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-Expressing Tumor Cells Enhance Generation and Promote Survival of Tumor-Specific CTLs
*
Department of Surgery, University of Pittsburgh School of Medicine, and University of Pittsburgh Cancer Institute, Pittsburgh, PA 15261; and
Department of Dermatology, J. Gutenberg-University, Mainz, Germany
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Abstract |
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 Top Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
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gene therapy has been successfully applied in several tumor
models. Our studies involving the murine colorectal adenocarcinoma cell
line MC38 confirm that IFN- transduction of a poorly immunogenic
tumor cell reduces tumorigenicity and leads to long-lasting tumor
immunity. To investigate the effect of IFN- transduction on the
development of antitumor immune responses, we restimulated splenocytes
from MC38-immune mice in vitro. Detection of MC38-specific cytotoxicity
was markedly enhanced when murine IFN-2-transduced MC38
(MC38-IFN) or CD80-transduced MC38 (MC38-CD80) was used for
restimulation compared with wild type (MC38-WT) or neomycin resistance
gene-transduced MC38 (MC38-Neo) cells. MC38-specific CD8+
CTL line and clone were established from splenocytes of mouse immunized
with MC38-IFN. Stimulation with MC38-IFN as well as MC38-CD80
enhanced the proliferation of MC38-specific CTLs in vitro much more
effectively than stimulation with WT or MC38-Neo (p
< 0.05). Coincubation of MC38-specific CTLs with MC38-IFN or
MC38-CD80 resulted in significantly less DNA fragmentation (8.0% and
12.8%, respectively) compared with coincubation of the CTLs with
MC38-WT (43.5%; p < 0.001) or MC38-Neo cells
(38.1%; p < 0.003). These results suggest that
prevention of apoptotic cell death in tumor-specific CTLs may be one
mechanism by which IFN--expressing tumor cells can promote the
generation of antitumor immunity. The effect of IFN- on CTLs appears
to be similar to that of CD80, which also prevents apoptotic cell death
after stimulation of T lymphocytes. |
Introduction |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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and -
), which were produced in large amounts
during the early phase of viral infection, and type II IFN (later
IFN-
), which was considered to be more closely associated with
specific immune reaction. The importance of IFN- for the development
of cellular immune responses is now firmly established. In contrast,
the role of type I IFN in the modulation of T cell immunity has been
only partially clarified. IFN-, like IL-12 and IFN-, appears to
favor the proliferation of Th1 lymphocytes (2). Several
studies have emphasized the importance of IFN- for the generation of
CTLs. Mice lacking the type I IFN receptor by targeted deletion are
unable to mount a significant CTL response to lymphocytic
choriomeningitis virus (3). Importantly, exposure to type
I IFNs during a primary immune response promotes both the clonal
expansion and survival of CD8+ T cells responding
to specific Ag in vivo (4). In addition to the well-known
direct antiproliferative effects on tumor cells, type I IFNs have also
been found essential for the generation of effective CTL responses
against tumors. Neutralization of type I IFNs following injection of
potent neutralizing Abs impaired the generation of a tumor-specific CTL
response in murine models (5). These findings have been
supported by murine studies involving tumor cells transduced to express
IFN- (6). Inoculation into mice with IFN--expressing
tumor cells resulted in tumor rejection which was mediated by
CD8+ T cells (6) and associated with
the generation of long-lasting, tumor-specific memory. Type I IFN also
inhibit the expression of the IL-12 p40 chain in dendritic cells,
thereby limiting its production. IL-12, along with IL-18, is thought to
be required for development of IFN--producing
CD4+ T cells (7), and thus at level
IFN- feedback, it may inhibit APCs. Further investigations are
necessary to clarify the effects of IFN- on immune responses.
In a previous study, we reported that IFN- transduction of a poorly
immunogenic tumor cell reduces tumorigenicity and leads to long-lasting
tumor immunity (8). The studies reported here were
performed to understand in greater detail the effect of IFN- gene
transduction on the induction of tumor-specific cellular immune
responses. We show that IFN- expressed by tumor cells enhances the
generation of tumor-specific CTLs in vitro. Furthermore, we observed
that IFN--transduced tumor cells promote the survival of a
tumor-specific CTL line by preventing apoptosis. Both enhanced
generation and survival of specific CTLs were found at comparable
levels using tumor cells expressing the costimulatory molecule
CD80.
