Poorly cohesive gastric cancer with increased epithelial­mesenchymal transition is associated with a poor prognosis.

The present study examined the surgical outcome and prognosis of patients with poorly cohesive carcinoma (PCC), and characterized the molecular pathological factors, epithelial-mesenchymal transition (EMT) and interstitial signals of the disease. A total of 281 patients who underwent gastric cancer (GC) surgery between April 2015 and August 2020 were included. Furthermore, tissue samples from another 197 patients with GC who underwent surgery between 1999 and 2003 were assessed using a tissue microarray. Preoperatively treated cases and endoscopic submucosal dissection cases were excluded, and multiple blocks containing the invasion region were collected for tissue microarray. For tissue microarray analysis, the clinicopathological factors of protein wnt3a (wnt3a), leucine-rich repeat-containing G-protein coupled receptor 5, transforming growth factor-ß-induced, phosphorylated serine/threonine-protein kinase mTOR and E-cadherin expression were collected as EMT markers. The results of the surgical case evaluation and tissue microarray indicated that PCC was more common in younger patients and women, as the ratio of women to men was higher in the PCC group compared with that in the non-PCC group. However, none of the results revealed that the prognosis was worse in all patients with PCC compared with the non-PCC group. Furthermore, in the tissue microarray study, PCC samples exhibited significantly decreased expression of the cell adhesion molecule E-cadherin, suggesting enhanced EMT, which activates wnt3a signaling. PCC with increased EMT was significantly associated with a poor prognosis.

Traumatic sigmoid colon rupture due to breast cancer metastasis: a case report.

The metastasis of breast cancer to the gastrointestinal tract is rare. Herein, we presented the case of an 85-year-old woman who had a history of invasive lobular carcinoma and experienced complete colon rupture due to relatively low-energy trauma. The patient underwent bilateral total mastectomy and axillary dissection following preoperative chemotherapy 6 years ago. She had a local recurrence 2 years after the surgery and underwent chemotherapy. Subsequently, the cancer metastasized to the thoracolumbar area and retroperitoneum. In addition, the patient fell from a height of 30 cm while hanging laundry and her abdomen hit a hose reel. Emergency surgery was performed, and the entire circumference of the sigmoid colon was ruptured. The ruptured colon lesion was resected, and the stump was closed. A double-barrel transverse colostomy was created as it was impossible to lift the stump up to the abdominal wall. Histopathological examination revealed the invasive lobular carcinoma metastasis and a linitis plastica-like change of the colon wall, which probably consequently weakened. In addition, minimal trauma can damage the gastrointestinal tract that had invasive lobular carcinoma metastasis.

Significance of Lipopolysaccharides in Gastric Cancer and Their Potential as a Biomarker for Nivolumab Sensitivity.

Lipopolysaccharides are a type of polysaccharide mainly present in the bacterial outer membrane of Gram-negative bacteria. Recent studies have revealed that lipopolysaccharides contribute to the immune response of the host by functioning as a cancer antigen. We retrospectively recruited 198 patients with gastric cancer who underwent surgery. The presence of lipopolysaccharides was determined using immunohistochemical staining, with the intensity score indicating positivity. The relationship between lipopolysaccharides and CD8, PD-L1, TGFBI (a representative downstream gene of TGF-ß signaling), wnt3a, and E-cadherin (epithelial-mesenchymal transition marker) was also investigated. Thereafter, we identified 20 patients with advanced gastric cancer receiving nivolumab and investigated the relationship between lipopolysaccharides and nivolumab sensitivity. After staining for lipopolysaccharides in the nucleus of cancer cells, 150 negative (75.8%) and 48 positive cases (24.2%) were found. The lipopolysaccharide-positive group showed increased cancer stromal TGFBI expression (p < 0.0001) and PD-L1 expression in cancer cells (p = 0.0029). Lipopolysaccharide positivity was significantly correlated with increased wnt3a signaling (p = 0.0028) and decreased E-cadherin expression (p = 0.0055); however, no significant correlation was found between lipopolysaccharide expression and overall survival rate (p = 0.71). In contrast, high TGFBI expression in the presence of LPS was associated with a worse prognosis than that in the absence of LPS (p = 0.049). Among cases receiving nivolumab, the lipopolysaccharide-negative and -positive groups had disease control rates of 66.7% and 11.8%, respectively (p = 0.088). Lipopolysaccharide positivity was associated with wnt3a, TGF-ß signaling, and epithelial-mesenchymal transition and was considered to tend to promote therapeutic resistance to nivolumab.

