Sporadic colorectal carcinomas with low-level microsatellite instability: a distinct subgroup with specific clinicopathological and molecular features

Low level of microsatellite instability correlates with short disease-free survival of gastric cancer patients undergoing neoadjuvant chemotherapy

Limited studies have been reported about the function of low level of microsatellite instability (MSI-L) in cancer. The aim of our study is to unveil the prognostic role of MSI-L in gastric cancer (GC). One hundred nine patients with locally advanced GC (T3-4a, N+, M0) who underwent neoadjuvant chemotherapy plus gastrectomy with extended (D2) lymph node dissection were collected. Clinicopathological characteristics, tumour regression score, disease-free survival (DFS), and overall survival (OS) were analysed and correlated with the MSI status. The MSI status of 96 patients was identified (7 (7.3%) with MSI-H, 12 (12.5%) with MSI-L, and 77 (80.2%) with MSS). MSI-L was significantly correlated with perineural invasion (P = 0.009) and decreased MUC5AC expression (P = 0.042). Poor response to neoadjuvant chemotherapy in MSI-L patients (83.3% assessed as poor response) was observed (P = 0.501). Compared with patients with MSS tumours, patients with MSI-L tumours showed poor DFS (P = 0.018) with a hazard ratio (HR) of 2.839 (95% CI 1.131-7.124, P = 0.026) from multivariable cox regression analysis. However, this was not associated with OS (P = 0.063). MSI-L is an independent poor prognostic biomarker for the locally advanced gastric cancer treated with neoadjuvant chemotherapy. Further studies with larger sample sizes are needed for validation.

MSI-L/EMAST is a predictive biomarker for metastasis in colorectal cancer patients

BACKGROUND

Microsatellite instability (MSI) is a prognostic marker in colorectal cancer (CRC). The biological significance of MSI-low (MSI-L) phenotype and its differences with microsatellite stable (MSS) phenotype remains unclear. The aim of this study is indicating the role of mononucleotide repeat in identifying MSI-L and revealing the association of MSI-L with elevated microsatellite alterations at selected tetranucleotide repeats (EMAST) and oncologic outcome in CRC patients.

METHODS

MSI and EMAST status were analyzed using three quasimonomorphic panel (BAT-25, BAT-26, and NR-27) and five tetranucleotide repeats (D20S82, D20S85, D9S242, D8S321, and MYCL1), respectively, by capillary electrophoresis method without the need to fluorescent primers. The associations of MSI status with clinicopathological features, EMAST status, metastasis, and overall survival (OS) were investigated.

RESULTS

Among 159 CRC patient 22.0% were MSI-H, 40.3% were MSS, 37.7% were MSI-L, and 41.5% showed EMAST + phenotype. MSI-L were associated with advanced stages, EMAST⁺ tumors and worse OS ( p ≤ 0.001). Metastasis was relatively common in MSI-L/EMAST ⁺ CRCs and BAT-25 were the most unstable marker in these tumors.

CONCLUSIONS

MSI-L tumors have different clinicopathological features from MSS and MSI-H tumors. The MSI-L phenotype is a worse prognostic biomarker in CRC and when accompanied by EMAST could be a predictor for metastasis.

The significance of microsatellite instability in colorectal cancer after controlling for clinicopathological factors

The colorectal cancer (CRC) patients with microsatellite instability (MSI) have distinct clinicopathological characteristics consisting of factors predicting positive and negative outcomes, such as a high lymph node harvest and poor differentiation. In this study, we measured the value of MSI as a prognostic factor after controlling for these discrepant factors. A total of 603 patients who underwent curative surgery for stages I to III colorectal cancer were enrolled. The patients were divided into microsatellite instability high (MSI-H) and microsatellite stable/microsatellite instability low (MSS/MSI-L) groups. Propensity score matching was used to match clinicopathological factors between the 2 groups. MSI-H patients had a high lymph node harvest (median: 31.0 vs 23.0, P < .001), earlier-stage tumors (P < .001), advanced T stage (89.3% vs 74.0%, P = .018), and poor differentiation (19.6% vs 2.0%, P < .001). Survival analysis showed better survival in the MSI-H group, but the difference was not statistically significant (P = .126). Propensity score matching was performed for significant prognostic factors identified by Cox hazard regression. After the matching, the survival difference by MSI status was estimated to be larger than before, and reached statistical significance (P = .045). In conclusion, after controlling for pathological characteristics, MSI-H could be a potent prognostic factor regarding patient survival.

