Circulating Tumor Cells Clusters Research Articles

Abstract P6-10-23: Presence of circulating tumor cell clusters and elevated platelet counts interactively predict disease progression in advanced-stage breast cancer patients

Abstract Background: Circulating tumor cells (CTCs) and their clusters (CTC-clusters) are promising prognostic markers in breast cancer. Recently studies showed that platelets interact with tumor cells in the circulation and promote metastasis. However, no study has been reported to explore the effects of interactions between CTCs/CTC-clusters and platelets on the prognosis of breast cancer at the population level. Methods: A total of 146 female advanced-stage breast cancer patients were included in this study. CTCs and CTC-clusters were enumerated using the CellSearch system. Platelet count was obtained from laboratory tests. The individual and joint effects of CTCs/CTC-clusters and platelets on progression free survival (PFS) were evaluated using the Cox proportional hazards model. Results: Elevated CTCs (≥ 5 CTCs/7.5 mL), presence of CTC-clusters, or high platelet counts (≥ 400 × 109/L) were individually associated with PFS (hazard ratio [HR] 2.69, 2.71, and 1.79, respectively). We further stratified patients into three risk groups according to the status of CTCs/CTC-clusters in combination with the level of platelet counts, including: 1) low-risk group: for CTC-related analyses, low CTCs (< 5 CTCs/7.5 mL) and platelet counts (< 400 × 109/L); for CTC-cluster-related analyses, absence of CTC-cluster and low platelet counts; 2) medium-risk group: for CTC-related analyses, either elevated CTCs (≥ 5 CTCs/7.5 mL) or high platelet counts (≥ 400 × 109/L), but not both; for CTC-cluster-related analyses, either presence of CTC-clusters or high platelet counts, but not both; 3) high-risk group: for CTC-related analyses, both elevated CTCs and high platelet counts; for CTC-cluster-related analyses, presence of CTC-clusters and high platelet counts. A significantly increased risk for disease progression was observed in high-risk patients, especially in patients with both CTC-clusters and high platelet counts (adjusted HR 16.06, P = 0.0003, log-rank P< 0.0001). Furthermore, we identified a multiplicative interaction between CTC-clusters and platelets on PFS (P for interaction = 0.0483), and the patients with both CTC-clusters and high platelet counts had the shortest time of development of new metastatic sites. Conclusions: Our results indicated the effects of interactions between the presence of CTC-clusters and high platelet counts on tumor progression and dissemination in breast cancer. Future studies are warranted to validate our findings and explore their biological mechanisms and clinical relevance. Citation Format: Chun Wang, Zhong Ye, Zhenchao Zhang, Maysa Abu-Khalaf, Daniel Silver, AnaMaria Lopez, Frederick Fellin, Saveri Bhattacharya, Rebecca Jaslow, Kaelan Yao, Darayus Toorkey, Neha Pancholy, Ronald Myers, Hushan Yang. Presence of circulating tumor cell clusters and elevated platelet counts interactively predict disease progression in advanced-stage breast cancer patients [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P6-10-23.

Cluster circulating tumor cells in surgical cases of lung cancer.

A cancer lesion sheds tumor cells into the circulating blood as circulating tumor cells (CTCs). Since cluster CTCs have been considered as precursor lesions of metastasis, their clinical implication was investigated in this study according to the preoperative status of cluster CTC detection in surgical cases of clinically early-stage lung cancer. Among 104 surgical patients of early-stage lung cancer, CTCs were extracted from the peripheral blood before surgery using a micro-pore size selection method (ScreenCell®) and diagnosed microscopically. Implications of detecting cluster CTC were assessed according to the prognosis and clinicopathological characteristics. The status of CTC detection was not detected in 77 cases (74.0%), single CTC only detection in 7 cases (6.7%), and cluster CTC detected in 20 cases (19.2%). Patients with cluster CTCs exhibited significantly lower recurrence-free survival and overall survival than did patients of other groups. In addition, in hazard ratio analysis, the hazard ratios were independent of other predictors of poor prognosis, and detection of cluster CTCs was associated with predictors of poor prognosis. Cluster CTCs were detected in cases where the original lung cancer lesion had clinical predictors of poor prognosis and were independent negative predictors of survival.

