ALDH1-high ovarian cancer stem-like cells can be isolated from serous and clear cell adenocarcinoma cells, and ALDH1 high expression is associated with poor prognosis

Cancer stem-like cells (CSCs)/cancer-initiating cells (CICs) are defined as a small population of cancer cells that have high tumorigenicity. Furthermore, CSCs/CICs are resistant to several cancer therapies, and CSCs/CICs are therefore thought to be responsible for cancer recurrence after treatment and distant metastasis. In epithelial ovarian cancer (EOC) cases, disease recurrence after chemotherapy is frequently observed, suggesting ovarian CSCs/CICs are involved. There are four major histological subtypes in EOC, and serous adenocarcinoma and clear cell adenocarcinoma are high-grade malignancies. We therefore analyzed ovarian CSCs/CICs from ovarian carcinoma cell lines (serous adenocarcinoma and clear cell adenocarcinoma) and primary ovarian cancer cells in this study. We isolated ovarian CSCs/CICs as an aldehyde dehydrogenase 1 high (ALDH1(high)) population from 6 EOC cell lines (3 serous adenocarcinomas and 3 clear cell adenocarcinomas) by the ALDEFLUOR assay. ALDH1(high) cells showed greater sphere-forming ability, higher tumorigenicity and greater invasive capability, indicating that ovarian CSCs/CICs are enriched in ALDH1(high) cells. ALDH1(high) cells could also be isolated from 8 of 11 primary ovarian carcinoma samples. Immunohistochemical staining revealed that higher ALDH1 expression levels in ovary cancer cases are related to poorer prognosis in both serous adenocarcinoma cases and clear cell adenocarcinoma cases. Taken together, the results indicate that ALDH1 is a marker for ovarian CSCs/CICs and that the expression level of ALDH1 might be a novel biomarker for prediction of poor prognosis.

Rapid on-site evaluation by endosonographer during endoscopic ultrasound-guided fine needle aspiration for pancreatic solid masses

BACKGROUND AND AIM

Endoscopic ultrasound-guided fine needle aspiration (EUS-FNA) is an established diagnostic method for patients with suspected pancreatic ductal carcinoma. Rapid on-site evaluation (ROSE) has been reported to improve the accuracy. However, an on-site cytopathologist is not routinely available in many institutions. One of the solutions may be ROSE by endosonographer. The aim was to examine whether diagnostic accuracy increases through ROSE by endosonographer using our cytological criteria.

METHODS

Patients who underwent EUS-FNA of solid pancreatic masses from January 2006 to August 2009 (n = 53, period 1) and September 2009 to April 2011 (n = 85, period 2) were retrospectively identified. Before initiating ROSE at the start of period 2, two endosonographers underwent training for cytological interpretation, which was focused on four cytological features of pancreatic ductal carcinoma: anisonucleosis, nuclear membrane irregularity, overlapping, and enlargement. During EUS-FNA in period 2, endosonographers classified the Diff-Quik smears under three atypical grades and evaluated the adequacy. All diagnoses were made by one pathologist without knowledge of clinical information.

RESULTS

The rate of "inconclusive" diagnoses, interpreted as "suspicious," "atypical," and "inadequate for diagnosis" was reduced from 26.4% in period 1 to 8.2% in period 2 (P = 0.004). Moreover, diagnostic accuracy was increased from 69.2% in period 1 to 91.8% in period 2 (P < 0.001).

CONCLUSIONS

This cytological grading system used in ROSE by endosonographers is invaluable for the diagnosis of pancreatic solid masses.

