Expression of G1 cell cycle markers and the effect of adenovirus-mediated overexpression of p21Waf-1 in squamous cell carcinoma of the esophagus

To determine the crucial abnormality in the cell cycle regulatory proteins in human squamous cell carcinoma of the esophagus, we examined the cell growth ratio (CGR) and basal expression levels of G1 cyclins (cyclin D1, cyclin E), cyclin-dependent kinase (cdk) 2, cdk4, proliferating cell nuclear antigen (PCNA), and p21Waf-1 using 9 cell lines (KE3, KE4, TE8, TE9, TE10, TE11, YES1, YES2, and YES6). Western blotting revealed an inverse linear correlation between the basal levels of p21Waf-1 expression and CGR. The protein levels of G1 cyclins, cdks, and PCNA did not coordinately reflect the CGR. There was no relationship between p21Waf-1 expression levels and mutation of the p53 gene. Next, when the cells were stimulated with serum 48 h after the starvation, stimulated levels of the above G1 cell cycle markers were variously observed among cell lines irrespective of CGR. Serum stimulation markedly induced phosphorylated Rb in TE9 (a high CGR cell line, CGR>2.0), but not in KE4 (a low CGR cell line, CGR<1.5). Furthermore, adenovirus-mediated expression of exogenous p21Waf-1 effectively reduced cell growth in KE3 and TE9 (high CGR cell lines), but not in KE4 and TE11 (low CGR cell lines). p21Waf-1-mediated growth suppression was associated with the induction of involucrin, a marker of squamous cell differentiation. Our data suggested that the basal level, but not the stimulated level, of p21Waf-1 expression play a pivotal role in abnormal growth in human squamous cell carcinoma of the esophagus.

Expression of the SART1 tumor-rejection antigens in colorectal cancers

PURPOSE

Colorectal cancer is one of the major causes of cancer death in the world, including in the United States and Japan. We recently identified the tumor-rejection antigen gene SART1, which encodes both the SART1(259) antigen expressed in the cytosol of epithelial cancers and the SART1(800) antigen expressed in the nucleus of the majority of proliferating cells. This study investigated the expression of these tumor antigens to explore a potential molecule for specific immunotherapy of colorectal cancer patients.

METHODS

SART1 antigens were investigated by Western blotting in six colorectal cancer cell lines and in 33 colorectal cancer tissues. The cancer cell lines were tested for their ability to stimulate interferon-gamma production by the human-leukocyte-antigen-A24-restricted and SART1-specific cytotoxic T lymphocytes and were also tested for their susceptibility to the lysis by the cytotoxic T lymphocytes.

RESULTS

The SART1(259) antigen was detected in the cytosol of four of six cancer cell lines, 13 of 33 (39 percent) cancer tissues, and 0 of 20 nontumorous colorectal tissues. The SART1(800) antigen was expressed in the nucleus of all the colorectal cancer cell lines, 18 of 33 (55 percent) cancer tissues, and 0 of 20 nontumorous tissues. The human-lymphocyte-antigen-A24-restricted and SART1-specific cytotoxic T lymphocytes killed the human-lymphocyte-antigen-A24+ SART1(259+) cancer cells.

CONCLUSIONS

The SART1(259) antigen could be an appropriate target molecule for specific immunotherapy of approximately 40 percent of the human-lymphocyte-antigen-A24+ patients with colorectal cancer.