Circulating Tumor Cells as a Biomarker to Assist Molecular Diagnosis for Early Stage Non-Small Cell Lung Cancer.

Background and ObjectiveCompared with tissue biopsy, liquid biopsy is the most preferable non-invasive promising method in personalized medicine, although it has many limitations in isolating circulating tumor cells (CTC). Lung cancer associated mortality is drastically increased due to a shortfall of early-stage detection, which remains a challenge. Herein, we aimed to detect lung cancer at an early-stage using CellCollector device.Methods39,627 volunteers underwent low-dose computed tomography; 2508 cases with pulmonary nodules and 7080 with no pulmonary nodules were chosen. After follow-up, 24 patients were diagnosed with early-stage non-small cell lung cancer (NSCLC), and subjected to CTC detection using CellCollector, along with 72 healthy volunteers. Immunofluorescence staining for EpCAM/CKs and CD45 were performed for CTC validation.ResultsFifteen out of twenty-four (stage I, n = 18; stage II, n = 6) early-stage lung cancer patients were found to be CTC-positive, whereas no CTC was found in the control group. Genetic mutation of TP53, ERBB2, PDGFRA, CFS1R and FGFR1 in the CTC revealed 71.6% of the mutation sites similar to the tumor tissues of 13 patients. Molecular characterization revealed higher expression of protein PD-LI in CTC (40%) as compared to tumor tissue (26.7%). Moreover, CTC clusters were detected in 40% of patients.ConclusionCTC detection using the CellCollector in early-stage NSCLC had a relative high capture rate. Moreover, CTC analysis is a prospective setting for molecular diagnostic in cases when tumor tissue biopsy is not desirable.

Circulating ensembles of tumor-associated cells in gastrointestinal cancers.

808 Background: CEA and CA19-9 are non-specific markers for Gastrointestinal (GI) cancers. Molecular analysis of fecal blood is of limited utility in colorectal cancers. A non-invasive pan-GI-cancer blood-based test with high specificity and sensitivity is an unmet medical need. Considering that unprovoked thromboembolism is a significant risk in multiple cancers, we hypothesized that circulating thrombotic emboli in peripheral blood could comprise cancer cells and would serve as a reliable biomarker for detection of GI cancers. Methods: We obtained 15ml of blood from 7481 individuals, including 181 cases of Esophageal cancer, 125 cases of Gastric cancer, 448 cases of colorectal cancer and from 6727 asymptomatic individuals with age related elevated risk who underwent evaluation of serum CA19-9 and AFP. Peripheral blood mononuclear cells (PBMC) were isolated by centrifugation and further processes for negative enrichment and harvesting of circulating tumor cell clusters which were characterized by immunostaining. Circulating Ensembles of Tumor Associated Cells (C-ETACs) were defined as clusters of 3 or more cells which were positive for EpCAM and CK, irrespective of CD45 status. Results: C-ETACs were detected in 86.7% of esophageal cancers, 94.4% of gastric cancers and 91.3% of colorectal cancers respectively irrespective of extent (stage / metastatic status) of disease and prior treatments. Overall sensitivity among 754 cancer patients was 90.7%. Among the asymptomatic individuals, C-ETACs were detected in 31 / 366 (8.5%) individuals with elevated CEA and 10 / 152 (6.2%) individuals with elevated CA19-9. C-ETACs were detected in 160 / 5333 (2.9%) of the asymptomatic individuals who had no abnormal findings in any of the said markers. Conclusions: C-ETACs were ubiquitously detected in cancers of Oesophagus, Stomach and Colorectum regardless of stage and treatment status, and pose significant latent risk of thromboembolism and metastasis/recurrence. The relative undetectability of C-ETACs in the asymptomatic cohort indicates causative connection with malignancies and are suitable for screening for these cancers.

Detection of AXL expression in circulating tumor cells of lung cancer patients using an automated microcavity array system.

