YAP-independent mechanotransduction drives breast cancer progression

The Hippo Transducer YAP/TAZ as a Biomarker of Therapeutic Response and Prognosis in Trastuzumab-Based Neoadjuvant Therapy Treated HER2-Positive Breast Cancer Patients

Background

We explored the therapeutic and prognostic effect of YAP/TAZ intensityinHER2-positive breast cancer patients. We also investigated the relationship between YAP/TAZ expression and Trastuzumab-resistance.

Methods

We collected clinicopathological information from 397 cases. We evaluated therapeutic and prognostic effect of YAP/TAZ and other variables. We also cultivated Trastuzumab-resistance cell lines and explored relationship between YAP/TAZ and Trastuzumab-resistance.

Results

Over-expression of YAP/TAZ was remarkable in Trastuzumab-resistant cells, and so did HER3 and HER2/HER3 heterodimer. Inhibition of YAP/TAZ expression reversed Trastuzumab-resistance.YAP/TAZ deficiency contributed to favorable therapeutic response, and so did hormone receptor insufficiency and chemotherapy dosage inferiority. Deficient YAP/TAZ intensity and abundant hormone receptor intensity contributed to better survival. Over-expression of YAP/TAZ was obvious in recurrent cases in comparison with their matching primary lesions. Prognostic superiority of insufficient YAP/TAZ intensity was more outstanding in hormone receptor negative cases. Over-expression of YAP/TAZ and HER3 was generally synchronous. Absence of HER3 expression in residual lesions might correlate with better breast cancer-free survival.

Conclusions

Over-expression of YAP/TAZ as well as HER-3 and HER2/HER3 heterodimer was synchronously remarkable in Trastuzumab-resistant cell lines. Inhibition of YAP/TAZ expression reversed Trastuzumab resistance. Deficient YAP/TAZ intensity as well as insufficient hormone receptor intensity and high chemotherapy dosage contributed to favorable therapeutic response. Deficient YAP/TAZ intensity and abundant hormone receptor intensity contributed to better survival, and so did absence of HER3expression in residual lesions. Prognostic superiority of YAP/TAZ expression depended on hormone receptor status. Cases with synchronous over-expression of YAP/TAZ and HER3 suffered poor survival, which revealed the potential effect of YAP/TAZ-HER2/HER3 crosstalk in prognosis of HER2-positive patients.

Effects of extracellular matrix viscoelasticity on cellular behaviour

Substantial research over the past two decades has established that extracellular matrix (ECM) elasticity, or stiffness, affects fundamental cellular processes, including spreading, growth, proliferation, migration, differentiation and organoid formation. Linearly elastic polyacrylamide hydrogels and polydimethylsiloxane (PDMS) elastomers coated with ECM proteins are widely used to assess the role of stiffness, and results from such experiments are often assumed to reproduce the effect of the mechanical environment experienced by cells in vivo. However, tissues and ECMs are not linearly elastic materials-they exhibit far more complex mechanical behaviours, including viscoelasticity (a time-dependent response to loading or deformation), as well as mechanical plasticity and nonlinear elasticity. Here we review the complex mechanical behaviours of tissues and ECMs, discuss the effect of ECM viscoelasticity on cells, and describe the potential use of viscoelastic biomaterials in regenerative medicine. Recent work has revealed that matrix viscoelasticity regulates these same fundamental cell processes, and can promote behaviours that are not observed with elastic hydrogels in both two- and three-dimensional culture microenvironments. These findings have provided insights into cell-matrix interactions and how these interactions differentially modulate mechano-sensitive molecular pathways in cells. Moreover, these results suggest design guidelines for the next generation of biomaterials, with the goal of matching tissue and ECM mechanics for in vitro tissue models and applications in regenerative medicine.

