PD-L1 Expression with Epithelial Mesenchymal Transition of Circulating Tumor Cells Is Associated with Poor Survival in Curatively Resected Non-Small Cell Lung Cancer

A comparative study of circulating tumor cell isolation and enumeration technologies in lung cancer

Circulating tumor cells (CTCs) have potential as diagnostic, prognostic, and predictive biomarkers in solid tumors. Despite Food and Drug Administration (FDA) approval of CTC devices in various cancers, the rarity and heterogeneity of CTCs in lung cancer make them technically challenging to isolate and analyze, hindering their clinical integration. Establishing a consensus through comparative analysis of different CTC systems is warranted. This study aimed to evaluate seven different CTC enrichment methods across five technologies using a standardized spike-in protocol: the CellMag™ (EpCAM-dependent enrichment), EasySep™ and RosetteSep™ (blood cell depletion), and the Parsortix® PR1 and the new design Parsortix® Prototype (PP) (size- and deformability-based enrichment). The Parsortix® systems were also evaluated for any differences in recovery rates between cell harvest versus in-cassette staining. Healthy donor blood (5 mL) was spiked with 100 fluorescently labeled EpCAMhigh H1975 cells, processed through each system, and the isolation efficiency was calculated. The CellMag™ had the highest recovery rate (70 ± 14%), followed by Parsortix® PR1 in-cassette staining, while the EasySep™ had the lowest recovery (18 ± 8%). Additional spike-in experiments were performed with EpCAMmoderate A549 and EpCAMlow H1299 cells using the CellMag™ and Parsortix® PR1 in-cassette staining. The recovery rate of CellMag™ significantly reduced to 35 ± 14% with A549 cells and 1 ± 1% with H1299 cells. However, the Parsortix® PR1 in-cassette staining showed cell phenotype-independent and consistent recovery rates among all lung cancer cell lines: H1975 (49 ± 2%), A549 (47 ± 10%), and H1299 (52 ± 10%). Furthermore, we demonstrated that the Parsortix® PR1 in-cassette staining method is capable of isolating heterogeneous single CTCs and cell clusters from patient samples. The Parsortix® PR1 in-cassette staining, capable of isolating different phenotypes of CTCs as either single cells or cell clusters with consistent recovery rates, is considered optimal for CTC enrichment for lung cancer, albeit needing further optimization and validation.

Linking EMT Status of Circulating Tumor Cells to Clinical Outcomes in Lung Cancer

Background

Lung cancer (LC) remains a leading cause of cancer-related mortality worldwide, with its prognosis influenced by complex biological factors.

Objective

This study delves into the clinical relevance of circulating tumor cells (CTCs) and their Epithelial-Mesenchymal Transition (EMT) status in LC patients.

Methods

We enrolled 30 newly diagnosed LC patients and utilized the CanPatrol technique for the separation and categorization of CTCs from peripheral blood samples. Immunofluorescent staining identified epithelial (CK8/18/19, EpCAM), mesenchymal (Vimentin, Twist), and leukocyte (CD45) markers in these cells. Fluorescence microscopy analyzed the slides, and RECIST 1.1 criteria assessed treatment response. Spearman's method was used to correlate CTCs' EMT states with their count and clinical characteristics.

Results

Our findings reveal three distinct CTC groups: epithelial (E-CTCs), hybrid epithelial/mesenchymal (E/M-CTCs), and mesenchymal (M-CTCs). Significant statistical differences were observed in stages III-IV vs I-II, tumor sizes T3-T4 vs T1-T2, and in the presence or absence of distant metastasis and lymph node involvement. Notably, the count of E/M-CTCs was positively correlated with TNM staging, tumor size, lymph node, and distant metastasis. Changes in M-CTC count pre- and post-treatment closely mirrored disease progression and control, showing considerable consistency with RECIST criteria.

Conclusion

In conclusion, the EMT status of CTCs, especially E/M-CTCs, holds predictive value for LC staging, tumor size, and metastasis. Dynamic monitoring of M-CTCs can accurately reflect disease progression.

scRNAseq and High-Throughput Spatial Analysis of Tumor and Normal Microenvironment in Solid Tumors Reveal a Possible Origin of Circulating Tumor Hybrid Cells

Metastatic cancer is a leading cause of death in cancer patients worldwide. While circulating hybrid cells (CHCs) are implicated in metastatic spread, studies documenting their tissue origin remain sparse, with limited candidate approaches using one-two markers. Utilizing high-throughput single-cell and spatial transcriptomics, we identified tumor hybrid cells (THCs) co-expressing epithelial and macrophage markers and expressing a distinct transcriptome. Rarely, normal tissue showed these cells (NHCs), but their transcriptome was easily distinguishable from THCs. THCs with unique transcriptomes were observed in breast and colon cancers, suggesting this to be a generalizable phenomenon across cancer types. This study establishes a framework for HC identification in large datasets, providing compelling evidence for their tissue residence and offering comprehensive transcriptomic characterization. Furthermore, it sheds light on their differential function and identifies pathways that could explain their newly acquired invasive capabilities. THCs should be considered as potential therapeutic targets.

Immune checkpoints between epithelial-mesenchymal transition and autophagy: A conflicting triangle

Inhibitory immune checkpoint (ICP) molecules are pivotal in inhibiting innate and acquired antitumor immune responses, a mechanism frequently exploited by cancer cells to evade host immunity. These evasion strategies contribute to the complexity of cancer progression and therapeutic resistance. For this reason, ICP molecules have become targets for antitumor drugs, particularly monoclonal antibodies, collectively referred to as immune checkpoint inhibitors (ICI), that counteract such cancer-associated immune suppression and restore antitumor immune responses. Over the last decade, however, it has become clear that tumor cell-associated ICPs can also induce tumor cell-intrinsic effects, in particular epithelial-mesenchymal transition (EMT) and macroautophagy (hereafter autophagy). Both of these processes have profound implications for cancer metastasis and drug responsiveness. This article reviews the positive or negative cross-talk that tumor cell-associated ICPs undergo with autophagy and EMT. We discuss that tumor cell-associated ICPs are upregulated in response to the same stimuli that induce EMT. Moreover, ICPs themselves, when overexpressed, become an EMT-inducing stimulus. As regards the cross-talk with autophagy, ICPs have been shown to either stimulate or inhibit autophagy, while autophagy itself can either up- or downregulate the expression of ICPs. This dynamic equilibrium also extends to the autophagy-apoptosis axis, further emphasizing the complexities of cellular responses. Eventually, we delve into the intricate balance between autophagy and apoptosis, elucidating its role in the broader interplay of cellular dynamics influenced by ICPs. In the final part of this article, we speculate about the driving forces underlying the contradictory outcomes of the reciprocal, inhibitory, or stimulatory effects between ICPs, EMT, and autophagy. A conclusive identification of these driving forces may allow to achieve improved antitumor effects when using combinations of ICIs and compounds acting on EMT and/or autophagy. Prospectively, this may translate into increased and/or broadened therapeutic efficacy compared to what is currently achieved with ICI-based clinical protocols.

Meta-Analysis of Circulating Tumor Cell PD-L1 Expression and the Association with Clinical Outcomes in Non-Small Cell Lung Cancer

BACKGROUND

Programmed death ligand-1 (PD-L1) expression on circulating tumor cells (CTCs) has been suggested to provide prognostic information in non-small cell lung cancer (NSCLC), but consensus relative to treatment outcomes is lacking. We conducted the first comprehensive meta-analysis exploring its potential as a prognostic and predictive marker, and assessed the concordance between PD-L1 + CTCs and paired tumor tissue in NSCLC patients.

METHOD

A comprehensive search was applied to PubMed and EMBASE to identify 26 studies that evaluated PD-L1 + CTCs and their association with survival outcomes in 1236 NSCLC patients.

RESULTS

The meta-analysis estimated a mean PD-L1 + CTCs detection rate of 61% (95% CI, 49-72). Subgroup analysis based on treatment showed that PD-L1 + CTCs was not significantly associated with better overall survival (OS) in NSCLC patients treated with immune checkpoint inhibitors (ICIs) (Hazard Ratio (HR) = 0.96, 95% CI, 0.35-2.65, P = 0.944), but was predictive of worse OS in those treated with other therapies (HR = 2.11, 95% CI, 1.32-3.36, P = 0.002). Similarly, PD-L1 + CTCs was not significantly associated with superior progressing free survival (PFS) in NSCLCs treated with ICIs (HR = 0.67, 95% CI, 0.41-1.09, P = 0.121), but was significantly associated with shorter PFS in patients treated with other therapies (HR = 1.91, 95% CI, 1.24-2.94, P = 0.001). The overall estimate for the concordance between PD-L1 expression on CTCs and tumor cells was 63% (95% CI, 44-80).

