Deficient DNA mismatch repair is associated with favorable prognosis in Thai patients with sporadic colorectal cancer

Rate of dissemination and prognosis in early and advanced stage colorectal cancer based on microsatellite instability status: systematic review and meta-analysis

INTRODUCTION

For the past two decades, microsatellite instability (MSI) has been reported as a robust clinical biomarker associated with survival advantage attributed to its immunogenicity. However, MSI is also associated with high-risk adverse pathological features (poorly differentiated, mucinous, signet cell, higher grade) and exhibits a double-edged sword phenomenon. We performed a systematic review and meta-analysis to evaluate the rate of dissemination and the prognosis of early and advanced stage colorectal cancer based on MSI status.

METHODS

A systematic literature search of original studies was performed on Ovid searching MEDLINE, Embase, Cochrane Database of Systematic Reviews, American College of Physicians ACP Journal Club, Database of Abstracts of Reviews of Effects DARE, Clinical Trials databases from inception of database to June 2019. Colorectal cancer, microsatellite instability, genomic instability and DNA mismatch repair were used as key words or MeSH terms. The Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) reporting guideline was followed. Data were pooled using a random-effects model with odds ratio (OR) as the effect size. Statistical analysis was performed using RevMan ver 5.3 Cochrane Collaboration.

RESULTS

From 5288 studies, 136 met the inclusion criteria (n = 92,035; MSI-H 11,746 (13%)). Overall, MSI-H was associated with improved OS (OR, 0.81; 95% CI 0.73-0.90), DFS (OR, 0.73; 95% CI 0.66-0.81) and DSS (OR, 0.69; 95% CI 0.52-0.90). Importantly, MSI-H had a protective effect against dissemination with a significantly lower rate of lymph node and distant metastases. By stage, the protective effect of MSI-H in terms of OS and DFS was observed clearly in stage II and stage III. Survival in stage I CRC was excellent irrespective of MSI status. In stage IV CRC, without immunotherapy, MSI-H was not associated with any survival benefit.

CONCLUSIONS

MSI-H CRC was associated with an overall survival benefit with a lower rate of dissemination. Survival benefit was clearly evident in both stage II and III CRC, but MSI-H was neither a robust prognostic marker in stage I nor stage IV CRC without immunotherapy.

Loss of CDX-2 expression is an independent poor prognostic biomarker in patients with early-stage deficient mismatch repair colorectal cancer

AIM

To investigate the clinicopathological factors, molecular features, and prognostic implications associated with loss of Caudal-related homeobox transcription factor 2 (CDX-2) expression in colorectal cancer (CRC) patients.

METHODS

Immunohistochemistry for CDX-2 expression was performed on formalin-fixed, paraffin-embedded primary CRC tissue samples from 449 patients. Correlation between CDX-2 expression and clinicopathological and molecular characteristics was evaluated. Univariate and multivariate survival analyses were performed to determine the prognostic value of loss of CDX-2 expression.

RESULTS

Of 449 patients, 84% were stage I-III. CDX-2-negative expression was identified in 18 of 441 (4.1%) patients. Loss of CDX-2 expression was more commonly found in patients with right-sided tumors rather than left-sided tumors (odds ratio [OR] = 3.57; p = 0.009), deficient mismatch repair (dMMR) compared to proficient MMR (pMMR) (OR = 3.7; p = 0.012), and BRAF mutation compared to BRAF wild type (OR = 8.06; p = 0.002). Univariate analysis revealed that stage I-III CRC patients with loss of CDX-2 expression had significantly worse overall survival (OS) and disease-free survival (DFS) than those with positive CDX-2 expression (5-year OS = 33.3% vs. 74.6%, respectively; p < 0.001, and 5-year DFS: 42.9% vs. 69.5%, respectively; p = 0.004). Loss of CDX-2 expression remained significantly associated with worse OS compared to positive CDX-2 expression in multivariate analysis (hazard ratio [HR] = 2.4; 95% confidence interval [CI], 1.12-5.11; p = 0.023).

CONCLUSIONS

Loss of CDX-2 expression was found to be associated with right-sided tumor, dMMR status, and BRAF mutation. Moreover, loss of CDX-2 expression is a poor prognostic factor for OS in stage I-III, even among patients with dMMR tumors.

