MutS Homolog 2 Expression Research Articles

Association Between the Protein Expressions of MutS Homologs and Villin and the Clinicopathological Characteristics in 310 Colon Cancer Patients

To examine the relationship between the expressions of mismatch repair proteins, MutS homolog 2 (MSH2) and MutS homolog 6 (MSH6), and villin and the pathological features in patients with colon cancer. A total of 310 cases of colon cancer patients who were treated at our hospital between January 2017 and September 2021 were selected. The diagnosis of colon cancer of all patients was verified by pathological evaluation. Immunohistochemistry was used to determine the protein expressions of MSH2, MSH6, and villin. The correlation between the expressions of MSH2, MSH6, and villin and the clinicopathological parameters in patients with colon cancer was analyzed accordingly. Multivariate logistic regression was used to analyze the correlation between the expressions of MSH2, MSH6, and villin and the clinicopathological parameters of colon cancer. Kaplan-Meier survival curve was used to compare the 2-year survival rates of colon cancer patients with different expression levels of the proteins. Among the 310 patients with colon cancer, the negative expression rates of MSH2, MSH6, and villin proteins in cancer tissues were 8.71% (27/310), 9.35% (29/310), and 46.13% (143/310), respectively. The negative expression rates of the three proteins in tissues adjacent to cancer were 3.23% (10/310), 4.19% (13/310), and 9.68% (30/310), respectively. The negative expression rates of the three proteins in cancer tissues were all higher than those in adjacent tissues (P<0.05). Regression analysis showed that the expression of MSH2 and MSH6 in cancer tissues was correlated with the age, the location of tumor lesions, tumor differentiation degree, and lymph node metastasis in colon cancer patients (P<0.05). The expression of villin in the cancer tissue is correlated with the depth of tumor infiltration, lymph node metastasis, distant metastasis, and clinical staging status in colon cancer patients (P<0.05). The 2-year survival rates of patients with negative expressions of MSH2 and MSH6 were 51.85% and 44.83%, respectively, which were lower than those of patients with positive expression of MSH2 and MSH6 (79.51% and 80.43%, P<0.05). Thirteen patients (4.1%) had negative expression of MSH2, MSH6, and villin (referred to as "triple negative expressions") in the cancer tissues, and their 2-year survival rate was 30.77%, which was lower than that of colon cancer patients who did not meet the criteria for triple negative expressions (79.12% [235/297], P<0.05). The expressions of MSH2, MSH6, and villin are closely correlated with the pathological features of colon cancer patients. Evaluating the expression of the three proteins may assist in the clinical diagnosis, treatment, and prognosis evaluation of colon cancer.

Mismatch Repair Deficient (dMMR) Colorectal Carcinoma in a Pakistani Cohort: Association With Clinical and Pathological Parameters.

Introduction Microsatellite instability (MSI) is an important pathway in colorectal carcinoma (CRC) pathogenesis. MSI occurs due to mutations in mismatch repair (MMR) genes that include MutL protein homolog 1 (MLH1), postmeiotic segregation increased 2 (PMS2), MutS homolog 2 (MSH2), and MutS homolog 6 (MSH6). CRC with MSI is termed MMR deficient (dMMR) CRC. Conversely, CRC with intact MMR genes is called microsatellite stable (MSS) or MMR proficient (pMMR). In this study, we compared the clinicopathological features of dMMR CRC with pMMR CRC. Methods It was a retrospective study conducted in the Department of Histopathology, Liaquat National Hospital, Karachi, Pakistan, from March 2020 to February 2022, over a duration of twoyears. Biopsy-proven cases of CRC with upfront surgical resection were included in the study. Microscopic examination was performed to evaluate tumor type, grade, and extent of invasion, presence of necrosis, perineural invasion (PNI), lymphovascular invasion (LVI), peritumoral lymphocytes (PTL), intratumoral lymphocytes (ITL), and nodal metastasis. Immunohistochemical staining was performed using antibodies, namely, MLH1, PMS2, MSH2, and MSH6. Any loss of nuclear expression in tumor cells was termed dMMR or microsatellite instable, whereas the intact nuclear expression in tumor cells was labeled as MSS or pMMR. Results A total of 135 cases of CRC were included in the study. The mean age at diagnosis was 46.76 ± 17.74 years, with female predominance (60.7%). The loss of MLH1, PMS2, MSH2, and MSH6 expression was noted in 39.3%, 34.1%, 17.8%, and 16.3% cases, respectively. Overall, 59.3% of CRCs were pMMR, while 40.7% were dMMR. A significant association of MMR status was noted with respect to age, PNI, LVI, tumor grade, tumor (T) and nodal (N) stage, mucinous differentiation, and ITL. dMMR CRC was significantly above 50 years than pMMR CRC. The frequency of PNI and LVI was lower in dMMR CRC than in pMMR CRC. Conversely, the higher grade (grade 3) and higher T-stage (T4) were associated with dMMR CRC. Alternatively, the frequency of higher N stage (N2b) was more commonly seen in pMMR CRC. Moreover, mucinous differentiation and ITL were significantly associated with dMMR CRC. Conclusion A significant proportion of CRC patients in our population demonstrated dMMR status. dMMR CRC had a higher histological grade with a higher frequency of mucinous differentiation and higher T-stage. Conversely, the presence of LVI, PNI, and higher N stages were associated with pMMR CRC.

