We examined whether human sodium/iodide symporter (hNIS) radioiodine gene therapy can modulate the phenotype of cancer cells and enhance the killing activities of CTLs in a mouse tumor model. Various doses of I-131 (75, 300, 600, 1,200, and 2,400 μCi/5 mL) were incubated with hNIS-expressing colon cancer (CT26/hNIS) and parental cells (CT26), and numbers of MHC class I and Fas-expressing cells were determined by fluorescence-activated cell sorting (FACS). In addition, CT26/hNIS or CT26 tumor-bearing mice were treated with 1,200 μCi of I-131, and percentages of MHC class I and Fas-expressing tumor cells were determined by FACS. The levels of tumor-infiltrating CD8+IFNγ+ and CD11c+CD86+ cells and CTL killing activities were measured in CT26/hNIS tumor-bearing mice (treated with PBS or 1,200 μCi of I-131) by FACS and lactate dehydrogenase assay, respectively. MHC class I and Fas gene expressions were markedly upregulated in CT26/hNIS cells, but not in CT26 cells, in an I-131 dose-dependent manner. The level of MHC class I and Fas-expressing cancer cell were 4.5-fold and 2.1-fold higher in CT26/hNIS tumors than in CT26 tumors, respectively (P < 0.01). Interestingly, numbers of tumor-infiltrating CD8+IFNγ+ cells and CD11c+CD86+ cells were 5-fold and 2.5-fold higher in I-131–treated tumors than in PBS tumors, respectively (P < 0.001). Furthermore, CTL assays showed significantly more specific tumor cell lysis in I-131 tumors than in PBS tumors (P < 0.01). Our findings suggest that hNIS radioiodine gene therapy can generate tumor-associated immunity in tumor microenvironments and enhance the killing activities of CTLs. Mol Cancer Ther; 9(1); 126–33

The modulation of tumor microenvironments has been shown to be essential for successful cancer immunotherapy. However, because of the complexities of these microenvironments, effective therapeutic effects may not be achieved. Several researchers have reported obstacles to successful therapy, such as tumor-derived suppression cytokines, the absence of danger signal, loss of MHC class molecules, and low antigen levels (15). To overcome these impediments, many research groups have investigated the effects of single and combinatorial therapies.

Among various cancer therapy, radiation-based therapies inhibit cancer growth by inducing the apoptosis and necrosis of cancer cells (6). Furthermore, recently, it was shown that radiation can modify cancer cell phenotypes and enhance the cytotoxic effects of T cells (CTLs) against cancer cells (79). In particular, irradiated cancer or stroma cells show upregulated levels of Fas, MHC class I molecules, and intracellular adhesion molecules-1. Moreover, these sequential modifications in the tumor microenvironment offer the possibility of devising combinatorial therapeutic strategies.

Sodium/iodide symporter (NIS) protein is a specialized active iodide transporter (10, 11), and the transfer of the NIS gene and the subsequent functional expression of NIS protein cause cancer cells to accumulate therapeutic radionuclides, such as I-131 and 188Re, from plasma, and thus, NIS gene transfer offers a possible radionuclide gene therapy. In fact, human NIS (hNIS)–mediated radionuclide gene therapy has been reported by several researchers to offer a potential means of cancer control (1216). However, the phenotypic modulation of cancer cells and the subsequent modification of antitumor immunity by hNIS radioiodine gene therapy have not been studied.

Accordingly, we investigated whether MHC class I and Fas receptor gene expressions are upregulated by hNIS radioiodine gene therapy in vitro and in an in vivo tumor model and whether changes in cancer cell phenotype affect numbers of tumor-infiltrating CD11c+CD86+ cells (activated dendritic cells) and CD8+IFNγ+T cells (CTLs) and enhance the antitumor activities of CTLs.

Animals

Specific pathogen-free 6-wk-old female BALB/c mice were obtained from SLC, Inc. All animal experiments were done after receiving approval from the Institutional Animal Care and Use Committee of the Clinical Research Institute at Seoul National University Hospital. In addition, National Research Council guidelines for the care and use of laboratory animals (revised 1996) were observed throughout.

The Cell Line

The CT26/hNIS cell line established by our laboratory was used throughout (17). This cell line is a stable clone of CT26 cells (an adenocarcinoma colon cancer cell line) that expresses hNIS gene. hNIS gene expression was confirmed by performing 125I uptake assays (data not shown).