Validity and reproducibility of Ki-67 assessment in gastrointestinal stromal tumors and leiomyosarcomas

With the aim of standardizing Ki-67 immunohistochemistry, we assessed interobserver and interlaboratory variability of the Ki-67 labeling index and Ki-67 score among eight general pathologists for 24 gastrointestinal stromal tumors (GISTs) and 12 leiomyosarcomas, which were predominantly of the gastrointestinal (GI) tract, mesentery and retroperitoneum, based on a review of a tissue microarrays subjected to immunohistochemistry with antibodies for Ki-67. For Ki-67 immunostaining of mesenchymal tumors of the GI tract, including GISTs, differences were seen in the scores given by regional hospitals. Conversely, for two categories of the Ki-67 labeling index, namely <10% and ≥10%, concordance of the Ki-67 score between microscopic observation and image analysis, and between the observers, was good, but it was not good for the other four categories of the index for <5%, 5-9%, 10-29%, and ≥30%. The concordance of the Ki-67 scores between the observers in two categories was higher using the Ki-67 pre-stained tissue microarrays (TMAs) within each participating institute than that using the Ki-67 stained TMAs between the participating institutes. The reproducibility of a 10% cut-off value for the Ki-67 labeling index to predict the prognosis of GISTs was relatively high, but there is an urgent need to standardize the staining technique.

Prostate cancer stem-like cells/cancer-initiating cells have an autocrine system of hepatocyte growth factor

Prostate cancer cells include a small population of cancer stem-like cells (CSCs)/cancer-initiating cells (CICs) that have roles in initiation and progression of the cancer. Recently, we isolated prostate CSCs/CICs as aldehyde dehydrogenase 1-highh (ALDH1(high) ) cells using the ALDEFLUOR assay; however, the molecular mechanisms of prostate CSCs/CICs are still elusive. Prostate CSCs/CICs were isolated as ALDH1(high) cells using the ALDEFLUOR assay, and the gene expression profiles were analyzed using a cDNA microarray and RT-PCR. We found that prostate CSCs/CICs expressed higher levels of growth factors including hepatocyte growth factor (HGF). Hepatocyte growth factor protein expression was confirmed by enzyme linked immunosorbent assay and Western blotting. On the other hand, c-MET HGF receptor was expressed in both CSCs/CICs and non-CSCs/CICs at similar levels. Hepatocyte growth factor and the supernatant of myofibloblasts derived from the prostate augmented prostasphere formation in vitro, and prostasphere formation was inhibited by an anti-HGF antibody. Furthermore, c-MET gene knockdown by siRNA inhibited the prostasphere-forming ability in vitro and tumor-initiating ability in vivo. Taken together, the results indicate that HGF secreted by prostate CSCs/CICs and prostate myofibroblasts has a role in the maintenance of prostate CSCs/CICs in an autocrine and paracrine fashion.

Use of potassium channel tetramerization domain-containing 12 as a biomarker for diagnosis and prognosis of gastrointestinal stromal tumor

Previously, we showed that the expression of potassium channel tetramerization domain-containing 12 (KCTD12), which was discovered by a proteomics approach, is associated with high-risk behavior of gastrointestinal stromal tumors (GISTs). Here, we examined the distribution and expression of this protein by immunostaining with a commercially available polyclonal KCTD12 antibody in GISTs (n = 64) and other types of malignancy (n = 168) to clarify its diagnostic and clinical significance. Diffuse KCTD12 immunoreactivity was found in most GISTs (52 cases; 81%). KCTD12 expression was observed primarily in vascular endothelial cells, Purkinje cells of the cerebellum, and some neurons scattered throughout the cerebral cortex. KCTD12 was absent from not only the interstitial cells of Cajal but also interstitial cells of Cajal hyperplasia that was encountered incidentally in colon diverticulitis. KCTD12 immunostaining was also seen in malignant peripheral nerve sheath tumors (2/10 cases; 20%), synovial sarcomas (2/10; 20%), solitary fibrous tumor (1/8; 13%), angiosarcoma (1/7; 14%), and colon adenocarcinoma (1/24; 4%). In survival analyses, the 5-year recurrence-free survival rate of patients without KCTD12 expression was only 16.7% compared with 95.6% in those with KCTD12 expression (P < .0001). Ki-67 and KCTD12 were significant predictors of recurrence-free survival, and KCTD12 expression provided additional information about recurrence-free survival after accounting for Ki-67 status. Overall, KCTD12 expression was specific for GISTs from neoplastic and nonneoplastic adult tissues other than brain and served as a predictor of GIST recurrence. These findings suggest that KCTD12 is a useful and reliable biomarker for both the diagnosis and prognosis of GIST.

