Clinical significance of peripheral circulating tumor cell counts in colorectal polyps and non-metastatic colorectal cancer

How much do we know about the metastatic process?

Cancer cells can leave their primary sites and travel through the circulation to distant sites, where they lodge as disseminated cancer cells (DCCs), even during the early and asymptomatic stages of tumor progression. In experimental models and clinical samples, DCCs can be detected in a non-proliferative state, defined as cellular dormancy. This state can persist for extended periods until DCCs reawaken, usually in response to niche-derived reactivation signals. Therefore, their clinical detection in sites like lymph nodes and bone marrow is linked to poor survival. Current cancer therapy designs are based on the biology of the primary tumor and do not target the biology of the dormant DCC population and thus fail to eradicate the initial or subsequent waves of metastasis. In this brief review, we discuss the current methods for detecting DCCs and highlight new strategies that aim to target DCCs that constitute minimal residual disease to reduce or prevent metastasis formation. Furthermore, we present current evidence on the relevance of DCCs derived from early stages of tumor progression in metastatic disease and describe the animal models available for their study. We also discuss our current understanding of the dissemination mechanisms utilized by genetically less- and more-advanced cancer cells, which include the functional analysis of intermediate or hybrid states of epithelial-mesenchymal transition (EMT). Finally, we raise some intriguing questions regarding the clinical impact of studying the crosstalk between evolutionary waves of DCCs and the initiation of metastatic disease.

Circulating tumor cells in cancer-risk populations as a cancer interception tool

Cancer interception (CI) is a new approach to cancer prevention and treatment in a cancer-risk population that aims to detect and treat pre-tumoral stages. It has several potential advantages over traditional cancer diagnosis and monitoring methods because it is non-invasive, making it less painful and risky than conventional biopsy procedures. The circulating tumor cells (CTCs), liquid biopsy family members, are essential for the CI approach; then, the liquid biopsy (LB) is used as a CI tool. LB can be performed frequently because of its easy sampling and early pathological stages, which allow repeated non-invasive monitoring of cancer progression and response to treatment. CTCs have been found in the bloodstream of several types of cancer patients, including in early-stage cancer and premalignant lesions, suggesting a tumor development role in cancer's early stages. This chapter will present foundational scientific studies addressing CI and the clinical impact of CTC screening in a population at risk for cancer.

Exploring the Role of Circulating Cell-Free RNA in the Development of Colorectal Cancer

Circulating tumor RNA (ctRNA) has recently emerged as a novel and attractive liquid biomarker. CtRNA is capable of providing important information about the expression of a variety of target genes noninvasively, without the need for biopsies, through the use of circulating RNA sequencing. The overexpression of cancer-specific transcripts increases the tumor-derived RNA signal, which overcomes limitations due to low quantities of circulating tumor DNA (ctDNA). The purpose of this work is to present an up-to-date review of current knowledge regarding ctRNAs and their status as biomarkers to address the diagnosis, prognosis, prediction, and drug resistance of colorectal cancer. The final section of the article discusses the practical aspects involved in analyzing plasma ctRNA, including storage and isolation, detection technologies, and their limitations in clinical applications.

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.

Liquid Biopsy and Artificial Intelligence as Tools to Detect Signatures of Colorectal Malignancies: A Modern Approach in Patient's Stratification

