Mismatch repair gene defects in sporadic colorectal cancers with microsatellite instability

Differential Responses to Immune Checkpoint Inhibitors are Governed by Diverse Mismatch Repair Gene Alterations

PURPOSE

The response to immune checkpoint inhibitors (ICI) in deficient mismatch repair (dMMR) colorectal cancer and endometrial cancer is variable. Here, we explored the differential response to ICIs according to different mismatch repair alterations.

EXPERIMENTAL DESIGN

Colorectal cancer (N = 13,701) and endometrial cancer (N = 3,315) specimens were tested at Caris Life Sciences. Median overall survival (mOS) was estimated using Kaplan-Meier. The prediction of high-, intermediate-, and low-affinity epitopes by tumor mutation burden (TMB) values was conducted using R-squared (R2).

RESULTS

Compared with mutL (MLH1 and PMS2) co-loss, the mOS was longer in mutS (MSH2 and MSH6) co-loss in all colorectal cancer (54.6 vs. 36 months; P = 0.0.025) and endometrial cancer (81.5 vs. 48.2 months; P < 0.001) patients. In ICI-treated patients, the mOS was longer in mutS co-loss in colorectal cancer [not reached (NR) vs. 36 months; P = 0.011). In endometrial cancer, the mOS was NR vs. 42.2 months; P = 0.711]. The neoantigen load (NAL) in mutS co-loss compared with mutL co-loss was higher in colorectal cancer (high-affinity epitopes: 25.5 vs. 19; q = 0.017, intermediate: 39 vs. 32; q = 0.004, low: 87.5 vs. 73; q < 0.001) and endometrial cancer (high-affinity epitopes: 15 vs. 11; q = 0.002, intermediate: 27.5 vs. 19; q < 0.001, low: 59 vs. 41; q < 0.001), respectively. R2 ranged from 0.25 in mutS co-loss colorectal cancer to 0.95 in mutL co-loss endometrial cancer.

CONCLUSIONS

Patients with mutS co-loss experienced longer mOS in colorectal cancer and endometrial cancer and better response to ICIs in colorectal cancer. Among all explored biomarkers, NAL was higher in mutS co-loss and may be a potential driving factor for the observed better outcomes. TMB did not reliably predict NAL.

Immune Checkpoint Inhibitors in pMMR/MSS Colorectal Cancer

BACKGROUND

Immune checkpoint inhibitors have recently replaced over chemotherapy as the first-line treatment for microsatellite instability-high or mismatch repair deficient (dMMR/MSI-H) stage 4 colorectal cancers. Considering this success, many studies have tried to replicate the use of immune checkpoint inhibitors, either as a single agent or in combination with other therapeutic agents, in the treatment of proficient mismatch repair (pMMR/MSS) stage 4 colorectal cancers. This review summarizes the seminal clinical data about the immune checkpoint inhibitors used in pMMR/MSS colorectal cancers and some future directions.

RESULTS

Studies concerning the use of immune checkpoint inhibitors as a single agent or in combination with other immune checkpoint inhibitors, targeted therapy, chemotherapy, or radiotherapy have proven inefficient in the treatment of pMMR/MSS colorectal cancer. However, a small subset of patients with pMMR/MSS colorectal cancer who has a mutation in POLE and POLD1 enzymes may respond to immunotherapy. Moreover, patients without liver metastasis appear to have a better chance of response. New immune checkpoint targets are being identified, such as VISTA, TIGIT, LAG3, STING signal pathway, and BTLA, and studies are ongoing to determine their efficiency in this disease type.

CONCLUSION

Immune checkpoint inhibitor-based regimens have not yet shown any meaningful positive outcomes for most pMMR/MSS colorectal cancers. A beneficial effect among a minority of these patients has been observed, but concrete biomarkers of response are lacking. Understanding the underlying mechanisms of immune resistance should guide further research for overcoming these obstacles.

Can immunotherapy reinforce chemotherapy efficacy? a new perspective on colorectal cancer treatment

As one of the main threats to human life (the fourth most dangerous and prevalent cancer), colorectal cancer affects many people yearly, decreases patients' quality of life, and causes irreparable financial and social damages. In addition, this type of cancer can metastasize and involve the liver in advanced stages. However, current treatments can't completely eradicate this disease. Chemotherapy and subsequent surgery can be mentioned among the current main treatments for this disease. Chemotherapy has many side effects, and regarding the treatment of this type of tumor, chemotherapy can lead to liver damage, such as steatohepatitis, steatosis, and sinus damage. These damages can eventually lead to liver failure and loss of its functions. Therefore, it seems that other treatments can be used in addition to chemotherapy to increase its efficiency and reduce its side effects. Biological therapies and immunotherapy are one of the leading suggestions for combined treatment. Antibodies (immune checkpoint blockers) and cell therapy (DC and CAR-T cells) are among the immune system-based treatments used to treat tumors. Immunotherapy targets various aspects of the tumor that may lead to 1) the recruitment of immune cells, 2) increasing the immunogenicity of tumor cells, and 3) leading to the elimination of inhibitory mechanisms established by the tumor. Therefore, immunotherapy can be used as a complementary treatment along with chemotherapy. This review will discuss different chemotherapy and immunotherapy methods for colorectal cancer. Then we will talk about the studies that have dealt with combined treatment.

Biomarkers for Predicting Response to Personalized Immunotherapy in Gastric Cancer

Despite advances in diagnostic imaging, surgical techniques, and systemic therapy, gastric cancer (GC) is the third leading cause of cancer-related death worldwide. Unfortunately, molecular heterogeneity and, consequently, acquired resistance in GC are the major causes of failure in the development of biomarker-guided targeted therapies. However, by showing promising survival benefits in some studies, the recent emergence of immunotherapy in GC has had a significant impact on treatment-selectable procedures. Immune checkpoint inhibitors (ICIs), widely indicated in the treatment of several malignancies, target inhibitory receptors on T lymphocytes, including the programmed cell death protein (PD-1)/programmed death-ligand 1 (PD-L1) axis and cytotoxic T-lymphocyte-associated protein 4 (CTLA4), and release effector T-cells from negative feedback signals. In this article, we review currently available predictive biomarkers (including PD-L1, microsatellite instability, Epstein-Barr virus, and tumor mutational burden) that affect the ICI treatment response, focusing on PD-L1 expression. We further briefly describe other potential biomarkers or mechanisms for predicting the response to ICIs in GC. This review may facilitate the expansion of the understanding of biomarkers for predicting the response to ICIs and help select the appropriate therapeutic approaches for patients with GC.

