PD-L1+ aneuploid circulating tumor endothelial cells (CTECs) exhibit resistance to the checkpoint blockade immunotherapy in advanced NSCLC patients

Circulating Tumor Microenvironment in Metastasis

Activation of invasion and metastasis is a central hallmark of cancer, contributing to the primary cause of death for patients with cancer. In the multistep metastatic process, cancer cells must infiltrate the circulation, survive, arrest at capillary beds, extravasate, and form metastatic clones in distant organs. However, only a small proportion of circulating tumor cells (CTC) successfully form metastases, with transit of CTCs in the circulation being the rate-limiting step. The fate of CTCs is influenced by the circulating tumor microenvironment (cTME), which encompasses factors affecting their biological behaviors in the circulation. This liquid and flowing microenvironment differs significantly from the primary TME or the premetastatic niche. This review summarizes the latest advancements in identifying the biophysical cues, key components, and biological roles of the cTME, highlighting the network among biophysical attributes, blood cells, and nonblood factors in cancer metastasis. In addition to the potential of the cTME as a therapeutic target for inhibiting metastasis, the cTME could also represent as a biomarker for predicting patient outcomes and developing strategies for treating cancer.

Unveiling the immunomodulatory dance: endothelial cells' function and their role in non-small cell lung cancer

The dynamic interactions between tumor endothelial cells (TECs) and the immune microenvironment play a critical role in the progression of non-small cell lung cancer (NSCLC). In general, endothelial cells exhibit diverse immunomodulatory properties, influencing immune cell recruitment, antigen presentation, and regulation of immune checkpoint expression. Understanding the multifaceted roles of TECs as well as assigning specific functional hallmarks to various TEC phenotypes offer new avenues for targeted development of therapeutic interventions, particularly in the context of advanced immunotherapy and anti-angiogenic treatments. This review provides insights into the complex interplay between TECs and the immune system in NSCLC including discussion of potential optimized therapeutic opportunities.

The Presence of Small-Size Circulating Tumor Cells Predicts Worse Prognosis in Non-Small Cell Lung Cancer Patients

CONTEXT.—

Most patients with non-small cell lung cancers (NSCLC) are diagnosed at advanced stages. The 5-year survival rate of patients with advanced lung cancer is less than 20%, which makes lung cancer the leading cause of cancer-related deaths worldwide.

OBJECTIVE.—

To identify indicators that can predict the prognosis of lung cancer patients.

DESIGN.—

To determine the correlation between circulating tumor cells (CTCs), circulating tumor-derived endothelial cells (CTECs), and their subtypes and the prognosis of patients with NSCLC, 80 patients with lung cancer were recruited and 48 patients who met the enrollment criteria were selected in this study. Peripheral blood was collected from the enrolled patients before any treatment and analyzed by the subtraction enrichment and immunostaining-fluorescence in situ hybridization technique to determine the correlation between CTCs and CTECs and lung cancer disease progression and to identify prognostic indicators.

RESULTS.—

In all patients, the positive rate of CTCs was 100% and the positive rate of CTECs was 81.3%. Patients with advanced or lymph node metastases had a higher rate of small-size CTC positivity than those with early or no lymph node metastases. Large-size CTEC positivity was higher in patients with advanced NSCLC than in early-stage patients (P = .03). Patients with ≥1 small-size CTC had shorter progression-free survival, and it was an independent prognostic factor.

CONCLUSIONS.—

Small-size CTCs are a reliable prognostic indicator and a probable predictor of the severity of disease in NSCLC patients.

Aneuploid Circulating Endothelial Cells with Prognostic Value in Locally Advanced Breast Cancer Patients After Neoadjuvant Chemotherapy

Background

Aneuploid circulating endothelial cells (CECs) are an indicator in breast cancer (BC). Significant changes of aneuploid CECs occurred during neoadjuvant chemotherapy (NCT). This study aimed to explore the predictive and prognostic values of aneuploid CECs in locally advanced breast cancer (LABC) patients with different NCT responses.

Methods

Breast cancer patients received an EC4-T4 NCT regimen. A novel subtraction enrichment and immunostaining fluorescence in situ hybridization (SE-iFISH) strategy was applied for the detection of CECs (CD45-/CD31+/DAPI+). Receiver operating characteristic (ROC) curves were plotted to evaluate the predictive value of aneuploid CEC counts in distinguishing NCT-resistant patients from sensitive ones. All patients were observed for progression-free survival (PFS) and overall survival (OS).

Results

The CEC counts at any time point did not show the ability to predict the efficacy of NCT. The difference in the CECs between post-chemotherapy levels and baseline could be sufficient to distinguish chemotherapy-resistant cases from other cases in Hormone+Her-2-/+ (HR+) BC patients. Patients with reduction of CECs after all courses of NCT were associated with higher probability of PFS.

Conclusion

Variations in aneuploid CECs during NCT may predict chemotherapy response in patients with HR+ breast cancer. The decrease in the number of aneuploid CECs after all courses of NCT indicates better treatment outcomes in patients with LABC.

Biphasic co-detection of melanoma aneuploid tumor cells and tumor endothelial cells in guidance of specifying the field cancerized surgical excision margin and administering immunotherapy

An optimum safety excision margin (EM) delineated by precise demarcation of field cancerization along with reliable biomarkers that enable predicting and timely evaluating patients' response to immunotherapy significantly impact effective management of melanoma. In this study, optimized biphasic "immunofluorescence staining integrated with fluorescence insitu hybridization" (iFISH) was conducted along the diagnosis-metastasis-treatment-cellular MRD axis to longitudinally co-detect a full spectrum of intact CD31- aneuploid tumor cells (TCs), CD31+ aneuploid tumor endothelial cells (TECs), viable and necrotic circulating TCs (CTCs) and circulating TECs (CTECs) expressing PD-L1, Ki67, p16 and Vimentin in unsliced specimens of the resected primary tumor, EM, dissected sentinel lymph nodes (SLNs) and peripheral blood in an early-stage melanoma patient. Numerous PD-L1+ aneuploid TCs and TECs were detected at the conventional safety EM (2 cm), quantitatively indicating the existence of a field cancerized EM for the first time. Contrary to highly heterogeneous PD-L1 expression and degrees of Chr8 aneuploidy in TCs and TECs in the primary lesions as well as CTCs and CTECs in peripheral blood, almost all TCs and TECs in SLNs and EM were homogeneously PD-L1+ haploid cells. Dynamic monitoring and cellular MRD assessment revealed that, in contrast to PD-L1+ CTCs being responsive to the immune checkpoint inhibitor (ICI-anti-PD-1), multiploid (≥pentasomy 8) PD-L1+ and Ki67+ CTECs were respectively resistant to ICI-sensitized T cells. In therapeutically stressed lymphatic and hematogenous metastatic cascades, stratified phenotypic and karyotypic profiling of iFISH tissue and liquid biopsied TCs, TECs, CTCs and CTECs in future large-cohort studies will enable appropriate re-specification of the optimal safety EM and distribution mapping of in-depth characterized, subcategorized target cells to help illustrate their metastatic relevance, ultimately improving risk stratification and clinical intervention of tumor progression, metastases, therapy resistance and cancer relapse.

The complex interplay of tumor-infiltrating cells in driving therapeutic resistance pathways

Drug resistance remains a significant challenge in cancer treatment. Recently, the interactions among various cell types within the tumor microenvironment (TME) have deepened our understanding of the mechanisms behind treatment resistance. Therefore, this review aims to synthesize current research focusing on infiltrating cells and drug resistance suggesting that targeting the TME could be a viable strategy to combat this issue. Numerous factors, including inflammation, metabolism, senescence, hypoxia, and angiogenesis, contribute to drug resistance could be a viable strategy to combat this issue. Overexpression of STAT3 is commonly associated with drug-resistant cancer cells or stromal cells. Current research often generalizes the impact of stromal cells on resistance, lacking specificity and statistical robustness. Thus, future research should take notice of this issue and aim to provide high-quality evidence. Despite the existing limitations, targeting the TME to overcome therapy resistance hold promising and valuable potential.

Angiogenesis and Ovarian Cancer: What Potential Do Different Subtypes of Circulating Endothelial Cells Have for Clinical Application?

