Single Cell Secretome Analyses of Hepatic Stellate Cells: Aiming for Single Cell Phenomics

Activated hepatic stellate cells (HSCs) that secrete large amounts of extracellular matrix (ECM) proteins, primarily collagens, are recognized as the key pathogenic cells in liver diseases. Excessive ECM accumulation results in tissue scarring, referred to as liver fibrosis, that progresses to liver cirrhosis (liver dysfunction) and hepatocellular carcinoma. Recent studies using single cell RNA sequencing have discovered various subpopulations of HSCs with high degree of heterogeneity in quiescent, activated, as well as inactive (identified during disease regression) HSCs. However, little is known about the role of these subpopulations in ECM secretion and cell-cell communication or if they respond differently to different exogenous and endogenous factors. Moreover, how the heterogenous single cell transcriptome translates into the single cell secretome and "communicatome" (cell-cell communication) remains largely underexplored. In this chapter, we describe the method (modified enzyme-linked immunosorbent spot, ELISpot) for analyzing collagen type 1 secretion of HSCs at the single cell level, enabling a deeper understanding into the HSC secretome. In the near future, we aim to develop an integrated platform with which we can study secretome of individual cells identified by immunostaining-based fluorescence-activated cell sorting derived from healthy and diseased liver. Through the use of the VyCAP 6400-microwell chip in combination with their puncher device, we aim to perform single cell phenomics by analyzing and correlating phenotype, secretome, transcriptome, and genome of the single cells.

Optimal Halbach Configuration for Flow-through Immunomagnetic CTC Enrichment

Due to the low frequency of circulating tumor cells (CTC), the standard CellSearch method of enumeration and isolation using a single tube of blood is insufficient to measure treatment effects consistently, or to steer personalized therapy. Using diagnostic leukapheresis this sample size can be increased; however, this also calls for a suitable new method to process larger sample inputs. In order to achieve this, we have optimized the immunomagnetic enrichment process using a flow-through magnetophoretic system. An overview of the major forces involved in magnetophoretic separation is provided and the model used for optimizing the magnetic configuration in flow through immunomagnetic enrichment is presented. The optimal Halbach array element size was calculated and both optimal and non-optimal arrays were built and tested using anti-EpCAM ferrofluid in combination with cell lines of varying EpCAM antigen expression. Experimentally measured distributions of the magnetic moment of the cell lines used for comparison were combined with predicted recoveries and fit to the experimental data. Resulting predictions agree with measured data within measurement uncertainty. The presented method can be used not only to optimize magnetophoretic separation using a variety of flow configurations but could also be adapted to optimize other (static) magnetic separation techniques.

EPAC-lung: European pooled analysis of the prognostic value of circulating tumour cells in small cell lung cancer

BACKGROUND

Circulating tumour cell (CTC) number is an independent prognostic factor in patients with small cell lung cancer (SCLC) but there is no consensus on the CTC threshold for prognostic significance. We undertook a pooled analysis of individual patient data to clinically validate CTC enumeration and threshold for prognostication.

METHODS

Four European cancer centres, experienced in CellSearch CTC enumeration for SCLC provided pseudo anonymised data for patients who had undergone pre-treatment CTC count. Data was collated, and Cox regression models, stratified by centre, explored the relationship between CTC count and survival. The added value of incorporating CTCs into clinico-pathological models was investigated using likelihood ratio tests.

RESULTS

A total of 367 patient records were evaluated. A one-unit increase in log-transformed CTC counts corresponded to an estimated hazard ratio (HR) of 1.24 (95% CI: 1.19-1.29, P<0.0001) for progression free survival (PFS) and 1.23 (95% CI: 1.18-1.28, P<0.0001) for overall survival (OS). CTC count of ≥15 or ≥50 was significantly associated with an increased risk of progression (CTC ≥15: HR 3.20, 95% CI: 2.50-4.09, P<0.001; CTC ≥50: HR 2.56, 95% CI: 2.01-3.25, P<0.001) and an increased risk of death (CTC ≥15: HR 2.90, 95% CI: 2.28-3.70, P<0.001; CTC ≥50: HR 2.47, 95% CI: 1.95-3.13, P<0.001). There was no significant inter-centre heterogeneity observed. Addition of CTC count to clinico-pathological models as a continuous log-transformed variable, offers further prognostic value (both likelihood ratio P<0.001 for OS and PFS).

CONCLUSIONS

Higher pre-treatment CTC counts are a negative independent prognostic factor in SCLC when considered as a continuous variable or dichotomised counts of ≥15 or ≥50. Incorporating CTC counts, as a continuous variable, improves clinic-pathological prognostic models.

CD38 in Advanced Prostate Cancers

Background

CD38, a druggable ectoenzyme, is involved in the generation of adenosine, which is implicated in tumour immune evasion. Its expression and role in prostate tumour-infiltrating immune cells (TIICs) have not been elucidated.

Objective

To characterise CD38 expression on prostate cancer (PC) epithelial cells and TIICs, and to associate this expression with clinical outcomes.

