Impedimetric quantification of migration speed of cancer cells migrating along a Matrigel-filled microchannel

Investigation of Stem Cell-Like Characteristics and Immune Cell Interaction of Tumor Cells Survived from Continuous Shear Flow Environment

When tumor cells are released from a primary tumor into the bloodstream or lymphatic circulation system, they are exposed to a continuous shear flow environment. This environment exerts physical stresses on the tumor cells, which can activate apoptotic pathways. However, certain tumor cells have the ability to adapt to these mechanical stresses, enhancing their likelihood of survival and promoting metastasis. In this study, these tumor cells survived from shear flow environment are examined and revealed to closely link to stem cell-like characteristics. Higher gene expression levels of self-renewal and differentiation markers and enhanced abilities of migration, spheroid formation, and colony formation are shown. Moreover, the interaction between immune cells and the surviving cells is investigated. The results show that the surviving cells possess immune escape capabilities, implying their ability to evade immune surveillance. Additionally, these surviving cells display characteristics reminiscent of stem cells. This study holds great importance in advancing the understanding of tumor biology. By comprehending the behavior and properties of these surviving cells, new therapeutic strategies can be developed to specifically target circulating tumor cells (CTCs) and enhance cancer treatment outcomes.

A machine learning based approach for quantitative evaluation of cell migration in Transwell assays based on deformation characteristics

Many pathological and physiological processes, including embryonic development, immune response and cancer metastasis, involve studies on cell migration, and especially detection methods, for which it is difficult to satisfy the requirements for rapid and quantitative evaluation and analysis. In view of the shortcomings in simultaneously quantifying the number of migrated cells and non-migrated cells using Transwell assays, we propose a novelty approach for the evaluation of cell migration by distinguishing whether the cells have migrated based on the regularity of the cell morphology changes. Traditionally, the status of living cells and dead cells are detected and analyzed by machine learning using some common morphological characteristics, e.g., area and perimeter of the cells. However, the accuracy of detecting whether cells have migrated or not using these common characteristics is not high, and the characteristics are not appropriate for our studies. Therefore, from the point of view of mechanism analysis for the migration behavior, we examined the regularity of different morphology changes of migrated cells and non-migrated cells, and thus discovered the distinguishable morphological characteristics. Then, two deformation characteristics, deformation index and taper index are proposed. Then, a machine learning based algorithm that can identify migrated cells according to the proposed deformation characteristics was devised. In addition, images of migrated cells and non-migrated cells were obtained from the Transwell assays. This algorithm was trained, and was able to successfully identify migrated cells with an accuracy of 84% using the proposed morphological characteristics. This method greatly improves the identification accuracy when compared with the identification of traditional characteristics of which the accuracy was about 54.7%. This machine learning based method might be employed as a potential tool for cell counting and evaluation of cell migration with the aim of reducing time and improving automation compared with the traditional method. This method is effective, rapid, and incorporate advances in artificial intelligence which could be used for adapting the current evaluation methods.

A Review on Microfluidics-Based Impedance Biosensors

Electrical impedance biosensors are powerful and continuously being developed for various biological sensing applications. In this line, the sensitivity of impedance biosensors embedded with microfluidic technologies, such as sheath flow focusing, dielectrophoretic focusing, and interdigitated electrode arrays, can still be greatly improved. In particular, reagent consumption reduction and analysis time-shortening features can highly increase the analytical capabilities of such biosensors. Moreover, the reliability and efficiency of analyses are benefited by microfluidics-enabled automation. Through the use of mature microfluidic technology, complicated biological processes can be shrunk and integrated into a single microfluidic system (e.g., lab-on-a-chip or micro-total analysis systems). By incorporating electrical impedance biosensors, hand-held and bench-top microfluidic systems can be easily developed and operated by personnel without professional training. Furthermore, the impedance spectrum provides broad information regarding cell size, membrane capacitance, cytoplasmic conductivity, and cytoplasmic permittivity without the need for fluorescent labeling, magnetic modifications, or other cellular treatments. In this review article, a comprehensive summary of microfluidics-based impedance biosensors is presented. The structure of this article is based on the different substrate material categorizations. Moreover, the development trend of microfluidics-based impedance biosensors is discussed, along with difficulties and challenges that may be encountered in the future.

