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Second Department of Surgery, School of Medicine, University of Occupational and Environmental Health, Kitakyushu, Japan
| Abstract |
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| Introduction |
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We previously reported that 1) fresh human lung cancer tissues engrafted in SCID mice produced human IgG; 2) IgG derived from autologous tumor-infiltrating B lymphocytes (TIB) highly bound to the intra- and extracellular Ags of autologous lung cancer cells; and 3) less reactivity was observed against normal lymphocytes by IgG derived from autologous TIB than from peripheral blood B cells (10, 11, 12). These results indicate that TIB recognize lung cancer cell lines, including the autologous lung cancer cell line, and produce tumor-specific antibodies. We identified 37 Ags recognized by the Abs derived from TIB engrafted in SCID mice. One of these identified Ags was mutated p53 with a point mutation resulting in the alteration of codon 158 from Arg to Leu (10). The production of Ab against p53 protein by TIB indicates that specific B lymphocytes recognizing p53 protein accumulate around the tumor microenvironment. The TIB-derived Ab also showed a same level of reactivity against wild-type p53 protein. The aim of the present study was to ascertain whether cellular immunity against mutated p53 may exist in the regional lymph nodes and also in the primary tumor tissue of the same patient together with humoral immunity against the same Ag.
| Materials and Methods |
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Patient
Patient A904, a 51-year-old male, presented in September 1996 with large cell carcinoma of the lung. After the first operation, a metastatic tumor appeared in the right adrenal gland, which was subsequently resected in October 1997. Thereafter, no recurrence was observed for 6 years.
SCID mice
Female SCID mice (BALB/c · C57BL/Ka-Igh-1b/ICR [N17F34] scid/acid, 6 wk old) were obtained from Charles River (Tokyo, Japan) and maintained in specific pathogen-free conditions throughout the study. Surgically resected specimens from the patient with lung cancer (A904) were used to prepare tissue specimens for implantation as described previously (11, 12). Engrafted SCID mice were bled by a retro-orbital venipuncture once a week after the xenotransplantation of the cancer tissue, and serum was collected and pooled for analysis of human Ig. The human Ig titers were measured by the latex agglutination method (11).
Culture medium (CM)
The CM we used consisted of RPMI 1640 (Life Technologies, Grand Island, NY) supplemented with 10% heated-inactivated FCS (Life Technologies), 10 mM HEPES, 100 U/ml penicillin G, and 100 mg/ml streptomycin sulfate.
Cell lines
A904L is a lung large cell carcinoma cell line derived from patient A904. B cells transformed by EBV (EBV-B) were produced from patient A904 by infecting PBMC with the supernatant from the EBV producer line B95.8. K562 is an erythroleukemia cell line that is sensitive to NK cell cytotoxicity.
Immunohistochemical staining for p53 protein
A904L was stained with Abs against p53 protein using the DO-1 Ab (Oncogene Science, Cambridge, MA) (13).
HLA typing
The tumor cell line genotypes of HLA alleles were determined by PCR, performed by Shionogi Biomedical Laboratories (Osaka, Japan). The genotypes of A904 EBV-B were HLA-A*2402, 2603, -B*0702, 3901, and -Cw*0702, 0702. In contrast, the genotypes of A904L were HLA-A*2402, -B*0702, and -Cw*0702 with a loss of the haplotype.
Peptides
From the reported data concerning the HLA binding motif of peptides (14), the following peptides including the point mutation were selected as Ag peptide candidates to induce CTL. The HLA-A*2402 and -B*0702 binding peptides, the same TPPPGTRVL (mutated p53150 is underlined), and the HLA-Cw*0702 binding peptides, TRVLAMAIY (mutated p53155 is underlined) and TRVRAMAIY (wild-type p53155), were synthesized (Table I).
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Peptide-specific CTL were induced by the method reported by Coulie et al. (15), with a slight modification. In brief, the regional lymph node lymphocytes (RLNL) of the patient were first pulsed with the synthetic mutated p53 peptides at a final concentration of 20 µg/ml for 1 h at room temperature, and then were cultured in the presence of 20 U/ml IL-2 (donated by Takeda Chemical Industries, Osaka, Japan), 5 ng/ml IL-4 (Serotec, Oxford, U.K.), and 5 ng/ml IL-7 (Genzyme, Cambridge, MA). The initial number of RLNL to induce CTL against each peptide was 2.4 x 107. These RLNL were independently divided into eight wells (3 x 106 cells/well) of a 24-well culture plate (Iwaki Glass, Tokyo, Japan). On day 7 the cultured cells were restimulated in the manner described above. On day 14 they were stimulated by irradiated autologous EBV-B prepulsed with the synthetic mutated p53 peptides at a final concentration of 20 µg/ml for 1 h at room temperature. The stimulation was conducted at a responder/stimulator cell ratio of 10:1. CTL activity was assessed by a standard 4-h 51Cr release assay 1 wk after the third stimulation.