CONCLUSION

The average detection rate of PD-L1 + CTCs was comparable to the rate of PD-L1 expression in NSCLC tumors. There was a trend towards better PFS in ICI-treated NSCLC patients with PD-L1 + CTCs. Larger longitudinal studies on the association of PD-L1 + CTCs with clinical outcomes in NSCLC patients treated with ICIs are warranted.

Circulating tumor cells in gastric cancer: developments and clinical applications

Circulating tumor cells (CTCs), which are shed from primary tumor or metastatic sites into the bloodstream and subsequently seed into distant tissues, are considered as the precursors of metastases. Gastric cancer (GC) is a highly heterogeneous malignant tumor. With regard to the diagnosis of GC, secondary pathological biopsy is difficult, while invasive examination is harmful to patients. In recent years, CTCs have made great progress in tumor diagnosis, prognosis prediction, efficacy detection and treatment guidance, but the research on the role of CTCs in GC remains limited. The following sections review the landmark studies demonstrating the technical approaches of CTCs monitoring in the field of GC. Moreover, we highlight the clinical application of CTCs numbers and phenotypes in monitoring the therapeutic efficacy and judging patient prognosis by sequential blood analyses.

Diagnostic value of programmed cell death-ligand 1 expression on circulating tumor cells in lung cancer: A systematic review and meta-analysis

The expression of programmed cell death-ligand 1 (PD-L1) on circulating tumor cells offers a noninvasive method for the detection of PD-L1 expression in lung cancer, and could serve as a potential surrogate for cancer tissue. However, discrepant results make it difficult to apply PD-L1 on circulating tumor cells to clinical practice. Therefore, we conducted a meta-analysis to investigate the diagnostic value of PD-L1 on circulating tumor cells in lung cancer. To identify the relationship between the expression of PD-L1 on circulating tumor cells and lung cancer, the PubMed, Web of Science, Embase, China National Knowledge Infrastructure, and Wanfang databases were searched from inception to March 2023. The pooled sensitivity, specificity, positive likelihood ratio, negative likelihood ratio, diagnostic odds ratio, and the corresponding 95% confidence intervals were calculated to assess the diagnostic performance of PD-L1. We also conducted subgroup and sensitivity analyses. A total of 11 studies including 472 lung cancer patients were included in our study. The overall performance in terms of pooled sensitivity and specificity was 0.72 (0.52-0.86) and 0.54 (0.25-0.81), respectively. The positive likelihood ratio, negative likelihood ratio, and area under the curve were 1.57 (0.87-2.84), 0.52 (0.30-0.90), and 0.70 (0.66-0.74), respectively. Deeks' funnel plot test indicated no publication bias. Our analysis demonstrated that positive PD-L1 expression on circulating tumor cells (CTCs) exhibited a moderate diagnostic value in lung cancer, and CTCs may serve as a feasible alternative tissue analysis for the detection of PD-L1 in lung cancer.

Prognostic significance of programmed cell death-ligand 1 expression on immune cells and epithelial-mesenchymal transition expression in patients with hepatocellular carcinoma

Purpose

Immune checkpoint inhibitors (ICIs) have been shown significant oncological improvements in several cancers. However, ICIs are still in their infancy in hepatocellular carcinoma (HCC). Programmed cell death-ligand 1 (PD-L1), tumor-infiltrating lymphocytes (TILs), and epithelial-mesenchymal transition (EMT) have been known as prognostic factors in HCC. Therefore, we have focused on identifying the molecular mechanisms between each marker to evaluate a predictive role.

Methods

Formalin-fixed paraffin-embedded samples were obtained from 166 patients with HCC who underwent surgery. The expression of PD-L1 and TILs and EMT marker were evaluated by immunohistochemical analysis.

Results

The multivariate analysis showed that TIL expression (hazard ratio [HR], 0.483; 95% confidence interval [CI], 0.269-0.866; P = 0.015) were independent prognostic factors for overall survival. The prognostic factors for disease-free survival were EMT marker expression (HR, 1.565; 95% CI, 1.019-2.403; P = 0.005). Patients with high expression of TILs had significantly better survival compared to patients with low expression (P = 0.023). Patients who were TIL+/EMT- showed a significantly better prognosis than those who were TIL-/EMT+ (P = 0.049).

Conclusion

This study demonstrates that PD-L1 expression of TILs is closely associated with EMT marker expression in HCC. Clinical investigations using anti-PD-1/PD-L1 inhibitors in patients with EMT-associated PD-L1 upregulation are warranted.

A Review of Biomarkers and Their Clinical Impact in Resected Early-Stage Non-Small-Cell Lung Cancer

The postoperative survival of early-stage non-small-cell lung cancer (NSCLC) patients remains unsatisfactory. In this review, we examined the relevant literature to ascertain the prognostic effect of related indicators on early-stage NSCLC. The prognostic effects of the epidermal growth factor receptor (EGFR), anaplastic lymphoma kinase (ALK), mesenchymal-epithelial transition (MET), C-ros oncogene 1 (ROS1), or tumour protein p53 (TP53) alterations in resected NSCLC remains debatable. Kirsten rat sarcoma viral oncogene homologue (KRAS) alterations indicate unfavourable outcomes in early-stage NSCLC. Meanwhile, adjuvant or neoadjuvant EGFR-targeted agents can substantially improve prognosis in early-stage NSCLC with EGFR alterations. Based on the summary of current studies, resected NSCLC patients with overexpression of programmed death-ligand 1 (PD-L1) had worsening survival. Conversely, PD-L1 or PD-1 inhibitors can substantially improve patient survival. Considering blood biomarkers, perioperative peripheral venous circulating tumour cells (CTCs) and pulmonary venous CTCs predicted unfavourable prognoses and led to distant metastases. Similarly, patients with detectable perioperative circulating tumour DNA (ctDNA) also had reduced survival. Moreover, patients with perioperatively elevated carcinoembryonic antigen (CEA) in the circulation predicted significantly worse survival outcomes. In the future, we will incorporate mutated genes, immune checkpoints, and blood-based biomarkers by applying artificial intelligence (AI) to construct prognostic models that predict patient survival accurately and guide individualised treatment.

Gene-network analysis predicts clinical response to immunotherapy in patients affected by NSCLC

OBJECTIVES

Predictive biomarkers of response to immune checkpoint inhibitors (ICIs) have been extensively studied in non-small cell lung cancer (NSCLC) with controversial results. Recently, gene-network analysis emerged as a new tool to address tumor biology and behavior, representing a potential tool to evaluate response to therapies.

METHODS

Clinical data and genetic profiles of 644 advanced NSCLCs were retrieved from cBioPortal and the Cancer Genome Atlas (TCGA); 243 ICI-treated NSCLCs were used to identify an immunotherapy response signatures via mutated gene network analysis and K-means unsupervised clustering. Signatures predictive values were tested in an external dataset of 242 cases and assessed versus a control group of 159 NSCLCs treated with standard chemotherapy.

RESULTS

At least two mutations in the coding sequence of genes belonging to the chromatin remodelling pathway (A signature), and/or at least two mutations of genes involved in cell-to-cell signalling pathways (B signature), showed positive prediction in ICI-treated advanced NSCLC. Signatures performed best when combined for patients undergoing first-line immunotherapy, and for those receiving combined ICIs.

CONCLUSIONS

Alterations in genes related to chromatin remodelling complexes and cell-to-cell crosstalk may force dysfunctional immune evasion, explaining susceptibility to immunotherapy. Therefore, exploring mutated gene networks could be valuable for determining essential biological interactions, contributing to treatment personalization.

Detection and Molecular Characterization of Circulating Tumour Cells: Challenges for the Clinical Setting

Over the last decade, liquid biopsy has gained much attention as a powerful tool in personalized medicine since it enables monitoring cancer evolution and follow-up of cancer patients in real time. Through minimally invasive procedures, liquid biopsy provides important information through the analysis of circulating tumour cells (CTCs) and circulating tumour-derived material, such as circulating tumour DNA (ctDNA), circulating miRNAs (cfmiRNAs) and extracellular vehicles (EVs). CTC analysis has already had an important impact on the prognosis, detection of minimal residual disease (MRD), treatment selection and monitoring of cancer patients. Numerous clinical trials nowadays include a liquid biopsy arm. CTC analysis is now an exponentially expanding field in almost all types of solid cancers. Functional studies, mainly based on CTC-derived cell-lines and CTC-derived explants (CDx), provide important insights into the metastatic process. The purpose of this review is to summarize the latest findings on the clinical significance of CTCs for the management of cancer patients, covering the last four years. This review focuses on providing a comprehensive overview of CTC analysis in breast, prostate and non-small-cell lung cancer. The unique potential of CTC single-cell analysis for understanding metastasis biology, and the importance of quality control and standardization of methodologies used in this field, is also discussed.

