Extended RAS testing in metastatic colorectal cancer-Refining the predictive molecular biomarkers

Anti-EGFR Antibodies in the Management of Advanced Colorectal Cancer

Colorectal cancer is the third most common cancer worldwide, and incidence is rising in younger individuals. Anti-EGFR antibodies, including cetuximab and panitumumab, have been incorporated into standard-of-care practice for patients with advanced disease. Herein, we review the molecular characteristics of these agents and the trials that lead to their approvals. Further, we discuss clinical implications of data regarding biomarkers that dictate treatment selection, different dosing strategies, and side effect management. Finally, we look towards the future and describe contexts in which these agents are currently being investigated clinically with a focus on combinations with MAPK-targeted therapies and immunotherapy. Overall, this review provides historical context, current clinical usage, and future directions for anti-EGFR antibodies in advanced colorectal cancer.

Long Noncoding RNA LOC550643 Acts as an Oncogene in the Growth Regulation of Colorectal Cancer Cells

Long noncoding RNAs play a key role in the progression of colorectal cancer (CRC). However, the role and mechanism of LOC550643 in CRC cell growth and metastasis remain largely unknown. In this study, we assessed the clinical impacts of LOC550643 on CRC through the analysis of The Cancer Genome Atlas database, which revealed the significant upregulation of LOC550643 in CRC. Moreover, the high expression of LOC550643 was associated with poor survival in patients with CRC (p = 0.001). Multivariate Cox regression analysis indicated that LOC550643 overexpression was an independent prognostic factor for shorter overall survival in patients with CRC (adjusted hazard ratio, 1.90; 95% confidence interval, 1.21-3.00; p = 0.006). A biological function analysis revealed that LOC550643 knockdown reduced colon cancer cell growth by hindering cell cycle progression. In addition, LOC550643 knockdown significantly induced cell apoptosis through the inhibition of signaling activity in phosphoinositide 3-kinases. Moreover, LOC550643 knockdown contributed to the inhibition of migration and invasion ability in colon cancer cells. Furthermore, miR-29b-2-5p interacted with the LOC550643 sequence. Ectopic miR-29b-2-5p significantly suppressed colon cancer cell growth and motility and induced cell apoptosis. Our findings suggest that, LOC550643-miR-29b-2-5p axis was determined to participate in the growth and metastasis of colon cancer cells; this could serve as a useful molecular biomarker for cancer diagnosis and as a potential therapeutic target for CRC.

Recent Advances in Our Knowledge of mCRC Tumor Biology and Genetics: A Focus on Targeted Therapy Development

Metastatic colorectal cancer (mCRC) remains a highly lethal malignancy although considerable progress has resulted from characterizing molecular alterations such as RAS mutation status and extent of microsatellite instability (MSI) to guide optimal use of available therapies. The availability of gene expression profiling, next generation sequencing technologies, proteomics analysis and other technologies provides high resolution information on individual tumors, including metastatic lesions to better define intra-tumor and inter-tumor heterogeneity. Recent literature applying this information to further customize personalized therapies is reviewed. Current biomarker-based stratification used to select optimal therapy that is personalized to the mutation profile of individual tumors is described. Recent literature using whole exome sequencing of metastatic lesions and primary CRC tumors and other advanced technologies to more fully elucidate the tumor biology specific to mCRC sub-types and to develop more precise therapies that improve outcomes is also reviewed.

GUCY2C as a biomarker to target precision therapies for patients with colorectal cancer

Introduction

Colorectal cancer (CRC) is one of the most-deadly malignancies worldwide. Current therapeutic regimens for CRC patients are relatively generic, based primarily on disease type and stage, with little variation. As the field of molecular oncology advances, so too must therapeutic management of CRC. Understanding molecular heterogeneity has led to a new-found promotion for precision therapy in CRC; underlining the diversity of molecularly targeted therapies based on individual tumor characteristics.

Areas covered

We review current approaches for the treatment of CRC and discuss the potential of precision therapy in advanced CRC. We highlight the utility of the intestinal protein guanylyl cyclase C (GUCY2C), as a multi-purpose biomarker and unique therapeutic target in CRC. Here, we summarize current GUCY2C-targeted approaches for treatment of CRC.

Expert opinion

The GUCY2C biomarker has multi-faceted utility in medicine. Developmental investment of GUCY2C as a diagnostic and therapeutic biomarker offers a variety of options taking the molecular characteristics of cancer into account. From GUCY2C-targeted therapies, namely cancer vaccines, CAR-T cells, and monoclonal antibodies, to GUCY2C agonists for chemoprevention in those who are at high risk for developing colorectal cancer, the utility of this protein provides many avenues for exploration with significance in the field of precision medicine.

