Low-frequency Microsatellite Instability Research Articles

A radiomics model fusing clinical features to predict microsatellite status preoperatively in colorectal cancer liver metastasis

PurposeTo study the combined model of radiomic features and clinical features based on enhanced CT images for noninvasive evaluation of microsatellite instability (MSI) status in colorectal liver metastasis (CRLM) before surgery.MethodsThe study included 104 patients retrospectively and collected CT images of patients. We adjusted the region of interest to increase the number of MSI-H images. Radiomic features were extracted from these CT images. The logistic models of simple clinical features, simple radiomic features, and radiomic features with clinical features were constructed from the original image data and the expanded data, respectively. The six models were evaluated in the validation set. A nomogram was made to conveniently show the probability of the patient having a high MSI (MSI-H).ResultsThe model including radiomic features and clinical features in the expanded data worked best in the validation group.ConclusionA logistic regression prediction model based on enhanced CT images combining clinical features and radiomic features after increasing the number of MSI-H images can effectively identify patients with CRLM with MSI-H and low-frequency microsatellite instability (MSI-L), and provide effective guidance for clinical immunotherapy of CRLM patients with unknown MSI status.

The epigenetic modifier lysine methyltransferase 2C is frequently mutated in gastric remnant carcinoma.

Gastric remnant carcinoma (GRC), which occurs in the stomach after partial gastrectomy, is a rare and aggressive form of gastric adenocarcinoma (GAC). Comprehensive profiling of genomic mutations in GRC could provide the basis for elucidating the origin and characteristics of this cancer. Herein, whole-exome sequencing (WES) was performed on 36 matched tumor-normal samples from patients with GRC and identified recurrent mutations in epigenetic modifiers, notably KMT2C, ARID1A, NSD1, and KMT2D, in 61.11% of cases. Mutational signature analysis revealed a low frequency of microsatellite instability (MSI) in GRC, which was further identified by MSIsensor, MSI-polymerase chain reaction, and immunohistochemistry analysis. Comparative analysis demonstrated that GRC had a distinct mutation spectrum compared to that of GAC in The Cancer Genome Atlas samples, with a significantly higher mutation rate of KMT2C. Targeted deep sequencing (Target-seq) of an additional 25 paired tumor-normal samples verified the high mutation frequency (48%) of KMT2C in GRC. KMT2C mutations correlated with poor overall survival in both WES and Target-seq cohorts and were independent prognosticators in GRC. In addition, KMT2C mutations were positively correlated with favorable outcomes in immune checkpoint inhibitor-treated pan-cancer patients and associated with higher intratumoral CD3+ , CD8+ tumor-infiltrating lymphocyte counts, and PD-L1expression in GRC samples (p = 0.018, 0.092, 0.047, 0.010, and 0.034, respectively). Our dataset provides a platform for information and knowledge mining of the genomic characteristics of GRC and helps to frame new therapeutic approaches for this disease.

Interaction between glycolysis‒cholesterol synthesis axis and tumor microenvironment reveal that gamma-glutamyl hydrolase suppresses glycolysis in colon cancer.