Preclinical models to study patient-derived circulating tumor cells and metastasis

Circulating tumor cells (CTCs) that are detached from the tumor can be precursors of metastasis. The majority of studies focus on enumeration of CTCs from patient blood to predict recurrence and therapy outcomes. Very few studies have managed to expand CTCs to investigate their functional dynamics with respect to genetic changes, tumorigenic potential, and response to drug treatment. A growing amount of evidence based on successful CTC expansion has revealed novel therapeutic targets that are associated with the process of metastasis. In this review, we summarize the successes, challenges, and limitations that collectively contribute to the better understanding of metastasis using patient-derived CTCs as blood-borne seeds of metastasis. The roadblocks and future avenues to move CTC-based scientific discoveries forward are also discussed.

Genetic analysis of heterogeneous subsets of circulating tumour cells from high grade serous ovarian carcinoma patients

Circulating tumour cells (CTCs) are heterogenous and contain genetic information from the tumour of origin. They bear specific intra- and extra-cellular protein markers aiding in their detection. However, since these markers may be shared with other rare cells in the blood, only genetic testing can confirm their malignancy. Herein, we analyse different CTC subsets using single cell whole genome DNA sequencing to validate their malignant origin. We randomly selected putative CTCs identified by immunostaining that were isolated from 4 patients with high grade serous ovarian cancer (HGSOC) and one with benign cystadenoma. We specifically targeted CTCs positive for epithelial (CK/EpCAM^pos), mesenchymal (vimentin^pos), and pseudoendothelial (CK/EpCAM^pos plus CD31^pos) markers. We isolated these cells and performed whole genome amplification (WGA) and low-pass whole-genome sequencing (LP-WGS) for analysis of copy number alterations (CNA). Of the CK/EpCAM^pos cells analysed from the HGSOC patients, 2 of 3 cells showed diverse chromosomal CNAs. However, the 4 pseudoendothelial cells (CK/EpCAM^pos plus CD31^pos) observed in the HGSOC cases did not carry any CNA. Lastly, two of the clusters of vimentin positive cells sequenced from those found in the benign cystadenoma case had CNA. Despite the low number of cells analysed, our results underscore the importance of genetic analysis of putative CTCs to confirm their neoplastic origin. In particular, it highlights the presence of a population of CK/EpCAM^pos cells that are not tumour cells in patients with HGSOC, which otherwise would be counted as CTCs.

Gene expression profiling of circulating tumor cells captured by MicroCavity Array is superior to enumeration in demonstrating therapy response in patients with newly diagnosed advanced and locally advanced non-small cell lung cancer

Background

Circulating tumor cells (CTCs) are a promising non-invasive tool for monitoring therapy response. The only Food and Drug Administration (FDA)-approved test is limited to enumeration of epithelial CTC without further characterization and is not approved for the management of non-small cell lung cancer (NSCLC). Here we use a MicroCavity Array (MCA) system to capture CTC agnostic of epithelial markers for further molecular testing in NSCLC.

Methods

CTCs were enumerated by fluorescent microscopy as longitudinal sampling throughout disease management from 213 NSCLC patients. CTC-enriched samples from a subset of 127 patients were interrogated for gene expression by reverse transcription polymerase chain reaction (RT-PCR) using a customized pre-selected panel of 20 genes.

Results

At least 1 CTC was detected by enumeration in 53.8% of samples. Most patients had fewer than 5 CTCs (91%) and the highest observed count was 35 CTCs. Enumeration of single CTCs was not prognostic, although detection of CTC clusters at any time point was associated with increased risk of progression [hazard ratio (HR) 3.00, 95% confidence interval (CI): 1.1-8.2, P=0.0318]. In contrast, 124 (97.6%) patients with samples interrogated for gene expression had at least 1 gene detectable in at least 1 sample, and 101 (79.5%) had at least one elevated epithelial gene in at least one timepoint. High expression of BCL2, CD274 [programmed death-ligand 1 (PD-L1)], CDH1, EPCAM, FGFR1, FN1, KRT18, MET and MUC1 were associated with poor prognosis. Patients with CTCs positive for at least 3 epithelial genes at baseline all progressed within 10 months (HR 8.2, P<0.001, 95% CI: 3.2-21.1). BCL2, CD274 (PD-L1), EPCAM and MUC1 remained significant independent prognostic factors in multivariate, time-dependent analyses of progression and death.

Conclusions

The selective profile of CTC genes and identification of CTC clusters better correlated with prognosis than enumeration of enriched CTC in NSCLC patients in this study.

Crucial roles of circulating tumor cells in the metastatic cascade and tumor immune escape: biology and clinical translation

Cancer-related deaths are mainly caused by metastatic spread of tumor cells from the primary lesion to distant sites via the blood circulation. Understanding the mechanisms of blood-borne tumor cell dissemination by the detection and molecular characterization of circulating tumor cells (CTCs) in the blood of patients with cancer has opened a new avenue in cancer research. Recent technical advances have enabled a comprehensive analysis of the CTCs at the genome, transcriptome and protein level as well as first functional studies using patient-derived CTC cell lines. In this review, we describe and discuss how research on CTCs has yielded important insights into the biology of cancer metastasis and the response of patients with cancer to therapies directed against metastatic cells. Future investigations will show whether CTCs leaving their primary site are more vulnerable to attacks by immune effector cells and whether cancer cell dissemination might be the 'Achilles heel' of metastatic progression. Here, we focus on the lessons learned from CTC research on the biology of cancer metastasis in patients with particular emphasis on the interactions of CTCs with the immune system. Moreover, we describe and discuss briefly the potential and challenges for implementing CTCs into clinical decision-making including detection of minimal residual disease, monitoring efficacies of systemic therapies and identification of therapeutic targets and resistance mechanisms.

Circulating Tumor Cells as a Predictive Biomarker in Resectable Lung Cancer: A Systematic Review and Meta-Analysis

Background: In breast, prostate, and other epithelial tumors, circulating tumor cells (CTC) in peripheral blood may predict survival. Our study evaluated the prognostic significance of baseline and postoperative CTC in patients with early non-small cell lung cancer (NSCLC) through a meta-analytic approach. Methods: Prospective studies comparing survival outcomes between positive (CTC+) and negative CTC (CTC−) patients were systematically searched. Primary outcomes were overall (OS) and disease-free survival (DFS) with hazard ratio (HR) and 95% confidence interval (CI) as the effect measure. Pooled HR determined the prognostic role under a fixed-effect or random-effect model depending on heterogeneity. Results: Eighteen studies with 1321 patients were eligible. CTC+ patients were associated with an increased risk of death (HR 3.53, 95% CI 2.51−4.95; p < 0.00001) and relapse (HR 2.97, 95% CI 2.08−4.22; p < 0.00001). Subgroup analysis results were consistent in different subsets, including time points (baseline and postoperative) and sources (peripheral and pulmonary vein) of blood collection, detection methods (label-free, label-dependent, and RT-PCR), and follow-up duration. Conclusion: Our meta-analysis revealed that CTC is a promising predictive biomarker for stratifying survival outcomes in patients with early-stage NSCLC. However, future studies are required to validate these findings and standardize detection methods.

Phenotyping of rare circulating cells in the blood of non-metastatic breast cancer patients using microfluidic Labyrinth technology

Label-free technologies for isolating rare circulating cells in breast cancer patients are widely available; however, they are mostly validated on metastatic patient blood samples. Given the need to use blood-based biomarkers to inform on disease progression and treatment decisions, it is important to validate these technologies in non-metastatic patient blood samples. In this study, we specifically focus on a recently established label-free microfluidic technology Labyrinth and assess its capabilities to phenotype a variety of rare circulating tumor cells indicative of epithelial-to-mesenchymal transition as well as cancer-associated macrophage-like (CAML) cells. We specifically chose a patient cohort that is non-metastatic and selected to undergo neoadjuvant chemotherapy to assess the performance of the Labyrinth technology. We enrolled 21 treatment naïve non-metastatic breast cancer patients of various disease stages. Our results indicate that (i) Labyrinth microfluidic technology is successfully able to isolate different phenotypes of CTCs despite the counts being low. (ii) Invasive phenotypes of CTCs such as transitioning CTCs and mesenchymal CTCs were found to be present in high numbers in stage III patients as compared to stage II patients. (iii) As the total load of CTCs increased, the mesenchymal CTCs were found to be increasing. (iv) Labyrinth was able to isolate CAMLs with the counts being higher in stage III patients as compared to stage II patients. Our study demonstrates the ability of the Labyrinth microfluidic technology to isolate rare cancer-associated cells from the blood of treatment naïve non-metastatic breast cancer patients, laying the foundation for tracking oncogenic spread and immune response in patients undergoing neoadjuvant chemotherapy.