Infiltration of Gastric Cancer Stroma by Tumor-Infiltrating Lymphocytes Correlates with Mechanistic Target of Rapamycin Signaling.

INTRODUCTION: We investigated whether the infiltration of tumor-infiltrating lymphocytes (TILs) in gastric cancer (GC), as evaluated by hematoxylin and eosin (H&E) staining, could be a prognostic marker. We also explored on the relationship between TILs and mechanistic target of rapamycin (mTOR) and how it regulates immune effector responses in GC. METHODS: A total of 183 patients with available data on TIL were included. TIL infiltration was evaluated using H&E staining. We also conducted immunohistochemistry to determine mTOR expression. RESULTS: Positive TIL infiltration was defined as TILs ≥20%. There were 72 (39.3%) and 111 (60.7%) positive and negative cases, respectively. TILs positivity significantly correlated with both absence of lymph node metastasis (p = 0.037) and negative p-mTOR expression (p = 0.040). TIL infiltration correlated with a significantly better overall (p = 0.046) and disease-free (p = 0.020) survival. CONCLUSION: mTOR possibly suppresses TIL infiltration in GC. H&E staining is an effective tool for evaluating the immune status of GC patients. H&E staining may be used in clinical practice to monitor treatment response in GC.

Kikuchi-Fujimoto Disease in Human Leukocyte Antigen Partially Matched Siblings: A Case Study of Familial Susceptibility.

Kikuchi-Fujimoto disease (KFD) is a rare and self-limiting disorder that predominantly affects young individuals of Asian descent. This case report describes familial KFD in partially human leukocyte antigen (HLA)-matched siblings. An adolescent male presented with cervical lymphadenopathy and elevated lactate dehydrogenase (LDH) levels, diagnosed by biopsy as KFD; approximately one year later, his sister presented with similar symptoms. Both siblings were found to carry the HLA-DPB1*0202 allele, which is commonly associated with KFD. These cases highlight a genetic component in KFD and encourage further genetic research to delineate the pathogenesis of the disease.

PROX1 Was Associated with LGR5 and Wnt Signaling and Contributed to Poor Prognosis in Gastric Cancer.

INTRODUCTION: We investigated whether the expression of prospero homeobox protein-1 (PROX1) in gastric cancer (GC) could be a prognostic marker. We also focused on the relationship between PROX1 and LGR5 and Wnt/ß-catenin activity in GC. METHODS: A total of 196 patients who underwent potentially curative surgery were collected and reviewed retrospectively. Immunohistochemistry was conducted and evaluated the expression PROX1, LGR5, Wnt3a, and ß-catenin expression. And we evaluated the relationship between PROX1 expression and clinicopathological features. RESULTS: The PROX1 low-expression group consisted of 105 patients (53.6%) and the high-expression group consisted of 91 patients (46.4%). For LGR5 expression, 76 patients (38.8%) were classified as low-expression, and 120 patients (61.2%) were classified as high-expression. The PROX1 low-expression group was significantly younger (p = 0.0095), had more intestinal type (p = 0.014), and had smaller tumor size (p = 0.013). The PROX1 high-expression group was significantly correlated with high LGR5 expression (p < 0.0001) and high Wnt3a expression (p = 0.012). In addition, there were significantly more cases of postoperative recurrence in the PROX1 high-expression group (p = 0.013). CONCLUSION: Our findings demonstrate that PROX1 correlated with the cancer stemness markers LGR5 and Wnt3a signaling in GC and had a poor prognosis including postoperative recurrence.

Coexistence of superficial carcinogenesis of resident epithelium besides neuroendocrine neoplasm of the digestive tract.