Expression and function of FERMT genes in colon carcinoma cells

Invasion into the matrix is one of hallmarks of malignant diseases and is the first step for tumor metastasis. Thus, analysis of the molecular mechanisms of invasion is essential to overcome tumor cell invasion. In the present study, we screened for colon carcinoma-specific genes using a cDNA microarray database of colon carcinoma tissues and normal colon tissues, and we found that fermitin family member-1 (FERMT1) is overexpressed in colon carcinoma cells. FRRMT1, FERMT2 and FERMT3 expression was investigated in colon carcinoma cells. Reverse transcription polymerase chain reaction (RT-PCR) analysis revealed that only FERMT1 had cancer cell-specific expression. Protein expression of FERMT1 was confirmed by western blotting and immunohistochemical staining. To address the molecular functions of FERMT genes in colon carcinoma cells, we established FERMT1-, FERMT2- and FERMT3-overexpressing colon carcinoma cells. FERMT1-overexpressing cells exhibited greater invasive ability than did FERMT2- and FERMT3-overexpressing cells. On the other hand, FERMT1-, FERMT2- and FERMT3-overexpressing cells exhibited enhancement of cell growth. Taken together, the results of this study indicate that FERMT1 is expressed specifically in colon carcinoma cells, and has roles in matrix invasion and cell growth. These findings indicate that FERMT1 is a potential molecular target for cancer therapy.

Prognostic impact of the expression of ALDH1 and SOX2 in urothelial cancer of the upper urinary tract

Aldehyde dehydrogenase 1 (ALDH1) and sex determining region-Y-related high mobility group box 2 (SOX2) have been identified as putative cancer stem-like cell/tumor-initiating cell markers in various cancer tissues. The aim of this study was to elucidate the prognostic impact of these putative cancer stem-like cell/tumor-initiating cell markers in upper urinary tract urothelial cell carcinoma. Immunohistochemical staining for ALDH1 and SOX2 was carried out on archival specimens from 125 patients with upper urinary tract urothelial cell carcinoma who underwent radical nephroureterectomy. The prognostic value of ALDH1 and SOX2 expression and other clinicopathological features was evaluated. On univariate analysis, tumor grade, pathological T stage, pathological N stage, lymphovascular invasion, ALDH1 expression and SOX2 expression were associated with a poor prognosis. On multivariate analysis, the independent factors of prognosis were tumor grade (P=0.014), pathological N stage (P=0.005) and ALDH1 expression (P=0.002). In subgroup analysis, those subgroups with no positive, one positive or two positive results in immunohistochemistry for ALDH1 and SOX2 expression had estimated 5-year cancer-specific survival rates of 80%, 49% and 22%, respectively (P<0.001). Neither ALDH1 nor SOX2 expression correlated with intravesical recurrence after radical nephroureterectomy. These findings suggest that cancer stem-like cells/tumor-initiating cells are linked to more aggressive behavior of upper urinary tract urothelial cell carcinoma, supporting the current cancer stem cell hypothesis. Thus, therapeutic targeting of cancer stem-like cells/tumor-initiating cells in upper urinary tract urothelial cell carcinoma is a future possibility.