Design, setting, and participants

RNAseq from 159 patients with metastatic castration-resistant prostate cancer (mCRPC) in the International Stand Up To Cancer/Prostate Cancer Foundation (SU2C/PCF) cohort and 171 mCRPC samples taken from 63 patients in the Fred Hutchinson Cancer Research Centre cohort were analysed. CD38 expression was immunohistochemically scored by a validated assay on 51 castration-resistant PC (CRPC) and matching, same-patient castration-sensitive PC (CSPC) biopsies obtained between 2016 and 2018, and was associated with retrospectively collected clinical data.

Outcome measurements and statistical analysis

mCRPC transcriptomes were analysed for associations between CD38 expression and gene expression signatures. Multiplex immunofluorescence determined CD38 expression in PC biopsies. Differences in CD38⁺ TIIC densities between CSPC and CRPC biopsies were analysed using a negative binomial mixed model. Differences in the proportions of CD38⁺ epithelial cells between non-matched benign prostatic epithelium and PC were compared using Fisher’s exact test. Differences in the proportions of biopsies containing CD38⁺ tumour epithelial cells between matched CSPC and CRPC biopsies were compared by McNemar’s test. Univariable and multivariable survival analyses were performed using Cox regression models.

Results and limitations

CD38 mRNA expression in mCRPC was most significantly associated with upregulated immune signalling pathways. CD38 mRNA expression was associated with interleukin (IL)-12, IL-23, and IL-27 signalling signatures as well as immunosuppressive adenosine signalling and T cell exhaustion signatures. CD38 protein was frequently expressed on phenotypically diverse TIICs including B cells and myeloid cells, but largely absent from tumour epithelial cells. CD38⁺ TIIC density increased with progression to CRPC and was independently associated with worse overall survival. Future studies are required to dissect TIIC CD38 function.

Conclusions

CD38⁺ prostate TIICs associate with worse survival and immunosuppressive mechanisms. The role of CD38 in PC progression warrants investigation as insights into its functions may provide rationale for CD38 targeting in lethal PC.

Patient summary

CD38 is expressed on the surface of white blood cells surrounding PC cells. These cells may impact PC growth and treatment resistance. Patients with PC with more CD38-expressing white blood cells are more likely to die earlier.

Abstract PO003: CD38 in the advanced prostate cancer

Background: CD38, an ecto-enzyme involved in adenosine synthesis, is implicated in tumor immune evasion. Its expression and role in the prostate tumor microenvironment (TME) has not been fully elucidated. Main objectives: To determine whether CD38 is associated with prostate cancer (PC) immune evasion, to characterize CD38 expression on PC epithelial cells and tumor infiltrating immune cells (TIICs) as tumors progress from castration-sensitive PC (CSPC) to metastatic castration-resistant PC (mCRPC), and to determine the association between CD38+ TIICs and survival.

Methods: Data from 159 mCRPC transcriptomes from the Stand Up To Cancer/Prostate Cancer Foundation cohort were analyzed for associations between CD38 and 200 cell signaling pathways, an adenosine signature and T cell exhaustion signatures. CD38 protein expression on tumor epithelial cells and TIICs was scored using validated immunohistochemistry (IHC) assays on 51 treatment-naïve CSPC biopsies and matching, same-patient mCRPC biopsies obtained between 2016-2018 from men treated at The Royal Marsden Hospital. To characterize CD38+ TIICs, CD38 co-expression with immune cell surface markers for T cells (CD3), B cells (CD19, CD20, CD138, CD79a), and myeloid cells (CD11b, CD15, CD33) was determined by dual-color IHC or multiplex immunofluorescence. The change in CD38+ TIICs density from CSPC to mCRCP was assessed by negative binomial regression and the associations between CD38+ TIIC density and survival were studied using Kaplan-Meier methods, Cox regression and the log-rank test.

Results: Unbiased transcriptome analyses showed that CD38 mRNA expression in mCRPC was associated with upregulated immune signaling pathways, with the ten pathways showing the strongest evidence of association (all P &lt; 1 × 10^-10) with CD38 mRNA expression all being immunomodulatory. CD38 expression was associated with IL-23 signaling (P &lt; 1 × 10^-10), a myeloid suppressor cell-derived mediator of endocrine resistance, as well as immunosuppressive adenosine signaling (P &lt; 1 × 10^-8) and T cell exhaustion signatures (P &lt; 1 × 10^-10). CD38 protein was largely absent from tumor epithelial cells (7.7%). CD38 was expressed by phenotypically diverse TIICs. CD38+ TIICs co-expressed myeloid cell surface markers (CD33, CD15), B cell surface markers (CD19, CD20, CD79a, CD138), and the T cell surface marker (CD3). CD38+ TIIC density increased as tumors progressed from CSPC to CRPC (negative binomial regression, P = 0.03). CSPC and CRPC with higher CD38+ TIIC density (dichotomized based on the median; &gt; 1.5 cells/mm^2) were associated with shorter overall survival from the time of PC diagnosis (hazard ratio [HR]: 1.89; 95% CI: 1.02-3.50) and the time of mCRPC biopsy (HR: 2.14; 95% CI: 1.15-4.00), respectively.