Development and validation of an epithelial–mesenchymal transition-related gene signature for predicting prognosis

BACKGROUND

Currently, there are many therapeutic methods for lung adenocarcinoma (LUAD), but the 5-year survival rate is still only 15% at later stages. Epithelial– mesenchymal transition (EMT) has been shown to be closely associated with local dissemination and subsequent metastasis of solid tumors. However, the role of EMT in the occurrence and development of LUAD remains unclear.

AIM

To further elucidate the value of EMT-related genes in LUAD prognosis.

METHODS

Univariate, least absolute shrinkage and selection operator, and multivariate Cox regression analyses were applied to establish and validate a new EMT-related gene signature for predicting LUAD prognosis. The risk model was evaluated by Kaplan–Meier survival analysis, principal component analysis, and functional enrichment analysis and was used for nomogram construction. The potential structures of drugs to which LUAD is sensitive were discussed with respect to EMT-related genes in this model.

RESULTS

Thirty-three differentially expressed genes related to EMT were found to be highly associated with overall survival (OS) by using univariate Cox regression analysis (log2FC ≥ 1, false discovery rate < 0.001). A prognostic signature of 7 EMT-associated genes was developed to divide patients into two risk groups by high or low risk scores. Kaplan–Meier survival analysis showed that the OS of patients in the high-risk group was significantly poorer than that of patients in the low-risk group (P < 0.05). Multivariate Cox regression analysis showed that the risk score was an independent risk factor for OS (HR > 1, P < 0.05). The results of receiver operator characteristic curve analysis suggested that the 7-gene signature had a perfect ability to predict prognosis (all area under the curves > 0.5).

CONCLUSION

The EMT-associated gene signature classifier could be used as a feasible indicator for predicting OS.

The molecular mechanisms and therapeutic strategies of EMT in tumor progression and metastasis

Epithelial–mesenchymal transition (EMT) is an essential process in normal embryonic development and tissue regeneration. However, aberrant reactivation of EMT is associated with malignant properties of tumor cells during cancer progression and metastasis, including promoted migration and invasiveness, increased tumor stemness, and enhanced resistance to chemotherapy and immunotherapy. EMT is tightly regulated by a complex network which is orchestrated with several intrinsic and extrinsic factors, including multiple transcription factors, post-translational control, epigenetic modifications, and noncoding RNA-mediated regulation. In this review, we described the molecular mechanisms, signaling pathways, and the stages of tumorigenesis involved in the EMT process and discussed the dynamic non-binary process of EMT and its role in tumor metastasis. Finally, we summarized the challenges of chemotherapy and immunotherapy in EMT and proposed strategies for tumor therapy targeting EMT.

PD-L1/pS6 in Circulating Tumor Cells (CTCs) during Osimertinib Treatment in Patients with Non-Small Cell Lung Cancer (NSCLC)

The PD-1/PD-L1 axis provides CTCs an escape route from the immune system. Phosphorylation of the ribosomal protein S6 is implicated in the same pathway, following mTOR activation. The aim of the study was to investigate the expression of PD-L1 and pS6 in CTCs from NSCLC patients under Osimertinib treatment at a single cell level. CTCs were isolated using ISET from NSCLC patients’ blood [37 at baseline, 25 after the 1st cycle, and 23 at the end of treatment (EOT)]. Staining was performed using immunofluorescence. Cytokeratin-positive (CK+) CTCs were detected in 62% of patients. CK+PD-L1+CD45− and CK+pS6+ phenotypes were detected in 38% and 41% of the patients at baseline, in 28% and 32% after 1st cycle, and in 30% and 35% at EOT, respectively. Spearman’s analysis revealed statistically significant correlations between PD-L1 and pS6 phenotypes at all time points. Survival analysis revealed that CK+pS6+ (p = 0.003) and CKlowpS6+ (p = 0.021) phenotypes after 1st cycle were related to significantly decreased one-year progression-free survival (PFS12m) and PFS, respectively. CK+PD-L1+CD45−phenotype at baseline and after 1st cycle showed a trend for decreased PFS12m. Increased expression of PD-L1/pS6 in CTCs of Osimertinib-treated NSCLC patients implies the activation of the corresponding pathway, which is potentially associated with poor clinical outcomes.

Powering single-cell genomics to unravel circulating tumour cell subpopulations in non-small cell lung cancer patients

BACKGROUND

Circulating tumour cells (CTCs) are attractive "liquid biopsy" candidates that could provide insights into the different phenotypes of tumours present within a patient. The epithelial-to-mesenchymal transition (EMT) of CTCs is considered a critical step in tumour metastasis; however, it may confound traditional epithelial feature-based CTC isolation and detection. We applied single-cell copy number alteration (CNA) analysis for the identification of genomic alterations to confirm the neoplastic nature of circulating cells with only mesenchymal phenotypes.

METHODS

We isolated CTCs from blood samples collected from 46 NSCLC patients using the Parsortix system. Enriched cells were subjected to immunofluorescent staining for CTC identification using a multi-marker panel comprising both epithelial and mesenchymal markers. A subset of isolated CTCs was subjected to whole genome amplification (WGA) and low-pass whole-genome sequencing (LP-WGS) for the analysis of copy number alterations (CNAs).

RESULTS

CTCs were detected in 16/46 (34.8%) patients, inclusive of CK⁺/EpCAM⁺ CTCs (3/46, 6.5%) and Vim⁺ CTCs (13/46, 28.3%). Clusters of Vim⁺ cells were detected in 8 samples, which constitutes 50% of the total number of NSCLC patients with CTCs. No patients had detectable hybrid CK⁺/EpCAM⁺/Vim⁺ cells. All of the tested CK⁺/EpCAM⁺ CTCs and 7/8 Vim⁺ CTCs or CTC clusters carried CNAs confirming their neoplastic nature. Notably, the Vim⁺ cluster with no CNAs was characterised by spindle morphology and, therefore, defined as normal mesenchymal circulating cells.

CONCLUSION

Our results revealed that CK-negative, vimentin-expressing cells represent a large proportion of CTCs detected in NSCLC patients, which are likely missed by standard epithelial-marker-dependent CTC categorisation.

Prognostic value of integrating circulating tumour cells and cell-free DNA in non-small cell lung cancer

Background

Non-small cell lung cancer (NSCLC) often presents at an incurable stage, and majority of patients will be considered for palliative treatment at some point in their disease. Despite recent advances, the prognosis remains poor, with a median overall survival of 12–18 months. Liquid biopsy-based biomarkers have emerged as potential candidates for predicting prognosis and response to therapy in NSCLC patients. This pilot study evaluated whether combining circulating tumour cells and clusters (CTCs) and cell-free DNA (cfDNA) can predict progression-free survival (PFS) in NSCLC patients.

Methods

CTC and cfDNA/ctDNA from advanced stage NSCLC patients were measured at study entry (T⁰) and 3-months post-treatment (T¹). CTCs were enriched using a spiral microfluidic chip and characterised by immunofluorescence. ctDNA was assessed using an UltraSEEK® Lung Panel. Kaplan-Meier plots were generated to investigate the contribution of the presence of CTC/CTC clusters and cfDNA for PFS. Cox proportional hazards analysis compared time to progression versus CTC/CTC cluster counts and cfDNA levels.

Results

Single CTCs were found in 14 out of 25 patients, while CTC clusters were found in 8 out of the 25 patients at T⁰. At T¹, CTCs were found in 7 out of 18 patients, and CTC clusters in 1 out of the 18 patients. At T⁰, CTC presence and the combination of CTC cluster counts with cfDNA levels were associated with shorter PFS, p = 0.0261, p = 0.0022, respectively.

Conclusions

Combining CTC cluster counts and cfDNA levels could improve PFS assessment in NSCLC patients. Our results encourage further investigation on the combined effect of CTC/cfDNA as a prognostic biomarker in a large cohort of advanced stage NSCLC patients.