The Importance of Immunohistochemical Heterogeneous Expression of MMR Protein in Patients with Colorectal Cancer in Stage II and III of the Disease

Background and objectives: In patients with colorectal cancer (CRC), heterogeneous expression of Mismatch repair (MMR) proteins can manifest itself in several different forms and is not such a rare phenomenon. Therefore, it is very important to recognize the nuclear expression of MMR proteins of different MMR status in order to avoid false positive or false negative results. The aim of this study was to determine the frequency and distribution of heterogeneous expression of MMR proteins in patients with stages II and III of the disease as well as its association with clinical, demographic and pathological characteristics of CRC in relation to proficient and deficient expression of MMR proteins. Material and Methods: The study included 104 cases of colorectal cancer obtained from surgical colectomy material in stages II and III of the disease. Results: From a total of 104 patients with colorectal cancer, immunohistochemical analysis of the expression of all four MMR proteins showed that heterogeneous expression of MMR proteins (as well as deficient immunoreactivity of tumor cells) was present in 12 cases, while proficient expression of MMR proteins was detected in 80 tumors. Conclusions: Our study showed that the only independent predictors of the loss of MMR protein expression were younger patient age and right-sided anatomical location of the tumor. The study also established the existence of heterogeneous expression of MMR proteins in a non-negligible percentage of CRCs (11.5%), where heterogeneous nuclear expression of MMR proteins was described in several different forms.

Establish immune-related gene prognostic index for esophageal cancer

Background: Esophageal cancer is a tumor type with high invasiveness and low prognosis. As immunotherapy has been shown to improve the prognosis of esophageal cancer patients, we were interested in the establishment of an immune-associated gene prognostic index to effectively predict the prognosis of patients. Methods: To establish the immune-related gene prognostic index of esophageal cancer (EC), we screened 363 upregulated and 83 downregulated immune-related genes that were differentially expressed in EC compared to normal tissues. By multivariate Cox regression and weighted gene coexpression network analysis (WGCNA), we built a prognostic model based on eight immune-related genes (IRGs). We confirmed the prognostic model in both TCGA and GEO cohorts and found that the low-risk group had better overall survival than the high-risk group. Results: In this study, we identified 363 upregulated IRGs and 83 downregulated IRGs. Next, we found a prognostic model that was constructed with eight IRGs (OSM, CEACAM8, HSPA6, HSP90AB1, PCSK2, PLXNA1, TRIB2, and HMGB3) by multivariate Cox regression analysis and WGCNA. According to the Kaplan–Meier survival analysis results, the model we constructed can predict the prognosis of patients with esophageal cancer. This result can be verified by the Gene Expression Omnibus (GEO). Patients were divided into two groups with different outcomes. IRGPI-low patients had better overall survival than IRGPI-high patients.

Conclusion: Our findings indicated the potential value of the IRGPI risk model for predicting the prognosis of EC patients.

Colorectal cancer immunotherapy-Recent progress and future directions

Compared with conventional chemotherapy and targeted therapy, immunotherapy has changed the treatment prospects of various solid tumors and has recently become the main treatment method for metastatic or recurrent solid tumors, including malignant melanoma, non-small-cell lung cancer, and renal cell carcinoma. The application of immune checkpoint inhibitor (ICI)-based immunotherapy in patients with colorectal cancer (CRC) has yielded satisfactory results in terms of safety and efficacy, and several immunotherapeutic agents, including pembrolizumab, nivolumab, and ipilimumab, have been approved for the treatment of advanced CRC. The advent of other immunotherapies, such as chimeric antigen receptor-modified T (CAR-T) cells or cancer vaccines, have also contributed to the development of immunotherapy for CRC. Here, we summarize the findings of recent clinical trials on the efficacy of immunotherapy in CRC and briefly describe the mechanisms associated with tumor-intrinsic resistance to ICIs. We then discuss potential biomarkers for predicting the efficacy of immunotherapy.

Spectrum of DNA mismatch repair failures viewed through the lens of cancer genomics and implications for therapy

Genome sequencing can be used to detect DNA repair failures in tumors and learn about underlying mechanisms. Here, we synthesize findings from genomic studies that examined deficiencies of the DNA mismatch repair (MMR) pathway. The impairment of MMR results in genome-wide hypermutation and in the ‘microsatellite instability’ (MSI) phenotype—occurrence of indel mutations at short tandem repeat (microsatellite) loci. The MSI status of tumors was traditionally assessed by molecular testing of a selected set of MS loci or by measuring MMR protein expression levels. Today, genomic data can provide a more complete picture of the consequences on genomic instability. Multiple computational studies examined somatic mutation distributions that result from failed DNA repair pathways in tumors. These include analyzing the commonly studied trinucleotide mutational spectra of single-nucleotide variants (SNVs), as well as of other features such as indels, structural variants, mutation clusters and regional mutation rate redistribution. The identified mutation patterns can be used to rigorously measure prevalence of MMR failures across cancer types, and potentially to subcategorize the MMR deficiencies. Diverse data sources, genomic and pre-genomic, from human and from experimental models, suggest there are different ways in which MMR can fail, and/or that the cell-type or genetic background may result in different types of MMR mutational patterns. The spectrum of MMR failures may direct cancer evolution, generating particular sets of driver mutations. Moreover, MMR affects outcomes of therapy by DNA damaging drugs, antimetabolites, nonsense-mediated mRNA decay (NMD) inhibitors, and immunotherapy by promoting either resistance or sensitivity, depending on the type of therapy.

BRAF Mutations Are Associated with Poor Survival Outcomes in Advanced-stage Mismatch Repair-deficient/Microsatellite High Colorectal Cancer

Background

Mismatch repair-deficient (MMR-D)/microsatellite instability-high (MSI-H) metastatic colorectal cancer (mCRC) is a unique disease entity with growing interest given the rise of young-onset CRC. Given its heterogeneous behavior and potential for highly effective treatment outcomes, we sought to identify the clinical and molecular features that offer prognostic value for MMR-D CRC.

Materials/Methods

This was a retrospective cohort study of patients with metastatic CRC with MMR-D or microsatellite instability in a real-world database. Overall survival (OS) was determined by the date of metastatic disease to date of death with stratification made based on factors including BRAF and RAS mutation status, age, and MMR protein loss type.

Results

There were 1101 patients in the study. Patients with BRAF mutations had worse OS compared with patients with wild-type BRAF with a median survival of 18.9 months versus 33.2 months (hazard ratio [HR] 1.52, 95% confidence interval [CI]: 1.25-1.86, P < .001). Patients with age >50 were found to have decreased OS versus age ≤50 with a median survival of 21.4 months versus 38.7 months (HR 1.66, 95% CI: 1.33-2.07, P < .001). BRAF mutations and age >50 remained significant predictors of OS in multivariate analysis.

Conclusion

BRAF mutations and age >50 are associated with worse survival outcomes for patients with MMR-D mCRC. RAS mutations and specific MMR alterations are not associated with survival outcomes.

Evolutionary patterns of chromosomal instability and mismatch repair deficiency in proximal and distal colorectal cancer

AIM

Colorectal carcinomas (CRCs) progress through heterogeneous pathways. The aim of this study was to analyse whether or not the cytogenetic evolution of CRC is linked to tumour site, level of chromosomal imbalance and metastasis.

METHOD

A set of therapy-naïve pT3 CRCs comprising 26 proximal and 49 distal pT3 CRCs was studied by combining immunohistochemistry of mismatch repair (MMR) proteins, microsatellite analyses and molecular karyotyping as well as clinical parameters.

