Rupture of thymoma due to recurrent tumor hemorrhage: a case report.

Background: Rupture of a thymoma is rare, and due to its rarity, the mechanism of rupture remains unclear. Here we report a case of a ruptured thymoma that ruptured due to an increase in the intratumoral pressure caused by recurrent hemorrhaging. Case Description: A 70-year-old woman presented 2 days prior persistent right chest and shoulder pain. A chest computed tomography (CT) scan revealed the presence of a mass occupying the anterior mediastinum and a right pleural effusion. It was diagnosed as an anterior mediastinum tumor. The increase in the levels of inflammatory markers and tumor necrosis observed on CT were suggestive of infection. As the general status of the patient was stable and she initially received antibiotic medical therapy, an improvement in the inflammatory marker levels was observed with antibiotic therapy. A surgical resection was performed 10 days after admission. Median sternotomy revealed a tumor extending from the mediastinum to the right thoracic cavity. Since the adhesion was strong and tumor invasion was suspected, the tumor was completely resected by combining a partial resection of the right middle and lower lobes with the pericardium. Pathological examination revealed that the tumor was a type B2 thymoma with fibrosis, necrosis, hemosiderosis, and hemorrhaging, suggesting recurrent hemorrhaging within the tumor. Conclusions: Based on the findings of our case, recurrent hemorrhaging within the tumor led to an increase in the intratumoral pressure and chronic inflammation and necrosis weakened the tumor wall. These changes contributed to the subsequent rupture.

An autopsy case of disseminated Cunninghamella bertholletiae infection in an immunocompetent patient: a case report.

BACKGROUND: Recently, deaths due to mucormycosis in immunocompromised hosts have increased; however, the clinical and pathological features of mucormycosis are not fully understood, especially in view of the associated high mortality and rare incidence in immunocompetent patients. CASE PRESENTATION: We have described a rare autopsy case of a 67-year-old Japanese man with chronic obstructive pulmonary disease who contracted mucormycosis. He had not been on any immunosuppressants, and his immune functions were intact. Since 3 days prior to admission to our hospital, he had experienced progressive dyspnea, productive cough, and fever. Chest computed tomography revealed pleural effusion in the left lower hemithorax and consolidation in the right lung field. Although he was administered with tazobactam-piperacillin hydrate (13.5 g/day), renal dysfunction occurred on the ninth disease day. Therefore, it was switched to cefepime (2 g/day). However, his general condition and lung-field abnormality worsened gradually. Cytological analysis of the sputum sample at admission mainly revealed sporangiophores and unicellular sporangioles, while repeated sputum culture yielded Cunninghamella species. Therefore, he was diagnosed with pulmonary mucormycosis. Liposomal amphotericin B (5 mg/kg/day) was initiated on the 28th disease day. However, chest radiography and electrocardiography detected cardiomegaly and atrial fibrillation, respectively, and he died on the 37th disease day. A postmortem examination revealed clusters of fungal hyphae within the arteries of the right pulmonary cavity wall, the subpericardial artery, intramyocardial capillary blood vessels, and the esophageal subserosa vein. Direct sequencing revealed that all fungal culture samples were positive for Cunninghamella bertholletiae. CONCLUSIONS: Cunninghamella bertholletiae could rapidly progress from colonizing the bronchi to infecting the surrounding organs via vascular invasion even in immunocompetent patients.

Argon plasma coagulation with atezolizumab and chemoradiation in lung pleomorphic cancer showed a remarkable response: Case report.

RATIONALE: Lung pleomorphic carcinoma (LPC) is generally resistant to chemotherapy or radiotherapy. However, a combination of immune checkpoint inhibitors and radiotherapy has a remarkable efficacy against LPC. PATIENT CONCERNS AND DIAGNOSES: Here, we report the case of a 50-year old man diagnosed with progressive LPC. The tumor invaded the carina and predominantly obstructed the right main bronchus; therefore, a combination of palliative chemoradiotherapy and atezolizumab was initiated. However the trachea was gradually obstructed. INTERVENTION AND OUTCOME: Argon plasma coagulation (APC) was performed to prevent tumor invasion. After three APC sessions, the tumor showed a necrotic change and was easily excised using biopsy forceps. LESSONS: A combination of chemoradiotherapy, atezolizumab, and APC showed a good efficacy, and the patient had a good response to atezolizumab maintenance therapy. Multidisciplinary treatments, such as a combination of immune checkpoint inhibitors and APC, could have synergistic efficacy in lung cancer.