Clinical Applications of Circulating Tumour Cells and Circulating Tumour DNA in Non-Small Cell Lung Cancer-An Update

Despite efforts to improve earlier diagnosis of non-small cell lung cancer (NSCLC), most patients present with advanced stage disease, which is often associated with poor survival outcomes with only 15% surviving for 5 years from their diagnosis. Tumour tissue biopsy is the current mainstream for cancer diagnosis and prognosis in many parts of the world. However, due to tumour heterogeneity and accessibility issues, liquid biopsy is emerging as a game changer for both cancer diagnosis and prognosis. Liquid biopsy is the analysis of tumour-derived biomarkers in body fluids, which has remarkable advantages over the use of traditional tumour biopsy. Circulating tumour cells (CTCs) and circulating tumour DNA (ctDNA) are two main derivatives of liquid biopsy. CTC enumeration and molecular analysis enable monitoring of cancer progression, recurrence, and treatment response earlier than traditional biopsy through a minimally invasive liquid biopsy approach. CTC-derived ex-vivo cultures are essential to understanding CTC biology and their role in metastasis, provide a means for personalized drug testing, and guide treatment selection. Just like CTCs, ctDNA provides opportunity for screening, monitoring, treatment evaluation, and disease surveillance. We present an updated review highlighting the prognostic and therapeutic significance of CTCs and ctDNA in NSCLC.

Circulating Tumor-Macrophage Fusion Cells and Circulating Tumor Cells Complement Non-Small-Cell Lung Cancer Screening in Patients With Suspicious Lung-RADS 4 Nodules

PURPOSE

Low-dose computed tomography (LDCT) screening of high-risk patients decreases lung cancer-related mortality. However, high false-positive rates associated with LDCT result in unnecessary interventions. To distinguish non-small-cell lung cancer (NSCLC) from benign nodules, in the present study, we integrated cellular liquid biomarkers in patients with suspicious lung nodules (lung cancer screening reporting and data system [Lung-RADS] 4).

METHODS

Prospectively, 7.5 mL of blood was collected from 221 individuals (training set: 90 nonscreened NSCLC patients, 74 high-risk screening patients with no/benign nodules [Lung-RADS 1-3], and 20 never smokers; validation set: 37 patients with suspicious nodules [Lung-RADS 4]). Circulating tumor cells (CTCs), CTC clusters, and tumor-macrophage fusion (TMF) cells were identified by blinded analyses. Screening patients underwent a median of two LDCTs (range, 1-4) with a median surveillance time of 30 (range, 11-50) months.

RESULTS

In the validation set of 37 Lung-RADS 4 patients, all circulating cellular biomarker counts (P < .005; Wilcoxon test) and positivity rates were significantly higher in 23 biopsy-proven NSCLC patients (CTCs: 23 of 23 [100%], CTC clusters: 6 of 23 [26.1%], and TMF cells: 15 of 23 [65.2%]) than in 14 patients with biopsy-proven benign nodules (6 of 14 [42.9%], 0 of 14 [0%], and 2 of 14 [14.3%]). On the basis of cutoff values from the training set, logistic regression with receiver operating characteristic and area under the curve analyses demonstrated that CTCs (sensitivity: 0.870, specificity: 1.0, and area under the curve: 0.989) and TMF cells (0.652; 0.880; 0.790) complement LDCT in diagnosing NSCLC in Lung-RADS 4 patients.

CONCLUSION

Cellular liquid biomarkers have a potential to complement LDCT interpretation of suspicious Lung-RADS 4 nodules to distinguish NSCLC from benign lung nodules. A future prospective, large-scale, multicenter clinical trial should validate the role of cellular liquid biomarkers in improving diagnostic accuracy in high-risk patients with Lung-RADS 4 nodules.

Detyrosinated α-Tubulin, Vimentin and PD-L1 in Circulating Tumor Cells (CTCs) Isolated from Non-Small Cell Lung Cancer (NSCLC) Patients

Upregulation of Vimentin (VIM), alpha-Tubulin (TUB) and Detyrosinated tubulin (GLU) in circulating tumor cells (CTCs) derived from breast cancer patients is related to poor prognosis. In the current study we evaluated for the first time, these cytoskeletal proteins in sixty Non-Small Cell Lung Cancer (NSCLC) patients’ CTCs (33 treatment-naïve and 27 pre-treated). Samples were isolated using the ISET platform and stained with a pancytokeratin (CK)/CD45/TUB, CK/GLU/VIM and CK/programmed death ligand 1 (PD-L1) combination of antibodies. Subsequently, slides were analyzed using confocal laser scanning microscopy. CTCs were detected in 86.7% of the patients. CTCs with TUB expression were identified in 65.4% (34/52) of the CK (+)-patients. GLU, VIM and PD-L1 were also evaluated. The frequency of the observed phenotypes was as follow: (CK+/GLU−/VIM−): 35.2%, (CK+/GLU+/VIM+): 63.0%, (CK+/GLU+/VIM−): 16.7%, (CK+/GLU−/VIM+): 72.2%, (CK+/PD-L1−): 75% and (CK+/PD-L1+): 55%. The OS was significantly decreased in patients with high GLU (3.8 vs. 7.9 months; p = 0.018) and/or high VIM (3.2 vs. 7.1 months; p = 0.029) expression in their CTCs. PD-L1 was also related to OS (3.4 vs. 7.21 months; p = 0.035). Moreover, TUB-high and TUB-low expression in CTCs inversely influenced patients’ OS as independent prognostic factors (p = 0.041 and p = 0.009). The current study revealed that TUB, GLU, VIM and PD-L1 were overexpressed in CTCs from NSCLC patients. Furthermore, the presence of GLU, VIM-positive and PD-L1 in CTCs is potentially related to patients’ outcomes.

Relevance of Circulating Tumor Cells as Predictive Markers for Cancer Incidence and Relapse

Shedding of cancer cells from the primary site or undetectable bone marrow region into the circulatory system, resulting in clinically overt metastasis or dissemination, is the hallmark of unfavorable invasive cancers. The shed cells remain in circulation until they extravasate to form a secondary metastatic lesion or undergo anoikis. The circulating tumor cells (CTCs) found as single cells or clusters carry a plethora of information, are acknowledged as potential biomarkers for predicting cancer prognosis and cancer progression, and are supposed to play key roles in determining tailored therapies for advanced diseases. With the advent of novel technologies that allow the precise isolation of CTCs, more and more clinical trials are focusing on the prognostic and predictive potential of CTCs. In this review, we summarize the role of CTCs as a predictive marker for cancer incidence, relapse, and response to therapy.

The Expression of Programmed Death Ligand 1 and Vimentin in Resected Non-Metastatic Non-Small-Cell Lung Cancer: Interplay and Prognostic Effects

Programmed death ligand 1 (PD-L1) is an immune checkpoint with a role in cancer-related immune evasion. It is a target for cancer immunotherapy and its expression is detected for the use of some immune checkpoint inhibitors in advanced non-small cell lung cancer patients (NSCLC). Vimentin is a key component of the epithelial-to-mesenchymal transition phenotype. Its expression has negative prognostic effects in NSCLC. In this study, we retrospectively evaluated PD-L1 and vimentin expression in tumor cells, immune infiltrate and PD-L1 positive immune infiltrate via immunohistochemistry in tissue samples from resected non-metastatic NSCLC patients. We explored the interplay between PD-L1 and vimentin expression through Spearman’s correlation test. We performed univariate analysis through the Cox models for demographic and clinico-pathological variables, and also for dichotomized biomarkers, i.e., PD-L1 and vimentin in tumor cells, both with 1 and 50% cutoffs. We used Kaplan-Meier method to estimate the overall survival, comparing both vimentin and PD-L1 positive patients with all the others. We found a weak positive correlation between PD-L1 and vimentin expressions in tumor cells (r = 0.25; p = 0.001). We also observed a statistically not significant trend towards a shorter overall survival in patients with both PD-L1 and vimentin expression >1% (HR = 1.36; 95% CI: 0.96–1.93, p = 0.087). In conclusion, these findings suggest that interplay between PD-L1 and vimentin may exist in non-metastatic NSCLC patients and the positivity of both markers in tumor tissue is associated with a trend towards a worse prognosis.

Multi-Marker Immunofluorescent Staining and PD-L1 Detection on Circulating Tumour Cells from Ovarian Cancer Patients

Simple Summary

Circulating tumour cells (CTCs) have the potential to serve as a rich source of information for cancer diagnostic and therapeutic decisions. To fully exploit this minimally invasive diagnostic resource requires techniques that aid in enriching heterogenous populations of CTCs and markers to efficiently characterise these cells as tumour derived. In the present study we eva-luated the microfluidic enrichment of CTCs and a multi-marker staining methodology for the identification of heterogeneous CTCs in ovarian cancer (OC) patients and evaluation of PD-L1 expression. We showed, for the first time, the existence of hybrid CTCs with an epithelial/mesenchymal phenotype and their association with PD-L1 in OC. Incorporation of this method in future clinical trials can help predict immunotherapy responsiveness in OC patients.