Conclusion: CD38 is expressed by diverse TIICs in the prostate TME and was associated with potential mechanisms of immune evasion. CD38 expression may serve as a potential prognostic biomarker and therapeutic target in PC aimed at overcoming PC immunoresistance.

Citation Format: Christina Guo, Mateus Crespo, Bora Gurel, David Dolling, Jan Rekowski, Adam Sharp, Antonella Petremolo, Semini Sumanasuriya, Daniel N. Rodrigues, Ana Ferreira, Rita Pereira, Ines Figueiredo, Niven Mehra, Maryou B.K. Lambros, Antje Neeb, Veronica Gil, Leon Terstappen, Andrea Alimonti, Charles G. Drake, Wei Yuan, Johann S. de Bono. CD38 in the advanced prostate cancer [abstract]. In: Abstracts: AACR Virtual Special Conference: Tumor Immunology and Immunotherapy; 2020 Oct 19-20. Philadelphia (PA): AACR; Cancer Immunol Res 2021;9(2 Suppl):Abstract nr PO003.

Abstract 2693: Detection of PSA secretion from single prostate cancer cells with and without drug stimulation

Treatment options available for cancer patients are increasing rapidly. Biomarkers to predict which therapies will be effective are however lacking, resulting in the frequent administration of ineffective therapies. Emergence of therapy resistance and both inter-patient and intra-patient heterogeneity play an important role in the differences in response to treatment in prostate cancer (PC). Therefore, research into the nature of the heterogeneity and its significance will aid in developing an improved individualized treatment strategy. Here we use a microwell technology that can enable the testing of drug effectivity and heterogeneity of tumor cells.

Several techniques exist to study secreted proteins, including enzyme-linked immunosorbent assay (ELISA), enzyme-linked immunosorbent spot (ELISpot), intracellular staining, and cytokine capture. The common immunoassays that directly measure secreted proteins on a solid support (ELISA and ELISpot) fail to correlate the captured analytes with the producing cell and cannot do this repeatedly on the same cell. We used the microwell technology to sort viable single cells derived from the prostate cancer cell lines LnCAP and VcCAP. The Prostate Specific Antigen (PSA) produced by LnCAP and VcAP cells is measured with or without drug stimulation (r1881, Enzalutamide or Abiraterone). To measure PSA secretion the microwell is connected to a membrane coated with antibodies against PSA.

We demonstrate that PSA secreted by cells can be measured and we quantified the amounts for &gt;1200 single PC cells. Before cells were subjected to drug stimulation PSA secretion was measured. Results indicate a heterogeneous PSA secretion profile for both cell lines; the average LnCAP secretion patterns were 4,7 (sd=3,3), 11,3 (sd=5,9) and 2,4 (sd=1,1) pg/cell for respectively, non-stimulated, r1881 androgen steroid and Enzalutamide respectively. LnCAPs stimulated with Abiraterone secreted 4,7 (sd=1,9) pg/cell, indicating that enzalutamide has a higher inhibitory effect on PSA secretion than abiraterone. VcAPs secreted 3,8 (sd=1,8), 6,5 (sd=4,1) and 0,9 (sd=0,7) pg/cell for non-stimulated, r1881 androgen steroid and enzalutamide stimulated cells respectively. Abiraterone stimulated cells secreted 2,0 (sd=1,5) pg/cell. The results further suggest that a small percentage of LnCAP of the cells (&lt;1%) did not respond to Enzalutamide treatment indicating resistance to the drug. We expect that this approach can enable to study and predict the efficacy of the clinical response to drug and ultimately improve the success rate of treatment of PC patients.

This research is part of the HTSM research programme and was partly funded by the NWO, The Netherlands Organization for Scientific Research (Utrecht, The Netherlands) and is part of Project McSPRinter under project number 15327.

Citation Format: Fikri Abali, Narghes Baghi, Arjan Tibbe, Leon Terstappen. Detection of PSA secretion from single prostate cancer cells with and without drug stimulation [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2693.

EPAC-lung: pooled analysis of circulating tumour cells in advanced non-small cell lung cancer

INTRODUCTION

We assessed the clinical validity of circulating tumour cell (CTC) quantification for prognostication of patients with advanced non-small cell lung cancer (NSCLC) by undertaking a pooled analysis of individual patient data.

METHODS

Nine European NSCLC CTC centres were asked to provide reported/unreported pseudo-anonymised data for patients with advanced NSCLC who participated in CellSearch CTC studies from January 2003 to March 2017. We used Cox regression models, stratified by centres, to establish the association between CTC count and survival. We assessed the added value of CTCs to prognostic clinicopathological models using likelihood ratio (LR) statistics and c-indices.

