Determination of 35 cell surface antigen levels in malignant pleural effusions identifies CD24 as a marker of disseminated tumor cells

The Complexities of Metastasis

Therapies that prevent metastatic dissemination and tumor growth in secondary organs are severely lacking. A better understanding of the mechanisms that drive metastasis will lead to improved therapies that increase patient survival. Within a tumor, cancer cells are equipped with different phenotypic and functional capacities that can impact their ability to complete the metastatic cascade. That phenotypic heterogeneity can be derived from a combination of factors, in which the genetic make-up, interaction with the environment, and ability of cells to adapt to evolving microenvironments and mechanical forces play a major role. In this review, we discuss the specific properties of those cancer cell subgroups and the mechanisms that confer or restrict their capacity to metastasize.

Multi-MHz laser-scanning single-cell fluorescence microscopy by spatiotemporally encoded virtual source array

Apart from the spatial resolution enhancement, scaling of temporal resolution, equivalently the imaging throughput, of fluorescence microscopy is of equal importance in advancing cell biology and clinical diagnostics. Yet, this attribute has mostly been overlooked because of the inherent speed limitation of existing imaging strategies. To address the challenge, we employ an all-optical laser-scanning mechanism, enabled by an array of reconfigurable spatiotemporally-encoded virtual sources, to demonstrate ultrafast fluorescence microscopy at line-scan rate as high as 8 MHz. We show that this technique enables high-throughput single-cell microfluidic fluorescence imaging at 75,000 cells/second and high-speed cellular 2D dynamical imaging at 3,000 frames per second, outperforming the state-of-the-art high-speed cameras and the gold-standard laser scanning strategies. Together with its wide compatibility to the existing imaging modalities, this technology could empower new forms of high-throughput and high-speed biological fluorescence microscopy that was once challenged.

Oncolytic adenovirus expressing bispecific antibody targets T-cell cytotoxicity in cancer biopsies

Oncolytic viruses exploit the cancer cell phenotype to complete their lytic life cycle, releasing progeny virus to infect nearby cells and repeat the process. We modified the oncolytic group B adenovirus EnAdenotucirev (EnAd) to express a bispecific single-chain antibody, secreted from infected tumour cells into the microenvironment. This bispecific T-cell engager (BiTE) binds to EpCAM on target cells and cross-links them to CD3 on T cells, leading to clustering and activation of both CD4 and CD8 T cells. BiTE transcription can be controlled by the virus major late promoter, limiting expression to cancer cells that are permissive for virus replication. This approach can potentiate the cytotoxicity of EnAd, and we demonstrate using primary pleural effusions and peritoneal malignant ascites that infection of cancer cells with the BiTE-expressing EnAd leads to activation of endogenous T cells to kill endogenous tumour cells despite the immunosuppressive environment. In this way, we have armed EnAd to combine both direct oncolysis and T cell-mediated killing, yielding a potent therapeutic that should be readily transferred into the clinic.

Engineering a high-affinity humanized anti-CD24 antibody to target hepatocellular carcinoma by a novel CDR grafting design

Cluster of differentiation 24 (CD24) is a specific surface marker involved in the tumorigenesis and progression of hepatocellular carcinoma (HCC). However, all reported anti-CD24 antibodies are murine ones with inevitable immunogenicity. To address this, a method using both molecular structure and docking-based complementarity determining region (CDR) grafting was employed for humanization. After xenogeneic CDR grafting into a human antibody, three types of canonical residues (in the VL/VH interface core, in the loop foundation, and interaction with loop residues) that support loop conformation and residues involved in the antigen-binding interface were back-mutated. Four engineered antibodies were produced, among which hG7-BM3 has virtually identical 3-D structure and affinity parameters with the parental chimeric antibody cG7. In vitro, hG7-BM3 demonstrated superior immunogenicity and serum stability to cG7. Antibody-dependent cellular cytotoxicity (ADCC), tumor cell internalization and in vivo targeting assays indicate that hG7-BM3 has the potential for development as an antibody-drug conjugate (ADC). We therefore generated the hG7-BM3-VcMMAE conjugate, which was shown to induce tumor cell apoptosis and effectively suppress nude mice bearing HCC xenografts. In conclusion, our study provides new inspiration for antibody humanization and an ADC candidate for laboratory study and clinical applications.

Malignant Nonhematological Effusion Characterization by Flow Cytometry

With the exception of hematological malignancies, flow cytometry (FC) is infrequently applied as an ancillary tool in the diagnosis of malignant effusions in most institutions. However, FC may be effectively used to differentiate between epithelial cells, mesothelial cells and leukocytes using antibodies against both cell surface and intracellular proteins, offering the advantage of quantitative analysis. Additionally, FC may be applied to the quantitative detection of cancer-associated molecules, including stem cell markers, as well as assessment of critical cellular processes, such as proliferation and apoptosis. Some of the latter tests may have relevance for monitoring treatment response in the presence of metastatic disease, although this does not constitute routine practice to date. This review summarizes current knowledge regarding the application of FC to serous effusions in the diagnostic setting, as well as in research into cancer biology focusing on clinical specimens. The studies published to date suggest a role for this method in the clinical setting in the context of diagnosis, prediction and prognosis.