Noninvasive diagnostics using circulating tumor cells (CTCs) are expected to be useful for decision making in precision cancer therapy. AXL, a receptor tyrosine kinase is associated with tumor progression, epithelial‐to‐mesenchymal transition (EMT), and drug resistance, and is a potential therapeutic target. However, the epithelial markers generally used for CTC detection may be not enough to detect AXL‐expressing CTCs due to EMT. Here, we evaluated the detection of AXL‐expressing CTCs using the mesenchymal marker vimentin with a microcavity array system. To evaluate the recovery of cancer cells, spike‐in experiments were performed using cell lines with varying cytokeratin (CK) or vimentin (VM) expression levels. With high CK and low VM‐expressing cell lines, PC‐9 and HCC827, the recovery rate of AXL‐expressing cancer cells was 1%‐17% using either CK or VM as markers. Whereas, with low CK and high VM‐expressing cell lines, MDA‐MB231 and H1299, it was 52%‐75% using CK and 72%‐88% using VM as a marker. For clinical evaluation, peripheral blood was collected from 20 non–small cell lung cancer patients and CTCs were detected using CK or VM as markers in parallel. Significantly more AXL‐expressing single CTCs were detected in VM‐positive than CK‐positive CTCs (P < .001). Furthermore, CTC clusters were identified only among VM‐positive CTCs in 20% of patients. Patients with one or more prior treatments harbored significantly more VM‐positive AXL‐expressing CTCs, suggesting the involvement of these CTCs in drug resistance. These results indicate the necessity of integrating mesenchymal markers with CTC detection and this should be further evaluated clinically.

Cancer stemness contributes to cluster formation of colon cancer cells and high metastatic potentials.

The ability of cancer cells to form clusters is a characteristic feature in the development of metastatic tumours with drug resistance. Several studies demonstrated that clusters of circulating tumour cells (CTCs) have a greater metastatic potential to establish new tumours at secondary sites than single CTCs. However, the mechanism of cluster formation is not well understood. In this study, we investigated whether cancer stemness would contribute to cluster formation. We used a tumour sphere culture method to enrich cancer stem cells (CSCs) from colon cancer cells and found that during the second generation of sphere culture, clusters (between 3 and 5 cells) formed within the first 24hours, whereas the rest remained as single cells. The clusters were analysed for stemness and metastatic potential, including gene expressions for cancer stemness (CD133 and Lgr5), epithelial-mesenchymal transition (E-cadherin and TGF-β 1-3) and hypoxia-induced factors (HIF-1α and HIF-2α). The results showed that the clusters expressed higher levels of these genes and colon CSC surface markers (including CD24, CD44 and CD133) than the single cells. Among these markers, CD24 seemed the major contributor linking the cells into the clusters. These clusters also showed a stronger ability to both form colonies and migrate. Our data collectively suggest that colon cancer stemness contributes to cluster formation and that clustered cells exhibit a great metastatic potential. Our study thus provides a method to study the CTC clusters and derive insight into oncogenesis and metastasis.

Identification and Single-Cell Analysis of Viable Circulating Tumor Cells by a Mitochondrion-Specific AIE Bioprobe.

Liquid biopsies of cancer via single‐cell molecular profiling of circulating tumor cells (CTCs) are hampered by the lack of ideal CTC markers. In this study, it is reported that TPN, a bioprobe with aggregation‐induced emission (AIE) activity is capable of distinguishing various tumor cells from blood leukocytes based on the difference in cell mitochondria. TPN is a cell‐permeant live‐cell stain that has little effect on cell viability and integrity, enabling single‐cell DNA/RNA analysis with improved efficiency compared with traditional antibody‐based methods. Using TPN labeling, CTCs and CTC cluster are detected in the blood from patients with lung or liver cancer. The capability of TPN to identify rare tumor cells in the malignant pleural effusion samples is also demonstrated. Furthermore, RNA sequencing of single lung CTC identified by TPN is successfully performed. The findings presented here provide an antibody‐free, low‐cost, and nondisruptive approach for detection and genomic characterization of viable tumor cells based on a mitochondria‐targeting AIE luminogen. It might serve as a new tool for monitoring of genomics dynamic of tumor and unraveling the mechanisms of tumor metastasis.