High MutS homolog 2 expression predicts poor prognosis and is related to immune infiltration in endometrial carcinoma.

Several studies have shown that MutS homolog 2 (MSH2) is highly expressed in many cancer tissues. Transcriptome expression data were collected from the Cancer Genome Atlas (TCGA) database. We analyzed the expression of MSH2 in normal and tumor tissues, the relationship between MSH2 expression and various prognostic factors, and the relationship between MSH2 expression and overall survival, disease specific survival, and progression free interval. We also examined MSH2 promoter methylation between endometrial cancer and normal endometrial tissues, and identified the prognostic value of MSH2 methylation in endometrial cancer. MSH2 was highly expressed in endometrial cancer tumor tissues compared with normal tissues. High MSH2 expression might be an independent prognostic factor for OS, DSS, and PFI. Further, high MSH2 expression was correlated with age and histological type, but not with BMI, clinical stage, tumor invasion, or other clinical features. MSH2 promoter methylation in endometrial cancer was significantly lower than in normal tissues. Additionally, MSH2 levels, OS, DSS, and PFI were associated with BMI, age, tumor invasion, and histological type. ssGSEA showed that MSH2 expression was positively correlated with the infiltration of Th2 cells, Tcm cells, T helper cells, and Tgd cells, whereas it was negatively correlated with NK CD56 bright cells, pDC cells, iDC cells, cytotoxic cells, and neutrophils. Increased MSH2 expression and reduced MSH2 methylation in endometrial cancer predicts poor prognosis. MSH2 may be used as a biomarker for the diagnosis and prognosis of endometrial cancer and as an immunotherapy target.