Differential SATB1 Expression Reveals Heterogeneity of Cutaneous T-Cell Lymphoma

SATB1 is an important T-cell specific chromatin organizer in cutaneous T-cell lymphoma, whereas its expression and function in mycosis fungoides (MF) remain ambiguous. Our study aimed to investigate the clinicopathological significance of SATB1 in a cohort of 170 patients with MF. SATB1 expression was heterogeneous among the patients with MF in each clinical stage. High SATB1 expression was associated with epidermal hyperplasia, eosinophil infiltration, less large-cell transformation, and favorable prognosis in MF cases. SATB1 and CD30 coexpression distinguished cutaneous CD30⁺ lymphoproliferative disorders from MF large-cell transformation. SATB1 silencing in MF lines showed that SATB1 upregulated the genes involved in eosinophil recruitment, including signal transducer and activator of transcription 3 and IL13, and downregulated the genes in cell-cycle progression, which may explain the inferior prognosis for low SATB1-expressing cases. Moreover, SATB1 was inversely correlated with PD-1 expression, indicating an exhausted status of SATB1-negative malignant T cells. SATB1 was positively correlated with toll-like receptors expression, suggesting innate immune activation in high SATB1-expressing MF cases. Therefore, variable SATB1 expression promotes heterogeneity in pathology and clinical outcome of patients with MF.

Plant-Based Scaffolds Modify Cellular Response to Drug and Radiation Exposure Compared to Standard Cell Culture Models

Plant-based scaffolds present many advantages over a variety of biomaterials. Recent studies explored their potential to be repopulated with human cells and thus highlight a growing interest for their use in tissue engineering or for biomedical applications. However, it is still unclear if these in vitro plant-based scaffolds can modify cell phenotype or affect cellular response to external stimuli. Here, we report the characterization of the mechano-regulation of melanoma SK-MEL-28 and prostate PC3 cells seeded on decellularized spinach leaves scaffolds, compared to cells deposited on standard rigid cell culture substrate, as well as their response to drug and radiation treatment. The results showed that YAP/TAZ signaling was downregulated, cellular morphology altered and proliferation rate decreased when cells were cultured on leaf scaffold. Interestingly, cell culture on vegetal scaffold also affected cellular response to external stress. Thus, SK-MEL-28 cells phenotype is modified leading to a decrease in MITF activity and drug resistance, while PC3 cells showed altered gene expression and radiation response. These findings shed lights on the decellularization of vegetal materials to provide substrates that can be repopulated with human cells to better reproduce a soft tissue microenvironment. However, these complex scaffolds mediate changes in cell behavior and in order to exploit the capability of matching physical properties of the various plant scaffolds to diverse physiological functionalities of cells and human tissue constructs, additional studies are required to better characterize physical and biochemical cell-substrate interactions.

Clinicopathologic significance of nuclear HER4 and phospho-YAP(S127) in human breast cancers and matching brain metastases

Background

Human epidermal growth factor receptor-4 (HER4) and yes-associated protein-1 (YAP) are candidate therapeutic targets in oncology. YAP's transcriptional coactivation function is modulated by the HER4 intracellular domain (HER4-ICD) in vitro, but the clinical relevance of this has not been established. This study investigated the potential for targeting the HER4-YAP pathway in brain metastatic breast cancer.

Methods

We performed immuno-phenotypic profiling of pathway markers in a consecutive breast cancer series with 25 years of clinical follow up (n = 371), and patient-matched breast and metastatic brain tumours (n = 91; 30 pairs).