Locoregional cellular immunotherapy for patients with advanced esophageal cancer

The objectives of the present study were to determine the safety of locoregional administration of autologous lymphocytes stimulated with autologous tumor cells and interleukin (IL) 2 in vitro and to find laboratory markers to predict either clinical toxicity or clinical response. Eleven patients with advanced (n = 4) or recurrent (n = 7) esophageal cancers received the locoregional administration of these activated lymphocytes every 2 weeks for two to nine times (mean, 5.6 times), and mean numbers of the administered cells were 0.8 x 10(9) cells per treatment. The activated lymphocytes that were pretested for their surface markers and CTL activity were endoscopically injected into primary tumor sites (n = 4) or directly injected into metastatic lymph nodes (n = 2), pleural (n = 4) or ascitic (n = 1) regions. Grade 3 hypotension, grade 2 diarrhea, and grade 1 fever were observed in 1, 1, and 6 patients, respectively, and there was no adverse effect in the remaining three patients. The clinical outcome was as follows: one, complete response (CR); three, partial response (PR); two, stable response (SR); and five, progressive disease (PD). CTL activity in the administered cells was observed in 5 of the 11 patients (1 CR, 3 PR, and 1 PD) and was not observed in the remaining 6 patients (2 SR and 4 PD). Percentages of CD16+ cells in the peripheral blood of the responder group (CR+PR) significantly increased when compared with those before treatment or with those of the nonresponder group before as well as after treatment. Because the clinical toxicity was moderate and tolerable, this new method of locoregional immunotherapy will be applicable for use in treatment of patients with advanced and recurrent esophageal cancers. Both CTL activity in the administered cells and the percentages of CD16+ cells in the peripheral blood may be useful laboratory markers for predicting of clinical response.

[New trends in neoadjuvant chemoradiotherapy for locally-advanced esophageal cancer: esophagectomy--is it necessary?]

In responders to neoadjuvant chemoradiotherapy for locally-advanced esophageal cancer, there was no significant difference in the long-term outcome between patients who underwent esophagectomy and those who did not. Esophagectomy might be unnecessary for patients who achieve a complete response with chemoradiotherapy for an esophageal cancer, in cases when salvage surgery is considered in order to treat any future recurrence.

Radical esophagectomy and secondary anastomosis for high-risk patients with intrathoracic esophageal carcinoma

OBJECTIVE

We have often conducted esophageal reconstruction via a thoracic subcutaneous route in high-risk patients to avoid major complications following anastomotic leakage. This type of reconstruction is nonphysiological, however, and presents a poor cosmetic appearance. In better risk patients, therefore, we usually conduct gastric-tube replacement via a posterior mediastinal route. We have recently begun gastric-tube replacement via the posterior mediastinal route with secondary anastomosis for high-risk patients to avoid anastomotic leakage.

RESULTS

From 1996 to 1999, secondary anastomosis was conducted in 25 patients with different degrees of risk--10 with diabetes mellitus, 7 with liver dysfunction, 3 with simultaneous laryngeal and/or pharyngeal cancer, 2 each with induction chemoradiotherapy, cardiac failure, renal dysfunction, respiratory failure, and cardiorespiratory dysfunction, and 1 with cerebral infarction. 6 patients had with multiple combined diseases. Secondary anastomosis was conducted 3-12 weeks (mean: 5.5 weeks) after esophagectomy. Stomach-tube necrosis was not seen in any of the 25 patients undergoing this 2-step procedure. Anastomosis leakage was seen in 5 of the 25 patients (20%), but was slight, in all but 1.

CONCLUSION

Our 2-step procedure has the following advantages: low risk of anastomotic leakage, radical surgery for esophageal cancer, the potential for early adjuvant therapy after esophagectomy, easy and early training in swallowing, and no cosmetic problem. Its disadvantages are prolonged hospitalization, multiple surgery, and esophageal stoma formation. Secondary anastomosis thus appears helpful in treating high-risk patients with advanced esophageal cancer.

[Specific immunotherapy with cancer vaccines]

With the recent progress in molecular biology and gene technology, many new cancer-specific antigens have been identified. Many studies have demonstrated the role of HLA class I-restricted cytotoxic T lymphocytes (CTLs) in cancer specific-immunotherapies. We have also established HLA-A24- and A26-restricted and cancer-specific CTLs from a patient with squamous cell carcinoma of the esophagus. Using CTLs, we identified a new gene SART-1 by cDNA-expression cloning and some SART-1-derived cancer rejection peptides were also identified. Further more, using the same approach, we identified a cyclophilin B gene that encodes antigenic epitopes recognized by HLA-A24-restricted and tumor-specific CTLs. Now we are performing phase I trials using these peptide vaccines and have found an increase in CTL precursor frequency in some cases in an in vitro study. However, other recent studies have reported that many tumors escape from CTL recognition by downregulation of HLA class I expression. Moreover, most cancer cells produce a suppressor agents against the immune system. Therefore, we must resolve these major problems to produce successful cancer vaccine therapy soon.

