Practical and Robust Identification of Molecular Subtypes in Colorectal Cancer by Immunohistochemistry

Abstract

Purpose: Recent transcriptomic analyses have identified four distinct molecular subtypes of colorectal cancer with evident clinical relevance. However, the requirement for sufficient quantities of bulk tumor and difficulties in obtaining high-quality genome-wide transcriptome data from formalin-fixed paraffinembedded tissue are obstacles toward widespread adoption of this taxonomy. Here, we develop an immunohistochemistrybased classifier to validate the prognostic and predictive value of molecular colorectal cancer subtyping in a multicenter study.Experimental Design: Tissue microarrays from 1,076 patients with colorectal cancer from four different cohorts were stained for five markers (CDX2, FRMD6, HTR2B, ZEB1, and KER) by immunohistochemistry and assessed for microsatellite instability. An automated classification system was trained on one cohort using quantitative image analysis or semiquantitative pathologist scoring of the cores as input and applied to three independent clinical cohorts.Results: This classifier demonstrated 87% concordance with the gold-standard transcriptome-based classification. Application to three validation datasets confirmed the poor prognosis of the mesenchymal-like molecular colorectal cancer subtype. In addition, retrospective analysis demonstrated the benefit of adding cetuximab to bevacizumab and chemotherapy in patients with RAS wild-type metastatic cancers of the canonical epithelial-like subtypes.Conclusions: This study shows that a practical and robust immunohistochemical assay can be employed to identify molecular colorectal cancer subtypes and uncover subtypespecific therapeutic benefit. Finally, the described tool is available online for rapid classification of colorectal cancer samples, both in the format of an automated image analysis pipeline to score tumor core staining, and as a classifier based on semiquantitative pathology scoring.

Immunotherapy for Colorectal Cancer

“…At present, this is predominantly a classification with application to research rather than routine patient care. Interestingly, recent data has suggested that these subtypes may be accurately assigned through straightforward IHC based assays, though this remains to be validated in additional data sets [10]. CMS 1 tumors (MSI Immune, 14%) are characterized by hypermutation, MSI, and strong immune activation.…”

Colorectal Cancer Consensus Molecular Subtypes Translated to Preclinical Models Uncover Potentially Targetable Cancer Cell Dependencies

“…The CMS classification has prognostic value independent of cancer stage, with dismal survival outcomes for the CMS4 population, even when treated with standard adjuvant chemotherapies (22). A potential predictive value of the CMS groups has also been suggested from retrospective analysis of clinical trials, including lack of benefit from oxaliplatin (22) and anti-EGFR treatment (17,23) in tumors with a mesenchymal-like phenotype, the latter independent of RAS mutation status. However, increased understanding of the unique drug sensitivities of the individual CMS groups has great potential to advance precision medicine in colorectal cancer.…”

Prognostic, predictive, and pharmacogenomic assessments of CDX2 refine stratification of colorectal cancer

“…This transcription factor is a major regulator of intestinal development and differentiation (Verzi et al ., 2011), and it is specifically expressed in the intestinal epithelium (Werling et al ., 2003). CDX2 is a tumor suppressor in the adult colon, and loss of CDX2 expression is associated with advanced stages of CRC, poor differentiation, BRAF mutation, and MSI (Olsen et al ., 2014), as well as the CMS1 and CMS4 subtypes (Pilati et al ., 2017; Trinh et al ., 2017). In concordance, loss of CDX2 expression has been found to be associated with a poor patient prognosis in several studies (Baba et al ., 2009; Dalerba et al ., 2016; Lugli et al ., 2008; Zhang et al ., 2017), and it was recently suggested that the prognostic value is limited to the CMS4 group (Pilati et al ., 2017).…”