RESULTS

Seven out of nine eligible centres provided data for 550 patients with prognostic information for overall survival. CTC counts of ≥2 and ≥ 5 per 7·5 mL were associated with reduced progression-free survival (≥2 CTCs: hazard ratio [HR] = 1.72, p < 0·001; ≥5 CTCs: HR = 2.21, p < 0·001) and overall survival (≥2 CTCs: HR = 2·18, p < 0·001; ≥5 CTCs: HR = 2·75, p < 0·001), respectively. Survival prediction was significantly improved by addition of baseline CTC count to LR clinicopathological models (log-transformed CTCs p < 0·001; ≥2 CTCs p < 0·001; ≥5 CTCs p ≤ 0·001 for both survival end-points), whereas moderate improvements were observed with the use of c-index models. There was some evidence of between-centre heterogeneity, especially when examining continuous counts of CTCs.

CONCLUSIONS

These data confirm CTCs as an independent prognostic indicator of progression-free survival and overall survival in advanced NSCLC and also reveal some evidence of between-centre heterogeneity. CTC count improves prognostication when added to full clinicopathological predictive models.

Abstract 5600: Establishment and characterization of a unique circulating tumor cells-derived xenograft (CDX) in prostate cancer

Background: The rarity of in vivo and in vitro human prostate cancer (PCa) models has hampered progress in understanding disease pathogenesis, metastatic progression and drug resistance mechanisms. Using CTCs from a leukapheresis product of a patient with advanced PCa, we report the establishment of a CDX and an in vitro cell line derived from this CDX. The phenotypic and molecular characterization of patient tumor-biopsies, CTCs, CDX and CDX-derived cell-line are presented.

Methods: Leukapheresis was performed in seven patients with advanced castration-resistant prostate cancer (CRPC). CTCs from the seven leukapheresis products were enriched by RosetteSep and implanted in Nod/Scid-IL2Rγ-/-mice. The CDX tumor was propagated in successive generations of mice. All samples, including eight tumor-biopsies performed at diagnosis two years prior leukapheresis and CTCs isolated at the single cell level during leukapheresis were characterized by immunofluorescence, immunohistochemistry, and whole-exome sequencing (WES).

Results: Based on CellSearch® counts in leukapheresis products, the estimated median number of engrafted CTCs was 697 (range: 10-19988). A mouse engrafted with 19988 CTCs developed a tumor within 193 days. Immunohistochemistry performed on the CDX and two tumor-biopsies indicated that the CDX and biopsies were positive for EpCAM, CK5/6/8/18, negative for CK7 and vimentin, and weakly positive for synaptophysin. While biopsies expressed PSA and the androgen receptor, the CDX was negative for both indicating tumor evolution. In contrast to tumor biopsies, the CDX strongly expressed Ki67, NSE and chromogranin, evidencing emergence of a neuroendocrine phenotype. The in vitro cell line established by culturing dissociated CDX cells for five months, grew in microspheres and expressed epithelial and ALDH and CD133 cancer stem-cell markers. By WES, a high degree of intra-tumor heterogeneity was observed in the eight tumor biopsies and CTCs as already reported in this tumor type. Only 2.8% (58/2087) and 2.3% (49/2087) of the mutations present in the tumor biopsies were identified in CTCs and the CDX respectively, indicating that a very few number of mutations have the potential to support the dissemination and tumorigenic activity of CTC. Trunk mutations in TP53, NF1 and LRP1B genes were identified in all samples including the CDX while PTEN gene loss was acquired lately and detected only in CTCs and the CDX. Mutational similarity of the CDX and the in vitro cell line was 91%. The analysis of copy number variations is ongoing in all samples and will be presented.

Conclusion: We report the first PCa CDX model, demonstrating the tumorigenicity of CTCs from CRPC. This CDX model represents a unique tool to identify clonal mutations associated with the tumor-initiating capacity of CTCs and explore the genetic and phenotypic basis of metastasis and drug resistance in advanced CRPC.

Citation Format: Vincent Faugeroux, Emma Pailler, Olivier Deas, Virginie Marty, Kamélia Alexandrova, Kiki Andree, Jean-Yves Scoazec, Nikolas Stoecklein, Nicolo Manaresi, Dominique Tramalloni, Maud Ngo-Camus, Claudio Nicotra, Leon Terstappen, Valérie Lapierre, Karim Fizazi, Yohann Loriot, Jean-Gabriel Judde, Françoise Farace. Establishment and characterization of a unique circulating tumor cells-derived xenograft (CDX) in prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5600.

Interrogating Metastatic Prostate Cancer Treatment Switch Decisions: A Multi-institutional Survey

BACKGROUND

Evaluation of responses to treatment for metastatic castration-resistant prostate cancer (mCRPC) remains challenging. Consensus criteria based on prostate-specific antigen (PSA) and clinical and radiologic biomarkers are inconsistently utilized. Circulating tumor cell (CTC) counts can inform prognosis and response, but are not routinely used.

