Colorectal cancer (CRC) is a frequently lethal disease with heterogeneous outcomes and drug responses. To resolve inconsistencies among the reported gene expression–based CRC classifications and facilitate clinical translation, we formed an international consortium dedicated to large-scale data sharing and analytics across expert groups. We show marked interconnectivity between six independent classification systems coalescing into four consensus molecular subtypes (CMS) with distinguishing features: CMS1 (MSI Immune, 14%), hypermutated, microsatellite unstable, strong immune activation; CMS2 (Canonical, 37%), epithelial, chromosomally unstable, marked WNT and MYC signaling activation; CMS3 (Metabolic, 13%), epithelial, evident metabolic dysregulation; and CMS4 (Mesenchymal, 23%), prominent transforming growth factor β activation, stromal invasion, and angiogenesis. Samples with mixed features (13%) possibly represent a transition phenotype or intra-tumoral heterogeneity. We consider the CMS groups the most robust classification system currently available for CRC – with clear biological interpretability – and the basis for future clinical stratification and subtype–based targeted interventions.

Background It is hypothesized that BRAF mutant cancers represent a discrete subset of metastatic colorectal cancer (CRC) defined by poorer survival. This study investigates whether BRAF mutant CRC is further defined by a distinct pattern of metastatic spread and explores the impact of BRAF mutation and microsatellite instability (MSI) on prognosis in metastatic CRC. Methods Using prospective clinical data and molecular analyses from two major centers (Royal Melbourne Hospital and MD Anderson Cancer Centre) patients with known BRAF mutation status were analyzed for clinical characteristics, survival and metastatic sites. Results We identified 524 metastatic CRC patients where BRAF mutation status was known, 57 (11%) were BRAF mutant tumors. BRAF mutant tumors were significantly associated with right-sided primary tumor, MSI and poorer survival (median 10.4mo v 34.7mo, p<0.001). A distinct pattern of metastatic spread was observed in BRAF mutant tumors, namely higher rates of peritoneal metastases (46% v 24%, p=0.001), distant lymph node metastases (53% v 38%, p=0.008) and lower rates of lung metastases (35% v 49%, p=0.049). In additional survival analyses, MSI tumors had significantly poorer survival compared to micro-satellite stable tumors (22.1mo v 11.1 mo, p=0.017), but this difference was not evident in the BRAF mutant population. Conclusions The pattern of metastatic spread observed in this study further defines BRAF mutant CRC as a discrete disease subset. We demonstrate that, unlikely early stage disease, MSI is associated with poorer survival in metastatic CRC, although this is driven by its association with BRAF mutation.

Pathologic response predicts survival after preoperative chemotherapy and resection of CLM. Degree of pathologic response represents a new outcome end point for prognosis after resection of CLM.

PurposeBRAF V600E mutation is seen in 5% to 8% of patients with metastatic colorectal cancer (CRC) and is associated with poor prognosis. Vemurafenib, an oral BRAF V600 inhibitor, has pronounced activity in patients with metastatic melanoma, but its activity in patients with BRAF V600E–positive metastatic CRC was unknown.Patients and MethodsIn this multi-institutional, open-label study, patients with metastatic CRC with BRAF V600 mutations were recruited to an expansion cohort at the previously determined maximum-tolerated dose of 960 mg orally twice a day.ResultsTwenty-one patients were enrolled, of whom 20 had received at least one prior metastatic chemotherapy regimen. Grade 3 toxicities included keratoacanthomas, rash, fatigue, and arthralgia. Of the 21 patients treated, one patient had a confirmed partial response (5%; 95% CI, 1% to 24%) and seven other patients had stable disease by RECIST criteria. Median progression-free survival was 2.1 months. Patterns of concurrent mutations, microsatellite instability status, CpG island methylation status, PTEN loss, EGFR expression, and copy number alterations were not associated with clinical benefit. In contrast to prior expectations, concurrent KRAS and NRAS mutations were detected at low allele frequency in a subset of the patients' tumors (median, 0.21% allele frequency) and were apparent mechanisms of acquired resistance in vemurafenib-sensitive patient-derived xenograft models.ConclusionIn marked contrast to the results seen in patients with BRAF V600E–mutant melanoma, single-agent vemurafenib did not show meaningful clinical activity in patients with BRAF V600E mutant CRC. Combination strategies are now under development and may be informed by the presence of intratumor heterogeneity of KRAS and NRAS mutations.

SUMMARY We report a paracrine effect whereby endothelial cells (ECs) promote the cancer stem cell (CSC) phenotype of human colorectal cancer (CRC) cells. We showed that, without direct cell-cell contact, ECs secrete factors that promoted the CSC phenotype in CRC cells via Notch activation. In human CRC specimens, CD133 and Notch intracellular domain-positive cells co-localized with CRC cells in perivascular regions. An EC-derived, soluble form of Jagged-1, via ADAM17 proteolytic activity, led to Notch activation in CRC cells in a paracrine manner; these effects were blocked by immunodepletion of Jagged-1 in EC conditioned medium or blockade of ADAM17 activity. ECs play an active role in promoting Notch signaling and the CSC phenotype by secreting soluble Jagged-1.

HE ADDITION OF BEVACIZUMAB, a monoclonal antibody against vascular endothelial growth factor, to cytotoxic chemotherapy is associated with improved survival in patients with stage IV colorectal cancer and higher pathologic response rates in patients undergoing resection of colorectal liver metastases. 1,2 Response to bevacizumab, which exerts an antiangiogenic mechanism of action, may be inadequately assessed by traditional size-based radiologic criteria, the Response Evaluation Criteria in Solid Tumors (RECIST), which were designed for assessing tumor volume reduction following cytotoxic chemotherapy. [3][4][5] In support of this, a recent phase 3 trial showed that the addition of bevacizumab to oxaliplatin-based chemotherapy for metastatic colorectal cancer improved progression-free survival without affecting RECIST-defined response rates. 6 Recently, pathologic response to preoperative chemotherapy has been shown to correlate with improved sur-Author Affiliations are listed at the end of this article.

Metastasis is a complex biological process that has been difficult to delineate in human colorectal cancer (CRC) patients. A major obstacle in understanding metastatic lineages is the extensive intra-tumor heterogeneity at the primary and metastatic tumor sites. To address this problem, we developed a highly multiplexed single-cell DNA sequencing approach to trace the metastatic lineages of two CRC patients with matched liver metastases. Single-cell copy number or mutational profiling was performed, in addition to bulk exome and targeted deep-sequencing. In the first patient, we observed monoclonal seeding, in which a single clone evolved a large number of mutations prior to migrating to the liver to establish the metastatic tumor. In the second patient, we observed polyclonal seeding, in which two independent clones seeded the metastatic liver tumor after having diverged at different time points from the primary tumor lineage. The single-cell data also revealed an unexpected independent tumor lineage that did not metastasize, and early progenitor clones with the "first hit" mutation in APC that subsequently gave rise to both the primary and metastatic tumors. Collectively, these data reveal a late-dissemination model of metastasis in two CRC patients and provide an unprecedented view of metastasis at single-cell genomic resolution.

We report the first case series of ICI-associated colitis successfully treated with fecal microbiota transplantation (FMT), with reconstitution of the gut microbiome and a relative increase in the proportion of regulatory T cells (Tregs) within the colonic mucosa. These preliminary data provide evidence that modulation of the gut microbiome may abrogate ICI-associated colitis.