Anomalous systemic arterial supply to the basal lung segments with high serum carbohydrate antigen 19-9 levels-a case report.

Anomalous systemic arterial supply to the basal lung segments is relatively rare. A 39-year-old Japanese man was found to have high serum carbohydrate antigen 19-9 levels during a routine medical examination. He had no medical history and no symptoms. Although his serum carbohydrate antigen 19-9 level was high at 571 U/mL, his abdominal computed tomography (CT), gastrointestinal endoscopy, and abdominal ultrasonography findings were not abnormal. However, his chest CT scan revealed anomalous systemic arterial supply to the basal lung segment of the left lower lobe. He underwent partial resection of the left lung and stapling of the abnormal artery. After surgery, his serum carbohydrate antigen 19-9 level normalized. We consider that bronchiectasis of the basal left lung was involved in carbohydrate antigen 19-9 production and increase in its serum level. It is important to remain aware that various benign lung diseases can cause high serum carbohydrate antigen 19-9 levels.

Programmed cell death-1 blockade in kidney carcinoma may induce eosinophilic granulomatosis with polyangiitis: a case report.

BACKGROUND: Immune checkpoint inhibitors have potential applications in treating various cancers but are associated with immune-related adverse events, such as inflammation, in a wide range of organs; however, allergic inflammation caused by these agents has not been extensively studied. CASE PRESENTATION: A 65-year-old man was diagnosed with a kidney neuroendocrine carcinoma. Three months after kidney resection surgery, the tumor cells had metastasized to his liver and lymph nodes. Subsequently, the patient started chemotherapy; however, regardless of treatment, the tumor grew, and the patient experienced a series of adverse effects, such as taste disorder, anorexia, and general fatigue. Finally, he was administered a programmed cell death (PD)-1 inhibitor, nivolumab (biweekly, toal 200 mg/body), which was effective against kidney carcinoma. However, the patient had a bronchial asthma attack at 22 cycles of nivolumab treatment and chest computed tomography (CT) revealed an abnormal bilateral shadow after 37 cycles of nivolumab treatment. Bronchoscopy findings revealed eosinophil infiltration in the lungs along with severe alveolar hemorrhage. Paranasal sinus CT scanning indicated sinusitis and nerve conduction analysis indicated a decrease in his right ulnar nerve conduction velocity. Based on these findings, the patient was diagnosed with eosinophilic granulomatosis with polyangiitis; he was treated with prednisolone, which alleviated his bronchial asthma. To restart nivolumab treatment, the dose of prednisolone was gradually tapered, and the patient was administered a monthly dose of mepolizumab and biweekly dose of nivolumab. To date, there have been no bronchial attacks or CT scan abnormalities upon follow up. CONCLUSIONS: We present a rare case in which a patient with cancer was diagnosed with eosinophilic granulomatosis with polyangiitis following treatment with a PD-1 inhibitor. Blockade of PD-1 and the programmed cell death ligand (PD-L) 1/PD-1 and PD-L2/PD-1 signaling cascade may cause allergic inflammation. Further studies are needed to identify the specific mechanisms underlying allergic inflammation after PD-1 blockade.

An autopsy case report of extensive intramyocardial hemorrhage complicated with acute myocardial infarction.

Hemorrhagic myocardial infarction (HMI) is a complication associated with percutaneous coronary intervention (PCI) for acute myocardial infarction (AMI). We carried out a successful PCI for a 59-year old Japanese man presenting with chest pain due to AMI over 5 h. The onset to balloon time was 363 min. The next morning, he suffered cardiogenic shock, even with an auxiliary circulating device, which eventually resulted in death. An autopsy revealed extensive HMI. The necrotic myocardium showed not only coagulation necrosis but also contraction band necrosis which suggests myocardial injury due to late reperfusion. Although the intramyocardial hemorrhage was confined to the necrotic area, it was beyond the perfusion area of the culprit artery. Here, we describe a case of death with severe HMI. HMI can be a serious complication and worsen prognosis. .

Salvage surgery for primary lung cancer complicated with Trousseau's syndrome after chemotherapy: a case report.