Ovarian cancer (OC) remains the most fatal disease of gynaecologic malignant tumours. The neovasculature in the tumour microenvironment principally comprises endothelial cells. Haematogenous cancer metastases are significantly impacted by tumour neovascularisation, which predominantly depends on the tumour-derived endothelial vasculogenesis. There is an urgent need for biomarkers for the diagnosis, prognosis and prediction of drug response. Endothelial cells play a key role in angiogenesis and other forms of tumour vascularisation. Subtypes of circulating endothelial cells may provide interesting non-invasive biomarkers of advanced OC that might have the potential to be included in clinical analysis for patients' stratification and therapeutic management. In this review, we summarise the reported studies on circulating endothelial subtypes in OC, detailing their isolation methods as well as their potential diagnostic, prognostic, predictive and therapeutic utility for clinical application. We highlight key biomarkers for the identification of circulating endothelial cell subtypes and their targets for therapies and critically point out future challenges.

PRKDC-Mediated NHEJ May Play a Crucial Role in Aneuploidy of Chromosome 8-Driven Progression of Ovarian Cancer

High malignancy is a prominent characteristic of epithelial ovarian cancer (EOC), emphasizing the necessity for further elucidation of the potential mechanisms underlying cancer progression. Aneuploidy and copy number variation (CNV) partially contribute to the heightened malignancy observed in EOC; however, the precise features of aneuploidy and their underlying molecular patterns, as well as the relationship between CNV and aneuploidy in EOC, remain unclear. In this study, we employed single-cell sequencing data along with The Cancer Genome Atlas (TCGA) to investigate aneuploidy and CNV in EOC. The technique of fluorescence in situ hybridization (FISH) was employed using specific probes. The copy number variation within the genomic region of chromosome 8 (42754568-47889815) was assessed and utilized as a representative measure for the ploidy status of individual cells in chromosome 8. Differential expression analysis was performed between different subgroups based on chromosome 8 ploidy. Gene ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), protein-protein interaction (PPI), and hub-gene analyses were subsequently utilized to identify crucial genes involved. By classifying enriched tumor cells into distinct subtypes based on chromosome 8 ploidy combined with TCGA data integration, we identified key genes driving chromosome 8 aneuploidy in EOC, revealing that PRKDC gene involvement through the mediated non-homologous end-joining pathway may play a pivotal role in disease progression. Further validation through analysis of the GEO and TCGA database and survival assessment, considering both mRNA expression levels and CNV status of PRKDC, has confirmed its involvement in the progression of EOC. Further functional analysis revealed an upregulation of PRKDC in both ovarian EOC cells and tissues, with its expression showing a significant correlation with the extent of copy number variation (CNV) on chromosome 8. Taken together, CNV amplification and aneuploidy of chromosome 8 are important characteristics of EOC. PRKDC and the mediated NHEJ pathway may play a crucial role in driving aneuploidy on chromosome 8 during the progression of EOC.

Liquid biopsy in lung cancer

Lung cancer is a highly prevalent malignancy worldwide and the primary cause of mortality. The absence of systematic and standardized diagnostic approaches for identifying potential pulmonary nodules, early-stage cancers, and indeterminate tumors has led clinicians to consider tissue biopsy and pathological sections as the preferred method for clinical diagnosis, often regarded as the gold standard. The conventional tissue biopsy is an invasive procedure that does not adequately capture the diverse characteristics and evolving nature of tumors. Recently, the concept of 'liquid biopsy' has gained considerable attention as a promising solution. Liquid biopsy is a non-invasive approach that facilitates repeated analysis, enabling real-time monitoring of tumor recurrence, metastasis, and response to treatment. Currently, liquid biopsy includes circulating tumor cells, circulating cell-free DNA, circulating tumor DNA, circulating cell-free RNA, extracellular vesicles, and other proteins and metabolites. With rapid progress in molecular technology, liquid biopsy has emerged as a highly promising and intriguing approach, yielding compelling results. This article critically examines the significant role and potential clinical implications of liquid biopsy in the diagnosis, treatment, and prognosis of lung cancer.

Tracking circulating PD-L1-positive cells to monitor the outcome of patients with gastric cancer receiving anti-HER2 plus anti-PD-1 therapy

Dual blockade of HER2 and PD-1/PD-L1 is the most promising regimen for HER2-positive patients with gastric cancer (GC); PD-L1 combined positive score, rather than HER2 status, indicates potential benefit. Circulating tumor cells (CTCs) and circulating endothelial cells (CECs) derived from the tumor microenvironment provide platforms for the dynamic evaluation of PD-L1 expression. Whether PD-L1 positive CTCs/CECs (PD-L1+CTCs/CECs) can serve as biomarkers for evaluating the efficacy of combination therapy remains unknown. Therefore, this study investigated PD-L1 expression and heterogeneous karyotypic features of CTCs/CECs and their involvement in the clinical response to treatment in 72 patients with advanced GC by applying a pre-established surface molecule-independent subtraction enrichment (SE)-iFISH strategy. In the captured PD-L1 positive cells, there were 42.80% and 57.20% of CTCs and CECs, respectively. PD-L1+ CTCs were pre-therapeutically detected in 0% (0/11) of HER2-negative patients and 14.75% (9/61) of HER2-positive patients. The presence of baseline PD-L1+CTCs was relevant to inferior prognosis (mPFS: 14.40 months vs 5.00 months, P = 0.065); post-treatment PD-L1+ CECs were associated with longer irPFS (immunotherapeutic-related PFS) (mPFS: 15.57 months vs 6.73 months, P = 0.053). Further dynamic karyotype-based profiling of PD-L1+ CTCs/CECs indicated that multiploidy and triploidy were the dominant subtypes of baseline PD-L1+ CTCs, and that triploidy was specifically associated with therapeutic resistance. Intratherapeutically detected multiploid PD-L1+ CECs demonstrated a superior clinical response; triploidy and tetraploidy contributed to acquired resistance. The karyotypic features of PD-L1+CTCs/CECs should be dynamically profiled in patients with GC treated with anti-HER2 plus anti-PD-1 therapy. Triploid-PD-L1+ CTCs and multiploid-PD-L1+ CECs are potential indicators of therapeutic response.

Prognostic significance of blood-based PD-L1 analysis in patients with non-small cell lung cancer undergoing immune checkpoint inhibitor therapy: a systematic review and meta-analysis

BACKGROUND

The main types of PD-L1 in the blood include soluble PD-L1 (sPD-L1), exosomal PD-L1 (exoPD-L1), and PD-L1 in circulating tumor cells (CTCs). However, the predictive and prognostic values of these three indicators in patients with non-small cell lung cancer (NSCLC) undergoing immune checkpoint inhibitor (ICI) therapy are unclear, warranting a systematic meta-analysis.

METHODS

A systematic literature search was performed in the PubMed, Cochrane Library, and Embase databases. The pooled hazard ratio (HR) and 95% confidence interval (CI) values were extracted from the included studies to investigate the correlation between the three PD-L1 indicators and overall survival (OS) or progression-free survival (PFS). The Newcastle-Ottawa Scale (NOS) was used to examine the quality of the included studies. Subgroup analyses were employed to investigate the heterogeneity. The publication bias of the included studies was assessed using Begg's and Egger's tests. P < 0.05 was regarded as significantly different.

RESULTS

The pooled results revealed that high pre-treatment sPD-L1 levels were significantly associated with inferior OS (HR = 2.32, 95% CI = 1.68-3.18, P < 0.001) and PFS (HR = 2.52, 95% CI = 1.72-3.68, P < 0.001). However, dynamic changes in sPD-L1 after immunotherapy were not statistically significant for OS (HR = 1.46, 95% CI = 0.65-3.26, P > 0.05) or PFS (HR = 1.62, 95% CI = 0.92-2.86, P > 0.05). Meanwhile, the upregulated pre-treatment exoPD-L1 levels were significantly associated with poor PFS (HR = 4.44, 95% CI = 2.87-6.89, P < 0.001), whereas the post-treatment dynamic upregulation of exoPD-L1 was significantly correlated with superior PFS (HR = 0.36, 95% CI = 0.24-0.54, P < 0.001) and OS (HR = 0.20, 95% CI = 0.07-0.53, P < 0.001). For PD-L1 in CTCs, the pooled results indicated that PD-L1 expression in CTCs was not significantly correlated with OS (HR = 0.75, 95% CI = 0.49-1.13, P = 0.170) and PFS (HR = 0.79, 95% CI = 0.59-1.06, P = 0.12).

CONCLUSIONS

Blood-based PD-L1 analysis is a potential strategy for predicting treatment efficacy and prognosis in patients with cancer.