Metabolic reprogramming is a feature of cancer. However, colon cancer subtypes based on the glycolysis‒cholesterol synthesis axis have not been identified, and little is known about connections between metabolic features and the tumor microenvironment. Data for 430 colon cancer cases were extracted from The Cancer Genome Atlas, including transcriptome data, clinical information, and survival outcomes. Glycolysis and cholesterol synthesis-related gene sets were obtained from the Molecular Signatures Database for a gene set variation analysis. The relationship between the genomic landscape and immune landscape were investigated among four metabolic subtypes. Hub genes were determined. The clinical significance of candidate hub gene was evaluated in 264 clinical samples and potential functions were validated in vitro and in vivo. Colon cancer cases were clustered into four metabolic subtypes: quiescent, glycolytic, cholesterogenic, and mixed. The metabolic subtypes differed with respect to the immune score, stromal score, and estimate score using the ESTIMATE algorithm, cancer-immunity cycle, immunomodulator signatures, and signatures of immunotherapy responses. Patients in the cholesterogenic group had better survival outcomes than those for other subtypes, especially glycolytic. The glycolytic subtype was related to unfavorable clinical characteristics, including high mutation rates in TTN, APC, and TP53, high mutation burden, vascular invasion, right colon cancer, and low-frequency microsatellite instability. GGH, CACNG4, MME, SLC30A2, CKMT2, SYN3, and SLC22A31 were identified as differentially expressed both in glycolytic-cholesterogenic subgroups as well as between colon cancers and healthy samples, and were involved in glycolysis‒cholesterol synthesis. GGH was upregulated in colon cancer; its high expression was correlated with CD4+ T cell infiltration and longer overall survival and it was identified as a favorable independent prognostic factor. The overexpression of GGH in colon cancer-derived cell lines (SW48 and SW480) inhibited PKM, GLUT1, and LDHA expression and decreased the extracellular lactate content and intracellular ATP level. The opposite effects were obtained by GGH silencing. The phenotype associated with GGH was also validated in a xenograft nude mouse model. Our results provide insight into the connection between metabolism and the tumor microenvironment in colon cancer and provides preliminary evidence for the role of GGH, providing a basis for subsequent studies.

Prognostic value of desmoplastic stromal reaction, tumor budding and tumor-stroma ratio in stage II colorectal cancer

Existing high-risk factors are insufficient to accurately predict the postoperative recurrence risk of stage II colorectal cancer (CRC). The discovery of additional prognostic markers may be the key to improving the current status of stage II CRC treatment. The present study aimed to evaluate the relationship among desmoplastic reaction (DR), tumor budding (TBd), the tumor-stroma ratio (TSR) and their prognostic value for relapse-free survival (RFS). In this study, 207 patients with histologically confirmed stage II CRC from January 2012 to August 2018 were retrospectively reviewed from a single center; the cohort was divided into subgroups based on low or high TSR, and low, intermediate or high DR and TBd. Kaplan-Meier curve analysis and log-rank test were applied to examine RFS among subgroups. Univariate and multivariate Cox proportional hazards analyses were used to identify independent factors associated with RFS, and a nomogram was subsequently developed. Abnormal CA242, CEA, T4 stage, presence of hypertension, internal obstruction or perforation (IOP), lymphovascular or/and perineural invasion (PNI), number of nodes examined less than 12, low-frequency microsatellite instability (MSI-L), higher Ki-67 and immature DR were associated with a lower RFS. In multivariable analysis, DR (HR =2.111; 95% CI: 1.184-3.766; P=0.011), LVI (HR =1.919; 95% CI: 1.004-3.669; P=0.049) and PNI (HR =2.724; 95% CI: 1.362-5.448; P=0.005) were prognostic factors for RFS. On this basis, a nomogram that integrated DR and clinicopathologic predictors for predicting RFS passed the calibration and had an area under the curve of 0.826. The prognostic significance of DR outperformed TBd and TSR, therefore, we recommend adding DR as a biomarker in routine pathological reports. The novel nomogram combining these factors may be used as a reliable and effective tool for the prediction of RFS in stage II CRC, thus helping optimize therapeutic regimens under cooperation of oncologists and surgeons. Further multicentric studies are required for validation of this novel, simple and cost-effective prognostic model.

Left-sided colorectal cancer distinct in indigenous African patients compared to other ethnic groups in South Africa

IntroductionA large proportion of indigenous African (IA) colorectal cancer (CRC) patients in South Africa are young (< 50 years), with no unique histopathological or molecular characteristics. Anatomical site as well as microsatellite instability (MSI) status have shown to be associated with different clinicopathological and molecular features. This study aimed to ascertain key histopathological features in microsatellite stable (MSS) and low-frequency MSI (MSI-L) patients, to provide insight into the mechanism of the disease.MethodsA retrospective cohort (2011–2015) of MSS/MSI-L CRC patient samples diagnosed at Charlotte Maxeke Johannesburg Academic Hospital was analyzed. Samples were categorized by site [right colon cancer (RCC) versus left (LCC)], ethnicity [IA versus other ethnic groups (OEG)] and MSI status (MSI-L vs MSS). T-test, Fischer’s exact and Chi-square tests were conducted.ResultsIA patients with LCC demonstrated an increased prevalence in males, sigmoid colon, signet-ring-cell morphology, MSI-L with BAT25/26 marker instability and advanced disease association.ConclusionThis study revealed distinct histopathological features for LCC, and suggests BAT25 and BAT26 as negative prognostic markers in African CRC patients. Larger confirmatory studies are recommended.

