Tislelizumab in previously treated,locally advanced unresectable/metastatic microsatellite instability-high/mismatch repair-deficient solid tumors

Objective:The open-label,phase II RATIONALE-209 study evaluated tislelizumab(anti-programmed cell death protein 1 antibody)as a tissue-agnostic monotherapy for microsatellite instability-high(MSI-H)/mismatch repair-deficient(dMMR)tumors.Methods:Adults with previously treated,locally advanced unresectable or metastatic MSI-H/dMMR solid tumors were enrolled.Patients received tislelizumab 200 mg intravenously every 3 weeks.Objective response rate(ORR;primary endpoint),duration of response(DoR),and progression-free survival(PFS)were assessed by independent review committee(Response Evaluation Criteria in Solid Tumors v1.1).Results:Eighty patients were enrolled and treated;75(93.8%)patients had measurable disease at baseline.Most had metastatic disease and received at least one prior therapy for advanced/metastatic disease(n=79;98.8%).At primary analysis(data cutoff July 8,2021;median follow-up 15.2 months),overall ORR[46.7%;95%confidence interval(95%CI),35.1−58.6;one-sided P<0.0001]and ORR across tumor-specific subgroups[colorectal(n=46):39.1%(95%CI,25.1–54.6);gastric/gastroesophageal junction(n=9):55.6%(95%CI,21.2−86.3);others(n=20):60.0%(95%CI,36.1−80.9)]were significantly greater with tislelizumab vs.a prespecified historical control ORR of 10%;five(6.7%)patients had complete responses.Median DoR,PFS,and overall survival were not reached with long-term follow-up(data cutoff December 5,2022;median follow-up 28.9 months).Tislelizumab was well tolerated with no unexpected safety signals.Treatment-related adverse events(TRAEs)of grade≥3 occurred in 53.8%of patients;7.5%of patients discontinued treatment due to TRAEs.Conclusions:Tislelizumab demonstrated a significant ORR improvement in patients with previously treated,locally advanced unresectable or metastatic MSI-H/dMMR tumors and was generally well tolerated.

Application of immune checkpoint inhibitors and microsatellite instability in gastric cancer

In this editorial we comment on the article by Li published in the recent issue of the World Journal of Gastroenterology.We focus specifically on the application of immune checkpoint inhibitors(ICIs)and microsatellite instability(MSI)in gastric cancer(GC).The four pillars of GC management have long been considered,including surgery,chemotherapy,radiotherapy and targeted therapy.However,immunotherapy has recently emerged as a“fifth pillar”,and its use is rapidly expanding.There are four principal strategies for tumor immunotherapy:ICIs,tumor vaccines,adoptive immunotherapy and nonspecific immunomodulators.Of them,ICIs are the most advanced and widespread type of cancer immunotherapy for GC.Recent breakthrough results for ICIs have paved the way to a new era of cancer immunotherapy.In particular,inhibition of the PD-1/PD-L1 axis with ICIs,including nivolumab and pembrolizumab,has emerged as a novel treatment strategy for advanced GC.Unfortunately,these therapies are sometimes associated with often subtle,potentially fatal immune-related adverse events(irAEs),including dermatitis,diarrhea,colitis,endocrinopathy,hepatotoxicity,neuropathy and pneumonitis.We must be aware of these irAEs and improve the detection of these processes to prevent inappropriate discharges,emergency department revisits,and downstream complications.Recent studies have revealed that MSI-high or mismatch-repair-deficient tumors,regardless of their primary site,have a promising response to ICIs.So,it is important to detect MSI before applying ICIs for treatment of GC.

