Quantifying the Morphology and Mechanisms of Cancer Progression in 3D in-vitro environments: Integrating Experiments, Multiscale Models, and Spatial Validation

Throughout the years, mathematical models of cancer growth have become increasingly more accurate in terms of the description of cancer growth in both space and time. However, the limited amount of data typically available has resulted in a larger number of qualitative rather than quantitative studies. In this study, we provide an integrated experimental-computational framework for the quantification of the morphological characteristics and the mechanistic modelling of cancer progression in 3D environments. The proposed framework allows the calibration of multiscale-spatiotemporal models of cancer growth using 3D cell culture data, and their validation based on the morphological patterns. The implementation of this framework enables us to pursue two goals; first, the quantitative description of the morphology of cancer progression in 3D cultures, and second, the relation of tumour morphology with underlying biophysical mechanisms that govern cancer growth. We apply this framework to the study of the spatiotemporal progression of Triple Negative Breast Cancer (TNBC) cells cultured in 3D Matrigel scaffolds, under the hypothesis of chemotactic migration using a multiscale Keller-Segel model. The results reveal transient, non-random spatial distributions of cancer cells that consist of clustered patterns across a wide range of neighbourhood distances, as well as dispersion for larger distances. Overall, the proposed model was able to describe the general characteristics of the experimental observations and suggests that cancer cells exhibited chemotactic migration and cell accumulation, as well as random motion throughout the period of development. To our knowledge, this is the first time a framework attempts to quantify the relationship of the spatial patterns and the underlying mechanisms of cancer growth in 3D environments.

A Pillar-Free Diffusion Device for Studying Chemotaxis on Supported Lipid Bilayers

Chemotactic cell migration plays a crucial role in physiological and pathophysiological processes. In tissues, cells can migrate not only through extracellular matrix (ECM), but also along stromal cell surfaces via membrane-bound receptor–ligand interactions to fulfill critical functions. However, there remains a lack of models recapitulating chemotactic migration mediated through membrane-bound interactions. Here, using micro-milling, we engineered a multichannel diffusion device that incorporates a chemoattractant gradient and a supported lipid bilayer (SLB) tethered with membrane-bound factors that mimics stromal cell membranes. The chemoattractant channels are separated by hydrogel barriers from SLB in the cell loading channel, which enable precise control of timing and profile of the chemokine gradients applied on cells interacting with SLB. The hydrogel barriers are formed in pillar-free channels through a liquid pinning process, which eliminates complex cleanroom-based fabrications and distortion of chemoattractant gradient by pillars in typical microfluidic hydrogel barrier designs. As a proof-of-concept, we formed an SLB tethered with ICAM-1, and demonstrated its lateral mobility and different migratory behavior of Jurkat T cells on it from those on immobilized ICAM-1, under a gradient of chemokine CXCL12. Our platform can thus be widely used to investigate membrane-bound chemotaxis such as in cancer, immune, and stem cells.

The Only Chemoreceptor Encoded by che Operon Affects the Chemotactic Response of Agrobacterium to Various Chemoeffectors

Chemoreceptor (also called methyl-accepting chemotaxis protein, MCP) is the leading signal protein in the chemotaxis signaling pathway. MCP senses and binds chemoeffectors, specifically, and transmits the sensed signal to downstream proteins of the chemotaxis signaling system. The genome of Agrobacterium fabrum (previously, tumefaciens) C58 predicts that a total of 20 genes can encode MCP, but only the MCP-encoding gene atu0514 is located inside the che operon. Hence, the identification of the exact function of atu0514-encoding chemoreceptor (here, named as MCP514) will be very important for us to understand more deeply the chemotaxis signal transduction mechanism of A. fabrum. The deletion of atu0514 significantly decreased the chemotactic migration of A. fabrum in a swim plate. The test of atu0514-deletion mutant (Δ514) chemotaxis toward single chemicals showed that the deficiency of MCP514 significantly weakened the chemotactic response of A. fabrum to four various chemicals, sucrose, valine, citric acid and acetosyringone (AS), but did not completely abolish the chemotactic response. MCP514 was localized at cell poles although it lacks a transmembrane (TM) region and is predicted to be a cytoplasmic chemoreceptor. The replacement of residue Phe328 showed that the helical structure in the hairpin subdomain of MCP514 is a direct determinant for the cellular localization of MCP514. Single respective replacements of key residues indicated that residues Asn336 and Val353 play a key role in maintaining the chemotactic function of MCP514.

