KRAS genotypic changes of circulating tumor cells during treatment of patients with metastatic colorectal cancer

Correlation between KRAS Mutation and CTLA-4 mRNA Expression in Circulating Tumour Cells: Clinical Implications in Colorectal Cancer

Combination strategies of KRAS inhibition with immunotherapy in treating advanced or recurrent colorectal carcinoma (CRC) may need to be assessed in circulating tumour cells (CTCs) to achieve better clinical outcomes. This study aimed to investigate the genomic variations of KRAS in CTCs and matched CRC tissues and compared mRNA expression of KRAS and CTLA-4 between wild-type and KRAS-mutated CTCs and CRC tissues. Clinicopathological correlations were also compared. Six known mutations of KRAS were identified at both codon 12 and codon 13 (c.35G>T/G12V, c.35G>A7/G12D, c.35G>C/G12A, c.34G>A/G12S, c.38G>C/G13A, and c.38G>A/G13D). Three CTC samples harboured the identified mutations (16.7%; 3/18), while fifteen matched primary tumour tissues (65.2%, 15/23) showed the mutations. CTCs harbouring the KRAS variant were different from matched CRC tissue. All the mutations were heterozygous. Though insignificant, CTLA-4 mRNA expression was higher in patients carrying KRAS mutations. Patients harbouring KRAS mutations in CTCs were more likely to have poorly differentiated tumours (p = 0.039) and with lymph node metastasis (p = 0.027) and perineural invasion (p = 0.014). KRAS mutations in CTCs were also significantly correlated with overall pathological stages (p = 0.027). These findings imply the genetic basis of KRAS with immunotherapeutic target molecules based on a real-time platform. This study also suggests the highly heterogeneous nature of cancer cells, which may facilitate the assessment of clonal dynamics across a single patient's disease.

Extracellular Vesicles' Genetic Cargo as Noninvasive Biomarkers in Cancer: A Pilot Study Using ExoGAG Technology

The two most developed biomarkers in liquid biopsy (LB)-circulating tumor cells and circulating tumor DNA-have been joined by the analysis of extracellular vesicles (EVs). EVs are lipid-bilayer enclosed structures released by all cell types containing a variety of molecules, including DNA, mRNA and miRNA. However, fast, efficient and a high degree of purity isolation technologies are necessary for their clinical routine implementation. In this work, the use of ExoGAG, a new easy-to-use EV isolation technology, was validated for the isolation of EVs from plasma and urine samples. After demonstrating its efficiency, an analysis of the genetic material contained in the EVs was carried out. Firstly, the sensitivity of the detection of point mutations in DNA from plasma EVs isolated by ExoGAG was analyzed. Then, a pilot study of mRNA expression using the nCounter NanoString platform in EV-mRNA from a healthy donor, a benign prostate hyperplasia patient and metastatic prostate cancer patient plasma and urine samples was performed, identifying the prostate cancer pathway as one of the main ones. This work provides evidence for the value of using ExoGAG for the isolation of EVs from plasma and urine samples, enabling downstream applications of the analysis of their genetic cargo.

Dynamic liquid biopsy components as predictive and prognostic biomarkers in colorectal cancer

Colorectal cancer (CRC) is one of the most common cancers worldwide. The diagnosis, prognosis and therapeutic monitoring of CRC depends largely on tissue biopsy. However, due to tumor heterogeneity and limitations such as invasiveness, high cost and limited applicability in longitudinal monitoring, liquid biopsy has gathered immense attention in CRC. Liquid biopsy has several advantages over tissue biopsy including ease of sampling, effective monitoring, and longitudinal assessment of treatment dynamics. Furthermore, the importance of liquid biopsy is signified by approval of several liquid biopsy assays by regulatory bodies indicating the powerful approach of liquid biopsy for comprehensive CRC screening, diagnostic and prognostics. Several liquid biopsy biomarkers such as novel components of the microbiome, non-coding RNAs, extracellular vesicles and circulating tumor DNA are extensively being researched for their role in CRC management. Majority of these components have shown promising results on their clinical application in CRC including early detection, observe tumor heterogeneity for treatment and response, prediction of metastases and relapse and detection of minimal residual disease. Therefore, in this review, we aim to provide updated information on various novel liquid biopsy markers such as a) oral microbiota related bacterial network b) gut microbiome-associated serum metabolites c) PIWI-interacting RNAs (piRNAs), microRNA(miRNAs), Long non-coding RNAs (lncRNAs), circular RNAs (circRNAs) and d) circulating tumor DNAs (ctDNA) and circulating tumor cells (CTC) for their role in disease diagnosis, prognosis, treatment monitoring and their applicability for personalized management of CRC.