A 65-year-old man was admitted to our hospital due to an abnormal shadow on chest radiographs. Chest computed tomography (CT) revealed a tumor (diameter: 38 mm × 27 mm) and another small nodule in the left upper lobe of the lung, which were accompanied by lymphangitis of the left upper lobe. The patient underwent a transbronchial lung biopsy, following which he was diagnosed with lung adenocarcinoma. Contrast-enhanced CT and ultrasound imaging revealed bilateral pulmonary artery thrombosis and multiple venous thromboses. He was thus diagnosed with stage IIB lung cancer complicated by Trousseau's syndrome. Chemotherapy was initiated using platinum doublets, while infusions of unfractionated heparin and Xa inhibitor were administered for anticoagulant therapy. Following chemotherapy, the main tumor had shrunk, and his lymphangitis, pulmonary artery thrombosis, and multiple venous thromboses had resolved. We then could perform a left upper lobectomy and lymph node dissection safely.

Period from Loss of the Ability to Access Toilets Independently to Death in End-Stage Cancer Patients.

Background: Toileting independence is considered to be important factors for achieving a "good death" for terminally ill patients. Aim: To clarify the period from loss of the ability to access toilets independently to death in end-stage cancer patients. Design: Observational study. Setting/Participants: The medical records of all end-stage cancer patients who had died while using home care services provided by Medical Corporation Kagayaki General Home Care Clinic between September 2011 and August 2017, were retrospectively reviewed. Results: A total of 220 patients were included. The median time from total dependence in toileting to death was 6.0 (95% confidence interval: 5.0-7.0) days. When the duration was 7 days or shorter and 21 days or shorter, the cumulative death rate was 55.9% and 86.4% respectively. Conclusion: A large percentage of terminally ill cancer patients maintained the ability to access toilets independently until very close to the end of their lives, so the duration of total assistance needed was shorter. These findings may be useful to make a care plan to support achieving "good death" for patients.

Cellular stress induces cancer stem-like cells through expression of DNAJB8 by activation of heat shock factor 1.

In a previous study, we found that DNAJB8, a heat shock protein (HSP) 40 family member is expressed in kidney cancer stem-like cells (CSC)/cancer-initiating cells (CIC) and that it has a role in the maintenance of kidney CSC/CIC. Heat shock factor (HSF) 1 is a key transcription factor for responses to stress including heat shock, and it induces HSP family expression through activation by phosphorylation. In the present study, we therefore examined whether heat shock (HS) induces CSC/CIC. We treated the human kidney cancer cell line ACHN with HS, and found that HS increased side population (SP) cells. Western blot analysis and qRT-PCR showed that HS increased the expression of DNAJB8 and SOX2. Gene knockdown experiments using siRNAs showed that the increase in SOX2 expression and SP cell ratio depends on DNAJB8 and that the increase in DNAJB8 and SOX2 depend on HSF1. Furthermore, treatment with a mammalian target of rapamycin (mTOR) inhibitor, temsirolimus, decreased the expression of DNAJB8 and SOX2 and the ratio of SP cells. Taken together, the results indicate that heat shock induces DNAJB8 by activation of HSF1 and induces cancer stem-like cells.

Phosphorylation of HSF1 at serine 326 residue is related to the maintenance of gynecologic cancer stem cells through expression of HSP27.

Cancer stem-like cells (CSCs)/ cancer-initiating cells (CICs) are defined by their higher tumor-initiating ability, self-renewal capacity and differentiation capacity. CSCs/CICs are resistant to several therapies including chemotherapy and radiotherapy. CSCs/CICs thus are thought to be responsible for recurrence and distant metastasis, and elucidation of the molecular mechanisms of CSCs/CICs are essential to design CSC/CIC-targeting therapy. In this study, we analyzed the molecular aspects of gynecological CSCs/CICs. Gynecological CSCs/CICs were isolated as ALDH1high cell by Aldefluor assay. The gene expression profile of CSCs/CICs revealed that several genes related to stress responses are preferentially expressed in gynecological CSCs/CICs. Among the stress response genes, a small heat shock protein HSP27 has a role in the maintenance of gynecological CSCs/CICs. The upstream transcription factor of HSP27, heat shock factior-1 (HSF1) was activated by phosphorylation at serine 326 residue (pSer326) in CSCs/CICs, and phosphorylation at serine 326 residue is essential for induction of HSP27. Immunohistochemical staining using clinical ovarian cancer samples revealed that higher expressions of HSF1 pSer326 was related to poorer prognosis. These findings indicate that activation of HSF1 at Ser326 residue and transcription of HSP27 is related to the maintenance of gynecological CSCs/CICs.

Matrix metalloproteinase-10 regulates stemness of ovarian cancer stem-like cells by activation of canonical Wnt signaling and can be a target of chemotherapy-resistant ovarian cancer.