Precision Approaches in the Management of Colorectal Cancer: Current Evidence and Latest Advancements Towards Individualizing the Treatment

The genetic and molecular underpinnings of metastatic colorectal cancer have been studied for decades, and the applicability of these findings in clinical decision making continues to evolve. Advancements in translating molecular studies have provided a basis for tailoring chemotherapeutic regimens in metastatic colorectal cancer (mCRC) treatment, which have informed multiple practice guidelines. Various genetic and molecular pathways have been identified as clinically significant in the pathogenesis of metastatic colorectal cancer. These include rat sarcoma (RAS), epithelial growth factor receptor (EGFR), vascular endothelial growth factor VEGF, microsatellite instability, mismatch repair, and v-raf murine sarcoma viral oncogene homolog b1 (BRAF) with established clinical implications. RAS mutations and deficiencies in the mismatch repair pathway guide decisions regarding the administration of anti-EGFR-based therapies and immunotherapy, respectively. Furthermore, there are several emerging pathways and therapeutic modalities that have not entered mainstream use in mCRC treatment and are ripe for further investigation. The well-established data in the arena of targeted therapies provide evidence-based support for the use or avoidance of various therapeutic regimens in mCRC treatment, while the emerging pathways and platforms offer a glimpse into the future of transforming a precision approach into a personalized treatment.

HER2-HER3 Heterodimer Quantification by FRET-FLIM and Patient Subclass Analysis of the COIN Colorectal Trial

BACKGROUND

The phase III MRC COIN trial showed no statistically significant benefit from adding the EGFR-target cetuximab to oxaliplatin-based chemotherapy in first-line treatment of advanced colorectal cancer. This study exploits additional information on HER2-HER3 dimerization to achieve patient stratification and reveal previously hidden subgroups of patients who had differing disease progression and treatment response.

METHODS

HER2-HER3 dimerization was quantified by fluorescence lifetime imaging microscopy in primary tumor samples from 550 COIN trial patients receiving oxaliplatin and fluoropyrimidine chemotherapy with or without cetuximab. Bayesian latent class analysis and covariate reduction was performed to analyze the effects of HER2-HER3 dimer, RAS mutation, and cetuximab on progression-free survival and overall survival (OS). All statistical tests were two-sided.

RESULTS

Latent class analysis on a cohort of 398 patients revealed two patient subclasses with differing prognoses (median OS = 1624 days [95% confidence interval [CI] = 1466 to 1816 days] vs 461 days [95% CI = 431 to 504 days]): Class 1 (15.6%) showed a benefit from cetuximab in OS (hazard ratio = 0.43, 95% CI = 0.25 to 0.76, P = .004). Class 2 showed an association of increased HER2-HER3 with better OS (hazard ratio = 0.64, 95% CI = 0.44 to 0.94, P = .02). A class prediction signature was formed and tested on an independent validation cohort (n = 152) validating the prognostic utility of the dimer assay. Similar subclasses were also discovered in full trial dataset (n = 1630) based on 10 baseline clinicopathological and genetic covariates.

CONCLUSIONS

Our work suggests that the combined use of HER dimer imaging and conventional mutation analyses will be able to identify a small subclass of patients (>10%) who will have better prognosis following chemotherapy. A larger prospective cohort will be required to confirm its utility in predicting the outcome of anti-EGFR treatment.