Quantitative evaluation of MSI testing using NGS detects the imperceptible microsatellite changed caused by MSH6 deficiency.

Microsatellite instability (MSI) is an effective biomarker for diagnosing Lynch syndrome (LS) and predicting the responsiveness of cancer therapy. MSI testing is conventionally performed by capillary electrophoresis, and MSI status is judged by visual assessment of allele size change. Here, we attempted to develop a quantitative evaluation model of MSI using next-generation sequencing (NGS). Microsatellite markers were analyzed in tumor and non-tumor tissues of colorectal cancer patients by NGS after a single multiplex polymerase chain reaction amplification. The read counts corresponding to microsatellite loci lengths were calculated independently of mapping against a reference genome, and their distribution was digitized by weighted mean. Weighted mean differences between tumor and non-tumor samples with different MSI status were assessed, and cut-off values for each marker in the discovery cohort were determined. Each microsatellite maker was defined as unstable if the weighted mean difference was greater than the cut-off value. In the discovery cohort, the evaluation model demonstrated sensitivity and specificity of 100% for all markers. In the validation cohort, MSI status determined by the new model was consistent with the outcome of the conventional method in 29/30 cases (97%). The single inconsistent case was classified as low-frequency MSI by the conventional method but considered MSI-high by NGS. Genetic testing for mismatch repair genes revealed a pathogenic variant in MSH6 in the discordant case. We successfully developed a quantitative evaluation method for determining MSI status using NGS. This is a robust and sensitive method and could improve LS diagnosis.

Microsatellite instability is inversely associated with type 2 diabetes mellitus in colorectal cancer.

BackgroundMicrosatellite instability (MSI) is a clonal change in the number of repeated DNA nucleotide units in microsatellites. High-frequency MSI (MSI-H) colorectal cancers (CRCs) are known to have different clinicopathological features compared with microsatellite stable (MSS) CRCs. In addition, previous studies have shown that type2 diabetes mellitus (T2DM) is a risk factor for malignant tumors including CRCs. The aim of this study was to investigate the relationship between T2DM and MSI-H colorectal cancer.MethodsThe study design is a single center, cross-sectional study. Data from a series of 936 patients with CRCs were collected and MSI status was assessed.ResultsIn total, 29 (3.1%) and 907 (96.9%) tumors were classified as having MSI-H and low-frequency microsatellite instability or being MSS (MSS), respectively. Of the 936 patients, 275 (29.6%) were associated with T2DM. One (3.4%) of the 29 MSI-H patients and 274 (30.2%) of the 907 MSS patients had T2DM. Thus, the incidence of T2DM was significantly less frequent in MSI-H compared with MSS patients (Fisher’s exact test: p = 0.0007).ConclusionsWe conclude that MSS tumors are significantly more common than MSI-H tumors among individuals with T2DM.

Predicting the Efficacy of 5-Fluorouracil-Based Adjuvant Chemotherapy in Gastric Cancer by Microsatellite Instability: A Meta-Analysis.

