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

Clinical significance of Fusobacterium nucleatum, epithelial-mesenchymal transition, and cancer stem cell markers in stage III/IV colorectal cancer patients

Colorectal cancer (CRC) is a common digestive malignancy and emerging studies have closely linked its initiation and development with gut microbiota changes. Fusobacterium nucleatum (Fn) has been recently identified as a pathogenic bacteria for CRC; however, its prognostic significance for patients is poorly investigated and is less for patients within late stage. Therefore, in this study, we made efforts to analyze its level and prognostic significance in a retrospective cohort of 280 stage III/IV CRC patients. We found that the Fn level was abnormally high in tumor tissues and correlated with tumor invasion, lymph node metastasis status, and distant metastasis. We also identified it as an independent adverse prognostic factor for cancer-specific survival (CSS) and disease-free survival (DFS). The following subgroup analysis indicated that Fn level could stratify CSS and DFS in stage IIIB/C and IV patients but failed in stage IIIA patients. In addition, stage III/IV patients with low Fn level were found to benefit more from adjuvant chemotherapy than those with high Fn level, in terms of DFS. Finally, we analyzed the expression and clinical significance of epithelial-to-mesenchymal transition (EMT) markers (E-cadherin and N-cadherin) and cancer stem cell (CSC) markers (Nanog, Oct-4, and Sox-2) in CRC tissues. The results indicated that N-cadherin, Nanog, Oct-4, and Sox-2 were adverse prognostic factors in these patients, while the opposite was true for E-cadherin. More importantly, expression of E-cadherin, N-cadherin, and Nanog was significantly correlated with Fn level in tumor tissues, suggesting the potential involvement of Fn in EMT-CSC cross talk during CRC progression. Taken together, these findings indicate that Fn is a novel predictive biomarker for clinical management in stage III/IV patients, and targeting Fn may be an effective adjuvant approach for preventing CRC metastasis and chemotherapy resistance.

A Blueprint to Advance Colorectal Cancer Immunotherapies

Immunotherapy is rapidly becoming a standard of care for many cancers. However, colorectal cancer had been generally resistant to immunotherapy, despite features in common with sensitive tumors. Observations of substantial clinical activity for checkpoint blockade in colorectal cancers with defective mismatch repair (microsatellite instability-high tumors) have reignited interest in the search for immunotherapies that could be extended to the larger microsatellite stable (MSS) population. The Cancer Research Institute and Fight Colorectal Cancer convened a group of scientists, clinicians, advocates, and industry experts in colorectal cancer and immunotherapy to compile ongoing research efforts, identify gaps in translational and clinical research, and provide a blueprint to advance immunotherapy. We identified lack of a T-cell inflamed phenotype (due to inadequate T-cell infiltration, inadequate T-cell activation, or T-cell suppression) as a broad potential explanation for failure of checkpoint blockade in MSS. The specific cellular and molecular underpinnings for these various mechanisms are unclear. Whether biomarkers with prognostic value, such as the immunoscores and IFN signatures, would also predict benefit for immunotherapies in MSS colon cancer is unknown, but if so, these and other biomarkers for measuring the potential for an immune response in patients with colorectal cancer will need to be incorporated into clinical guidelines. We have proposed a framework for research to identify immunologic factors that may be modulated to improve immunotherapy for colorectal cancer patients, with the goal that the biomarkers and treatment strategies identified will become part of the routine management of colorectal cancer. Cancer Immunol Res; 5(11); 942-9. ©2017 AACR.

Molecular Testing of Colorectal Cancer in the Modern Era: What Are We Doing and Why?

A plethora of tests are routinely ordered and interpreted by pathologists to assist the management of colorectal cancer patients. Many of these tests are immunohistochemistry assays using antibodies against prognostically relevant proteins, some of which predict therapeutic response. This review focuses on tissue DNA-based tests. It presents novel methodologies for assessing well-established biomarkers, updates the expanding spectrum of genetic alterations that are associated with resistance to inhibition of epidermal growth factor receptor signaling, and briefly discusses emerging actionable alterations that may translate into new therapeutic options for colorectal cancer patients. The utility of next-generation sequencing is emphasized.

A Molecularly Annotated Model of Patient-Derived Colon Cancer Stem-Like Cells to Assess Genetic and Nongenetic Mechanisms of Resistance to Anti-EGFR Therapy

Purpose: Patient-derived xenografts ("xenopatients") of colorectal cancer metastases have been essential to identify genetic determinants of resistance to the anti-EGFR antibody cetuximab and to explore new therapeutic strategies. From xenopatients, a genetically annotated collection of stem-like cultures ("xenospheres") was generated and characterized for response to targeted therapies.Experimental Design: Xenospheres underwent exome-sequencing analysis, gene expression profile, and in vitro targeted treatments to assess genetic, biological, and pharmacologic correspondence with xenopatients, and to investigate nongenetic biomarkers of therapeutic resistance. The outcome of EGFR family inhibition was tested in an NRG1-expressing in vivo model.Results: Xenospheres faithfully retained the genetic make-up of their matched xenopatients over in vitro and in vivo passages. Frequent and rare genetic lesions triggering primary resistance to cetuximab through constitutive activation of the RAS signaling pathway were conserved, as well as the vulnerability to their respective targeted treatments. Xenospheres lacking such alterations (RAS^wt) were highly sensitive to cetuximab, but were protected by ligands activating the EGFR family, mostly NRG1. Upon reconstitution of NRG1 expression, xenospheres displayed increased tumorigenic potential in vivo and generated tumors completely resistant to cetuximab, and sensitive only to comprehensive EGFR family inhibition.Conclusions: Xenospheres are a reliable model to identify both genetic and nongenetic mechanisms of response and resistance to targeted therapies in colorectal cancer. In the absence of RAS pathway mutations, NRG1 and other EGFR ligands can play a major role in conferring primary cetuximab resistance, indicating that comprehensive inhibition of the EGFR family is required to achieve a significant therapeutic response. Clin Cancer Res; 24(4); 807-20. ©2017 AACRSee related commentary by Napolitano and Ciardiello, p. 727.