Mapping the protein-protein interactome in the tumor immune microenvironment

The cell-to-cell communication primarily occurs through cell-surface and secreted proteins, which form a sophisticated network that coordinates systemic immune function. Uncovering these protein-protein interactions (PPIs) is indispensable for understanding the molecular mechanism and elucidating immune system aberrances under diseases. Traditional biological studies typically focus on a limited number of PPI pairs due to the relative low throughput of commonly used techniques. Encouragingly, classical methods have advanced, and many new systems tailored for large-scale protein-protein screening have been developed and successfully utilized. These high-throughput PPI investigation techniques have already made considerable achievements in mapping the immune cell interactome, enriching PPI databases and analysis tools, and discovering therapeutic targets for cancer and other diseases, which will definitely bring unprecedented insight into this field.

Non-immune cell components in tumor microenvironment influencing lung cancer Immunotherapy

Lung cancer (LC) is one of the leading causes of cancer-related deaths worldwide, with a significant morbidity and mortality rate, endangering human life and health. The introduction of immunotherapies has significantly altered existing cancer treatment strategies and is expected to improve immune responses, objective response rates, and survival rates. However, a better understanding of the complex immunological networks of LC is required to improve immunotherapy efficacy further. Tumor-associated antigens (TAAs) and tumor-specific antigens (TSAs) are significantly expressed by LC cells, which activate dendritic cells, initiate antigen presentation, and activate lymphocytes to exert antitumor activity. However, as tumor cells combat the immune system, an immunosuppressive microenvironment forms, enabling the enactment of a series of immunological escape mechanisms, including the recruitment of immunosuppressive cells and induction of T cell exhaustion to decrease the antitumor immune response. In addition to the direct effect of LC cells on immune cell function, the secreting various cytokines, chemokines, and exosomes, changes in the intratumoral microbiome and the function of cancer-associated fibroblasts and endothelial cells contribute to LC cell immune escape. Accordingly, combining various immunotherapies with other therapies can elicit synergistic effects based on the complex immune network, improving immunotherapy efficacy through multi-target action on the tumor microenvironment (TME). Hence, this review provides guidance for understanding the complex immune network in the TME and designing novel and effective immunotherapy strategies for LC.

Longitudinal detection of subcategorized CD44v6+ CTCs and circulating tumor endothelial cells (CTECs) enables novel clinical stratification and improves prognostic prediction of small cell lung cancer: A prospective, multi-center study

Current management of small cell lung cancer (SCLC) remains challenging. Effective biomarkers are needed to subdivide patients presenting distinct treatment response and clinical outcomes. An understanding of heterogeneous phenotypes of aneuploid CD31- circulating tumor cells (CTCs) and CD31+ circulating tumor endothelial cells (CTECs) may provide novel insights in the clinical management of SCLC. In the present translational and prospective study, increased cancer metastasis-related cell proliferation and motility, accompanied with up-regulated mesenchymal marker vimentin but down-regulated epithelial marker E-cadherin, were observed in both lentivirus infected SCLC and NSCLC cells overexpressing the stemness marker CD44v6. Aneuploid CTCs and CTECs expressing CD44v6 were longitudinally detected by SE-iFISH in 120 SCLC patients. Positive detection of baseline CD44v6+ CTCs and CD44v6+ CTECs was significantly associated with enhanced hepatic metastasis. Karyotype analysis revealed that chromosome 8 (Chr8) in CD44v6+ CTCs shifted from trisomy 8 towards multiploidy in post-therapeutic patients compared to pre-treatment subjects. Furthermore, the burden of baseline CD44v6+ CTCs (t0) or amid the therapy (t1-2), the ratio of baseline CD31+ CTEC/CD31- CTC (t0), and CTC-WBC clusters (t0) were correlated with treatment response and distant metastases, particularly brain metastasis, in subjects with limited disease (LD-SCLC) but not in those with extensive disease (ED-SCLC). Multivariate survival analysis validated that longitudinally detected CD44v6+/CD31- CTCs was an independent prognostic factor for inferior survival in SCLC patients. Our study provides evidence for the first time that comprehensive analyses of CTCs, CTECs, and their respective CD44v6+ subtypes enable clinical stratification and improve prognostic prediction of SCLC, particularly for potentially curable LD-SCLC.

Post-therapeutic circulating tumor cell-associated white blood cell clusters predict poor survival in patients with advanced driver gene-negative non-small cell lung cancer

PURPOSE

This study aimed to investigate the clinical utility of diverse aneuploid circulating tumor cell (CTC) subtypes and particularly CTC-associated white blood cell (CTC-WBC) clusters in predicting treatment response, prognosis and real-time monitoring disease progression in advanced driver gene-negative non-small lung cancer (NSCLC) patients.

MATERIALS AND METHODS

A total of 74 eligible patients were prospectively enrolled and serial blood samples were collected at pre-treatment(t₀), after two cycles of therapy (t₁) and at post-four-to-six treatment cycles (t₂). Co-detection of diverse subtypes of aneuploid CTCs and CTC-WBC clusters was conducted in advanced NSCLC patients receiving first-line treatment.

RESULTS

At baseline, CTCs were detected in 69 (93.24%) patients and CTC-WBC clusters were detected in 23 (31.08%) patients. Patients with CTCs < 5/6ml or with CTC-WBC clusters undetectable exhibited a better treatment response than patients with pre-therapeutic aneuploid CTCs ≥ 5/6ml or harboring CTC-WBC clusters (p = 0.034 and p = 0.012, respectively). Before treatment, patients bearing tetraploid CTCs ≥ 1/6ml showed significantly inferior progression-free survival (PFS) [hazard ratio (HR):2.420, 95% confidence interval (CI): 1.426-4.106; p = 0.001] and overall survival (OS) compared to patients with tetraploid CTCs < 1/6ml (HR:1.907, 95%CI: 1.119-3.251; p = 0.018). A longitudinal study demonstrated that post-therapeutic patients harboring CTC-WBC clusters displayed the reduced PFS and OS compared with those without CTC-WBC clusters, and subgroup analysis showed that the presence of CTC-WBC clusters indicated a worse prognosis in both lung adenocarcinoma (LUAD) and lung squamous cell carcinoma (LUSC) patients. After adjusting for multiple significant factors, post-therapeutic CTC-WBC clusters were the only independent predictor of both PFS (HR:2.872, 95% CI: 1.539-5.368; p = 0.001) and OS (HR:2.162, 95% CI: 1.168-4.003; p = 0.014).

CONCLUSIONS

In addition to CTCs, longitudinal detection of CTC-WBC clusters provided a feasible tool to indicate initial treatment response, dynamically monitor disease progression and predict survival in driver gene-negative advanced NSCLC patients.

Tumour associated endothelial cells: origin, characteristics and role in metastasis and anti-angiogenic resistance

Tumour progression and metastasis remain the leading causes of cancer-related death worldwide. Tumour angiogenesis is essential for tumour progression. The vasculature surrounding tumours is not only a transport channel for nutrients, oxygen, and metabolites, but also a pathway for metastasis. There is a close interaction between tumour cells and endothelial cells in the tumour microenvironment. Recent studies have shown that tumour-associated endothelial cells have different characteristics from normal vascular endothelial cells, play an important role in tumour progression and metastasis, and are expected to be a key target for cancer therapy. This article reviews the tissue and cellular origin of tumour-associated endothelial cells and analyses the characteristics of tumour-associated endothelial cells. Finally, it summarises the role of tumour-associated endothelial cells in tumour progression and metastasis and the prospects for their use in clinical anti-angiogenic therapy.

Soluble biomarkers to predict clinical outcomes in non-small cell lung cancer treated by immune checkpoints inhibitors

Lung cancer remains the first cause of cancer-related death despite many therapeutic innovations, including immune checkpoint inhibitors (ICI). ICI are now well used in daily practice at late metastatic stages and locally advanced stages after a chemo-radiation. ICI are also emerging in the peri-operative context. However, all patients do not benefit from ICI and even suffer from additional immune side effects. A current challenge remains to identify patients eligible for ICI and benefiting from these drugs. Currently, the prediction of ICI response is only supported by Programmed death-ligand 1 (PD-L1) tumor expression with perfectible results and limitations inherent to tumor-biopsy specimen analysis. Here, we reviewed alternative markers based on liquid biopsy and focused on the most promising biomarkers to modify clinical practice, including non-tumoral blood cell count such as absolute neutrophil counts, platelet to lymphocyte ratio, neutrophil to lymphocyte ratio, and derived neutrophil to lymphocyte ratio. We also discussed soluble-derived immune checkpoint-related products such as sPD-L1, circulating tumor cells (detection, count, and marker expression), and circulating tumor DNA-related products. Finally, we explored perspectives for liquid biopsies in the immune landscape and discussed how they could be implemented into lung cancer management with a potential biological-driven decision.