Epithelial ovarian cancer (EOC) is one of the most lethal cancers in females. Cancer stem-like cells (CSCs)/cancer-initiating cells (CICs) have been reported to be origin of primary and recurrent cancers and to be resistant to several treatments. In this study, we identified matrix metalloproteinase-10 (MMP10) is expressed in CSCs/CICs of EOC. An immunohistochemical study revealed that a high expression level of MMP10 is a marker for poor prognosis and platinum resistance in multivariate analysis. MMP10 gene overexpression experiments and MMP10 gene knockdown experiments using siRNAs revealed that MMP10 has a role in the maintenance of CSCs/CICs in EOC and resistance to platinum reagent. Furthermore, MMP10 activate canonical Wnt signaling by inhibiting noncanonical Wnt signaling ligand Wnt5a. Therefore, MMP10 is a novel marker for CSCs/CICs in EOC and that targeting MMP10 is a novel promising approach for chemotherapy-resistant CSCs/CICs in EOC.

MAPK13 is preferentially expressed in gynecological cancer stem cells and has a role in the tumor-initiation.

Cancer stem-like cells (CSCs)/cancer-initiating cells (CICs) are defined as small subpopulation of cancer cells that are endowed with higher tumor-initiating ability. CSCs/CICs are resistant to standard cancer therapies including chemotherapy and radiotherapy, and they are thus thought to be responsible for cancer recurrence and metastasis. Therefore, elucidation of molecular mechanisms of CSCs/CICs is essential to cure cancer. In this study, we analyzed the gene expression profiles of gynecological CSCs/CICs isolated as aldehyde dehydrogenase high (ALDH(high)) cells, and found that MAPK13, PTTG1IP, CAPN1 and UBQLN2 were preferentially expressed in CSCs/CICs. MAPK13 is expressed in uterine, ovary, stomach, colon, liver and kidney cancer tissues at higher levels compared with adjacent normal tissues. MAPK13 gene knockdown using siRNA reduced the ALDH(high) population and abrogated the tumor-initiating ability. These results indicate that MAPK13 is expressed in gynecological CSCs/CICs and has roles in the maintenance of CSCs/CICs and tumor-initiating ability, and MAPK13 might be a novel molecular target for treatment-resistant CSCs/CICs.

Brother of the regulator of the imprinted site (BORIS) variant subfamily 6 is involved in cervical cancer stemness and can be a target of immunotherapy.

Cervical cancer is a major cause of cancer death in females worldwide. Cervical cancer stem-like cells (CSCs)/cancer-initiating cells (CICs) are resistant to conventional radiotherapy and chemotherapy, and CSCs/CICs are thought to be responsible for recurrence. Eradication of CSCs/CICs is thus essential to cure cervical cancer. In this study, we isolated cervical CSCs/CICs by sphere culture, and we identified a cancer testis (CT) antigen, CTCFL/BORIS, that is expressed in cervical CSCs/CICs. BORIS has 23 mRNA isoform variants classified by 6 subfamilies (sfs), and they encode 17 different BORIS peptides. BORIS sf1 and sf4 are expressed in both CSCs/CICs and non-CSCs/CICs, whereas BORIS sf6 is expressed only in CSCs/CICs. Overexpression of BORIS sf6 in cervical cancer cells increased sphere formation and tumor-initiating ability compared with those in control cells, whereas overexpression of BORIS sf1 and BORIS sf4 resulted in only slight increases. Thus, BORIS sf6 is a cervical CSC/CIC-specific subfamily and has a role in the maintenance of cervical CSCs/CICs. BORIS sf6 contains a specific c-terminal domain (C34), and we identified a human leukocyte antigen (HLA)-A2-restricted antigenic peptide, BORIS C34_24(9) encoded by BORIS sf6. A BORIS C34_24(9)-specific cytotoxic T cell (CTL) clone showed cytotoxicity for BORIS sf6-overexpressing cervical cancer cells. Furthermore, the CTL clone significantly suppressed sphere formation of CaSki cells. Taken together, the results indicate that the CT antigen BORIS sf6 is specifically expressed in cervical CSCs/CICs, that BORIS sf6 has a role in the maintenance of CSCs/CICs, and that BORIS C34_24(9) peptide is a promising candidate for cervical CSC/CIC-targeting immunotherapy.