Validation of Immunohistochemical Assays for Integral Biomarkers in the NCI-MATCH EAY131 Clinical Trial

Biomarkers that guide therapy selection are gaining unprecedented importance as targeted therapy options increase in scope and complexity. In conjunction with high-throughput molecular techniques, therapy-guiding biomarker assays based upon immunohistochemistry (IHC) have a critical role in cancer care in that they inform about the expression status of a protein target. Here, we describe the validation procedures for four clinical IHC biomarker assays-PTEN, RB, MLH1, and MSH2-for use as integral biomarkers in the nationwide NCI-Molecular Analysis for Therapy Choice (NCI-MATCH) EAY131 clinical trial. Validation procedures were developed through an iterative process based on collective experience and adaptation of broad guidelines from the FDA. The steps included primary antibody selection; assay optimization; development of assay interpretation criteria incorporating biological considerations; and expected staining patterns, including indeterminate results, orthogonal validation, and tissue validation. Following assay lockdown, patient samples and cell lines were used for analytic and clinical validation. The assays were then approved as laboratory-developed tests and used for clinical trial decisions for treatment selection. Calculations of sensitivity and specificity were undertaken using various definitions of gold-standard references, and external validation was required for the PTEN IHC assay. In conclusion, validation of IHC biomarker assays critical for guiding therapy in clinical trials is feasible using comprehensive preanalytic, analytic, and postanalytic steps. Implementation of standardized guidelines provides a useful framework for validating IHC biomarker assays that allow for reproducibility across institutions for routine clinical use. Clin Cancer Res; 24(3); 521-31. ©2017 AACR.

High-risk family colorectal cancer screening service in Ireland: Critical review of clinical outcomes

BACKGROUND

We present the 15-year experience of a family colorectal cancer screening service in Ireland with emphasis on real life experience and outcomes.

METHODS

Questionnaires were used to assess family cancer history and assign patients to risk categories; 'Moderate Risk', HNPCC, (suspected) genetic syndrome (non-HNPCC), 'Low Risk'. Screening was by full colonoscopy. We report neoplastic yield, examining effect of risk category, age, gender, and index colonoscopy findings.

RESULTS

Between 1998 and 2013, 2242 individuals were referred; 57.3% female, 42.7% male, median age 46 years (range9-85yrs). Median follow up time was 7.9yrs (range 0.5-15.3yrs). Follow up data after exclusion (non-compliance, known CRC) was available in 1496 (66.7%): 'Moderate risk' 785 (52.5%), HNPCC 256 (17.1%), (suspected) genetic syndrome (non-HNPCC) 85 (5.7%), 'Low Risk' 370 (24.7%). Screening was performed in 1025(68.5%) patients; colonoscopy data available for 993 (96.9%); total 1914 colonoscopies. At index colonoscopy, 178 (18.0%) patients had adenomas; 56 (5.5%) advanced adenoma. During the entire study period, 240 (24.2%) had an adenoma; 69 (7.0%) advanced adenoma. Cancers were diagnosed on screening in 2 patients. Older age and male gender were associated with higher adenoma detection rate; p<0.001, p=0.01, respectively. Risk category did not affect adenoma yield. Adenoma and advanced adenoma detection at index colonoscopy were associated with detection of same at follow up screening; p<0.001.

CONCLUSION

Male gender and age (>50) were the core identifiable risk factors for neoplasia at screening colonoscopy in this family screening setting. Our results would support less intensive surveillance in younger patients (<50), particularly where index colonoscopy is normal.

Guidelines for Colorectal Cancer Testing: Evidence-Based Practice Recommendations

This Editorial provides readers additional insight on the colorectal guideline appearing in this issue.

Precision surgery for colorectal liver metastases: Opportunities and challenges of omics-based decision making

Precision surgery involves improving patient selection to ensure that surgical intervention that is proven to benefit on a population level is the optimal treatment for each individual patient. For patients with colorectal liver metastases (CRLM), existing prognostic scoring systems rely on well-recognised histopathological features such as size and number of lesions. Advances in preoperative imaging algorithms mean that increasingly low volume disease can be detected, improving assessment of these factors. In addition, novel imaging modalities mean that underlying tumour biology and metabolic behaviour during therapy can be assessed. Molecular analysis of tumours can provide crucial prognostic information, with the critical role of RAS/RAF mutations in prognosis well recognised. The optimal source of tissue for this level of analysis is debated, with good concordance between primary and metastatic lesions for some recognised prognostic factors but marked discrepancies for a variety of other relevant mutations. As well as mutational heterogeneity between primary and metastatic lesions, heterogeneity within tumours and dynamic changes in tumour biology over time present a significant challenge in assessing tumour for prognostic biomarkers. Circulating tumour cells offer one potential method of longitudinal tumour analysis, but are limited by current technologies. This review article summarises some of the key advances in prognostication for patients with resectable colorectal liver metastases, as well as highlighting the potential limitations of such an approach.