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Materials and Methods |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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Female C57BL/6 mice, 6–8 wk old, were purchased from Taconic Farms (Germantown, NY) and were used in experiments when they were 8–12 wk old. Animals were maintained in a specific pathogen-free facility (Central Animal Facility, University of Pittsburgh, Pittsburgh, PA).
Cell lines, culture medium, and reagents
The murine colorectal adenocarcinoma (MC38) (9), the methylcholanthrene-induced fibrosarcoma (MCA205) (both of C57BL/6 mouse origin), yeast artificial chromosome-1 (YAC-1)3 lymphoma cells, and p815 thymoma cells were obtained from Dr. S. A. Rosenberg (Surgery Branch, National Cancer Institute, Bethesda, MD). Cells were maintained in RPMI 1640 supplemented with 10% heat-inactivated FCS, 2 mM L-glutamine, 100 IU/ml penicillin, 100 µg/ml streptomycin, 10 mM HEPES buffer, 1 mM MEM sodium pyruvate, and 0.1 mM MEM nonessential amino acids (complete medium) in a humidified incubator with 5% CO2 at 37°C. Cells were determined to be free of mycoplasma contamination (detected by Mycoplasma T. C., Gene-Probe, San Diego, CA). All cell culture reagents were purchased from Life Technologies (Gaithersburg, MD).
A sheep polyclonal anti-mouse IFN--neutralizing Ab was a kind
gift of Dr. I. Gresser (Institut Gustav Roussy, Paris, France)
(10, 11). Sheep IgG and rat IgG (Sigma, St. Louis, MO)
were used as a control for sheep polyclonal anti-mouse
IFN--neutralizing Ab and rat anti-mouse CD8a Ab, respectively.
Flow cytometry was performed using FACScan (Becton Dickinson, San Jose,
CA). Anti-CD8 mAb was prepared from supernatant of the hybridoma
TIB-105 (American Type Culture Collection, Manassas, VA) and was used
for cytolytic assays and mixed lymphocyte/tumor proliferation assays to
block interaction between TCR on CTLs and MHC class I molecules on
tumor cells.
Retroviral construct and genetically modified tumor cell lines
A producer cell line for the retroviral vector SAM-mB7.1-EN was
kindly provided by Dr. P. Hwu (National Cancer Institute, Bethesda, MD)
(12). The construction and characterization of the
DFG-mIFN-2 retroviral vector has been described previously
(13). Retroviral transfection was performed using standard
approaches followed by selection of neomycin-resistant cells using the
neomycin analogue, G418 (obtained from Life Technologies, Gaithersburg,
MD), was done(14). The expression of mouse CD80 on the
surface of transduced tumor cells (MC38-CD80) was confirmed by flow
cytometry (FACScan, Becton Dickinson) using a mAb specific for mouse
CD80 (Becton Dickinson). The expression of mouse IFN-2 was confirmed
by ELISA (13). IFN-2-transduced MC38 cells
(MC38-IFN) produced 
80 ng (2400 U)/1 x
106 cells/48 h (8). Neomycin
resistance gene-transduced MC38 (MC38-Neo) cells used for control cell
line were obtained from Dr. Takashi Iwazawa (University of Pittsburgh).
Wild type (WT) MC38 (MC38-WT) cells or MC38-Neo did not express CD80 or
IFN-2. In vitro growth of these transduced cells was almost same as
that of WT cells (8). No difference between survival of WT
and that of genetically modified MC38 had been observed after
gamma-irradiation.
Generation and maintenance of tumor-specific CTLs
Hyperimmunized mice were generated by initial injection with
1 x 105 nonirradiated MC38-IFN on day 0.
Subsequently, tumor-free animals rejected a challenge with 3 x
105 MC38-WT on day 35 and also 1 x
106 MC38-WT on day 70. Splenocytes (1.5 x
106 cells/ml) from these hyperimmunized mice were
harvested on day 77 and were stimulated with WT or genetically modified
irradiated (10,000 rad) MC38 tumor cells (1.5 x
105 cells/ml). Seven days later, responder cells
(5 x 105 cells/ml) were restimulated with
the same MC38 cell lines (5 x 104 cells/ml)
as the first stimulation, irradiated (3000 rad) syngeneic naive
splenocytes (5 x 105 cells/ml), and 50
IU/ml of recombinant human IL-2 (Chiron, Emoryville, CA). Seven days
after the second stimulation, a cytolytic assay was performed against
MC38 cells and YAC-1 cells. An MC38-specific CTL line, referred to as
MK-1 cells (5 x 105 cells/ml), was
restimulated with MC38-CD80 (5 x 104
cells/ml) and syngeneic splenocytes (5 x
105 cells/ml) in the presence of 30 IU/ml of IL-2
every 7 days. Furthermore, limiting dilution was performed to establish
MC38-specific CTL clones. A total of 0.3 cells/well (96-well
round-bottom plate) of MK-1 cells was stimulated with MC38-CD80 (5
x 104 cells/ml) and syngeneic splenocytes
(5 x 105 cells/ml) in the presence of 30
IU/ml of IL-2 every 7 days, and clone cB4 was established. Phenotypic
analysis of these cells was performed using flow cytometry
(FACScan).