Comparative effectiveness of immunotherapy and chemotherapy in patients with metastatic colorectal cancer stratified by microsatellite instability status

BACKGROUND Immunotherapy have demonstrated promising outcomes in patients with high microsatellite instability(MSI)(MSI-H)metastatic colorectal cancer.However,the comparative effectiveness of Immunotherapy and chemotherapy for patients with low MSI(MSI-L),and microsatellite stable(MSS)metastatic colorectal cancer remains unclear.AIM To investigate immunotherapy vs chemotherapy for treatment of MSI-L/MSS metastatic colorectal cancer,and to evaluate the success of immunotherapy against chemotherapy in managing MSI-H metastatic colorectal cancer during a follow-up of 50 months.METHODS We conducted a retrospective cohort study using the National Cancer Database(NCDB)to evaluate the overall survival(OS)of patients with metastatic colorectal cancer treated with immunotherapy or chemotherapy.The study population was stratified by MSI status(MSI-H,MSI-L,and MSS).Multivariable Cox proportional hazard models were used to assess the association between treatment modality and OS,adjusting for potential confounders.RESULTS A total of 21951 patients with metastatic colorectal cancer were included in the analysis,of which 2358 were MSI-H,and 19593 were MSI-L/MSS.In the MSI-H cohort,immunotherapy treatment(n=142)was associated with a significantly improved median OS compared to chemotherapy(n=860).After adjusting for potential confounders,immunotherapy treatment remained significantly associated with better OS in the MSI-H cohort[adjusted hazard ratio(aHR):0.57,95%confidence interval(95%CI):0.43-0.77,P<0.001].In the MSS cohort,no significant difference in median OS was observed between immunotherapy treatment and chemotherapy(aHR:0.94,95%CI:0.69-1.29,P=0.715).CONCLUSION In this population-based study using the NCDB,immunotherapy treatment was associated with significantly improved OS compared to chemotherapy in patients with MSI-H metastatic colorectal cancer,but not in those with MSI-L/MSS metastatic colorectal cancer.Further studies are warranted to determine the optimal therapeutic approach for patients with MSI-L/MSS metastatic colorectal cancer.

Discrepancy among microsatellite instability detection methodologies in non-colorectal cancer:Report of 3 cases

BACKGROUND Microsatellite instability(MSI)is a predictive biomarker for cancer immunotherapy.The tumor-agnostic nature of MSI makes it a denominator for immunotherapy in several solid tumors.It can be assessed using next-generation sequencing(NGS),fluorescent multiplex PCR,and immunohistochemistry(IHC).CASE SUMMARY Here,we report 3 cases with discordant MSI results detected using different methods.A cholangiocellular carcinoma case revealed proficient mismatch repair(MMR)by IHC but high MSI(MSI-H)by liquid NGS.A cervical cancer case revealed deficient MMR by IHC,microsatellite stable by PCR,and MSI-H by NGS.Lastly,an endometrial cancer case revealed proficient MMR by IHC but MSI-H by NGS.CONCLUSION IHC for MMR status is the first choice due to several advantages.However,in cases of indeterminate IHC results,molecular testing by MSI-PCR is preferred.Recently,NGS-based MSI assays are being widely used to detect MSI-H tumors.All three methods have high accuracy;however,the inconsistencies between them may lead to misdiagnosis.

Bat 26 Microsatellite Instability in Oral Cavity Cancers in Senegal

Oral cavity cancers are part of head and neck cancers. They have become frequent in the world in general and Senegal in particular. This study evaluates microsatellite instability tumors in oral cavity cancers in Senegal. Forty cancerous tissues, 20 healthy tissues, and 12 blood tissues were included in this study. These tissues were collected from each patient during the biopsy after obtaining consent. DNA extraction, Polymerase Chain Reaction (PCR) and sequencing were carried out to obtain sequences. Mutation surveyor, Bioedit and Dnasp software were used to perform our analyses. High instability was found in 57.5% of patients with cancer. Moreover, 90% of the patients had the same motif on healthy and cancerous tissue. Furthermore, 26.12%, 20.72%, and 11.71% polymorphic sites were found in cancerous, healthy and blood tissue respectively. Thus, a similarity between cancerous and healthy tissues seems to exist. This implies that instability of the Bat 26 microsatellite could occur early in the occurrence of oral cavity cancers.