Nuclear, but not cytoplasmic, localization of survivin as a negative prognostic factor for survival in upper urinary tract urothelial carcinoma

Survivin, a member of the inhibitor of apoptosis protein gene family, inhibits apoptosis and promotes mitosis. We determined whether nuclear or cytoplasmic localization of survivin could predict survival of patients with upper urinary tract urothelial carcinoma (UUTUC). Immunohistochemical staining for survivin was carried out on archival specimens from 125 consecutive patients with UUTUC who underwent radical nephroureterectomy. Nuclear and cytoplasmic staining of survivin was scored and compared with clinicopathologic features and cancer-specific survival (CSS). Nuclear expression of survivin was significantly correlated with tumor grade (p < 0.001), lymphovascular invasion (p = 0.022) and poor survival with an estimated 5-year CSS probability of 54 % for tumors with nuclear expression of survivin vs. 73 % for those without nuclear expression of survivin (hazard ratio = 2.19; 95 % confidence interval = 1.02-4.70; p = 0.043). The 5-year cancer-specific survival rates of patients with cytoplasmic survivin-negative and -positive tumors were 66 and 67 %, respectively. There was no difference in survival between patients with cytoplasmic survivin-negative tumors and those with cytoplasmic survivin-positive tumors. Using univariate analysis, nuclear survivin expression, tumor grade, pathological T stage, pathological N stage, and lymphovascular invasion were the predictive variables for CSS. In contrast, cytoplasmic survivin expression had no prognostic relevance. These data suggest that nuclear accumulation of survivin represents biologic aggressiveness and that nuclear survivin is a negative prognostic marker in patients with resected UUTUC.

DNA methyltransferase 1 is essential for initiation of the colon cancers

DNA methyltransferase 1 (Dnmt1) is essential for the maintenance of hematopoietic and somatic stem cells in mice; however, its roles in human cancer stem-like cells (CSCs)/cancer-initiating cells (CICs) are still elusive. In the present study, we investigated DNMT1 functions in the maintenance of human colon CSCs/CICs using the human colon cancer cell line HCT116 (HCT116 w/t) and its DNMT1 knockout cell line (DNMT1(-/-)). The rates of CSCs/CICs were evaluated by side population (SP) analysis, ALDEFLUOR assay and expression of CD44 and CD24. SP, ALDEFLUOR-positive (ALDEFLUOR(+)) and CD44-positive and CD24-positive (CD44(+)CD24(+)) cell rates were lower in DNMT1(-/-) cells than in HCT116 w/t cells. Since CSCs/CICs have higher tumor-initiating ability than that of non-CSCs/CICs, the tumor-initiating abilities were addressed by injecting immune deficient (NOD/SCID) mice. DNMT1(-/-) cells showed less tumor-initiating ability than did HCT116 w/t cells, whereas the growing rate of DNMT1(-/-) cells showed no significant difference from that of HCT116 cells both in vitro and in vivo. Similar results were obtained for cells in which DNMT1 had been transiently knocked-down using gene-specific siRNAs. Taken together, these results indicate that DNMT1 is essential for maintenance of colon CSCs/CICs and that short-term suppression of DNMT1 might be sufficient to disrupt CSCs/CICs.

HSP DNAJB8 controls tumor-initiating ability in renal cancer stem-like cells

Cancer stem-like cells (CSC) are a small population of cancer cells with superior tumor initiating, self-renewal, and differentiation properties. In this study, we show that the cancer-testis antigen and HSP40 family member DNAJB8 contributes to the CSC phenotype in renal cell carcinoma (RCC). DNAJB8 overexpression increased the percentage of side population (SP) cells representing CSCs in RCC cells, enhancing their tumor-initiating ability. Conversely, attenuation of DNAJB8 decreased SP cells and reduced tumor-initiating ability. The utility of DNAJB8 as an immunologic target was established in DNA vaccination experiments. Compared with immunization with the tumor-associated antigen survivin, which was expressed in both CSCs and non-CSCs in RCC, immunization with Dnajb8 expression plasmids yielded stronger antitumor effects. Together, our findings suggest that DNAJB8 plays a role in CSC maintenance and that it offers a candidate for CSC-targeting immunotherapy in RCC.