Circulating tumor cells: biology and clinical significance

Circulating tumor cells (CTCs) are tumor cells that have sloughed off the primary tumor and extravasate into and circulate in the blood. Understanding of the metastatic cascade of CTCs has tremendous potential for the identification of targets against cancer metastasis. Detecting these very rare CTCs among the massive blood cells is challenging. However, emerging technologies for CTCs detection have profoundly contributed to deepening investigation into the biology of CTCs and have facilitated their clinical application. Current technologies for the detection of CTCs are summarized herein, together with their advantages and disadvantages. The detection of CTCs is usually dependent on molecular markers, with the epithelial cell adhesion molecule being the most widely used, although molecular markers vary between different types of cancer. Properties associated with epithelial-to-mesenchymal transition and stemness have been identified in CTCs, indicating their increased metastatic capacity. Only a small proportion of CTCs can survive and eventually initiate metastases, suggesting that an interaction and modulation between CTCs and the hostile blood microenvironment is essential for CTC metastasis. Single-cell sequencing of CTCs has been extensively investigated, and has enabled researchers to reveal the genome and transcriptome of CTCs. Herein, we also review the clinical applications of CTCs, especially for monitoring response to cancer treatment and in evaluating prognosis. Hence, CTCs have and will continue to contribute to providing significant insights into metastatic processes and will open new avenues for useful clinical applications.

Detection and clinical significance of circulating tumor cells in colorectal cancer

Histopathological examination (biopsy) is the "gold standard" for the diagnosis of colorectal cancer (CRC). However, biopsy is an invasive method, and due to the temporal and spatial heterogeneity of the tumor, a single biopsy cannot reveal the comprehensive biological characteristics and dynamic changes of the tumor. Therefore, there is a need for new biomarkers to improve CRC diagnosis and to monitor and treat CRC patients. Numerous studies have shown that "liquid biopsy" is a promising minimally invasive method for early CRC detection. A liquid biopsy mainly samples circulating tumor cells (CTCs), circulating tumor DNA (ctDNA), microRNA (miRNA) and extracellular vesicles (EVs). CTCs are malignant cells that are shed from the primary tumors and/or metastases into the peripheral circulation. CTCs carry information on both primary tumors and metastases that can reflect dynamic changes in tumors in a timely manner. As a promising biomarker, CTCs can be used for early disease detection, treatment response and disease progression evaluation, disease mechanism elucidation, and therapeutic target identification for drug development. This review will discuss currently available technologies for plasma CTC isolation and detection, their utility in the management of CRC patients and future research directions.

Clinical Applications of Circulating Tumor Cells and Circulating Tumor DNA as a Liquid Biopsy Marker in Colorectal Cancer

Simple Summary

Colorectal cancer is one of the most frequent malignant tumors worldwide and the spread of tumor cells through the blood circulation followed by the colonization of distant organs (“metastases”) is the main cause of cancer-related death. The blood is, therefore, an important fluid that can be explored for diagnostic purposes. Liquid biopsy is a new diagnostic concept defined as the analysis of circulating tumor cells or cellular products such as cell-free DNA in the blood or other body fluids of cancer patients. In this review, we summarize and discuss the latest findings using circulating tumor cells and cell-free DNA derived from tumor lesions in the blood of patients with colorectal cancer. Clinical applications include early detection of cancer, identification of patients with a high risk for disease progression after curative surgery, monitoring for disease progression in the context of cancer therapies, and discovery of mechanisms of resistance to therapy.

Abstract

Colorectal cancer (CRC) is the third most commonly diagnosed cancer worldwide. It is a heterogeneous tumor with a wide genomic instability, leading to tumor recurrence, distant metastasis, and therapy resistance. Therefore, adjunct non-invasive tools are urgently needed to help the current classical staging systems for more accurate prognostication and guiding personalized therapy. In recent decades, there has been an increasing interest in the diagnostic, prognostic, and predictive value of circulating cancer-derived material in CRC. Liquid biopsies provide direct non-invasive access to tumor material, which is shed into the circulation; this enables the analysis of circulating tumor cells (CTC) and genomic components such as circulating free DNA (cfDNA), which could provide the key for personalized therapy. Liquid biopsy (LB) allows for the identification of patients with a high risk for disease progression after curative surgery, as well as longitudinal monitoring for disease progression and therapy response. Here, we will review the most recent studies on CRC, demonstrating the clinical potential and utility of CTCs and ctDNA. We will discuss some of the advantages and limitations of LBs and the future perspectives in the field of CRC management.

Updates on liquid biopsy: current trends and future perspectives for clinical application in solid tumors

Despite advances in screening and therapeutics cancer continues to be one of the major causes of morbidity and mortality worldwide. The molecular profile of tumor is routinely assessed by surgical or bioptic samples, however, genotyping of tissue has inherent limitations: it represents a single snapshot in time and it is subjected to spatial selection bias owing to tumor heterogeneity. Liquid biopsy has emerged as a novel, non-invasive opportunity of detecting and monitoring cancer in several body fluids instead of tumor tissue. Circulating tumor cells (CTCs), circulating tumor DNA (ctDNA), RNA (mRNA and microRNA), microvesicles, including exosomes and tumor "educated platelets" were recently identified as a source of genomic information in cancer patients which could reflect all subclones present in primary and metastatic lesions allowing sequential monitoring of disease evolution. In this review, we summarize the currently available information concerning liquid biopsy in breast cancer, colon cancer, lung cancer and melanoma. These promising issues still need to be standardized and harmonized across laboratories, before fully adopting liquid biopsy approaches into clinical practice.