Study on the Correlation between the Expression of Angiogenic Factor VEGF and Microsatellite Instability in Gastric Adenocarcinoma

Objective: To investigate the correlation between the microsatellite instability (MSI) and the expression of vascular endothelial growth factor (VEGF) in gastric adenocarcinoma. Methods: PCR SSCP method was used to detect MSI of thirty cases with gastric adenocarcinoma at five loci in each patient. Expression of VEGF was examined by the method of immunohistochemistry. Results: The positive of MSI was in 13 patients out of 30 patients (43.4%) in our study. Positive VEGF Immunostaining was detected in 18 patients (60.0%). VEGF was decreased in microsatellite instability high (MSI H) gastric adenocarcinoma. Conclusion: MSI H and microsatellite stable (MSS) gastric adenocarcinoma may follow a different pathway of angiogenesis. The low frequency of VEGF expression among MSI H cancer may partially explain why these cancers are less aggressive.

Interrelationship between microsatellite instability and microRNA in gastrointestinal cancer

There is an increasing understanding of the roles that microsatellite instability （MSI） plays in Lynch syndrome （by mutations） and sporadic （by mainly epigenetic changes） gastrointestinal （GI） and other cancers. Defi- cient DNA mismatch repair （MMR） results in the strong mutator phenotype known as MSI, which is the hall- mark of cancers arising within Lynch syndrome. MSI is characterized by length alterations within simple repeated sequences called microsatellites. Lynch syn- drome occurs primarily because of germline mutations in one of the MMR genes, mainly MLH1 or MSH2, less frequently MSH6, and rarely PMS2. MSI is also observed in about 15% of sporadic colorectal, gastric, and en-dometrial cancers and in lower frequencies in a minor- ity of other cancers where it is often associated with the hypermethylation of the IVlLH1 gene. miRNAs are small noncoding RNAs that regulate gene expression at the posttranscriptional level and are critical in many biological processes and cellular pathways. There is accumulating evidence to support the notion that the interrelationship between MSI and miRNA plays a key role in the pathogenesis of GI cancer. As a possible new mechanism underlying MSI, overexpression of m/R-IEE has been shown to downregulate expression of MLH1, IVlSH2, and MSH6. Thus, a subset of MSI-positive （MSI＋） cancers without known MMR defects may result from m/R-1E5 overexpression. Target genes of frameshift mutation for MSI are involved in various cellular func- tions, such as DNA repair, cell signaling, and apoptosis. A novel class of target genes that included not only epi- genetic modifier genes, such as HDAC2, but also miRNA processing machinery genes, including TARBP2 and XPO5, were found to be mutated in MSI＋ GI cancers. Thus, a subset of MSI＋ colorectal cancers （CRCs） has been proposed to exhibit a mutated miRNA machinery phenotype. Genetic, epigenetic, and transcriptomic dif- ferences exist between MSI＋ and MSI- cancers. Mo- lecular signatures of miRNA expression apparently have the potential to distinguish between MSI＋ and MSI- CRCs. In this review, we summarize recent advances in the MSI pathogenesis of GI cancer, with the focus on its relationship with miRNA as well as on the potential to use MSI and related alterations as biomarkers and novel therapeutic targets.

Causes and consequences of microsatellite instability in gastric carcinogenesis

Loss of DNA mismatch repair(MMR) function, due to somatic or germline epi/genetic alterations of MMR genes leads to the accumulation of numerous mutations across the genome, creating a molecular phenotype known as microsatellite instability(MSI). In gastric cancer(g C), MSI occurs in about 15% to 30% of the cases. This review summarizes the current knowledge on the molecular mechanisms underlying the acquisition of MSI in g C as well as on the clinic, pathologic and molecular consequences of the MSI phenotype. Additionally, current therapeutic strategies for g C and their applicability in the MSI subset are also discussed.