Phenotype Marker Analysis

To determine the levels of MHC class I and Fas receptor gene expressions in cancer cells, CT26 and CT26/hNIS cells were grown in 75-cm2 flasks and incubated for 7 h at 37°C in HBSS only or in HBSS containing 75, 300, 600, 1,200, or 2,400 μCi/5 mL of NaI-131. The reaction was terminated by removing radioisotope-containing medium and by washing cells twice with HBSS. Cells were then grown for 3 d. These cells were then stained with PE-conjugated monoclonal rat anti-mouse MHC class I (BD Pharmingen) or PE-conjugated monoclonal hamster antimouse Fas.

To determine levels of MHC class I and Fas receptor gene expression in our mouse tumor model, 1 × 105 CT26 or CT26/hNIS cells were transplanted s.c. into the right thighs of 28 mice (7 mice per group). PBS or 1.2 mCi of I-131 in PBS (200 μL) was i.p. injected into tumor-bearing mice 14 d later. Twenty-one days later, mice were sacrificed and tumor masses were extracted. Tumors were dissociated using collagenase D (Roche), and single cells were stained with PE-conjugated monoclonal rat antimouse MHC class I (BD Pharmingen) or PE-conjugated monoclonal hamster antimouse Fas. Flow cytometric analysis was done using a Becton Dickinson FACScan unit using CELLQuest software (Becton Dickinson Immunocytometry Systems).

Apoptosis Analysis

CT26 and CT26/hNIS cells were grown in 75-cm2 flask and incubated for 7 h at 37°C in HBSS only or in HBSS containing 1.2 mCi/5 mL NaI-131. The radioisotope-containing medium was then removed, and cells were washed twice with HBSS. Cells were then trypsinized, plated in six-well plates (2 × 105), and cultured for a further 3 d. They were then harvested, washed twice with PBS, and stained for 15 min at room temperature with a solution of FITC-conjugated Annexin V and propidium iodide (BD Pharmingen). Flow cytometric analysis was done using a Becton Dickinson FACScan and CELLQuest software (Becton Dickinson Immunocytometry Systems).

In vitro Clonogenic Assay

The procedure used has been described previously (14). Briefly, cells were grown in a 75-cm2 flask and incubated for 7 h at 37°C in 5 mL of HBSS only or HBSS containing 1.2 mCi/5 mL NaI-131. Cells were then washed twice with HBSS, trypsinized, counted, plated in six-well plates containing DMEM at densities of 250 or 1,000 cells per well, grown for 10 d, fixed with 3:1 methanol/acetic acid, and stained with crystal violet. Macroscopic colony numbers were then counted. Survival rates are presented as colony numbers expressed as percentages of colony numbers in plates treated with HBSS only.

Quantification of CD8+ T Cells and Dendritic Cells in Tumors

Tumors from treated mice were dissociated using collagenase. To determine numbers of tumor-infiltrating CTLs, prepared tumor cells were stained with FITC-conjugated monoclonal rat antimouse CD8 (BD Pharmingen) and then immunostained for cytokines using a Cytofix/cytoperm kit (BD Pharmingen) with PE-conjugated anti-IFN-γ (BD Pharmingen). To determine numbers of tumor-infiltrating dendritic cells, prepared tumor cells were stained with FITC-conjugated monoclonal rat antimouse CD11c (BD Pharmingen) and PE-conjugated monoclonal rat antimouse CD86 (BD Pharmingen). Flow cytometric analysis was done using a Becton Dickinson FACScan and CELLQuest software (Becton Dickinson Immunocytometry Systems).

Cytotoxicity Assays

The CytoTox 96 nonradioactive cytotoxicity assay (Promega) was used to measure the cytotoxic activities of splenocytes in treated mice (seven mice per group) according to the manufacturer's protocol with minor modification. Briefly, splenocytes of treated immunocompetent BALB/c mice were incubated in the presence of human interleukin-2 (50 units/mL) and irradiated CT26/hNIS cells (5 × 106). After 3 d, irradiated CT26/hNIS target cells were plated at 1 × 104 cells per well on 96-well U-bottomed plates (Costar), and then splenocytes (effectors) were added to a final volume of 100 μL in ratios of 1:6, 1:12, and 1:25 (target/effector). Plates were then incubated for 4 h in a humidified 5% CO2 chamber at 37°C and centrifuged at 500 × g for 5 min. Aliquots (50 μL) were transferred from all wells to fresh 96-well flat-bottomed plates, and an equal volume of reconstituted substrate mix was added per well. Plates were then incubated in the dark at room temperature for 30 min. Stop solution (50 μL) was then added, and absorbances were measured at 492 nm. Cell death percentages at each effector to target cell ratio were calculated using [A492 nm (experimental) − A492 nm (effector spontaneous) − A492 nm (target spontaneous)] × 100/[A492 nm (target maximum) − A492 nm (target spontaneous)].