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.

Circulating tumor cells PD-L1 expression detection and correlation of therapeutic efficacy of immune checkpoint inhibition in advanced non-small-cell lung cancer

INTRODUCTION

This study investigated whether programmed death-ligand 1 (PD-L1) expression of circulating tumor cells (CTCs) in peripheral blood can serve as a predictive biomarker for immunotherapy efficacy in patients with advanced non-small-cell lung cancer (NSCLC).

METHODS

We employed a negative enrichment method to isolate CTCs. We identified PD-L1 + CTCs as PD-L1+/4',6-diamidino-2-phenylindole (DAPI)+/CD45-circulating tumor cells through an immunofluorescence method. Tumor tissue PD-L1 expression was determined by immunohistochemical staining. The correlation between CTC PD-L1 expression and patients' prognostic features was estimated through the Kaplan-Meier method.

RESULTS

CTCs released a higher detection rate of PD-L1 expression than tumor tissues (53.0% vs. 42.1%). No correlation was observed between them. Forty-nine NSCLC patients received anti-PD-1/PD-L1 immunotherapy (three with combined anti-PD-1/PD-L1 and cytotoxic T lymphocyte-associated antigen-4 (CTLA-4), two with four cycles of combined immune checkpoint inhibitors [ICIs] plus chemotherapy and ICI monotherapy for maintenance). Patients with PD-L1 expression on tissue or CTCs had a median progression-free survival (mPFS) of 5.6 months (n = 36, 95% confidence interval [CI] 3.6-7.5 months), significantly longer than those without PD-L1 detection (n = 9, mPFS of 1.4 months, 95% CI 1.3-1.5 months, log-rank p = 0.032). The multivariable Cox proportional-hazard model suggested that the tissue or CTC PD-L1 expression was associated with a lower risk of progression (hazard ratio 0.45, 95% CI 0.21-0.98, p = 0.043).

CONCLUSIONS

CTCs and tumor tissues reveal heterogeneous expression of PD-L1 in NSCLC patients. Patients with baseline PD-L1 expression on CTCs or tissue showed prolonged mPFS and may help to identify the subsets of patients who potentially benefit from immunotherapy.

Liquid Biopsy and Immuno-Oncology for Advanced Nonsmall Cell Lung Cancer

BACKGROUND

In the last decade, immune checkpoint inhibitors have revolutionized the treatment of metastatic nonsmall cell lung cancer without oncogenic addiction. Currently, programmed death ligand 1 (PD-L1) status, assessed in tissue biopsy samples, is the only test for guiding the prescription of these therapies in clinical practice. However, obtaining tumor tissue from patients with lung cancer is not always feasible and PD-L1 positivity is not a guarantee of immunotherapy efficacy. In this context, liquid biopsy, represented by several circulating biomarkers that reflect the tumor characteristics, is emerging as an interesting alternative approach.

CONTENT

We describe the main blood biomarkers evaluated in patients with metastatic nonsmall cell lung cancer before/during immune checkpoint inhibitor treatment, with a focus on circulating cell-free DNA, circulating tumor DNA (ctDNA), blood tumor mutational burden, and circulating tumor cells (CTCs).

SUMMARY

Monitoring of ctDNA and CTCs during immunotherapy may be a promising tool to help clinicians in therapeutic decision-making.

Aneuploid subtypes of circulating tumor cells and circulating tumor-derived endothelial cells predict the overall survival of advanced lung cancer

Objective

This study aimed to detect circulating tumor cells (CTCs) and circulating tumor-derived endothelial cells (CTECs) in patients with advanced lung cancer, for describing the distribution characteristics of CTC and CTEC subtypes, exploring the correlation between CTC/CTEC subtypes and novel prognostic biomarkers.

Methods

A total of 52 patients with advanced lung cancer were enrolled in this study. Using the subtraction enrichment-immunofluorescence in situ hybridization (SE-iFISH) system, CTCs and CTECs derived from these patients were identified.

Results

Based on cell size, there were 49.3% small and 50.7% large CTCs, and 23.0% small and 77.0% large CTECs. Triploidy, tetraploidy, and multiploidy varied in the small and large CTCs/CTECs. Besides these three aneuploid subtypes, monoploidy was found in the small and large CTECs. Triploid and multiploid small CTCs and tetraploid large CTCs were associated with shorter overall survival (OS) in patients with advanced lung cancer. However, none of the CTECs subtypes showed a significant correlation with patient prognosis. In addition, we found strong positive correlations (P<0.0001) in the four groups including triploid small cell size CTCs and multiploid small cell size CTECs, and multiploid small cell size CTCs and monoploid small cell size CTECs. Furthermore, combined detection of the specific subtypes, including triploid small CTC and monoploid small CTEC, triploid small CTC and triploid small CTEC, and multiploid small CTC and monoploid small CTEC, were associated with poor prognosis in advanced lung cancer.

Conclusions

Aneuploid small CTCs are associated with the outcome of patients with advanced lung cancer. In particular, the combined detection of triploid small CTCs and monoploid small CTECs, triploid small CTCs and triploid small CTECs, and multiploid small CTCs and monoploid small CTECs has clinical significance for predicting prognosis in patients with advanced lung cancer.

Detection of Circulating Tumor Cells Using the Attune NxT

Circulating tumor cells (CTCs) have been detected in many patients with different solid malignancies. It has been reported that presence of CTCs correlates with worse survival in patients with multiple types of cancer. Several techniques have been developed to detect CTCs in liquid biopsies. Currently, the only method for CTC detection that is approved by the Food and Drug Administration is CellSearch. Due to low abundance of CTCs in certain cancer types and in early stages of disease, its clinical application is currently limited to metastatic colorectal cancer, breast cancer and prostate cancer. Therefore, we aimed to develop a new method for the detection of CTCs using the Attune NxT-a flow cytometry-based application that was specifically developed to detect rare events in biological samples without the need for enrichment. When healthy donor blood samples were spiked with variable amounts of different EpCAM+EGFR+ tumor cell lines, recovery yield was on average 75%. The detection range was between 1000 and 10 cells per sample. Cell morphology was confirmed with the Attune CytPix. Analysis of blood samples from metastatic colorectal cancer patients, as well as lung cancer patients, demonstrated that increased EpCAM+EGFR+ events were detected in more than half of the patient samples. However, most of these cells showed no (tumor) cell-like morphology. Notably, CellSearch analysis of blood samples from a subset of colorectal cancer patients did not detect CTCs either, suggesting that these blood samples were negative for CTCs. Therefore, we anticipate that the Attune NxT is not superior to CellSearch in detection of low amounts of CTCs, although handling and analysis of samples is easier. Moreover, morphological confirmation is essential to distinguish between CTCs and false positive events.

Emerging Insights on Immunotherapy in Liver Cancer

Significance: Hepatocellular carcinoma (HCC) is a liver malignancy with high mortality rate, limited treatment options, and poor prognosis. Sorafenib has been the only systemic treatment option for patients with advanced HCC for more than a decade. HCC is a typical inflammation-related tumor with a distinct immunosuppressive microenvironment especially the upregulation of immune checkpoints. Recent Advances: Immunotherapy has shown persistent and powerful efficacy in HCC treatment. Several preclinical and clinical studies have prompted the application of immunotherapy in first-line, second-line, and postline treatment of HCC, which has profoundly shifted the paradigm for advanced HCC treatment in the past few years. Critical Issues and Future Directions: Major unaddressed challenges in HCC immunotherapy include the discovery and validation of biological markers that predict the efficacy, the application of immunotherapy in patients with impaired liver function and nonalcoholic steatohepatitis-associated HCC, and the exploration of immunotherapy combinations with better effectiveness. This review provides the latest advances in the research of immune microenvironment and immunotherapy in HCC. Antioxid. Redox Signal. 37, 1325-1338.

Biomarkers for response to immunotherapy in hepatobiliary malignancies

BACKGROUND

The advent of immune checkpoint inhibitors (ICIs) has revolutionized the therapeutic options of hepatobiliary malignancies. However, the clinical benefit provided by immunotherapy seems limited to a small subgroup of patients with hepatobiliary malignancies. The identification of reliable predictors of the response to immunotherapy is urgently needed.