Genetic changes of p53,K-ras,and microsatellite instability in gallbladder carcinoma in high-incidence areas of Japan and Hungary

AIM： To disclose geographic differences in genetic changes involved in gallbladder carcinogenesis between two distinct high-incidence areas of Japan and Hungary. METHODS： We examined 42 cases of gallbladder carcinoma： 22 Japanese and 20 Hungarian cases, p53 mutations at exons 5 to 8 and K-ras mutations at codon 12 were tested by direct sequencing. Microsatellite instability was determined from fluorescent dye-labeled PCR amplifications of flve-microsatellite markers （BAT-25, BAT-26, D2S123, DSS346, and D17S250）. RESULTS： Mutations of p53 were detected in 11 of 22 Japanese cases and 6 of 18 Hungarian cases （11/22 vs 6/18, P = 0.348）. Transition at CpG sites was found in none of 11 Japanese cases and 2 of 6 Hungarian cases; the difference was marginally significant （0/11 vs 2/6,P = 0.110）. K-ras mutations were detected in only one of the Hungarian cases. Eight of 19 （42.1%） ]apanese cases were MSI-high （presence of novel peaks in more than one of the five loci analyzed）, whereas only 1 of 15 （6.7%） Hungarian cases was MSI-high （P = 0.047）. CONCLUSION： It appears that the p53 mutations and MSI differ in patients with gallbladder carcinoma between two distinct high-incidence areas. Geographic variation might exist in the process of gallbladder carcinogenesis.

Microsatellite instability and MLH1 promoter hypermethylation in colorectal cancer

Colorectal cancer （CRC） is caused by a series of genetic or epigenetic changes, and in the last decade there has been an increased awareness that there are multiple forms of colorectal cancer that develop through different pathways. Microsatellite instability is involved in the genesis of about 15% of sporadic colorectal cancers and most of hereditary nonpolyposis cancers. Tumors with a high frequency of microsatellite instability tend to be diploid, to possess a mucinous histology, and to have a surrounding lymphoid reaction. They are more prevalent in the proximal colon and have a fast pass from polyp to cancer. Nevertheless, they are associated with longer survival than stage-matched tumors with microsateUite stability. Resistance of colorectal cancers with a high frequency of microsatellite instability to 5-fluorouracilbased chemotherapy is well established. Silencing the MLH1 gene expression by its promoter methylation stops the formation of MLH1 protein, and prevents the normal activation of the DNA repair gene. This is an important cause for genomic instability and cell proliferation to the point of colorectal cancer formation. Better knowledge of this process will have a huge impact on colorectal cancer management, prevention, treatment and prognosis.

Microsatellite instability in gastric cancer and pre-cancerous lesions

AIM: To investigate the microsatellite instability (MSI) in cancer and pre-cancerous lesions of the stomach and its mechanisms underlying the development of gastric cancer.METHODS: Thirty-six gastric cancer samples were obtained from patients undergoing surgery. Forty-one gastric mucosa samples with dysplasia and 51 with intestinal metaplasia (IM) were obtained from patients with chronic gastritis undergoing gastro-endoscopy. Genomic DNA was extracted from the samples. Silver staining single strand conformation polymorphis-polymerize chain reaction (SSCP-PCR) was used to screen MSI markers at 5 loci (Bat-25, Bat-26, D5S346, D17S250, and D2S123)in fresh tissues and formalin-fixed, paraffin-embedded samples and their corresponding normal gastric mucosa.RESULTS: The abnormal shifting of the single-strand DNA (MSI) was identified in 21 out of 36 (58.3%) gastric cancers.Seven cases showed high-level MSI (two or more loci altered) and 14 showed low-level MSI (one locus altered).Gastric cancer with MSI had a tendency to be located in the distal stomach. MSI was also detected in 11 out of 41(26.8%) dysplasia samples and in 9 of 51 (17.6%) IM samples respectively. Three cases of dysplasia and one case of IM showed high-level MSI. Eight cases of dysplasia and 8 cases of IM displayed low-level MSI. MIS in IM was found only in moderate or severe-grade IM. No association was detected between MSI and dysplasia grade.CONCLUSION: Accumulation of MSI in dysplasia and intestinal metaplasia of gastric mucosa may be an early molecular event during gastric carcinogenesis and may contribute to the acquisition of transformed cell phenotype and the development of gastric cancer.