RESULTS

A MMR deficient/microsatellite-unstable (dMMR/MSI-H) status was associated with location of the primary tumour proximal to the splenic flexure, and dMMR/MSI-H tumours presented with significantly lower levels of chromosomal imbalances compared with MMR proficient/microsatellite-stable (pMMR/MSS) tumours. Oncogenetic tree modelling suggested two evolutionary clusters characterized by dMMR/MSI-H and chromosomal instability (CIN), respectively, for both proximal and distal CRCs. In CIN cases, +13q, -18q and +20q were predicted as preferentially early events, and -1p, -4 -and -5q as late events. Separate oncogenetic tree models of proximal and distal cases indicated similar early events independent of tumour site. However, in cases with high CIN defined by more than 10 copy number aberrations, loss of 17p occurred earlier in cytogenetic evolution than in cases showing low to moderate CIN. Differences in the oncogenetic trees were observed for CRCs with lymph node and distant metastasis. Loss of 8p was modelled as an early event in node-positive CRC, while +7p and +8q comprised early events in CRC with distant metastasis.

CONCLUSION

CRCs characterized by CIN follow multiple, interconnected genetic pathways in line with the basic 'Vogelgram' concept proposed for the progression of CRC that places the accumulation of genetic changes at centre of tumour evolution. However, the timing of specific genetic events may favour metastatic potential.

Human MLH1/3 variants causing aneuploidy, pregnancy loss, and premature reproductive aging

Embryonic aneuploidy from mis-segregation of chromosomes during meiosis causes pregnancy loss. Proper disjunction of homologous chromosomes requires the mismatch repair (MMR) genes MLH1 and MLH3, essential in mice for fertility. Variants in these genes can increase colorectal cancer risk, yet the reproductive impacts are unclear. To determine if MLH1/3 single nucleotide polymorphisms (SNPs) in human populations could cause reproductive abnormalities, we use computational predictions, yeast two-hybrid assays, and MMR and recombination assays in yeast, selecting nine MLH1 and MLH3 variants to model in mice via genome editing. We identify seven alleles causing reproductive defects in mice including female subfertility and male infertility. Remarkably, in females these alleles cause age-dependent decreases in litter size and increased embryo resorption, likely a consequence of fewer chiasmata that increase univalents at meiotic metaphase I. Our data suggest that hypomorphic alleles of meiotic recombination genes can predispose females to increased incidence of pregnancy loss from gamete aneuploidy.

Proper meiotic chromosome segregation requires mismatch repair genes MLH1 and MLH3, of which variants occur in the human population. Here, the authors use computational predictions and yeast assays to select human MLH1/3 variants for modelling in mice, observing reproductive defects from abnormal levels of crossing over.

Mismatch Repair (MMR) Gene Alteration and BRAF V600E Mutation Are Potential Predictive Biomarkers of Immune Checkpoint Inhibitors in MMR-Deficient Colorectal Cancer

BACKGROUND

Immune checkpoint inhibitor (ICI) therapy is highly effective in metastatic mismatch repair-deficient (MMR-D) colorectal cancer (CRC). In this study, we evaluated molecular and clinical predictors of ICI response in MMR-D CRC.

MATERIALS AND METHODS

Patient databases at four cancer institutions were queried. The Fisher exact test was performed to test the association of clinical and molecular markers. The Kaplan-Meier method was used to estimate progression-free survival (PFS) and compared by the log-rank test. Twelve- and 24-month PFS rates were compared by the Z test.

RESULTS

A total of 60 patients with CRC with MMR-D/microsatellite instability-high who previously received ICIs were identified. Patients with liver metastasis had a lower overall response rate as compared with other sites of metastasis (36.4% vs. 68.7%; p = .081). Patients with MLH1/PMS2 loss had worse 1-year and 2-year PFS rates compared with patients with MSH2/MSH6 loss (84.2% vs. 57.8% and 78.2% vs. 54.2%, respectively; p < .001). There were improved 1-year and 2-year PFS rates in patients with wild-type BRAF when compared with patients with BRAF V600E mutation (73.3% vs. 40%, and 73.3% vs. 26.7%; respectively; p < .001). Patients aged >65 had significantly worse PFS rates as compared with patients aged ≤65 (p < .001).

CONCLUSION

BRAF V600E mutation, MLH1 and/or PMS2 loss, as well as age >65 years and liver metastasis, may be predictive of duration of ICI response in patients with MMR-D CRC. Larger cohorts are needed to confirm our findings.

IMPLICATIONS FOR PRACTICE

The results of this study reveal clinically important biomarkers that potentially predict immune checkpoint inhibitor response in patients with mismatch repair-deficient colorectal cancer.

Defining the current role of immune checkpoint inhibitors in the treatment of mismatch repair-deficient/microsatellite stability-high colorectal cancer and shedding light on future approaches

Introduction: Mismatch repair deficient (MMR-D)/microsatellite instability-high (MSI-H) colorectal cancer (CRC) carries unique biologic features including high tumor mutation burden, increased amount of mutation-associated neoantigen generation, and the presence of marked tumor-infiltrating lymphocytes. Immune checkpoint inhibitor (ICI) therapy has rapidly changed the treatment algorithm of MMR-D/MSI-H CRC.Areas covered: In this review article, we discuss the recent data regarding the use of ICIs in metastatic MMR-D/MSI-H CRC patients. We also elaborated on potential biomarkers of ICI response and innovative therapeutic approaches that may prevail resistance mechanisms for the treatment of MMR-D/MSI-H colorectal cancer.Expert opinion: Pembrolizumab was recently granted approval by the FDA as first-line therapy for metastatic MMR-D/MSI-H CRC based on the results of the Keynote 177 study. The combination of nivolumab and ipilimumab will also likely be a choice for the initial therapy of MMR-D/MSI-H CRC in the near future. More therapeutic modalities with novel immunomodulatory agents as well as targeted therapy directed to immune resistance pathways are needed. The novel approaches discussed in this review article will define potential treatment options for the management of MMR-D/MSI-H CRC patients who progress on first-line ICI therapy.

Chlamydia Trachomatis Infection: Their potential implication in the Etiology of Cervical Cancer

Pathogenic bacterial strains can alter the normal function of cells and induce different levels of inflammatory responses that are connected to the development of different diseases, such as tuberculosis, diarrhea, cancer etc. Chlamydia trachomatis (C. trachomatis) is an intracellular obligate gram-negative bacterium which has been connected with the cervical cancer etiology. Nevertheless, establishment of causality and the underlying mechanisms of carcinogenesis of cervical cancer associated with C. trachomatis remain unclear. Studies reveal the existence of C. trachomatis in cervical cancer patients. The DNA repair pathways including mismatch repair, nucleotide excision, and base excision are vital in the abatement of accumulated mutations that can direct to the process of carcinogenesis. C. trachomatis recruits DDR proteins away from sites of DNA damage and, in this way, impedes the DDR. Therefore, by disturbing host cell-cycle control, chromatin and DDR repair, C. trachomatis makes a situation favorable for malignant transformation. Inflammation originated due to infection directs over production of reactive oxygen species (ROS) and consequent oxidative DNA damage. This review may aid our current understanding of the etiology of cervical cancer in C. trachomatis-infected patients.