SELE gene as a characteristic prognostic biomarker of colorectal cancer

OBJECTIVE

To investigate the expression and clinical value of the E-selectin gene (SELE) in colorectal cancer (CRC).

METHODS

Using gene expression profiles and clinicopathological data for patients with CRC from The Cancer Genome Atlas, and tumor and adjacent normal tissues from 31 patients with CRC from Xianyang Central Hospital, we studied the correlation between SELE gene expression and clinical parameters using Kaplan-Meier and Cox proportional hazards regression analyses.

RESULTS

Higher expression of SELE was significantly associated with a poorer prognosis and shorter survival in patients with CRC. The median expression level of SELE was significantly higher in CRC tissues compared with healthy adjacent tissue. Cox regression analysis showed that the prognosis of CRC was significantly correlated with the expression of SELE. Immunohistochemical analysis also showed that positive expression of E-selectin increased significantly in line with increasing TNM stage.Conclusion: This study confirmed that SELE gene expression is an independent prognostic factor in patients with CRC.

Comparison of universal screening in major lynch-associated tumors: a systematic review of literature

Lynch syndrome (LS) is associated with an increased lifetime risk of several cancers including colorectal (CRC), endometrial (EC), ovarian (OC), urinary (UT) and sebaceous tumors (ST). The benefit for universal screening in CRC and EC is well known. However, this benefit in other major lynch-associated tumors is unclear. We performed a systematic review of all published articles in the MEDLINE database between 2005 to 2017 to identify studies performing universal screening for LS in unselected CRC, EC, OC, UT and ST. All cases with MSI-H (instability in two or more markers) or missing one or more proteins on IHC testing were considered screening positive. Cases with MLH1 promoter hypermethylation or BRAF mutation positive were considered to have somatic mutations. A total of 3788 articles were identified in MEDLINE yielding 129 study arms from 113 studies. The overall pooled yield of universal LS screening and germline mismatch gene mutation was significantly different across the major LS-associated tumors (Mann Whitney test, p < 0.001). The pooled screening yield was highest in ST [52.5% (355/676), 95% CI 48.74-56.26%] followed by EC [22.65% (1142/5041), 95% CI 21.54-23.86%], CRC [11.9% (5649/47,545), 95% CI 11.61-12.19%], OC [11.29% (320/2833), 95% CI 10.13-12.47%] and UT [11.2% (31/276), 95% CI 7.48-14.92%]. ST also had the highest pooled germline positivity for mismatch repair gene mutation [18.8%, 33/176, 95%CI 13.03-24.57], followed by EC [2.6% (97/3765), 95% CI 2.09-3.11], CRC [1.8% (682/37,220), 95% CI 1.66-1.94%], UT [1.8%(3/164), 95% CI - 0.24-3.83%] and OC [0.83%(25/2983), 95% CI 0.48-1.12%]. LS screening in EC yielded significantly higher somatic mutations compared to CRC [pooled percentage 16.94% [(538/3176), 95%CI 15.60-18.20%] vs. 5.23% [(1639/26,152), 95% CI 4.93-5.47%], Mann Whitney test, p < 0.0001. Universal LS testing should be routinely performed in OC, UT and STs in addition to CRC and EC. Our findings also support consideration for IHC and somatic mutation testing before germline testing in EC due to higher prevalence of somatic mutations as well as germline testing in all patients with ST. Our results have implications for future design of LS screening programs and further studies are needed to assess the cost effectiveness and burden on genetic counselling services with expanded universal testing for LS.

Duration of FOLFOX Adjuvant Chemotherapy in High-Risk Stage II and Stage III Colon Cancer With Deficient Mismatch Repair

Background

We evaluated the impact of 3 months of mFOLFOX6 adjuvant chemotherapy or surgery alone in comparison with 6 months of mFOLFOX6 on disease-free survival (DFS) in deficient mismatch repair (dMMR) colon cancer (CC) patients.

Methods

This retrospective study identified a cohort of patients with high-risk stage II and III dMMR CC who underwent curative surgery between May 2011 and July 2019. DFS was compared using the Kaplan-Meier survival methods and Cox proportional hazards models. Propensity-score matching was performed to reduce imbalance in baseline characteristics.