Microsatellite instability (MSI) implies the deletion of mismatch repair genes caused by DNA methylation or gene mutation. MSI is a good predictor for efficacy of 5-fluorouracil (FU)-based chemotherapy in the treatment of colorectal cancer. Some gastric cancer studies have reported that MSI has no apparent impact on prognosis after patients receive 5-FU-based adjuvant chemotherapy. However, other studies suggest that high-frequency MSI (MSI-H) status reduced survival in patients receiving 5-FU-based adjuvant chemotherapy. Thus, the correlation between MSI status and efficacy of 5-FU-based adjuvant chemotherapy for gastric cancer remains controversial. We performed a PubMed, Embase, and Cochrane search to retrieve studies that explore the correlation between MSI status and 5-FU-based adjuvant chemotherapy efficacy in gastric cancer. After extracting 65 potentially eligible studies, four were ultimately included in this meta-analysis using Stata software (ver. 12.0). For each study, we estimated the hazard ratio (HR) value for overall survival (OS), and HR was extracted per the survival curve in the studies. Heterogeneity was estimated using the random-effects model. Overall, 1174 patients after operation were included: 84 patients were classed as MSI-H and 1090 as microsatellite stable (MSS)/low-frequency MSI (MSI-L). For the four studies, the overall estimate of HR for OS between MSI-H and MSS/MSI-L groups was 1.90 (95% confidence interval: 0.91-3.93; p = 0.08). We found no correlation to exist between MSI status and efficacy of 5-FU-based adjuvant chemotherapy for gastric cancer. Although MSI can effectively predict efficacy of 5-FU-based chemotherapy in patients with colorectal cancer, the correlation between MSI status and efficacy of 5-FU-based adjuvant chemotherapy for gastric cancer remains controversial. This meta-analysis suggests that MSI status is unrelated to efficacy of 5-FU-based adjuvant chemotherapy in gastric cancer, and more prospective clinical studies are needed to further investigate predictive value of MSI status in patients with gastric cancer who, after operation, receive 5-FU-based adjuvant chemotherapy.

Toward a Molecular Classification of Synchronous Colorectal Cancer: Clinical and Molecular Characterization

BackgroundTwo or more primary colorectal tumors coexisting at the time of diagnosis are considered to be synchronous tumors. It is estimated that synchronous colorectal cancer (SCRC) only accounts for 1.1% to 8.1% of all colorectal cancers (CRCs), and its molecular basis is still poorly understood. Patients and MethodsWe evaluated the microsatellite instability (MSI) and the CpG island methylator phenotype (CIMP) statuses in a series of 49 patients (98 tumors) diagnosed with sporadic SCRC at the 12 de Octubre University Hospital with the aim of improving the molecular characterization of this type of tumor. We considered Lynch syndrome, familial adenomatous polyposis, and MUTYH-associated polyposis (MAP) as exclusion criteria. ResultsMolecular subgrouping on the basis of MSI and CIMP enabled us to define 4 groups that corresponded to the molecular classification proposed for single-tumor CRC. We observed a significant predominance of MSI tumors at the right side regardless of the methylation pattern, and a significant prevalence of microsatellite-stable tumors either at the left side or throughout the entire colon (P = .026). Furthermore, we defined some molecular features frequently observed in sporadic SCRC such as a low-frequency of MSI (8.2%). We observed a high concordance in terms of MSI between simultaneous tumors (93.9%) and a lower concordance in terms of CIMP (51%) between such tumors. ConclusionOur findings support the hypothesis that SCRC involves an environmental rather than a genetic component in which various etiologic factors might modify tumor progression. Further studies are required to refine the molecular characterization of SCRC.

Patterns of recurrence by microsatellite instability in colorectal cancer.

501 Background: Although colorectal cancer (CRC) with microsatellite instability (MSI) has a more favorable prognosis than microsatellite stable (MSS) CRC, patterns of recurrence has not been precisely investigated. We aim to explore patterns of recurrence and prognosis of CRC with MSI-H (high-frequency MSI) in comparison to MSI-L (low-frequency of MSI)/MSS. Methods: Patients with stage I-III colorectal cancer who received complete surgical resection were included using retrospective cohort of Yonsei Cancer Center. Patients were categorized to MSI status (MSI-H vs. MSS-L/MSS). Patterns of recurrence, disease free survival (DFS) and overall survival (time from diagnosis to death as OS1 and time from recurrence to death as OS2) between two groups were compared. Results: A total of 2944 patients were evaluated. Of all, 263 patients (8.9%) has MSI-H tumor. Patients with MSI-L/MSS tumor experienced more systemic recurrence events than patients with MSI-H tumor (13.1% vs. 4.6%). In patients who experienced recurrence, MSI-H tumor has tendency toward young age, proximal location and poorly differentiated histology. MSI-H tumor is more likely to recur as peritoneal metastasis (33.3% vs. 8.0%, p-value 0.002) and lymph node metastasis (25.0% vs. 7.7%, p-value 0.033). In contrast, MSI-L/MSS tumor is more likely to recur as lung metastasis (37.1% vs. 0.0%, p-value 0,008). There was no difference in DFS [hazard ratio (HR) = 0.753, p-value 0.241] and OS1 [HR = 1.486, p-value 0.203]. However, OS2 was marginally inferior in MSI-H tumor [HR = 1.779, p-value 0.064]. Conclusions: Patterns of recurrence in MSI-H CRC is different from that of MSI-L/MSS and modification of surveillance strategy in MSI-H CRC should be considered. In addition, prognosis of recurred MSI-H CRC is not superior than MSI-L/MSS and prognostic value of MSI in this circumstance should be evaluated using larger sample size.