Epigenetic Regulation of Intestinal Stem Cells and Disease: A Balancing Act of DNA and Histone Methylation

Genetic mutations or regulatory failures underlie cellular malfunction in many diseases, including colorectal cancer and inflammatory bowel diseases. However, mutational defects alone fail to explain the complexity of such disorders. Epigenetic regulation-control of gene action through chemical and structural changes of chromatin-provides a platform to integrate multiple extracellular inputs and prepares the cellular genome for appropriate gene expression responses. Coregulation by polycomb repressive complex 2-mediated trimethylation of lysine 27 on histone 3 and DNA methylation has emerged as one of the most influential epigenetic controls in colorectal cancer and many other diseases, but molecular details remain inadequate. Here we review the molecular interplay of these epigenetic features in relation to gastrointestinal development, homeostasis, and disease biology. We discuss other epigenetic mechanisms pertinent to the balance of trimethylation of lysine 27 on histone 3 and DNA methylation and their actions in gastrointestinal cancers. We also review the current molecular understanding of chromatin control in the pathogenesis of inflammatory bowel diseases.

Genomic and immunological features of microsatellite instability in colon cancer

Microsatellite instability (MSI) is closely related to the prognosis and therapy response of colon cancer. Colon cancer patients with MSI show resistance to 5-Fluorouracil (5-FU) but sensitivity to immunosuppressive checkpoint inhibitors (ICIs). The relevant mechanism behind the opposite response remains unclear. Multi-omics research data of colon cancer patients were acquired from The Cancer Genome Atlas (TCGA) database, GEO database, and DAFI dataset. Transcriptome data were normalized to gene expression data through the R software package "Limma". Somatic mutations data were analyzed and visualized through the R software package "maftools". CIBERSORT algorithm was used to estimate the relative proportion of 22 infiltrating immune cell types. We demonstrated MSI patients showed both overexpressed immune checkpoints (mRNA level) and activated tumor-infiltrating lymphocytes (TILs), which may explain the satisfying response of ICIs. The additionally, we also demonstrated MSI promoted the mRNA expression of thymidylate synthase (TYMS) through regulating its copy number variation. As a main target of 5-FU, overexpressed TYMS promoted the resistance of 5-FU. Furthermore, we demonstrated MSI patients showed significantly increased somatic mutations compared with microsatellite stability (MSS) patients, except APC, TP53, and KRAS mutations. The substitutions and location of somatic mutations in different genes were at variance between MSS and MSI patients. In conclusion, our research determined mechanisms of MSI associated treatment response, and may provide potential value for improving the survival of colon cancer patients.

A Roadmap Toward the Definition of Actionable Tumor-Specific Antigens

The search for tumor-specific antigens (TSAs) has considerably accelerated during the past decade due to the improvement of proteogenomic detection methods. This provides new opportunities for the development of novel antitumoral immunotherapies to mount an efficient T cell response against one or multiple types of tumors. While the identification of mutated antigens originating from coding exons has provided relatively few TSA candidates, the possibility of enlarging the repertoire of targetable TSAs by looking at antigens arising from non-canonical open reading frames opens up interesting avenues for cancer immunotherapy. In this review, we outline the potential sources of TSAs and the mechanisms responsible for their expression strictly in cancer cells. In line with the heterogeneity of cancer, we propose that discrete families of TSAs may be enriched in specific cancer types.

Bacteria-related changes in host DNA methylation and the risk for CRC

Colorectal cancer (CRC) is the second most common cause of cancer deaths in men and women combined. Colon-tumor growth is multistage and the result of the accumulation of spontaneous mutations and epigenetic events that silence tumor-suppressor genes and activate oncogenes. Environmental factors are primary contributors to these somatic gene alterations, which account for the increase in incidence of CRC in western countries. In recent decades, gut microbiota and their metabolites have been recognized as essential contributing factors to CRC, and now serve as biomarkers for the diagnosis and prognosis of CRC. In the present review, we highlight holistic approaches to understanding how gut microbiota contributes to CRC. We particularly focus herein on bacteria-related changes in host DNA methylation and the risk for CRC.

DNA Mismatch Repair Gene Variants in Sporadic Solid Cancers

The phenotypic effects of single nucleotide polymorphisms (SNPs) in the development of sporadic solid cancers are still scarce. The aim of this review was to summarise and analyse published data on the associations between SNPs in mismatch repair genes and various cancers. The mismatch repair system plays a unique role in the control of the genetic integrity and it is often inactivated (germline and somatic mutations and hypermethylation) in cancer patients. Here, we focused on germline variants in mismatch repair genes and found the outcomes rather controversial: some SNPs are sometimes ascribed as protective, while other studies reported their pathological effects. Regarding the complexity of cancer as one disease, we attempted to ascertain if particular polymorphisms exert the effect in the same direction in the development and treatment of different malignancies, although it is still not straightforward to conclude whether polymorphisms always play a clear positive role or a negative one. Most recent and robust genome-wide studies suggest that risk of cancer is modulated by variants in mismatch repair genes, for example in colorectal cancer. Our study shows that rs1800734 in MLH1 or rs2303428 in MSH2 may influence the development of different malignancies. The lack of functional studies on many DNA mismatch repair SNPs as well as their interactions are not explored yet. Notably, the concerted action of more variants in one individual may be protective or harmful. Further, complex interactions of DNA mismatch repair variations with both the environment and microenvironment in the cancer pathogenesis will deserve further attention.

High EREG Expression Is Predictive of Better Outcomes in Rectal Cancer Patients Receiving Neoadjuvant Concurrent Chemoradiotherapy

BACKGROUND/AIM

A great proportion of patients with rectal cancer initially present with locally advanced disease and can potentially benefit from neoadjuvant concurrent chemoradiotherapy (CCRT) for downstaging before surgery. However, risk and clinical outcome stratification remain a great challenge. We aimed to find the potential biomarker to predict the effect of neoadjuvant CCRT on rectal cancer.

METHODS

We identified epiregulin (EREG) as the most significant predictive marker for neoadjuvant CCRT response from the published rectal cancer transcriptome data set GSE35452. We collected 172 biopsy specimens from rectal cancer patients who received neoadjuvant CCRT followed by radical proctectomy, performed EREG immunohistochemistry, and analyzed the H-scores. We further examined the correlations between the expression level of EREG and clinicopathological features, tumor regression grade, and survival, including disease-specific survival (DSS), locoregional recurrence-free survival (LRFS), and metastasis-free survival (MeFS).

RESULTS

High EREG expression was significantly related to early pretreatment (pre-Tx) and posttreatment (post-Tx) tumor status (T1, T2, p = 0.047 and p < 0.001), pre-Tx and post-Tx negative nodal status (N0, p < 0.001 and p = 0.004), less vascular and perineurial invasion (p = 0.015 and p = 0.023), and higher tumor regression grade (p < 0.001). In the survival analysis, high EREG expression was significantly associated with better DSS (p < 0.0001), LRFS (p = 0.0004), and MeFS (p < 0.0001). In the multivariate analysis, high EREG expression remained prognostically significant for better DSS (p = 0.003; hazard ratio: 5.599).