[Human tumor-rejection antigens and peptides from genes to clinical research]

One of the most significant advances in the field of modern tumor immunology is the identification of genes encoding tumor-rejection antigens that are recognized by human leukocyte antigen (HLA) class I-restricted and tumor-specific cytotoxic T lymphocytes (CTLs). Several peptides encoded by these genes are now under clinical trial as cancer vaccines, and major tumor regression has been observed in some melanoma patients. These results indicate that identification of the peptides capable of inducing CTLs may provide a new modality of cancer therapy. We investigated tumor-rejection antigens from epithelial cancers, and reported 7 genes encoding tumor-rejection antigens and peptides available for specific immunotherapy of HLA-A26 or -A24 patients with epithelial cancers. Furthermore, we identified more than 10 genes encoding tumor-rejection antigens and peptides available for specific immunotherapy of HLA-A2 patients with epithelial cancers. Therefore these new antigens and peptides could be applicable to the treatment of numerous epithelial cancer patients worldwide. Phase I clinical trials of cancer vaccine with these peptides for epithelial cancer patients are in progress at our university. Basic and clinical research will provide new insights for a better understanding of the molecular basis of T cell-mediated recognition of cancer cells and be important for the development of cancer vaccines.

[Immunoguided surgery]

Radioimmunoguided surgery has been attempted using intraoperative tumor detection with radiolabeled monoclonal antibody (mAb). Directly radiolabeled mAb showed poor tumor imaging due to high blood-pool radioactivity. In 1991, three-step immunoscintigraphy of the avidin-biotin system was reported. This three-step method improved tumor imaging because it reduced background radioactivity. Although there were some problems such as a human anti-mouse response and anti-avidin response, the three-step clinical protocol was performed in various cancer patients, and many good results (the tumor detection rate was about 85%) were reported. On the other hand, recent major trials on tumor localization and sentinel lymph node detection have been performed using FDG-PET. However, radioimmunoscintigraphy has the major advantage of simultaneous tumor diagnosis and treatment. In the near future, radioimmunoscintigraphy may become a useful diagnostic method with anticancer effects when its adverse effects are ameliorated by the application of gene technology.

Relationship between cancer cell proliferation and thallium-201 uptake in lung cancer

Although thallium-201 (201Tl) uptake is related to perfusion in many normal tissues, the biologic rationale for 201Tl uptake in tumors is uncertain. To determine if tumor uptake is related to cell proliferation, we correlated the relative retention of 201Tl in lung tumors with expression of Ki-67, an indicator of cell proliferation.

METHODS

Sixty patients with lung tumors, included small cell carcinoma (n = 8) and non-small cell carcinoma (n = 52), underwent 201Tl single photon emission computed tomography (SPECT) imaging. The 201Tl lesion uptake was determined on early and delayed images and the radiotracer retention index (RI) was calculated. Tumor specimens were obtained at surgery or bronchoscopy. The cell proliferation ratio was estimated with MIB-1, a monoclonal antibody that recognized the nuclear antigen Ki-67.

RESULTS

The average 201Tl index was 2.13+/-0.61 (early) and 2.46+/-0.83 (delayed). The average RI was 17.44+/-35.01. Overall, the 201Tl index (delayed) and the cancer cell proliferation were correlated (r = 0.70, p < 0.0001). Of interest, there was a significant correlation (r = 0.872, p < 0.0005) between the 201Tl index on delayed images and the cell proliferation ratio in patients with small cell but not non-small cell lung carcinoma. The 201Tl index (delayed) was significantly higher (p < 0.0001) in patients with small cell lung carcinoma than in patients with non-small cell lung carcinoma.

CONCLUSION

201Tl imaging appears to be useful for evaluating patients with small cell lung carcinoma but not non-small lung carcinoma, and is correlated with the monoclonal antibody MIB-1, a marker of cell proliferation.