Establishment of a monoclonal anti-pan HLA class I antibody suitable for immunostaining of formalin-fixed tissue: unusually high frequency of down-regulation in breast cancer tissues

A novel monoclonal anti-pan human leukocyte antigen (HLA) class I heavy chain antibody, EMR8-5, was established. It could detect HLA-A, -B, and -C antigens in formalin-fixed paraffin embedded tissues. By immunohistochemical staining using the EMR8-5 antibody, various cancer tissues from 246 cases were examined for HLA class I expression. It was found that HLA class I expression was decreased in 20% to 42% of the cases of lung cancer, hepatocellular carcinoma, colon cancer, renal cell carcinoma, and urothelial carcinoma. In contrast, 85% of breast cancer cases had loss of or decreased HLA class I expression. Of the 35 breast cancer cases that had decreased HLA class I heavy chain expression, 33 (94%) also had decreased beta2-microglobulin expression detected by immunohistochemical staining. It was suggested that HLA class I down-regulation might be a common characteristic of breast cancer mostly caused by the down-regulation of beta2-microglobulin expression.

SOX2 is overexpressed in stem-like cells of human lung adenocarcinoma and augments the tumorigenicity

Recently, the SOX2 gene has been reported to be amplified in human lung squamous cell carcinomas. However, its roles in human lung adenocarcinomas are still elusive. In this study, we analyzed the functions of SOX2 in cancer stem-like cells (CSCs)/cancer-initiating cells (CICs) derived from human lung adenocarcinoma. Human lung CSCs/CICs were isolated as higher tumorigenic side population (SP) cells using Hoechst 33342 dye from several lung cancer cell lines. Four of nine lung cancer cell lines were positive for SP cells (LHK2, 1-87, A549, Lc817). The ratios of SP cells ranged from 0.4% for Lc817 to 2.8% for LHK2. To analyze the molecular aspects of SP cells, we performed microarray screening and RT-PCR analysis, and isolated SOX2 as one of a SP cell-specific gene. SOX2 was expressed predominantly in LHK2 and 1-87 SP cells, and was also expressed in several other cancer cell lines. The expression of SOX2 protein in primary human lung cancer tissues were also confirmed by immunohistochemical staining, and SOX2 was detected in more than 80% of primary lung cancer tissues. To address SOX2 molecular functions, we established a SOX2-overexpressed LHK2 and A549 cell line (LHK2-SOX2 and A549-SOX2). LHK2-SOX2 cells showed higher rates of SP cells and higher expression of POU5F1 compared with control cells. LHK2-SOX2 and A549-SOX2 cells showed relatively higher tumorigenicity than control cells. On the other hand, SOX2 mRNA knockdown of LHK2 SP cells by gene-specific siRNA completely abrogated tumorigenicity in vivo. These observations indicate that SOX2 has a role in maintenance of stemness and tumorigenicity of human lung adenocarcinoma CSCs/CICs and is a potential target for treatment.

Cytotoxic T lymphocytes efficiently recognize human colon cancer stem-like cells

Cancer stem-like cells (CSCs) and tumor-initiating cells (TICs) are a small population of cancer cells that share three properties: tumor initiating ability, self-renewal, and differentiation. These properties suggest that CSCs/TICs are essential for tumor maintenance, recurrence, and distant metastasis. Here, we show that cytotoxic T lymphocytes (CTLs) specific for the tumor-associated antigen CEP55 can efficiently recognize colon CSCs/TICs both in vitro and in vivo. Using Hoechst 33342 dye staining, we isolated CSCs/TICs as side population (SP) cells from colon cancer cell lines SW480, HT29, and HCT15. The SP cells expressed high levels of the stem cell markers SOX2, POU5F1, LGR5, and ALDH1A1 and showed resistance to chemotherapeutic agents such as irinotecan or etoposide.To evaluate the susceptibility of SP cells to CTLs, we used CTL clone 41, which is specific for the CEP55-derived antigenic peptide Cep55/c10orf3_193 (10) (VYVKGLLAKI). The SP cells expressed HLA class I and CEP55 at the same level as the main population cells. The SP cells were susceptible to CTL clone 41 at the same level as main population cells. Furthermore, adoptive transfer of CTL clone 41 inhibited tumor growth of SW480 SP cells in vivo. These observations suggest that Cep55/c10orf3_193(10) peptide-based cancer vaccine therapy or adoptive cell transfer of the CTL clone is a possible approach for targeting chemotherapy-resistant colon CSCs/TICs.

