduced relative to invariant NK T cells from a
healthy donor (Fig. 4
A, right panel). Analyses of
CD1d-stimulated IL-4 vs IFN-
production by
-GalCer-expanded
invariant NK T cell lines from a series of advanced prostate cancer
patients and healthy donors confirmed the decrease in IFN-
production by the cells derived from prostate cancer patients (Fig. 4
B, left panel). As this decrease could reflect
differences in the number of invariant NK T cells in the lines and
fraction of these cells responding to the CD1d stimulus, the ratio of
IFN-
to IL-4 produced by each line was assessed. This showed a
striking loss of IFN-
relative to IL-4, with a difference of
50-fold in the IFN-
:IL-4 production ratios between the prostate
cancer- and healthy donor-derived NK T cell lines (Fig. 4
C).
|
production was common to
other T cell populations, bulk peripheral blood T cells from advanced
androgen-independent prostate cancer patients and healthy donors were
stimulated in vitro with PHA. The results showed that IFN-
production by bulk T cells from prostate cancer patients was intact
(Fig. 4
:IL-4
ratios observed in the cells from prostate cancer patients vs healthy
donors (Fig. 4
production in the invariant NK T cell
population from advanced prostate cancer patients.
As invariant NK T cells may contribute to the antitumor effects of
IL-12, it was next determined whether these cancer patient-derived
cells could respond to IL-12. Prostate cancer-derived invariant
NK T cells were treated with IL-12 (1 ng/ml) during the last week of
culture to determine whether they could respond to this cytokine. The
IL-12-treated cells showed a marked increase in IFN-
production, and
had ratios of IFN-
:IL-4 production that were comparable with those
in the healthy donors (Fig. 4
C, cancer + IL-12).
| Discussion |
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) in the remaining cells. Moreover, this Th2 bias
may impede both endogenous antitumor responses and responses to tumor
vaccines and other forms of immunotherapy that rely on stimulating
strong Th1 immune responses. Together with a report showing decreased
numbers of V
24+ CD161+ T
cells in melanoma (38), this suggests that loss of
invariant NK T cell function will be a general finding in advanced
cancer.
An increase in IL-4 production relative to IFN-
by invariant NK T
cells was reported previously in mice after multiple treatments with
-GalCer, and was associated with Th2-biased immune responses
(43, 44). However, this study provides the first evidence
in humans or mice for the development of a Th2 bias (high IL-4:IFN-
ratio) by invariant NK T cells in a physiological or disease setting. A
previously described functional change in invariant NK T cells was loss
of IL-4 production in type 1 diabetes mellitus, which was linked to
Th1-biased immune responses and disease progression in identical twins
discordant for the disease (20). Although the Th1 and Th2
biases observed previously in diabetes and in this study in cancer may
be pathological, they likely reflect an extreme in the spectrum of
invariant NK T cell responses to normal immunological stimuli.
Therefore, these findings strongly support a physiological role for
human invariant NK T cells in regulating both Th1 and Th2 immune
responses through mechanisms including selective local production of
Th1 or Th2 cytokines.
Activated invariant NK T cells express IL-12 receptors and can induce
dendritic cells to produce IL-12 through IFN-
production and
CD40/CD40 ligand interactions (32, 33). The IFN-
loss
observed here in prostate cancer patients appeared to be intrinsic to
the invariant NK T cells, as substitution of
-GalCer-treated
allogeneic-irradiated PBMCs from healthy donors did not restore IFN-
production (data not shown). Therefore, the restoration of IFN-
production by exogenous IL-12 suggests a defect in the ability of
invariant NK T cells from cancer patients to induce dendritic cell
IL-12 production, a hypothesis that is currently being tested. In any
case, these results indicate that invariant NK T cells may be an
important target of IL-12 treatment in advanced cancer clinical trials
(45). Current efforts are focused on development of a
clinical trial of autologous in vitro-expanded and IL-12-activated
invariant NK T cells to test whether these cells can augment endogenous
antitumor responses or responses to tumor vaccines.
| Acknowledgments |
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| Footnotes |
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2 Address correspondence and reprint requests to Dr. Steven P. Balk or Dr. Mark A. Exley, Department of Medicine, Beth Israel-Deaconess Medical Center, Harvard Institutes of Medicine Building, Room 1050, 330 Brookline Avenue, Boston, MA 02215. E-mail address: sbalk@caregroup.harvard.edu or mexley{at}caregroup.harvard.edu ![]()
3 Abbreviations used in this paper:
-GalCer,
-galactosylceramide; PSA, prostrate-specific Ag. ![]()
Received for publication June 11, 2001. Accepted for publication July 26, 2001.
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