Expression levels of thymidine phosphorylase and dihydropyrimidine dehydrogenase in various human tumor tissues

Thymidine phosphorylase (dThdPase) is the rate-limiting enzyme that metabolizes 5'-deoxy-5-fluorouridine (5'-dFUrd, doxifluridine), an intermediate metabolite of capecitabine, to the active drug 5-fluorouracil (5-FUra), while dihydropyrimidine dehydrogenase (DPD) catabolizes 5-FUra to an inactive molecule. The susceptibility of tumors to fluoropyrimidines is reported to correlate with tumor levels of these enzymes. To obtain some insight into the tumor types susceptible to fluoropyrimidine therapy, we measured expression levels of these two enzymes in various types of human cancer tissues (241 tissue samples) by the ELISA methods. DPD exists in all the cancer types studied, such as bladder, breast, cervical, colorectal, esophageal, gastric, hepatic, pancreatic, prostate, and renal cancers. Among them, the cervical, hepatic, pancreatic, esophageal, and breast cancer tissues expressed high levels of DPD (median >70 U/mg protein), while high concentrations of the dThdPase were expressed in esophageal, cervical, breast, and pancreatic cancers and hepatoma (median >150 U/mg protein). The dThdPase/DPD ratio, which was reported to correlate with the susceptibility of human cancer xenografts to capecitabine, was high in esophageal, renal, breast, colorectal, and gastric cancers (median ratio of >1.5). In any of these three parameters, the inter-patient DPD variability for each cancer type was much larger than the DPD variability among cancer types; highest/lowest ratios for dThdPase, DPD, and dThdPase/DPD were 10-321, 7-513, and 2-293, respectively. These results indicate that measurements of the three parameters, DPD, dThdPase and dThdPase/DPD, would be useful criteria for selecting cancer patients suitable for fluoropyrimidine therapy rather than for selecting cancer types.

Histopathological analysis of non-malignant and malignant epithelium in achalasia of the esophagus

We studied the premalignant nature of achalasia using anti-Ki-67 and anti-p53 monoclonal antibodies immunohistochemically. In this study, four patients with esophageal carcinoma and achalasia were investigated. Three tumors were pT4 (UICC pTNM) and one tumor was pT1. The majority of non-malignant esophageal epithelium showed esophagitis and/or dysplasia histologically. Esophageal epithelial cells in the lesions of esophagitis and/or dysplasia had a higher number of Ki-67-positive cells than normal epithelial cells. p53 protein was expressed in two tumors and it was not expressed in non-malignant epithelium. From these results, we found that esophageal epithelium in achalasia lesions is changed to varying degrees of esophagitis and/or dysplasia by stagnation of intake foods, and these abnormal epithelial cells showed a high proliferative state compared with the normal cells without the p53 gene mutation. We suggest that the distinct proliferative status is a cause of carcinogenesis.

CDw108 expression during T-cell development

We recently reported a gene encoding the human CDw108, a glycosylphosphatidylinositol (GPI)-anchored membrane glycoprotein that is preferentially expressed on activated T lymphocytes and erythrocytes. The present study investigated the expression of CDw108 on various tissues and cells, particularly on T cells during development. The murine CDw108 cDNA was cloned initially, and it was highly homologous to the human CDw108 (88.0% or 89.3% similarity at the nucleotide or amino acid level, respectively) or identical to the murine semaphorin K1/Sema7A. The CDw108 mRNA was demonstrated in a few tissues including thymus and brain with the highest expression coming on day 7 in whole embryo followed by relatively consistent expression during development. Cell-surface expression of the CDw108 during T-cell development was further examined by flow cytometry in the human umbilical cord blood and thymus. It was preferentially expressed on a CD34+ stem cell population of umbilical cord blood, and CD3dull CD34+/- CD117 (c-kit)+ CD4bright CDbright cells in the thymus that are involved in the stage of positive selection. These results suggest the contribution of CDw108 in T-cell development, especially in the stage of positive selection in the thymus.