Colorectal cancer (CRC) is the second most frequently diagnosed type of cancer and a major worldwide public health concern. Despite the global efforts in the development of modern therapeutic strategies, CRC prognosis is strongly correlated with the stage of the disease at diagnosis. Early detection of CRC has a huge impact in decreasing mortality while pre-lesion detection significantly reduces the incidence of the pathology. Even though the management of CRC patients is based on robust diagnostic methods such as serum tumor markers analysis, colonoscopy, histopathological analysis of tumor tissue, and imaging methods (computer tomography or magnetic resonance), these strategies still have many limitations and do not fully satisfy clinical needs due to their lack of sensitivity and/or specificity. Therefore, improvements of the current practice would substantially impact the management of CRC patients. In this view, liquid biopsy is a promising approach that could help clinicians screen for disease, stratify patients to the best treatment, and monitor treatment response and resistance mechanisms in the tumor in a regular and minimally invasive manner. Liquid biopsies allow the detection and analysis of different tumor-derived circulating markers such as cell-free nucleic acids (cfNA), circulating tumor cells (CTCs), and extracellular vesicles (EVs) in the bloodstream. The major advantage of this approach is its ability to trace and monitor the molecular profile of the patient's tumor and to predict personalized treatment in real-time. On the other hand, the prospective use of artificial intelligence (AI) in medicine holds great promise in oncology, for the diagnosis, treatment, and prognosis prediction of disease. AI has two main branches in the medical field: (i) a virtual branch that includes medical imaging, clinical assisted diagnosis, and treatment, as well as drug research, and (ii) a physical branch that includes surgical robots. This review summarizes findings relevant to liquid biopsy and AI in CRC for better management and stratification of CRC patients.

Interrogating the interplay of angiogenesis and immunity in metastatic colorectal cancer

Colon cancer is the third most common malignancy and the fifth most frequent cause of death from neoplastic disease worldwide. At the time of diagnosis, more than 20% of patients already have metastatic disease. In the last 20 years, the natural course of the disease has changed due to major changes in the management of metastatic disease such as the advent of novel surgical and local therapy approaches as well as the introduction of novel chemotherapy drugs and targeted agents such as anti-epidermal growth factor receptor, anti-BRAF and antiangiogenics. Angiogenesis is a complex biological process of new vessel formation from existing ones and is an integral component of tumor progression supporting cancer cells to grow, proliferate and metastasize. Many molecules are involved in this proangiogenic process, such as vascular endothelial growth factor and its receptors on endothelial cells. A well-standardized methodology that is applied to assess angiogenesis in the tumor microenvironment is microvascular density by using immunohistochemistry with antibodies against endothelial CD31, CD34 and CD105 antigens. Even smaller molecules, such as the microRNAs, which are small non-coding RNAs, are being studied for their usefulness as surrogate biomarkers of angiogenesis and prognosis. In this review, we will discuss recent advances regarding the investigation of angiogenesis, the crosstalk between elements of the immune microenvironment and angiogenesis and how a disorganized tumor vessel network affects the trafficking of CD8+ T cells in the tumor bed. Furthermore, we will present recent data from clinical trials that combine antiangiogenic therapies with immune checkpoint inhibitors in colorectal cancer.

Deep Phenotypic Characterisation of CTCs by Combination of Microfluidic Isolation (IsoFlux) and Imaging Flow Cytometry (ImageStream)

Simple Summary

Cells that escape the primary tumour and have the potential ability to colonise distant organs through metastasis are called circulating tumour cells (CTCs). The study of CTCs in colorectal cancer (CRC) has demonstrated their prognostic utility, although current methodologies only allow the evaluation of CTC numbers and a maximum of two markers. Here, we developed a novel protocol for the isolation and characterisation of CTCs by combining two existing technologies. This new methodology allows the simultaneous evaluation of multiple markers and parameters. In particular, we evaluated the expression of a mutant protein (BRAF^V600E) associated with poor response to therapies against EGFR and the expression of PD-L1, a marker for immunotherapy. Based on these markers, we evaluated the CTCs (positive for cytokeratin) of 16 early CRC patients and demonstrated the suitability of our protocol to classify patients into potential responders and non-responders.