BACKGROUND & AIMS: Mixed neuroendocrine-non-neuroendocrine neoplasm (MiNEN) is a rare neuroendocrine neoplasm (NEN) comprising dual neuroendocrine and non-neuroendocrine components. Although the coexistence pattern of neuroendocrine and non-neuroendocrine components in definitive MiNEN is thought to overlap, there may be a coexistent pattern of both components, such as superficial carcinoma adjacent to NEN. The present study evaluated the histopathological findings of the coexistence pattern of superficial carcinomas adjacent to NENs in the esophagogastrointestinal tract. METHODS: From 2000 to 2019, 35 serial NEN resections of the esophagus (n = 9), stomach (n = 3), and large intestine (n = 23), respectively, were performed at Gunma University Hospital. Borderline areas between NEN and resident superficial epithelium were observed in the 35 serial NEN cases as well as two additional cases from affiliated hospitals. RESULTS: Among the 35 serial NEN samples, squamous cell carcinomatous/dysplastic components were identified 77.8% (7/9 cases) of esophageal NENs, and adenocarcinomatous areas were seen in 66.7% (2/3 cases) of gastric NENs and 26% (6/23 cases) of colorectal NENs. Thus, all superficial carcinomatous components adjacent to NENs were observed as squamous cell carcinoma/dysplasia in esophagus and adenocarcinoma in stomach and large intestine, which showed histological characteristics as the resident epithelial pattern in each organ. CONCLUSIONS: These findings suggested a potential "paratransformation" or "bystander effect" in resident epithelium by NENs. Thus, "bystander carcinogenesis" could be a pathogenic mechanism of resident epithelium transformation adjacent to NENs in the esophagogastrointestinal tract.

Sudden unexpected death caused by infantile acute lymphoblastic leukaemia.

A 7-week-old girl with a normal birth history suddenly developed respiratory distress while feeding. Cardiopulmonary resuscitation was initiated at home after she had a cardiac arrest and was continued in the emergency room but all efforts at resuscitation proved unsuccessful and she died 2 h after presentation. Investigations performed in the emergency room revealed that she had a significantly high white blood cell count and severe anaemia. The cause of death was identified as KMT2A-rearranged infantile acute lymphoblastic leukaemia based on cytogenetic tests. She had no abnormalities at the 4-week check-up; however, she developed a skin nodule on her abdomen thereafter, and the family did not consult a doctor for fear of contracting COVID-19. Early detection and diagnosis could have changed the prognosis of the patient. The present case highlights the negative impact of the reduction of outpatient consultations during the COVID-19 pandemic.

High L-Type Amino Acid Transporter 1 Levels Are Associated with Chemotherapeutic Resistance in Gastric Cancer Patients.

INTRODUCTION: We investigated whether the expression of L-type amino acid transporter 1 (LAT-1) in clinical gastric cancer (GC) patients could predict patient therapeutic response to postoperative adjuvant chemotherapy. METHODS: Immunohistochemistry was used to investigate LAT-1, CD98, and phosphorylated-mammalian target of rapamycin (p-mTOR) expression in 111 GC patients. To clarify whether LAT-1 influences the therapeutic effects of chemotherapy, the correlation between disease-free survival rates and LAT-1 was determined in 2 groups: 59 patients who did not undergo postoperative adjuvant chemotherapy and 52 patients who did undergo postoperative adjuvant chemotherapy. RESULTS: LAT-1 was significantly correlated with CD98 and p-mTOR expressions. We did not find any statistically significant correlation between LAT-1 and recurrence in the nontreated group. In contrast, a significant association was found between LAT-1 expression and disease-free survival in the chemotherapy group. Moreover, multivariate regression analysis demonstrated that LAT-1 was an independent predictor of disease-free survival in the postoperative adjuvant chemotherapy group (p = 0.012). CONCLUSION: Our findings demonstrate that LAT-1 is a useful predictive marker for a successful postoperative adjuvant chemotherapy treatment.

PD-L1 upregulation is associated with activation of the DNA double-strand break repair pathway in patients with colitic cancer.

Ulcerative colitis (UC) is a DNA damage-associated chronic inflammatory disease; the DNA double-strand break (DSB) repair pathway participates in UC-associated dysplasia/colitic cancer carcinogenesis. The DSB/interferon regulatory factor-1 (IRF-1) pathway can induce PD-L1 expression transcriptionally. However, the association of PD-L1/DSB/IRF-1 with sporadic colorectal cancer (SCRC), and UC-associated dysplasia/colitic cancer, remains elusive. Therefore, we investigated the significance of the PD-L1/DSB repair pathway using samples from 17 SCRC and 12 UC patients with rare UC-associated dysplasia/colitic cancer cases by immunohistochemical analysis. We compared PD-L1 expression between patients with SCRC and UC-associated dysplasia/colitic cancer and determined the association between PD-L1 and the CD8+ T-cell/DSB/IRF-1 axis in UC-associated dysplasia/colitic cancer. PD-L1 expression in UC and UC-associated dysplasia/colitic cancer was higher than in normal mucosa or SCRC, and in CD8-positive T lymphocytes in UC-associated dysplasia/colitic cancer than in SCRC. Moreover, PD-L1 upregulation was associated with γH2AX (DSB marker) and IRF-1 upregulation in UC-associated dysplasia/colitic cancer. IRF-1 upregulation was associated with γH2AX upregulation in UC-associated dysplasia/colitic cancer but not in SCRC. Multicolour immunofluorescence staining validated γH2AX/IRF-1/PD-L1 co-expression in colitic cancer tissue sections. Thus, immune cell-induced inflammation might activate the DSB/IRF-1 axis, potentially serving as the primary regulatory mechanism of PD-L1 expression in UC-associated carcinogenesis.

