Tumor spheroids accelerate persistently invading cancer cells

Advancing in vitro cell migration studies: a review of open-source analytical platforms for cancer and wound healing research

A single cell or cell population exhibits the fundamental phenomenon of cell migration during developmental processes or disease progression. Vast literature suggests that, in vitro 2-dimensional or 3-dimensional cell migration assay is one of the most commonly used assays in cancer, wound healing research, and developmental biology research. The data obtained from this assay are often analyzed using various proprietary or open-source programs. Proprietary software are costly and not always accessible to everyone. Whereas the open-source programs are free, easy to access, and user friendly. However, not all researchers are aware of these open-source programs. Despite the increasing availability of these programs, many researchers still rely on proprietary software, due to a lack of comparative analyses and practical guidance on their implementation. Hence, this review aims to provide insights into these open-source tools and serves as a practical guide to both biologists and computational researchers for their specific analytical needs.

Tumor invasiveness is regulated by the concerted function of APC, formins, and Arp2/3 complex

Tumor cell invasion is the initial step in metastasis, the leading cause of death from cancer. Invasion requires protrusive cellular structures that steer the migration of leader cells emanating from the tumor mass toward neighboring tissues. Actin is central to these processes and is therefore the prime target of drugs known as migrastatics. However, the broad effects of general actin inhibitors limit their therapeutic use. Here, we delineate the roles of specific actin nucleators in tuning actin-rich invasive protrusions and pinpoint potential pharmacological targets. We subject colorectal cancer spheroids embedded in collagen matrix-a preclinical model mirroring solid tumor invasiveness-to pharmacologic and/or genetic treatment of specific actin arrays to assess their roles in invasiveness. Our data reveal coordinated yet distinct involvement of actin networks nucleated by adenomatous polyposis coli, formins, and actin-related protein 2/3 complex in the biogenesis and maintenance of invasive protrusions. These findings may open avenues for better targeted therapies.

In Vitro Tumor Mimetic Spheroid Model: Void Space within a Self-Detachable Cross-Linked Hydrogel

The three-dimensional (3D) spheroid cell culture model is crucial in screening anticancer drugs in vitro and understanding tumor cell behavior. However, the current in vitro models require highly skilled techniques. Here, we present an in vitro, tumor-mimetic, self-detachable, cancer cell spheroid model that provides the confined space of a tumor microenvironment, convenient spheroid retrieval, immunostaining, treatment, and imaging. We formed a void space within alginate macrobeads by ionic disintegration at a specific region inside. The macrobeads were further destabilized with bovine serum albumin to retrieve the spheroid cultured within the void space. Quantitative analysis of the immunofluorescence images of the cultured spheroids showed enhanced expressions of the hypoxia-inducible factor-1α (HIF-1α) and carbonic anhydrase-9 (CA-9), like monolayer cultures of cancer cells under hypoxic conditions (0.2% oxygen). Furthermore, adding CoCl2 to the cell culture media induces even higher amounts of HIF-1α and CA-9 in the cultured spheroids. In conclusion, the present work highlighted the in vitro spheroid model, which is closer to the tumor microenvironment and has user-friendly cell seeding, spheroid retrieval, and immunostaining steps.

Anomalous diffusion, nonergodicity, non-Gaussianity, and aging of fractional Brownian motion with nonlinear clocks

How do nonlinear clocks in time and/or space affect the fundamental properties of a stochastic process? Specifically, how precisely may ergodic processes such as fractional Brownian motion (FBM) acquire predictable nonergodic and aging features being subjected to such conditions? We address these questions in the current study. To describe different types of non-Brownian motion of particles-including power-law anomalous, ultraslow or logarithmic, as well as superfast or exponential diffusion-we here develop and analyze a generalized stochastic process of scaled-fractional Brownian motion (SFBM). The time- and space-SFBM processes are, respectively, constructed based on FBM running with nonlinear time and space clocks. The fundamental statistical characteristics such as non-Gaussianity of particle displacements, nonergodicity, as well as aging are quantified for time- and space-SFBM by selecting different clocks. The latter parametrize power-law anomalous, ultraslow, and superfast diffusion. The results of our computer simulations are fully consistent with the analytical predictions for several functional forms of clocks. We thoroughly examine the behaviors of the probability-density function, the mean-squared displacement, the time-averaged mean-squared displacement, as well as the aging factor. Our results are applicable for rationalizing the impact of nonlinear time and space properties superimposed onto the FBM-type dynamics. SFBM offers a general framework for a universal and more precise model-based description of anomalous, nonergodic, non-Gaussian, and aging diffusion in single-molecule-tracking observations.

3D printed inserts for reproducible high throughput screening of cell migration

Cell migration is a fundamental and complex phenomenon that occurs in normal physiology and in diseases like cancer. Hence, understanding cell migration is very important in the fields of developmental biology and biomedical sciences. Cell migration occurs in 3 dimensions (3D) and involves an interplay of migrating cell(s), neighboring cells, extracellular matrix, and signaling molecules. To understand this phenomenon, most of the currently available techniques still rely on 2-dimensional (2D) cell migration assay, also known as the scratch assay or the wound healing assay. These methods suffer from limited reproducibility in creating a cell-free region (a scratch or a wound). Mechanical/heat related stress to cells is another issue which hampers the applicability of these methods. To tackle these problems, we developed an alternative method based on 3D printed biocompatible cell inserts, for quantifying cell migration in 24-well plates. The inserts were successfully validated via a high throughput assay for following migration of lung cancer cell line (A549 cell line) in the presence of standard cell migration promoters and inhibitors. We also developed an accompanying image analysis pipeline which demonstrated that our method outperforms the state-of-the-art methodologies for assessing the cell migration in terms of reproducibility and simplicity.

Cancer Spheroids and Organoids as Novel Tools for Research and Therapy: State of the Art and Challenges to Guide Precision Medicine

Spheroids and organoids are important novel players in medical and life science research. They are gradually replacing two-dimensional (2D) cell cultures. Indeed, three-dimensional (3D) cultures are closer to the in vivo reality and open promising perspectives for academic research, drug screening, and personalized medicine. A large variety of cells and tissues, including tumor cells, can be the starting material for the generation of 3D cultures, including primary tissues, stem cells, or cell lines. A panoply of methods has been developed to generate 3D structures, including spontaneous or forced cell aggregation, air-liquid interface conditions, low cell attachment supports, magnetic levitation, and scaffold-based technologies. The choice of the most appropriate method depends on (i) the origin of the tissue, (ii) the presence or absence of a disease, and (iii) the intended application. This review summarizes methods and approaches for the generation of cancer spheroids and organoids, including their advantages and limitations. We also highlight some of the challenges and unresolved issues in the field of cancer spheroids and organoids, and discuss possible therapeutic applications.