Phase I clinical trial of survivin-derived peptide vaccine therapy for patients with advanced or recurrent oral cancer

Survivin, a member of the inhibitor of apoptosis protein (IAP) family, is abundantly expressed in most malignancies, but is hardly detectable in normal adult tissues. Previously we have identified a human leukocyte antigen (HLA)-A24-restricted antigenic peptide, survivin-2B80-88 (AYACNTSTL), recognized by CD8(+) cytotoxic T lymphocytes (CTL). Survivin-2B80-88-specific CTL were induced efficiently from peripheral blood mononuclear cells (PBMC) of oral cancer patients after stimulation with the peptide in vitro. We conducted a phase I clinical study to evaluate the safety and the efficacy of survivin-2B80-88 peptide vaccination in HLA-A24-positive patients with advanced or recurrent oral cancer. The vaccines were given subcutaneously or intratumorally six times at 14-day intervals. Eleven patients were enrolled and 10 patients completed the vaccination protocol. No adverse events were observed in any patients. In two patients, the levels of serum squamous cell carcinoma (SCC) antigen decreased transiently during the period of vaccination. Tumor regression that was compatible with a partial response (PR) was noted in one patient. The remaining nine patients experienced progressive disease (PD). Immunologically, an increase of the peptide-specific CTL frequency was detected in six of the eight patients evaluated by HLA-A24/peptide tetramer analysis. The present clinical trial revealed that survivin-2B peptide vaccination was safe and had therapeutic potential for oral cancer patients. However, subsequent clinical trials in combination with various adjuvant drugs will be required to improve the immunological and therapeutic efficacy. This trial was registered with University Hospital Medical Information Network (UMIN) number UMIN000000976.

The feasibility of Cep55/c10orf3 derived peptide vaccine therapy for colorectal carcinoma

In our previous study, we demonstrated that a peptide derived from the novel centrosome residing protein Cep55/c10orf3 can be targeted by the cytotoxic T lymphocytes (CTLs) in peripheral blood mononuclear cells (PBMCs) of breast carcinoma patients. In this report, we evaluated the feasibility of cancer immunotherapy using Cep55/c10orf3 peptide for colorectal carcinoma (CRC). To evaluate the expression of Cep55/c10orf3 in CRC tissues, we performed immunohistochemical staining of using anti-Cep55/c10orf3 monoclonal antibody. Sixty-three percent cases showed weak positive for Cep55/c10orf3 in total 70 CRC cases. The Cep55/c10orf3 expression intention was collated with high histological grade of CRC. Thus, we hypothesized that Cep55/c10orf3 can also be the target of CTLs in CRC cases. We generated CTLs from PBMCs of human leukocyte antigen (HLA)-A24-positive colorectal carcinoma patients using HLA-A24-restricted Cep55/c10orf3 peptides. Two of 6 colorectal cancer patients were reactive for the Cep55/c10orf3_193(10) peptide, which was the only immunogenic peptide in breast carcinoma patients. CTL clone specific for Cep55/c10orf3_193(10) recognized and lysed HLA-A24 (+) and Cep55/c10orf3 (+) colorectal carcinoma cell lines. In addition, 1 of 6 colorectal carcinoma patients was reactive for the Cep55/c10orf3_402(11) and Cep55/c10orf3_283(12) peptides, but not for Cep55/c10orf3_193(10) with the ELISPOT assay. These observations suggest that the antigenic peptide repertoire presented by HLA-A24 in colorectal carcinoma might be different from that in breast carcinoma. Thus, these peptide vaccination peptide mixture of Cep55/c10orf3_193(10), Cep55/c10orf3_402(11) and Cep55/c10orf3_283(12) might be more effective than a single peptide in the treatment of colorectal carcinoma patients.

