• Asian Pacific Journal of Cancer Prevention
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• 제17권4호
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• pp.1917-1923
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• 2016

Background: Lynch Syndrome (LS) is a familial cancer condition caused by germline mutations in DNA mismatch repair genes. Individuals with LS have a greatly increased risk of developing colorectal cancer (CRC) and it is therefore important to identify mutation carriers so they can undergo regular surveillance. Tumor DNA from LS patients characteristically shows microsatellite instability (MSI). Our aim here was to screen young CRC patients for MSI as a first step in the identification of unrecognized cases of LS in the Saudi population. Materials and Methods: Archival tumor tissue was obtained from 284 CRC patients treated at 4 institutes in Dammam and Riyadh between 2006 and 2015 and aged less than 60 years at diagnosis. MSI screening was performed using the BAT-26 microsatellite marker and positive cases confirmed using the pentaplex MSI analysis system. Positive cases were screened for BRAF mutations to exclude sporadic CRC and were evaluated for loss of expression of 4 DNA mismatch repair proteins using immunohistochemistry. Results: MSI was found in 33/284 (11.6%) cases, of which only one showed a BRAF mutation. Saudi MSI cases showed similar instability in the BAT-26 and BAT-25 markers to Australian MSI cases, but significantly lower frequencies of instability in 3 other microsatellite markers. Conclusions: MSI screening of young Saudi CRC patients reveals that approximately 1 in 9 are candidates for LS. Patients with MSI are strongly recommended to undergo genetic counselling and germline mutation testing for LS. Other affected family members can then be identified and offered regular surveillance for early detection of LS-associated cancers.

• Journal of Gastric Cancer
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• 제23권2호
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• pp.264-274
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• 2023

Purpose: In this study, polymerase chain reaction (PCR)-based microsatellite instability (MSI) testing was comprehensively analyzed and compared with immunohistochemistry (IHC) for mismatch repair (MMR) protein expression in patients with gastric cancer (GC). Materials and Methods: In 5,676 GC cases, PCR-based MSI testing using five microsatellites (BAT-26, BAT-25, D5S346, D2S123, and D17S250) and IHC for MLH1 were performed. Reevaluation of MSI testing/MLH1 IHC and additional IHC for MSH2, MSH6, and PMS2 were performed in discordant/indeterminate cases. Results: Of the 5,676 cases, microsatellite stable (MSS)/MSI-low and intact MLH1 were observed in 5,082 cases (89.5%), whereas MSI-high (MSI-H) and loss of MLH1 expression were observed in 502 cases (8.8%). We re-evaluated the remaining 92 cases (1.6%) with a discordant/indeterminate status. Re-evaluation showed 1) 37 concordant cases (0.7%) (18 and 19 cases of MSI-H/MMR-deficient (dMMR) and MSS/MMR-proficient (pMMR), respectively), 2) 6 discordant cases (0.1%) (3 cases each of MSI-H/pMMR and MSS/dMMR), 3) 14 MSI indeterminate cases (0.2%) (1 case of dMMR and 13 cases of pMMR), and 4) 35 IHC indeterminate cases (0.6%) (22 and 13 cases of MSI-H and MSS, respectively). Finally, MSI-H or dMMR was observed in 549 cases (9.7%), of which 47 (0.8%) were additionally confirmed as MSI-H or dMMR by reevaluation. Sensitivity was 99.3% for MSI testing and 95.4% for MMR IHC. Conclusions: Considering the low incidence of MSI-H or dMMR, discordant/indeterminate results were occasionally identified in GCs, in which case complementary testing is required. These findings could help improve the accuracy of MSI/MMR testing in daily practice.