[Malignant Central Nervous System Lymphoma after Radical Total Cystectomy : A Diagnostic Challenge].

We report a case of primary central nervous system lymphoma (PCNSL) in an 81-year-old man who had undergone radical cystectomy with an ileal conduit urostomy due to a diagnosis of muscle-invasive bladder cancer. The postoperative diagnosis was invasive urothelial carcinoma (pT2bN1M0, stage IV). Gemcitabine-cisplatin therapy was provided as adjuvant chemotherapy, and there was no recurrence during follow-up. Four years after surgery, he visited the emergency department because of weakness of the lower extremities and stuttering. He was found to have a parietal lobe mass on magnetic resonance imaging (MRI) and hospitalized with suspicion of brain metastasis. Despite examination by a neurosurgeon, it was not possible to make a clinical diagnosis, and the patient gradually deteriorated and died 21 days later. The pathology results were diagnostic of PCNSL.

Malignant peripheral nerve sheath tumour of the oesophagus: a case report.

BACKGROUND: Malignant peripheral nerve sheath tumour (MPNST) is a very rare disease, and its pathogenesis is unknown. There are few reports of MPNST of the oesophagus. We report a case of an MPNST that was diagnosed and resected. CASE PRESENTATION: A 30-year-old female presented with dysphagia. She had been aware of the dysphagia approximately 6 months before presentation. The chest X-ray showed shadows in the right mediastinum. Barium fluoroscopy revealed a semicircular raised lesion in the lower oesophagus. Upper gastrointestinal endoscopy revealed a type 1 oesophageal tumour centred on the posterior wall 26-35 cm from the incisors. The surface was ulcerated, and the tumour was exposed. The affected area showed no iodine uptake. The EUS showed an isoechoic mass. The CT scan showed a mass of 71 × 61 × 55 mm in the beginning of the lower oesophagus with low density mass and swelling of the right recurrent nerve lymph node to 12 mm. On FDG-PET, the tumour showed an SUVmax of 11.05, and no abnormal accumulation was found in lymph nodes or other organs. The MRI showed a hyperintense mass on the T2WI, which had prolonged contrast enhancement, and no findings of invasion into surrounding tissue were found. The patient underwent right thoracotomy and open thoracic oesophagectomy. The affected lymph node was tumour negative by rapid pathological diagnosis during the operation. Histologically, spindle cells with different-sized nuclei were mixed throughout the tissue. Some regions showed nuclear polymorphism or a storiform pattern, and locally, there were approximately 7 mitoses/10 HPFs. The margin was relatively clear, but spindle-shaped tumour cells infiltrated the surrounding interstitium and basal myoepithelium, and the patient was diagnosed with MPNST. In this case, the postoperative course was good, and 16 months after the operation, the patient is currently under observation at the outpatient stage without recurrence. CONCLUSIONS: MPNST in the oesophagus is a relatively rare disease. Diagnosis before treatment is sometimes difficult, but the prognosis is good if radical resection is possible.

Low IRBIT Levels Are Associated With Chemo-resistance in Gastric Cancer Patients.

BACKGROUND/AIM: We investigated whether the expression of inositol 1, 4, 5-trisphosphate receptor-binding protein released with inositol 1, 4, 5-trisphosphate (IRBIT) in clinical gastric cancer (GC) patients could predict the therapeutic response to postoperative adjuvant chemotherapy. MATERIALS AND METHODS: Immunohistochemistry was used to investigate IRBIT expression in 115 GC patients. To clarify whether IRBIT had a relationship with the therapeutic effects of chemotherapy, we compared two groups - 62 patients treated with postoperative adjuvant chemotherapy and 53 patients treated with postoperative adjuvant chemotherapy. RESULTS: Regarding the postoperative adjuvant chemotherapy-free group, we did not find any statistically significant correlation between clinicopathological features and recurrence regardless of the expression of IRBIT. In contrast, in the group receiving postoperative adjuvant chemotherapy, a significant association was found between IRBIT expression and both overall and disease-free survival. CONCLUSION: IRBIT may be used as a useful predictive marker for chemotherapy.