Microsatellite instability & survival in patients with stage II/III colorectal carcinoma.

Background & objectives:The two key aspects associated with the microsatellite instability (MSI) as genetic phenomenon in colorectal cancer (CRC) are better survival prognosis, and the varying response to 5-fluorouracil (5-FU)-based chemotherapy. This study was undertaken to measure the survival of surgically treated patients with stages II and III CRC based on the MSI status, the postoperative 5-FU treatment as well as clinical and histological data.Methods:A total of 125 consecutive patients with stages II and III (American Joint Committee on Cancer, AJCC staging) primary CRCs, were followed prospectively for a median time of 31 months (January 2006 to December 2009). All patients were assessed, operated and clinically followed. Tumour samples were obtained for cytopathological verification and MSI grading.Results:Of the 125 patients, 21 (20%) had high MSI (MSI-H), and 101 patients (80%) had MSI-L or MSS (low frequency MSI or stable MSI). Patients with MSS CRC were more likely to have recurrent disease (P=0.03; OR=3.2; CI 95% 1-10.2) compared to those with MSI-H CRC. Multi- and univariate Cox regression analysis failed to show a difference between MSI-H and MSS groups with respect to disease-free, disease-specific and overall survival. However, the disease-free survival was significantly lower in patients with MSI-H CRC treated by adjuvant 5-FU therapy (P=0.03).Interpretation & conclusions:MSI-H CRCs had a lower recurrence rate, but the prognosis was worse following adjuvant 5-FU therapy.

Clinical Implications of Microsatellite Instability in T1 Colorectal Cancer

PurposeThe estimation of regional lymph node metastasis (LNM) risk in T1 colorectal cancer is based on histologic examination and imaging of the primary tumor. High-frequency microsatellite instability (MSI-H) is likely to decrease the possibility of metastasis to either regional lymph nodes or distant organs in colorectal cancers. This study evaluated the clinical implications of MSI in T1 colorectal cancer with emphasis on the usefulness of MSI as a predictive factor for regional LNM.Materials and MethodsA total of 133 patients who underwent radical resection for T1 colorectal cancer were included. Genomic DNA was extracted from normal and tumor tissues and amplified by polymerase chain reaction (PCR). Five microsatellite markers, BAT-25, BAT-26, D2S123, D5S346, and D17S250, were used. MSI and clinicopathological parameters were evaluated as potential predictors of LNM using univariate and multivariate analyses.ResultsAmong 133 T1 colorectal cancer patients, MSI-H, low-frequency microsatellite instability (MSI-L), and microsatellite stable (MSS) colorectal cancers accounted for 7.5%, 6%, and 86.5%, respectively. MSI-H tumors showed a female predominance, a proximal location and more retrieved lymph nodes. Twenty-two patients (16.5%) had regional LNM. Lymphovascular invasion and depth of invasion were significantly associated with LNM. There was no LNM in 10 MSI-H patients; however, MSI status was not significantly correlated with LNM. Disease-free survival did not differ between patients with MSI-H and those with MSI-L/MSS.ConclusionMSI status could serve as a negative predictive factor in estimating LNM in T1 colorectal cancer, given that LNM was not detected in MSI-H patients. However, validation of our result in a different cohort is necessary.