High-Throughput Label-Free Isolation of Heterogeneous Circulating Tumor Cells and CTC Clusters from Non-Small-Cell Lung Cancer Patients

(1) Background: Circulating tumor cell (CTC) clusters are emerging as clinically significant harbingers of metastases in solid organ cancers. Prior to engaging these CTC clusters in animal models of metastases, it is imperative for technology to identify them with high sensitivity. These clusters often present heterogeneous surface markers and current methods for isolation of clusters may fall short. (2) Methods: We applied an inertial microfluidic Labyrinth device for high-throughput, biomarker-independent, size-based isolation of CTCs/CTC clusters from patients with metastatic non-small-cell lung cancer (NSCLC). (3) Results: Using Labyrinth, CTCs (PanCK+/DAPI+/CD45−) were isolated from patients (n = 25). Heterogeneous CTC populations, including CTCs expressing epithelial (EpCAM), mesenchymal (Vimentin) or both markers were detected. CTCs were isolated from 100% of patients (417 ± 1023 CTCs/mL). EpCAM− CTCs were significantly greater than EpCAM+ CTCs. Cell clusters of ≥2 CTCs were observed in 96% of patients—of which, 75% were EpCAM−. CTCs revealed identical genetic aberrations as the primary tumor for RET, ROS1 , and ALK genes using fluorescence in situ hybridization (FISH) analysis. (4) Conclusions: The Labyrinth device recovered heterogeneous CTCs in 100% and CTC clusters in 96% of patients with metastatic NSCLC. The majority of recovered CTCs/clusters were EpCAM−, suggesting that these would have been missed using traditional antibody-based capture methods.

Relevance of CTC Clusters in Breast Cancer Metastasis.

Metastasis is the major cause of mortality in patients with breast cancer; however, the mechanisms of tumor cell dissemination and metastasis formation are not well established yet. The study of circulating tumour cells (CTCs), the metastatic precursors of distant disease, may help in this search. CTCs can be found in the blood of cancer patients as single cells or as tumor cell aggregates, known as CTC clusters. CTC clusters have differential biological features such as an enhanced survival and metastatic potential, and they hold great promises for the evaluation of prognosis, diagnosis and therapy of the metastatic cancer. The analysis of CTC clusters offers new insights into the mechanism of metastasis and can guide towards the development of new diagnostic and therapeutic strategies to suppress cancer metastasis. This has become possible thanks to the development of improved technologies for detection of CTCs and CTC clusters. However, more efficient methods are needed in order to address important questions regarding the metastatic potential of CTC and future clinical applications. In this chapter, we explore the current knowledge on the role of CTC clusters in breast cancer metastasis, their origin, metastatic advantages and clinical importance.

Liquid Biopsy: Detection of Circulating Tumor Cells in Esophageal Squamous Cell Carcinoma.

Circulating tumor cells (CTC) harvested in the blood of patients with esophageal squamous cell carcinoma (ESCC) are associated with certain clinical pathological parameters as well as patients' prognosis and response to chemoradiation. They are the source of distant metastases and their mechanisms of pathogenesis is complex. In recent years, advance in technologies has allowed scientists to detect, enumerate, and isolate these cells for further analysis and monitor the diseases progression in patients with cancer. There are a few methods available for the identification of individual CTC and clusters of CTCs (circulating tumor microemboli). The most commonly used is detection by immunomagnetic method. Although all these methods have limitations, they are helpful for understanding the pathogenesis of CTCs with potential applications in clinical managements in patients with ESCC.

In-flow measurement of cell-cell adhesion using oscillatory inertial microfluidics.