Accumulation of ALDH1-positive cells after neoadjuvant chemotherapy predicts treatment resistance and prognosticates poor outcome in ovarian cancer

Although ovarian cancer is a highly chemosensitive disease, it is only infrequently cured. One of the major reasons lies in the presence of drug-resistant cancer stem-like cells, sufficient to fuel recurrence. We phenotyped cancer stem-like cells by flow cytometry and immunohistochemistry in 55 matched samples before and after taxane/platinum-based neoadjuvant chemotherapy. All used markers of stemness (ALDH1, CD24, CD117, CD133) isolated low frequencies of malignant cells. ALDH1 was the most valuable marker for tracking stemness in vivo. The enrichment of ALDH1 expression after treatment was associated with a poor response to chemotherapy, with platinum resistance and independently prognosticated unfavorable outcome. Our results suggest that increased ALDH1 expression after treatment identifies patients with aggressive tumor phenotypes.

Fibronectin Modulates Cell Adhesion and Signaling to Promote Single Cell Migration of Highly Invasive Oral Squamous Cell Carcinoma

Cell migration is regulated by adhesion to the extracellular matrix (ECM) through integrins and activation of small RhoGTPases, such as RhoA and Rac1, resulting in changes to actomyosin organization. During invasion, epithelial-derived tumor cells switch from laminin-enriched basal membrane to collagen and fibronectin-enriched connective tissue. How this switch affects the tumor migration is still unclear. We tested the hypothesis that ECM dictates the invasiveness of Oral Squamous Cell Carcinoma (OSCC). We analyzed the migratory properties of two OSCC lines, a low invasive cell line with high e-cadherin levels (L^inv/H^E-cad) or a highly invasive cell line with low e-cadherin levels (H^inv/L^E-cad), plated on different ECM components. Compared to laminin, fibronectin induced non-directional collective migration and decreased RhoA activity in L^inv/H^E-cad OSCC. For H^inv/L^E-cad OSCC, fibronectin increased Rac1 activity and induced smaller adhesions, resulting in a fast single cell migration in both 2D and 3D environments. Consistent with these observations, human OSCC biopsies exhibited similar changes in cell-ECM adhesion distribution at the invasive front of the tumor, where cells encounter fibronectin. Our results indicate that ECM composition might induce a switch from collective to single cell migration according to tumor invasiveness due to changes in cell-ECM adhesion and the resulting signaling pathways that alter actomyosin organization.

Squamous cell carcinoma of the oral cavity and circulating tumour cells

Due to a lack of substantial improvement in the outcome of patients suffering from oral squamous cell carcinoma (OSCC) during the past decades, current staging methods need to be revised. This disease is associated with poor survival rates despite considerable advances in diagnosis and treatment. The early detection of metastases is an important indicator of survival, prognosis and relapse. Therefore, a better understanding of the mechanisms underlying metastasis is crucial. Exploring alternative measures apart from common procedures is needed to identify new prognostic markers. Similar to previous findings predominantly for other solid tumours, recently published studies demonstrate that circulating tumour cells (CTCs) and disseminated tumour cells (DTCs) might serve as prognostic markers and could supplement routine staging in OSCC. Thus, the detection of CTCs/DTCs is a promising tool to determine the individual need for therapeutic intervention. Encouraging results and new approaches point to the future use of targeted therapies for OSCC, an exceedingly heterogeneous subgroup of head and neck cancer. This review focuses on summarising technologies currently used to detect CTCs/DTCs. The translational relevance for OSCC is highlighted. The inherent challenges in detecting CTCs/DTCs will be emphasised.

Tumor-propagating cells and Yap/Taz activity contribute to lung tumor progression and metastasis

Metastasis is the leading cause of morbidity for lung cancer patients. Here we demonstrate that murine tumor propagating cells (TPCs) with the markers Sca1 and CD24 are enriched for metastatic potential in orthotopic transplantation assays. CD24 knockdown decreased the metastatic potential of lung cancer cell lines resembling TPCs. In lung cancer patient data sets, metastatic spread and patient survival could be stratified with a murine lung TPC gene signature. The TPC signature was enriched for genes in the Hippo signaling pathway. Knockdown of the Hippo mediators Yap1 or Taz decreased in vitro cellular migration and transplantation of metastatic disease. Furthermore, constitutively active Yap was sufficient to drive lung tumor progression in vivo. These results demonstrate functional roles for two different pathways, CD24-dependent and Yap/Taz-dependent pathways, in lung tumor propagation and metastasis. This study demonstrates the utility of TPCs for identifying molecules contributing to metastatic lung cancer, potentially enabling the therapeutic targeting of this devastating disease.

Advances and critical concerns with the microfluidic enrichments of circulating tumor cells

Over the past two decades, circulating tumor cells (CTCs) have been widely recognized for their importance in clinical trials. While most enrichment methods for these cells have been conducted through the batch process due to their rarity in blood and the need for large sample volumes, the batch process leads to unavoidable cell loss. Given the heterogenetic features of CTCs, this cell loss may limit the validity of research that relies on the isolation of CTCs; such research includes cancer prognosis, diagnosis of minimal residual diseases, assessment of tumor sensitivity to anticancer drugs, and the personalization of anticancer therapies. Recent advances in microfluidic approaches have made it possible to enrich CTCs with a small degree of cell loss. In this review, we highlight several microfluidic-based positive and negative enrichment methods that are the subject of considerable research interest (e.g. EpCAM-dependent assay and EpCAM-independent assay) and suggest a microfluidic-based single cell analysis platform for the down-stream analysis of CTCs. We also discuss critical concerns and future directions for research.