To obtain T cell clones, a limiting dilution was performed from the bulk CTL line by the following method. The cells were seeded at 0.1, 0.3, 1, 3, 10, 50, or 500 cells/well in 96-well, U-bottom plates (Iwaki Glass) and stimulated under the following culture conditions: CM with irradiated autologous EBV-B prepulsed with the mutated p53 peptide (5 x 103/well) as stimulator cells and EBV-B established from allogenic PBMC (5 x 104/well) as feeder cells in the presence of IL-2 (50 U/ml), IL-4 (5 ng/ml), and IL-7 (5 ng/ml). Next, the irradiated stimulator cells and feeder cells were added to each well for restimulation of the lymphocytes once per week with CM containing IL-2, IL-4, and IL-7.
Phenotypic analysis
The CTLs were doubly labeled with FITC- and PE-conjugated mAbs to CD3, CD4, CD8, and CD56. These cells were tested, using a two-color analysis, on a flow cytometer.
Monoclonal Ab
Hybridomas (HB-145 and HB-95) were purchased from American Type Culture Collection (Manassas, VA). C7709.A2.6 (anti-HLA-A24) and B1.23.2 (anti-HLA-B and -C) were donated by Dr. P. G. Coulie (Cellular Genetics Unit, Universite Catholique de Louvain, Brussels, Belgium). The supernatants of American Type Culture Collection HB-145 (IVA 12; anti-HLA-DR, -DP, and -DQ), HB-95 (W6/32; anti-HLA-A, -B, and -C), C7709.A2.6, and B 1.23.2 were used to analyze the HLA restriction of the CTLs.
Cytokine production
The cultured lymphocytes (3 x 104/ml) were cocultured with autologous tumor cells or autologous EBV-B (3 x 105/ml) pulsed with peptides for 4 h. Next, the amount of IFN-
in the culture supernatant was measured using an IFN-
ELISA test kit (Life Technologies) according to the instruction manual. To confirm the restriction element of HLA for CTL to recognize the p53 Ag, an HLA transfection experiment using COS-7 cells was performed. The cDNA of HLA-A*2402, -B*0702, and -Cw*0702 was obtained from autologous tumor cells by RT-PCR and cloned into the pcDNA3. The cDNA plasmid of 100 ng of HLA-A*2402, -B*0702, or -Cw*0702 was suspended in 50 µl of OptiMEM (Life Technologies) mixed with Lipofectamine reagent (Life Technologies), and samples were cultured at room temperature for 1 h at a final volume of 100 µl for a duplicate assay. A 50-µl aliquot of the mixture was then added to the COS-7 cells (5 x 103 cells/well), which were then incubated for 4 h at a final volume of 50 µl. Thereafter, the COS-7 cells were pulsed with the mutated p53155 peptide at a final concentration of 20 µg/ml. The COS-7 cells were cultured for 1 day in RPMI 1640 medium supplemented with 10% FCS containing IL-2 (final concentration, 25 U/ml), followed by the addition of CTL (3 x 103 cells/well). After 18-h incubation, 100 µl of the culture supernatant was collected and assayed in duplicate for IFN-
production by ELISA.
TCR usage analysis
TCR V
usage of the CTL clone was assessed by RT-PCR and sequencing. RNA extracted from the CTL clone using RNeasy Mini Kit (Qiagen, Valencia, CA) was converted to cDNA using a random primer. The cDNA served as a template for PCR amplification using a panel of V
-specific forward primers and reverse C
primers. The PCR products were sequenced with the BigDye Terminator Cycle Sequence kit (PerkinElmer, PE Applied Biosystems, Foster City, CA). The products of the sequence reaction were analyzed on an ABI 310 sequencer (PerkinElmer).