Mesenchymal Characteristics and Predictive Biomarkers on Circulating Tumor Cells for Therapeutic Strategy

Metastasis-related events are the primary cause of cancer-related deaths, and circulating tumor cells (CTCs) have a pivotal role in metastatic relapse. CTCs include a variety of subtypes with different functional characteristics. Interestingly, the epithelial-mesenchymal transition (EMT) markers expressed in CTCs are strongly associated with poor clinical outcome and related to the acquisition of circulating tumor stem cell (CTSC) features. Recent studies have revealed the existence of CTC clusters, also called circulating tumor microemboli (CTM), which have a high metastatic potential. In this review, we present current opinions regarding the clinical significance of CTCs and CTM with a mesenchymal phenotype as clinical surrogate markers, and we summarize the therapeutic strategy according to phenotype characterization of CTCs in various types of cancers for future precision medicine.

Genomic Instability in Circulating Tumor Cells

Simple Summary

In this review, we focus on recent advances in the detection and quantification of tumor cell heterogeneity and genomic instability of CTCs and the contribution of chromosome instability studies to genetic heterogeneity in CTCs at the single-CTC level.

Abstract

Circulating tumor cells (CTCs) can promote distant metastases and can be obtained through minimally invasive liquid biopsy for clinical assessment in cancer patients. Having both genomic heterogeneity and instability as common features, the genetic characterization of CTCs can serve as a powerful tool for a better understanding of the molecular changes occurring at tumor initiation and during tumor progression/metastasis. In this review, we will highlight recent advances in the detection and quantification of tumor cell heterogeneity and genomic instability in CTCs. We will focus on the contribution of chromosome instability studies to genetic heterogeneity in CTCs at the single-CTC level by discussing data from different cancer subtypes and their impact on diagnosis and precision medicine.

Liquid biopsies: Potential and challenges

The analysis of tumor cells or tumor cell products obtained from blood or other body fluids ("liquid biopsy" [LB]) provides a broad range of opportunities in the field of oncology. Clinical application areas include early detection of cancer or tumor recurrence, individual risk assessment and therapy monitoring. LB allows to portray the entire disease as tumor cells or tumor cell products are released from all metastatic or primary tumor sites, providing comprehensive and real-time information on tumor cell evolution, therapeutic targets and mechanisms of resistance to therapy. Here, we focus on the most prominent LB markers, circulating tumor cells (CTCs) and circulating tumor-derived DNA (ctDNA), in the blood of patients with breast, prostate, lung and colorectal cancer, as the four most frequent tumor types in Europe. After a brief introduction of key technologies used to detect CTCs and ctDNA, we discuss recent clinical studies on these biomarkers for early detection and prognostication of cancer as well as prediction and monitoring of cancer therapies. We also point out current methodological and biological limitations that still hamper the implementation of LB into clinical practice.

Liquid biopsy and tumor heterogeneity in metastatic solid tumors: the potentiality of blood samples

In a large number of cancer types, treatment selection depends on the presence of specific tumor biomarkers. Due to the dynamic nature of cancer, very often these predictive biomarkers are not uniformly present in all cancer cells. Tumor heterogeneity represents indeed one of the main causes of therapeutic failure, and its decoding remains a major ongoing challenge in the field.

Liquid biopsy is the sampling and analysis of non-solid biological tissue often through rapid and non-invasive methods, which allows the assessment in real-time of the evolving landscape of cancer. Samples can be obtained from blood and most other bodily fluids. A blood-based liquid biopsy can capture circulating tumor cells and leukocytes, as well as circulating tumor-derived nucleic acids.

In this review, we discuss the current and possibly future applications of blood-based liquid biopsy in oncology, its advantages and its limitations in clinical practice. We specifically focused on its role as a tool to capture tumor heterogeneity in metastatic cancer patients.

KRAS mutations by digital PCR in circulating tumor cells isolated from the mesenteric vein are associated with residual disease and overall survival in resected colorectal cancer patients

PURPOSE

In colorectal cancer (CRC), circulating tumor cells (CTCs) are released into the mesenteric veins (MV). We chose to determine whether KRAS mutations detected in CTCs from blood obtained at the time of surgery could be a marker of survival.