In vivo Animal Experiments

The two experimental groups are referred as the PBS and I-131 groups. hNIS radioiodine gene therapy was done as follows (Fig. 4A).

In 14 mice (7 mice per group), 1 × 105 CT26/hNIS cells were transplanted s.c. into right thighs. Subsequently, mice were placed on a low-iodine diet with T4 supplementation in drinking water for 14 wk postchallenge. At 14 d postchallenge, PBS or 1.2 mCi of I-131 was injected i.p. Tumor sizes were measured using a caliper at 14 and 21 d postchallenge.

For scintigraphic imaging acquisition, 99mTc-pertechnetate (0.5 mCi) was injected i.p, and mice were imaged using a γ-ray camera (ON-410; Ohio Nuclear) at 14 and 21 d postchallenge.

Statistical Analysis

All data are expressed as means ± SDs and are representative of at least two separate experiments. Statistical significance was determined using the unpaired Student's t test, and P values of < 0.05 were considered statistically significant.

Phenotypic Modulation of Cancer Cells by hNIS Radioiodine Gene Therapy In vitro

When CT26 and CT26/hNIS cells were treated with HBSS containing 75, 300, 600, 1,200, and 2,400 μCi of I-131, levels of MHC class I and Fas receptor gene expression were significantly increased in CT26/hNIS cells, but not in CT26 cells, in an I-131 dose-dependent manner (Fig. 1A–D; P < 0.01). The upregulation of MHC class I gene expression reached a maximum when CT26/hNIS cells were treated with 1.2 mCi of I-131 (Fig. 1A and B; CT26 and CT26/hNIS, 9.8% and 52.1% of cells showed positive expressions, respectively; P < 0.01). On the other hand, the percentage of Fas receptor–expressing cancer cells increased continuously in a dose-dependent manner (Fig. 1C and D).

Figure 1.

Effect of hNIS radioiodine gene therapy on surface molecule expressions in CT26 and CT26/hNIS cells in vitro. A and C, representative flow cytometry data for MHC class I and Fas receptor. B and D, the Y axis indicates relative increases of MHC class I and Fas receptor expression on cancer cells. Ten thousand cells were analyzed and relative percentage depicts the increased percentage of surface marker gene expression of I-131–treated cells compared with HBSS-treated cells. The data shown are the means of experiments done in triplicate. Points, means; bars, SDs. *, P < 0.01.

Figure 1.

Effect of hNIS radioiodine gene therapy on surface molecule expressions in CT26 and CT26/hNIS cells in vitro. A and C, representative flow cytometry data for MHC class I and Fas receptor. B and D, the Y axis indicates relative increases of MHC class I and Fas receptor expression on cancer cells. Ten thousand cells were analyzed and relative percentage depicts the increased percentage of surface marker gene expression of I-131–treated cells compared with HBSS-treated cells. The data shown are the means of experiments done in triplicate. Points, means; bars, SDs. *, P < 0.01.

Close modal

Phenotypic Modulation of Tumor Cells by hNIS Radioiodine Gene Therapy in the Murine Xenograft Model

After I-131 was given to the two tumor models (CT26 and CT26/hNIS), the level of MHC class I gene expression were significantly more upregulated (by 4.5-fold) in CT26/hNIS tumors than in CT26 tumors (Fig. 2A and B; CT26 and CT26/hNIS, 8.9% and 40.9%; P < 0.01). Furthermore, the percentage of Fas-expressing cells was 2.1-fold higher in CT26/hNIS tumors than in CT26 tumors (Fig. 2C and D; 7% and 14.9%; P < 0.01).

Figure 2.

Changes in surface marker levels on tumor cells in the CT26 and CT26/hNIS tumor models after hNIS radioiodine gene therapy in vivo. A and C, representative flow cytometry data for MHC class I and Fas receptor. B and D, Y axis indicates the relative percentage of MHC class I and Fas receptor–expressing cancer cells. Ten thousand cells were analyzed, and relative percentage depicts the relative increased percentage of surface marker gene expression of I-131–treated cells compared with PBS-treated cells. The data shown are means of experiments done in triplicate. Columns, means; bars, SDs. *, P < 0.01.