CONCLUSION

These data suggest that EREG is a potential predictive marker and therapeutic target in rectal cancer patients receiving neoadjuvant CCRT.

Limiting oxidative DNA damage reduces microbe-induced colitis-associated colorectal cancer

Inflammatory bowel disease patients have a greatly increased risk of developing colitis-associated colon cancer (CAC); however, the basis for inflammation-induced genetic damage requisite for neoplasia is unclear. Using three models of CAC, we find that sustained inflammation triggers 8-oxoguanine DNA lesions. Strikingly, antioxidants or iNOS inhibitors reduce 8-oxoguanine and polyps in CAC models. Because the mismatch repair (MMR) system repairs 8-oxoguanine and is frequently defective in colorectal cancer (CRC), we test whether 8-oxoguanine mediates oncogenesis in a Lynch syndrome (MMR-deficient) model. We show that microbiota generates an accumulation of 8-oxoguanine lesions in MMR-deficient colons. Accordingly, we find that 8-oxoguanine is elevated in neoplastic tissue of Lynch syndrome patients compared to matched untransformed tissue or non-Lynch syndrome neoplastic tissue. While antioxidants reduce 8-oxoguanine, they do not reduce CRC in Lynch syndrome models. Hence, microbe-induced oxidative/nitrosative DNA damage play causative roles in inflammatory CRC models, but not in Lynch syndrome models.

It is unclear how microbial-induced inflammation promotes neoplastic transformation in colitis-associated cancer (CAC). Here, the authors use models of CAC to show that inflammation induces 8-oxoguanine lesions in DNA, and that antioxidants can reduce these DNA lesions as well as CAC.

Update on optimal treatment for metastatic colorectal cancer from the AGITG expert meeting: ESMO congress 2019

Introduction: Outcomes in metastatic colorectal cancer are improving, due to the tailoring of therapy enabled by better understanding of clinical behavior according to molecular subtype.Areas covered: A review of the literature and recent conference presentations was undertaken on the topic of systemic treatment of metastatic colorectal cancer. This review summarizes expert discussion of the current evidence for therapies in metastatic colorectal cancer (mCRC) based on molecular subgrouping.Expert opinion: EGFR-targeted and VEGF-targeted antibodies are now routinely incorporated into treatment strategies for mCRC. EGFR-targeted antibodies are restricted to patients with extended RAS wild-type profiles, with evidence that they should be further restricted to patients with left-sided tumors. Clinically distinct treatment pathways based on tumor RAS, BRAF, HER2 and MMR status, are now clinically applicable. Evidence suggests therapy for additional subgroups will soon be defined; the most advanced being for patients with KRAS G12 C mutation and gene TRK fusion defects.

Safety and Efficacy of Immune Checkpoint Inhibitors in Patients With Cancer Living With HIV: A Perspective on Recent Progress and Future Needs

Recent studies have identified durable responses with the use of immune checkpoint inhibitors in patients with mismatch repair-deficient (MMR-D)/microsatellite instability-high (MSI-H) metastatic colorectal cancer (CRC). The dramatic improvement in clinical outcomes led to the US Food and Drug Administration approval of pembrolizumab, nivolumab, and nivolumab in combination with ipilimumab in metastatic patients with MSI-H/MMR-D CRC who previously experienced progression on cytotoxic therapies. In the clinical trials investigating these agents, HIV-seropositive patients were not included and therefore the clinical efficacy of these agents in patients with metastatic MSI-H/MMR-D CRC living with HIV is unclear. On the basis of growing evidence, immune checkpoint blockade therapies seem to be a safe approach in patients with well-controlled HIV infection. Research on immunotherapeutic approaches in patients living with HIV and cancer is an area of unmet medical need that can be addressed by clinical trial designs that are inclusive of patients with well-controlled seropositive HIV and trials that specifically evaluate immune therapies in patients living with HIV.

Prognostic and therapeutic molecular markers in the clinical management of esophageal cancer

Introduction: Esophageal cancer is a deadly disease with high mortality. Treatment with chemotherapy, radiation, and surgery continues to leave many patients with disease progression and recurrence. Novel treatments are needed for this patient population. The development of molecular markers are important for identifying therapeutic targets, as well as prognosis.Areas covered: This review evaluates three molecular markers in esophageal cancer: HER2, PD-L1, and MSI. The fundamentals of these markers, diagnosis, and rates of occurrence in esophageal cancer are explored. The prognostic potential of these markers is based on existing literature as well as application in clinical trials. Key trial findings pertaining to the therapeutic targets for HER2 and PD-1 as well as the role of MSI are discussed.Expert commentary: Molecular markers are changing the practice for esophageal cancer. Therapeutic targeting for HER2 and PD-L1 have shown positive results in recent clinical trials. Trials evaluating immunotherapy as first-line agents are currently underway.

Colon Cancer: A Clinician's Perspective in 2019

Colon cancer is a common preventable cancer. With the adoption of widespread colon cancer screening in the developed countries, the incidence and mortality of colon cancer have decreased in the targeted population. But unfortunately, the incidence and mortality of colorectal cancer (CRC) have been increasing over the last 25 years in the young adults below the age of 50. There is disparity in benefit, i.e. reduction in risk of death between right-sided and left-sided colon cancer by screening colonoscopy. The reason could be multifactorial and various measures have been taken to decrease this disparity. Although most of the screened populations are average risk individuals, a minority of the population have various risk factors for developing colon cancer and need to follow specific colon cancer screening guidelines. Gene mutations (adenomatous polyposis coli (APC), deleted in colon cancer (DCC), K-ras, p53, B-Raf proto-oncogene serine/threonine kinase (BRAF), mismatch repair genes) and microsatellite instability lead to the development of colon cancer. Although various non-invasive methods of colon cancer screening are now available, colonoscopy remains the gold standard of colon cancer screening and adenoma detection rate is now being used as the quality metrics in screening colonoscopy. Although Multi-Society Task Force (MSTF) and American College of Physicians (ACP) recommend initiating screening colonoscopy at age 50 years in all individuals except African Americans who should begin screening colonoscopy at age 45 years, the American Cancer Society (ACS) recommends initiating screening colonoscopy at age 45 years in all individuals irrespective of race and ethnicity. Low-volume split-dose prep has been found to be as effective as high-volume split-dose prep and more tolerable to patients with increased compliance. Boston bowel preparation scale is recommended to measure the quality of colon cleansing. CRC is curative if it is diagnosed at an early stage but various palliative treatment options (endoscopic, oncologic and surgical) are available in advanced stages of this cancer. Adequate number of lymph node assessment during surgery is essential in accurate staging of CRC. Checkpoint inhibitors have been found to have dramatic response and durable clinical benefit in dMMR/MSI-H metastatic CRC. Different genetic and immune-oncologic research trials are ongoing for early detection and better management of CRC.