OBJECTIVE

To evaluate the use of biomarkers and trends in clinical decision-making in current mCRPC treatment.

DESIGN, SETTING, AND PARTICIPANTS

A 23-part online questionnaire was completed by physicians treating mCRPC.

OUTCOME MEASURES AND STATISTICAL ANALYSIS

Results are presented as the proportion (%) of physicians responding to each of the options. We used χ2 and Fisher's tests to compare differences.

RESULTS AND LIMITATIONS

A total of 118 physicians (22.1%) responded. Of these, 69.4% treated ≥50 mCRPC patients/year. More physicians administered four or fewer courses of cabazitaxel (27.9%) than for docetaxel (10.4%), with no significant difference in the number of courses between bone-only disease and Response Evaluation Criteria in Solid Tumours (RECIST)-evaluable disease. Some 74.5% of respondents considered current biomarkers useful for monitoring disease, but only 39.6% used the Prostate Cancer Working Group (PCWG2) criteria in clinical practice. PSA was considered an important biomarker by 55.7%, but only 41.4% discarded changes in PSA before 12 wk, and only 39.4% were able to identify bone-scan progression according to PCWG2. The vast majority of physicians (90.5%) considered clinical progression to be important for switching treatment. The proportion considering biomarkers important was 71.6% for RECIST, 47.4% for bone scans, 23.2% for CTCs, and 21.1% for PSA. Although 53.1% acknowledged that baseline CTC counts are prognostic, only 33.7% would use CTC changes alone to switch treatment in patients with bone-only disease. The main challenges in using CTC counts were access to CTC technology (84.7%), cost (74.5%), and uncertainty over utility as a response indicator (58.2%).

CONCLUSIONS

A significant proportion of physicians discontinue treatment for mCRPC before 12 wk, raising concerns about inadequate response assessment. Many physicians find current biomarkers useful, but most rely on symptoms to drive treatment switch decisions, suggesting there is a need for more precise biomarkers.

PATIENT SUMMARY

In this report we analyse the results of a questionnaire evaluating tools for clinical decision-making completed by 118 prostate cancer specialists. We found that most physicians favour clinical progression over prostate-specific antigen or imaging, and that criteria established by the Prostate Cancer Working Group are not widely used.

Abstract 513: Standardization of technologies for CTC, ctDNA and miRNA enrichment, isolation and analysis for liquid biopsies during the first year of IMI's CANCER-ID

Within the European Innovative Medicines Initiative (IMI) consortium CANCER-ID (www.cancer-id.eu), scientists at academic, clinical and industrial sites across Europe and in the US joined forces to evaluate innovative technologies in the field of liquid cancer biopsies. This project aims at implementing standard operating procedures (SOPs) for pre-analytical sample handling, enrichment, isolation and analysis of Circulating Tumor Cells (CTCs), circulating free tumor DNA (ctDNA) and microRNAs (miRNAs) as novel blood-based biomarkers, with a focus on Non-Small Cell Lung Cancer (NSCLC) and HER2-treatment refractory breast cancer. In order to determine sensitivity and specificity of different technologies for CTC isolation and analysis (e.g. detection of mutations, amplifications, protein phosphorylation), complex samples comprising a mixture of NSCLC or breast cancer cell lines spiked in healthy donor blood were distributed to different CANCER-ID partner sites. These cell lines have been selected based on their molecular/genetic properties to reflect clinically relevant subtypes of the disease and have been further characterized in terms of cell-surface marker expression and cell size distribution. The use of complex spiked samples better models the heterogeneity of real-life patient material. Furthermore, healthy donor and patient derived plasma samples are investigated using different technology platforms to validate tumor-specific miRNA or ctDNA profiles that might characterize molecular tumor subtypes. To this end, differences in exosome-derived versus free circulating miRNAs are of special interest. As for CTCs the development of ctDNA and miRNA standards that can be used to compare and validate different technologies are in the focus of this effort. In summary, our results pave the way for the next phase of CANCER-ID, which includes the analysis of cancer patient samples in clinical studies using different technologies and thereby advance the concept of liquid biopsy particularly in indications in which conventional tissue biopsies are difficult to obtain.

Citation Format: Thomas Schlange, Nikolas Stoecklein, Rui P. Neves, Sabrina Pleier, Sebastian Bender, Nora Brychta, Merlin V. Luetke-Eversloh, Kiki Andree, Leon Terstappen, Thomas Krahn, Thomas Krahn. Standardization of technologies for CTC, ctDNA and miRNA enrichment, isolation and analysis for liquid biopsies during the first year of IMI's CANCER-ID. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 513.

Detection and Characterization of Circulating Tumor Cells by the CellSearch Approach

Cancer metastasis occurs when cells shed from a primary or metastatic tumor, enter the circulation, and begin to grow in distant locations of the body. With current techniques it is possible to measure the presence of a few circulating tumor cells (CTC) in a blood sample. Detection of even the presence of a very small number (one or more) of these CTC in a 7.5 mL blood sample with the CellSearch system is associated with a significant decrease in survival of patients with metastatic carcinomas. The techniques and definitions used for the detection and enumeration of CTC with the CellSearch system were validated in series of preclinical and prospective multicenter studies. After enumeration of the CTC, the cells can be isolated from the cartridge for the purpose of downstream single-cell analysis. In this chapter, we will describe in detail the sample acquisition, sample preparation, data acquisition, and assignment of CTC used in the CellSearch system.