Induction of human leukocyte antigen-A26-restricted and tumor-specific cytotoxic T lymphocytes by a single peptide of the SART1 antigen in patients with cancer with different A26 subtypes

Peptide antigens available for use in specific immunotherapy of patients with cancer have not been fully determined. Although the authors have reported the SART1 gene encoding epitopes recognized by HLA-A2601-restricted and tumor-specific cytotoxic T lymphocytes (CTLs), the HLA-A26 allele is mainly subdivided into A2601, A2602, and A2603 subtypes. In this study, the authors attempted to determine whether the SART1-derived peptide at position 736-744 (KGSGKMKTE) is suitable to induce HLA-A26-restricted and tumor-specific CTLs in patients with cancer who have these subtypes. This peptide induced the HLA-A26 subtype-restricted and tumor-specific CTLs in HLA-A2601+ or HLA-A2603+ peripheral blood mononuclear cells, respectively. It also induced the HLA-A26-restricted CTL activity in HLA-A2602+ peripheral blood mononuclear cells. Therefore, this peptide could be useful for specific immunotherapy of patients with cancer who have any of the three HLA-A26 subtypes.

Identification of a gene coding for a new squamous cell carcinoma antigen recognized by the CTL

Peptide-based specific immunotherapy has resulted in tumor regression in some melanoma patients. However, tumor Ags and peptides for specific immunotherapy, except for treatment of melanomas, have not yet been well identified. In this study, we report a gene encoding a new squamous cell carcinoma (SCC) Ag recognized by cells of the HLA-A24-restricted and tumor-specific CTL line. This gene with 3958-bp length was transcribed from the chromosome 6q22 with six exons, and its mRNA was ubiquitously expressed in both SCCs and normal tissues, and partly expressed in adenocarcinomas. The deduced 958-aa sequence encoded by this gene showed no similarity to any known amino acid sequences. This gene product had a characteristic of an endoplasmic reticulum-resident protein. A 100-kDa protein was detected in the vast majority of SCCs from various tissues, in majority of renal cell carcinomas and brain tumors, and in about one-third of melanomas and adenocarcinomas from various organs other than the breast. In contrast, it was not expressed at all in any of the normal cells or tissues tested, including the testis and fetal liver. Three different peptides at positions 93-101, 161-169, and 899-907 of this Ag were recognized by this CTL line, and all of them induced HLA-A24-restricted and tumor-specific CTLs from PBMCs of SCC patients. Therefore, these peptides may be useful for peptide-based specific immunotherapy of HLA-A24+ patients with SCC in various organs, as well as for treatment of other cancer.

Expression of SART3 tumor-rejection antigen in gastric cancers

We previously reported SART3 as a tumor-rejection antigen recognized by histocompatibility leukocyte antigen (HLA)-A24-restricted cytotoxic T lymphocytes (CTLs). In this study, we investigated the expression of the SART3 antigen in gastric cancers, as a candidate for use in specific immunotherapy. The SART3 antigen was detected in 9 of 10 (90%) gastric cancer cell lines, 35 of 52 (67.3%) gastric cancer tissues, and 0 of 20 non-tumorous gastric tissues. SART3-derived peptides corresponding to positions 109- 118 and 315-323 induced HLA-A24-restricted and tumor-specific CTLs from peripheral blood mononuclear cells (PBMCs) of gastric cancer patients. These peptide-induced CTLs recognized HLA-A24(+) SART3(+) gastric cancer cells, but not HLA-A24(+) SART3(-) or HLA-A24(-) SART3(+) gastric cancer cells. Therefore, the SART3 peptides could be useful in specific immunotherapy of gastric cancer patients.