Cytolytic assays
Tumor-stimulated effector cells were assessed for their cytolytic activity against MC38, MCA205, and YAC-1 cells in triplicate in 4-h 51Cr-release assays. Target cells (1 x 106 cells/ml) were labeled with 100 µCi of Na2-51CrO4 (New England Nuclear-DuPont, Bedford, MA) for 1 h at 37°C. Labeled cells were washed and resuspended. A total of 1 x 104 target cells and various numbers of effector cells were plated in 200 µl of complete medium into each well of 96-well round-bottom plates. The 51Cr-release was measured after a 4-h incubation at 37°C. Percentage lysis was determined using the following formula: [(release in assay - spontaneous release) x 100]/(maximum release - spontaneous release). Maximum release was determined by lysis of labeled target cells with 1% Triton X-100. Spontaneous release was measured by incubating target cells in the absence of effector cells and was <20% of maximum release. Each experiment was performed at least three times.
Mixed lymphocyte/tumor proliferation assays
MK-1 cells or cB4 cells were rested for 14 days in complete
medium and IL-2 before the proliferation assay was performed. CTLs
(5 x 104 or 1 x
105 cells/well) were coincubated with 5 x
103 or 1 x 104
cells/well of WT or genetically modified gamma-irradiated (20,000 rad)
MC38 cells or irrelevant MCA205 tumor cell line in 200 µl of complete
medium in 96-well round-bottom plates for 3 days. To evaluate the
effect of IFN-, 2000 U/ml of murine IFN-2 or 15 µg/ml of
anti-IFN- Ab, which is capable of neutralizing over 5 x
104 U/ml of IFN- or, as a control, sheep IgG
was added to some wells. Anti-CD8 mAb (5 µg/ml) was also added to
block TCR-MHC interaction. Then, 1 µCi/well of
[3H]TdR was added to each well. After an 18-h
incubation, all cells were harvested onto glass fiber filter mats and
[3H]TdR uptake was assessed by liquid
scintillation counting. Experiments were performed three or four times
in triplicate.
DNA fragmentation (JAM) assays
MC38-specific CTLs (target cells) were labeled with
[3H]TdR as previously described
(15) and cocultured with or without tumor cells at
indicated tumor to CTL ratios. Exogenous murine IFN-2 (2000 U/ml)
and anti-IFN--neutralizing Ab (15 µg/ml) were used to evaluate
the effects of IFN-. After 8 h, the cells were harvested onto
glass fiber filter mats, and nuclear DNA-bound radioactivity was
determined by liquid scintillation counting. Nuclear DNA-bound
radioactivity of the 5 x 103 CTLs incubated
for 8 h without tumor cell was usually between 10,000 and 15,000
cpm. The nuclear contents of radiolabeled DNA are decreased as a result
of DNA fragmentation associated with apoptotic cell death. The
percentage of DNA fragmentation was calculated using the following
formula (15): percentage DNA fragmentation =
[(DNA-bound activity without tumor) - (DNA-bound activity
coincubated with tumor)] x 100/(DNA-bound activity without tumor).
Experiments were performed at least three times.
Statistical analyses
Significance was assessed by Student’s t test. The difference between groups was considered statistically significant when the p value was <0.05.
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Results |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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- and CD80-transduced MC38 cells generate MC38-specific
CTLs in vitro from IFN--transduced MC38-immunized mice
Mice hyperimmunized to MC38 as a result of inoculation of
MC38-IFN and two subsequent rechallenges with a 3- to 10-fold
greater number of MC38-WT were sacrificed, and splenocytes were
harvested. Restimulation was performed twice in vitro with MC38-WT,
-Neo, -CD80, or -IFN and syngeneic splenocytes to assess the
induction of tumor-specific cytotoxicity as described above in
Materials and Methods. Cytotoxicity was determined in
51Cr-release assays using MC38 and the
lymphokine-activated killer-sensitive YAC-1 as targets. When MC38-WT or
-Neo cells were used as stimulator cells, comparable cytolytic activity
was noted for both MC38 and YAC-1 cells (Fig. 1
, A and B).