METHODS

From 52 surgically resected CRC patients who later relapsed, samples of tumor tissue, normal tissue, and blood from the peripheral vein (PV) and MV were obtained from each patient at the time of surgery. KRAS mutations were assessed by Sanger sequencing and digital PCR (DGPCR) in tissue samples and by DGPCR in CTCs. Mutant KRAS copy number was assessed in CTCs. Results were correlated with overall survival (OS).

RESULTS

Sanger sequencing detected KRAS mutations in ten tumor samples (19.2%), while DGPCR detected mutations in 30 (58%). Mutations were detected in CTCs in 21 MV samples (40.4%) and 18 PV samples (34.6%). Patients with G13D mutations in CTCs from the MV had shorter OS than those with G12D mutations (28.1 vs 54.6 months; p = 0.025). Patients with a high mutant KRAS copy number in CTCs had shorter OS than those with a low mutant KRAS copy number (MV: 20.5 vs 43.7 months; p = 0.002; PV: 15.1 vs 38.2 months; p = 0.027).

CONCLUSION

DGPCR is more efficient than Sanger sequencing for detecting KRAS mutations. KRAS G13D mutations and high mutant KRAS copy number are associated with shorter OS. The analysis of KRAS mutations in CTCs from blood obtained at the time of surgery can identify patients with a higher risk of relapse.

Perspectives of the Application of Liquid Biopsy in Colorectal Cancer

Colorectal cancer (CRC) is one of the most common gastrointestinal tumors and the second leading cause of cancer death worldwide. Since traditional biopsies are invasive and do not reflect tumor heterogeneity or monitor the dynamic progression of tumors, there is an urgent need for new noninvasive methods that can supplement and improve the current management strategies of CRC. Blood-based liquid biopsies are a promising noninvasive biomarker that can detect disease early, assist in staging, monitor treatment responses, and predict relapse and metastasis. Over time, an increasing number of experiments have indicated the clinical utility of liquid biopsies in CRC. In this review, we mainly focus on the development of circulating tumor cells and circulating tumor DNA as key components of liquid biopsies in CRC and introduce the potential of exosomal microRNAs as emerging liquid biopsy markers in clinical application for CRC.

Discovery of steroidal lactam conjugates of POPAM-NH2 with potent anticancer activity

Aim: Steroidal prodrugs of nitrogen mustards such as estramustine and prednimustine have proven effective anticancer agents in clinical use since the 1970s. In this work, we aimed to develop steroidal prodrugs of the novel nitrogen mustard POPAM-NH2. POPAM-NH2 is a melphalan analogue that was coupled with three different steroidal lactams. Methodology: The new conjugates were preclinically tested for anticancer activity against nine human and one rodent cancer experimental models, in vitro and in vivo. Results & conclusion: All the steroidal alkylators showed high antitumor activity, in vitro and in vivo, in the experimental systems tested. Moreover, these hybrid compounds showed by far superior anticancer activity compared with the alkylating agents, melphalan and POPAM-NH2.

Effect of FOLFOX on minimal residual disease in Stage III colon cancer and risk of relapse

Introduction

25% of Stage III colon cancer patients relapse within 5 years due to minimal residual disease (MRD) not eliminated by surgery and chemotherapy. We hypothesise that sub-types of MRD, defined by circulating tumour cells (CTCs) and bone marrow micro-metastasis (mM) have different types and kinetics of relapse.

Patients and Methods

One month of curative surgery and 1 month after completing six cycles of FOLFOX chemotherapy blood and bone marrow samples were taken to detect CTCs and mM using immunocytochemistry with anti-carcino-embryonic antigen (CEA). Follow up was up to 5 years or disease progression defined as new images on CT scanning. Survival curves using Kaplan–Meier (KM) and Restricted Mean Survival Time (RMST) were calculated for three prognostic groups: CTC and mM negative, CTC negative mM positive, and CTC positive.

Results

76 patients (39 men) participated, mean age 67 years, median follow-up 3.6 years. The response to chemotherapy was heterogeneous and MRD pre-treatment did not predict response to therapy. Of 21 patients MRD (−), 20 remained MRD negative and one patient became mM (+); of 21 patients mM (+), 10 became MRD (−), 8 remained the same and 3 became CTC (+); of the 34 CTC positive, 8 became MRD (−), 8 with only mM, and 18 remained positive.

After chemotherapy, 38 patients were negative for CTC and mM, 17 were positive for only mM, and 21 for CTCs. For the whole cohort, the 5 year KM was 58%, the median survival was not reached. For the three prognostic groups, the KM 5-year survivals were 87%, 58%, and 4%, respectively, the median survival for patients MRD negative and mM only was not reached. RMST for the whole cohort was 3.6 years, for the three prognostic groups the RMST was 4.6 years, 4.0 years, and 1.5 years, respectively. Serum CEA was significantly higher pre-surgery in the CTC positive group. There were no significant differences with respect to age or sex between the three groups.