Early-onset colorectal cancer: A distinct entity with unique genetic features

The aim of the present study was to elucidate the genetic features of early-onset colorectal cancer (CRC), particularly the genetic mutations that may be regarded as prognostic and/or predictive markers in CRC and other malignancies. In total, 40 patients with non-polyposis CRC aged 35 or younger were selected. The formalin-fixed, paraffin-embedded tumors acquired were subjected to mismatch repair (MMR) protein immunochemical staining and gene analysis with next-generation sequencing (44 exons, 17 genes; Ion Torrent Sequencing Platform). A total of 11 (27.5%) tumors presented with MMR protein deficiency (dMMR) and 26 (65%) tumors harbored one or more genetic mutations, including K-RAS proto-oncogene (35%), phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha (PIK3CA; 20%), B-Raf proto-oncogene (5%), erb-b2 receptor tyrosine kinase 2 (5%), discoidin domain receptor tyrosine kinase 2 (5%), N-RAS proto-oncogene (2.5%), KIT proto-oncogene (2.5%), TSC complex subunit 1 (2.5%), DNA methyltransferase 3 alpha (2.5%) and ABL proto-oncogene 1 (2.5%). Of the dMMR tumors, 81.8% (9/11) of cases presented with mutations in the tested genes, while only 58.6% (17/29) of the MMR-proficient (pMMR) tumors presented with these (P=0.158). PI3KCA was frequently mutated in dMMR tumors compared to pMMR tumors (P=0.025). In a subgroup with a family history of CRC, the dMMR status (P<0.001) and PIK3CA genetic mutation status (P=0.01) were more frequently observed compared to the other two groups (with a family history of other cancer types or no malignancy). Almost all patients who had relatives with CRC presented with both dMMR and other genetic mutations, while this was not observed in the patients who had relatives with other types of carcinoma. Certain genetic mutations that are rarely reported in CRC were only identified in those patients with a family history of carcinoma. In conclusion, non-polyposis CRC in young adults presents as a distinct entity with a unique set of genetic features. However, investigation of more cases in further studies is required to verify the present results.

NRAS mutant E132K identified in young-onset sporadic colorectal cancer and the canonical mutants G12D and Q61K affect distinct oncogenic phenotypes

Recent data show a global increase in colorectal cancer (CRC) cases among younger demographics, which portends poorer prognosis. The cause of rising incidence is uncertain, and its mutational landscape remains largely unexplored, including those in genes of the epidermal growth factor receptor pathway. Among these are NRAS mutants where there is paucity of functional studies compared to KRAS. Here, the novel NRAS mutant E132K, identified in three tumor samples from Filipino young-onset, sporadic colorectal cancer patients, was investigated for its effects on different cancer hallmarks, alongside the NRAS canonical mutants G12D and Q61K which are yet poorly characterized in the context of CRC. The novel NRAS mutant E132K and the canonical G12D and Q61K mutants show resistance to apoptosis, cytoskeletal reorganization, and loss of adhesion. In contrast to activating KRAS mutations, including the analogous KRAS G12D and Q61K mutations, all three NRAS mutants have no apparent effect on cell proliferation and motility. The results highlight the need to characterize isoform- and mutation-specific oncogenic phenotypes which can have repercussions in disease management and choice of therapeutic intervention. Further analyses of young-onset versus late-onset CRC datasets are necessary to qualify NRAS E132K as a biomarker for the young-onset subtype.

Immunohistochemical evaluation of the prognostic and predictive power of epidermal growth factor receptor ligand levels in patients with metastatic colorectal cancer

For patients with metastatic colorectal cancer (mCRC), epidermal growth factor receptor (EGFR) inhibitors are limited to patients with RAS wild-type tumours. Not all patients will benefit from treatment and better predictive biomarkers are needed. Here we investigated the prognostic and predictive impact of the EGFR ligands amphiregulin (AREG) and epiregulin (EREG). Expression levels were assessed by immunohistochemistry on 99 KRAS wild-type tumours. AREG and EREG positivity was seen in 49% and 50% of cases, respectively. No difference in expression was observed by primary tumour side. There was no significant difference in OS by AREG or EREG expression. In the subset of patients who received an EGFR inhibitor, EREG positivity was associated with longer OS (median 34.0 vs. 27.0 months, p = 0.033), driven by a difference in patients with a left-sided primary (HR 0.37, p = 0.015). Our study supports further investigation into EREG as a predictive biomarker in mCRC.

The Evolving Biomarker Landscape for Treatment Selection in Metastatic Colorectal Cancer