Telomerase activity in colorectal cancer,prognostic factor and implications in the microsatellite instability pathway

AIM： To determine whether the telomerase activity is related to the Microsatellite instability （MSI） genetic pathway and whether it means a difference in the survival.METHODS： The population consisted of 97 colorectal cancer patients. MSI determination was performed in accordance with the NCI criteria using PCR and Genescan. Telomerase activity was determined by the TRAP-assay, an ELISA procedure based on the amplification of telomeric repeat sequences.RESULTS： 6.2% showed high MSI （MSI-H）, 10.3% showed low MSI （MSI-L） and 83.5% did not show this alteration （MSS）. Positive telomerase activity was detected in 92.8% of the patients. 83.3% of MSI-H tumors showed positive telomerase against 93.8% of MSS tumors. In the overall survival analysis the absence of telomerase activity conferred a better prognosis.CONCLUSION： Previous works have shown that tumors which develop via the MSI pathway present a better prognosis. No link between telomerase activity and MSl status is observed, although sample sizes are small. Patients with telomerase negative tumors had better overall survival than patients with telomerase positive tumors.

Helicobacter pylori and EBV in gastric carcinomas:Methylation status and microsatellite instability

AIM:To verify the methylation status of CDH1, DAPK, COX2, hMLH1 and CDKN2A genes and to evaluate their association with Helicobacter pylori (H. pylori)-cagA+ and Epstein Barr virus (EBV) infections in gastric adenocarcinomas.METHODS: Methylation-specific PCR (MSP) assay was performed in 89 primary gastric carcinomas (intestinal and diffuse types). Microsatellite instability (MSI) analysis was performed using the BAT26 primer set and PCR products were analyzed with the ABI PRISM 3100 Genetic Analyzer using Genescan 3.7 software (Applied Biosystems). Detection of H. pylori and genotyping were performed by PCR, using specifi c primers for ureaseC and cagA genes. The presence of EBV was assessed by in situ hybridization. Statistical analyses were performed using the χ2 or Fisher's exact test.RESULTS: The most frequent hypermethylated gene was COX-2 (63.5%) followed by DAPK (55.7%), CDH1 (51%), CDKN2A (36%) and hMLH1 (30.3%). Intestinal and diffuse adenocarcinomas showed different methylation profiles and there was an association between methylation of E-CDH1 and H. pylori-cagA+ in the intestinal adenocarcinoma type. MSI was correlated with hMLH1 methylation. There was an inverse correlation between DAPK hypermethylation and MSI.CONCLUSION: We found a strong association between CDH1 methylation and H. pylori-cagA+ in intestinal-type gastric cancer, association of MSI and better prognosis and an heterogeneous COX-2 overexpression.

Endoscopic and clinicopathologic characteristics of early gastric cancer with high microsatellite instability