PCR analysis
To prove that the CTL clone expressing the same TCR was present in the primary tumor tissue, regional lymph node collected at the surgery (1 x 105 cells), and the peripheral blood of patient A904 collected 3 and 5 years after the operation, RNA was extracted from each sample and converted to cDNA. The cDNA served as template for PCR amplification using V
-specific forward primer (OKY56, 5'-GCACAACAGTTCCCTGACTTGC-3') and the TCR-D-J joint region-specific reverse primer (OKY198, 5'-CCAAAATACTGCGTATCTATCACTCC-3'). The second PCR was performed using the diluted first PCR products (1/100) as a template with the same forward and newly designed TCR-D-J joint region-specific reverse primer (OKY199, 5'-TATCACTCCAAGCCCAAG-3').
| Results |
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As we reported previously, one of 37 distinct cDNA clones identified using the modified SEREX method, which exhibited strong reactivity, corresponded to the gene encoding p53 with one base substitution at position 473 (CGC to CTC) that altered codon 158 from Arg to Leu (10). Titration of the p53 Ab of the SCID mouse serum was performed by a dilution method. The serum was thus shown to have a very strong reactivity with p53 protein up to 2 x 10−5 dilution (data not shown). Probably this mutation resulted in an overexpression of the p53 protein, as the p53 protein was accumulated in the nuclei of the tumor cell line A904L by immunohistochemistry using staining for DO-1 antibody. To determine whether the mutated amino acid in p53 is the epitope recognized by TIB-derived antibody, cDNA coding for wild-type p53 was cloned from autologous EBV-B and tested for the reactivity of TIB-derived antibody. The serum also showed a strong reactivity against wild-type p53 protein, thus indicating that the epitope in p53 recognized by the Ab does not involve the mutated amino acid (Fig. 1).
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The cytotoxic activity was detected in two of eight wells stimulated with mutated p53155 peptide binding to HLA-Cw*0702. The cytotoxic activities against autologous EBV-B pulsed with mutated p53155 peptide and against the autologous tumor cell line (A904L) were detected after three peptide stimulations (data not shown). However, cytotoxic activity could not be induced by stimulation with a mutated p53150 peptide which has a binding affinity to HLA-A*2402 or -B*0702.
Establishment of CTL clone specific for mutated p53155 peptide
A limiting dilution of these bulk CTLs was performed to obtain a mutated p53155 peptide-specific CTL clone. Consequently, one CTL clone (CD3+, CD8+) was obtained.
As shown in Fig. 2, the cytotoxic activities of this CTL clone against autologous EBV-B pulsed with mutated p53155 peptide and against the autologous tumor cell line (A904L) were detected in a dose-dependent manner. However, the cytotoxic activity against autologous EBV-B pulsed with wild-type p53155 peptide could not be detected. These results suggested that the autologous tumor cell line (A904L) endogenously presented the mutated p53155 peptide recognized by the CTL clone that was derived from the RLNL of the patient.
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A blocking assay for the production of IFN-
by the CTL was performed using various mAbs. The CTL clone produced IFN-
in response to mutated p53155 peptide-pulsed autologous EBV-B (Fig. 3A) and an autologous tumor cell line (Fig. 3B). The production of IFN-
was partially inhibited by both anti-MHC class I and anti-HLA-B/C antibodies. The same CTL responses were observed against autologous A904L cells. This CTL clone produced a significant level of IFN-
in response to COS-7 cells transfected with HLA-Cw*0702, but not to cells transfected with either HLA-A*2402 or -B*0702, which was pulsed with mutated p53155 peptide, as shown in Fig. 4. Therefore, this CTL clone recognized mutated p53155 peptide with restriction by HLA-Cw*0702.
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The mutated p53155 peptide-specific CTL clone was proved to express the V
9 gene segment, and it possessed V
9-D
1-J
2-C
2 (Fig. 5A). To determine whether lymphocytes expressing the same TCR as the CTL clone were present in the tumor tissue, regional lymph node collected at surgery, and peripheral blood collected 3 and 5 years after the operation, clonotypic PCR was performed using V
-specific forward primer and TCR-D-J joint region-specific reverse primer. The cDNA from each sample served as a template for PCR amplification. As shown in Fig. 5B, the same TCR as the mutated p53155 peptide-specific CTL clone existed in 20 mg of primary tumor tissue, but not in 1 x 105 of lymphocytes from the regional lymph node and not in 1 x 106 of the lymphocytes from the peripheral blood of the patient collected 3 and 5 years after operation. We further analyzed 8 x 106 of PBMC from the patient collected 3 years after operation for TCR usage, and the same TCR could not be detected (data not shown). These results indicated that the mutated p53155 peptide-specific CTL clone accumulated in the tumor tissue.