Abstract 4825: Circulating tumor cells in metastatic lung cancer enriched by EpCAM expression and physical characteristics

Introduction: Circulating tumor cells (CTC) measured with the CellSearch system in patients with metastatic carcinomas are associated with poor survival. The frequency of CTC detected by the CellSearch system in non-small cell lung cancer (NSCLC) patients is relatively low, raising the question whether some CTC are not detected by the CellSearch system. To investigate this, additional antibodies were added to broaden the coverage of cytokeratins and leukocytes. Additionally, a device was designed that collects the sample material of the individual samples that are discarded by CellSearch. This collected waste is filtered for CTC isolation based on physical characteristics and the CTC are stained with a cocktail of antibodies.

Methods: A device was designed that uses optical sensing to detect the presence of blood in the waste tube of the CellTracks Autoprep. It collects the waste of individual samples in a 50 mL conical tube. After collection the blood is passed with 100 mbar pressure through a 8x8 mm2 microfabricated silicon microsieve containing 300,000 pores of 5 µm in diameter (VyCAP, Deventer, The Netherlands). The performance was tested using four pre-stained cell lines: Colo320 (size 11 µm, ∼1,616 EpCAM antigens), SW480 (size 11 µm, ∼63,233 EpCAM antigens), T24 (size 16 µm, ∼2,167 EpCAM antigens) and SKBR3 (size 16 µm, ∼445,000 EpCAM antigens). Cells are spiked in 7.5 mL of blood collected in CellSave tubes from healthy volunteers. Spiked blood samples from healthy donors and patients with NCSLC and small cell lung cancer (SCLC) (enrollment is ongoing) were processed on the CellSearch and filtration system between 24 and 96 hours of collection. The cells on the microsieves were stained with a nucleic acid dye, antibodies recognizing leukocytes and all cytokeratins. Additional antibodies were added to the CellSearch test to cover all cytokeratins and broaden the coverage of leukocytes.

Results: The recovery percentage of the CellSearch system for the different cell lines used was: 2% of COLO320, 91% of SW480, 2% of T24 and 87% of SKBR3. Additional recovery on the microsieves after filtration of the CellSearch waste was: 18% of COLO320, 6% of SW480, 59% of T24 and 2% of SKBR3. The combined recovery accounts for 20% of COLO320, 97% of SW480, 61% of T24 cells and 89% of SKBR3. In patients with NSCLC and SCLC either no CTC were detected at all, or in various proportions in the CellSearch cartridge, on the microsieves after filtration of the CellSearch waste or with the additional antibodies that were added.

Conclusions: We combined the CellSearch system with a device for collecting and filtering the CellSearch waste. On cell lines this demonstrated that a low EpCAM expression results in the presence of CTC in the waste that would not be detected by the CellSearch system. In both NSCLC and SCLC additional CTC can be detected but it still remains to be determined whether the CTC not detected by the original CellSearch approach are also of clinical relevance.

Citation Format: Sanne de Wit, Guus van Dalum, Joost van Dalum, Aufried Lenferink, Arjan Tibbe, Cees van Rijn, Jeroen Hiltermann, Harry Groen, Leon Terstappen. Circulating tumor cells in metastatic lung cancer enriched by EpCAM expression and physical characteristics. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4825. doi:10.1158/1538-7445.AM2014-4825

A novel side electrode configuration integrated in fused silica microsystems for synchronous optical and electrical spectroscopy

We present a novel electrode configuration consisting of coplanar side electrode pairs integrated at the half height of the microchannels for the creation of a homogeneous electric field distribution as well as for synchronous optical and electrical measurements. For the integration of such electrodes in fused silica microsystems, a dedicated microfabrication method was utilized, whereby an intermediate bonding layer was applied to lower the temperature for fusion bonding to avoid thereby metal degradation and subsequently to preserve the electrode structures. Finally, we demonstrate the applicability of our devices with integrated electrodes for single cell electrical lysis and simultaneous fluorescence and impedance measurements for both cell counting and characterization.

International study on inter-reader variability for circulating tumor cells in breast cancer

Introduction

Circulating tumor cells (CTCs) have been studied in breast cancer with the CellSearch® system. Given the low CTC counts in non-metastatic breast cancer, it is important to evaluate the inter-reader agreement.

Methods

CellSearch® images (N = 272) of either CTCs or white blood cells or artifacts from 109 non-metastatic (M0) and 22 metastatic (M1) breast cancer patients from reported studies were sent to 22 readers from 15 academic laboratories and 8 readers from two Veridex laboratories. Each image was scored as No CTC vs CTC HER2- vs CTC HER2+. The 8 Veridex readers were summarized to a Veridex Consensus (VC) to compare each academic reader using % agreement and kappa (κ) statistics. Agreement was compared according to disease stage and CTC counts using the Wilcoxon signed rank test.