Prognostic impact of human leukocyte antigen class I expression and association of platinum resistance with immunologic profiles in epithelial ovarian cancer.

Epithelial ovarian cancer (EOC) is one of the most deadly carcinomas in females. Immune systems can recognize EOCs; however, a defect of human leukocyte antigen (HLA) class I expression is known to be a major mechanism for escape from immune systems, resulting in poor prognosis. The purpose of this study is to identify novel correlations between immunologic responses and other clinical factors. We investigated the expression of immunologic components in 122 cases of EOCs for which surgical operations were performed between 2001 and 2011. We immunohistochemically stained EOC specimens using an anti-pan HLA class I monoclonal antibody (EMR8-5) and anti-CD3, -CD4, and -CD8 antibodies, and we analyzed correlations between immunologic parameters and clinical factors. In multivariate analysis that used the Cox proportional hazards model, independent prognostic factors for overall survival in advanced EOCs included low expression level of HLA class I [risk ratio (RR), 1.97; 95% confidence interval (CI), 1.01-3.83; P = 0.046] and loss of intraepithelial cytotoxic T lymphocyte (CTL) infiltration (RR, 2.11; 95% CI, 1.06-4.20; P = 0.033). Interestingly, almost all platinum-resistant cases showed a significantly low rate of intraepithelial CTL infiltration in the χ(2) test (positive vs. negative: 9.0% vs. 97.7%; P < 0.001). Results from a logistic regression model revealed that low CTL infiltration rate was an independent factor of platinum resistance in multivariate analysis (OR, 3.77; 95% CI, 1.08-13.12; P = 0.037). Platinum-resistant EOCs show poor immunologic responses. The immune escape system of EOCs may be one of the mechanisms of platinum resistance.

Fibroblasts induce expression of FGF4 in ovarian cancer stem-like cells/cancer-initiating cells and upregulate their tumor initiation capacity.

Cancer stem-like cells (CSCs)/cancer-initiating cells (CICs) are defined as a small population of cells within cancer that contribute to cancer initiation and progression. Cancer-associated fibroblasts (CAFs) are stromal fibroblasts surrounding tumor cells, and they have important roles in tumor growth and tumor progression. It has been suggested that stromal fibroblasts and CSCs/CICs might mutually cooperate to enhance their growth and tumorigenic capacity. In this study, we investigated the effects of fibroblasts on tumor-initiating capacity and stem-like properties of ovarian CSCs/CICs. CSCs/CICs were isolated from the ovarian carcinoma cell line HTBoA as aldehyde dehydrogenase 1 high (ALDH1(high)) population by the ALDEFLUOR assay. Histological examination of tumor tissues derived from ALDH1(high) cells revealed few fibrous stroma, whereas those derived from fibroblast-mixed ALDH1(high) cells showed abundant fibrous stroma formation. In vivo tumor-initiating capacity and in vitro sphere-forming capacity of ALDH1(high) cells were enhanced in the presence of fibroblasts. Gene expression analysis revealed that fibroblast-mixed ALDH1(high) cells had enhanced expression of fibroblast growth factor 4 (FGF4) as well as stemness-associated genes such as SOX2 and POU5F1. Sphere-forming capacity of ALDH1(high) cells was suppressed by small-interfering RNA (siRNA)-mediated knockdown of FGFR2, the receptor for FGF4 which was expressed preferentially in ALDH1(high) cells. Taken together, the results indicate that interaction of fibroblasts with ovarian CSCs/CICs enhanced tumor-initiating capacity and stem-like properties through autocrine and paracrine FGF4-FGFR2 signaling.

High expression of CD109 antigen regulates the phenotype of cancer stem-like cells/cancer-initiating cells in the novel epithelioid sarcoma cell line ESX and is related to poor prognosis of soft tissue sarcoma.

Epithelioid sarcoma (ES) is a relatively rare, highly malignant soft tissue sarcoma. The mainstay of treatment is resection or amputation. Currently other therapeutic options available for this disease are limited. Therefore, a novel therapeutic option needs to be developed. In the present study, we established a new human ES cell line (ESX) and analyzed the characteristics of its cancer stem-like cells/cancer-initiating cells (CSCs/CICs) based on ALDH1 activity. We demonstrated that a subpopulation of ESX cells with high ALDH1 activity (ALDH(high) cells) correlated with enhanced clonogenic ability, sphere-formation ability, and invasiveness in vitro and showed higher tumorigenicity in vivo. Next, using gene expression profiling, we identified CD109, a GPI-anchored protein upregulated in the ALDH(high) cells. CD109 mRNA was highly expressed in various sarcoma cell lines, but weakly expressed in normal adult tissues. CD109-positive cells in ESX predominantly formed spheres in culture, whereas siCD109 reduced ALDH1 expression and inhibited the cell proliferation in vitro. Subsequently, we evaluated the expression of CD109 protein in 80 clinical specimens of soft tissue sarcoma. We found a strong correlation between CD109 protein expression and the prognosis (P = 0.009). In conclusion, CD109 might be a CSC/CIC marker in epithelioid sarcoma. Moreover, CD109 is a promising prognostic biomarker and a molecular target of cancer therapy for sarcomas including ES.