Immune checkpoint inhibitors for the treatment of MSI-H/MMR-D colorectal cancer and a perspective on resistance mechanisms

Metastatic colorectal cancer (CRC) with a mismatch repair-deficiency (MMR-D)/microsatellite instability-high (MSI-H) phenotype carries unique characteristics such as increased tumour mutational burden and tumour-infiltrating lymphocytes. Studies have shown a sustained clinical response to immune checkpoint inhibitors with dramatic clinical improvement in patients with MSI-H/MMR-D CRC. However, the observed response rates range between 30% and 50% suggesting the existence of intrinsic resistance mechanisms. Moreover, disease progression after an initial positive response to immune checkpoint inhibitor treatment points to acquired resistance mechanisms. In this review article, we discuss the clinical trials that established the efficacy of immune checkpoint inhibitors in patients with MSI-H/MMR-D CRC, consider biomarkers of the immune response and elaborate on potential mechanisms related to intrinsic and acquired resistance. We also provide a perspective on possible future therapeutic approaches that might improve clinical outcomes, particularly in patients with actionable resistance mechanisms.

Precision medicine for metastatic colorectal cancer: an evolving era

Introduction: Metastatic colorectal cancer (CRC) remains a dilemma for cancer researchers with an increasing incidence in the younger patient population. Until the last decade, limited therapeutic options were available for metastatic CRC patients leading to relatively poor clinical outcomes.Areas covered: With advances in genome sequencing technology and reductions in the cost of next-generation sequencing, molecular profiling has become more accessible for cancer researchers and clinical investigators, which has furthered our understanding of the molecular behavior of CRC. This progress has recently translated into significant advances in molecular-based therapeutics and led to the development of new target-specific agents in metastatic CRC patients. In this review article, we extensively elaborate on genomic alterations seen in CRC patients including, but not limited to, EGFR, MMR, BRAF, HER2, NTRKs, FGFR, BRCA1/2, PALB2, POLE, and POLD1 genes, all of which are potentially actionable by either an FDA-approved agent or in a clinical trial setting.Expert opinion: We strongly recommend molecular profiling in metastatic CRC patients during the early course of their disease, as this may provide therapeutic and prognostic information that can guide clinicians to practice precision medicine. Patients with potentially actionable genes should be considered for targeting agents based on molecular alterations.

Dna Methylation in Esophageal Diseases Including Cancer: Special Reference to hMLH1 Gene Promoter Status

Aims and Background

Chronic inflammation leading to malignancy in the esophagus may be due to errors in mismatch repair (MMR) genes such as hMLH1. Promoter hypermethylation has been suggested as the main cause of hMLH1 silencing. In this study we assessed hMLH1 promoter hypermethylation in a range of esophageal diseases. Further, we evaluated the role of factors affecting the methylation cycle: (1) methyt-enetetrahydrofolate reductase (MTHFR) C677T mutation and (2) serum homocysteine levels.

Methods

We endoscopically and histologically categorized 124 paired tissue and blood samples from patients into cancer, precancer, reflux esophagitis, other inflammatory esophagitis and controls (endoscopically normal). Restriction enzyme-based methylation analysis was carried out to assess hMLH1 promoter hypermethylation.

Results and Conclusions

hMLH1 promoter hypermethylation in tissue was seen in 63.5% of patients with cancer and 53.8% of those with precancer, which was significantly increased when compared with controls (P <0.001). There appears to be an increasing degree of hMLH1 hypermethylation with disease progression. Patients with gastroesophageal reflux disease (GERD) showed a high degree of hMLH1 hypermethylation (88.8%), indicating that local environment due to reflux may be promoting hypermethylation. We suggest that GERD is a progressive condition with an increased risk for developing into cancer. Only 14.5% of cases exhibited hypermethylation both in tissue and blood. Hence, we conclude that hMLH1 promoter hypermethylation is a tissue-specific change in the esophagus and blood testing cannot be used as a noninvasive tool to assess it. DNA methylation is dependent on the methylation cycle; MTHFR is a major enzyme in this pathway. MTHFR mutations did not correlate with hypermethylation or clinical pathology (P >0.5). Elevated homocysteine levels, independent of MTHFR mutation, correlated significantly with hMLH1 hypermethylation in tissue (P <0.005). Our study shows that hMLH1 hypermethylation in tissue may be the primary event caused by endogenous/exogenous factors in esophageal diseases, aiding disease progression.

Exome-wide analysis of bi-allelic alterations identifies a Lynch phenotype in The Cancer Genome Atlas

BACKGROUND

Cancer susceptibility germline variants generally require somatic alteration of the remaining allele to drive oncogenesis and, in some cases, tumor mutational profiles. Whether combined germline and somatic bi-allelic alterations are universally required for germline variation to influence tumor mutational profile is unclear. Here, we performed an exome-wide analysis of the frequency and functional effect of bi-allelic alterations in The Cancer Genome Atlas (TCGA).

METHODS

We integrated germline variant, somatic mutation, somatic methylation, and somatic copy number loss data from 7790 individuals from TCGA to identify germline and somatic bi-allelic alterations in all coding genes. We used linear models to test for association between mono- and bi-allelic alterations and somatic microsatellite instability (MSI) and somatic mutational signatures.

RESULTS

We discovered significant enrichment of bi-allelic alterations in mismatch repair (MMR) genes and identified six bi-allelic carriers with elevated MSI, consistent with Lynch syndrome. In contrast, we find little evidence of an effect of mono-allelic germline variation on MSI. Using MSI burden and bi-allelic alteration status, we reclassify two variants of unknown significance in MSH6 as potentially pathogenic for Lynch syndrome. Extending our analysis of MSI to a set of 127 DNA damage repair (DDR) genes, we identified a novel association between methylation of SHPRH and MSI burden.

CONCLUSIONS

We find that bi-allelic alterations are infrequent in TCGA but most frequently occur in BRCA1/2 and MMR genes. Our results support the idea that bi-allelic alteration is required for germline variation to influence tumor mutational profile. Overall, we demonstrate that integrating germline, somatic, and epigenetic alterations provides new understanding of somatic mutational profiles.

Targeted therapy for metastatic colorectal cancer

INTRODUCTION

Outcomes in metastatic colorectal cancer are improving, with better understanding and use of targeted therapies. Areas covered: A review of the literature and recent conference presentations was undertaken on the topic of systemic treatment of metastatic colorectal cancer. This article reviews the current evidence for targeted therapies in advanced colorectal cancer, including up-to-date data regarding anti-epidermal growth factor receptor (EGFR) and anti-vascular endothelial growth factor (VEGF) agents, the relevance of primary tumor location and novel subgroups such as BRAF mutated, HER2 amplified, and mismatch-repair-deficient cancers. Expert commentary: EGFR-targeted and VEGF-targeted antibodies are now routinely incorporated into treatment strategies for metastatic colorectal cancer (mCRC). The use of EGFR-targeted antibodies should be restricted to patients with extended RAS wild-type profiles, and there is evidence that they should be further restricted to patients with left-sided tumors. Clinically, mCRC can be divided into subgroups based on RAS, BRAF, HER2, and MMR status, each of which have distinct treatment pathways.