DATA SOURCES

Literature search was conducted in PubMed for relevant articles published up to May 2022. Information of clinical trials was obtained from https://clinicaltrials.gov/.

RESULTS

Biomarkers for ICI response of hepatobiliary malignancies remain in the exploration stage and lack compelling evidence. Tumor programmed death-ligand 1 (PD-L1) expression is the most widely studied biomarker in hepatocellular carcinoma (HCC) and biliary tract cancers (BTCs), but there are conflicting results on its predictive potential. Tumor mutational burden (TMB) is generally low both in HCC and BTCs, and the clinical trials of TMB are rare in hepatobiliary malignancies. Promisingly, mismatch repair deficiency (dMMR)/high microsatellite instability (MSI-H) may be a predictive biomarker of response to anti-PD-1 therapy in BTCs. Furthermore, some emerging biomarkers, such as gut microbiota, show predictive potential in the preliminary studies. Radiomics and liquid-biopsy biomarkers, including circulating tumor cells, circulating tumor DNA (ctDNA) and exosomal PD-L1 provide a quick and non-invasive approach for monitoring the ICI response, showing a new promising direction.

CONCLUSIONS

Multiple potential biomarkers for predicting ICI response of hepatobiliary malignancies have been explored and tried to apply in clinic. Yet there is no robust evidence to prove their clinical value in predicting immunotherapeutic response for patients with hepatobiliary malignancies. The identification of predictors for response to ICIs is an urgent need and major challenge. Further studies are warranted to validate the role of emerging biomarkers in predicting immunotherapeutic responses.

Case report: Post-therapeutic laryngeal carcinoma patient possessing a high ratio of aneuploid CTECs to CTCs rapidly developed de novo malignancy in pancreas

Effectively evaluating therapeutic efficacy, detecting minimal residual disease (MRD) after therapy completion, and predicting early occurrence of malignancy in cancer patients remain as unmet imperative clinical demands. This article presents a case of a laryngeal carcinoma patient who had a surgical resection and complete post-operative chemoradiotherapy in combination with the targeted therapy, then rapidly developed pancreatic adenocarcinoma. Detected by SE-iFISH, the patient had a substantial amount of 107 non-hematological aneuploid circulating rare cells including 14 circulating tumor cells (CTCs, CD31-/CD45-) and 93 circulating tumor endothelial cells (CTECs, CD31+/CD45-) with a high ratio of CTECs/CTCs &gt; 5 upon finishing post-surgical combination regimens. Positive detection of those aneuploid non-hematological circulating rare cells was five months prior to subsequent plasma CA19-9 increasing and ten months before the de novo pancreatic cancer was diagnosed by medical imaging modalities. Besides previously reported clinical utilities of co-detection of aneuploid CD31- CTCs and CD31+ CTECs in real-time evaluation of therapeutic efficacy, longitudinal monitoring of emerging treatment resistance and adequate detection of MRD, a large cohort study is necessary to further investigate whether, and how, a high ratio of MRD CTECs to CTCs may function as an appropriate index forecasting either occurrence or metastatic distant recurrence of malignancy in post-therapeutic cancer patients.

Advances in the Biology, Detection Techniques, and Clinical Applications of Circulating Tumor Cells

Circulating tumor cells (CTCs) play a crucial role in tumor recurrence and metastasis, and their early detection has shown remarkable benefits in clinical theranostics. However, CTCs are extremely rare, thus detecting them in the blood is very challenging. New CTC detection techniques are continuously being developed, enabling deeper analysis of CTC biology and potential clinical application. This article reviews current CTC detection techniques and their clinical application. CTCs have provided, and will continue to provide, important insights into the process of metastasis, which could lead to development of new therapies for different cancers.

The Discovery of Novel Circulating Cancer-Related Cells in Circulation Poses New Challenges to Microfluidic Devices for Enrichment and Detection

Circulating tumor cells (CTCs) enumeration has been widely used as a surrogate predictive marker for early diagnoses, the evaluation of chemotherapy efficacy, and cancer prognosis. Microfluidic technologies for CTCs enrichment and detection have been developed and commercialized as automation platforms. Currently, in addition to CTCs, some new types of circulating cancer-related cells (e.g., CCSCs, CTECs, CAMLs, and heterotypic CTC clusters) in circulation are also reported to be correlated to cancer diagnosis, metastasis, or prognosis. And they widely differ from the conventional CTCs in positive markers, cellular morphology, or size, which presents a new technological challenge to microfluidic devices that use affinity-based capture methods or size-based filtration methods for CTCs detection. This review focuses on the biological and physical properties as well as clinical significance of the novel circulating cancer-related cells, and discusses the challenges of their discovery to microfluidic chip for enrichment. Finally, the current challenges of CTCs detection in clinical application and future opportunities are also discussed.

Comprehensive Atlas of Circulating Rare Cells Detected by SE-iFISH and Image Scanning Platform in Patients With Various Diseases

Objective

Circulating rare cells (CRCs) are known as a crucial nucleated cellular response to pathological conditions, yet the landscape of cell types across a wide variety of diseases lacks comprehensive understanding. This study aimed at detecting and presenting a full spectrum of highly heterogeneous CRCs in clinical practice and further explored the characterization of CRC subtypes in distinct biomarker combinations and aneuploid chromosomes among various disease groups.

Methods

Peripheral blood was obtained from 2,360 patients with different cancers and non-neoplastic diseases. CRC capture and identification were accomplished using a novel platform integrating subtraction enrichment and immunostaining-fluorescence in situ hybridization (SE-iFISH) strategy with a high-throughput automated image scanning system, on which hemocyte, tumor, epithelial, endothelial, mesenchymal, and stemness biomarkers were immunostained and displayed simultaneously. Double chromosome enumeration probe (CEP8 and CEP12) co-detection was performed on isolated CRCs from an extended trial for two chromosome ploidy patterns.

Results

A comprehensive atlas categorizing the diverse CRCs into 71 subtypes outlining was mapped out. The presence of epithelial-mesenchymal transition (EMT) or endothelial-mesenchymal transition (EndoMT), the cells with progenitor property, hematologic CRCs expressing multiple biomarkers, CRCs at "naked nuclei" status, and the rarely reported aneuploid mesenchymal epithelial-endothelial fusion cluster were described. Circulating tumor cells (CTCs) were detected in 2,157 (91.4%) patients; the total numbers of CTCs and circulating tumor-derived endothelial cells (CTECs) were relatively higher in several digestive system cancer types and non-neoplastic infectious diseases (p < 0.05). Co-detection combining CEP8 and CEP12 showed a higher diagnostic specificity on account of 57.27% false negativity of CRC detection through a single probe of CEP8.

Conclusions

The alternative biomarkers and chromosomes to be targeted by SE-iFISH and the image scanning platform, along with the comprehensive atlas, offer insight into the heterogeneity of CRCs and reveal potential contributions to specific disease diagnosis and therapeutic target cell discovery.

Clinical Application of Circulating Tumor Cells and Circulating Endothelial Cells in Predicting Bladder Cancer Prognosis and Neoadjuvant Chemosensitivity

Purpose

To investigate the role of circulating rare cells (CRCs), namely, circulating tumor cells (CTCs) and circulating endothelial cells (CECs), in aiding early intervention, treatment decision, and prognostication in bladder cancer.

Methods

A total of 196 patients with pathologically confirmed bladder cancer, namely, 141 non-muscle invasive bladder cancer (NMIBC) and 55 muscle invasive bladder cancer (MIBC) patients. There were 32 patients who received cisplatin-based neoadjuvant chemotherapy (NAC) followed by radical cystectomy (RC). Subtraction enrichment combined with immunostaining-fluorescence in situ hybridization (SE-iFISH) strategy was used for CTC/CEC detection. Kaplan–Meier analysis and Cox regression were used to evaluate the overall survival (OS) and recurrence-free survival (RFS). Receiver operator characteristic analysis was used to discriminate NAC sensitivity.

Results

CTCs and CECs were related to clinicopathological characteristics. Triploid CTCs, tetraploid CTCs, and total CECs were found to be higher in incipient patients than in relapse patients (P = 0.036, P = 0.019, and P = 0.025, respectively). The number of total CECs and large cell CECs was also associated with advanced tumor stage (P = 0.028 and P = 0.033) and grade (P = 0.028 and P = 0.041). Remarkably, tumor-biomarker-positive CTCs were associated with worse OS and RFS (P = 0.026 and P = 0.038) in NMIBC patients underwent TURBT. CECs cluster was an independent predictor of recurrence in non-high-risk NMIBC patients underwent TURBT (HR = 9.21, P = 0.040). For NAC analysis, pre-NAC tetraploid CTCs and small cell CTCs demonstrated the capability in discriminating NAC-sensitive from insensitive patients. Additionally, tetraploid CTCs and single CTCs elevated post-NAC would indicate chemoresistance.

