Collective tumor cell migration in the presence of fibroblasts

A mixture-like model for tumor-immune system interactions

We introduce a mathematical model based on mixture theory intended to describe the tumor-immune system interactions within the tumor microenvironment. The equations account for the geometry of the tumor expansion, and the displacement of the immune cells, driven by diffusion and chemotactic mechanisms. They also take into account the constraints in terms of nutrient and oxygen supply. The numerical investigations analyze the impact of the different modeling assumptions and parameters. Depending on the parameters, the model can reproduce elimination, equilibrium or escape phases and it identifies a critical role of oxygen/nutrient supply in shaping the tumor growth. In addition, antitumor immune cells are key factors in controlling tumor growth, maintaining an equilibrium while protumor cells favor escape and tumor expansion.

Cancer-Associated Fibroblasts: Master Tumor Microenvironment Modifiers

Cancer cells rely on the tumor microenvironment (TME), a composite of non-malignant cells, and extracellular matrix (ECM), for survival, growth, and metastasis. The ECM contributes to the biomechanical properties of the surrounding tissue, in addition to providing signals for tissue development. Cancer-associated fibroblasts (CAFs) are stromal cells in the TME that are integral to cancer progression. Subtypes of CAFs across a variety of cancers have been revealed, and each play a different role in cancer progression or suppression. CAFs secrete signaling molecules and remodel the surrounding ECM by depositing its constituents as well as degrading enzymes. In cancer, a remodeled ECM can lead to tumor-promoting effects. Not only does the remodeled ECM promote growth and allow for easier metastasis, but it can also modulate the immune system. A better understanding of how CAFs remodel the ECM will likely yield novel therapeutic targets. In this review, we summarize the key factors secreted by CAFs that facilitate tumor progression, ECM remodeling, and immune suppression.

Mg-based materials diminish tumor spreading and cancer metastases

Cancer metastases are the most common causes of cancer-related deaths. The formation of secondary tumors at different sites in the human body can impair multiple organ function and dramatically decrease the survival of the patients. In this stage, it is difficulty to treat tumor growth and spreading due to arising therapy resistances. Therefore, it is important to prevent cancer metastases and to increase subsequent cancer therapy success. Cancer metastases are conventionally treated with radiation or chemotherapy. However, these treatments elicit lots of side effects, wherefore novel local treatment approaches are currently discussed. Recent studies already showed anticancer activity of specially designed degradable magnesium (Mg) alloys by reducing the cancer cell proliferation. In this work, we investigated the impact of these Mg-based materials on different steps of the metastatic cascade including cancer cell migration, invasion, and cancer-induced angiogenesis. Both, Mg and Mg–6Ag reduced cell migration and invasion of osteosarcoma cells in coculture with fibroblasts. Furthermore, the Mg-based materials used in this study diminished the cancer-induced angiogenesis. Endothelial cells incubated with conditioned media obtained from these Mg and Mg–6Ag showed a reduced cell layer permeability, a reduced proliferation and inhibited cell migration. The tube formation as a last step of angiogenesis was stimulated with the presence of Mg under normoxia and diminished under hypoxia.

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Magnesium (Mg)-based material degradation decrease cell migration and invasion of an osteosarcoma coculture.

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Mg-based material degradation products reduce cancer-induced angiogenesis at an early stage.

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These materials may reduce secondary tumor formation and metastases.

Melanoma cells with diverse invasive potential differentially induce the activation of normal human fibroblasts

Background

The tumor microenvironment consists of stromal cells, extracellular matrix, and physicochemical properties (e.g., oxygenation, acidification). An important element of the tumor niche are cancer-associated fibroblasts (CAFs). They may constitute up to 80% of the tumor mass and share some features with myofibroblasts involved in the process of wound healing. CAFs can facilitate cancer progression. However, their interaction with melanoma cells is still poorly understood.

Methods

We obtained CAFs using conditioned media derived from primary and metastatic melanoma cells, and via co-culture with melanoma cells on Transwell inserts. Using 2D and 3D wound healing assays and Transwell invasion method we evaluated CAFs’ motile activities, while coverslips with FITC-labeled gelatin, gelatin zymography, and fluorescence-based activity assay were employed to determine the proteolytic activity of the examined cells. Western Blotting method was used for the identification of CAFs’ markers as well as estimation of the mediators of MMPs’ (matrix metalloproteinases) expression levels. Lastly, CAFs’ secretome was evaluated with cytokine and angiogenesis proteomic arrays, and lactate chemiluminescence-based assay.