The Roles of DNA Methylation in the Stages of Cancer

Next year will mark 60 years since Dr. Leslie Foulds outlined his hypothesis that cancer is "a dynamic process advancing through stages that are qualitatively different," leading the way to our view of cancer progression as we know it today. Our understanding of the mechanisms of these stages has been continuously evolving this past half-century, and there has always been an active discussion of the roles of both genetic and epigenetic changes in directing this progression. In this review, we focus on the roles one particular epigenetic mark-DNA methylation-plays in these various "discontinuous" stages of cancer. Understanding these steps not only gives us a better picture of how this fascinating biological process operates, but also opens the doors to new prognostic biomarkers and therapies against these malignancies.

Molecular Genetics of Hereditary Non-Polyposis Colorectal Cancer (HNPCC)

The story of the molecular genetics of HNPCC is one of astonishingly rapid achievements. In just 16 months, from May 1993 to September 1994, four different genes, namely hMSH2, hMLH1, hPMS1 and hPMS2 have been identified and demonstrated to be associated with the disease. Their cloning was facilitated by the finding that tumor cells in HNPCC patients display a hypermutability of DNA short tandem repeats (microsatellite instability). In fact, HNPCC associated genes are the human counterparts of genetic elements known to control the fidelity of DNA replication in lower organisms. So far, more than 50 germline mutations of hMSH2 and hMLH1 genes have been reported in HNPCC kindreds. In addition, somatic mutations have been documented in hereditary as well as sporadic cancers. Unfortunately, the molecular diagnosis of HNPCC is hampered by the lack of mutational “hot spots” and of clearly defined genotype-phenotype correlations and different screening methods are to be employed for the analysis of affected and at-risk individuals.

Descriptive Epidemiology of Hereditary Non-Polyposis Colorectal Cancer

Hereditary non-polyposis colorectal cancer (HNPCC or Lynch syndrome) is characterized by early occurrence of colorectal malignancies, localization of tumors in the proximal colon, frequency of multiple primaries (both synchronous and metachronous) and an autosomal dominant type of genetic transmission. HNPCC has been reported in many races and populations, including Japanese, Philipinos and American Indians. The frequency of the disease ranges between 1 and 5% of all colorectal malignancies. In northern Italy, the frequency of HNPCC has been estimated in the order of 2.8-3.0% of all registered cancers of the large bowel, while lower estimates have been recorded in southern regions. The identification of HNPCC remains difficult, mainly because the full-blown syndrome does not become manifest until several family members are affected with cancer. The recent identification of at least four genes responsible, when mutated, for the clinical spectrum of Lynch syndrome should be of considerable help in recognizing this type of tumors in the general population.

Genetic Epidemiology of Colorectal Cancer

Starting from a survey of the studies on familial aggregation of colorectal cancer, we introduce the aims of genetic epidemiology. One of its main goals is to assess population frequency of cancer susceptibility genes and to determine the age-specific risks for carriers with respect to non-carriers. In section two, segregation analysis investigations are reviewed, and inferences on the relevance of genetic components of susceptibility to colorectal cancer are drawn. In section three, the HNPCC paradigm is discussed in the light of the Knudson model of tumorigenesis and recent advances of molecular research. In the last section we show an example of genotype/environment interaction in the etiology of a particular cancer and present a conceptual framework for studies on cancer genetic epidemiology in terms of attributable and relative risk.

Molecular Biomarkers for the Evaluation of Colorectal Cancer: Guideline From the American Society for Clinical Pathology, College of American Pathologists, Association for Molecular Pathology, and American Society of Clinical Oncology

OBJECTIVES

- To develop evidence-based guideline recommendations through a systematic review of the literature to establish standard molecular biomarker testing of colorectal cancer (CRC) tissues to guide epidermal growth factor receptor (EGFR) therapies and conventional chemotherapy regimens.

METHODS

- The American Society for Clinical Pathology, College of American Pathologists, Association for Molecular Pathology, and American Society of Clinical Oncology convened an expert panel to develop an evidence-based guideline to establish standard molecular biomarker testing and guide therapies for patients with CRC. A comprehensive literature search that included more than 4,000 articles was conducted.

RESULTS

- Twenty-one guideline statements were established.

CONCLUSIONS

- Evidence supports mutational testing for EGFR signaling pathway genes, since they provide clinically actionable information as negative predictors of benefit to anti-EGFR monoclonal antibody therapies for targeted therapy of CRC. Mutations in several of the biomarkers have clear prognostic value. Laboratory approaches to operationalize CRC molecular testing are presented.

Pan-cancer analysis distinguishes transcriptional changes of aneuploidy from proliferation

Patterns of gene expression in tumors can arise as a consequence of or result in genomic instability, characterized by the accumulation of somatic copy number alterations (SCNAs) and point mutations (PMs). Expression signatures have been widely used as markers for genomic instability, and both SCNAs and PMs could be thought to associate with distinct signatures given their different formation mechanisms. Here we test this notion by systematically investigating SCNA, PM, and transcriptome data from 2660 cancer patients representing 11 tumor types. Notably, our data indicate that similar expression signatures can be derived from correlating gene expression with either SCNA or PM load. Gene sets related to cell growth and proliferation generally associated positively, and immunoregulatory gene sets negatively, with variant burden. In-depth analyses revealed several genes whose de-regulation correlates with SCNA but not with PM burden, yielding downstream effectors of TP53 and MYC signaling unique to high-SCNA tumors. We compared our findings to expression changes observed in two different cancer mouse models with persistent mitotic chromosomal instability, observing a decrease in proliferative expression signatures. Our results suggest that overexpression of cell-cycle-related genes are a characteristic of proliferation, and likely tumor evolution, rather than ongoing genomic instability.

Molecular Biomarkers for the Evaluation of Colorectal Cancer

Objectives: To develop evidence-based guideline recommendations through a systematic review of the literature to establish standard molecular biomarker testing of colorectal cancer (CRC) tissues to guide epidermal growth factor receptor (EGFR) therapies and conventional chemotherapy regimens. Methods: The American Society for Clinical Pathology, College of American Pathologists, Association for Molecular Pathology, and American Society of Clinical Oncology convened an expert panel to develop an evidence-based guideline to establish standard molecular biomarker testing and guide therapies for patients with CRC. A comprehensive literature search that included more than 4,000 articles was conducted. Results: Twenty-one guideline statements were established. Conclusions: Evidence supports mutational testing for EGFR signaling pathway genes, since they provide clinically actionable information as negative predictors of benefit to anti-EGFR monoclonal antibody therapies for targeted therapy of CRC. Mutations in several of the biomarkers have clear prognostic value. Laboratory approaches to operationalize CRC molecular testing are presented.

Molecular Biomarkers for the Evaluation of Colorectal Cancer: Guideline From the American Society for Clinical Pathology, College of American Pathologists, Association for Molecular Pathology, and American Society of Clinical Oncology

OBJECTIVES

To develop evidence-based guideline recommendations through a systematic review of the literature to establish standard molecular biomarker testing of colorectal cancer (CRC) tissues to guide epidermal growth factor receptor (EGFR) therapies and conventional chemotherapy regimens.

METHODS

The American Society for Clinical Pathology, College of American Pathologists, Association for Molecular Pathology, and American Society of Clinical Oncology convened an expert panel to develop an evidence-based guideline to establish standard molecular biomarker testing and guide therapies for patients with CRC. A comprehensive literature search that included more than 4,000 articles was conducted.