Conclusion

CTCs and CECs may putatively guide in diagnosis, prognosis prediction, and therapeutic decision-making for bladder cancer.

Liquid biopsy to identify biomarkers for immunotherapy in hepatocellular carcinoma

The past years have witnessed the vigorous development of immunotherapy, mainly immune checkpoint inhibitors (ICIs) targeting the programmed cell death-1 (PD-1) protein and its ligand, PD-L1, and cytotoxic T-lymphocyte-associated antigen-4 (CTLA-4). Indeed, ICIs have largely revolutionized the management and improved the prognosis of patients with intermediate and advanced hepatocellular carcinoma (HCC). However, biomarker-based stratification of HCC patients for optimal response to ICI treatment is still of unmet need and again, there exists the necessity to dynamically monitor treatment effect in real-time manner. The role of conventional biomarkers in immunotherapy surveillance is largely limited by spatial and temporal tumor heterogeneity whereas liquid biopsy seems to be promising to circumvent tumor heterogeneity to identify candidate patients who may response to immunotherapy, to dynamically monitor treatment effect and to unveil resistance mechanism. Herein, we provide a thorough review about the potential utility of liquid biopsy in immunotherapy for HCC and discuss its future perspectives.

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.

Detection of circulating rare cells benefitted the diagnosis of malignant solitary pulmonary nodules

INTRODUCTION

Solitary pulmonary nodules (SPNs) are challenging in differentiating between benignancy and malignancy. Therefore, more effective non-invasive biomarkers are urgently needed. The purpose of this investigation was to examine whether circulating rare cells (CRCs) could facilitate the differentiation between benign and malignant SPNs as well as its sensitivity and specificity.

METHODS

164 patients diagnosed with SPNs, 24 healthy volunteers, and 25 patients diagnosed with advanced-stage lung cancer were included. CT/PET-CT images, serum tumor markers, and biopsy results were collected. The CRCs were examined using subtraction enrichment and immunostaining-fluorescence in situ hybridization (SE-iFISH) and their relationship with malignant or benign SPNs was analyzed.

RESULTS

The total CRC numbers from patients with malignant SPNs diagnosed by biopsy were significantly greater compared to those with benign SPNs (P < 0.0001), but not significantly different from patients with advanced lung cancer (P > 0.05). The total CRCs, with a cut-off value of 21.5 units, showed 67.6% sensitivity and 73.3% specificity [area under curve (AUC) 95% CI, 0.778 (0.666-0.889)] in discriminating benign and malignant SPNs and the triploid CRCs exhibited a high positive likelihood ratio of 8.4, which suggested that CRCs appeared to have a distinct advantage in discriminating benign and malignant SPNs compared to CT/PET-CT images and serum tumor markers and could be a potential screening indicator for lung cancer in the high-risk population.

CONCLUSIONS

SE-iFISH could effectively detect CRCs including circulating tumor cells (CTCs) and circulating tumor-derived endothelial cells (CTECs) and the detection of CRCs could benefit the differentiation of patients with benign and malignant SPNs.

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).

Identification and Comprehensive Co-Detection of Necrotic and Viable Aneuploid Cancer Cells in Peripheral Blood

Aneuploid circulating tumor cells (CTCs, CD31-) and circulating tumor endothelial cells (CTECs, CD31+) exhibit an active interplay in peripheral blood, and play an essential role in tumorigenesis, neoangiogenesis, disease progression, therapy-resistant minimal residual disease (MRD), cancer metastasis and relapse. Currently, most CTC detection techniques are restricted to the indistinguishable quantification of circulating rare cells, including both necrotic and viable cells in cancer patients. Clinically imperative demands to distinguish and detect live and/or dead non-hematological aneuploid cancer cells in peripheral blood, which will assist in the rapid evaluation of therapeutic effects, real-time monitoring of treatment resistance longitudinally developed along with therapy and the effective detection of post-therapeutic MRD, have not yet been achieved. The integrated subtraction enrichment and immunostaining-fluorescence in situ hybridization (SE-iFISH)-derived novel strategy was developed in this study, aiming to precisely identify and detect live and necrotic cancer cells (NC) enriched from carcinoma patients' biofluids. The innovative SE-iFISH (NC) provides a meaningful and practical approach to co-detect various viable and necrotic aneuploid CTCs and CTECs. The detected circulating rare cells can be characterized and categorized into diverse subtypes based upon cell viability, morphology, multiple tumor markers' expression, and the degree of aneuploidy relevant to both malignancy and therapeutic resistance. Each subtype of live or necrotic CTCs and CTECs possesses distinct utility in anti-cancer drug development, translational research, and clinical practice.

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.

Fibrinogen-like protein 1 (FGL1): the next immune checkpoint target

Immune checkpoint therapy has achieved significant efficacy by blocking inhibitory pathways to release the function of T lymphocytes. In the clinic, anti-programmed cell death protein 1/programmed cell death ligand 1 (PD-1/PD-L1) monoclonal antibodies (mAbs) have progressed to first-line monotherapies in certain tumor types. However, the efficacy of anti-PD-1/PD-L1 mAbs is still limited due to toxic side effects and de novo or adaptive resistance. Moreover, other immune checkpoint target and biomarkers for therapeutic response prediction are still lacking; as a biomarker, the PD-L1 (CD274, B7-H1) expression level is not as accurate as required. Hence, it is necessary to seek more representative predictive molecules and potential target molecules for immune checkpoint therapy. Fibrinogen-like protein 1 (FGL1) is a proliferation- and metabolism-related protein secreted by the liver. Multiple studies have confirmed that FGL1 is a newly emerging checkpoint ligand of lymphocyte activation gene 3 (LAG3), emphasizing the potential of targeting FGL1/LAG3 as the next generation of immune checkpoint therapy. In this review, we summarize the substantial regulation mechanisms of FGL1 in physiological and pathological conditions, especially tumor epithelial to mesenchymal transition, immune escape and immune checkpoint blockade resistance, to provide insights for targeting FGL1 in cancer treatment.

Role of aneuploid circulating tumor cells and CD31+ circulating tumor endothelial cells in predicting and monitoring anti-angiogenic therapy efficacy in advanced NSCLC

Prognosticating the efficacy of anti‐angiogenic therapy through longitudinal monitoring and early detection of treatment resistance in cancer patients remain highly challenging. In this study, co‐detection and comprehensive phenotypic and karyotypic molecular characterization of aneuploid circulating tumor cells (CTCs) and circulating tumor endothelial cells (CTECs) were conducted on non‐small cell lung cancer (NSCLC) patients receiving bevacizumab plus chemotherapy. Prognostic values of the cell‐based significant univariate risk factors identified by Cox regression analyses were progressively investigated. Subjects showing an increase in total post‐therapeutic platelet endothelial cell adhesion molecule‐1 (CD31)^– CTCs and CD31⁺ CTECs exhibited a significantly reduced median progression‐free survival (mPFS) and overall survival. Further stratification analyses indicated that pretherapeutic patients bearing vimentin (Vim)⁺ CTECs (mesenchymal M‐type) at baseline revealed a significantly shortened mPFS compared with patients with Vim^– CTECs. Post‐therapeutic patients harboring epithelial cell adhesion molecule (EpCAM)⁺ CTCs and CTECs (epithelial E‐type), regardless of Vim expression or not, showed a significantly reduced mPFS. Post‐therapeutic patients possessing de novo EpCAM⁺/Vim⁺ (hybrid E/M‐type) CTECs displayed the shortest mPFS. Patients harboring either pre‐ or post‐therapeutic EpCAM^–/Vim^– null CTECs (N‐type) exhibited a better response to therapy compared to patients harboring EpCAM⁺ and/or Vim⁺ CTECs. The presented results support the notion that baseline Vim⁺ CTECs and post‐therapeutic EpCAM⁺ CTCs and CTECs are predictive biomarkers for longitudinal monitoring of response to anti‐angiogenesis combination regimens in NSCLC patients.

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.