Results

A total of 242 dMMR CC patients were identified; 66 patients received 6 months of mFOLFOX6, 87 patients received 3 months of mFOLFOX6, and 89 patients were treated with surgery alone. The 3-year DFS rate was 72.8% in 3-month therapy group and 86.1% in 6-month therapy group, with a hazard ratio (HR) of 2.78 (95CI%, 1.18 to 6.47; P= 0.019). The difference in DFS between surgery alone group and 6-month therapy group was also observed but was nonsignificant (HR= 2.30, 95%CI, 0.99 to 5.38; P=0.054). The benefit of 6-month therapy in DFS compared with 3-month therapy group was pronounced for patients with stage III (HR=2.81, 95%CI, 1.03 to 7.67; P=0.044) but not for high-risk stage II patients. Propensity score matched analysis confirmed a DFS benefit in the 6-month therapy group.

Conclusion

This study suggested that a 6-month duration of mFOLFOX6 adjuvant chemotherapy in dMMR CC patients may be associated with improved DFS compared with 3-month therapy, particularly in patients with stage III. The observational nature of the study implies caution should be taken in the interpretation of these results.

Clinicopathological Characteristics and Outcome of Adolescent and Young Adult-Onset Microsatellite Stable Colorectal Cancer Patients

Purpose: Colorectal cancer (CRC) incidence is increasing in adults younger than 50 years. This study evaluated clinicopathological characteristics and outcome of adolescent and young adult (AYA)-onset sporadic CRC patients. Methods: Medical records of patients who were diagnosed adenocarcinoma of colon or rectum at Siriraj Hospital between 2007 and 2018 were retrospectively reviewed. The patients were classified into two groups: AYA-onset CRC (age 15-39 years) and adult-onset CRC (age >50 years). Associations between sporadic microsatellite stable (MSS) AYA-/adult-onset CRC and clinicopathological features and outcome were evaluated. Results: A total of 203 patients were diagnosed with AYA-onset CRC with no known history of familial CRC syndromes, 119 had data on mismatch repair status; 98 confirmed MSS CRC. AYA-onset CRC patients were commonly found with left-sided rather than right-sided tumors (77.1% vs. 22%) and late stage of disease (80.7% in stage III-IV vs. 19.3% in stage I-II). Compared with adult-onset CRC (218 patients), AYA-onset MSS CRC had more patients with female gender (p = 0.038), perineural invasion (p = 0.003), and signet ring cell/mucinous histology (p = 0.132). On univariate analysis, male gender and mucinous/signet ring cell histology had worse overall survival (OS) (p = 0.004 and p = 0.072, respectively) and remained significant in multivariate analysis for signet ring cell histology (p = 0.008). There was no difference in disease-free survival and OS between both age groups. Conclusions: Sporadic MSS AYA-onset CRC patients were associated with female gender and aggressive pathological characteristics. However, there was no difference in survival outcome between AYA-onset and adult-onset groups.

Mismatch repair status between primary colorectal tumor and metastatic tumor, a retrospective consistent study

Objectives Mismatch repair (MMR) and Microsatellite instability (MSI) are critical when considering immunotherapy and chemotherapeutic drugs an option for patients with colorectal cancer (CRC). We investigated the consistence of MMR status as well as MSI between primary CRC and metastatic tumor to see if the expression of four MMR proteins and the status of MSI are congruent in primary tumor and metastatic tumor. With the results of the study and future more relevant studies, the sites of MMR testing may be more precise for individualized treatment.

Study design Patients with clear diagnosis of sporadic CRC and distal organ metastasis were identified from a prospectively established database. The status of MMR and MSI was evaluated by immunohistochemistry (IHC) and Polymerase Chain Reaction (PCR) respectively of synchronously obtained tissue samples.

Results Forty patients with complete clinical date were enrolled. For primary tumor, 36/40 samples were tested as MMR-proficient (pMMR) and 4 were MMR-deficient (dMMR). For metastatic samples, 30 samples were tested as pMMR while 10 samples were dMMR. Six out of forty patients were tested as inconsistent status of MMR and MSI. After statistical analysis, the expression status of MMR was not statistically significant between primary and metastatic tumors (P=0.1405, larger than 0.05).