Abstract

Detection of ovarian cancer (OC) circulating tumour cells (CTCs) is primarily based on targeting epithelial markers, thus failing to detect mesenchymal tumour cells. More importantly, the immune checkpoint inhibitor marker PD-L1 has not been demonstrated on CTCs from OC patients. An antibody staining protocol was developed and tested using SKOV-3 and OVCA432 OC cell lines. We targeted epithelial (cytokeratin (CK) and EpCAM), mesenchymal (vimentin), and OC-specific (PAX8) markers for detection of CTCs, and CD45/16 and CD31 were used for the exclusion of white blood and vascular endothelial cells, respectively. PD-L1 was used for CTC characterisation. CTCs were enriched using the Parsortix™ system from 16 OC patients. Results revealed the presence of CTCs in 10 (63%) cases. CTCs were heterogeneous, with 113/157 (72%) cells positive for CK/EpCAM (epithelial marker), 58/157 (37%) positive for vimentin (mesenchymal marker), and 17/157 (11%) for both (hybrid). PAX8 was only found in 11/157 (7%) CTCs. In addition, 62/157 (39%) CTCs were positive for PD-L1. Positivity for PD-L1 was significantly associated with the hybrid phenotype when compared with the epithelial (p = 0.007) and mesenchymal (p = 0.0009) expressing CTCs. Characterisation of CTC phenotypes in relation to clinical outcomes is needed to provide insight into the role that epithelial to mesenchymal plasticity plays in OC and its relationship with PD-L1.

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.

Circulating Tumour Cells (CTCs) in NSCLC: From Prognosis to Therapy Design

Designing optimal (neo)adjuvant therapy is a crucial aspect of the treatment of non-small-cell lung carcinoma (NSCLC). Standard methods of chemotherapy, radiotherapy, and immunotherapy represent effective strategies for treatment. However, in some cases with high metastatic activity and high levels of circulating tumour cells (CTCs), the efficacy of standard treatment methods is insufficient and results in treatment failure and reduced patient survival. CTCs are seen not only as an isolated phenomenon but also a key inherent part of the formation of metastasis and a key factor in cancer death. This review discusses the impact of NSCLC therapy strategies based on a meta-analysis of clinical studies. In addition, possible therapeutic strategies for repression when standard methods fail, such as the administration of low-toxicity natural anticancer agents targeting these phenomena (curcumin and flavonoids), are also discussed. These strategies are presented in the context of key mechanisms of tumour biology with a strong influence on CTC spread and metastasis (mechanisms related to tumour-associated and -infiltrating cells, epithelial–mesenchymal transition, and migration of cancer cells).

Progress and application of circulating tumor cells in non-small cell lung cancer

Non-small cell lung cancer (NSCLC) has the highest morbidity and mortality worldwide among malignant tumors. NSCLC is a great threat to health and well-being. Biopsy is the gold standard to diagnose lung cancer, but traditional biopsy methods cannot fully reflect the true condition of tumors. There is growing evidence that a single-point biopsy fails to reveal the complete landscape of the tumor due to intratumor heterogeneity, but it is impractical to complete multiple biopsies that are separated both spatially and temporally. Liquid biopsy heralds that a new era is coming. Circulating tumor cells (CTCs) are tumor cells that circulate in the peripheral blood after being shed from primary or metastatic tumors. CTCs constitute a considerable portion of a liquid biopsy, which contributes to the diagnosis, assessment of prognosis, and therapy of NSCLC. Herein, this review discusses the technologies for detection and enrichment of CTCs as well as clinical applications involving CTCs.

Prognostic significance of programmed cell death-ligand 1 expression on circulating tumor cells in various cancers: A systematic review and meta-analysis

Background

The prognostic significance of programmed cell death‐ligand 1 (PD‐L1) expression on circulating tumor cells (CTCs) has been explored but is still in controversy. We performed, for the first time, a meta‐analysis to systematically evaluate its prognostic value in human cancers.

Methods

Literature databases were searched for eligible studies prior to June 30, 2021. The pooled hazard ratios (HRs) and 95% confidence intervals (95% CIs) were calculated for the associations of pre‐treatment and post‐treatment PD‐L1⁺ CTCs with progression‐free survival (PFS) and overall survival (OS). Subgroup analyses with regards to cancer type, treatment, CTC enrichment method, PD‐L1 detection method, cut‐off, and specifically the comparison model were performed.

Results

We included 30 eligible studies (32 cohorts, 1419 cancer patients) in our analysis. Pre‐treatment PD‐L1⁺ CTCs detected by immunofluorescence (IF) tended to predict better PFS (HR = 0.55, 95% CI 0.28–1.08, p = 0.084) and OS (HR = 0.61, 95% CI 0.36–1.04, p = 0.067) for immune checkpoint inhibitor (ICI) treatment, but were significantly associated with unfavorable survival for non‐ICI therapies (PFS: HR = 1.85, 95% CI 1.21–2.85, p = 0.005; OS: HR = 2.44, 95% CI 1.69–3.51, p < 0.001). Post‐treatment PD‐L1⁺ CTCs predicted markedly worse PFS and OS. The prognostic value was obviously modulated by comparison models. Among patients with detectable CTCs, PD‐L1⁺ individuals had comparable survival to PD‐L1⁻ individuals, except ICI treatment for which PD‐L1⁺ may predict better PFS (HR = 0.42, 95% CI 0.17–1.06, p = 0.067). Patients with PD‐L1⁺ CTCs had worse survival prognosis compared to those without PD‐L1⁺ CTCs in overall analysis (PFS: HR = 2.10, 95% CI 1.59–2.77, p < 0.001; OS: HR = 2.55, 95% CI 1.70–3.81, p < 0.001) and in most subgroups.

Conclusions

Our analysis demonstrated that PD‐L1 positive expression on CTCs predicted better survival prognosis for ICI treatment but worse survival for other therapies, which thus can be potentially used as a prognostic marker of malignant tumor treatment. However, the prognostic value of PD‐L1⁺ CTCs for ICI treatment needs validation by more large‐scale studies in the future.

Programmed Cell Death Ligand 1-Expressing Circulating Tumor Cells: A New Prognostic Biomarker in Non-Small Cell Lung Cancer

BACKGROUND

In non-small cell lung cancer (NSCLC), analysis of programmed cell death ligand 1 (PD-L1) expression in circulating tumor cells (CTCs) is a potential alternative to overcome the problems linked to the tumor biopsy spatiotemporal heterogeneity. However, the prognostic significance of PD-L1-positive [PD-L1(+)] CTCs remains controversial.

METHODS

We prospectively evaluated the correlation with clinicopathological variables and prognostic value of PD-L1(+) CTCs, detected with the FDA-cleared CellSearch® system, in 54 patients with advanced NSCLC.

RESULTS

We detected CTCs and PD-L1(+) CTCs in 43.4% and 9.4% of patients with NSCLC. PD-L1 expression concordance between tumor tissue and CTCs was low (54%). The presence of PD-L1(+) CTC correlated with the absence of gene alterations in tumor tissue and with poor prognosis-related biological variables (anemia, hyponatremia, increased lactate dehydrogenase). In univariate analysis, absence of gene alterations, number of metastatic sites, prior systemic therapies, and presence of CTCs and PD-L1(+) CTCs were associated with worse overall survival, whereas PD-L1 expression in tumor tissue was not. In multivariate analysis, squamous cell carcinoma histology, number of prior systemic treatments, and the presence of CTC were significantly associated with overall survival. Survival was worse in patients with PD-L1(+) CTCs than in patients with PD-L1-negative CTC or without any CTC.

CONCLUSIONS

Our study suggests that the presence of PD-L1(+) CTCs is associated with poor prognosis in patients with advanced NSCLC. Studies with larger samples are needed to confirm our results and to determine how PD-L1(+) CTC detection could help to predict the response or resistance to anti-PD-1/PD-L1 therapies.Clinical trial registration NCT02866149.

Hypoxia in Lung Cancer Management: A Translational Approach

Simple Summary

Hypoxia is a common feature of lung cancers. Nonetheless, no guidelines have been established to integrate hypoxia-associated biomarkers in patient management. Here, we discuss the current knowledge and provide translational novel considerations regarding its clinical detection and targeting to improve the outcome of patients with non-small-cell lung carcinoma of all stages.