AIM： To investigate endoscopic and clinicopathologic characteristics of early gastric cancer （EGC） according to microsatellite instability phenotype. METHODS： Data were retrospectively collected from a single tertiary referral center. Of 981 EGC patients surgically treated between December 2003 and October 2007, 73 consecutive EGC patients with two or more microsatellite instability （MSI） mutation [high MSI （MSI-H）] and 146 consecutive EGC patients with one or no MSI mutation （non-MSI-H） were selected. The endoscopic and clinicopathologic features were compared between the MSI-H and non-MSI-H EGC groups.RESULTS： In terms of endoscopic characteristics, MSI-H EGCs more frequently presented with elevated pattern （OR 4.38, 95% Cl： 2.40-8.01, P 〈 0.001）, moderate- to-severe atrophy in the surrounding mucosa （OR 1.91, 95% CI： 1.05-3.47, P = 0.033）, antral location （OR 3.99, 95% CI： 2.12-7.52, P 〈 0.001） and synchronous le- sions, compared to non-MSI-H EGCs （OR 2.65, 95% CI： 1.16-6.07, P = 0.021）. Other significant clinicopatholog- ic characteristics of MSI-H EGC included predominance of female sex （OR 2.77, 95% CI： 1.53-4.99, P 〈 0.001）, older age （〉 70 years） （OR 3.30, 95% CI： 1.57-6.92, P = 0.002）, better histologic differentiation （OR 2.35, 95% Cl： 1.27-4.34, P = 0.007）, intestinal type by Lau- ren classification （OR 2.34, 95% CI： 1.15-4.76, P = 0.019）, absence of a signet ring cell component （OR 2.44, 95% CI： 1.02-5.86, P = 0.046）, presence of mu- cinous component （OR 5.06, 95% Cl： 1.27-20.17, P = 0.022）, moderate-to-severe lymphoid stromal reaction （OR 3.95, 95% CI： 1.59-9.80, P = 0.003）, and co-exist- ing underlying adenoma （OR 2.66, 95% CI： 1.43-4.95, P = 0.002）. CONCLUSION： MSI-H EGC is associated with unique endoscopic and clinicopathologic characteristics includ- ing frequent presentation in protruded type, co-exist- ing underlying adenoma, and synchronous lesions.

Role of detection of microsatellite instability in Chinese with hereditary nonpolyposis colorectal cancer or ordinary hereditary colorectal cancer

AIM： To detect microsatellite instability （MSI） in patients with hereditary nonpolyposis colorectal cancer or ordinary hereditary colorectal cancer and to provide criteria for screening the kindreds with hereditary nonpolyposis colorectal cancer at molecular level.METHODS： MSI was detected in the specimens from 20 cases with HNPCC, 20 cases with ordinary hereditary colorectal cancer and 20 cases with sporadic colorectal cancer by means of polymerase chain reaction-single strand conformation polymorphism. RESULTS： The positive rate of MSI was 85% （17/20） in HNPCC group, 40% （8/20） in ordinary hereditary colorectal cancer group and 10% （2/20） in the sporadic colorectal cancer group respectively. The differences were significant. The mean ages of the three groups were 43.6, 52.2, and 61.8 years respectively, which increased gradually. The incidence of right hemicolon cancer was 64.7%, 37.5%, and 0% respectively, which decreased gradually and had significant difference. The expression ratio of BAT26 and BAT25 was 94.1% respectively, which was highest in the 5 gene sites studied. The incidence of poorly differentiated adenocarcinoma was 70.6% in HNPCC group among high frequency microsatellite instability （MSI-H）, which was higher than the other two groups, which had 50% and 50% respectively. CONCLUSION： The incidence of MSI-H is higher in HNPCC group. The detection of MSI is simple and economical and has high correlation with the clinicopathologic feature of HNPCC and can be used as a screening method to detect the germ line mutation of the mismatch repair gene.

Simplified microsatellite instability detection protocol provides equivalent sensitivity to robust detection strategies in Lynch syndrome patients

Objective:Germline mutations in mismatch repair(MMR)genes cause Lynch syndrome(LS).LS is an inherited disease,and an important consequence of MMR deficiency is microsatellite instability(MSI)phenotype.MSI phenotype influences the efficacy of5 fluorouracil(5-FU)chemotherapy.Reproducible,cost effective,and easy to perform laboratory tests are required to include MSI detection in routine laboratory practice.Evaluation of CAT25 as monomorphic short tandem repeat sequence enables CAT25 to be an efficient screening tool among hereditary nonpolyposis colorectal cancer(HNPCC)patients compared with other methods used currently.Methods:Based on Amsterdam II criteria,31 patients in 31 families were shortlisted from a total number of 1,659 colorectal cancer patients.MSI status was examined in these patients using CAT25 and a commercially available Promega MSI five-markerbased detection system as well as immunohistochemical(IHC)staining of four important MMR proteins.Patients were scored as high microsatellite instable(MSI-H),low(MSI-L),or stable(MSS).MSI status determined by CAT25 single mononucleotide marker was compared with that of five mononucleotide markers,Promega commercial kit,and IHC method.Results:MMR protein deficiency was observed on 7/31 probands using IHC methodology and 6/31 categorized as MSI-H using commercial kit or CAT25 single marker.The sensitivity and specificity of the CAT25 single marker were the same as those detected by five-marker Promega commercial kit in our patients.Conclusions:Based on our results,the performance of the CAT25 single mononucleotide marker for MSI status determination in our HNPCC patients is the same as that of the five-marker-based commercial kit.