G-Protein coupled Purinergic P2Y12 receptor interacts and internalizes TauRD-mediated by membrane-associated actin cytoskeleton remodelling in microglia

In Alzheimers disease, the microtubule-associated protein, Tau misfolds to form aggregates and filaments in the intra- and extracellular region of neuronal cells. Microglial cells are the resident brain macrophage cells that are involved in constant surveillance and are activated by the extracellular deposits. Purinergic receptors are involved in chemotactic migration of microglial cells towards the site of inflammation. In our recent study, we found that microglial P2Y12 receptor has been involved in phagocytosis of full-length Tau species such as monomers, oligomers and aggregates by actin-driven chemotaxis. In this study, we have showed the interaction of repeat-domain of Tau (TauRD) with microglial P2Y12 receptor and analysed the corresponding residues for interaction by various in-silico approaches. In cellular studies, TauRD was found to interact with microglial P2Y12R and induces its cellular expression as confirmed by co-immunoprecipitation and western blot analysis respectively. Similarly, immunofluorescence microscopic studies emphasized that TauRD were phagocytosed by microglial P2Y12R via the membrane-associated actin remodelling as filopodia extension. Furthermore, the P2Y12R-mediated TauRD internalization has activated the microglia with an increase in the Iba1 level and TauRD become accumulated at peri-nuclear region as localized with Iba1. Altogether, microglial P2Y12R interacts with TauRD and mediates directed migration and activation for its internalization.

Antisense oligonucleotide p45Skp-2 suppresses migratory chemotactic and metastasis of oral malignant Burkitt’s lymphoma cell through down-regulation of MTA-1 and induction of E-cadherin mechanism

Introduction: Burkitt’s lymphoma is a high-grade B-cell neoplasm and one of the most aggressive malignancies of lymphoid origins which found mainly in the paediatric population. The treatment options of this tumour are still limited. However, a new strategy for refractory tumour, phosphorothioate oligonucleotide antisense technique has watched with keen interest. This study was aimed to examine the effect of antisense p45Skp-2 (Skp-2 AS) suppressed migratory chemotactic and metastasis of oral malignant Burkitt’s lymphoma (Raji) cell through down-regulation of MTA-1 and E-cadherin. Methods: True experiment laboratory with post-test control group design was confirmed in this study. The efficiency of Skp-2 AS in the suppression of cell chemotactic migration was examined by Boyden chamber assay. To evaluate the inhibition of cell metastasis was conducted by decreasing MTA-1 expression protein. The expressions of MTA-1, E-cadherin and α-tubulin protein were investigated by Western blot analysis. Results: The results revealed that the number of chemotactic migration of Skp-2 AS treated Raji cell was significantly decreased when compared with that of sense p45Skp-2 (Skp-2 S) and scrambled control (SC) cells (P<0.05) followed by decreased expressions of MTA-1 protein and overexpression of E-cadherin. Interestingly, the expression of α-tubulin protein as an internal control was approximately similar in each transfectant cells. Conclusion: p45Skp-2 have an antitumor activity via suppression of migratory chemotactic activity and metastasis on oral Burkitt’s lymphoma cells through down-regulation of MTA-1 and induction of E-cadherin proteins targeting this molecule could represent a promising new therapeutic approach for this type of cancer.