Results

Acquired FAP-α/IL6-positive CAFs exhibited elevated motility expressed as increased migration and invasion ratio, as well as higher proteolytic activity (area of digestion, MMP2, MMP14). Furthermore, fibroblasts activated by melanoma cells showed upregulation of the MMPs’ expression mediators’ levels (pERK, p-p38, CD44, RUNX), enhanced secretion of lactate, several cytokines (IL8, IL6, CXCL1, CCL2, ICAM1), and proteins related to angiogenesis (GM-CSF, DPPIV, VEGFA, PIGF).

Conclusions

Observed changes in CAFs’ biology were mainly driven by highly aggressive melanoma cells (A375, WM9, Hs294T) compared to the less aggressive WM1341D cells and could promote melanoma invasion, as well as impact inflammation, angiogenesis, and acidification of the tumor niche. Interestingly, different approaches to CAFs acquisition seem to complement each other showing interactions between studied cells.

Studying Activated Fibroblast Phenotypes and Fibrosis-Linked Mechanosensing Using 3D Biomimetic Models

Fibrosis and solid tumor progression are closely related, with both involving pathways associated with chronic wound dysregulation. Fibroblasts contribute to extracellular matrix (ECM) remodeling in these processes, a crucial step in scarring, organ failure, and tumor growth, but little is known about the biophysical evolution of remodeling regulation during the development and progression of matrix-related diseases including fibrosis and cancer. A 3D collagen-based scaffold model is employed here to mimic mechanical changes in normal (2 kPa, soft) versus advanced pathological (12 kPa, stiff) tissues. Activated fibroblasts grown on stiff scaffolds show lower migration and increased cell circularity compared to those on soft scaffolds. This is reflected in gene expression profiles, with cells cultured on stiff scaffolds showing upregulated DNA replication, DNA repair, and chromosome organization gene clusters, and a concomitant loss of ability to remodel and deposit ECM. Soft scaffolds can reproduce biophysically meaningful microenvironments to investigate early stage processes in wound healing and tumor niche formation, while stiff scaffolds can mimic advanced fibrotic and cancer stages. These results establish the need for tunable, affordable 3D scaffolds as platforms for aberrant stroma research and reveal the contribution of physiological and pathological microenvironment biomechanics to gene expression changes in the stromal compartment.

In silico investigations of intratumoral heterogeneous interstitial fluid pressure

Recent preclinical studies have shown that interstitial fluid pressure (IFP) within tumors can be heterogeneous Andersen et al. (2019). In that study tumors of two xenograft models, respectively, HL-16 cervical carcinoma and Panc-1 pancreatic carcinoma, were investigated. Significant heterogeneity in IFP was reported and it was proposed that this was associated with division of tissue into compartments separated by thick connective tissue bands for the HL-16 tumors and with dense collagen-rich extracellular matrix for the Panc-1 tumors. The purpose of the current work is to explore these experimental observations by using in silico generated tumor models. We consider a mathematical multiphase model which accounts for tumor cells, fibroblasts and interstitial fluid. The model has been trained to comply with experimental in vitro results reported in Shieh et al. (2011) which has identified autologous chemotaxis, ECM remodeling, and cell-fibroblast interaction as drivers for invasive tumor cell behavior. The in silico model is informed with parameters that characterize the leaky intratumoral vascular network, the peritumoral lymphatics which collect the fluid, and the density of ECM as represented through the hydraulic conductivity of the interstitial space. Heterogeneous distribution of solid stress may result in heterogeneous compression of blood vessels and, thus, heterogeneous vascular density inside the tumor. To mimic this we expose the in silico tumor to an intratumoral vasculature whose net effect of density of blood vesssels and vessel wall conductivity is varied through a 2D Gaussian variogram constrained such that the resulting IFPs lie within the range as reported from the preclinical study. The in silico cervical carcinoma model illustrates that sparse ECM was associated with uniform intratumoral IFP in spite of heterogeneous microvascular network, whereas compartment structures resulted in more heterogeneous IFP. Similarly, the in silico pancreatic model shows that heterogeneity in the microvascular network combined with dense ECM structure prevents IFP to even out and gives rise to heterogeneous IFP. The computer model illustrates how a heterogeneous invasive front might form where groups of tumor cells detach from the primary tumor and form isolated islands, a behavior which is natural to associate with metastatic propensity. However, unlike experimental studies, the current version of the in silico model does not show an association between metastatic propensity and elevated IFP.