An Unexpected Esophageal Lesion in a Patient With Muir-Torre Syndrome

Question: In a 52-year-old female patient with a history of sebaceous gland neoplasms of the skin (carcinoma resected in 2017 and several subsequent adenomas) and positive family history for early-onset colorectal cancer (father at the age of 39 years), Muir-Torre syndrome was suspected. This is a rare variant of Lynch syndrome (LS; approximately 10% of individuals with LS) clinically defined by the typical LS tumor spectrum (colorectal cancer as well as extracolonic tumors, eg, endomtetrial/ovarian cancer, urinary tract cancer) and additional increased risk for characteristic skin neoplasms (especially sebaceous gland neoplasms and keratoacanthoma). DNA mismatch-repair (MMR) deficiency resulting in an accumulation of somatic mutations throughout the genome, also affecting genes involved in carcinogenesis, causes LS. Genetic testing identified a pathogenic germline mutation in MSH2 (mutS homolog 2) on chromosome 2p21 and confirmed the diagnosis in 2018. Compliant with current international guidelines, the patient was included in a specific tumor-screening program. In dermatologic follow-up examinations, basal cell carcinoma and squamous cell carcinoma of the skin were detected. By annual surveillance colonoscopies up to the present, 4 colorectal adenomas with sizes from 2 to 15 mm were resected. On an individual basis, and not covered by guidelines, we performed yearly surveillance esophagogastroduodenoscopy (EGD). Interestingly, at the age of 57 years, a small irregular and slightly elevated lesion (8 mm) with small central erosion (Figure A, arrow) was observed (Paris 0-IIa) in the mid-esophagus (25 cm from incisors). The central part of the lesion stained negative during chromoendoscopy with Lugol’s iodine (1%) (Figure B, arrow) and showed an irregular surface pattern with virtual chromoendoscopy (NBI mode; narrow band imaging) (Figure C). Therefore, malignancy was suspected, and the lesion was removed en bloc by means of rubber-band ligation assisted endoscopic mucosal resection (Figures D and E). Of note, the patient was never a smoker and only occasionally consumed alcohol. Endoscopies were performed with Olympus GIF-H190 endoscopes (Olympus, Hamburg, Germany). Which diagnosis do you suspect and is this lesion LS associated? Look on page 189 for the answer and see the Gastroenterology website (www.gastrojournal.org) for more information on submitting to Gastro Curbside Consult. Histopathologic and immunohistochemical examination of the resected tumor revealed poorly differentiated invasive squamous cell carcinoma (pT1a, Pn0, V0, R0, G3) (Figure F, hematoxylin and eosin [HE] stain, ×40) with focal invasion of the lamina muscularis mucosae (Figure G, HE, ×200, arrow). Molecular microsatellite instability testing discovered instability in 4/5 markers (BAT-26, NR-21, BAT-25, and NR-24; NR-27 was stable). When an LS-associated tumor was suspected, MMR protein immunohistochemistry showed a loss of MSH2 expression within the neoplastic cells (Figure H, ×200, red arrow) while surrounding tissue stained positive for MSH2 (Figure H, black arrow) and MLH1 expression was unaffected in neoplastic (Figure I, ×200, red arrow) and nonneoplastic (Figure I, black arrow) cells. Computed tomography and endoscopic ultrasound did not find any distant or lymph-node metastases, and there was no residual tumor in a follow-up endoscopy. Because of poor tumor differentiation and invasion of the lamina muscularis mucosae (m3), additive radiotherapy (50.4 Gy/59.92 Gy boost in 28 fractions) was recommended after discussion by the tumor board. This is the first description of an LS/Muir-Torre syndrome–associated squamous cell carcinoma of the esophagus in a patient without typical risk factors for this tumor entity. Moreover, we show in-depth molecular characterization to prove LS association. Only rarely have adenocarcinomas of the esophagus been reported1Sweetser S. Chandan V.S. Baron T.H. Dysphagia in Lynch syndrome.Gastroenterology. 2013; 145: 1167-1168Abstract Full Text Full Text PDF Scopus (6) Google Scholar in LS. Until recently, squamous cell carcinoma of the skin was not counted as typical skin manifestation of Muir-Torre syndrome, but an association has been demonstrated.2Ykema B.L.M. Adan F. Crijns M.B. et al.Cutaneous squamous cell carcinoma is associated with Lynch syndrome: widening the spectrum of Lynch syndrome-associated tumours.Br J Dermatol. 2021; 185: 462-463Crossref PubMed Scopus (7) Google Scholar Of note, our patient also suffered from squamous cell carcinoma of the skin. In conclusion, clinicians should carefully consider esophageal neoplasms as a rare manifestation of LS. Despite limited data supporting EGD surveillance in LS and in contrast to current guidelines, upper endoscopy could be easily performed along with routine colonoscopy in an effort to prevent morbidity and mortality from upper GI manifestations of LS (early-stage cancer observed in about 1.5% of asymptomatic patients3Farha N. Hrabe J. Sleiman J. Beard J. et al.Clinically actionable findings on surveillance EGD in asymptomatic patients with Lynch syndrome.Gastrointest Endosc. 2022; 95: 105-114Abstract Full Text Full Text PDF PubMed Scopus (8) Google Scholar).

Potential Influence of Age and Diabetes Mellitus Type 1 on MSH2 (MutS homolog 2) Expression in a Rat Kidney Tissue

Background: Homeostasis of proliferating tissues is strongly dependent on intact DNA. Both neoplastic and non-neoplastic diseases have been associated with MSH2 (MutS homolog 2, a mismatch repair protein) deficiency. In this study, we examined how age and diabetes mellitus influence the expression of MSH2 in the kidney. Methods: To study the effect of age, three groups of healthy rats were formed: 2 months, 8 months, and 14 months old. Two groups of diabetic rats were formed: 8 months old and 14 months old. Expression of MSH2 in the kidney was studied by quantifying immunofluorescent staining. Results: Age was identified as the main factor that influences MSH2 expression in kidneys. The effect of age followed parabolic dynamics, with peak expression at 8 months of age and similar levels at 2 and 14 months. Diabetes had an age-dependent effect, which manifested as the increase of MSH2 expression in 14-month-old diabetic rats in comparison to healthy animals. Conclusions: Age influences MSH2 expression in the kidney more than diabetes mellitus. Since ageing is a risk factor for kidney neoplasia, downregulation of MSH2 in older rats might represent one of the pro-oncogenic mechanisms of ageing at a molecular level.

Andrias davidianus Ranavirus (ADRV) Genome Replicate Efficiently by Engaging Cellular Mismatch Repair Protein MSH2.

As nucleocytoplasmic large DNA viruses, replication of ranaviruses (genus Ranavirus, family Iridoviridae) involves a series of viral and host proteins. We have described that the replication and transcription machinery of Andrias davidianus ranavirus (ADRV) which was isolated from the Chinese giant salamander contained host factors. Here, a new host factor, the MutS homolog 2 (MSH2), was proved as an important protein that participated in ADRV infection. Expression of MSH2 was stable during ADRV infection in cultured cells and it localized at the cytoplasmic viral factories and colocalized with virus nascent DNA, indicating its possible role in virus genome replication. Investigation of the viral proteins that interacted with MSH2 by co-immunoprecipitation showed that A. davidianus MSH2 can interact with ADRV-35L (possible components associated with virus transcription), ADRV-47L (virus DNA polymerase), and ADRV-98R. Further knockdown MSH2 expression by RNAi significantly reduced the late gene expression of ADRV. Additionally, MSH2 knockout by CRISPR/Cas9 significantly reduced viral titers, genome replication, and late gene transcription of ADRV. Thus, the current study proved that ADRV can engage cellular MSH2 for its efficient genome replication and late gene transcription, which provided new information for understanding the roles of host factors in ranavirus replication and transcription.