EBV-EBNA1 constructs an immunosuppressive microenvironment for nasopharyngeal carcinoma by promoting the chemoattraction of Treg cells

BackgroundNasopharyngeal carcinoma (NPC) is primarily caused by the Epstein-Barr virus (EBV) infection in NPC endemic areas. EBNA1 is an EBV-encoded nuclear antigen, which plays a critical role in the maintenance and replication of EBV genome. However, the mechanisms of EBNA1-promoted NPC immune escape are unknown. Regulatory T (Treg) cells are among the key regulators in restraining antitumor responses. However, the mechanisms of accumulation of Treg cells in NPC have not been defined. This study attempted to identify the detailed mechanisms of EBNA1 functions as a tumor accelerator to promote NPC immune escape by enhancing chemoattraction of Treg cells.MethodsmRNA profiles were determined by next-generation sequencing in NPC cells. In vitro and in vivo assays were performed to analyze the role of EBNA1 in regulation of recruitment of Treg cells. Colocation and coimmunoprecipitation analyzes were used to identify the SMAD3/c-JUN complex. Chromatin immunoprecipitation assay and dual luciferase reporter assays were designed to demonstrate c-JUN binding to miR-200a promoter and miR-200a targeting to CXCL12 3’Untranslated Regions. The hepatocellular carcinoma models were designed to demonstrate universality of the CXCL12-CXCR4-Treg axis in promoting immune evasion of various tumors.ResultA novel molecular mechanism was identified that involves EBV-EBNA1-stimulated chemotactic migration of Treg cells toward NPC microenvironment by upregulation of the transforming growth factor-β1 (TGFβ1)-SMAD3-PI3K-AKT-c-JUN-CXCL12-CXCR4 axis and downregulation of miR-200a. EBV-EBNA1 promotes the chemoattraction of Treg cells by governing the protein–protein interactions of the SMAD3/c-JUN complex in a TGFβ1-dependent manner in vitro and in vivo. TGFβ1 suppresses miR-200a by enhancing the SMAD3/c-JUN complex. miR-200a negatively regulates the CXCL12 chemokine by direct targeting of the CXCL12 3’UTR region. However, CXCL12 acts as the target gene of miR-200a and as an inhibitor of miR-200a transcription, and inhibition of miR-200a by CXCL12 is mediated by c-JUN, which directly binds to the miR-200a promoter and forms a c-JUN-miR-200a-CXCL12-c-JUN feedback loop. In addition, enhanced CXCL12 efficiently attracts CXCR4-positive Treg cells to remodel an immunosuppressive microenvironment.ConclusionsEBV-EBNA1 promotes chemotactic migration of Treg cells via the TGFβ1-SMAD3-PI3K-AKT-c-JUN-miR-200a-CXCL12-CXCR4 axis in the NPC microenvironment. These results suggest that EBV-EBNA1 may serve as a potential therapeutic target to reshape the NPC microenvironment.

Chemotactic Migration of Bacteria in Porous Media

Chemotactic migration of bacteria—their ability to direct multicellular motion along chemical gradients—is central to processes in agriculture, the environment, and medicine. However, studies are typically performed in homogeneous media, despite the fact that many bacteria inhabit heterogeneous porous media such as soils, sediments, and biological gels. Here, we directly visualize the migration of Escherichia coli populations in 3D porous media. We find that pore-scale confinement is a strong regulator of chemotactic migration. Strikingly, cells use a different primary mechanism to direct their motion in confinement than in bulk liquid. Further, confinement markedly alters the dynamics and morphology of the migrating population—features that can be described by a continuum model, but only when standard motility parameters are substantially altered from their bulk liquid values. Our work thus provides a framework to predict and control the migration of bacteria, and active matter in general, in heterogeneous environments.Statement of SignificanceTypical studies of bacterial motility focus on cells in homogeneous media; however, many bacteria inhabit tight porous media such as soils, sediments, and biological gels. This paper demonstrates how confinement in a porous medium fundamentally alters the chemotactic migration of Escherichia coli. We find that cells use a different primary mechanism to direct their motion in confinement than in bulk liquid. Further, confinement markedly alters the overall dynamics and morphology of a migrating population—features that can be described by a continuum model, but only when standard motility parameters are substantially altered from their bulk liquid values. This work thus provides a framework to predict and control the migration of bacteria, and active matter in general, in heterogeneous porous environments.