Conclusion Based on our samples, the status of MMR between primary CRC and metastatic tumor was consistent, thus test of MMR status can be performed at both sites. However, due to the limited samples enrolled in our study, the results should be interpreted carefully.

Worldwide variation in lynch syndrome screening: case for universal screening in low colorectal cancer prevalence areas

To perform a systematic assessment of universal Lynch syndrome (LS) screening yield in colorectal cancer (CRC) patients around the world. Universal screening for LS is recommended in all CRC patients. However, the variation in yield of LS screening in the setting of significant global variation in CRC prevalence is unknown. A systematic review of articles in the MEDLINE database was performed to identify studies performing universal screening for LS. All cases with microsatellite instability (MSI-H) or missing one or more proteins on immunohistochemistry (IHC) were considered screening positive. The overall pooled yield of universal LS screening in 97 study arms from 89 identified studies was 11.9% (5649/47545) and the overall pooled percentage of confirmed LS patients was 1.8% (682/37220). LS screening positivity varied significantly based on geographic region (Kruskal Wallis test, p < 0.001) and reported 5-year CRC prevalence in the country (Fisher's exact, p < 0.001). Significant inverse correlation was found between LS screening positivity and 5-year CRC prevalence (Pearson correlation, r =  - 0.56, p < 0.001). The overall yield of LS screening was 15.00% (382/2553) and rate of confirmed LS was 7.7% (113/1475) in LS screening done in patients ≤ 50 years (16 studies). There is significant geographic variation in LS screening positivity with higher yield in countries with lower prevalence of CRC. Our results highlight the importance of universal LS screening in younger patients and low CRC prevalence countries.

Less correlation between mismatch repair proteins deficiency and decreased expression of HLA class I molecules in endometrial carcinoma: a different propensity from colorectal cancer

Mismatch repair protein deficiency (dMMR) is a favorable prognostic factor in colorectal cancer. It is also associated with aberrant expression of HLA class I molecules, which are required for cytotoxic T lymphocyte-mediated cancer immunotherapy. Because dMMR is frequently also found in endometrial cancers (ECs), we retrospectively investigated the expression of mismatch repair proteins and HLA class I molecules in 127 EC patients. In this study, EC patients being treated in our hospital were recruited from 2005 to 2009 and observed until December 2017. Lesion specimens were evaluated via immunohistochemistry for MSH6 and PMS2 (mismatch repair proteins) and HLA class I molecules. Expression of these molecules was statistically related to clinical and pathological factors and prognosis. dMMR was detected in 33 patients and did not correlate with the expression level of HLA class I molecules (P = 0.60). On the other hand, unexpectedly, multivariate analysis revealed that intact expression of HLA class I molecules was associated with p53 overexpression (P = 0.004). Neither dMMR nor decreased expression of HLA class I molecules were prognostic factors. These results are inconsistent with previous findings for colorectal cancer. A distinctive local tissue immune microenvironment would underlie the discrepancy in the results between EC and colorectal cancer.

Prevalence of RAS and BRAF mutations in metastatic colorectal cancer patients by tumor sidedness: A systematic review and meta-analysis

Studies have shown that the prevalence of RAS and BRAF mutations may differ by tumor sidedness among metastatic colorectal cancer (mCRC) patients. Both mutation status and tumor sidedness may impact survival and disease progression and RAS mutation status has been shown to predict response to anti‐epidermal growth factor receptor (EGFR) therapy. A systematic literature review and meta‐analysis were conducted to estimate the pooled prevalence of RAS and BRAF mutations by tumor sidedness in studies of mCRC patients. Forty‐four studies comprising 15 981 mCRC patients tested for RAS and/or BRAF mutations were included in the meta‐analyses. The prevalence of RAS mutations differed significantly by tumor side (32.4% among left‐sided tumors, 41.3% among right‐sided tumors; P = .017), as did the prevalence of KRAS mutations (35.8% among left‐sided tumors, 46.3% among right‐sided tumors; P < .0001) and BRAF mutations (4.3% among left‐sided tumors, 16.3% among right‐sided tumors; P < .0001). Among right‐sided tumors, the prevalence of RAS and KRAS mutations varied significantly by study design, with higher prevalence among observational studies than clinical trials, and there was significant variation by study location for the prevalence of KRAS mutations in left‐sided tumors and the prevalence of BRAF mutations in right‐sided tumors. These results help to better characterize the mCRC population to better inform clinicians and researchers. Few of the included studies reported overall or progression‐free survival (PFS) by both tumor sidedness and mutation status. As both of these factors may have prognostic impact, future studies should consider evaluating survival by these variables.