Low-frequency microsatellite instability in genomic di-nucleotide sequences correlates with lymphatic invasion and poor prognosis in gastric cancer.

The clinical significance of low-frequency microsatellite instability (MSI-L) in gastric cancer (GC) has not been well established. The aim of this study was to evaluate the clinicopathological features of MSI-L in GC. We investigated microsatellite instability (MSI) in 5 di-nucleotide repeat sequences in 210 unselected GC patients. High-resolution fluorescent microsatellite analysis assay was utilized to detect MSI. Clinicopathological variables were compared among groups with different microsatellite statuses. The overall survival (OS) was analyzed by Kaplan-Meier method. Multivariable analysis was performed to identify prognostic factors and variables correlated with lymph node metastasis. High-frequency microsatellite instability (MSI-H), MSI-L, and microsatellite stable were identified, respectively, in 10.5, 10.0, and 79.5% of unselected GC cases. Tumors with MSI-H were less invasive, and these patients showed a better OS. MSI-L was correlated with more advanced tumor Node Metastasis stage, and more frequent lymph node metastasis. The unfavorable prognosis predicted by MSI-L was ascribed to its correlation with lymphatic invasion. MSI-L characterized by di-nucleotide markers represents a distinct subcategory of GC with aggressive clinicopathological features, which are particularly affiliated to lymphatic system and correlated with a poor prognosis. MSI-L could be beneficial for predicting the clinical outcome of GC.

Colorectal cancer with high-frequency microsatellite instability expresses high-level thymidine phosphorylase but not dihydropyrimidine dehydrogenase

Recent clinical studies have reported that microsatellite instability (MSI) colorectal cancers show a high sensitivity to 5-FU, but these reports are contradictory to findings from in vitro analyses. In this study, we analyzed the relationship between MSI phenotypes and the expression of 5-FU metabolic enzymes in human colorectal cancer specimens. MSI phenotypes in 174 sporadic colorectal carcinomas were determined and grouped into the following three categories based on the Bethesda guidelines: high-frequency MSI (MSI-H), low-frequency MSI (MSI-L), and stable microsatellite (MSS). The expressions of dihydropyrimidine dehydrogenase (DPD) and thymidine phosphorylase (TP) in tumor specimens were measured by enzymelinked immunosorbent assays. The ratio of TP to DPD expression (TP/DPD ratio) was calculated for each tumor. These three factors were compared with regard to MSI phenotypes by non-parametric and logistic regression analyses using cut-off values at their medians. MSI-L tumors were excluded from statistical analyses. Thirteen tumors were classified as MSI-H, 8 tumors as MSI-L, and 153 tumors as MSS. DPD expression did not differ between MSI-H tumors and MSS tumors. TP expression and the TP/DPD ratio were significantly higher in MSI-H tumors than in MSS tumors [TP, 160.1± 104.0 vs 97.3 ± 53.7 (Units/mg protein) (P=0.009); TP/DPD ratio, 3.04 ± 1.62 vs 2.07 ± 1.08, (P=0.016)]. These differences were also significant in multivariate analysis. In conclusion, these data suggest that 5-FU catabolic activity in cancer tissue does not differ between MSI-H and MSS tumors. However, 5-FU anabolic activity in cancer tissue is higher in MSI-H than in MSS colorectal carcinomas.

Germline mutation analysis, microsatellite instability and clinical pathology in Hazakh in China hereditary nonpolyposis colorectal cancer pedigree