The approval of targeted therapies for metastatic colorectal cancer (mCRC) has led to important improvements in patient outcomes. However, it is still necessary to increase individualisation of treatments based on tumour genetic profiles to optimise efficacy, while minimising toxicity. As such, there is currently great focus on the discovery and validation of further biomarkers in mCRC, with many new potential prognostic and predictive markers being identified alongside developments in patient molecular profiling technologies. Here, we review data for validated and emerging biomarkers impacting treatment strategies in mCRC. We completed a structured literature search of the PubMed database to identify relevant publications, limiting for English-language publications published between 1 January 2014 and 11 July 2018. In addition, we performed a manual search of the key general oncology and CRC-focused congresses to identify abstracts reporting emerging mCRC biomarker data, and of ClinicalTrials.gov to identify ongoing clinical trials investigating emerging biomarkers in mCRC and/or molecular-guided clinical trials. There is solid evidence supporting the use of BRAF status as a prognostic biomarker and DYPD, UGT1A1, RAS, and microsatellite instability as predictive biomarkers in mCRC. There are a number of emerging biomarkers that may prove to be clinically relevant in the future to have prognostic (HPP1 methylation), predictive (HER3, microRNAs, anti-angiogenic markers, and CRC intrinsic subtypes), or both prognostic and predictive values (HER2, CpG island methylator phenotype, tumour mutational load, gene fusions, and consensus molecular subtypes). As such, new biomarker-led treatment strategies in addition to anti-epidermal growth factor receptor and anti-angiogenetic treatments are being explored. Biomarkers that are not recommended to be tested in clinical practice or are unlikely to be imminently clinically relevant for mCRC include thymidylate transferase, ERCC1, PIK3CA, and PTEN. We highlight the clinical utility of existing and emerging biomarkers in mCRC and provide recommended treatment strategies according to the biomarker status. An update on ongoing molecular-guided clinical trials is also provided.

Molecular subtyping of colorectal cancer: Recent progress, new challenges and emerging opportunities

Colorectal cancer (CRC) is one of the leading causes of cancer-related deaths worldwide. Similar to many other malignancies, CRC is a heterogeneous disease, making it a clinical challenge for optimization of treatment modalities in reducing the morbidity and mortality associated with this disease. A more precise understanding of the biological properties that distinguish patients with colorectal tumors, especially in terms of their clinical features, is a key requirement towards a more robust, targeted-drug design, and implementation of individualized therapies. In the recent decades, extensive studies have reported distinct CRC subtypes, with a mutation-centered view of tumor heterogeneity. However, more recently, the paradigm has shifted towards transcriptome-based classifications, represented by six independent CRC taxonomies. In 2015, the colorectal cancer subtyping consortium reported the identification of four consensus molecular subtypes (CMSs), providing thus far the most robust classification system for CRC. In this review, we summarize the historical timeline of CRC classification approaches; discuss their salient features and potential limitations that may require further refinement in near future. In other words, in spite of the recent encouraging progress, several major challenges prevent translation of molecular knowledge gleaned from CMSs into the clinic. Herein, we summarize some of these potential challenges and discuss exciting new opportunities currently emerging in related fields. We believe, close collaborations between basic researchers, bioinformaticians and clinicians are imperative for addressing these challenges, and eventually paving the path for CRC subtyping into routine clinical practice as we usher into the era of personalized medicine.

Association of baseline absolute neutrophil counts and survival in patients with metastatic colorectal cancer treated with second-line antiangiogenic therapies: exploratory analyses of the RAISE trial and validation in an electronic medical record data set

BACKGROUND

In the RAISE trial, ramucirumab+leucovorin/fluorouracil/irinotecan (FOLFIRI) improved the median overall survival (mOS) of patients with previously treated metastatic colorectal cancer versus patients treated with placebo+FOLFIRI but had a higher incidence of neutropaenia, leading to more chemotherapy dose modifications and discontinuations. Thus, we conducted an exploratory post-hoc analysis of RAISE and a retrospective, observational analysis of electronic medical record (EMR) data to determine and verify the association of neutropaenia, baseline absolute neutrophil count (ANC) and survival.

METHODS

The RAISE analysis used the study safety population (n=1057). IMS Health Oncology Database (IMS EMR) was the source for the real-world data set (n=617).

RESULTS

RAISE patients with treatment-emergent neutropaenia had improved mOS compared with those without (ramucirumab arm: 16.1 vs 10.7 months, HR=0.57, p<0.0001; placebo arm: 12.7 vs 10.7 months, HR=0.76, p=0.0065). RAISE patients with low ANC versus high baseline ANC also had longer mOS (ramucirumab arm: 15.2 vs 8.9 months, HR=0.49, p<0.0001; placebo arm: 13.2 vs 7.3 months, HR=0.50, p<0.0001). The results were similar for IMS EMR low versus high baseline ANC (bevacizumab+FOLFIRI patients: 14.9 vs 7.7 months, HR=0.59, p<0.0001; FOLFIRI alone: 14.6 vs 5.4 months, HR=0.37, p<0.0001). Patients in the RAISE trial with low baseline ANC were more likely to develop neutropaenia (OR: ramucirumab arm=2.62, p<0.0001; placebo arm=2.16, p=0.0003).