Prevalence of BRAF gene mutation in samples of primary and metastatic colorectal cancer: A meta-analysis

INTRODUCTION

Understanding the prevalence and biology of BRAF gene can improve the treatment methods of cancerous patients. This study aims to estimate the prevalence of BRAF gene mutation in samples of primary and metastatic colorectal cancer using meta-analysis method.

METHODS

We searched PubMed, Scopus, ScienceDirect, Ovid and Google Scholar motor engine using MeSH terms of relevant keywords. During the screening phase, titles, abstracts and full texts were reviewed and risk of bias was assessed for all selected papers based on Newcastle-Ottawa Scale (NOS) checklist. The results of the primary studies were combined using meta-analysis.

RESULTS

Of 95 eligible studies entered into the meta-analysis, prevalence of BRAF gene mutation had been assessed among 19,484 primary tumour samples as well as 12,256 metastatic samples. The total prevalence of BRAF gene mutation among primary tumour samples was estimated as of 10.16% (8.09-12.22) in the world, 0.41% (0-1.89) in EMRO region, 10.06% (7.54-12.59) in EURO region, 10.33% (7.24-13.43) in SEARO region and 11.33% (7.29-15.37) in WPRO region. The pooled estimates for BRAF gene mutation in metastatic samples were 6.53% (5.09-7.96), 8.07% (5.57-10.56), 5.38% (3.75-7.02) and 5.55% (1.72-9.38) for all regions, EURO, WPRO and PAHO regions respectively.

CONCLUSION

Our results showed evidences of BRAF gene mutation in one-tenth of primary colorectal tumour samples in EURO, PAHO, SEARO and WPRO regions which was considerably higher than that of the EMRO region.

Role of intravoxel incoherent motion MRI in preoperative evaluation of DNA mismatch repair status in rectal cancers

AIM

To explore the role of intravoxel incoherent motion (IVIM) magnetic resonance imaging (MRI) in evaluating DNA mismatch repair (MMR) status of rectal cancers preoperatively.

MATERIALS AND METHODS

Seventy-six patients with a diagnosis of rectal cancer confirmed at endoscopic biopsy were enrolled prospectively and underwent IVIM MRI before surgery.

RESULTS

The perfusion fraction (f) values of MMR proteins (MMRP) positive rectal cancers were significantly higher than negative cancers. The f values could differentiate MMRP positive rectal cancers from negative cancers with an area under the curve (AUC) of 0.695. The vascular endothelial growth factor (VEGF) and vascular endothelial growth factor receptor 2 (VEGFR2) expression rates of positive MMRP rectal cancers were significantly higher than negative cancers.

CONCLUSION

This pilot study indicated that the f value derived from IVIM MRI differed significantly between rectal cancers with different MMRP expression levels, which might be involved with different VEGF and VEGFR2 expression rates.

High Frequency of KRAS Codon 146 and FBXW7 Mutations in Thai Patients with Stage II-III Colon Cancer

Background: KRAS, NRAS, and BRAF gene mutations are the most clinically relevant and frequently reported in colorectal cancer (CRC). Although data on these genes are frequently reported in several counties, data specific to these genes among Thai population are scarce. The aim of this study was to investigate and identify molecular alterations associated with colon cancer in Thai population, and to determine the impact of these genetic aberrations on clinical outcome. Methods: DNA from 108 archived formalin-fixed, paraffin-embedded (FFPE) tissue samples that histologically confirmed adenocarcinoma of stage II-III colon cancer between 2010 and 2012 at Siriraj Hospital (Bangkok, Thailand) were extracted. Gene mutational analysis was performed by next-generation sequencing (NGS) using an Oncomine Solid Tumor DNA kit (Thermo Fisher Scientific, Inc., Waltham, MA, USA). Results: A total of 22 somatic gene mutations were detected. The mutation frequency observed in KRAS, NRAS, BRAF, PIK3CA, and FBXW7 mutations was 47.2%, 1.9%, 1.9%, 12%, and 14.8%, respectively. KRAS mutation codon 12, 13, 59, 61, 117, and 146 mutations were identified in 29.6%, 8.3%, 1.8%, 0.9%, 0.0%, and 8.3%, respectively. KRAS Exon 4 had better DFS compared with Exon 2 and 3. Conclusions: This study is the first to comprehensively report hotspot mutations using NGS in Thai colon cancer patients. The most commonly identified gene mutation frequencies among Thai patients (KRAS, NRAS, BRAF, TP53, and PIK3CA) were similar to the gene mutation frequencies reported in Western population, except for subgroup of KRAS codon 146 and FBXW7 mutations that had a slightly higher frequency.