Multicellular clusters in circulation can exhibit a substantially different function and biomarker significance compared to individual cells. Notably, clusters of circulating tumor cells (CTCs) are much more effective initiators of metastasis than single CTCs, and correlate with worse patient prognoses. Measuring the cell-cell adhesion strength of CTC clusters is a critical step towards understanding their subsistence in the circulation and mechanism of elevated tumorigenicity. However, measuring cell-cell adhesion forces in flow is elusive using existing methods. Here, we report an oscillatory inertial microfluidics system which exerts a repeating fluidic force profile on suspended cell doublets to determine their cell-cell adhesion strength (Fs), without any biophysical modifications to the cell surface and physiological morphology. Using our system, we analyzed a large number (N > 500) of doublets from a patient-derived breast cancer CTC line. We discovered that the cell-cell adhesion strength of CTC doublets varied almost 20-fold between the weakly adhered (Fs < 28 nN) and strongly bound subpopulations (Fs > 542 nN). Our system can be used with other cancer or noncancer cells without restrictions, and may be used for rapid screening of drugs aiming to disrupt the highly-metastatic CTC clusters in circulation.

Circulating tumor cells in hepatocellular carcinoma: single-cell based analysis, preclinical models, and clinical applications.

Circulating tumor cells (CTCs) are shed into the bloodstream from primary tumors and metastatic lesions and provide significant information about tumor progression and metastasis. CTCs contribute to tumor metastasis through the epithelial-to-mesenchymal transition (EMT). CTC clusters and stem-like phenotypes lead to a more aggressive and metastatic potential. CTCs retain the heterogeneity and imitate the nature of corresponding primary tumors. Therefore, it is important to use single-cell based analysis to obtain information on tumor heterogeneity and biology. CTCs are also good candidates for building preclinical models (especially 3D organoid cultures) for drug screening, disease modeling, genome editing, tumor immunity research, and organ-like biobank establishment. In this article, we summarize the current CTC capture technology, dissect the phenotypes associated with CTC metastasis, and review the progress in single-cell based analysis and preclinical modeling of the pattern and kinetics of CTCs. In particular, we discuss the use of CTCs to assess the progression of hepatocellular carcinoma (HCC).

Microfluidic concentration and separation of circulating tumor cell clusters from large blood volumes.

Circulating tumor cells (CTCs) are extremely rare in the blood, yet they account for metastasis. Notably, it was reported that CTC clusters (CTCCs) can be 50-100 times more metastatic than single CTCs, making them particularly salient as a liquid biopsy target. Yet they can split apart and are even rarer, complicating their recovery. Isolation by filtration risks loss when clusters squeeze through filter pores over time, and release of captured clusters can be difficult. Deterministic lateral displacement is continuous but requires channels not much larger than clusters, leading to clogging. Spiral inertial focusing requires large blood dilution factors (or lysis). Here, we report a microfluidic chip that continuously isolates untouched CTC clusters from large volumes of minimally (or undiluted) whole blood. An array of 100 μm-wide channels first concentrates clusters in the blood, and then a similar array transfers them into a small volume of buffer. The microscope-slide-sized PDMS device isolates individually-spiked CTC clusters from >30 mL per hour of whole blood with 80% efficiency into enumeration (fluorescence imaging), and on-chip yield approaches 100% (high speed video). Median blood cell removal (in base-10 logs) is 4.2 for leukocytes, 5.5 for red blood cells, and 4.9 for platelets, leaving less than 0.01% of leukocytes alongside CTC clusters in the product. We also demonstrate that cluster configurations are preserved. Gentle, high throughput concentration and separation of circulating tumor cell clusters from large blood volumes will enable cluster-specific diagnostics and speed the generation of patient-specific CTC cluster lines.

Association of a novel circulating tumor DNA next-generating sequencing platform with circulating tumor cells (CTCs) and CTC clusters in metastatic breast cancer