• 대한의생명과학회지
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• 제9권3호
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• pp.171-175
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• 2003

Microsatellite instability (MSI), which is caused by a deficient mismatch repair system, is seen in most of the hereditary non-polyposis colon cancers (HNPCC) and a portion of sporadic colorectal cancers. Forty unselected colorectal cancer patients were analyzed for MSI using silver stain plus kit. The overall incidence of MSI in studied cases was 17％ (7/40). The incidence is similar result with previous study. MSI in colorectal carcers was more prevalent in moderative differentiated adenocarcinoma than well differentiated adenocarcinoma

• Asian Pacific Journal of Cancer Prevention
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• 제17권9호
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• pp.4259-4265
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• 2016

Background: Colorectal malignancies with high microsatellite instability (MSI-H), either hereditary (Lynch syndrome) or sporadic, demonstrate better prognosis and altered response to 5FU chemotherapy. It is now recommended to perform MSI testing for all new cases of colorectal cancer regardless of being categorized as hereditary or sporadic. For MSI detection, immunohistochemistry or PCR-based protocols using a cohort of various sets of STR markers are recommended. Here we aimed to evaluate a simplified protocol using just a single STR marker, MT1XT20 mononucleotide repeat, for detection of MSI in Lynch syndrome patients. A Promega five-marker MSI testing panel and immunohistochemistry (IHC) were used as the gold standard in conjunction with MT1XT20. Materials and Methods: Colorectal patients with a positive history of familial cancers were selected by evaluating medical records. Based on Amsterdam II criteria for Lynch syndrome 20 families were short listed. DNA was extracted from formalin fixed paraffin embedded tumour and adjacent normal tissues resected from the index case in each family. Extracted DNA was subjected to MT1XT20 mononucleotide marker analysis and assessment with a commercially available five marker MSI testing kit (Promega, USA). IHC also was performed on tissue sections and the results were compared with PCR based data. Results: Eight (40%), seven (35%) and five (25%) cases were MSI positive using with the Promega kit, IHC and MT1XT20, respectively. Among the markers included in Promega kit, BAT26 marker showed instability in all 8 samples. NR24 and NR21 markers showed instability in 7 (87.5%), and BAT25 and MONO 27 in 6 (75%) and 5 (62.5%). Conclusions: Although MT1XT20 was earlier reported as a valid standalone marker for MSI testing in CRC patients, we could not verify this in our Iranian patients. Instead BAT26 among the markers included in Promega MSI testing kit showed instability in all 8 MSI-H CRC samples. Therefore, it seems BAT26 could act well as a single marker for MSI testing in Iranian CRC patients.

• Asian Pacific Journal of Cancer Prevention
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• 제14권4호
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• pp.2393-2399
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• 2013

Objective: Mitochondrial DNA (mtDNA) is considered a hotspot of mutations in various tumors. However, the relationship between microsatellite instability (MSI) and mtDNA copy number alterations in lung cancer has yet to be fully clarifieds. In the current study, we investigated the copy number and MSI of mitochondrial genome in lung carcinomas, as well as their significance for cancer development. Methods: The copy number and MSI of mtDNA in 37 matched lung carcinoma/adjacent histological normal lung tissue samples were examined by polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) assays for sequence variation, followed by sequence analysis and fluorogenic 5'-nuclease real-time PCR. Student's t test and linear regression analyses were employed to analyze the association between mtDNA copy number alterations and mitochondrial MSI (mtMSI). Results: The mean copy number of mtDNA in lung carcinoma tissue samples was significantly lower than that of the adjacent histologically normal lung tissue samples (p<0.001). mtMSI was detected in 32.4% (12/37) of lung carcinoma samples. The average copy number of mtDNA in lung carcinoma samples containing mtMSI was significantly lower than that in the other lung carcinoma samples (P<0.05). Conclusions: Results suggest that mtMSI may be an early and important event in the progression of lung carcinogenesis, particularly in association with variation in mtDNA copy number.