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| Discussion |
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p53 plays a key role in the G0-G1 cell cycle regulation, and mutations in the p53 genome are found in >50% of human cancer diseases (17, 18). The p53 mutations lead to changes in p53 protein turnover and subsequent p53 protein accumulation in the tumor cells (19). The accumulated p53 is recognized by B cells and also CTLs. To date, five MHC class I-restricted, naturally presented, human wild-type sequence p53 peptides have been identified. They have been shown to be able to induce epitope-specific CTL from PBMC obtained from healthy individuals (20, 21, 22, 23, 24, 25, 26). The p53125134 peptide is HLA-A24 restricted (26), whereas the other four, p536573, p53149157, p53217225, and p53264272, are HLA-A2.1 restricted. In this study we identified a new mutated p53155163 peptide restricted by HLA-Cw*0702, which was recognized by autologous CTL. An analysis of 1961 Caucasian individuals showed HLA-Cw*0702 to be present in 658 of 3922 alleles, thus demonstrating a phenotype frequency of
31% (27). In Japanese, the phenotype frequency of HLA-Cw*0702 is 24%, and it is predominantly found in HLA-Cw alleles (28).
A mutation of the p53 suppressor gene has been observed in
47% of non-small cell lung cancer (29). Mutated p53 at codon 158 has been reported in four of 65 patients (6.2%) with non-small cell lung cancer (30), and the International Agency for Research on Cancer TP 53 Mutation Data indicated that 38 cases (2.0%) showed the same mutation in 1893 lung tumors (31). Although the mutated p53 at codon 158 is found in a small population, HLA-Cw*0702 is predominantly found in the HLA-Cw alleles of cancer patients. Therefore, the mutated p53155 peptide could be a potential target for cancer vaccination.
In this study because no TIL of A904 were available, clonotypic PCR using CDR3-specific primer was performed to identify mutated p53155 peptide-specific CTLs that infiltrated into tumor tissue. Consequently, the same TCR as the mutated p53155 peptide-specific CTL clone could be detected in the tumor tissue containing TIL. However, the presence of CTL could not be identified by the clonotypic PCR in 1 x 105 of RLNL. The mutated p53155 peptide-specific CTL clone could be elicited from two of eight wells (each well comprised 3 x 106 RLNL). The reason why the CTL could not be detected in 1 x 105 RLNL is because the frequency of the CTL clone is estimated to be
1 cell/1 x 107 cells of RLNL.
Anti-p53 Abs were detected in the sera of patients with an accumulation of p53 protein due to p53 gene mutation in the tumor. Most epitopes of p53 Abs have been shown to be located in the immunodominant N- and C-terminal region outside the core DNA binding domain (32). The secondary structure of these regions remains unchanged in the mutant forms of the protein, suggesting that the immune response is more likely to be due to the accumulation and overexpression of the protein, rather than the appearance of novel antigenic determinants induced by such a mutation. Whereas intratumoral p53 protein accumulation appears to be a prerequisite for the production of anti-p53 Abs, the exact mechanisms of the self-immunization process have not yet been clarified, and whether this type of gene mutation may influence the production of anti-p53 Abs remains a matter of debate. In our results, p53 protein overexpressed in the A904L tumor might have thus induced a strong humoral immunity in this patient.
The identification of tumor-specific Ags in SEREX requires high titrated IgG Ab selectively responsive to tumor-specific Ags, and the development of such Abs requires the help of CD4+ T cells. We also speculate that mutated p53-specific CD4+ T cells may exist in the tumor tissue, thereby causing IgM to IgG conversion.
| Acknowledgments |
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| Footnotes |
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2 Address correspondence and reprint requests to Dr. Mitsuhiro Takenoyama, Second Department of Surgery, School of Medicine, University of Occupational and Environmental Health, 1-1 Iseigaoka, Yahatanishi-ku, Kitakyushu 807-8555, Japan. E-mail address: m-take{at}med.uoeh-u.ac.jp ![]()
3 Abbreviations used in this paper: SEREX, serological analysis of Ags by recombinant cDNA expression cloning; CLP, coactosin-like protein; CM, culture medium; CT Ag, cancer-testis Ag; EBV-B, Epstein-Barr virus-transformed B cells; RLNL, regional lymph node lymphocyte; TIB, tumor-infiltrating B lymphocyte; TIL, tumor-infiltrating lymphocyte. ![]()
Received for publication July 21, 2003. Accepted for publication February 18, 2004.
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