Conclusions

MRD subtypes pre-chemotherapy did not predict treatment response. Post-chemotherapy MRD subtypes were associated with the pattern of failure and time to failure. MRD negative patients had an excellent prognosis with 87% disease-free survival at 5 years. Those with only mM had a similar outcome up to 2 years and then were at increasing risk of late failure. Patients who were CTC positive had a high risk of early failure. MRD subclassification may be useful to define the risk of relapse in Stage III colon cancer patients and warrants further studies with a larger number of patients.

Panitumumab-IRDye800CW for Fluorescence-Guided Surgical Resection of Colorectal Cancer

BACKGROUND

Fluorescence-guided surgery (FGS) is a rapidly advancing field that may improve outcomes in several cancer types. Although screening has decreased colorectal cancer (CRC) mortality, it remains a common and often fatal malignancy. In this study, we sought to identify an optical imaging agent for the application of FGS technology to CRC.

METHODS

We compared a panitumumab-IRDye800CW conjugate to an IgG-IRDye800CW isotype control. Mice were implanted with one of three CRC cell lines (LS174T, Colo205, and SW948) and imaged with open- and closed-filed fluorescence imaging systems. Fluorescent contrast was quantified by calculating the ratio between tumor and background fluorescence. After 10 d, the mice were sacrificed, and their tumors stained for microscopic imaging.

RESULTS

Panitumumab-IRDye800CW produced significantly greater (P < 0.05) fluorescent contrast in all three cell lines. Average tumor to background ratio was 6.00 versus 2.60 for LS174T, 5.78 versus 2.52 for Colo205, and 4.31 versus 1.70 for SW948. A 1-mg tumor fragment produced significantly greater fluorescent contrast in the Colo205 and SW948 cell lines in the panitumumab-IRDye800CW group. Western blotting for epidermal growth factor receptor (EGFR) and a semiquantitative analysis of EGFR expression noted strong expression in all three cell lines; however, EGFR expression did not directly correlate to tumor to background ratio.

CONCLUSIONS

Panitumumab-IRDye800CW produces significantly greater fluorescent contrast than IgG-IRDye800CW in a murine model of CRC and is a suitable agent for the application of FGS technology to CRC.

Molecular characteristics of circulating tumor cells resemble the liver metastasis more closely than the primary tumor in metastatic colorectal cancer

Background

CTCs are a promising alternative for metastatic tissue biopsies for use in precision medicine approaches. We investigated to what extent the molecular characteristics of circulating tumor cells (CTCs) resemble the liver metastasis and/or the primary tumor from patients with metastatic colorectal cancer (mCRC).

Results

The CTC profiles were concordant with the liver metastasis in 17/23 patients (74%) and with the primary tumor in 13 patients (57%). The CTCs better resembled the liver metastasis in 13 patients (57%), and the primary tumor in five patients (22%). The strength of the correlations was not associated with clinical parameters. Nine genes (CDH1, CDH17, CDX1, CEACAM5, FABP1, FCGBP, IGFBP3, IGFBP4, and MAPT) displayed significant differential expressions, all of which were downregulated, in CTCs compared to the tissues in the 23 patients.

Patients and Methods

Patients were retrospectively selected from a prospective study. Using the CellSearch System, CTCs were enumerated and isolated just prior to liver metastasectomy. A panel of 25 CTC-specific genes was measured by RT-qPCR in matching CTCs, primary tumors, and liver metastases. Spearman correlation coefficients were calculated and considered as continuous variables with r=1 representing absolute concordance and r= -1 representing absolute discordance. A cut-off of r>0.1 was applied in order to consider profiles to be concordant.

Conclusions

In the majority of the patients, CTCs reflected the molecular characteristics of metastatic cells better than the primary tumors. Genes involved in cell adhesion and epithelial-to-mesenchymal transition were downregulated in the CTCs. Our results support the use of CTC characterization as a liquid biopsy for precision medicine.

Circulating Tumor Cells as Cancer Biomarkers in the Clinic

It is believed that the development of metastatic cancer requires the presence of circulating tumor cells (CTCs) , which are found in a patient's circulation as rare abnormal cells comingled with billions of the normal red and white blood cells. The systems developed for detection of CTCs have brought progress to cancer treatment. The molecular characterization of CTCs can aid in the development of new drugs, and their presence during treatment can help clinicians determine the prognosis of the patient. Studies have been carried out in patients early in the disease course, with only primary tumors, and the role of CTCs in prognosis seems to be as important as it is in patients with metastatic disease. The published studies on CTCs have focused on their prognostic significance, their utility in real-time monitoring of therapies, the identification of therapeutic and resistance targets, and understanding the process of metastasis . The analysis of CTCs during the early stages, as a "liquid biopsy," helps to monitor patients at different points in the disease course, including minimal residual disease, providing valuable information about the very early assessment of treatment effectiveness. Finally, CTCs can be used to screen patients with family histories of cancer or with diseases that can lead to the development of cancer. With standard protocols, this easily obtained and practical tool can be used to prevent the growth and spread of cancer. In this chapter, we review some important aspects of CTCs , surveying the disease aspects where these cells have been investigated.