RESULTS

Twenty-one guideline statements were established.

CONCLUSIONS

Evidence supports mutational testing for EGFR signaling pathway genes, since they provide clinically actionable information as negative predictors of benefit to anti-EGFR monoclonal antibody therapies for targeted therapy of CRC. Mutations in several of the biomarkers have clear prognostic value. Laboratory approaches to operationalize CRC molecular testing are presented. Key Words: Molecular diagnostics; Gastrointestinal; Histology; Genetics; Oncology.

Molecular Biomarkers for the Evaluation of Colorectal Cancer: Guideline From the American Society for Clinical Pathology, College of American Pathologists, Association for Molecular Pathology, and the American Society of Clinical Oncology

Purpose Molecular testing of colorectal cancers (CRCs) to improve patient care and outcomes of targeted and conventional therapies has been the center of many recent studies, including clinical trials. Evidence-based recommendations for the molecular testing of CRC tissues to guide epidermal growth factor receptor (EGFR) -targeted therapies and conventional chemotherapy regimens are warranted in clinical practice. The purpose of this guideline is to develop evidence-based recommendations to help establish standard molecular biomarker testing for CRC through a systematic review of the literature. Methods The American Society for Clinical Pathology (ASCP), College of American Pathologists (CAP), Association for Molecular Pathology (AMP), and the American Society of Clinical Oncology (ASCO) convened an Expert Panel to develop an evidence-based guideline to help establish standard molecular biomarker testing, guide targeted therapies, and advance personalized care for patients with CRC. A comprehensive literature search that included over 4,000 articles was conducted to gather data to inform this guideline. Results Twenty-one guideline statements (eight recommendations, 10 expert consensus opinions and three no recommendations) were established. Recommendations Evidence supports mutational testing for genes in the EGFR signaling pathway, since they provide clinically actionable information as negative predictors of benefit to anti-EGFR monoclonal antibody therapies for targeted therapy of CRC. Mutations in several of the biomarkers have clear prognostic value. Laboratory approaches to operationalize molecular testing for predictive and prognostic molecular biomarkers involve selection of assays, type of specimens to be tested, timing of ordering of tests and turnaround time for testing results. Additional information is available at: www.asco.org/CRC-markers-guideline and www.asco.org/guidelineswiki.

Expression and promoter DNA methylation of MLH1 in colorectal cancer and lung cancer

AIMS

Aberrant DNA methylation is a common molecular feature in human cancer. The aims of this study were to analyze the methylation status of MLH1, one of the DNA mismatch repair (MMR) genes, in human colorectal and lung cancer and to evaluate its clinical relevance.

METHODS

The expression of MLH1 was analyzed in 8 colorectal cancer (CRC) and 8 lung cancer cell lines by real-time RT-PCR and western blotting. The MLH1 protein expression was evaluated by immunohistochemistry on tissue microarrays including 121 primary CRC and 90 lung cancer patient samples. In cancer cell lines, the methylation status of MLH1 promoter and exon 2 was investigated by bisulfite sequencing (BS). Methylation-specific-PCR (MSP) was used to evaluate methylation status of MLH1.

RESULTS

The expression of MLH1 mRNA was detected in 8 CRC cell lines as well as normal colonic fibroblast cells CCD-33Co. At protein levels, MLH1 was lost in one CRC cell line HCT-116 and normal cells CCD-33Co. No methylation was found in the promoter and exon 2 of MLH1 in CRC cell lines. MLH1 was expressed in 8 lung cancer cell lines at both mRNA and protein levels. Compared to cancer cells, normal bronchial epithelial cells (HBEC) had lower expression of MLH1 protein. In primary CRC, 54.5% of cases exhibited positive staining, while 47.8% of lung tumors were positive for MLH1 protein. MSP analysis showed that 58 out of 92 (63.0%) CRC and 41 out of 73 (56.2%) lung cancer exhibited MLH1 methylation. In CRC, the MLH1 methylation was significantly associated with tumor invasion in veins (P=0.012). However, no significant links were found between MLH1 expression and promoter methylation in both tumor entities.

CONCLUSIONS

MLH1 methylation is a frequent molecular event in CRC and lung cancer patients. In CRC, methylation of MLH1 could be linked to vascular invasiveness.

Regulation of DNA Alkylation Damage Repair: Lessons and Therapeutic Opportunities

Alkylation chemotherapy is one of the most widely used systemic therapies for cancer. While somewhat effective, clinical responses and toxicities of these agents are highly variable. A major contributing factor for this variability is the numerous distinct lesions that are created upon alkylation damage. These adducts activate multiple repair pathways. There is mounting evidence that the individual pathways function cooperatively, suggesting that coordinated regulation of alkylation repair is critical to prevent toxicity. Furthermore, some alkylating agents produce adducts that overlap with newly discovered methylation marks, making it difficult to distinguish between bona fide damaged bases and so-called 'epigenetic' adducts. Here, we discuss new efforts aimed at deciphering the mechanisms that regulate these repair pathways, emphasizing their implications for cancer chemotherapy.

Associations of defect mismatch repair genes with prognosis and heredity in sporadic colorectal cancer

BACKGROUND

Microsatellite instability arises due to defect mismatch repair (MMR) and occurs in 10-20% of sporadic colorectal cancer. The purpose was to investigate correlations between defect MMR, prognosis and heredity for colorectal cancer in first-degree relatives.

MATERIAL AND METHODS

Tumour tissues from 318 patients consecutively operated for colorectal cancer were analysed for immunohistochemical expression of MLH1, MSH2 and MSH6 on tissue microarrays. Information on KRAS and BRAF mutation status was available for selected cases.

RESULTS

Forty-seven (15%) tumours displayed MSI. No correlation was seen between patients exhibiting MSI in the tumour and heredity (p = 0.789). Patients with proximal colon cancer and MSI had an improved cancer-specific survival (p = 0.006) and prolonged time to recurrence (p = 0.037). In a multivariate analysis including MSI status, gender, CEA, vascular and neural invasion, patients with MSS and proximal colon cancer had an impaired cancer-specific survival compared with patients with MSI (HR, 4.32; CI, 1.46-12.78). The same prognostic information was also seen in distal colon cancer; no recurrences seen in the eight patients with stages II and III distal colon cancer and MSI, but the difference was not statistically significant.

CONCLUSION

No correlation between MSI and heredity for colorectal cancer in first-degree relatives was seen. Patients with MSI tumours had improved survival.

Epigenetic Determinants of Cancer

SUMMARYEpigenetic changes are present in all human cancers and are now known to cooperate with genetic alterations to drive the cancer phenotype. These changes involve DNA methylation, histone modifiers and readers, chromatin remodelers, microRNAs, and other components of chromatin. Cancer genetics and epigenetics are inextricably linked in generating the malignant phenotype; epigenetic changes can cause mutations in genes, and, conversely, mutations are frequently observed in genes that modify the epigenome. Epigenetic therapies, in which the goal is to reverse these changes, are now one standard of care for a preleukemic disorder and form of lymphoma. The application of epigenetic therapies in the treatment of solid tumors is also emerging as a viable therapeutic route.