Abstract

The isolation of circulating tumour cells (CTCs) in colorectal cancer (CRC) mostly relies on the expression of epithelial markers such as EpCAM, and phenotypic characterisation is usually performed under fluorescence microscopy with only one or two additional markers. This limits the ability to detect different CTC subpopulations based on multiple markers. The aim of this work was to develop a novel protocol combining two platforms (IsoFlux^TM and ImageStream^®X) to improve CTC evaluation. Cancer cell lines and peripheral blood from healthy donors were used to evaluate the efficiency of each platform independently and in combination. Peripheral blood was extracted from 16 early CRC patients (before loco-regional surgery) to demonstrate the suitability of the protocol for CTC assessment. Additionally, peripheral blood was extracted from nine patients one month after surgery to validate the utility of our protocol for identifying CTC subpopulation changes over time. Results: Our protocol had a mean recovery efficiency of 69.5% and a limit of detection of at least four cells per millilitre. We developed an analysis method to reduce noise from magnetic beads used for CTC isolation. CTCs were isolated from CRC patients with a median of 37 CTCs (IQ 13.0–85.5) at baseline. CTCs from CRC patients were significantly (p < 0.0001) larger than cytokeratin (CK)-negative cells, and patients were stratified into two groups based on BRAF^V600E and PD-L1 expression on CK-positive cells. The changes observed over time included not only the number of CTCs but also their distribution into four different subpopulations defined according to BRAF^V600E and PD-L1 positivity. We developed a novel protocol for semi-automatic CTC isolation and phenotypic characterisation by combining two platforms. Assessment of CTCs from early CRC patients using our protocol allowed the identification of two clusters of patients with changing phenotypes over time.

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.

Analytical validation of the CellMax platform for early detection of cancer by enumeration of rare circulating tumor cells

The CellMax (CMx®) platform was developed to enrich for epithelial circulating tumor cells (CTCs) in the whole blood. This report provides assay performance data, including accuracy, linearity, limit of blank, limit of detection (LOD), specificity, and precision of enumeration of cancer cell line cells (CLCs) spiked in cell culture medium or healthy donor blood samples. Additionally, assay specificity was demonstrated in 32 young healthy donors and clinical feasibility was demonstrated in a cohort of 47 subjects consisting of healthy donors and patients who were colonoscopy verified to have colorectal cancer, adenomas, or a negative result. The CMx platform demonstrated high accuracy, linearity, and sensitivity for the enumeration of all CLC concentrations tested, including the extremely low range of 1 to 10 cells in 2 mL of blood, which is most relevant for early cancer detection. Theoretically, the assay LOD is 0.71 CTCs in 2 mL of blood. The analytical specificity was 100% demonstrated using 32 young healthy donor samples. We also demonstrated precision across multiple days and multiple operators, with good reproducibility of recovery efficiency. In a clinical feasibility study, the CMx platform identified 8 of 10 diseased subjects as positive (80% clinical sensitivity) and 4 of 5 controls as negative (80% clinical specificity). We also compared processing time and transportation effects for similar blood samples from two different sites and assessed an artificial intelligence-based counting method. Finally, unlike other platforms for which captured CTCs are retained on ferromagnetic beads or tethered to the slide surface, the CMx platform's unique airfoam-enabled release of CTCs allows captured cells to be transferred from a microfluidic chip to an Eppendorf tube, enabling a seamless transition to downstream applications such as genetic analyses and live cell manipulations.

The application of nano-enrichment in CTC detection and the clinical significance of CTCs in non-small cell lung cancer (NSCLC) treatment