Detection of KRAS Exon 2 Mutations in Circulating Tumor Cells Isolated by the ISET System from Patients with RAS Wild Type Metastatic Colorectal Cancer

INTRODUCTION: The presence of KRAS mutations in patients with metastatic colorectal cancer (mCRC) predicts poor response to agents targeting the EGFR. Even in patients with RAS wild type (WT) tumors, resistance eventually develops due to multiple mechanisms, including the expansion of previously undetected KRAS mutated clones. In this feasibility study, we aimed to detect KRAS exon 2 mutations in serial samples of circulating tumor cells (CTCs) of RAS WT patients with mCRC captured by the Isolation by Size of Epithelial Tumor cells (ISET) system. METHODS: CTC isolation using the ISET system was performed from prospectively collected blood samples obtained from patients with RAS and BRAF WT mCRC prior to first-line therapy initiation, at first imaging assessment and on disease progression. CTCs were enumerated using hematoxylin & eosin and CD45 double stain on a single membrane spot. DNA was extracted from 5 spots and KRAS exon 2 mutations were detected using a custom quantitative Polymerase Chain Reaction (qPCR) assay. RESULTS: Fifteen patients were enrolled and 28 blood samples were analyzed. In 9 (60%) patients, at least one sample was positive for the presence of a KRAS exon 2 mutation. In 11 out of 28 samples (39.2%) with detectable CTCs a KRAS mutation was detected; the corresponding percentages for baseline and on progression samples were 27% and 37.5%, respectively. The most commonly detected mutations were G13D and G12C (n = 3). The presence of KRAS mutated CTCs at baseline was not prognostic for either PFS (P = .950) or OS (P = .383). CTC kinetics did not follow tumor response patterns. CONCLUSION: The results demonstrate that using a qPCR-based assay, KRAS exon 2 mutations could be detected in CTCs captured by the ISET system from patients with RAS WT primary tumors. However, the clinical relevance of these CTCs remains to be determined in future studies.

Circulating tumor cells: what we know, what do we want to know about them and are they ready to be used in clinics?

Circulating tumor cells (CTC) present in peripheral blood are assigned precursors of advanced tumor disease. Simplicity of blood withdrawal procedure adds practically an unlimited possibility of the CTC-monitoring and the advantages of the repeated biopsies over time. CTC got prognostic, predictive and diagnostic status with the technologic advance. Although the clinical utility of CTC has reached the high evidence, the significance of CTC testing was presented in the treatment strategy mostly with palliative intention. We report on the experiences with the CTC-testing in the CLIA-like laboratory working with the size-based CTC separation and in vitro culture. The data is presented in the form of case reports in patients with breast (BC), colorectal (CRC), prostate (PC) and lung cancer (NSCLC) to support the clinical utility of CTC during the neoadjuvant, adjuvant and palliative treatment. The presented findings support the evidence for liquid biopsy clinical implementation and enhance the ability of malignant disease monitoring and the treatment efficacy prediction.

Meta-analysis of the mutational status of circulation tumor cells and paired primary tumor tissues from colorectal cancer patients

As predictive markers for anti-EGFR therapy, KRAS and BRAF mutations are routinely detected in primary and metastatic colorectal cancer (CRC) cells, but seldom in circulating tumor cells (CTCs). Detecting mutations in CTCs could help explain mutational differences between tumor cells at local sites and distant metastases, thereby improving treatment outcomes. Here, we conducted a systematic review and meta-analysis to compare KRAS and BRAF mutations in paired CTCs and primary tumors from CRC patients, to detect any possible discordance. A total of 244 CRC patients from nine studies were included. Our subgroup meta-analysis demonstrated that the total odds ratio for mutations in CTCs was only 55% of that in primary tumors in the stage IV subgroup. We also found low heterogeneity among studies and differences in mutations between CTCs and primary tumors in the stage IV subgroup (I² = 0%, P = 0.01). We observed a higher frequency of KRAS mutations in CTCs than in primary tumors at early stages (I + II), a similar frequency in stage III, and a lower frequency in stage IV. There were also differences among the Epcam-targeted CTC enrichment, PCR-based mutation profiling, and ≥ 3 CTCs enriched (I² = 0%, P = 0.03) subgroups. These finding indicate mutational discordance between CTCs and primary CRCs, particularly in the stage IV and KRAS subgroups. We suggest large-sample studies stratified by clinical stage and KRAS subtype are urgently warranted to accurately evaluate mutational variations in CTCs compared to primary and metastatic CRC cells.