• Clinical Endoscopy
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• 제56권1호
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• pp.107-113
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• 2023

Background/Aims: Immune checkpoint blockade has recently been reported to be effective in treating microsatellite instability (MSI)-high tumors. Therefore, sufficient sampling of histological specimens is necessary in cases of unresectable pancreatic cancer (UR-PC). This multicenter study investigated the efficacy of endoscopic ultrasound-guided fine-needle biopsy (EUS-FNB) using a Franseen needle for MSI evaluation in patients with UR-PC. Methods: A total of 89 patients with UR-PC who underwent endoscopic ultrasound-guided fine-needle aspiration (EUS-FNA) or EUS-FNB using 22-G needles at three hospitals in Japan (2018-2021) were enrolled. Fifty-six of these patients (FNB 23 and FNA 33) were followed up or evaluated for MSI. Patient characteristics, UR-PC data, and procedural outcomes were compared between patients who underwent EUS-FNB and those who underwent EUS-FNA. Results: No significant difference in terms of sufficient tissue acquisition for histology was observed between patients who underwent EUS-FNB and those who underwent EUS-FNA. MSI evaluation was possible significantly more with tissue samples obtained using EUS-FNB than with tissue samples obtained using EUS-FNA (82.6% [19/23] vs. 45.5% [15/33], respectively; p<0.01). In the multivariate analysis, EUS-FNB was the only significant factor influencing the possibility of MSI evaluation. Conclusions: EUS-FNB using a Franseen needle is desirable for ensuring sufficient tissue acquisition for MSI evaluation.

• Journal of Digestive Cancer Research
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• 제10권2호
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• pp.65-73
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• 2022

A breakthrough in immunotherapy has changed the outlook for metastatic colorectal cancer (mCRC) treatment as the immune surveillance evasion mechanism of tumor cells has been continuously elucidated. Immune checkpoint inhibitors (ICI), such as pembrolizumab, nivolumab, and ipilimumab, which block immune checkpoint receptors or ligands have been approved for the treatment of mismatch repair deficient (dMMR)/microsatellite instability-high (MSI-H) mCRC based on numerous clinical studies. However, 50% of dMMR/MSI-H mCRC and most mismatch repair proficient/microsatellite stable mCRC remained unresponsive to current immunotherapy. Clinical trials on combination therapy that adds various treatments, such as target agents, chemotherapy, or radiation therapy to ICI, have been actively conducted to overcome this immunotherapy limitation. Further studies on safety and efficacy are needed although several trials presented promising data. Additionally, dMMR/MSI-H, tumor mutation burden, and programmed cell death ligand-1 expression have been studied as biomarkers for predicting the treatment response to immunotherapy, but the discovery and validation of more sensitively predictable biomarkers remained necessary. Thus, this study aimed to review recent studies on immunotherapy in mCRC, summarize the efficacy and limitation of immunotherapy, and describe the biomarkers that predict treatment response.

• IMMUNE NETWORK
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• 제2권4호
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• pp.208-216
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• 2002

Background: Reactive oxygen and nitrogen are produced by rheumatoid arthritis (RA) synovial tissue and can induce mutations in key genes. Normally, this process is prevented by a DNA mismatch repair (MMR) system that maintains sequence fidelity. Key members of the MMR system include MutS${\alpha}$ (comprised of hMSH2 and hMSH6), which can sense and repair single base mismatches and 8-oxoguanine, and MutS${\beta}$ (comprised of hMSH2 and hMSH3), which repairs longer insertion/deletion loops. Methods: To provide further evidence of DNA damage, we analyzed synovial tissues for microsatellite instability (MSI). MSI was examined by PCR on genomic DNA of paired synovial tissue and peripheral blood cells (PBC) of RA patients using specific primer sequences for 5 key microsatellites. Results: Surprisingly, abundant MSI was observed in RA synovium compared with osteoarthritis (OA) tissue. Western blot analysis of the same tissues for the expression of MMR proteins demonstrated decreased hMSH6 and increased hMSH3 in RA synovium. To evaluate potential mechanisms of MMR regulation in arthritis, fibroblast-like synoviocytes (FLS) were isolated from synovial tissues and incubated with the nitric oxide donor S-nitroso-N-acetylpenicillamine (SNAP). Western blot analysis demonstrated constitutive expression of hMSH2, 3 and 6 in RA and OA FLS. When FLS were cultured with SNAP, the RA synovial pattern of MMR expression was reproduced (high hMSH3, low hMSH6). Conclusion: Therefore, oxidative stress can relax the DNA MMR system in RA by suppressing hMSH6. Decreased hMSH6 can subsequently interfere with repair of single base mutations, which is the type observed in RA. We propose that oxidative stress not only creates DNA adducts that are potentially mutagenic, but also suppresses the mechanisms that limit the DNA damage.