Cell marathon: long-distance cell migration and metastasis-associated gene analysis using a folding paper system

A high mortality rate was found in cancer patients with distant metastasis. Development of targeted drugs for effectively inhibiting cancer metastasis is the key for increasing therapeutic success. In the current study, a folding paper system was developed to mimic a tumor-vascular interface for the study of long-distance cell migration. Correlation between the cell migration distance and metastasis-associated gene was successfully analyzed by disassembling the stacked paper construct. The result revealed that the migration distance and number of migrated cells were highly correlated to cell characteristics. Moreover, immunocytochemistry was directly conducted on the paper layer to study the signaling pathway. Kelch-like and protein tyrosine phosphatase families were examined and the PTPN13 gene was shown to regulate long-distance cell migration. By analyzing the phosphorylated mTOR, the PTPN13 gene was further confirmed to be a tumor suppressor gene that inhibits long-distance cell migration. The folding paper system provides an alternative approach for long-distance cell migration. Metastasis-associated gene expression can be analyzed to potentially develop targeted drugs for cancer metastasis inhibition.

Analysis of the Internal Hypoxic Environment in Solid Tumor Tissue Using a Folding Paper System

Hypoxia is a nonphysiological oxygen tension which is common in most malignant tumors. Hypoxia stimulates complicated cell signaling networks in cancer cells, e.g., the HIF, PI3K, MAPK, and NFκB pathways. Then, cells release a number of cytokines such as VEGFA to promote the growth of peripheral blood vessels and lead to metastasis. In the current work, understanding of the internal hypoxic environment in solid tumor tissue was attempted by developing a folding paper system. A paper-based solid tumor was constructed by folding a filter paper cultured with cancer cells. The cellular response in each layer could be analyzed by disassembling the folded paper after the culture course. The result showed that an internal hypoxic environment was successfully reproduced in the paper-based solid tumor. The cells in the inner layer expressed high levels of HIF1-α and VEGFA. Hence, proliferation and migration of endothelial cells were shown to be induced by the cells located in the internal hypoxic environment. Moreover, the paper-based solid tumor was transplanted into nude mice for the study of hypoxic response and angiogenesis. The crosstalk between internal and external parts of solid tumor tissue could be analyzed by sectioning each layer of the paper-based solid tumor. This approach provides a favorable analytical method for the discovery of the interaction between cancer cells, hypoxia, and peripheral angiogenesis.

Characterization of stem cell-like property in cancer cells based on single-cell impedance measurement in a microfluidic platform

Investigation of stem cell-like property in cancer cells is important for the development of new therapeutic drugs targeting at malignant tumors. Currently, the standard approach for identifying cancer stem cell-like cells relies on the recognition of stem cell surface markers. However, the reliability remains controversial among biologists. In the current work, a dielectrophoretic and impedimetric hybrid microfluidic platform was developed for capturing single cells and characterizing their stem cell-like property. Single cells were captured in 20 μm trapping wells by dielectrophoretic force and their impedance spectra were measured by an impedance analyzer. The result showed that different cancer cell lines could be differentiated by impedance magnitude ranging between 2 and 20 kHz. Moreover, cancer cells and cancer stem cell-like cells could be categorized by a 2-dimensional graph of the impedance magnitudes at 2 and 20 kHz. The stem cell-like property in cancer cells was verified by stem cell surface markers and single-cell derived colony assay. Comparing with bio-chemical approach, i.e., surface markers, bio-physical approach, i.e., cell impedance, is a label-free technique to identify cancer stem cell-like cells.