A Pan-Cancer Analysis on the Systematic Correlation of MutS Homolog 2 (MSH2) to a Malignant Tumor.

MutS homolog 2 (MSH2) is a crucial participant in human DNA repair, and lots of the studies functionally associated with it were begun with hereditary nonpolyposis colorectal cancer (HNPCC). MSH2 has also been reported to take part in the progresses of various tumors' formation. With the help of GTEx, CCLE, and TCGA pan-cancer databases, the analysis of MSH2 gene distribution in both tumor tissues and normal control tissues was carried out. Kaplan-Meyer survival plots and COX regression analysis were conducted for the assessment into the MSH2's impact on tumor patients' clinical prognosis. In an investigation to the association of MSH2 expression with immune infiltration level of various tumors and a similar study on tumor immune neoantigens, microsatellite instability was subsequently taken. It was found that high expression of MSH2 is prevalent in most cancers. MSH2's efficacy on clinical prognosis as well as immune infiltration in tumor patients revealed a fact that expression of MSH2 in prostate adenocarcinoma (PRAD), brain lower-grade glioma (LGG), breast-invasive carcinoma (BRCA), and head and neck squamous cell carcinoma (HNSC) posed a significant correlation with the immune cell infiltration level of patients. Likewise as above, MSH2's expression comes in a similar trend with tumor immune neoantigens and microsatellite instability. MSH2's expression in the majority of tumors is a direct factor to the activation of tumor-associated pathways as well as immune-associated pathways. MSH2's early screening or even therapeutic target role for sarcoma (SARC) diagnosis is contributing to the efficiency of early screening and overall survival in SARC patients.

Analysis of the Expression and Prognostic Value of MSH2 in Pan-Cancer Based on Bioinformatics.

Background MutS homolog 2 (MSH2), with the function of identifying mismatches and participating in DNA repair, is the “housekeeping gene” in the mismatch repair (MMR) system. MSH2 deficiency has been reported to enhance cancer susceptibility for the association of hereditary nonpolyposis colorectal cancer. However, the expression and prognostic significance of MSH2 have not been studied from the perspective of pan-cancer. Methods The GTEx database was used to analyze the expression of MSH2 in normal tissues. The TCGA database was used to analyze the differential expression of MSH2 in pan-cancers. The prognostic value of MSH2 in pan-cancer was assessed using Cox regression and Kaplan-Meier analysis. Spearman correlations were used to measure the relationship between the expression level of MSH2 in pan-cancer and the level of immune infiltration, tumor mutational burden (TMB), and microsatellite instability (MSI). Results MSH2 is highly expressed in most type of cancers and significantly correlated with prognosis. In COAD, KIRC, LIHC, and SKCM, the expression of MSH2 was significantly positively correlated with the abundance of B cells, CD4+ T cells, CD8+ T cells, dendritic cells, macrophages, and neutrophils. In THCA, MSH2 expression correlated with CD8+T Cell showed a significant negative correlation. MSH2 had significantly negative correlations with stromal score and immune score in a variety of cancers and significantly correlated with TMB and MSI of a variety of tumors. Conclusions MSH2 may play an important role in the occurrence, development, and immune infiltration of cancer. MSH2 can emerge as a potential biomarker for cancer diagnosis and prognosis.

Association of MSH2 Expression With Tumor Mutational Burden and the Immune Microenvironment in Lung Adenocarcinoma.

Immune checkpoint blockade (ICB) therapies that target programmed cell death 1 (PD1) and PD1 ligand 1 (PDL1) have demonstrated promising benefits in lung adenocarcinoma (LUAD), and tumor mutational burden (TMB) is the most robust biomarker associated with the efficacy of PD-1-PD-L1 axis blockade in LUAD, but the assessment of TMB by whole-exome sequencing (WES) is rather expensive and time-consuming. Although targeted panel sequencing has been developed and approved by the US Food and Drug Administration (FDA) to estimate TMB, we found that its predictive accuracy for ICB response was significantly lower than WES in LUAD. Given that previous studies were mainly focusing on genomic variations to explore surrogate biomarkers of TMB, we turned to examine the transcriptome-based correlation with TMB in this study. Combining three immunotherapeutic cohorts with two independent The Cancer Genome Atlas (TCGA) datasets, we revealed that the expression of mutS homolog 2 (MSH2), one of the most crucial genes involved in DNA mismatch repair (MMR) pathway, was the strongest feature associated with increased TMB in multivariate analysis. Furthermore, MSH2 expression also displayed a significantly positive correlation with smoking signature while an inverse association with MMR deficiency (MMRd) signature in LUAD. More importantly, high expression of MSH2 markedly correlated with increased PD-L1 expression and CD8+ T cell infiltration, both suggesting a prominent immunotherapy-responsive microenvironment in LUAD. Notably, detecting MSH2 expression is much easier, faster, and cheaper than TMB in clinical practice. Taken together, this study demonstrates the association of MSH2 expression with TMB and the immune microenvironment in LUAD. MSH2 expression may be developed as a potential surrogate biomarker of TMB to identify ICB responders in LUAD.