• Journal of Yeungnam Medical Science
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• 제39권2호
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• pp.141-149
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• 2022

Background: The present study evaluated the clinical implications of adjuvant chemotherapy according to the mismatch repair (MMR) status and clinicopathologic features of patients with intermediate- and high-risk stage II colon cancer (CC). Methods: This study retrospectively reviewed 5,774 patients who were diagnosed with CC and underwent curative surgical resection at Kyungpook National University Chilgok Hospital. The patients were enrolled according to the following criteria: (1) pathologically diagnosed with primary CC; (2) stage II CC classified based on the 7th edition of the American Joint Committee on Cancer staging system; (3) intermediate- and high-risk features; and (4) available test results for MMR status. A total of 286 patients met these criteria and were included in the study. Results: Among the 286 patients, 54 (18.9%) were identified as microsatellite instability-high (MSI-H) or deficient MMR (dMMR). Although all the patients identified as MSI-H/dMMR showed better survival outcomes, T4 tumors and adjuvant chemotherapy were identified as independent prognostic factors for survival. For the intermediate-risk patients identified as MSI-low (MSI-L)/microsatellite stable (MSS) or proficient MMR (pMMR), adjuvant chemotherapy exhibited a significantly better disease-free survival (DFS) but had no impact on overall survival (OS). Oxaliplatin-containing regimens showed no association with DFS or OS. Adjuvant chemotherapy was not associated with DFS in intermediate-risk patients identified as MSI-H/dMMR. Conclusion: The current study found that the use of adjuvant chemotherapy was correlated with better DFS in MSI-L/MSS or pMMR intermediate-risk stage II CC patients.

• Journal of Gastric Cancer
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• 제23권1호
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• pp.224-249
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• 2023

Gastric cancer is heterogeneous in morphology, biology, genomics, and treatment response. Alterations in human epidermal growth factor receptor 2 (HER2) overexpression, microsatellite instability (MSI) status, programmed death-ligand 1 (PD-L1) levels, and fibroblast growth factor receptor 2 (FGFR2) can be used as biomarkers. Since the combination of fluoropyrimidine/platinum plus trastuzumab that was investigated in the ToGA trial was approved as a standard of care in HER2-positive patients in 2010, no other agents showed efficacy in the first- (HELOISE, LOGiC, JACOB trials) and second- (TyTAN, GATSBY, T-ACT trials) line treatments. Despite the success in treating breast cancer, various anti-HER2 agents, including a monoclonal antibody (pertuzumab), an antibody-drug conjugate (ADC; trastuzumab emtansine [T-DM1]), and a small molecule (lapatinib) failed to translate into clinical benefits until the KEYNOTE-811 (first-line) and DESTINY-Gastri01 (≥second-line) trials were conducted. The incorporation of HER2-directed treatment with immune checkpoint inhibitors in the form of a monoclonal antibody or ADC is now approved as a standard treatment. Despite the promising results of new agents (engineered monoclonal antibodies, bi-specific antibodies, fusion proteins, and small molecules) in the early phase of development, the management of HER2-positive gastric cancer requires further optimization to achieve precision medicine with a chemotherapeutic backbone. Treatment resistance is a complex process that can be overcome using a combination of chemotherapy, targeted agents, and immune checkpoint inhibitors, including novel agents. HER2 status must be reassessed in patients undergoing anti-HER2 treatment with disease progression after the first-line treatment. As a general guideline, patients who need systemic treatment should receive chemotherapy plus targeted agents, anti-angiogenic agents, immune checkpoint inhibitors, or their combinations.