Circulating tumor cells (CTCs)/circulating tumor endothelial cells (CTECs) and their subtypes in small cell lung cancer: Predictors for response and prognosis

Background

The aim of the study was to define the clinical significance of circulating tumor cells (CTCs)/circulating tumor endothelial cells (CTECs) and their subtypes in small cell lung cancer (SCLC) patients.

Methods

CTCs/CTECs and their subtypes were determined using SE‐iFISH technology in 33 SCLC patients before initial treatment (B1), after two cycles of chemotherapy (B2), at the completion of chemotherapy (B3), and disease progression (B4). The correlations with clinical characteristics, progression‐free survival (PFS), and overall survival (OS) were analyzed.

Results

CTCs and CTECs were detected in 96.6% and 65.5% of patients, respectively. Patients had higher levels of CTCs compared with CTECs in circulation (p < 0.05). Extensive‐stage SCLC patients tended to have higher CTEC counts (p = 0.035), and the detection of CTC‐white blood cell (CTC‐WBC) clusters was associated with a worse response to treatment (p = 0.030). Patients with CTC‐WBC clusters at B1 (17.3 vs. 22.6 months, p = 0.041) and B2 (19.9 vs. 25.2 months, p = 0.018) had significantly shorter OS than those with no detection. Additionally, their presence was revealed as independent predictors for a worse OS in multivariable analyses (B1: HR 9.3, 95% CI: 1.4–48, p = 0.0079; B2: HR 4.4, 95% CI: 1.1–18, p = 0.041). A high CTC level at B4 was an adverse prognostic factor for SCLC patients (PFS: 8.7 vs. 22.5 months, p = 0.0026; OS: 19 months vs. not reached, p = 0.0086). CTC clusters and CTECs also showed prognostic values.

Conclusions

The presence of CTC‐WBC clusters at baseline and after two‐cycle chemotherapy and the total CTC counts at the completion of chemotherapy are strong predictors for the prognostic survival of SCLC patients receiving first‐line treatment.

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.

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.

Soluble Programmed Death Ligand-1 (sPD-L1): A Pool of Circulating Proteins Implicated in Health and Diseases

Upon T-cell receptor stimulation, the Programmed cell Death-1 receptor (PD-1) expressed on T-cells can interact with its ligand PD-L1 expressed at the surface of cancer cells or antigen-presenting cells. Monoclonal antibodies targeting PD-1 or PD-L1 are routinely used for the treatment of cancers, but their clinical efficacy varies largely across the variety of tumor types. A part of the variability is linked to the existence of several forms of PD-L1, either expressed on the plasma membrane (mPD-L1), at the surface of secreted cellular exosomes (exoPD-L1), in cell nuclei (nPD-L1), or as a circulating, soluble protein (sPD-L1). Here, we have reviewed the different origins and roles of sPD-L1 in humans to highlight the biochemical and functional heterogeneity of the soluble protein. sPD-L1 isoforms can be generated essentially by two non-exclusive processes: (i) proteolysis of m/exoPD-L1 by metalloproteases, such as metalloproteinases (MMP) and A disintegrin and metalloproteases (ADAM), which are capable of shedding membrane PD-L1 to release an active soluble form, and (ii) the alternative splicing of PD-L1 pre-mRNA, leading in some cases to the release of sPD-L1 protein isoforms lacking the transmembrane domain. The expression and secretion of sPD-L1 have been observed in a large variety of pathologies, well beyond cancer, notably in different pulmonary diseases, chronic inflammatory and autoimmune disorders, and viral diseases. The expression and role of sPD-L1 during pregnancy are also evoked. The structural heterogeneity of sPD-L1 proteins, and associated functional/cellular plurality, should be kept in mind when considering sPD-L1 as a biomarker or as a drug target. The membrane, exosomal and soluble forms of PD-L1 are all integral parts of the highly dynamic PD-1/PD-L1 signaling pathway, essential for immune-tolerance or immune-escape.

Dysregulated KRAS gene-signaling axis and abnormal chromatin remodeling drive therapeutic resistance in heterogeneous-sized circulating tumor cells in gastric cancer patients

The mechanism by which heterogeneous-sized circulating tumor cells (CTCs) in gastric cancer (GC) patients are resistant to the targeted therapy and/or chemotherapy remains unclear. This study investigated prognostic value and genomic variations of size-heterogenous CTCs, in an attempt to unravel the molecular mechanisms underlying the therapeutic resistance, which is relevant to poor prognosis in GC. Aneuploid CTCs, detected in 111 advanced GC patients, were categorized into small (≤white blood cell [WBC], 25.54%) and large (>WBC, 74.46%) cells. Pre-treatment patients possessing ≥3 baseline small CTCs with trisomy 8 (_SCTCs^tri) or ≥6 large multiploid CTCs (_LCTCs^multi) showed an inferior median progression-free survival. Moreover, the cut-off value of ≥6 _LCTCs^multi was also an effective prognosticator for poor median overall survival. Single cell-based DNA sequencing of 50 targeted CTCs indicated that _SCTCs^tri and _LCTCs^multi harbored distinct gene variations respectively. Mutations in the KRAS and Rap1 pathway were remarkably abundant in _SCTCs^tri, whereas several unique mutations in the MET/PI3K/AKT pathway and SMARCB1 gene were identified in _LCTCs^multi. Obtained results suggested that _SCTCs^tri and _LCTCs^multi exhibited different mechanisms to therapy resistance and correlated with patients' poor outcome.

CD44+ Circulating Tumor Endothelial Cells Indicate Poor Prognosis in Pancreatic Ductal Adenocarcinoma After Radical Surgery: A Pilot Study

Background

Circulating tumor endothelial cells (CTECs) are cells that originate from tumor endothelial cells (TECs) of blood vessels and are shed into peripheral blood. Some studies have shown that CTECs are associated with tumor angiogenesis, growth and indicate prognosis in patients with malignant solid tumor. However, the role of CTECs especially the phenotype of CTECs in pancreatic adenocarcinoma (PDAC) is still not clear. We investigated the relationship between CTECs and patients’ prognosis.

Methods

A total of 73 patients with resectable PDAC were enrolled in our research and underwent radical surgery. Peripheral venous blood samples were collected before surgery, on postoperative day (POD) 7 and on postoperative month (POM) 1, respectively. We used integrated subtraction enrichment and immunostaining-fluorescence in situ hybridization (SE-iFISH) platform to identify and enumerate CTECs. Immunofluorescence was used to identify CTECs expressing CD44 and vimentin.

Results

In patients with early tumor recurrence (DFS< 6 months), the preoperative CD44+ CTEC levels showed significantly higher (P = 0.023). Univariate and multivariate analysis showed that history of diabetes [HR 2.656 (1.194–5.908), P = 0.017], numbers of positive lymph nodes [HR 1.871 (1.388–2.522), P < 0.001], preoperative numbers of CD44+ CTECs [HR 1.216 (1.064–1.390), P = 0.004], and POM1 CA19-9 level [HR 1.002 (1.001–1.002), P < 0.001] were independent prognostic factors for DFS.

Conclusion

The detection of CD44+CTECs in patients with resectable PDAC preoperatively could be an independent predictor of shorter DFS after radical surgery.

Predictive biomarkers of anti-PD-1/PD-L1 therapy in NSCLC

Immunotherapy, especially anti-programmed cell death protein 1/programmed cell death ligand 1 (PD-1/PD-L1) treatment has significantly improved the survival of non-small cell lung cancer (NSCLC) patients. However, the overall response rate remains unsatisfactory. Many factors affect the outcome of anti-PD-1/PD-L1 treatment, such as PD-L1 expression level, tumor-infiltrating lymphocytes (TILs), tumor mutation burden (TMB), neoantigens, and driver gene mutations. Further exploration of biomarkers would be favorable for the best selection of patients and precisely predict the efficacy of anti-PD-1/PD-L1 treatment. In this review, we summarized the latest advances in this field, and discussed the potential applications of these laboratory findings in the clinic.

Therapeutic Approaches for Metastases from Colorectal Cancer and Pancreatic Ductal Carcinoma

Metastasis is the process of dissemination of a tumor, whereby cells from the primary site dislodge and find their way to other tissues where secondary tumors establish. Metastasis is the primary cause of death related to cancer. This process warrants changes in original tumoral cells and their microenvironment to establish a metastatic niche. Traditionally, cancer therapy has focused on metastasis prevention by systematic treatments or direct surgical re-sectioning. However, metastasis can still occur. More recently, new therapies direct their attention to targeting cancer stem cells. As they propose, these cells could be the orchestrators of the metastatic niche. In this review, we describe conventional and novel developments in cancer therapeutics for liver and lung metastasis. We further discuss the resistance mechanisms of targeted therapy, the advantages, and disadvantages of diverse treatment approaches, and future novel strategies to enhance cancer prognosis.