Abstract

Lung cancer represents the first cause of death by cancer worldwide and remains a challenging public health issue. Hypoxia, as a relevant biomarker, has raised high expectations for clinical practice. Here, we review clinical and pathological features related to hypoxic lung tumours. Secondly, we expound on the main current techniques to evaluate hypoxic status in NSCLC focusing on positive emission tomography. We present existing alternative experimental approaches such as the examination of circulating markers and highlight the interest in non-invasive markers. Finally, we evaluate the relevance of investigating hypoxia in lung cancer management as a companion biomarker at various lung cancer stages. Hypoxia could support the identification of patients with higher risks of NSCLC. Moreover, the presence of hypoxia in treated tumours could help clinicians predict a worse prognosis for patients with resected NSCLC and may help identify patients who would benefit potentially from adjuvant therapies. Globally, the large quantity of translational data incites experimental and clinical studies to implement the characterisation of hypoxia in clinical NSCLC management.

Correlation between PD-L1 expression ON CTCs and prognosis of patients with cancer: a systematic review and meta-analysis

Circulating tumor cells (CTCs) are considered to be related to the prognosis of cancer patients. CTC is a powerful indicator for recurrence or metastasis. The relationship, however, between the expression of programmed cell death receptor ligand 1 (PD-L1) on CTCs in peripheral blood and the prognosis, is still controversial. Here, we conducted a meta-analysis to evaluate its prognostic value. A total of 20 articles were screened from PubMed, Embase, Cochrane, China National Knowledge Internet (CNKI) and WanFang Database, and the Hazard Ratio (HR) along with 95% confidence intervals (CIs) of each article were combined to study the relationship between PD-L1 expression on CTCs and prognosis. The expression of PD-L1 on CTCs in the peripheral blood of cancer patients is associated with poor prognosis. The pooled HRs for overall survival (OS) in cancer patients were 1.85 (95% CI, 1.29-2.66, P = .001). The pooled HRs for progression-free survival (PFS) in cancer patients were 1.50 (95% CI, 1.12-2.01; P = .007). This is the first meta-analysis to clarify the expression of PD-L1 on CTCs at baseline affects the prognosis of cancer patients. Patients with CTCs expressing PD-L1 had a shorter survival time than patients with CTCs not expressing PD-L1.

The multiple roles and therapeutic potential of clusterin in non-small-cell lung cancer: a narrative review

Worldwide, lung cancer is the most common form of cancer, with an estimated 2.09 million new cases and 1.76 million of death cause in 2018. It is categorized into two subtypes, small-cell lung cancer (SCLC) and non-small-cell lung cancer (NSCLC). Although platinum-based chemotherapy or molecular targeted drugs is recommended for advanced stages of NSCLC patients, however, resistance to drug and chemotherapy are hindrances for patients to fully beneficial from these treatments. Clusterin (CLU), also known as apolipoprotein J, is a versatile chaperone molecule which produced by a wide array of tissues and found in most biologic fluids. There are studies reported high expression of CLU confers resistance to chemotherapy and radiotherapy in different lung cancer cell lines. By silencing CLU using Custirsen (OGX-011), a second-generation antisense oligonucleotide (ASO) that inhibits CLU production, not only could sensitized cells to chemo- and radiotherapy, also could decreased their metastatic potential. We will review here the extensive literature linking CLU to NSCLC, update the current state of research on CLU for better understanding of this unique protein and the development of more effective anti- CLU treatment.

Clinical Relevance of Mesenchymal- and Stem-Associated Phenotypes in Circulating Tumor Cells Isolated from Lung Cancer Patients

Simple Summary

Lung cancer is the most frequent malignancy in the world. Most lung cancer patients are diagnosed at an advanced stage. To make matters worse, the survival of patients is very poor. Circulating tumor cells (CTCs), albeit rare, have been portrayed as essential players in the progression of lung cancer. It is definitely not easy being a CTC. First, they escape from the primary tumor, then they travel in the bloodstream, have to survive really harsh conditions, and finally, they form metastases. The adoption of epithelial-to-mesenchymal transition as well as cancer stem cell features has been suggested to allow CTCs to survive and metastasize. This review will focus on how these features can be used to estimate the prognosis of lung cancer patients.

Abstract

Lung cancer is the leading cause of cancer-related mortality globally. Among the types of lung cancer, non-small-cell lung cancer (NSCLC) is more common, while small-cell lung cancer (SCLC) is less frequent yet more aggressive. Circulating tumor cells (CTCs), albeit rare, have been portrayed as essential players in the progression of lung cancer. CTCs are considered to adopt an epithelial-to-mesenchymal transition (EMT) phenotype and characteristics of cancer stem cells (CSCs). This EMT (or partial) phenotype affords these cells the ability to escape from the primary tumor, travel into the bloodstream, and survive extremely adverse conditions, before colonizing distant foci. Acquisition of CSC features, such as self-renewal, differentiation, and migratory potential, further reflect CTCs’ invasive potential. CSCs have been identified in lung cancer, and expression of EMT markers has previously been correlated with poor clinical outcomes. Thus far, a vast majority of studies have concentrated on CTC detection and enumeration as a prognostic tools of patients’ survival or for monitoring treatment efficacy. In this review, we highlight EMT and CSC markers in CTCs and focus on the clinical significance of these phenotypes in the progression of both non-small- and small-cell lung cancer.

Tumor Immune Microenvironment during Epithelial-Mesenchymal Transition

Epithelial-mesenchymal transition (EMT) has been shown to play a critical role in tumor development from initiation to metastasis. EMT could be regarded as a continuum, with intermediate hybrid epithelial and mesenchymal phenotypes having high plasticity. Classical EMT is characterized by the phenotype change of epithelial cells to cells with mesenchymal properties, but EMT is also associated with multiple other molecular processes, including tumor immune evasion. Some previous studies have shown that EMT is associated with the cell number of immunosuppressive cells, such as myeloid-derived suppressor cells, and the expression of immune checkpoints, such as programmed cell death-ligand 1, in several cancer types. At the molecular level, EMT transcriptional factors, including Snail, Zeb1, and Twist1, produce or attract immunosuppressive cells or promote the expression of immunosuppressive checkpoint molecules via chemokine production, leading to a tumor immunosuppressive microenvironment. In turn, immunosuppressive factors induce EMT in tumor cells. This feedback loop between EMT and immunosuppression promotes tumor progression. For therapy directly targeting EMT has been challenging, the elucidation of the interactive regulation of EMT and immunosuppression is desirable for developing new therapeutic approaches in cancer. The combination of immune checkpoint inhibitors and immunotherapy targeting immunosuppressive cells could be a promising therapy for EMT.

Minimal Residual Disease, Metastasis and Immunity

Progression from localized to metastatic disease requires cancer cells spreading to distant organs through the bloodstream. Only a small proportion of these circulating tumor cells (CTCs) survives dissemination due to anoikis, shear forces and elimination by the immune system. However, all metastases originate from CTCs capable of surviving and extravasating into distant tissue to re-initiate a tumor. Metastasis initiation is not always immediate as disseminated tumor cells (DTCs) may enter a non-dividing state of cell dormancy. Cancer dormancy is a reversible condition that can be maintained for many years without being clinically detectable. Subsequently, late disease relapses are thought to be due to cancer cells ultimately escaping from dormant state. Cancer dormancy is usually associated with minimal residual disease (MRD), where DTCs persist after intended curative therapy. Thus, MRD is commonly regarded as an indicator of poor prognosis in all cancers. In this review, we examine the current understanding of MRD and immunity during cancer progression to metastasis and discuss clinical perspectives for oncology.

Immune checkpoint molecules are regulated by transforming growth factor (TGF)-β1-induced epithelial-to-mesenchymal transition in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the most common type of primary liver cancer with a high mortality rate. Epithelial-to-mesenchymal transition (EMT) confers cancer cells with immune evasive ability by modulating the expression of immune checkpoints in many cancers. Thus, the aim of our study is to examine the interplay between EMT and immune checkpoint molecules in HCC. A reversible EMT model was utilised with transforming growth factor (TGF)-β1 as an EMT inducer for HCC cell lines Hep3B and PLC/PRF/5. HCC cells were treated with TGF-β1 for 72 h and the EMT status and immune checkpoint expression were examined. In addition, the migratory ability of HCC cells were examined using wound healing and transwell migration assays in the reversible EMT model. siRNA-mediated knockdown of immune checkpoint molecule, B7-H3, was further utilised to validate the association between TGF-β1-mediated EMT and immune checkpoint expression in HCC. In addition, a web-based platform, SurvExpress, was utilised to evaluate the association between expression of TGF-β1 in combination with immune checkpoint molecules and overall survival in HCC patients. We observed induction of EMT upon treatment of HCC cells with TGF-β1 revealed by reduced expression of epithelial markers along with increased expression of mesenchymal markers. Withdrawal of TGF-β1 reversed the process of EMT with elevated expression of epithelial markers and reduced expression of mesenchymal markers. TGF-β1 treatment elevated the migratory potential of HCC cells which was reversed following reversal assay. Notably, during TGF-β1-induced EMT, there was upregulation of immune checkpoint molecules PD-L1 and B7-H3. However, the reversal of EMT decreased the expression of PD-L1 and B7-H3. In addition, TGF-β1 driven EMT was reversed following knockdown of B7-H3 in both HCC cells further validating the interplay between TGF-β1-mediated EMT and immune checkpoint expression in HCC. Furthermore, the coordinate expression of TGF-β1 with PD-L1 (p=0.01487) and B7-H3 (p=0.009687) was correlated with poor overall survival in 422 HCC patients. Our study has demonstrated a close association between TGF-β1-mediated EMT and regulation of immune checkpoints in HCC.