Objective To study the significance of mismatch repair (MMR) gene and microsatellite instability (MSI) in Hazakh in China hereditary nonpolyposis colorectal cancer (HNPCC) pedigree.Methods The tumor tissues and normal intestine mucosa of the 105 members of this family were immunohistochemically examined for hMLH1 and hMSH2.The mutation of BAT25,BAT26,D2S123,D5S346 and D17S250 were analyzed with polymerase chain reaction-single-stmded conformation polymorphism (PCR-SSCP) in tissue paraffin imbedding in all cases of the family.Results MSI-positive rate of 17tumor in HNPCC families group was 100 ％,in which there are 16 patients (94.1％) with high frequency microsatellite instability (MSI-H),1 patients with low frequency microsatellite instability (MSI-L)(5.9％).The negative expression of hMLH1 or hMSH2 rate of 17 tumor in HNPCC families group was 100％.There are 44 patients (50.0％) in the other 88 members of the HNPCC family with MSI-H.There are 40 patients with hMLH1 or hMSH2 MMR protein expression absence in the 44 patients with MSI-H.Conclusion HNPCC patients with MSI-H and hMLH1 or hMSH2 MMR protein expression absence have a better consistency with earlier age of onset,right colon cancer incidence and the occurrence of poorly differentiated carcinoma. Key words: Hereditary nonpolyposis colorectal cancer; Microsatellite instability; Mismatch repair gene; Hazakh

Prognostic value of microsatellite instability in sporadic locally advanced rectal cancer following neoadjuvant radiotherapy

This study was conducted to investigate the clinicopathological significance and prognostic value of microsatellite instability (MSI) in locally advanced rectal cancer (LARC) following neoadjuvant radiotherapy. A total of 316 consecutive patients with LARC who underwent neoadjuvant radiotherapy and curative surgery were included retrospectively. Microsatellite instability in pretreatment biopsy tissue was assessed using the pentaplex panel of mononucleotides. Twenty-five tumours (7.9%) were assessed as high-frequency MSI (MSI-H) and 291 were low-frequency MSI (MSI-L; n = 42) or microsatellite stable (MSS; n = 249). There were no significant differences in terms of gender, age, tumour location or pretreatment serum carcinoembryonic antigen between the MSI-H and MSI-L + MSS groups. Microsatellite instability was not associated statistically with pathological stage, radiation-induced tumour regression or downstaging. No significant difference was found in disease-free survival (DFS) between the two groups but, within the subgroup of ypN0 stage, patients with MSI-H tumours presented a significantly improved DFS compared with those with MSI-L or MSS tumours (100% versus 79.8%, P < 0.05), whereas no DFS improvement was observed for patients with MSI-H tumours in the ypN + subgroup. Microsatellite instability could not predict a histopathological response to neoadjuvant radiotherapy, but was a good prognostic marker for patients without lymph node metastasis after neoadjuvant radiotherapy.

Gastrointestinal cancers reactive for the PAb416 antibody against JCV/SV40 T-Ag lack JCV DNA sequences while showing a distinctive pathologic profile

AimImmunohistochemical and molecular studies have suggested an oncogenic role for JCV in gastrointestinal carcinomas, but at least in colorectal cancers, the data are far from being unambiguous.MethodsTwo large series of...

Assessment of the beneficial loci and prognostic implications of microsatellite instability in gastric carcinoma

Microsatellite instability (MSI) is a hyper-mutable phenotype caused by the loss of DNA mismatch repair activity, and plays a crucial role in gastric carcinogenesis. To clarify the role of genetic instability in relation to clinicopathological variables, and to identify predictive MSI markers that facilitate the early detection and improve the classification of gastric carcinomas (GCs), 13 microsatellite (MS) loci, including the National Cancer Institute (NCI) panel of MS markers (D2S123, D5S346, D17S250, BAT25 and BAT26) and 8 dinucleotide repeats (D3S1260, D5S107, D5S409, D17S261, D17S520, D17S855, D18S34 and D18S61) were studied in GC patients. MSI was found in 88.2% (30/34) of GC cases and the number of high-frequency MSI (MSI-H, 23.5%, 8/34), low-frequency MSI (64.7%, 22/34), and stable MSI (11.8%, 4/34), was calculated. Among the MS loci analyzed, D18S34 and D17S261 (15/34, 44.1%) exhibited the highest frequency of MSI, followed by D2S123 (14/34, 41.2%), D5S107, D5S346, D5S409 and D18S61 (12/34, 35.3%) (MSI>35%). MSI-H was particularly prevalent in older patients and was mainly found in the antrum and poorly differentiated tumors. Furthermore, MSI-H was significantly associated with lymph node involvement cases in females. One notable finding in this analysis was that the markers, D17S250 and D17S520, exhibited a significantly higher percentage of MSI in advanced gastric carcinomas than in early gastric carcinomas (P=0.046 and 0.046, respectively), and the D17S520 and BAT26 loci represented significant different correlations between the tumor stages (P=0.038 and 0.042, respectively). This study indicates that the novel markers, D18S34 and D17S261, perform more favorably than the NCI panel for the detection of MSI, and the D17S520 locus presents a potential target for predicting the clinical impact of GC. These novel MS loci may prove to be beneficial and independent tools for the construction of a comprehensive genetic classification for GC cases.