Mutations of key driver genes in colorectal cancer progression and metastasis

The association between mutations of key driver genes and colorectal cancer (CRC) metastasis has been investigated by many studies. However, the results of these studies have been contradictory. Here, we perform a comprehensive analysis to screen key driver genes from the TCGA database and validate the roles of these mutations in CRC metastasis. Using bioinformatics analysis, we identified six key driver genes, namely APC, KRAS, BRAF, PIK3CA, SMAD4 and p53. Through a systematic search, 120 articles published by November 30, 2017, were included, which all showed roles for these gene mutations in CRC metastasis. A meta-analysis showed that KRAS mutations (combined OR 1.18, 95% CI 1.05-1.33) and p53 mutations (combined OR 1.49, 95% CI 1.23-1.80) were associated with CRC metastasis, including lymphatic and distant metastases. Moreover, CRC patients with a KRAS mutation (combined OR 1.29, 95% CI 1.13-1.47), p53 mutation (combined OR 1.35, 95% CI 1.06-1.72) or SMAD4 mutation (combined OR 2.04, 95% CI 1.41-2.95) were at a higher risk of distant metastasis. Subgroup analysis stratified by ethnic populations indicated that the BRAF mutation was related to CRC metastasis (combined OR 1.42, 95% CI 1.18-1.71) and distant metastasis (combined OR 1.51, 95% CI 1.20-1.91) in an Asian population. No significant association was found between mutations of APC or PIK3CA and CRC metastasis. In conclusion, mutations of KRAS, p53, SMAD4 and BRAF play significant roles in CRC metastasis and may be both potential biomarkers of CRC metastasis as well as therapeutic targets.

Colon Adenocarcinoma Stage IIA-Can We Predict Relapse?

PURPOSE

To determine prognostic factors for stage IIA colon cancer (CC) recurrence in patients undergoing curative intent surgery without adjuvant treatment.

METHODS

Single-centre cohort study. All patients with stage IIA CC discussed in a multidisciplinary colorectal cancer clinic from January 2010 to December 2012 were evaluated. Clinical data, laboratory data and tumour features, including expression of DNA repair proteins (EDRP), were analysed. Assessment of overall and disease free survival, recurrence, recurrence site and recurrence's method of diagnosis was performed. The associations between variables were tested through the Fisher's exact test (SPSS 23).

RESULTS

Fifty-five patients were included (55% male gender; mean age at diagnosis was 70.3 years (42-88)). CC was in the left colon in 62%, high grade in 7% and had lymphovascular invasion in 7% of the cases. Only one patient was submitted to emergent surgery for obstructive symptoms. In 55% of cases ≥ 12 lymph nodes were collected. There was EDRP loss in nine patients (MLH1/PMS2: six; MSH2/MSH6: three)-only two fulfilled revised Bethesda criteria. Recurrence occurred in five patients (8.9%), and it was diagnosed through surveillance in all of them. No variable showed a statistically significant association with recurrence; however, there were no recurrences in patients with EPRD loss (p = 0.209). Mean follow-up time was 43 months (2-70). In those with recurrence, mean disease-free survival was 23.4 months.

CONCLUSIONS

The overall good prognosis and absence of recurrence predictive factors were confirmed, validating the decision of not to submit stage IIA CC patients to chemotherapy risks.