Checkpoint with forkhead-associated and ring finger promoter hypermethylation correlates with microsatellite instability in gastric cancer

AIM:To examine the methylation status of the promoter region of the checkpoint with forkhead-associated and ring fi nger(CHFR) and microsatellite mutator status in 59 primary gastric cancers.METHODS:We investigated the promoter methylation of CHFR in 59 cases of gastric cancer using methylation-specifi c PCR.Five microsatellite loci were analyzed using high-intensity microsatellite analysis reported previously, and p53 gene mutations were investigated by direct sequencing.RESULTS:Twenty cases(33.9%) showed promoter methylation and no relation was observed with the clinicopathological factors.We found that the promoter methylation of CHFR was frequently accompanied with microsatellite instability(MIN).Seven of 20(35.0%) cases showed MIN in hypermethylation of the CHFR tumor, while three of 39(7.7%) cases showed MIN in the non-methylated CHFR tumor(P < 0.01).However, we failed to fi nd any relationship between CHFR methylation and p53 mutation status.CONCLUSION:The coordinated loss of both the mitotic check point function and mismatch repair system suggests the potential to overcome the cell cycle check point, which may lead to an accumulation of mutations.However, the p53 mutation was not related to hypermethylation of the CHFR promoter and MIN, which indicates that an abnormality in p53 occurs as an independent process from the mismatch repair deficiency in carcinogenesis.

Expression of Cyclooxygenase-2 and Its Relationship with Mismatch Repair and Microsatellite Instability in Hereditary Nonpolyposis Colorectal Cancer

Objective To investigate cyclooxygenase-2 (COX-2) expression and its relationship with mismatch repair (MMR) protein expression and microsatellite instability (MSI) in hereditary nonpolyposis colorectal cancer (HNPCC). Methods A total of 28 cases of colorectal adenoma and 14 cases of colorectal carcinoma were collected between July 2003 and July 2007 from 33 HNPCC families. Sporadic colorectal adenoma (n=32) and carcinoma patients (n=24) served as controls. With samples of tumor tissues and normal colonic mucosa collected from the patients, the protein expressions of COX-2 and MMR (hMLH1, hMSH2, and hMSH6) were examined with immunohistochemical assay. Frequency of MSI in five standard MSI loci BAT25, BAT26, D2S123, D5S346, and D17S250 were analyzed by means of polymerase chain reaction. Results The rate of COX-2 high-expression was 53.6% (15/28) and 42.9% (6/14) in HNPCC adenoma and carcinoma; 62.5% (20/32) and 91.7% (22/24) in sporadic adenoma and carcinoma, respectively. That rate was lower in HNPCC carcinoma than in sporadic carcinoma (P<0.05). MMR-deletion rate and percentage of high-frequency MSI (MSI-H) in HNPCC carcinoma were higher than those in sporadic colorectal carcinoma [both 71.4% (10/14) vs. 12.5% (3/24), both P<0.01]. Among the 10 MMR-deficient HNPCC carcinoma patients, COX-2 low-expression was observed in 8 cases (80.0%), while COX-2 high-expression was observed in all of the 4 MMR-positive HNPCC carcinoma cases (P<0.05). In comparison to MMR positive HNPCC carcinoma, HNPCC adenoma, and sporadic carcinoma, COX-2 expression was significantly lower in corresponding MMR-deficient cases (all P<0.05). The rates of COX-2 low-expression in HNPCC adenoma, HNPCC carcinoma, and sporadic carcinoma with MSI-H were significantly higher than those in the cases with microsatellite stability (all P<0.05). Conclusion COX-2 is expressed at a low level in HNPCC carcinoma, different from the high COX-2 expression in sporadic carcinoma.