Figure 2.

Changes in surface marker levels on tumor cells in the CT26 and CT26/hNIS tumor models after hNIS radioiodine gene therapy in vivo. A and C, representative flow cytometry data for MHC class I and Fas receptor. B and D, Y axis indicates the relative percentage of MHC class I and Fas receptor–expressing cancer cells. Ten thousand cells were analyzed, and relative percentage depicts the relative increased percentage of surface marker gene expression of I-131–treated cells compared with PBS-treated cells. The data shown are means of experiments done in triplicate. Columns, means; bars, SDs. *, P < 0.01.

Close modal

Growth Inhibition of Cancer Cells by hNIS Radioiodine Gene Therapy In vitro

As shown in Fig. 3A and B, I-131 treatment induced more early (AV+PI−), intermediate (AV+PI+), and late apoptosis (AV−PI−) in CT26/hNIS cells than in parental cells (CT26; P < 0.01). Furthermore, in vitro clonogenic assays showed that the survival rates of CT26/hNIS cells were reduced 11.3 ± 1.0% in response to I-131 versus that observed for CT26 cells (Fig. 3C; P < 0.001).

Figure 3.

Cancer cell growth inhibition in vitro. A, representative flow cytometry data. B,Y axis represents cell death (%); the early apoptotic portion was defined as AV+PI−, the intermediate apoptotic portion as AV+PI+, and late apoptotic portion as AV−PI−. C,in vitro clonogenic assay. Survival rates (%) are colony numbers in plates treated with radionuclide expressed as percentages of colony numbers in plates containing buffer only. The data shown are the means of experiments done in triplicate. Columns, means; bars, SDs. *, P < 0.001.

Figure 3.

Cancer cell growth inhibition in vitro. A, representative flow cytometry data. B,Y axis represents cell death (%); the early apoptotic portion was defined as AV+PI−, the intermediate apoptotic portion as AV+PI+, and late apoptotic portion as AV−PI−. C,in vitro clonogenic assay. Survival rates (%) are colony numbers in plates treated with radionuclide expressed as percentages of colony numbers in plates containing buffer only. The data shown are the means of experiments done in triplicate. Columns, means; bars, SDs. *, P < 0.001.

Close modal

In vivo Monitoring of Antitumor Effects and the Effect of hNIS Radioiodine Gene Therapy on Tumor-Infiltrating CD8+IFNγ+T Cells and CD11c+CD86+ Dendritic Cells

Tumor growth inhibition was observed in I-131 group but not in PBS group (Fig. 4B–D; P < 0.05). Interestingly, the number of CD8+IFNγ+ T cells (a CTL marker) in CT26/hNIS-treated mice was 5-fold higher in I-131–treated mice than in PBS-treated mice (Fig. 5A and B; P < 0.001). Furthermore, the number of CD11c+CD86+ dendritic cells (that is activated dendritic cells) in tumors was 2.5-fold higher in I-131–treated mice than PBS-treated mice (Fig. 5C and D; P < 0.001).

Figure 4.

In vivo monitoring of tumor growth inhibition by hNIS radioiodine gene therapy. A,in vivo tumor treatment schedule. B,in vivo monitoring of tumor growth inhibition by scintigraphy. C, regions of interest on scintigraphic images. Regions of interest of muscle and tumor were drawn on scintigraphic images. Tumor-to-muscle ratio was calculated for individual mice. D, tumor volume measurements. The data shown are the means of experiments done in triplicate. Columns, means; bars, SDs. n = 7 mice per group. *, P < 0.05.

Figure 4.

In vivo monitoring of tumor growth inhibition by hNIS radioiodine gene therapy. A,in vivo tumor treatment schedule. B,in vivo monitoring of tumor growth inhibition by scintigraphy. C, regions of interest on scintigraphic images. Regions of interest of muscle and tumor were drawn on scintigraphic images. Tumor-to-muscle ratio was calculated for individual mice. D, tumor volume measurements. The data shown are the means of experiments done in triplicate. Columns, means; bars, SDs. n = 7 mice per group. *, P < 0.05.

Close modal
Figure 5.