Inflammation-associated microsatellite alterations: Mechanisms and significance in the prognosis of patients with colorectal cancer

Microsatellite alterations within genomic DNA frameshift as a result of defective DNA mismatch repair (MMR). About 15% of sporadic colorectal cancers (CRCs) manifest hypermethylation of the DNA MMR gene MLH1, resulting in mono- and di-nucleotide frameshifts to classify it as microsatellite instability-high (MSI-H) and hypermutated, and due to frameshifts at coding microsatellites generating neo-antigens, produce a robust protective immune response that can be enhanced with immune checkpoint blockade. More commonly, approximately 50% of sporadic non-MSI-H CRCs demonstrate frameshifts at di- and tetra-nucleotide microsatellites to classify it as MSI-low/elevated microsatellite alterations at selected tetranucleotide repeats (EMAST) as a result of functional somatic inactivation of the DNA MMR protein MSH3 via a nuclear-to-cytosolic displacement. The trigger for MSH3 displacement appears to be inflammation and/or oxidative stress, and unlike MSI-H CRC patients, patients with MSI-L/EMAST CRCs show poor prognosis. These inflammatory-associated microsatellite alterations are a consequence of the local tumor microenvironment, and in theory, if the microenvironment is manipulated to lower inflammation, the microsatellite alterations and MSH3 dysfunction should be corrected. Here we describe the mechanisms and significance of inflammatory-associated microsatellite alterations, and propose three areas to deeply explore the consequences and prevention of inflammation's effect upon the DNA MMR system.

Major improvement in the detection of microsatellite instability in colorectal cancer using HSP110 T17 E-ice-COLD-PCR

Every colorectal cancer (CRC) patient should be tested for microsatellite instability (MSI) to screen for Lynch syndrome. Evaluation of MSI status involves screening tumor DNA for the presence of somatic deletions in DNA repeats using PCR followed by fragment analysis. While this method may lack sensitivity due to the presence of a high level of germline DNA, which frequently contaminates the core of primary colon tumors, no other method developed to date is capable of modifying the standard PCR protocol to achieve improvement of MSI detection. Here, we describe a new approach developed for the ultra-sensitive detection of MSI in CRC based on E-ice-COLD-PCR, using HSP110 T17, a mononucleotide DNA repeat previously proposed as an optimal marker to detect MSI in tumor DNA, and an oligo(dT)₁₆ LNA blocker probe complementary to wild-type genotypes. The HT17 E-ice-COLD-PCR assay improved MSI detection by 20-200-fold compared with standard PCR using HT17 alone. It presents an analytical sensitivity of 0.1%-0.05% of mutant alleles in wild-type background, thus greatly improving MSI detection in CRC samples highly contaminated with normal DNA. HT17 E-ice-COLD-PCR is a rapid, cost-effective, easy-to-implement, and highly sensitive method, which could significantly improve the detection of MSI in routine clinical testing.

Surgical treatment of multiple sporadic colorectal carcinoma

Aim: Many aspects of the surgical management of multiple sporadic colorectal cancer syndrome, either synchronous and metachronous, remain to be cleared, in particular the prognostic influence of the extent of surgical resection. Method: A retrospective review was performed of patients diagnosed with multiple colorectal cancer from 1982 to May 2010. Clinical and pathologic data were collected and reviewed. Survival analysis was performed. Results: We identified 23 patients with multiple sporadic colorectal cancers, of which 8 had synchronous (SC) and 15 metachronous cancers (MC). Of the MC patients, 2 (13%) had the second cancer within 2 years, 4 (27%) in the time period of 2-5 years and 9 (60%) after 5 years. Twenty-one patients underwent multiple segmental resections; 2 patients underwent subtotal colectomy. The 5-year overall survival rate of SC and MC patients was 100% and 87% (p<0.001) respectively. The 5-year overall survival rate of multiple segmental resection patients and subtotal colectomy was 94% and 75% (p=0.655) respectively. Conclusion: Either synchronous and metachronous MSCRC patients showed good prognosis independently from to the extent of resection. Our results support a less aggressive biological behaviour allowing a more conservative management. Multiple segmental colorectal resections seem appropriate from an oncologic point of view in MSCRC patients. (www.actabiomedica.it)

Low-Level Microsatellite Instability as a Potential Prognostic Factor in Sporadic Colorectal Cancer