Analysis of MSH2 Loss of Heterozygosity, Expression, and IVS10+12G>A Polymorphism in Sporadic Colon Cancer.

mutS homolog 2 (MSH2) deficiency may be involved in the development of microsatellite instability found in certain sporadic colorectal tumors. In addition to mutations or loss of heterozygosity resulting in complete loss of MSH2 function, polymorphisms affecting MSH2 expression have been also identified. Therefore, the aim of this study was to examine MSH2 status in sporadic colon cancer. MSH2 status was examined at the DNA, RNA and protein levels through loss of heterozygosity (LOH) analysis, quantitative real-time PCR and immunohistochemistry. MSH2 IVS10+12A>G polymorphism was examined by real-time single nucleotide polymorphism genotyping. MSH2 LOH was more frequent in tumors larger than 5 cm (p=0.032), mRNA expression was also significantly lower and the same expression pattern was present in the corresponding normal mucosa of the same patient (p=0.013 and p=0.008, respectively). No association was found between IVS10+12A>G polymorphism and susceptibility to sporadic colon cancer. Altered MSH2 expression detected in sporadic colon tumors pointing to its role in colorectal tumorigenesis without a hereditary component.

Mismatch repair protein expression in patients with stage II and III sporadic colorectal cancer.

Colorectal cancer (CRC) may be classified according to the level of microsatellite instability exhibited by the tumor. The malignant transformation of normal colonic mucosae to carcinomas may be accelerated by the loss or inactivation of DNA mismatch repair (MMR) genes. The present study examined the expression of certain MMR proteins [namely, MutL homolog 1 (MLH1), MutS homolog 2 (MSH2), MutS homolog 6 (MSH6) and PMS1 homolog 2 (PMS2)] in patients with stage II and III sporadic CRC. The association between the expression of these proteins, and the clinicopathological characteristics of patients with CRC and their tumors, was investigated. MMR protein expression was examined using immunohistochemistry. MLH1, MSH2, MSH6 and PMS2 protein expression was detected in 78.4% (120/153), 75.2% (115/153), 44.4% (68/153) and 79.7% (122/153) of stage II and III sporadic CRCs, respectively. Additionally, the expression of MLH1 and MSH6 was revealed to be significantly higher in stage III tumors when compared with stage II tumors (P<0.05). MLH1 and MSH6 negative tumors were larger, poorly differentiated and exhibited extraserosal invasion with infrequent lymph node metastasis (P<0.05). Patients with defects in MLH2 and PMS2 also had large tumors that exhibited extraserosal invasion and infrequent lymph node metastasis (P<0.05). No statistically significant associations were observed between MLH1, MSH2, MSH6 or PMS2 protein expression and patient age, sex, tumor localization or angiolymphatic invasion status (P>0.05). From the present study, it was concluded that MMR protein expression status evaluation may increase the efficiency of MMR testing and be useful in improving the individualized approach to patient monitoring and therapy.

Down-Regulation of MutS Homolog 2 (MSH2) Expression by Curcumin Enhances Cytotoxicity Induced by Gemcitabine in Human Lung Adenocarcinoma Cells

Gemcitabine (2′,2′-difluorodeoxycytidine) is a difluorinated analog of deoxycytidine. It is used clinically to treat patients with non-small-cell lung cancer (NSCLC). Curcumin is a yellow pigment derived from the rhizome of Curcuma longa, and has been proven to have antioxidant and antitumor properties. Human MutS homolog 2 (MSH2) is a key DNA mismatch repair protein that plays an important role in maintaining genomic stability. Depletion of MSH2 from cells can reverse resistance to certain DNA-damaging agents. In this study, exposure of human lung adenocarcinoma A549 and H1975 cells to gemcitabine increased protein phosphorylation of MKK3/6 and p38 MAPK in a time- and dose-dependent manner; this was accompanied by increased expression of MSH2 mRNA and protein. Gemcitabine-induced cytotoxicity was significantly enhanced by MSH2 siRNA transfection or inactivation of p38 MAPK by SB202190 or p38 MAPK siRNA transfection. However, overexpression of MSH2 cDNA reduced gemcitabine-induced cytotoxicity. Furthermore, curcumin enhanced gemcitabine-induced cytotoxicity via inactivation of MKK3/6-p38 MAPK and downregulation of MSH2. Enforced expression of constitutively active MKK6 rescued cell viability and restored MSH2 protein levels that were suppressed by curcumin and gemcitabine. Suppression of MSH2 expression and a combination with curcumin may be considered as potential therapeutic modalities for gemcitabine-resistant NSCLC cells.