Numbers of tumor-infiltrating T cells and dendritic cells in tumors. A and C, representative flow cytometry data for CD8+IFNγ+ T cells and CD11c+CD86+ cells. B and D, columns indicate numbers of CD8+IFNγ+ T cells and CD11c+CD86+ cells per 1 × 105 cells. The data shown are the means of triplicate experiments. Columns, means; bars, SDs. *, P < 0.001. n = 7 mice per group.

Figure 5.

Numbers of tumor-infiltrating T cells and dendritic cells in tumors. A and C, representative flow cytometry data for CD8+IFNγ+ T cells and CD11c+CD86+ cells. B and D, columns indicate numbers of CD8+IFNγ+ T cells and CD11c+CD86+ cells per 1 × 105 cells. The data shown are the means of triplicate experiments. Columns, means; bars, SDs. *, P < 0.001. n = 7 mice per group.

Close modal

Enhancement of CTL Killing Activity against hNIS-Expressing Cancer Ccells by hNIS Radioiodine Gene Therapy

As illustrated in Fig. 6, CTLs against hNIS-expressing CT26 cells in the I-131–treated mice had specific lysis percentages of 45%, 21%, and 11% at effector/target ratios of 25:1, 12:1, and 6:1, respectively. However, the specific lysis percentages of CTLs against hNIS-expressing CT26 in PBS-treated mice were only 5%, 2.3%, and 1.2% at effector/target ratios of 25:1, 12:1, and 6:1, respectively.

Figure 6.

Enhanced cytotoxic effect of CTLs on hNIS-expressing cancer cells by hNIS radioiodine gene therapy. Irradiated CT26/hNIS cells (target cells) were then incubated with splenocytes (effectors) at E/T ratios of 25:1, 12:1, or 6:1 for 4 h in 96-well plates. Experiments were done in triplicate. Points, means; bars, SDs. *, P < 0.01. n = 7 mice per group.

Figure 6.

Enhanced cytotoxic effect of CTLs on hNIS-expressing cancer cells by hNIS radioiodine gene therapy. Irradiated CT26/hNIS cells (target cells) were then incubated with splenocytes (effectors) at E/T ratios of 25:1, 12:1, or 6:1 for 4 h in 96-well plates. Experiments were done in triplicate. Points, means; bars, SDs. *, P < 0.01. n = 7 mice per group.

Close modal

The expression of MHC I class molecule is an essential factor for the presentation of tumor antigen to CTLs (1820). Because most of the level of MHC I class gene expression is downregulated in most cancer, they can escape attack of immune cells (21). Like MHC class I molecules, Fas is also required for CTL-mediated cancer cell death (22). CTLs induce the apoptosis of cancer cells through interaction of Fas ligand secreted from CTLs and Fas receptor on surface of tumor cells. Subsequently, tumor cells highly expressing FasR could become more susceptible to CTLs.

Several groups have reported that external beam radiation concomitantly upregulates MHC class I and Fas gene expression in human and mouse cancer models in vitro and in vivo (8, 2325). For example, Chakraborty et al. found that irradiated cancer cells dose-dependently express highly Fas receptor and intercellular adhesion molecule-1 and that phenotypic modifications of irradiated cancer cells increased the susceptibility of cancer cells to CTLs (8). Another group reported a similar finding in a human cancer cell line, showing that exposure to 10 Gy of radiation upregulated Fas, intercellular adhesion molecule-1, mucin 1 (MUC1), carcinoembryonic antigen, and MHC class I (23). Based on previous reports, we considered that hNIS radionuclide gene therapy, whereby the radioactive isotope I-131 is used as an internal radiation source, might induce the same positive effects as external beam radiation by inducing phenotype modifications in the surface markers of cancer cells and thus enhance antitumor immunity.

In the present study, we found that hNIS I-131 radionuclide gene therapy resulted in the dose-dependent upregulations of MHC class I and Fas receptor proteins in hNIS-expressing cancer cells, but not in parental cells (Fig. 1). Similarly, we observed more increased Fas receptor and MHC class I gene expression in the hNIS-expressing tumor model than in the parental tumor model in vivo (Fig. 2).