PurposeLiquid biopsies, including circulating tumor DNA (ctDNA) and circulating tumor cells (CTCs), can be used to understand disease prognosis, tumor heterogeneity, and dynamic response to treatment in metastatic breast cancer (MBC). We explored a novel, 180-gene ctDNA panel and the association of this platform with CTCs and CTC clusters.MethodsA total of 40 samples from 22 patients with MBC were included in the study. For the primary analysis, all patients had ctDNA sequencing using the PredicinePLUS™ platform. CTCs and CTC clusters were examined using the CellSearch™ System. Clinical and pathological variables were reported using descriptive analyses. Associations between CTC count and specific genomic alterations were tested using the Mann-Whitney U test.ResultsOf 43 sequenced patients, 40 (93%) had at least one detectable genomic alteration with a median of 6 (range 1–22). Fifty-seven different genes were altered, and the landscape of genomic alterations was representative of MBC, including the commonly encountered alterations TP53, PTEN, PIK3CA, ATM, BRCA1, CCND1, ESR1, and MYC. In patients with predominantly hormone-receptor-positive MBC, the number of CTCs was significantly associated with alterations in ESR1 (P < 0.005), GATA3 (P < 0.05), CDH1 (P < 0.0005), and CCND1 (P < 0.05) (Mann-Whitney U test). Thirty-six percent of patients had CTC clusters, which were associated with alterations in CDH1, CCND1, and BRCA1 (all P < 0.05, Mann-Whitney U test). In an independent validation cohort, CTC enumeration confirmed significant associations with ESR1 and GATA3, while CTC clusters were significantly associated with CDH1.ConclusionsWe report on a novel ctDNA platform that detected genomic alterations in the vast majority of tested patients, further indicating potential clinical utility for capturing disease heterogeneity and for disease monitoring. Detection of CTCs and CTC clusters was associated with particular genomic profiles.

Hydrodynamic stress stimulates growth of cell clusters via the ANXA1/PI3K/AKT axis in colorectal cancer

Cancer cells are exposed to various stresses in vivo, including hydrodynamic stress (HDS). HDS on cancer cells in the blood stream can influence the metastatic potential. Recent studies revealed that circulating tumor cell clusters are more responsible for metastasis than circulating single cells. Nevertheless, most studies on HDS are based on single cells prepared from established cancer cell lines. Here, we used cancer tissue-originated spheroids (CTOS) as a patient-derived, 3D organoid model to investigate the effect of HDS on cancer cell clusters. We found that HDS induced the growth of cancer cell clusters in a population of colorectal CTOSs. Microarray analyses revealed that the multifunctional protein, Annexin 1 (ANXA1), was upregulated upon HDS exposure. Chemically-induced membrane damage also triggered the expression of ANXA1. A knockdown of ANXA1 revealed that ANXA1 regulated HDS-stimulated growth in colorectal CTOSs. Mechanistically, activating the PI3K/AKT pathway downstream of ANXA1 contributed to the phenotype. These findings demonstrate that HDS induces the growth of cancer cell clusters via ANXA1/PI3K/AKT axis, which helps to elucidate the pro-metastatic feature of circulating cancer cell clusters.

A Biophysical Model Uncovers the Size Distribution of Migrating Cell Clusters across Cancer Types.

Migration from the primary tumor is a crucial step in the metastatic cascade. Cells with various degrees of adhesion and motility migrate and are launched into the bloodstream as single circulating tumor cells (CTC) or multicellular CTC clusters. The frequency and size distributions of these clusters have been recently measured, but the underlying mechanisms enabling these different modes of migration remain poorly understood. We present a biophysical model that couples the phenotypic plasticity enabled by the epithelial-mesenchymal transition (EMT) and cell migration to explain the modes of individual and collective cancer cell migration. This reduced physical model captures how cells undergo a transition from individual migration to collective cell migration and robustly recapitulates CTC cluster fractions and size distributions observed experimentally across several cancer types, thus suggesting the existence of common features in the mechanisms underlying cancer cell migration. Furthermore, we identify mechanisms that can maximize the fraction of CTC clusters in circulation. First, mechanisms that prevent a complete EMT and instead increase the population of hybrid epithelial/mesenchymal (E/M) cells are required to recapitulate CTC size distributions with large clusters of 5 to 10 cells. Second, multiple intermediate E/M states give rise to larger and heterogeneous clusters formed by cells with different epithelial-mesenchymal traits. Overall, this biophysical model provides a platform to continue to bridge the gap between the molecular and biophysical regulation of cancer cell migration and highlights that a complete EMT might not be required for metastasis. SIGNIFICANCE: A biophysical model of cancer cell invasion integrates phenotypic heterogeneity and cell migration to interpret experimental observations of circulating tumor cell clusters and provides new predictions.Graphical Abstract: http://cancerres.aacrjournals.org/content/canres/79/21/5527/F1.large.jpg.