Molecular profile and copy number analysis of sporadic colorectal cancer in Taiwan

BackgroundColorectal cancer (CRC) is a major health concern worldwide, and recently becomes the most common cancer in Asia. The case collection of this study is one of the largest sets of CRC in Asia, and serves as representative data for investigating genomic differences between ethnic populations. We took comprehensive and high-resolution approaches to compare the clinicopathologic and genomic profiles of microsatellite instability (MSI) vs. microsatellite stability (MSS) in Taiwanese sporadic CRCs.Methods1,173 CRC tumors were collected from the Taiwan population, and sequencing-based microsatellite typing assay was used to determine MSI and MSS. Genome-wide SNP array was used to detect CN alterations in 16 MSI-H and 13 MSS CRCs and CN variations in 424 general controls. Gene expression array was used to evaluate the effects of CN alterations, and quantitative PCR methods were used to replicate the findings in independent clinical samples.ResultsThese 1,173 CRC tumors can be classified into 75 high-frequency MSI (MSI-H) (6.4%), 96 low-frequency MSI (8.2%) and 1,002 MSS (85.4%). Of the 75 MSI-H tumors, 22 had a BRAF mutation and 51 showed MLH1 promoter hypermethylation. There were distinctive differences in the extent of CN alterations between CRC MSS and MSI-H subtypes (300 Mb vs. 42 Mb per genome, p-value < 0.001). Also, chr7, 8q, 13 and 20 gains, and 8p and 18 losses were frequently found in MSS but not in MSI-H. Nearly a quarter of CN alterations were smaller than 100 kb, which might have been missed in previous studies due to low-resolution technology. 514 expressed genes showed CN differences between subtypes, and 271 of them (52%) were differentially expressed.ConclusionsSporadic CRCs with MSI-H displayed distinguishable clinicopathologic features, which differ from those of MSS. Genomic profiling of the two types of sporadic CRCs revealed significant differences in the extent and distribution of CN alterations in the cancer genome. More than half of expressed genes showing CN differences can directly contribute to their expressional diversities, and the biological functions of the genes associated with CN changes in sporadic CRCs warrant further investigation to establish their possible clinical implications.

Abstract 3899: Anti-cancer drugs increases microsatellite instability in human colorectal cancer cells

Abstract Manifested as microsatellite instability (MSI), DNA mismatch repair (MMR) deficiency is known to contribute to colorectal cancer pathogenesis and drug resistance. Growing evidence indicates that MMR deficiency is also widespread among secondary cancers in patients who have received chemotherapy. It is unclear what chemotherapeutic agents cause MMR deficiency. In this study, we aim at identifying the MSI-inducing anti-cancer drugs. To facilitate the identification, we developed an in-vivo dual fluorescent reporter system in a human colorectal cancer cell model using RFP that contains a microsatellite as the MSI reporter and GFP as the cell label. Based on flow cytometric analysis, we found that test anti-cancer drugs increased the MSI frequency in a dose-dependent manner. This was confirmed by fluorescent microscopy. With the NCI recommended markers, we detected a low frequency of MSI in cells after treated with a couple, but not all, of test anti-cancer drugs. Our cell-based MSI reporter assay will facilitate large scale screens of MSI-inducing and MSI-reducing drugs/compounds, which might provide treatment strategies for controlling therapy-related secondary cancers. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3899. doi:10.1158/1538-7445.AM2011-3899