Deregulation of the miR-16-KRAS axis promotes colorectal cancer

KRAS plays a significant role in the etiology and progression of colorectal cancer (CRC), but the mechanism underlying this process has not been fully elucidated. In this study, we found that the KRAS protein levels were higher in CRC tissues than in the normal adjacent tissues, whereas its mRNA levels varied irregularly, suggesting that a post-transcriptional mechanism is involved in the regulation of KRAS. Then, we performed bioinformatic analyses to search for miRNAs that potentially target KRAS. We predicted and experimentally validated that miR-16 directly recognizes the 3'-UTR of the KRAS transcript and regulates KRAS expression. Furthermore, the in vitro results showed that the repression of KRAS by miR-16 suppressed the proliferation and invasion and induced the apoptosis of CRC cells, and the in vivo results revealed that miR-16 exerted a tumor-suppressive effect by negatively regulating KRAS in xenograft mice. Taken together, our findings provide evidence supporting the role of miR-16 as a tumor suppressor in CRC by targeting KRAS.

The biological complexity of colorectal cancer: insights into biomarkers for early detection and personalized care

Colorectal cancer has been ranked the third and second most prevalent of all cancers in men and women, respectively, and it represents the fourth most common cause of cancer deaths. In 2012, there were 1.4 million estimated cases of colorectal cancer worldwide, and 700,000 estimated deaths, which implies significant impact on public health, especially in economically-developed countries. In recent years, there has been an increase in the number of tumors, although this has been accompanied by decreased mortality, due to more appropriate and available information, earlier diagnosis, and improvements in treatment. Colorectal cancers are characterized by great genotypic and phenotypic heterogeneity, including tumor microenvironment and interactions between healthy and cancer cells. All of these traits confer a unique peculiarity to each tumor, which can thus be considered as an individual disease. Well conducted molecular and clinical characterization of each colorectal cancer is essential with a view to the implementation of precision oncology, and thus personalized care. This last aims at standardization of therapeutic plans chosen according to the genetic background of each specific neoplasm, to increase overall survival and reduce treatment side effects. Thus, prognostic and predictive molecular biomarkers assume a critical role in the characterization of colorectal cancer and in the determination of the most appropriate therapy.

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.

Evaluation and consequences of heterogeneity in the circulating tumor cell compartment

A growing understanding of the molecular biology of cancer and the identification of specific aberrations driving cancer evolution have led to the development of various targeted agents. Therapeutic decisions concerning these drugs are often guided by single biopsies of the primary tumor. Yet, it is well known that tumors can exhibit significant heterogeneity and change over time as a result of selective pressure. Circulating tumor cells (CTCs) are shed from various tumor sites and are thought to represent the molecular landscape of a patient's overall tumor burden. Moreover, a minimal-invasive liquid biopsy facilitates monitoring of clonal evolution during therapy pressure and disease progression in real-time. While more information becomes available regarding heterogeneity among CTCs, comparison between these studies is needed. In this review, we focus on the genomic and transcriptional heterogeneity found in the CTC compartment, and its significance for clinical decision making.

Prognostic Impact of Modulators of G proteins in Circulating Tumor Cells from Patients with Metastatic Colorectal Cancer

The consequence of a loss of balance between G-protein activation and deactivation in cancers has been interrogated by studying infrequently occurring mutants of trimeric G-protein α-subunits and GPCRs. Prior studies on members of a newly identified family of non-receptor guanine nucleotide exchange factors (GEFs), GIV/Girdin, Daple, NUCB1 and NUCB2 have revealed that GPCR-independent hyperactivation of trimeric G proteins can fuel metastatic progression in a variety of cancers. Here we report that elevated expression of each GEF in circulating tumor cells (CTCs) isolated from the peripheral circulation of patients with metastatic colorectal cancer is associated with a shorter progression-free survival (PFS). The GEFs were stronger prognostic markers than two other markers of cancer progression, S100A4 and MACC1, and clustering of all GEFs together improved the prognostic accuracy of the individual family members; PFS was significantly lower in the high-GEFs versus the low-GEFs groups [H.R = 5, 20 (95% CI; 2,15–12,57)]. Because nucleotide exchange is the rate-limiting step in cyclical activation of G-proteins, the poor prognosis conferred by these GEFs in CTCs implies that hyperactivation of G-protein signaling by these GEFs is an important event during metastatic progression, and may be more frequently encountered than mutations in G-proteins and/or GPCRs.