Identification of Polycomb Group Protein EZH2-Mediated DNA Mismatch Repair Gene MSH2 in Human Uterine Fibroids.

Uterine fibroids (UFs) are benign smooth muscle neoplasms affecting up to 70% of reproductive age women. Treatment of symptomatic UFs places a significant economic burden on the US health-care system. Several specific genetic abnormalities have been described as etiologic factors of UFs, suggesting that a low DNA damage repair capacity may be involved in the formation of UF. In this study, we used human fibroid and adjacent myometrial tissues, as well as an in vitro cell culture model, to evaluate the expression of MutS homolog 2 (MSH2), which encodes a protein belongs to the mismatch repair system. In addition, we deciphered the mechanism by which polycomb repressive complex 2 protein, EZH2, deregulates MSH2 in UFs. The RNA expression analysis demonstrated the deregulation of MSH2 expression in UF tissues in comparison to its adjacent myometrium. Notably, protein levels of MSH2 were upregulated in 90% of fibroid tissues (9 of 10) as compared to matched adjacent myometrial tissues. Human fibroid primary cells treated with 3-deazaneplanocin A (DZNep), chemical inhibitor of EZH2, exhibited a significant increase in MSH2 expression (P < .05). Overexpression of EZH2 using an adenoviral vector approach significantly downregulated the expression of MSH2 (P < .05). Chromatin immunoprecipitation assay demonstrated that enrichment of H3K27me3 in promoter regions of MSH2 was significantly decreased in DZNep-treated fibroid cells as compared to vehicle control. These data suggest that EZH2-H3K27me3 regulatory mechanism dynamically changes the expression levels of DNA mismatch repair gene MSH2, through epigenetic mark H3K27me3. MSH2 may be considered as a marker for early detection of UFs.

Ubiquitin-specific Peptidase 10 (USP10) Deubiquitinates and Stabilizes MutS Homolog 2 (MSH2) to Regulate Cellular Sensitivity to DNA Damage

MSH2 is a key DNA mismatch repair protein, which plays an important role in genomic stability. In addition to its DNA repair function, MSH2 serves as a sensor for DNA base analogs-provoked DNA replication errors and binds to various DNA damage-induced adducts to trigger cell cycle arrest or apoptosis. Loss or depletion of MSH2 from cells renders resistance to certain DNA-damaging agents. Therefore, the level of MSH2 determines DNA damage response. Previous studies showed that the level of MSH2 protein is modulated by the ubiquitin-proteasome pathway, and histone deacetylase 6 (HDAC6) serves as an ubiquitin E3 ligase. However, the deubiquitinating enzymes, which regulate MSH2 remain unknown. Here we report that ubiquitin-specific peptidase 10 (USP10) interacts with and stabilizes MSH2. USP10 deubiquitinates MSH2 in vitro and in vivo Moreover, the protein level of MSH2 is positively correlated with the USP10 protein level in a panel of lung cancer cell lines. Knockdown of USP10 in lung cancer cells exhibits increased cell survival and decreased apoptosis upon the treatment of DNA-methylating agent N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and antimetabolite 6-thioguanine (6-TG). The above phenotypes can be rescued by ectopic expression of MSH2. In addition, knockdown of MSH2 decreases the cellular mismatch repair activity. Overall, our results suggest a novel USP10-MSH2 pathway regulating DNA damage response and DNA mismatch repair.

Down-regulation of MSH2 expression by Hsp90 inhibition enhances cytotoxicity affected by tamoxifen in human lung cancer cells

The anti-estrogen tamoxifen has been used worldwide as an adjuvant hormone therapeutic agent in the treatment of breast cancer. However, the molecular mechanism of tamoxifen-induced cytotoxicity in non-small cell lung cancer (NSCLC) cells has not been identified. Human MutS homolog 2 (MSH2), a crucial element of the highly conserved DNA mismatch repair system, and expression of MSH2 have been down-regulated by Hsp90 function inhibition in human lung cancer. Therefore, in this study, we examined whether MSH2 plays a role in the tamoxifen and Hsp90 inhibitor-induced cytotoxic effect on NSCLC cells. The results showed that treatment with tamoxifen increased MSH2 mRNA and protein levels. The combination treatment with PI3K inhibitors (LY294002 or wortmannin) or knockdown AKT expression by specific small interfering RNA could decrease tamoxifen-induced MSH2 expression. Both knocking down MSH2 expression and co-treatment of PI3K inhibitors enhanced the cytotoxicity and cell growth inhibition of tamoxifen. Compared to a single agent alone, tamoxifen combined with an Hsp90 inhibitor resulted in cytotoxicity and cell growth inhibition synergistically in NSCLC cells, accompanied with reduced MSH2 expression. These findings may have implications for the rational design of future drug regimens incorporating tamoxifen and Hsp90 inhibitors for the treatment of NSCLC.