Cytotoxic CD8+ T cells and tissue resident memory cells in colorectal cancer based on microsatellite instability and BRAF status

BACKGROUND Recent studies in non-colorectal malignancy have associated T resident memory(T_(RM)) cells with improved patient survival. It is unknown if T_(RM) plays a role in colorectal cancer(CRC).AIM To examine the potential role of T_(RM) cells in providing immunogenicity in CRC stratified by microsatellite instability(MSI) and BRAF status.METHODS Patients with known MSI and BRAF mutation status were eligible for inclusion in this study. CRC tumour sections stained with haematoxylin and eosin were microscopically reviewed and the images scanned prior to assessment for location of invading edge and core of tumour. Sequential sections were prepared for quantitative multiplex immunohistochemistry(IHC) staining. Opal Multiplex IHC staining was performed with appropriate positive and negative controls and imaged using a standard fluorescent microscope fitted with a spectral scanning camera(Mantra) in conjunction with Mantra snap software. Images were unmixed and annotated in in Form 2.2.0. Statistical analysis was performed using Graphpad Prism Version 7 and Stata Version 15.RESULTS Seventy-two patients with known MSI and BRAF status were included in the study. All patients were assessed for MSI by IHC and high resolution capillary electrophoresis testing and 44 of these patients successfully underwent quantitative multiplex IHC staining. Overall, there was a statistically significant increase in CD8+ T_(RM) cells in the MSI(BRAF mutant and wild type) group over the microsatellite stable(MSS) group. There was a statistically significant difference in CD8+ T_(RM) between high level MSI(MSI-H):BRAF mutant [22.57, 95% confidence interval(CI): 14.31-30.84] vs MSS [8.031(95%CI: 4.698-11.36)], P = 0.0076 and MSI-H:BRAF wild type [16.18(95%CI: 10.44-21.93)] vs MSS [8.031(95%CI: 4.698-11.36)], P = 0.0279. There was no statistically significant difference in CD8 T cells(both CD8+CD103-and CD8+CD103+T_(RM)) between MSI-H: BRAF mutant and wild type CRC.CONCLUSION This study has shown that CD8+ T_(RM) are found in greater abundance in MSI-H CRC, both BRAF mutant and MSI-H:BRAF wild type, when compared with their MSS counterpart. CD8+ T_(RM) may play a role in the immunogenicity in MSI-H CRC(BRAF mutant and BRAF wild type). Further studies should focus on the potential immunogenic qualities of T_(RM) cells and investigate potential immunotherapeutic approaches to improve treatment and survival associated with CRC.

Novel mutations and sequence variants in exons 3-9 of human T Cell Factor-4 gene in sporadic rectal cancer patients stratified by microsatellite instability

AIM： To establish the role of human T Cell Factor-4 （hTCF-4） gene exons 3-9 mutation status in association with sporadic rectal cancer with microsatellite instability （MSI）. METHODS： Microsatellite markers were genotyped in 93 sporadic rectal cancer patients. Eleven cases were found to be high-frequency MSI （MSI-H）. Sequence analysis of the coding region of the exons 3-9 of hTCF-4 gene was carried out for the 11 MSI-H cases and 10 controls （5 microsatellite stability （MSS） cases and 5 cases with normal mucosa）. The sequencing and MSI identification were used. RESULTS： Several novel mutations and variants were revealed. In exon 4, one is a 4-position continuous alteration which caused amino acid change from Q131T and S132I （391insA, 392 G 〉 A, 393 A 〉 G and 395delC） and another nucleotide deletion （395delC） is present in MSI-H cases （5/10 and 4/10, respectively） but completely absent in the controls.CONCLUSION： Novel mutations in exon 4 of hTCF-4 gene were revealed in this study, which might be of importance in the pathogenesis of sporadic rectal cancer patients with MSI-H.