MiR-622 inhibited colorectal cancer occurrence and metastasis by suppressing K-Ras

Colorectal cancer (CRC) is one of the leading causes of cancer death worldwide, with many oncogenes and anti-oncogenes involved. MicroRNAs (miRNAs) are a class of small, noncoding RNA molecules that can adjust downstream targets. Accumulating evidence has revealed that microRNAs govern the occurrence and development of cancer. Here, we studied the role of miR-622 in CRC and clarified the underlying mechanism. We detected that miR-622 was down-regulated in colorectal tumor tissues and cell lines and that miR-622 was lower in metastatic CRC tissues compared with that in non-metastatic specimens. Furthermore, we confirmed that miR-622 inhibited tumor proliferation and migration in vitro. Through dual-luciferase reporter assay, we found kirsten rat sarcoma (K-Ras) gene was the direct target of miR-622. More importantly, K-Ras overexpression can rescue the inhibitory effect of miR-622 on CRC development. All these data were validated in colon xenograft tumor model. MiR-622-K-Ras signal pathway was a potentially new direction in the development of screening target and therapeutic treatments for CRC. © 2015 Wiley Periodicals, Inc.

EGF-Induced Acetylation of Heterogeneous Nuclear Ribonucleoproteins Is Dependent on KRAS Mutational Status in Colorectal Cancer Cells

KRAS mutational status is considered a negative predictive marker of the response to anti-EGFR therapies in colorectal cancer (CRC) patients. However, conflicting data exist regarding the variable response to EGFR-targeted therapy. The effects of oncogenic KRAS on downstream targets were studied in cell lines with different KRAS mutations. Cells harboring a single KRASG13D allele showed the most tumorigenic profile, with constitutive activation of the downstream pathway, rendering them EGF-unresponsive. Conversely, KRASA146T cells showed a full EGF-response in terms of signal transduction pathways, cell proliferation, migration or adhesion. Moreover, the global acetylome of CRC cells was also dependent on KRAS mutational status. Several hnRNP family members were identified within the 36 acetylated-proteins. Acetylation status is known to be involved in the modulation of EGF-response. In agreement with results presented herein, hnRNPA1 and L acetylation was induced in response to EGF in KRASA146T cells, whereas acetyl-hnRNPA1 and L levels remained unchanged after growth factor treatment in KRASG13D unresponsive cells. Our results showed that hnRNPs induced-acetylation is dependent on KRAS mutational status. Nevertheless hnRNPs acetylation might also be the point where different oncogenic pathways converge.

Colorectal Cancer Classification and Cell Heterogeneity: A Systems Oncology Approach

Colorectal cancer is a heterogeneous disease that manifests through diverse clinical scenarios. During many years, our knowledge about the variability of colorectal tumors was limited to the histopathological analysis from which generic classifications associated with different clinical expectations are derived. However, currently we are beginning to understand that under the intense pathological and clinical variability of these tumors there underlies strong genetic and biological heterogeneity. Thus, with the increasing available information of inter-tumor and intra-tumor heterogeneity, the classical pathological approach is being displaced in favor of novel molecular classifications. In the present article, we summarize the most relevant proposals of molecular classifications obtained from the analysis of colorectal tumors using powerful high throughput techniques and devices. We also discuss the role that cancer systems biology may play in the integration and interpretation of the high amount of data generated and the challenges to be addressed in the future development of precision oncology. In addition, we review the current state of implementation of these novel tools in the pathological laboratory and in clinical practice.

Progress of Circulating Tumor Cells in Cancer Management

Circulating tumor cells are low-frequency cells that are shed into the peripheral bloodstream from a primary solid tumor and/or metastasis. Although these cells were recognized initially in 1869, it is only in the past 2 decades that they have been isolated for use as a surrogate biomarker to monitor response to therapy, evaluate prognosis, detect tumor mutations, assist in selecting personalized medicine, and enable earlier cancer diagnosis.

Mutational analysis of circulating tumor cells from colorectal cancer patients and correlation with primary tumor tissue

Circulating tumor cells (CTCs) provide a non-invasive accessible source of tumor material from patients with cancer. The cellular heterogeneity within CTC populations is of great clinical importance regarding the increasing number of adjuvant treatment options for patients with metastatic carcinomas, in order to eliminate residual disease. Moreover, the molecular profiling of these rare cells might lead to insight on disease progression and therapeutic strategies than simple CTCs counting. In the present study we investigated the feasibility to detect KRAS, BRAF, CD133 and Plastin3 (PLS3) mutations in an enriched CTCs cell suspension from patients with colorectal cancer, with the hypothesis that these genes` mutations are of great importance regarding the generation of CTCs subpopulations. Subsequently, we compared CTCs mutational status with that of the corresponding primary tumor, in order to access the possibility of tumor cells characterization without biopsy. CTCs were detected and isolated from blood drawn from 52 colorectal cancer (CRC) patients using a quantum-dot-labelled magnetic immunoassay method. Mutations were detected by PCR-RFLP or allele-specific PCR and confirmed by direct sequencing. In 52 patients, discordance between primary tumor and CTCs was 5.77% for KRAS, 3.85% for BRAF, 11.54% for CD133 rs3130, 7.69% for CD133 rs2286455 and 11.54% for PLS3 rs6643869 mutations. Our results support that DNA mutational analysis of CTCs may enable non-invasive, specific biomarker diagnostics and expand the scope of personalized medicine for cancer patients.