However, specific cytolysis for MC38 cells was clearly detected when
MC38-CD80 (49.80% vs MC38 and 18.18% vs YAC-1; E:T = 40) or
MC38-IFN (50.01% vs MC38 and 15.87% vs YAC-1; E:T = 40) were
used as stimulator cells (Fig. 1, C and D).
IFN- and CD80 transduction appears to enhance the generation of
specific CTLs in vitro.
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-transduced tumor cells was
extended to the murine methylcholanthrene-induced fibrosarcoma cell
line MCA205. Restimulation of splenocytes harvested from MCA205-immune
mice with MCA205 transduced with IFN- or CD80 also led to
tumor-specific cytolytic effectors (data not shown). In this model, we
detected more nonspecific cytolytic activity due to
lymphokine-activated killer activity against YAC-1 cells. Characterization and specificity of MC38-specific CTLs
To further investigate the mechanism by which IFN- expression
of MC38 cells leads to the generation of tumor-specific CTLs, we
generated an MC38-specific CTL line. Splenocytes harvested from
hyperimmune mice were maintained by weekly stimulation with MC38-CD80,
syngeneic splenocytes, and IL-2. After a third stimulation,
cytotoxicity assays were performed against MC38-WT, YAC-1, and the
irrelevant fibrosarcoma MCA205 cells. These effector cells revealed
high specific cytolytic activity for MC38, but not for MCA205 and
YAC-1. Importantly, substantial lysis of MC38 was noted even at low E:T
ratios (40.46% at E:T = 1.25; Fig. 2A). After limiting dilution
cloning, an MC38-specific CTL clone, cB4, which demonstrated much
higher specific activity (30.90% at E:T = 0.16; Fig. 2B), was established. There was no difference in the killing
ratio of these CTLs against genetically modified MC38 compared to that
against MC38-WT. Phenotypic analysis was performed by flow cytometry,
confirming that the MC38-specific CTL lines designated as MK-1 were
CD8+ T lymphocytes (data not shown). Anti-CD8 mAb
efficiently blocked the killing activity of the MC38-specific CTL line
when more than 1 µg/ml of anti-CD8 mAb was used in the assay
(Fig. 2C). Furthermore, the epitope defined by this cB4 CTL
clone has now been identified by our colleague Dr. James C. Yang
(Surgery Branch, National Cancer Institute, Bethesda, MD). It is
restricted by H-2Db and represents the murine
homologue to cathepsin-L (H. Kazumasa, T. Tüting, M.T. Lotze, and J.
Yang, unpublished data).
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- and CD80-transduced MC38 cells enhance the proliferation
of specific CTLs
After establishment of the MC38-specific CTL line MK-1 and the CTL
clone cB4, we investigated the response to restimulation with WT or
genetically modified MC38 tumor cells as well as with the irrelevant
MCA205 tumor. We stimulated CTLs at a CTL-to-tumor ratio of 10 because
CTLs proliferate more efficiently in vitro at this ratio. Proliferation
of MK-1 CTLs was assessed by incorporation of
[3H]TdR during the final 18 h at the end
of day 4. The uptake of [3H]TdR by MK-1 cells
was significantly enhanced in cultures set up with MC38-IFN or
MC38-CD80 compared with cultures set up with MC38-WT
(p = 0.0215, MC38-IFN; or p
< 0.0001, MC38-CD80), MC38-Neo (p < 0.0001,
MC38-IFN and MC38-CD80), or MCA205 (Fig. 3A). Addition of exogenous
2000 U/ml IFN- resulted in an enhanced proliferative response of
MC38-specific CTL clone cB4 (p = 0.0040; Fig. 3B). When 15 µg/ml anti-IFN--neutralizing Ab, which
is capable of neutralizing over 5 x 104
U/ml of IFN-, was added in the assay,
[3H]TdR uptake by cB4 was decreased to almost
the same level as the uptake when CTLs were incubated with MC38-WT
(p = 0.0088). These results suggest that
IFN-- as well as CD80-transduced MC38 cells enhanced specific
CTL proliferation in vivo. Because anti-CD8 mAb abrogated the
proliferative response completely (p <
0.0004), TCR-MHC interactions seem to play a role (Fig. 3C).