Development of ultra-short PCR assay to reveal BRAF V600 mutation status in Thai colorectal cancer tissues

The protein kinase BRAF is one of the key players in regulating cellular responses to extracellular signals. Somatic mutations of the BRAF gene, causing constitutive activation of BRAF, have been found in various types of human cancers such as malignant melanoma, and colorectal cancer. BRAF V600E and V600K, most commonly observed mutations in these cancers, may predict response to targeted therapies. Many techniques suffer from a lack of diagnostic sensitivity in mutation analysis in clinical samples with a low cancer cell percentage or poor-quality fragmented DNA. Here we present allele-specific real-time PCR assay for amplifying 35- to 45-base target sequences in BRAF gene. Forward primer designed for BRAF V600E detection is capable of recognizing both types of BRAF V600E mutation, i.e. V600E1 (c.1799T>A) and V600E2 (c.1799_1800delTGinsAA), as well as complex tandem mutation caused by nucleotide changes in codons 600 and 601. We utilized this assay to analyze Thai formalin-fixed paraffin-embedded tissues. Forty-eight percent of 178 Thai colorectal cancer tissues has KRAS mutation detected by highly sensitive commercial assays. Although these DNA samples contain low overall yield of amplifiable DNA, our newly-developed assay successfully revealed BRAF V600 mutations in 6 of 93 formalin-fixed paraffin-embedded colorectal cancer tissues which KRAS mutation was not detected. Ultra-short PCR assay with forward mutation-specific primers is potentially useful to detect BRAF V600 mutations in highly fragmented DNA specimens from cancer patients.

Mismatch repair-deficient status associates with favorable prognosis of Eastern Chinese population with sporadic colorectal cancer

The present study aimed to investigate the expression level of DNA mismatch repair gene (MMR) in in sporadic colorectal cancer (SCRC) in eastern China, and to investigate the association between MMR status and prognosis of patients with SCRC. Patient archives from the Department of Gastrointestinal Surgery of Weihai Municipal Hospital (Weihai, China) were retrospectively collected between January 2011 and January 2012. Of the 221 consecutive patients identified, 192 patients who met the criterion were deemed eligible for inclusion. Immunohistochemistry (IHC) was conducted to detect the expression of MMR proteins MutL homolog 1 (MLH1), MutS homolog 2 (MSH2), MSH6 and PMS1 homolog 2, mismatch repair system component (PMS2) expression and mutation in sporadic colorectal cancer (SCRC). Kaplan-Meier plots and log-rank tests were performed to conduct survival analysis and Cox proportional hazard regression models were conducted to determine independent prognostic factors. The total rate of deficient MMR (dMMR) was 14.58% (28/192): MSH6, 0.52% (1/192); PMS2, 4.17% (8/192); MSH2/MSH6, 3.65% (7/192); and MLH1/PMS2, 6.25% (12/192). The dMMR group had a significantly longer overall survival time compared with proficient MMR (pMMR) group (P=0.017). Disease-free survival time of dMMR group was also longer than pMMR group (P=0.027). Multivariate analysis using the Cox regression model confirmed that MMR status was an independent prognostic factor for SCRC. Loss of MMR expression was indicative of a favorable outcome for patients with SCRC, and MMR status could be viewed as an independent prognostic factor.

Deficient mismatch repair and RAS mutation in colorectal carcinoma patients: a retrospective study in Eastern China

Objectives

To investigate the frequency and prognostic role of deficient mismatch repair (dMMR) and RAS mutation in Chinese patients with colorectal carcinoma.

Methods

Clinical and pathological information from 813 patients were reviewed and recorded. Expression of mismatch repair proteins was tested by immunohistochemistry. Mutation analyses for RAS gene were performed by real-time polymerase chain reaction. Correlations of mismatch repair status and RAS mutation status with clinicopathological characteristics and disease survival were determined.

Results

The overall percentage of dMMR was 15.18% (121/797). The proportion of dMMR was higher in patients <50 years old (p < 0.001) and in the right side of the colon (p < 0.001). Deficient mismatch repair was also associated with mucinous production (p < 0.001), poor differentiation (p < 0.001), early tumor stage (p < 0.05) and bowel wall invasion (p < 0.05). The overall RAS mutation rate was 45.88%, including 42.56% (346/813) KRAS mutation and 3.69% (30/813) NRAS mutation (including three patients with mutations in both). KRAS mutation was significantly associated with mucinous production (p < 0.05), tumor stage (p < 0.05) and was higher in non-smokers (p < 0.05) and patients with a family history of colorectal carcinoma (p < 0.05). Overall, 44.63% (54/121) dMMR tumors harbored KRAS mutation, however, dMMR tumors were less likely to have NRAS mutation. Moreover, dMMR, KRAS and NRAS mutation were not prognostic factors for stage I–III colorectal carcinoma.