Down-regulation of MSH2 expression by an Hsp90 inhibitor enhances pemetrexed-induced cytotoxicity in human non-small-cell lung cancer cells

Elevated heat shock protein 90 (Hsp90) expression has been linked to poor prognosis in patients with non-small cell lung cancer (NSCLC). The multitargeted antifolate pemetrexed has demonstrated certain clinical activities against NSCLC. However, the efficacy of the combination of pemtrexed and Hsp90 inhibitor to prolong the survival of patients with NSCLC still remains unclear. Human MutS homolog 2 (MSH2), a crucial element of the highly conserved DNA mismatch repair system, and defects or polymorphisms of MSH2 have been found in lung cancer. In this study, we evaluated the effects of pemetrexed on NSCLC cell lines (H520 and H1703) and found that treatment with this drug at 20–50µM increased the MSH2 mRNA and protein levels in a MKK3/6–p38 MAPK signal activation-dependent manner. Furthermore, the knockdown of MSH2 expression by transfection with small interfering RNA of MSH2 or the blockage of p38 MAPK activation by SB202190 enhanced the cytotoxicity of pemetrexed. Combining the drug treatment with an Hsp90 inhibitor resulted in an enhanced pemetrexed-induced cytotoxic effect, accompanied with the reduction of MSH2 protein and mRNA levels. The expression of constitutively active MKK6 (MKK6E) or HA-p38 MAPK vectors significantly rescued the decreased p38 MAPK activity, and restored the MSH2 protein levels and cell survival in NSCLC cells co-treated with pemetrexed and Hsp90 inhibitor. In this study, we have demonstrated that down-regulation of the MKK3/6–p38 MAPK signal with the subsequent reduction of MSH2 enhanced the cytotoxic effect of pemetrexed in H520 and H1703 cells. The results suggest a potential future benefit of combining pemetrexed and the Hsp90 inhibitor to treat lung cancer.

Reduction of DNA mismatch repair protein expression in airway epithelial cells of premenopausal women chronically exposed to biomass smoke

Biomass burning is a major source of indoor air pollution in rural India. This study examined whether chronic inhalation of biomass smoke causes change in the DNA mismatch repair (MMR) pathway in the airway cells. For this, airway cells exfoliated in sputum were collected from 72 premenopausal nonsmoking rural women (median age 34years) who cooked with biomass (wood, dung, crop residues) and 68 control women who cooked with cleaner fuel liquefied petroleum gas (LPG) for the past 5years or more. The levels of particulate matters with diameters less than 10 and 2.5μm (PM10 and PM2.5) in indoor air were measured by real-time aerosol monitor. Benzene exposure was monitored by measuring trans,trans-muconic acid (t,t-MA) in urine by high-performance liquid chromatography with ultraviolet detector. Generation of reactive oxygen species (ROS) and level of superoxide dismutase (SOD) in airway cells were measured by flow cytometry and spectrophotometry, respectively. Immunocytochemical assay revealed lower percentage of airway epithelial cells expressing MMR proteins mutL homolog 1 (MLH1) and mutS homolog 2 (MSH2) in biomass-using women compared to LPG-using controls. Women who cooked with biomass had 6.7 times higher level of urinary t,t-MA, twofold increase in ROS generation, and 31% depletion of SOD. Indoor air of biomass-using households had three times more particulate matters than that of controls. ROS, urinary t,t-MA, and particulate pollution in biomass-using kitchen had negative correlation, while SOD showed positive correlation with MSH2 and MLH1 expression. It appears that chronic exposure to biomass smoke reduces MMR response in airway epithelial cells, and oxidative stress plays an important role in the process.