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and MC38-CD80
CD80 signaling can indeed rescue CTLs from apoptotic cell death
following Ag-specific stimulation. The mechanism by which IFN-
enhances CTL proliferation is not clear. Therefore, we performed JAM
assays to determine whether IFN- would also protect tumor-specific
CTLs from apoptotic cell death. DNA fragmentation was detected when
MC38-specific CTLs were incubated with MC38-WT, but not with the other
irrelevant tumors (p < 0.01; Fig. 4A). Greater DNA fragmentation
was detected when MK-1 cells were incubated with MC38-WT (43.5%) or
MC38-Neo (38.1%) for 8 h at a tumor-to-CTL ratio of 80. In
contrast, incubation of MK-1 with MC38-IFN or MC38-CD80 resulted in
significantly less DNA fragmentation at the same tumor-to-CTL ratio
(8.0 or 12.8%, respectively; p < 0.003; Fig. 4B). Decreased levels of DNA fragmentation were also
detected following incubation with the irrelevant MCA205 tumor cells.
Taken together, these results suggest that IFN-- like
CD80-transduced MC38 cells are capable of enhancing the survival of
tumor-specific CTL by preventing tumor-specific apoptotic cell
death.
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protein was used to confirm the effects of
IFN- on preventing apoptosis of the CTLs. When CTLs were incubated
with MC38-Neo and exogenous murine IFN-2 (2000 U/ml), DNA
fragmentation of CTLs was significantly less than that of CTLs
incubated with MC38-Neo (p = 0.0111; Fig. 4
C). DNA fragmentation of CTLs incubated with MC38-IFN
was significantly increased when anti-IFN--neutralizing Ab (15
µg/ml) was added in the assay (p = 0.0116;
Fig. 4C). Exogenous IFN- has the same antiapoptotic
effect as shown for the transfectant in Fig. 4B. |
Discussion |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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into poorly immunogenic murine tumor cell
lines elicits a tumor-specific immune response in syngeneic
immunocompetent hosts (6). Tumor rejection in vivo appears
to depend upon a CD8+ cell-mediated immune
response (6). We studied the mechanisms by which IFN-
gene expression promotes tumor-specific cellular immune responses. The
effect of IFN--expressing MC38 tumor cells on tumor-specific CTLs
was studied in vitro using splenocytes harvested from MC38-immune mice
as responders. IFN- mediates up-regulation of MHC class I molecules
on tumor cells as well as enhanced killing activity of cytotoxic
effector cells (16). Belardelli (2) also
reported that IFN-, like IL-12, promotes T cell differentiation
toward a Th1 phenotype. Most importantly, type I IFNs can directly
enhance T cell proliferation and expression of a memory T cell
phenotype in vivo (4). Furthermore, Marrack et al.
(17) demonstrated that type I IFNs diminish activated T
cell apoptosis. Our results confirm and extend these observations. We
found that IFN--expressing MC38 tumor cells were able to efficiently
restimulate tumor-specific CTLs from splenocytes of MC38-immune mice in
vitro, while MC38-WT or MC38-Neo cells were not. Effective
restimulation of CTLs was observed at comparable levels when MC38-CD80
tumor cells were used. Furthermore, stimulation with MC38-IFN tumor
cells as well as MC38-CD80 tumor cells supported the proliferation of
MC38-specific CTLs in vitro. Stimulation with MC38-WT or MC38-Neo MC38
was significantly less effective. The CD80/CD28 interaction is critical
for survival, expansion, and delivery of signals allowing Ag-specific T
cell responses and effector function (18, 19, 20).
Cocultivation of CTLs with CD80-transduced tumor cells augmented the
specificity of tumor-reactive CTLs in long-term culture
(21). Proliferation of resting T cells in response to
parasite-infected cells was also found to be dependent on expression of
CD80 (22). Costimulatory signals delivered subsequent to
CD80/CD28 interactions prevents T cell apoptosis during target cell
lysis (23). Furthermore, ligation of CD28 by agonistic Abs
enhances the expression of Bcl-xL and prevents activation-induced cell
death (AICD) by apoptosis during activation of resting T cells
(24).
Premature apoptosis of effector cells is proposed to be one of the
major mechanism by which tumors escape host immune reactivity
(25). We hypothesized that IFN--expressing tumor cells
as well as CD80-expressing tumor cells were capable of inhibiting AICD,
which occurs after coincubation of MC38-specific CTLs with MC38-WT
tumor cells. This hypothesis was supported by DNA fragmentation assays,
which demonstrated that IFN--transduced tumor cells, like
CD80-transduced tumor cells, are able to prevent apoptotic cell death
of tumor-specific CTLs. Apoptosis of MC38-specific CTLs after
coincubation with MC38 tumor cells in these assays was very likely due
to AICD because only minimal DNA fragmentation was detected when CTLs
were incubated with the irrelevant MCA205, YAC-1, or p815 tumor cells.