Conclusions

This study confirms that the status of molecular markers involving mismatch repair status and RAS mutation reflects the specific clinicopathological characteristics of colorectal carcinoma.

Prognostic values of DNA mismatch repair genes in ovarian cancer patients treated with platinum-based chemotherapy

Purpose

DNA mismatch repair (MMR) is a highly conserved biological pathway that plays a key role in maintaining genomic stability. MMR has been reported as a prognostic marker in certain cancers; however, the results are controversial. Therefore, identification of the prognostic value of MMR genes in ovarian cancer based on a large sample size is pivotal.

Methods

In the current study, we systemically investigated the prognostic roles of seven MMR genes, MSH2, MSH3, MSH6, MLH1, MLH3, PMS1 and PMS2, in ovarian cancer patients treated with platinum-based chemotherapy through “The Kaplan–Meier plotter” (KM plotter) database, which contains gene expression data and survival information of ovarian cancer patients.

Results

Among seven MMR genes, high mRNA levels of MSH6, MLH1 and PMS2 were significantly associated with a better overall survival for all ovarian cancer patients treated with platinum-based chemotherapy, especially in late-stage and poor-differentiated ovarian cancer patients. Increased MSH6 and PMS2 mRNA expression was correlated with a favorable overall survival in serous ovarian cancer patients.

Conclusions

Our results indicate that sufficient MMR system is associated with an improved survival in ovarian cancer treated with platinum-based chemotherapy. MMR gene may be a potential prognosis predictor in ovarian cancer.

Characteristics of Differently Located Colorectal Cancers Support Proximal and Distal Classification: A Population-Based Study of 57,847 Patients

Background

It has been suggested that colorectal cancer be regarded as several subgroups defined according to tumor location rather than as a single entity. The current study aimed to identify the most useful method for grouping colorectal cancer by tumor location according to both baseline and survival characteristics.

Methods

Cases of pathologically confirmed colorectal adenocarcinoma diagnosed from 2000 to 2012 were identified from the Surveillance, Epidemiology, and End Results database and categorized into three groups: right colon cancer (RCC), left colon cancer (LCC), and rectal cancer (ReC). Adjusted hazard ratios for known predictors of disease-specific survival (DSS) in colorectal cancer were obtained using a Cox proportional hazards regression model.

Results

The study included 57847 patients: 43.5% with RCC, 37.7% with LCC, and 18.8% with ReC. Compared with LCC and ReC, RCC was more likely to affect old patients and women, and to be at advanced stage, poorly differentiated or un-differentiated, and mucinous. Patients with LCC or ReC had better DSS than those with RCC in subgroups including stage III or IV disease, age ≤70 years and non-mucinous adenocarcinoma. Conversely, patients with LCC or ReC had worse DSS than those with RCC in subgroups including age ˃70 years and mucinous adenocarcinoma.

Conclusions

RCC differed from both LCC and ReC in several clinicopathologic characteristics and in DSS. It seems reasonable to group colorectal cancer into right-sided (i.e., proximal) and left-sided (i.e., distal) ones.

Role of Deficient Mismatch Repair in the Personalized Management of Colorectal Cancer

Colorectal cancer (CRC) represents the third most common type of cancer in developed countries and one of the leading causes of cancer deaths worldwide. Personalized management of CRC has gained increasing attention since there are large inter-individual variations in the prognosis and response to drugs used to treat CRC owing to molecular heterogeneity. Approximately 15% of CRCs are caused by deficient mismatch repair (dMMR) characterized by microsatellite instability (MSI) phenotype. The present review is aimed at highlighting the role of MMR status in informing prognosis and personalized treatment of CRC including adjuvant chemotherapy, targeted therapy, and immune checkpoint inhibitor therapy to guide the individualized therapy of CRC.