Mutations in zinc-binding domains of p53 as a prognostic marker of esophageal-cancer patients

Some investigators have suggested that mutations of the p53 gene may be molecular markers for poor prognosis of cancer patients, although others have reported conflicting results. We examined esophageal cancers from 138 patients to investigate whether mutational status of p53 could be correlated either with prognosis or with response to chemotherapy or radiation. We detected p53 mutations in the tumors of 78 (56.5%) patients. Kaplan-Meier analysis showed that these 78 patients tended to have shorter survival times and greater resistance to either form of therapy than patients whose tumors carried two wild-type p53 alleles. The difference became more evident when we focused on mutations in zinc-binding domains of p53 (L2 and L3); the prognosis was significantly poorer among the 29 patients with tumors in this category than among patients whose tumors had no p53 mutations, or p53 mutations outside L2 or L3 (P=0.0060). Moreover, those tumors as a group were more resistant to chemotherapy or radiation than the others (P=0.0105). Our results underscore the importance of the zinc-binding domains of p53 with respect to clinical prognosis for patients with esophageal carcinomas.

Differential role of the JNK and p38 MAPK pathway in c-Myc- and s-Myc-mediated apoptosis

The s-Myc is similar to c-Myc in its ability to induce apoptosis requiring caspase activation. However, s-Myc is distinct from c-Myc in that it has activity to suppress tumor growth and does not require wild-type p53 to induce apoptosis. These facts suggest differential regulation between s-Myc and c-Myc. Here we showed that s-Myc-mediated apoptosis triggered by UV was not inhibited by the inactive form mutant JNK (APF), though c-Myc-mediated apoptosis was. Moreover, we found that JNK did not affect the transactivation activity of s-Myc, but stimulated that of c-Myc. In contrast, both Myc-mediated apoptosis and caspase-3-like protease activation were suppressed by kinase-negative MKK6 and an inactive form mutant p38(AGF). Our results indicate that s-Myc does not require the JNK signaling unlike c-Myc during UV-triggered apoptosis, but the MKK6/p38MAPK pathway might regulate common apoptotic machinery for both s-Myc and c-Myc upstream of caspase.

Evaluation of the accuracy of preoperative staging in thoracic esophageal cancer

BACKGROUND

Exact clinical staging before treatment of esophageal cancer has become increasingly important in the evaluation and comparison of the results of different treatment modalities, including surgery, chemotherapy, and radiotherapy.

METHODS

The accuracy of preoperative tumor staging by using an esophagography, esophagoscopy, percutaneous and endoscopic ultrasonography, and computed tomography was assessed in 224 patients with resectable esophageal cancer. The results of tumor staging by these tests were compared prospectively with the pathologic stage of the esophagectomy specimens with respect to the T and N categories defined by the International Union Against Cancer TNM classification.

RESULTS

For the T category, the overall accuracy was 80%. For the N category, overall accuracy was 72%, with a sensitivity of 78%, a specificity of 60%, and a positive predictive value of 78%. Overall, the accuracy of stage grouping was 56%.

CONCLUSIONS

Either the T or N categories can be predicted reliably by clinical staging techniques. However, the preoperative stage grouping might not be valid in resectable, localized esophageal cancer.

Regulation of c-Myc through phosphorylation at Ser-62 and Ser-71 by c-Jun N-terminal kinase

The expression of c-myc promotes cell proliferation and also sensitizes cells to various extracellular apoptotic stimuli. However, signal pathways regulating the function of Myc proteins during apoptosis are unknown. c-Jun N-terminal kinase (JNK) is activated by various apoptotic stimuli, but neither the target molecule(s) or the action of JNK has been identified in Myc-mediated apoptosis. Here, we found that JNK selectively interacted with, and phosphorylated, c-Myc at Ser-62 and Ser-71 as confirmed with phospho-c-Myc-specific antibodies. Interestingly, dominant negative mutant JNK(APF) impaired the c-Myc-dependent apoptosis, but not mutated c-Myc (S62A/S71A)-dependent apoptosis triggered by UV irradiation. Furthermore, c-Myc (S62A/S71A)-expressing NIH3T3 cells were not sensitized like wild type c-Myc-expressing NIH3T3 cells to JNK-activating apoptotic stimuli, such as UV and Taxol. These results indicate that the JNK pathway is selectively involved in the c-Myc-mediated apoptosis and that the apoptotic function of c-Myc is directly regulated by JNK pathway through phosphorylation at Ser-62 and Ser-71.