Because changes in the surface markers of irradiated cancer cells have been shown to be associated with antitumor immune response augmentation, we examined three key factors, namely, (a) tumor growth inhibitory effects in an hNIS-expressing mouse tumor model, (b) number of tumor-infiltrating dendritic cells and CD8+ T cells, and (c) the cytotoxic effect of CTLs on hNIS-expressing cancer cells. It was found that tumor growth was inhibited in I-131–treated mice, but not in PBS-treated mice (Fig. 2B–D). In addition, numbers of CD11c+CD86+ cells (Fig. 5C and D, a marker of dendritic cells) and CD8+IFNγ+T cells (Fig. 5A and B, a marker of CTLs) were greater in I-131–treated mice, but not in PBS-treated mice (Fig. 5). Furthermore, the cytotoxic effect of CTLs from splenocytes was much higher in I-131–treated group, but not PBS-treated group (Fig. 6).

Previously, we described the effects of hMUC1 vaccination plus hNIS radionuclide gene therapy in a hMUC1 and hNIS-expressing murine colon cancer model (16). In this previous study, combination therapy was found to have a marked tumoricidal effect compared with the two monotherapies (hMUC1 DNA vaccination or hNIS radionuclide gene therapy). We proposed that the reason for this effect of the combination therapy was as follows. Initially, hMUC1-associated immune response occurs in hMUC1-vaccinated mice, and activated immune cells (professional antigen presenting cells) then recognize abundant antigenic peptides generated by irradiated tumors. Also, the phenotypic modification of cancer cells by hNIS radionuclide gene therapy may enhance the killing activity of CTLs. Because hNIS radionuclide gene therapy could be used in combination with other therapy, we believe that our findings regarding the effectiveness of two modality therapies might become important in terms of further applications in clinical situations.

However, the application of our findings in clinical practice is not straightforward, because although it is possible to administer high doses of I-131 (1.2 mCi) to tumor-bearing mice, the same dose cannot be given to humans. Accordingly, to better approximate the likely clinical situation, the effects of minimal I-131 doses should be examined in a mouse tumor model in terms of MHC class I and Fas receptor upregulation in tumor cells and the cytotoxic effects of CTLs. Moreover, our findings suggest that future studies on combinatorial therapies, involving hNIS radionuclide gene therapy, should also determine cancer cell surface marker expressions and tumor-associated antitumor immunity.

This is the first study to show that hNIS radionuclide gene therapy (a) upregulates MHC class I and Fas gene expressions in cancer cells in vitro and in vivo, (b) increases numbers of tumor-infiltrating dendritic cells and CD8+T cells, and (c) increases the cytotoxic effects of CTLs on tumor cells. These findings have important implications for the combined application of hNIS radionuclide gene therapy and immunotherapy in cancer patients at risk of recurrence who are nonresponsive to conventional treatments.

No potential conflicts of interest were disclosed.

Grant Support: This work was supported in part by the Cancer Research Center, the Korean Science and Engineering Foundation (KOSEF) through the Tumor Immunity Medical Research Center at Seoul National University College of Medicine, and a grant of the Korea Healthcare technology R&D Project, Ministry for Health, Welfare and Family Affairs Korea. Y.H. Jeon and Y. Choi were supported by the BK21 Project for Medicine, Dentistry, and Pharmacy (2009).