Results

For CTC definition (No CTC vs CTC), the median agreement between academic readers and VC was 92% (range 69 to 97%) with a median κ of 0.83 (range 0.37 to 0.93). Lower agreement was observed in images from M0 (median 91%, range 70 to 96%) compared to M1 (median 98%, range 64 to 100%) patients (P < 0.001) and from M0 and <3CTCs (median 87%, range 66 to 95%) compared to M0 and ≥3CTCs samples (median 95%, range 77 to 99%), (P < 0.001). For CTC HER2 expression (HER2- vs HER2+), the median agreement was 87% (range 51 to 95%) with a median κ of 0.74 (range 0.25 to 0.90).

Conclusions

The inter-reader agreement for CTC definition was high. Reduced agreement was observed in M0 patients with low CTC counts. Continuous training and independent image review are required.

Circulating tumor cells expressing the insulin growth factor-1 receptor (IGF-1R): Method of detection, incidence and potential applications

3507

Purpose: To detect IGF-1R on circulating tumor cells (CTCs) as a biomarker in the clinical development of a monoclonal human antibody, CP-751,871, targeting IGF-1R. Experimental Design: An automated sample preparation and analysis system for enumerating CTCs (Celltracks) was adapted for detecting IGF-1R positive CTCs with a diagnostic antibody targeting a different IGF-1R epitope to CP-751,871. This assay was utilized in three phase I trials of CP-751,871 as a single agent or with chemotherapy and was validated using cell lines and blood samples from healthy volunteers and patients with metastatic carcinoma. Results: There was no interference between the analytical and therapeutic antibodies. CP-751,871 was well tolerated as a single agent, and in combination with docetaxel or carboplatin and paclitaxel, at doses ranging from 0.05 mg/kg to 20 mg/kg. Eighty patients were enrolled on phase 1 studies of CP-751,871, with 47 (59%) patients having CTCs detected during the study. Prior to treatment 26 patients (33%) had CTCs, with 23 having detectable IGF-1R positive CTCs. CP-751,871 alone, and CP-751,871 with cytotoxic chemotherapy, decreased CTCs and IGF-1R positive CTCs; these increased towards the end of the 21-day cycle in some patients, falling again with retreatment. CTCs were commonest in advanced hormone refractory prostate cancer (11/20). Detectable IGF-1R expression on CTCs before treatment with CP-751,871 and docetaxel was associated with a higher frequency of PSA decline by more than 50% (6/10 vs 2/8 patients). A relationship was observed between sustained falls in CTCs counts and PSA declines by more than 50%. Conclusions: IGF-1R expression is detectable by immunofluorescence on CTCs. These data support the further evaluation of CTCs in pharmacodynamic studies and patient selection, particularly in advanced prostate cancer.

No significant financial relationships to disclose.

Circulating tumor cells (CTC) in newly diagnosed breast or colorectal cancers

14512

Background: The presence of CTCs is associated with poor prognosis in patients with metastatic carcinomas. The significance of CTCs at the time of diagnosis and after therapy is not known. A prospective clinical trial is conducted to determine if monitoring CTC levels in pts diagnosed with breast and colorectal cancer identify pts at risk for recurrence. CTCs are correlated with pathological stage as follow-up is too short to assess recurrence risk. Methods: Currently 213 pts with newly diagnosed breast and 119 pts with colorectal cancer before surgery with curative intend have been enrolled as well as a control group of 120 patients in whom diagnosis of breast or colorectal cancer was excluded. Thirty ml of blood was screened for the presence of CTCs at baseline before surgery and every following year using the CellSearch™ System. Results: Presence of CTCs in 30mL of blood in breast, colorectal cancer and the control group is provided in the table . In colorectal cancer the average number of CTCs /30 mL at baseline for Dukes A, B and C was 0.2, 0.7 and 1.1 respectively, for stage 0, I, II, III breast cancer 0.3, 0.5, 0.6 and 1.8 respectively and for the control group 0.24 CTCs /30 mL. Conclusions: CTC can be detected in a substantial proportion of pts before and after definitive surgery for breast and colorectal cancer. The number of CTCs before surgery correlated with the stage of the disease. Specificity of the CellSearch™ System is being increased to improve the discrimination of patients with benign and malignant disease. Follow-up must clarify whether the presence CTCs is an identifier for the risk of recurrence.

[Table: see text]

No significant financial relationships to disclose.