Although microsatellite instability-high (MSI-H) colorectal cancers (CRCs) have been shown to exhibit a distinct phenotype, the clinical value of MSI-low (MSI-L) in CRC remains unclear. We designed this study to examine the clinicopathologic characteristics and oncologic implications associated with MSI-L CRCs. We retrospectively reviewed data of CRC patients from 3 tertiary referral hospitals in Korea, who underwent surgical resection between January 2003 and December 2009 and had available MSI testing results. MSI testing was performed using the pentaplex Bethesda panel. Clinicopathologic features and oncologic outcomes were compared between MSI-L and microsatellite stable (MSS) CRCs; prognostic factors for survival were also examined. Of the 3019 patients reviewed, 2621 (86.8%) were MSS, and 200 (6.6%) were MSI-L; the remaining 198 (6.6%) were MSI-H. MSI-L and MSS CRCs were comparable in terms of their clinicopathologic features, with the exception of proximal tumor location (MSI-L 30.0% vs MSS 22.1%, P = 0.024) and tumor size (MSI-L 5.2 ± 2.6  cm vs MSS 4.6 ± 2.1  cm, P = 0.001). No differences were detected in either 3-year disease-free survival (MSI-L 87.2% vs MSS 82.6%, P = 0.121) or 5-year overall survival (OS) (MSI-L 74.2% vs MSS 78.3%, P = 0.131) by univariable analysis. However, MSI-L was an independent prognostic factor for poor OS by Cox regression analysis (hazard ratio 1.358, 95% confidence interval 1.014-1.819, P = 0.040). MSI-L may be an independent prognostic factor for OS in sporadic CRCs despite their clinicopathologic similarity to MSS. Further studies investigating the significance of MSI-L in the genesis and prognosis of CRCs are needed.

Role of topoisomerase I and thymidylate synthase expression in sporadic colorectal cancer: associations with clinicopathological and molecular features

Topoisomerase I (Topo I) and thymidylate synthase (TS) are essential enzymes for the replication, transcription and repair of DNA, and are potential biomarkers in colorectal cancer (CRC). The aim of the study was to correlate the tissue expression of Topo I and TS in sporadic CRCs with relevant pathological and molecular features and patients' outcome. Topo I and TS expression was assessed by immunostaining in 112 consecutive primary CRCs. Increased expression of Topo I was found in 36% of tumors, preferentially rectal (50%) and with not otherwise specified (NOS) histology (44%). Topo I expression was associated with 18q allelic loss (LOH), (p=0.013), microsatellite stable phenotype (p=0.002) and normal expression of mismatch proteins hMLH1 and hMSH2 (p=0.0012 and p=0.02, respectively). High TS expression was found in 60% of tumors, more frequently in distal sites (62%) and with NOS histology (66%); no association with microsatellite instability was observed. Topo I seems to be involved in the chromosomal instability pathway of sporadic CRCs. Conversely, high TS expression is unlikely to affect the clinical behavior of microsatellite unstable CRCs.

Lymph node ratio is a stronger prognostic factor than microsatellite instability in colorectal cancer patients: results from a 7 years follow-up study

BACKGROUND

The presence of high microsatellite instability (MSI-H) in colorectal cancers has been generally associated with better survival, opposite an increased ratio between metastatic lymph-nodes and nodes sampled in the specimen (LNR) has been associated with a worse outcome. The study aims to detect the incidence and prognostic significance of MSI and LNR in a consecutive series of 119 colorectal cancers.

METHODS

119 consecutive colorectal cancer patients undergone resection at our Department were enrolled from 2000 to 2004. The MSI status has been evaluated by amplification of target sequences. The LNR has been calculated and patients stratified into 4 groups on the basis of the ratio values. Clinical/pathological data were collected and analyzed; the overall, disease free and disease specific survivals were analyzed by the Kaplan-Meier and Cox regression analyses (mean follow-up: 81 months).

RESULTS

MSI-H was detected in 11.7% of the cases and patients were compared with the microsatellite stable (MSS) group. We observed a higher prevalence of right colon localizations (p 0.01) and locally advanced tumors (p 0.0012) in the MSI-H subgroup. Kaplan-Meier analysis documented no significant difference comparing MSS patients vs MSI-H, although the latter showed a better survival trend (p ns); worse survivals were observed according with the LNR stratification (p < 0.0001). Multivariate analysis documented a statistical value associated with the LNR sub-groups in relationship with survival.

CONCLUSION

According to our results the MSI-H status was associated with particular features (right locations/locally advanced tumors). The results of a long-term follow-up indicate a trend for better survival in MSI-H vs MSS patients. Notably, an increased LNR is associated with worse survivals, both at the univariate and multivariate analysis, displaying this ratio as the strongest prognostic factor of cancer-related survival.

The Correlation between Microsatellite Instability and the Features of Sporadic Colorectal Cancer in the North Part of Iran

Background. The aim of this study was to determine the correlation between MSI and sporadic colorectal cancer in Guilan province, North part of Iran. Materials and Methods. A total of 96 patients who underwent resection for sporadic colorectal cancer in Guilan province were studied. No patients had positive family history of cancers. The frequencies of MSI were analyzed by testing the BAT-26 and BAT-25 markers. Results. MSI analysis revealed that 22.9% of the tumors (22 patients) were microsatellite instability positive and 77.1% (74 patients) were microsatellite instability negative. The highest rate of MSI (40.9%) was found in the rectal region. MSI-H status was seen more frequently in distal tumors (P = 0.04, odds ratio = 3.13, 0.96–10.14). Conclusions. Distal tumor location and MSI may associate with special clinicopathological features. It seems that there may be correlation with underlying genetic and immunologic mechanisms.