The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

1
Gurunathan
S
,
Klinman
DM
,
Seder
RA
. 
DNA vaccines: immunology, application, and optimization*
.
Annu Rev Immunol
2000
;
18
:
927
74
.
2
Rosenberg
SA
,
Yang
JC
,
Sherry
RM
, et al
. 
Inability to immunize patients with metastatic melanoma using plasmid DNA encoding the gp100 melanoma-melanocyte antigen
.
Hum Gene Ther
2003
;
14
:
709
14
.
3
Ferrone
S
,
Marincola
FM
. 
Loss of HLA class I antigens by melanoma cells: molecular mechanisms, functional significance and clinical relevance
.
Immunol Today
1995
;
16
:
487
94
.
4
Smyth
MJ
,
Godfrey
DI
,
Trapani
JA
. 
A fresh look at tumor immunosurveillance and immunotherapy
.
Nat Immunol
2001
;
2
:
293
9
.
5
Dudley
ME
,
Rosenberg
SA
. 
Adoptive-cell-transfer therapy for the treatment of patients with cancer
.
Nat Rev
2003
;
3
:
666
75
.
6
Watters
D
. 
Molecular mechanisms of ionizing radiation-induced apoptosis
.
Immunol Cell Biol
1999
;
77
:
263
71
.
7
Klein
B
,
Loven
D
,
Lurie
H
, et al
. 
The effect of irradiation on expression of HLA class I antigens in human brain tumors in culture
.
J Neurosurg
1994
;
80
:
1074
7
.
8
Chakraborty
M
,
Abrams
SI
,
Camphausen
K
, et al
. 
Irradiation of tumor cells up-regulates Fas and enhances CTL lytic activity and CTL adoptive immunotherapy
.
J Immunol
2003
;
170
:
6338
47
.
9
Chakraborty
M
,
Wansley
EK
,
Carrasquillo
JA
, et al
. 
The use of chelated radionuclide (samarium-153-ethylenediaminetetramethylenephosphonate) to modulate phenotype of tumor cells and enhance T cell-mediated killing
.
Clin Cancer Res
2008
;
14
:
4241
9
.
10
Chung
JK
. 
Sodium/iodide symporter: its role in nuclear medicine
.
J Nucl Med
2002
;
43
:
1188
200
.
11
De La Vieja
A
,
Dohan
O
,
Levy
O
,
Carrasco
N
. 
Molecular analysis of the sodium/iodide symporter: impact on thyroid and extrathyroid pathophysiology
.
Physiol Rev
2000
;
80
:
1083
105
.
12
Cho
JY
. 
A transporter gene (sodium/iodide symporter) for dual purposes in gene therapy: imaging and therapy
.
Curr Gene Ther
2002
;
2
:
393
402
.
13
Chen
L
,
Altmann
A
,
Mier
W
, et al
. 
Radioiodine therapy of hepatoma using targeted transfer of the human sodium/iodide symporter gene
.
J Nucl Med
2006
;
47
:
854
62
.
14
Mandell
RB
,
Mandell
LZ
,
Link
CJ
 Jr.
Radioisotope concentrator gene therapy using the sodium/iodide symporter gene
.
Cancer Res
1999
;
59
:
661
8
.
15
Jeon
YH
,
Choi
Y
,
Kim
HJ
, et al
. 
Human sodium/iodide symporter gene adjunctive radiotherapy to enhance the preventive effect of hMUC1 DNA vaccine
.
Int J Cancer
2007
;
121
:
1593
9
.
16
Jeon
YH
,
Choi
Y
,
Yoon
SO
,
Kim
CW
,
Chung
JK
. 
Synergistic tumoricidal effect of combined hMUC1 vaccination and hNIS radioiodine gene therapy
.
Mol Cancer Ther
2008
;
7
:
2252
60
.
17
Kim
HJ
,
Jeon
YH
,
Kang
JH
, et al
. 
In vivo long-term imaging and radioiodine therapy by sodium-iodide symporter gene expression using a lentiviral system containing ubiquitin C promoter
.
Cancer Biol Ther
2007
;
6
.
18
Gilboa
E
. 
How tumors escape immune destruction and what we can do about it
.
Cancer Immunol Immunother
1999
;
48
:
382
5
.
19
Garcia-Lora
A
,
Algarra
I
,
Garrido
F
. 
MHC class I antigens, immune surveillance, and tumor immune escape
.
J Cell Physiol
2003
;
195
:
346
55
.
20
Garcia-Lora
A
,
Algarra
I
,
Collado
A
,
Garrido
F
. 
Tumour immunology, vaccination and escape strategies
.
Eur J Immunogenet
2003
;
30
:
177
83
.
21
Bubenik
J
. 
Tumour MHC class I downregulation and immunotherapy (review)
.
Oncol Rep
2003
;
10
:
2005
8
.
22
Kojima
H
,
Shinohara
N
,
Hanaoka
S
, et al
. 
Two distinct pathways of specific killing revealed by perforin mutant cytotoxic T lymphocytes
.
Immunity
1994
;
1
:
357
64
.
23
Garnett
CT
,
Palena
C
,
Chakraborty
M
,
Tsang
KY
,
Schlom
J
,
Hodge
JW
. 
Sublethal irradiation of human tumor cells modulates phenotype resulting in enhanced killing by cytotoxic T lymphocytes
.
Cancer Res
2004
;
64
:
7985
94
.
24
Demaria
S
,
Bhardwaj
N
,
McBride
WH
,
Formenti
SC
. 
Combining radiotherapy and immunotherapy: a revived partnership
.
Int J Radiat Oncol Biol Phys
2005
;
63
:
655
66
.
25
Gulley
JL
,
Arlen
PM
,
Bastian
A
, et al
. 
Combining a recombinant cancer vaccine with standard definitive radiotherapy in patients with localized prostate cancer
.
Clin Cancer Res
2005
;
11
:
3353
62
.