Circulating tumor cells (CTCs) are an independent prognostic marker in non-small cell lung cancer (NSCLC). CTC numbers are closely related to early diagnosis, clinical stage, therapy surveillance, and prognosis of NSCLC. We used a more efficient nano-enrichment method to detect CTCs in NSCLC patients and explored the clinical value of CTCs. The results showed that CTC numbers in stage IV cases were significantly higher than those in stage I, II or III cases. The number of CTCs in poorly-differentiated cases was significantly higher than that in well-differentiated cases. During six chemotherapy cycles, the average CTC number decreased from 5.8/7.5 ml in cycle #1 to 2.4/7.5 ml in cycle #4 and remained at almost the same level from 4 to 6 cycles. CTC numbers in patients with EGFR mutations was significantly higher than those in patients with no mutations. The average progression free survival (PFS) in the favorable group (CTC ≤ 5/7.5 ml) was 11.3 months, which was longer than that in the unfavorable group (CTC > 5/7.5 ml, 7.2 months). In conclusion, the assessment of NSCLC cannot be performed using a single CTC analysis. The clinical value is more significant in the continuous analysis of CTC data, as well as the cross-validation of other indexes and imaging results.

Prognostic significance of circulating tumor cells (CTCs) in Egyptian non-metastatic colorectal cancer patients: A comparative study for four different techniques of detection (Flowcytometry, CellSearch, Quantitative Real-time PCR and Cytomorphology)

PURPOSE

We assessed CTCs counts in NMCRC patients using four different techniques.

METHODS

CTCs were detected in 63 NMCRC patients, 40 benign bowel diseases (BBD) and 40 normal controls (NC) using, flow-cytometry (FCM), CellSearch (CS), cytomorphology and quantitative real time (qPCR) for CK19, MUC1, CD44, CD133, ALDH1 expression. Results were correlated to progression free (PFS) and overall (OS).

RESULTS

Positive CTCs (≥4 cells /7.5 mL blood) were detected in 50.8% (32/63) NMCRC by FCM and 7.5% (3/40) BBD (p < .001). CTCs were detected in 34/63 (54%) NMCRC, 4/40 (10%) BBD (p < .001) by CS. CK19, MUC1, CD44, CD133 and ALDH1 were expressed in 35 (55.6%), 29 (46.0%), 28 (44.4%), 26 (41.3%) and 25 (41.3%) cases of NMCRC. In BBD 4/40 (10%) cases expressed CK19, MUC1 and CD44, while 2/40 (5%) expressed CD133. Cytomorphology showed the lowest sensitivity (47.6%) and specificity (90%) for CTCs detection. The combined use of FCM or CS with CTCs-mRNA markers improved the sensitivity and specificity to 68.3%, and 95.0%; respectively. Positive CTCs and mRNA markers expression were significantly associated with shorter 5-yr PFS and OS. In multivariate analysis, CTCs mRNA markers were independent prognostic factors for PFS and OS.

CONCLUSIONS

Enumeration of CTCs by FCM and RNA expression for specific colon cancer markers are comparable to CS regarding sensitivity and specificity. CTCs also represent novel therapeutic targets for NMCRC cases.

An update of circulating rare cell types in healthy adult peripheral blood: findings of immature erythroid precursors

Background

Circulating rare cells (CRCs) are benign or malignant minuscule events in the peripheral blood or other bodily fluids. The detection and quantification of certain CRC types is an invaluable or proposed candidate biomarker for diagnosis, prognosis and prediction of various pathological conditions. The list of CRC types and biomarker applicability thereof continues to expand along with improvements in cell selection technology. Past findings may suggest commonness of healthy donor peripheral blood circulating mature erythroblasts. This work suggests the occurrence of morphologically distinct bone marrow native circulating early erythroid precursors that we intend to add to the list of CRCs.

Methods

We tested 15 healthy individuals that varied in age and gender employing a negative cell selection assay based on magnetic bead technology to characterize healthy adult circulating CD45 negative cell events using cell surface markers CD71 and glycophorin-A.

Results

Positive events were detected and varied in cell and nuclear size ranging between 7.5 µm till 15 µm and 4.5 till 9.2 µm, respectively with distinct appearance under bright field microscope. Cell rarity increased with cell and nuclear size. Largest cells exceeded 13.5 µm in cell diameter and were found in 7 out of 15 donors.

Conclusions

Circulating erythroid precursors occur at different stages of maturation and may be part of the benign CRC spectrum.