Epithelial/Mesenchymal Characteristics and PD-L1 Co-Expression in CTCs of Metastatic Breast Cancer Patients Treated with Eribulin: Correlation with Clinical Outcome

We aimed to evaluate the co-expression of PD-L1 and epithelial-mesenchymal markers in CTCs from metastatic breast cancer (MBC) patients and to determine if there is any relationship with patients' outcome after eribulin treatment. Using cytospin preparations of peripheral blood mononuclear cells (PBMCs) from MBC patients treated with eribulin and a combination of immunocytochemistry and immunofluorescence, we quantified PD-L1, keratins and vimentin in single and cluster CTCs on days 1 and 8 of the first-treatment cycle. CTCs (n = 173) were found in 31 out of 38 patients. At baseline, the presence of cluster CTCs (p = 0.048), cluster mesenchymal CTCs (mCTCs) (p = 0.0003) or cluster PD-L1⁺mCTCs (p = 0.006) was associated with shorter overall survival (OS). In multivariate cox regression analysis, the detection of cluster mCTCs was the only parameter associated with increased risk of death (p = 0.024). On day 8 post-eribulin administration, PD-L1⁺mCTCs and especially single PD-L1⁺mCTCs decreased in 75% and 89% of patients, respectively. The detection of single PD-L1⁺mCTCs after eribulin treatment was correlated with shorter PFS (p = 0.047) and OS (p = 0.020). In conclusion, our study identified for the first time that cluster and single PD-L1⁺mCTCs subpopulations are of clinical significance in patients with MBC and highlighted the importance of CTC phenotyping during treatment with eribulin.

Tumor-derived exosomes in the PD-1/PD-L1 axis: Significant regulators as well as promising clinical targets

Programmed cell death-1 (PD-1) is a negative coreceptor mainly expressed on the surface of activated T cells. The binding of PD-1 to its ligand PD-L1 significantly induces non-reactivity of T cells to maintain the balance of autoimmunity and immune tolerance. It is reported that tumor cells highly express PD-L1 to restrict cellular immune response, which is one of the most important mechanisms for tumor to mediate immune escape. Cancer immunotherapy targeting PD-1/PD-L1 has achieved remarkable success so far. Tumor-derived exosomes (TEXs) are lipid bilayer vesicles released by tumor cells in an endosome-dependent manner, mediating communication between tumor cells and adjacent cells in the tumor microenvironment. Through signals transmitted by TEXs, tumor can alter the biological characteristics of these cells to promote tumor growth and metastasis. Recent studies have demonstrated that TEXs not only carry tumor-derived PD-L1, but are also closely related to PD-1/PD-L1 expression on target cells. The primary focus of this review will be on how TEXs regulate the PD-1/PD-L1 axis to promote tumor progression, and the promising clinical applications targeting TEXs and exosomal PD-L1.

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.

Advances in Oligonucleotide Aptamers for NSCLC Targeting

Non-small-cell lung cancer (NSCLC) is the most common type of lung cancer worldwide, with the highest incidence in developed countries. NSCLC patients often face resistance to currently available therapies, accounting for frequent relapses and poor prognosis. Indeed, despite great recent advancements in the field of NSCLC diagnosis and multimodal therapy, most patients are diagnosed at advanced metastatic stage, with a very low overall survival. Thus, the identification of new effective diagnostic and therapeutic options for NSCLC patients is a crucial challenge in oncology. A promising class of targeting molecules is represented by nucleic-acid aptamers, short single-stranded oligonucleotides that upon folding in particular three dimensional (3D) structures, serve as high affinity ligands towards disease-associated proteins. They are produced in vitro by SELEX (systematic evolution of ligands by exponential enrichment), a combinatorial chemistry procedure, representing an important tool for novel targetable biomarker discovery of both diagnostic and therapeutic interest. Aptamer-based approaches are promising options for NSCLC early diagnosis and targeted therapy and may overcome the key obstacles of currently used therapeutic modalities, such as the high toxicity and patients’ resistance. In this review, we highlight the most important applications of SELEX technology and aptamers for NSCLC handling.

A New Method for CTC Images Recognition Based on Machine Learning

Circulating tumor cells (CTCs) derived from primary tumors and/or metastatic tumors are markers for tumor prognosis, and can also be used to monitor therapeutic efficacy and tumor recurrence. Circulating tumor cells enrichment and screening can be automated, but the final counting of CTCs currently requires manual intervention. This not only requires the participation of experienced pathologists, but also easily causes artificial misjudgment. Medical image recognition based on machine learning can effectively reduce the workload and improve the level of automation. So, we use machine learning to identify CTCs. First, we collected the CTC test results of 600 patients. After immunofluorescence staining, each picture presented a positive CTC cell nucleus and several negative controls. The images of CTCs were then segmented by image denoising, image filtering, edge detection, image expansion and contraction techniques using python’s openCV scheme. Subsequently, traditional image recognition methods and machine learning were used to identify CTCs. Machine learning algorithms are implemented using convolutional neural network deep learning networks for training. We took 2300 cells from 600 patients for training and testing. About 1300 cells were used for training and the others were used for testing. The sensitivity and specificity of recognition reached 90.3 and 91.3%, respectively. We will further revise our models, hoping to achieve a higher sensitivity and specificity.

Clinical Impact of the Epithelial-Mesenchymal Transition in Lung Cancer as a Biomarker Assisting in Therapeutic Decisions

Lung cancer is one of the most common solid cancers and represents the leading cause of cancer death worldwide. Over the last decade, research on the epithelial-mesenchymal transition (EMT) in lung cancer has gained increasing attention. Here, we review clinical and histological features of non-small-cell lung cancer associated with EMT. We then aimed to establish potential clinical implications of EMT in current therapeutic options, including surgery, radiation, targeted therapy against oncogenic drivers, and immunotherapy.

Interactive Effects of PD-L1 Expression in Tumor and Immune Cells on Prognosis of Esophageal Squamous Cell Carcinoma: A One-Center Retrospective Cohort Study

Purpose

The present study aimed to investigate the prognostic effect of PD-L1 expressing in tumor and immune cells among patients with esophageal squamous cell carcinoma.

Patients and Methods

We performed a retrospective cohort study by consecutively recruiting 142 patients. The clinicopathological features and PD-L1 expression on tumor and immune cells were independently evaluated by two pathologists.

Results

The median expression rate of PD-L1 was 5% and 30% in tumor and immune cells, respectively. Patients with higher expression of PD-L1 in tumor cells had shorter disease-free and overall survival, and the HRs were 1.52 for relapse (95% CI: 0.88, 2.60) and 1.48 for death (95% CI: 0.82, 2.69). There was no significant association between the PD-L1 expression in immune cells and survival. However, among the patients with PD-L1 expression rate ≤30% in immune cells, the high expression rate of PD-L1 in tumor cells was significantly associated with the relapse and death, with HRs of 2.51 (95% CI: 1.25, 5.06) and 3.51 (95% CI: 1.57, 7.85), respectively. Among patients with PD-L1 expression rate >30% in immune cells, the PD-L1 expression in tumor cells did not show any association with the disease-free and overall survival.

Conclusion

Our study demonstrates that the integration of PD-L1 expression in tumor and immune cells could be used to predict the relapse and survival among patients with esophageal squamous cell carcinoma.

EMT-Associated Heterogeneity in Circulating Tumor Cells: Sticky Friends on the Road to Metastasis

Epithelial-mesenchymal transitions (EMTs) generate hybrid phenotypes with an enhanced ability to adapt to diverse microenvironments encountered during the metastatic spread. Accordingly, EMTs play a crucial role in the biology of circulating tumor cells (CTCs) and contribute to their heterogeneity. Here, we review major EMT-driven properties that may help hybrid Epithelial/Mesenchymal CTCs to survive in the bloodstream and accomplish early phases of metastatic colonization. We then discuss how interrogating EMT in CTCs as a companion biomarker could help refine cancer patient management, further supporting the relevance of CTCs in personalized medicine.