Metastatic seeding of human colon cancer cell clusters expressing the hybrid epithelial/mesenchymal state.

Emerging evidence supports the theory that tumor cell clusters efficiently metastasize to distant organs. However, the roles of epithelial-to-mesenchymal transition (EMT) in metastasizing tumor cell clusters have not yet been fully elucidated. To investigate this issue, tumor fragments were dissected from 40 colorectal cancer (CRC) patients and implanted subcutaneously into immunodeficient mice. We observed that tumors developed from the tumor fragments obtained from 28 of the 40 CRC patients. The tumors were then dissociated into cell suspensions to be orthotopically injected into secondary mice. The tumors from 13 of the 28 patients progressed. Furthermore, metastases formed spontaneously in the liver and lungs from the tumor fragments obtained from 8 of these 13 patients. Moreover, employing a mathematical analysis, we showed that tumor cell clusters seeded these metastases significantly more often than did single tumor cells. Membrane E-cadherin- and nuclear ZEB1-positive tumor cells indicating the hybrid epithelial/mesenchymal state were also detected in primary tumors of various CRC patients, and in the corresponding patient-derived xenografts (PDXs) and circulating tumor cell clusters in the bloodstreams of mice. In contrast, ZEB1 staining was barely detectable in the patient-matched liver metastases presumably developing through mesenchymal-to-epithelial transition. Inhibition of E-cadherin or ZEB1 expression by shRNA notably prevented the PDX-derived tumor organoids from colonizing the liver, when injected intrasplenically into mice, indicating E-cadherin and ZEB1 expressions to be required for their metastatic colonization. Taken together, these findings suggest that the epithelial/mesenchymal state mediates metastatic seeding of human CRC cell clusters into distant organs.

High Clinical Value of Liquid Biopsy to Detect Circulating Tumor Cells and Tumor Exosomes in Pancreatic Ductal Adenocarcinoma Patients Eligible for Up-Front Surgery.

Purpose: Expediting the diagnosis of pancreatic ductal adenocarcinoma (PDAC) would benefit care management, especially for the start of treatments requiring histological evidence. This study evaluated the combined diagnostic performance of circulating biomarkers obtained by peripheral and portal blood liquid biopsy in patients with resectable PDAC. Experimental design: Liquid biopsies were performed in a prospective translational clinical trial (PANC-CTC #NCT03032913) including 22 patients with resectable PDAC and 28 noncancer controls from February to November 2017. Circulating tumor cells (CTCs) were detected using the CellSearch® method or after RosetteSep® enrichment combined with CRISPR/Cas9-improved KRAS mutant alleles quantification by droplet digital PCR. CD63 bead-coupled Glypican-1 (GPC1)-positive exosomes were quantified by flow cytometry. Results: Liquid biopsies were positive in 7/22 (32%), 13/22 (59%), and 14/22 (64%) patients with CellSearch® or RosetteSep®-based CTC detection or GPC1-positive exosomes, respectively, in peripheral and/or portal blood. Liquid biopsy performance was improved in portal blood only with CellSearch®, reaching 45% of PDAC identification (5/11) versus 10% (2/22) in peripheral blood. Importantly, combining CTC and GPC1-positive-exosome detection displayed 100% of sensitivity and 80% of specificity, with a negative predictive value of 100%. High levels of GPC1+-exosomes and/or CTC presence were significantly correlated with progression-free survival and with overall survival when CTC clusters were found. Conclusion: This study is the first to evaluate combined CTC and exosome detection to diagnose resectable pancreatic cancers. Liquid biopsy combining several biomarkers could provide a rapid, reliable, noninvasive decision-making tool in early, potentially curable pancreatic cancer. Moreover, the prognostic value could select patients eligible for neoadjuvant treatment before surgery. This exploratory study deserves further validation.

A CTC-Cluster-Specific Signature Derived from OMICS Analysis of Patient-Derived Xenograft Tumors Predicts Outcomes in Basal-Like Breast Cancer.