Combined detection and subclass characteristics analysis of CTCs and CTECs by SE-iFISH in ovarian cancer

Objective

Hematogenous metastasis is essential for the progression of ovarian cancer (OC), and circulating tumor cells (CTCs) are part of the metastatic cascade. However, the detection rate of CTC is low due to the use of less sensitive detection methods. Therefore, this study aimed to detect CTCs and circulating tumorigenic endothelial cells (CTECs) in patients with OC using subtraction enrichment and immunostaining and fluorescence in situ hybridization (SE-iFISH).

Methods

We enrolled a total of 56 subjects, including 20 OC patients and 36 ovarian benign tumor patients. CTCs and CTECs were captured by subtraction enrichment (SE) and counted and classified according to immunofluorescence staining of tumor markers (TMs) carbohydrate antigen 125 (CA125) and human epididymis protein 4 (HE4) combined with fluorescence in situ hybridization (iFISH) of chromosome 8 (Chr8) aneuploidy. The diagnostic value and subtype characteristics of CTCs and CTECs were investigated.

Results

The detection rate of CTCs by SE-iFISH was high. Compared with CA125 and HE4, Chr8 aneuploidy was the major identification feature of CTC. CTC counts in OC were statistically higher than those in benign groups. CTC and CTEC with ≥pentaploidy were detected in both groups, illustrating the poor diagnostic value of CTC or CTEC. Distributions of triploid and tetraploid CTC subtypes were significantly different, and combined detection of triploid and tetraploid CTCs showed the best diagnostic value. In contrast, the distribution of CTECs in the OC and benign groups had no statistically significant difference. Small CTCs accounted for over 1/3 of the total CTC count. We also found that small CTCs and CTECs primarily comprised triploid cells, while large CTCs and CTECs mainly comprised pentaploidy and beyond.

Conclusions

The application of SE-iFISH offered a more comprehensive understanding of heterogeneous CTCs and CTECs in OC. Analysis of subclass characteristics of the CTCs and CTECs according to Chr8 aneuploidy and cell size may broaden their potential clinical utility and deepen mechanistic studies in OC.

Multifaceted modifications for a cell size-based circulating tumor cell scope technique hold the prospect for large-scale application in general populations

Circulating tumor cells (CTCs) indicate the diagnosis and prognosis of cancer patients, together with benefiting individual treatment and anticancer drug development. However, their large-scale application in general population still requires systematically multifaceted modifications for currently proprietary new technologies based on filtration. We primitively utilized a cell size-based platform to evaluate the recovery efficiency of spiked abnormal cell lines and analyzed circulating abnormal cells (CACs). To dissect the subpopulations of CACs, we conducted immunofluorescent (IF) staining with a combination of unique biomarkers of CTCs and circulating endothelial cells (CECs). Furthermore, we improved the CTC screening system by assessing the feasibility of transferring CTCs for automatic IF analysis, together with simulating and optimizing the circumstances for long-term CTC storage and transportation. We detected CACs in 15 HD candidates with CTC characteristics such as abnormally large cytomorphology, high nuclear-cytoplasmic ratio, and positive for panCK or VIM staining. Thereafter, we improved accuracy of the platform by distinguishing CTCs from CECs, which satisfied the elementary requirement for small-scale CTC screening in HD candidates. Finally, large-scale CTC screening in general population was available after multifaceted modifications including automatic analysis by transferring CTCs on slides, choosing the appropriate blood-collecting tube, optimizing the conditions for long-term CTC storage and transportation, and evaluating the potential effect on the CTC phenotype. Hence, we systematically modified the scope of technique parameters, improved the accuracy of early cancer detection, and made it realizable for large-scale CTC or CEC screening in general population.

Circulating Tumour Cell Expression of Immune Markers as Prognostic and Therapeutic Biomarkers in Head and Neck Squamous Cell Carcinoma: A Systematic Review and Meta-Analysis

Rates of loco-regional recurrence and distant metastasis remain high among head and neck squamous cell carcinoma (HNSCC) patients, despite advancing cancer treatment modalities and therapeutic agents. One area that has generated considerable interest is the immune landscape of the tumour, heralding a wave of immune checkpoint inhibitors with notable efficacy in recurrent/metastatic HNSCC patients. However, HNSCC remains poorly served by biomarkers that can direct treatment in a personalised fashion to target the tumour heterogeneity seen between patients. Detection and analysis of circulating tumour cells (CTCs) in HNSCC has provided a previously unseen view of the metastasis forming cells that are potentially contributing to poor clinical outcomes. In particular, identifying CTC expression of phenotypic and druggable protein markers has allowed CTC sub-populations to be defined that hold prognostic value or are potential therapeutic targets themselves. The aim of this systematic review was to examine the role of CTC immune-marker expression as prognostic/therapeutic biomarkers in HNSCC by evaluating progress to date and discussing areas for future research. Our results highlight how few studies have been able to demonstrate prognostic significance of immune-marker expression in CTCs. As expected, the immune checkpoint PD-L1 was the most widely investigated marker. However, no studies evaluated CTC target immune marker expression in immunotherapy cohorts. Despite these findings, the data presented demonstrate promise that CTCs may be a source of future biomarkers for immunotherapy and will provide valuable information regarding the potential immune evasion of these metastasis forming cells.

Hepatocellular Carcinoma-Circulating Tumor Cells Expressing PD-L1 Are Prognostic and Potentially Associated With Response to Checkpoint Inhibitors

Hepatocellular carcinoma (HCC) is a leading cause of mortality. Checkpoint inhibitors of programmed cell death protein-1 (PD-1) and programmed death-ligand 1 (PD-L1) have shown great efficacy, but lack biomarkers that predict response. Circulating tumor cells (CTCs) have promise as a liquid-biopsy biomarker; however, data on HCC CTCs expressing PD-L1 have not been reported. We sought to detect PD-L1-expressing HCC-CTCs and investigated their role as a prognostic and predictive biomarker. Using an antibody-based platform, CTCs were enumerated/phenotyped from a prospective cohort of 87 patients with HCC (49 early-stage, 22 locally advanced, and 16 metastatic), 7 patients with cirrhosis, and 8 healthy controls. Immunocytochemistry identified total HCC CTCs (4',6-diamidino-2-phenylindole-positive [DAPI+]/cytokeratin-positive [CK+]/clusters of differentiation 45-negative [CD45-]) and a subpopulation expressing PD-L1 (DAPI+/CK+/PD-L1+/CD45-). PD-L1+ CTCs were identified in 4 of 49 (8.2%) early-stage patients, but 12 of 22 (54.5%) locally advanced and 15 of 16 (93.8%) metastatic patients, accurately discriminating early from locally advanced/metastatic HCC (sensitivity = 71.1%, specificity = 91.8%, area under the receiver operating characteristic curve = 0.807; P < 0.001). Compared to patients without PD-L1+ CTCs, patients with PD-L1+ CTCs had significantly inferior overall survival (OS) (median OS = 14.0 months vs. not reached, hazard ratio [HR] = 4.0, P = 0.001). PD-L1+ CTCs remained an independent predictor of OS (HR = 3.22, P = 0.010) even after controlling for Model for End-Stage Liver Disease score (HR = 1.14, P < 0.001), alpha-fetoprotein (HR = 1.55, P < 0.001), and overall stage/tumor burden (beyond University of California, San Francisco, HR = 7.19, P < 0.001). In the subset of 10 patients with HCC receiving PD-1 blockade, all 5 responders demonstrated PD-L1+ CTCs at baseline, compared with only 1 of 5 nonresponders, all of whom progressed within 4 months of starting treatment. Conclusion: We report a CTC assay for the phenotypic profiling of HCC CTCs expressing PD-L1. PD-L1+ CTCs are predominantly found in advanced-stage HCC, and independently prognosticate OS after controlling for Model for End-Stage Liver Disease, alpha-fetoprotein, and tumor stage. In patients with HCC receiving anti-PD-1 therapy, there was a strong association with the presence of PD-L1+ CTCs and favorable treatment response. Prospective validation in a larger cohort will better define the utility of PD-L1+ CTCs as a prognostic and predictive biomarker in HCC.