Reduced expression of mutS homolog 2 and mutL homolog 1 affects overall survival in laryngeal squamous cell carcinoma patients: Investigation into a potential cause

The risk factors affecting the survival rates of laryngeal carcinoma are not well understood. In this study, we investigated the expression status of mutS homolog 2 (MSH2) and mutL homolog 1 (MLH1) and examined the relationship between these two molecules and overall survival rates in laryngeal cancer. We also explored the potential reason for the altered expression of these two genes. Using real-time polymerase chain reaction and western blotting, we detected MSH2 and MLH1 expression in laryngeal cancer tissue samples. We collected a retrospective cohort with 180 laryngeal cancer patients, and inspected MSH2 and MLH1 staining with tissue microarray immunohistochemistry. Prognostic value of clinicopathological characteristics was evaluated by statistical analysis. Laryngeal carcinoma cells were co-cultured with Helicobacter pylori (H. pylori) bacteria. MSH2 and MLH1 were expressed at lower levels compared to those of adjacent tissues in 21 laryngeal carcinoma patients. Patients with negative expression of MSH2 and MLH1 tended to have a higher risk of mortality compared to patients with positive expression (HR=4.38; HR=3.0, respectively). Cigarette smoking rate was higher in the MLH1 expression positive group. H. pylori infection reduced the MSH2 and MLH1 expression levels of laryngeal carcinoma cell lines within co-culture conditions. It is suggested that the altered expression levels of MSH2 and MLH1 probably affect the overall survival of laryngeal carcinoma patients. H. pylori infection may have an effect on the expression of MSH2 and MLH1 in laryngeal carcinoma patients.

Context-Dependent Bidirectional Regulation of the MutS Homolog 2 by Transforming Growth Factor β Contributes to Chemoresistance in Breast Cancer Cells

The TGF-β, a tumor suppressive cytokine in normal cells, is abused in cancer to promote the malignancy. In this study, we reported that TGF-β downregulated the mutS homolog 2 (MSH2), a central component of the DNA mismatch repair (MMR) system, in HER2-transformed MCF10A mammary epithelial cells and in breast cancer (BC) cells. This was mediated by a TGF-β-induced micro RNA (miRNA), miR-21, which targeted the 3' untranslated region of MSH2 mRNA and downregulated its expression. A negative correlation between the expression of TGF-β1 and MSH2 was also detected in primary breast tumors. In contrast, TGF-β upregulated MSH2 in nontransformed cells through Smad-mediated, p53-dependent promoter activation, which was absent in BC cells with impaired p53 function. Although this upregulating mechanism also existed in MCF10A/HER2 and p53-proficient BC cells, both basal and TGF-β-induced MSH2 promoter activities were significantly lower than those in MCF10A. Moreover, the basal and TGF-β-induced miR-21 levels were markedly higher in transformed cells, suggesting that the preset levels of miR-21 and MSH2 promoter activity, which is affected by the p53 status, determine the outputs of the bidirectional regulation of MSH2 by TGF-β in a certain cellular context. We further found that by downregulating MSH2, TGF-β contributed to resistance to DNA-damaging chemotherapy agents in cancer cells. Our results indicated a regulatory antagonism between promoter activation and miRNA-mediated posttranscriptional inhibition underlying a dual effect of TGF-β on the DNA repair machinery, which may influence the genomic stability in a context-dependent manner and contribute to chemoresistance in cancer.

MSH2 and adjuvant cisplatin-based chemotherapy in non-small cell lung cancer

CRA7502 Background: Adjuvant cisplatin-based chemotherapy improves survival among patients with non-small cell lung cancer. The human MutS homolog 2 (MSH2) protein is required to repair cisplatin-DNA lesions. Methods: We used immunohistochemistry to determine MSH2 expression in specimens from patients who had been enrolled in the International Adjuvant Lung Trial. The long-term (median follow-up 7.5 years) overall survival benefit was evaluated in a Cox model adjusted on clinical and pathological variables. Results: Among 673 evaluable tumors, 257 (38%) were MSH2 positive and 416 (62%) were MSH2 negative. The long-term survival benefit of chemotherapy was likely different according to MSH2 expression (test for interaction, P=0.06): chemotherapy compared with observation prolonged survival in the MSH2 negative group (adjusted hazard ratio for death, 0.76; 95%CI, 0.59 to 0.97; P=0.03), but not in the MSH2 positive group (adjusted hazard ratio for death, 1.12; 95%CI, 0.81 to 1.55; P=0.48). In the control arm, the adjusted hazard ratio for death associated with MSH2 positivity compared to MSH2 negativity was 0.66 (95%CI, 0.49 to 0.90; P=0.01). Among 658 patients with available excision repair cross-complementing group 1 (ERCC1) data, the benefit of chemotherapy decreased with the number of positive markers among MSH2 and ERCC1 (P=0.01). Chemotherapy compared with observation prolonged survival in the combined MSH2 negative/ERCC1 negative subgroup (adjusted hazard ratio for death, 0.65; 95%CI, 0.47 to 0.91; P=0.01). Conclusions: MSH2 appears to predict a long-term benefit from adjuvant cisplatin-based chemotherapy in patients with non-small cell lung cancer and may be combined with ERCC1. Author Disclosure Employment or Leadership Consultant or Advisory Role Stock Ownership Honoraria Research Funding Expert Testimony Other Remuneration GlaxoSmithKline Eli Lilly