[A Case of Ascending Colon Cancer Recurrence with Para-Aortic Lymph Node Metastases That Was Successfully Treated with Resection and Adjuvant Chemotherapy].

A laparoscopy-assisted right hemicolectomy and D3 lymph node dissection were performed to treat a 60-year-old woman with ascending colon cancer. Microscopically, the resected specimen was diagnosed as adenocarcinoma(tub1>tub2, pSS, pN1, M0). Adjuvant chemotherapy using UFT/UZEL was administered for 6 months. Enlarged para-aortic lymph nodes were identified by follow-up CT 2 years post operation, and a para-aortic lymph node dissection was performed. Microscopic examination revealed that the #216 b1 int lymph node contained poorly differentiated metastatic adenocarcinoma. After 36 courses of FOLFOX as adjuvant chemotherapy, the chemotherapy was discontinued because of an adverse event. She has remained well without recurrence for 5 years after the second surgery. There have been reports of survival improvements by surgical resections in patients with solitary para-aorta lymph node metastases of colorectal cancer. These observations suggest that the surgical therapy may have contributed to the improved prognosis in the present case.

Gliosarcoma with primitive neuronal, chondroid, osteoid and ependymal elements.

A 51-year-old man presented with a 2-week history of malaise. MRI revealed a large solid and cystic lesion with ring enhancement measuring 6.5 cm in diameter in the right frontal lobe. Histologically, the tumor consisted of various components: diffuse growth of atypical astrocytic cells consistent with glioblastoma, fascicular proliferation of atypical spindle cells such as fibrosarcoma, clusters of primitive neuronal cells, and foci of ependymal cells. The sarcomatous component also focally exhibited chondroid and osteoid differentiation. Immunohistochemically, tumor cells in the primitive neuronal component were immunoreactive for synaptophysin and CD56. The spindle cells were immunopositive for Slug and Twist, regulators of epithelial-mesenchymal transition. Direct DNA sequencing demonstrated C228T mutation in the TERT promoter in astrocytic, sarcomatous and primitive neuronal components, suggesting their identical origin. Although a few cases of gliosarcoma with primitive neuronal differentiation have previously been described, the finding that neuronal, glial and sarcomatous components share an identical mutation of the TERT promoter has not been reported. The tumor recurred at the original site 11 months after the first surgery. Interestingly, the recurrent tumor was composed exclusively of a glioblastomatous component, unlike past cases of recurrent gliosarcoma.

High expression of carcinoembryonic antigen and telomerase reverse transcriptase in circulating tumor cells is associated with poor clinical response to the immune checkpoint inhibitor nivolumab.

The present study aimed to enrich circulating tumor cells (CTCs) from blood samples using a new size-sorting CTC chip. The present study also set out to identify a blood sensitivity marker for the immune checkpoint inhibitor nivolumab in patients with advanced, pre-treatment lung cancer. The CTC sorting efficacy of the chip was investigated and the large cell fraction of blood samples from 15 patients with pre-treatment lung cancer who were later administered nivolumab were purified. The expression levels of carcinoembryonic antigen (CEA), human Telomerase Reverse Transcriptase (hTERT), cytokeratin19 (CK19), and programmed death ligand-1 (PD-L1) were investigated to clarify the association between these CTC markers and the clinical response to nivolumab. The CTC chip effectively enriched cells from lung cancer cell line PC-9. The large cell fraction had a high expression of CEA and hTERT, with the former being significantly associated with the clinical response to nivolumab. The expression of CEA and hTERT in CTCs derived from the blood of a patient with lung cancer were also validated. The evaluation of CEA and possibly hTERT in CTCs collected by the CTC chip may represent a promising predictive blood marker for sensitivity to nivolumab. To the best of our knowledge this is the first report to describe the predictive CTC marker for nivolumab in pre-treatment patients.

Heat shock-induced HIKESHI protects cell viability via nuclear translocation of heat shock protein 70.