Ovarian cancer stem cells are enriched in side population and aldehyde dehydrogenase bright overlapping population.

Cancer stem-like cells (CSCs)/cancer-initiaiting cells (CICs) are defined as a small population of cancer cells that have self-renewal capacity, differentiation potential and high tumor-initiating ability. CSCs/CICs of ovarian cancer have been isolated by side population (SP) analysis, ALDEFLUOR assay and using cell surface markers. However, these approaches are not definitive markers for CSCs/CICs, and it is necessary to refine recent methods for identifying more highly purified CSCs/CICs. In this study, we analyzed SP cells and aldehyde dehydrogenese bright (ALDH(Br)) cells from ovarian cancer cells. Both SP cells and ALDH(Br) cells exhibited higher tumor-initiating ability and higher expression level of a stem cell marker, sex determining region Y-box 2 (SOX2), than those of main population (MP) cells and ALDH(Low) cells, respectively. We analyzed an SP and ALDH(Br) overlapping population (SP/ALDH(Br)), and the SP/ALDH(Br) population exhibited higher tumor-initiating ability than that of SP cells or ALDH(Br) cells, enabling initiation of tumor with as few as 10(2) cells. Furthermore, SP/ADLH(Br) population showed higher sphere-forming ability, cisplatin resistance, adipocyte differentiation ability and expression of SOX2 than those of SP/ALDH(Low), MP/ALDH(Br) and MP/ALDH(Low) cells. Gene knockdown of SOX2 suppressed the tumor-initiation of ovarian cancer cells. An SP/ALDH(Br) population was detected in several gynecological cancer cells with ratios of 0.1% for HEC-1 endometrioid adenocarcinoma cells to 1% for MCAS ovary mucinous adenocarcinoma cells. Taken together, use of the SP and ALDH(Br) overlapping population is a promising approach to isolate highly purified CSCs/CICs and SOX2 might be a novel functional marker for ovarian CSCs/CICs.

Constitutive expression and activation of stress response genes in cancer stem-like cells/tumour initiating cells: potent targets for cancer stem cell therapy.

Cancer stem-like cells (CSCs)/tumour-initiating cells (TICs) are defined as the small population of cancer cells that have stem cell-like phenotypes and high capacity for tumour initiation. These cells may have a huge impact in the field of cancer therapy since they are extremely resistant to standard chemoradiotherapy and thus are likely to be responsible for disease recurrence after therapy. Therefore, extensive efforts are being made to elucidate the pathological and molecular properties of CSCs/TICs and, with this information, to establish efficient anti-CSC/TIC targeting therapies. This review considers recent findings on stress response genes that are preferentially expressed in CSCs/TICs and their roles in tumour-promoting properties. Implications for a novel therapeutic strategy targeting CSCs/TICs are also discussed.

Expression of ECRG4 is associated with lower proliferative potential of esophageal cancer cells.

We have shown that ECRG4 suppressed Fas-induced apoptosis in Jurkat cells. ECRG4 mRNA expression was ubiquitously detected in normal adult human tissues, suggesting that ECRG4 plays a major role in human tissues. ECRG4 mRNA expression was down-regulated in tumor cells. Expression of ECRG4 suppressed cell growth. We established an anti-ECRG4 monoclonal antibody. Our immunohistochemical analysis demonstrated that ECRG4-positive cells tended to be distributed in the region that was negative for Ki-67 in esophageal squamous cell carcinoma tissues. There was a significant inverse correlation between ECRG4 expression and Ki-67 labeling index in esophageal squamous cell carcinoma. This study provides the first functional evidence for an association of endogenous expression of ECRG4 with cell proliferation. ECRG4 is a candidate tumor suppressor gene that might be involved in the proliferation of esophageal squamous cell carcinoma.