Novel spliced form of a lens protein as a novel lung cancer antigen, Lengsin splicing variant 4

A glutamine synthetase I family protein, Lengsin, was previously identified as a novel lens-specific transcript in the vertebrate eye. In this report, we show for the first time that Lengsin is a novel tumor-associated antigen expressed ectopically in lung cancer. Interestingly, a novel spliced form of human Lengsin termed 'splicing variant 4', gaining exon 3 that codes extra 63 amino acids, is the dominant transcript form in lung cancer cells. Lengsin mRNA could be detected in 7 of 12 (58%) lung cancer cell lines and 7 of 7 (100%) surgically resected lung cancer tissues. On the other hand, Lengsin transcripts could not be detected in normal major tissues or in other cancer cell lines, including melanoma, colorectal carcinoma, breast carcinoma and hepatocellular carcinoma. In addition, knockdown of Lengsin mRNA with RNAi caused cell death and a decrease of cell viability, suggesting that Lengsin has some essential role in cell survival. Since the lens is an immune-privileged site, we regard Lengsin as a highly immunogenic cancer antigen. Anti-Lengsin autoantibodies were detectable in sera of lung cancer patients, although these patients did not show any lens-related disturbances. Hence, Lengsin splicing variant 4 might be an immunogenic lung cancer-specific antigen that is suitable as a diagnostic marker and for molecular targeting therapy, including immunotherapy.

Identification of an immunogenic CTL epitope of HIFPH3 for immunotherapy of renal cell carcinoma

PURPOSE

CD8(+) CTLs have an essential role in immune response against tumor. Although tumor-associated antigens have been identified in renal cell carcinoma (RCC), few of these are commonly shared and investigated as therapeutic targets in the clinical medicine. In this report, we show that HIFPH3, a member of prolyl hydroxylases that function as oxygen sensor, is a novel tumor antigen and HIFPH3-specific CTLs are induced from peripheral blood lymphocytes of RCC patients.

EXPERIMENTAL DESIGN

Expression of HIFPH3 was examined by reverse transcription-PCR and immunostaining with anti-HIFPH3 antibody. To identify HLA-A24-restricted T-cell epitopes of HIFPH3, eight peptides were selected from the amino acid sequence of this protein and screened for their binding affinity to HLA-A24. Peptide-specific CTLs were induced by stimulating peripheral blood lymphocytes of HLA-A24-positive RCC patients with these peptides in vitro. HLA-A24-restricted cytotoxicity of the CTLs against HIFPH3(+) RCC lines was assessed by chromium release assay.

RESULTS

HIFPH3 was overexpressed in many RCC cell lines and primary RCC tissues, whereas it was not detectable in normal adult tissues by reverse transcription-PCR. Of the eight peptides that contained HLA-A24-binding motif, HIFPH3-8 peptide (amino acid sequence, RYAMTVWYF) could induce the peptide-specific CTLs from 3 of 6 patients with HIFPH3-positive RCC. Furthermore, HIFPH3-8 peptide-specific CTLs showed cytotoxicity against HIFPH3(+) RCC cell lines in a HLA-A24-restricted manner.

CONCLUSIONS

HIFPH3 may be a target antigen in immunotherapy for RCC and HIFPH3-8 peptide could be used as a peptide vaccine for HLA-A*2402(+)/HIFPH3(+) RCC patients.