Heat shock proteins (HSPs), particularly HSP70, help restore normal cellular function following damage caused by stressors. HSP expression in tumor tissues indicates cancer progression, and while the development of HSP inhibitors is progressing, these substances are not widely used to treat cancer. HIKESHI (C11orf73) does not control the intracellular movement of HSP70 at normal temperatures; however, it does regulate the function and movements of HSP70 during heat shock. In this study, we examined the intracellular movement of HSP70 during heat shock to investigate the significance of HIKESHI expression in gastric cancer (GC) and determine if HIKESHI inhibition has cytotoxic effects. We examined HIKESHI using GC cell lines and immunostaining in 207 GC tissue samples. HIKESHI expression in GC tissues was associated with the progression of lymphatic invasion. Suppressing HIKESHI using siRNA did not affect cell viability at normal temperatures. However, suppressing HIKESHI during heat shock inhibited HSP70 nuclear transport and suppressed cell viability. Our results suggest that HIKESHI is a marker of cancer progression and that the combination of HIKESHI inhibition and hyperthermia is a therapeutic tool for refractory GC.

High STMN1 level is associated with chemo-resistance and poor prognosis in gastric cancer patients.

BACKGROUND: Stathmin1 (STMN1) is a cytosolic phosphoprotein that regulates cellular microtubule dynamics and is known to have oncogenic activity. Despite several reports, its roles in gastric cancer (GC) remain unclear owing to a lack of analyses of highly metastatic cases. This study aimed to investigate STMN1 as a prognostic and predictive indicator of response to paclitaxel therapy in patients with GC, including inoperable cases. METHODS: Immunohistochemical analysis of STMN1 was performed on both operable (n=95) and inoperable GC (n=61) samples. The roles of STMN1 in cancer cell proliferation and sensitivity to a microtubule-targeting drug, paclitaxel, were confirmed by knockdown experiments using GC cell lines. RESULTS: Multivariate and Kaplan-Meier analyses demonstrated that high STMN1 was predictive of poor prognosis in both the groups. In the operable cohort, STMN1 expression correlated with cancer curability, recurrence, and resistance to adjuvant therapy. A correlation with paclitaxel resistance was observed in inoperable cases. Knockdown of STMN1 in GC cell lines inhibited proliferation and sensitised the cells to paclitaxel by enhancing apoptosis. CONCLUSIONS: STMN1 is a possible biomarker for paclitaxel sensitivity and poor prognosis in GC and could be a novel therapeutic target in metastatic GC.

Dentatorubral-pallidoluysian atrophy (DRPLA) with a small ganglioglioma component containing neurofibrillary tangles and polyglutamine aggregation.

Dentatorubral-pallidoluysian atrophy (DRPLA), one of the polyglutamine diseases, has not been reported in combination with ganglioglioma (GG). Herein, we report an autopsy case of a 72-year-old man with DRPLA with a small GG component harboring neurofibrillary tangles (NFTs) and polyglutamine aggregates. NFTs, cytoplasmic accumulations of hyper-phosphorylated tau, are mainly observed in Alzheimer's disease (AD) and other tau-associated neurodegenerative disorders. NFTs can also be present in normal aging, and are occasionally observed in low-grade central nervous system (CNS) neoplasms such as GG. In the present case, whole brain examination demonstrated widespread deposition of polyglutamine aggregates, including GG, whereas NFTs were restricted to the GG component. In addition, no other AD or aging-related neuropathological structures were detected throughout the CNS. These findings may provide us with clues to elucidate the pathogenetic mechanisms that neuronal neoplasms may have to develop NFTs regardless of aging, and that polyglutamine may accumulate in neoplastic neurons in polyglutamine disease.

High Expression of MRE11-RAD50-NBS1 Is Associated with Poor Prognosis and Chemoresistance in Gastric Cancer.

BACKGROUND: The MRN complex of meiotic recombination 11 (MRE11), DNA repair protein Rad50 (RAD50) and Nijmegen breakage syndrome 1 (NBS1) proteins coordinate the detection and repair of DNA double-strand breaks (DSBs). DNA DSB repair-dependent chemoresistance likely has an effect on the treatment of human cancer. MATERIALS AND METHODS: We investigated the expression of MRN complex in human gastric cancer (GC) tissues using immunohistochemistry and analyzed its clinical significance and prognostic relevance. RESULTS: The expression of MRN complex was significantly associated with clinical factors including poorer prognosis and negatively associated with the expression of DNA damage marker phosphorylated H2A histone family, member X (γH2AX) in the nucleus. In the biopsy specimens, low expression of MRE11 correlated with good response to chemotherapy and surgical resection after down-staging by chemotherapy. Furthermore, the expression levels of MRE11 and RAD50 were independent predictors of surgical resection after chemotherapy. CONCLUSION: The high expression of MRN complex constituents could be a predictor for poor prognosis and chemoresistance in GC.