Identification of a gene coding for a protein possessing shared tumor epitopes capable of inducing HLA-A24-restricted cytotoxic T lymphocytes in cancer patients

Genes encoding tumor epitopes that are capable of inducing CTLs against adenocarcinomas and squamous cell carcinomas, two major human cancers histologically observed in various organs, have rarely been identified. Here, we report a new gene from cDNA of esophageal cancer cells that encodes a shared tumor antigen recognized by HLA-A2402-restricted and tumor-specific CTLs. The sequence of this gene is almost identical to that of the KIAA0156 gene, which has been registered in GenBank with an unknown function. This gene encodes a Mr 140,000 protein that is expressed in the nucleus of all of the malignant tumor cell lines tested and the majority of cancer tissues with various histologies, including squamous cell carcinomas, adenocarcinomas, melanomas, and leukemia cells. However, this protein was undetectable in the nucleus of any cell lines of nonmalignant cells or normal tissues, except for the testis. Furthermore, this protein was expressed in the cytosol of all of the proliferating cells, including normal cells and malignant cells, but not in normal tissues, except for the testis and fetal liver. Two peptides of this protein were recognized by HLA-A2402-restricted CTLs and were able to induce HLA-A24-restricted and tumor-specific CTLs from peripheral blood mononuclear cells of most of HLA-A24+ cancer patients tested, but not from peripheral blood mononuclear cells of any healthy donors. These peptides may be useful in specific immunotherapy for HLA-A24+ cancer patients with various histological types.

Induction of terminal differentiation and apoptosis in human colonic carcinoma cells by brefeldin A, a drug affecting ganglioside biosynthesis

An appreciable increase in G(M3) with a concomitant decrease in some neolacto-series gangliosides was observed during differentiation of human colonic carcinoma HCT 116 cells induced by a differentiating agent. When the cells were treated with brefeldin A (BFA), a striking increase in de novo biosynthesis of G(M3) and a decrease in biosynthesis of neolactoseries gangliosides were observed after 6 h. Clear morphological changes to differentiated epithelial cells and an arrest of cells in the G0/G1 phase of the cell cycle were observed after 1 day of treatment. Then the cells were led to apoptosis. This activity was not affected by forskolin, which antagonizes the effects of BFA on protein transport and the Golgi apparatus. These results suggest that the differentiation-inducing activity of BFA might be due to its modulatory effect on ganglioside biosynthesis, and that a specific change in ganglioside pattern is an essential prerequisite for induction of differentiation, providing a novel target for differentiation therapy of cancer.

Identification of a SART-1-derived peptide capable of inducing HLA-A24-restricted and tumor-specific cytotoxic T lymphocytes

We have described the SART-1 gene-encoding peptides recognized by HLA-A2601-restricted and tumor-specific cytotoxic T lymphocytes (CTLs). We now have investigated whether SART-1 encodes peptides capable of inducing the HLA-A24-restricted CTLs. Among the 18 different peptides with HLA-A24-binding motifs, the SART-1(690-698) peptide (EYRGFTQDF) was most strongly recognized by the HLA-A24-restricted and tumor-specific CTLs established from an esophageal cancer patient. After a third stimulation in vitro, this peptide induced HLA-A24-restricted CTLs recognizing the SART-1(259)+ tumor cells in PBMCs of all HLA-A24 homozygous and the majority of HLA-A24 heterozygous cancer patients and healthy donors tested. A similar activity, induction of CTLs from PBMCs, was observed in the Saccharomyces cerevisiae-derived nonapeptide (EYRGFTPMF) that shares 7 amino acids with the SART-1(690-698) peptide. The SART-1(690-698) peptide-induced CTL activity was significantly higher in PBMCs of HLA-A24 homozygotes than in HLA-A24 heterozygotes. The CTL precursor frequency in PBMCs after a third stimulation in vitro with the SART-1(690-698) peptide was high (>1/200) in both cancer patients and healthy donors. The SART-1(690-698) peptide could thus be useful for specific immunotherapy of HLA-A24+ cancer patients.