Circulating tumor cell clusters (CTCcl) have a higher metastatic potential compared to single CTCs and predict long-term outcomes in breast cancer (BC) patients. Because of the rarity of CTCcls, molecular characterization of primary tumors that give rise to CTCcl hold significant promise for better diagnosis and target discovery to combat metastatic BC. In our study, we utilized the reverse-phase protein array (RPPA) and transcriptomic (RNA-Seq) data of 10 triple-negative BC patient-derived xenograft (TNBC PDX) transplantable models with CTCs and evaluated expression of upregulated candidate protein Bcl2 (B-cell lymphoma 2) by immunohistochemistry (IHC). The sample-set consisted of six CTCcl-negative (CTCcl−) and four CTCcl-positive (CTCcl+) models. We analyzed the RPPA and transcriptomic profiles of CTCcl− and CTCcl+ TNBC PDX models. In addition, we derived a CTCcl-specific gene signature for testing if it predicted outcomes using a publicly available dataset from 360 patients with basal-like BC. The RPPA analysis of CTCcl+ vs. CTCcl− TNBC PDX tumors revealed elevated expression of Bcl2 (false discovery rate (FDR) < 0.0001, fold change (FC) = 3.5) and reduced acetyl coenzyme A carboxylase-1 (ACC1) (FDR = 0.0005, FC = 0.3) in CTCcl+ compared to CTCcl− tumors. Genome-wide transcriptomic analysis of CTCcl+ vs. CTCcl− tumors revealed 549 differentially expressed genes associated with the presence of CTCcls. Apoptosis was one of the significantly downregulated pathways (normalized enrichment score (NES) = −1.69; FDR < 0.05) in TNBC PDX tumors associated with CTCcl positivity. Two out of four CTCcl+ TNBC PDX primary tumors had high Bcl2 expression by IHC (H-score > 34); whereas, only one of six CTCcl− TNBC PDX primary tumors met this criterion. Evaluation of epithelial-mesenchymal transition (EMT)-specific signature did not show significant differences between CTCcl+ and CTCcl− tumors. However, a gene signature associated with the presence of CTCcls in TNBC PDX models was associated with worse relapse-free survival in the publicly available dataset from 360 patients with basal-like BC. In summary, we identified the multigene signature of primary PDX tumors associated with the presence of CTCcls. Evaluation of additional TNBC PDX models and patients can further illuminate cellular and molecular pathways facilitating CTCcl formation.

Circulating Tumor Cell Clusters in Patients with Metastatic Breast Cancer: a SWOG S0500 Translational Medicine Study.

Metastasis requires malignant cell circulation from the primary to a distant tissue. Elevated levels of circulating tumor cells (CTC) portend a poor prognosis in breast and other cancers. Recent studies have suggested that CTC clusters may be a factor in the metastatic process. We conducted a prospective retrospective study of the SWOG0500 clinical trial to test whether CTC clusters are associated with poorer prognosis. CTC CellSearch galleries from SWOG0500 trial were reread using prespecified criteria for CTC clusters, doublets, and enumeration. Survival analysis methods include Kaplan-Meier plots and log-rank tests. Patients were classified into three prognostic subgroups based on baseline CTC/7.5 mL whole blood (WB): Arm A: <5CTC; Arm B/C: ≥5CTC and then B (<5CTC) and C (≥5CTC)/7.5 mL WB at first follow-up. At baseline, 19% of patients had CTC doublets or clusters, which were more likely in Arm B/C versus Arm A (38% vs. 1.4%; P < 0.0001). Furthermore, doublets or clusters were significantly more common in patients who were ultimately assigned to Arm C versus B (54% vs. 25%; P < 0.0001). In Arm C, doublets and clusters were associated with worse overall survival than only doublets, clusters, or no doublets nor clusters at baseline (P = 0.008) and first follow-up (P = 0.010). When compared with enumeration alone, doublets, clusters, or both were not prognostic in patients who had 5-19 or ≥20 CTC/7.5 mL WB. In patients with metastatic breast cancer starting first-line chemotherapy, mortality is independent of the presence of CTC clusters, but rather depends on the number of CTC/7.5 mL WB.