Taken together, our results support the notion that IFN-, like CD80,
directly provides survival signals to tumor-specific CTLs.
We detected the DNA fragmentation of CTL at a tumor-to-CTL ratio of 80:1 but not 40:1. We believe that this reflects the physiological situation in vivo where a few CTLs attack a comparatively large amount of tumor cells. Our CTLs display a high specific cytolytic activity for MC38. Substantial lysis of MC38 was noted even at low E:T ratios. Because we performed 8-h JAM assays, MC38 cells were most likely killed by CTLs during the incubation. We presume that apoptosis of CTLs can be detected when CTLs are stimulated strongly by MC38 cells, i.e., when many tumor cells surround target CTLs. Therefore, a large number of MC38 cells may be required for CTL apoptosis to occur.
Because the natural IFN--producing cells have been recently
identified as type 2 dendritic cell precursors (26), these
cells provide stimuli of both IFN- and CD80. Together with this
identification, our findings suggest a novel role for these cells
during the effector phase of the immune response.
Cytokine gene-engineered tumor vaccines allow paracrine delivery of
cytokines into the tumor microenvironment, where they in turn elicit
antitumor effector cells (27, 28). We believe that this is
the first evidence that IFN- transduction of tumor cells
enhances proliferation of tumor-specific CTLs and prevents AICD of
the CTLs. Our results provide a scientific basis for the design of
clinical trials involving IFN- gene therapy for the treatment of
cancer. IFN- transduction with tumor cells should be considered for
application in cancer clinical trials.
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Acknowledgments |
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Footnotes |
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2 Address correspondence and reprint requests to Dr. Michael T. Lotze, Department of Surgery, University of Pittsburgh School of Medicine, Biomedical Science Tower, W1540, 200 Lothrop Street, Pittsburgh, PA 15261. E-mail address:
3 Abbreviations used in this paper: YAC-1, yeast artificial chromosome-1; MC38-CD80, MC38 cells transduced with CD80 gene; MC38-IFN, MC38 cells transduced with IFN-2 gene; WT, wild type; MC38-WT, wild-type MC38; MC38-Neo, MC38 cells transduced with neomycin resistance gene; AICD, activation-induced cell death.
Received for publication July 21, 1999. Accepted for publication October 13, 1999.
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References |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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/. Cell. Immunol. 126:80.[Medline]
1 gene expression into a metastatic murine adenocarcinoma (TS/A) results in CD8+ T cell-mediated tumor rejection and development of antitumor immunity: comparative studies with IFN--producing TS/A cells. J. Immunol. 153:4604.[Abstract]
gene therapy in
combination with CD80-transduction reduces tumorigenicity and growth of
established tumor in poorly immunogenic tumor models. Gene Ther.
In press.
gene therapy for cancer: retroviral transduction of fibroblasts and particle-mediated transfection of tumor cells are both effective strategies for gene delivery in murine tumor models. Gene Ther. 4:1053.[Medline]
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J. Steitz, J. Bruck, J. Lenz, J. Knop, and T. Tuting Depletion of CD25+ CD4+ T Cells and Treatment with Tyrosinase-related Protein 2-transduced Dendritic Cells Enhance the Interferon {alpha}-induced, CD8+ T-Cell-dependent Immune Defense of B16 Melanoma Cancer Res., December 1, 2001; 61(24): 8643 - 8646. [Abstract] [Full Text] [PDF]
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S.-i. Fujii, K. Shimizu, T. Shimizu, and M. T. Lotze Interleukin-10 promotes the maintenance of antitumor CD8+ T-cell effector function in situ Blood, October 1, 2001; 98(7): 2143 - 2151. [Abstract] [Full Text] [PDF]
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V. Soumelis, I. Scott, F. Gheyas, D. Bouhour, G. Cozon, L. Cotte, L. Huang, J. A. Levy, and Y.-J. Liu Depletion of circulating natural type 1 interferon-producing cells in HIV-infected AIDS patients Blood, August 15, 2001; 98(4): 906 - 912. [Abstract] [Full Text] [PDF]
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)
at indicated E:T ratios. Results are reported as mean percentage
cytotoxicity ± SD.