Changes in the growth properties of CD34+, CD38- bone marrow progenitors during human fetal development

We have previously described the isolation of separate populations of CD34+, CD38- stromal and hematopoietic progenitors cells within fetal bone marrow. The CD34+, CD38-, CD50+, HLA-DR+ population contained the majority of primitive hematopoietic progenitor cells, whereas stromal progenitors were contained within the CD34+, CD38-, CD50-, HLA-DR- population. In this study, we compared the frequencies and total numbers of clonogenic CD34+, CD38- stromal and hematopoietic cells as a function of fetal gestational age using single-cell fluorescent-activated cell sorting (FACS). At 14 weeks of gestation, 1/500 fetal bone marrow mononuclear cells were primitive hematopoietic CD34+, CD38-, HLA-DR+ progenitor cells, whereas 1/1,000 were stromal progenitors with the CD34+, CD38-, HLA-DR- phenotype. During fetal ontogeny there was a continuous, age-dependent decrease in the frequency of stromal progenitors, such that, at 24 weeks of gestation, only 1/100,000 of bone marrow cells had the CD34+, CD38-, HLA-DR- phenotype and were clonogenic stromal cells when isolated by FACS. In contrast, 1/250 bone marrow cells in a 24-week fetus had the CD34+, CD38-, HLA-DR+ phenotype and were clonogenic hematopoietic progenitors. The decrease in the frequency of stromal progenitors was a function of both a decreased frequency of cells with the CD34+, CD38-, HLA-DR- phenotype and a decrease in the growth potential of individual with this phenotype. The total numbers of mononuclear cells and the total numbers of hematopoietic progenitors in two fetal femurs increased in parallel, 100-fold, between 14 and 24 weeks of gestation. In contrast, the total numbers of clonogenic CD34+, CD38-, HLA-DR- stromal progenitor cells remained constant during this period. Although adult bone marrow samples contained stromal progenitor cells at a frequency of approximately 1/7,000 mononuclear cells, clonogenic stromal cells with the CD34+, CD38-, HLA-DR- phenotype could not be isolated by single-cell FACS from these samples. Thus, there are significant differences between the frequencies and biologic characteristics of stromal and hematopoietic stem cells during fetal and postnatal ontogeny.

The "common stem cell" hypothesis reevaluated: human fetal bone marrow contains separate populations of hematopoietic and stromal progenitors

There is a long-standing controversy as to whether a single bone marrow (BM)-derived cell can differentiate along both hematopoietic and stromal lineages. Both primitive hematopoietic and stromal progenitor cells in human BM express the CD34 antigen but lack expression of other surface markers, such as CD38. In this study we examined the CD34+, CD38- fraction of human fetal BM by multiparameter fluorescence-activated cell sorting (FACS) analysis and single-cell sorting. CD34+, C38- cells could be divided into HLA-DR+ and HLA-DR- fractions. After single-cell sorting, 59% of the HLA-DR+ cells formed hematopoietic colonies. In contrast, the CD34+, CD38-, HLA-DR- cells were much more heterogeneous with respect to their light scatter properties, expression of other hematopoietic markers (CD10, CD36, CD43, CD49b, CD49d, CD49e, CD50, CD62E, CD90w, CD105, and CD106), and growth properties. Single CD34+, CD38-, HLA-DR- cells sorted into individual culture wells formed either hematopoietic or stromal colonies. The presence or absence of CD50 (ICAM-3) expression distinguished hematopoietic from stromal progenitors within the CD34+, CD38-, HLA-DR- population. The CD50+ fraction had light scatter characteristics and growth properties of hematopoietic progenitor cells. In contrast, the CD50- fraction lacked hematopoietic progenitor activity but contained clonogenic stromal progenitors at a mean frequency of 5%. We tested the hypothesis that cultures derived from single cells with the CD34+, CD38-, HLA-DR- phenotype could differentiate along both a hematopoietic and stromal lineage. The cultures contained a variety of mesenchymal cell types and mononuclear cells that had the morphologic appearance of histiocytes. Immunophenotyping of cells from these cultures indicated a stromal rather than a hematopoietic origin. In addition, the growth of the histiocytic cells was independent of the presence or the absence of hematopoietic growth factors. Based on sorting more than 30,000 single cells with the CD34+, CD38-, HLA-DR- phenotype into individual culture wells, and an analysis of 864 stromal cultures initiated by single CD34+ BM cells, this study does not support the hypothesis of a single common progenitor for both hematopoietic and stromal lineages within human fetal BM.

Rapid selection of cell subpopulation-specific human monoclonal antibodies from a synthetic phage antibody library

Peripheral blood leukocytes incubated with a semisynthetic phage antibody library and fluorochrome-labeled CD3 and CD20 antibodies were used to isolate human single-chain Fv antibodies specific for subsets of blood leukocytes by flow cytometry. Isolated phage antibodies showed exclusive binding to the subpopulation used for selection or displayed additional binding to a restricted population of other cells in the mixture. At least two phage antibodies appeared to display hitherto-unknown staining patterns of B-lineage cells. This approach provides a subtractive procedure to rapidly obtain human antibodies against known and novel surface antigens in their native configuration, expressed on phenotypically defined subpopulations of cells. This approach does not depend on immunization procedures or the necessity to repeatedly construct phage antibody libraries.