CONCLUSION

Neutropaenia during treatment, and subsequent dose modifications or discontinuations, do not compromise treatment efficacy. Baseline ANC is a strong prognostic factor for survival and is associated with treatment-emergent neutropaenia in the analysed population.

TRIAL REGISTRATION NUMBER

NCT01183780, Results.

K-ras Mutations as the Earliest Driving Force in a Subset of Colorectal Carcinomas

K-ras oncogene is a key factor in colorectal cancer. Based on published and our data we propose that K-ras could be the oncogene responsible for the inactivation of the tumor-suppressor gene APC, currently considered as the initial step in colorectal tumorigenesis. K-ras fulfills the criteria of the oncogene-induced DNA damage model, as it can provoke well-established causes for inactivating tumor-suppressors, i.e. DNA double-strand breaks (causing allele deletion) and ROS production (responsible for point mutation). The model we propose is a variation of the currently existing model and hypothesizes that, in a subgroup of colorectal carcinomas, K-ras mutation may precede APC inactivation, representing the earliest driving force and, probably, an early biomarker of colorectal carcinogenesis. This observation is clinically useful, since it may modify the preventive colorectal cancer strategy, restricting numerically patients undergoing colonoscopies to those bearing K-ras mutation in their colorectum, either in benign polyps or the normal accompanying mucosa.

Important molecular genetic markers of colorectal cancer

Colorectal cancer (CRC) ranks third in the incidences of cancer morbidity and mortality worldwide. CRC is rather heterogeneous with regard to molecular genetic characteristics and pathogenic pathways. A wide spectrum of biomarkers is used for molecular subtype determination, prognosis, and estimation of sensitivity to different drugs in practice. These biomarkers can include germline and somatic mutations, chromosomal aberrations, genomic abnormalities, gene expression alterations at mRNA or protein level and changes in DNA methylation status. In the present review we discuss the most important and well-studied CRC biomarkers, and their potential clinical significance and current approaches to molecular classification of colorectal tumors.

Prognostic impact of mutation profiling in patients with stage II and III colon cancer

Development of colorectal cancer (CRC) associates with accumulation of genetic mutations include the epidermal growth factor receptor (EGFR) signaling pathway. However, whether mutations in KRAS together with downstream factors BRAF, PIK3CA and NRAS impact prognosis is still unclear for stage II-III colon cancer. In the present study a total of 228 stage II-III colon cancer samples were retrospectively collected, KRAS (codons 12, 13 and 61), BRAF (exon 11 and exon 15), PIK3CA (exon 9 and exon 20) and NRAS (codons 12, 13 and 61) status was detected by Sanger sequencing, 37.89% (86/227) tumors harbored a KRAS mutation, 7.02% (16/228) harbored a BRAF mutation, 13.18% (29/220) harbored a PIK3CA mutation and 0.89% (2/224) harbored a NRAS mutation. NRAS mutations existed only in stage II colon cancer. Older groups harbored a higher KRAS and BRAF mutation (P < 0.05), PIK3CA (exon9) mutations appeared more common in worse differentiation tumors (P = 0.032). Moreover, PIK3CA (E545K) mutation was significantly associated with tumor recurrence (P = 0.031) and acted independently prognostic for poor OS (P = 0.044), while only in stage III colon cancer. KRAS, BRAF and NRAS mutations do not have major prognostic value in stage II and III colon cancer, subtypes of gene mutations should be further investigated for a better understanding in CRC.

Prognostic and Predictive Significance of Stromal Fibroblasts and Macrophages in Colon Cancer

Colon cancer development and malignant progression are driven by genetic and epigenetic alterations in tumor cells and by factors from the tumor microenvironment. Cancer cells become reliant on the activity of specific oncogenes and on prosurvival and proliferative signals they receive from the abnormal environment they create and reside in. Accordingly, the response to anticancer therapy is determined by genetic and epigenetic changes that are intrinsic to tumor cells and by the factors present in the tumor microenvironment. Recent advances in the understanding of the involvement of the tumor microenvironment in tumor progression and therapeutic response are optimizing the application of prognostic and predictive factors in colon cancer. Moreover, new targets in the tumor microenvironment that are amenable to therapeutic intervention have been identified. Because stromal cells are with rare exceptions genetically stable, the tumor microenvironment has emerged as a preferred target for therapeutic drugs. In this review, we discuss the role of stromal fibroblasts and macrophages in colon cancer progression and in the response of colon cancer patients to therapy.