Results

Membrane localisation of phospho-HER4 [pHER4(Y¹¹⁶²)] was infrequent in primary breast cancer, but very frequent in brain metastases (5.9% versus 75% positive), where it was usually co-expressed with pHER3(Y¹²⁸⁹) (p < 0.05). The presence of YAP in tumour cell nuclei was associated directly with nuclear pERK5(T²¹⁸/Y²¹⁰) (p = 0.003). However, relationships with disease-specific survival depended on oestrogen receptor (ER) status. Nuclear pYAP(S¹²⁷) was associated with smaller, good prognostic ER+ breast tumours (log-rank hazard-ratio 0.53; p = 9.6E^-03), but larger, poor prognostic triple-negative cancers (log-rank hazard-ratio 2.78; p = 1.7E^-02), particularly when co-expressed with nuclear HER4-ICD (p = 0.02). This phenotype was associated with stemness and mitotic instability markers (vimentin, SOX9, ID1, SPAG5, TTK, geminin; p < 0.05). YAP expression in brain metastases was higher than matched primary tumours; specifically, nuclear pYAP(S¹²⁷) in ER-negative cases (p < 0.05). Nuclear YAP was detected in ~70% of ER-negative, HER4-activated brain metastases.

Discussion

Our findings suggest that the canonical-mechanism where Hippo pathway-mediated phosphorylation of YAP ostensibly excludes it from the nucleus is dysfunctional in breast cancer. The data are consistent with pYAP(S¹²⁷) having independent transcriptional functions, which may include transducing neuregulin signals in brain metastases. Consistent with mechanistic studies implicating it as an ER co-factor, nuclear pYAP(S¹²⁷) associations with breast cancer clinical outcomes were dependent on ER status.

Conclusion

Preclinical studies investigating HER4 and nuclear YAP combination therapy strategies are warranted.

The Janus Role of Adhesion in Chondrogenesis

Tackling the first stages of the chondrogenic commitment is essential to drive chondrogenic differentiation to healthy hyaline cartilage and minimize hypertrophy. During chondrogenesis, the extracellular matrix continuously evolves, adapting to the tissue adhesive requirements at each stage. Here, we take advantage of previously developed nanopatterns, in which local surface adhesiveness can be precisely tuned, to investigate its effects on prechondrogenic condensation. Fluorescence live cell imaging, immunostaining, confocal microscopy and PCR analysis are used to follow the condensation process on the nanopatterns. Cell tracking parameters, condensate morphology, cell-cell interactions, mechanotransduction and chondrogenic commitment are evaluated in response to local surface adhesiveness. Results show that only condensates on the nanopatterns of high local surface adhesiveness are stable in culture and able to enter the chondrogenic pathway, thus highlighting the importance of controlling cell-substrate adhesion in the tissue engineering strategies for cartilage repair.

Aspirin attenuates YAP and β-catenin expression by promoting β-TrCP to overcome docetaxel and vinorelbine resistance in triple-negative breast cancer

The use of aspirin has been associated with reduced breast cancer risk, but it is litter known if aspirin overcomes chemoresistance in triple-negative breast cancer (TNBC). Herein, we demonstrated that changes in the expression of Yes-associated protein (YAP) and β-catenin might be a promising predictive biomarker for neoadjuvant chemotherapy sensitivity in TNBC patients. Inhibition of YAP or β-catenin enhanced the cytotoxicity of the anti-microtubule agents docetaxel and vinorelbine against drug-resistant TNBC cells as well as the sensitivity of these cells to the agents in vitro and in vivo. Interestingly, aspirin not only significantly inhibited the growth of TNBC cells, but also attenuated YAP and β-catenin expression by upregulating the E3 ubiquitin ligase β-TrCP to abolished docetaxel and vinorelbine resistance. The combination of aspirin and docetaxel or vinorelbine remarkably inhibited the growth of drug-resistant TNBC cells in vitro and in vivo. Moreover, TNBC patients with high YAP and/or β-catenin expression had a higher risk of relapse or mortality than patients with low YAP and/or β-catenin expression. Collectively, our study discovered a novel role of aspirin based on its anticancer effect, and put forward some possible mechanisms of chemoresistance in TNBC. The combined use of aspirin and anti-microtubule drugs presented several promising therapeutic approaches for TNBC treatment.

Emerging Biomimetic Materials for Studying Tumor and Immune Cell Behavior

Cancer is one of the leading causes of death both in the United States and worldwide. The dynamic microenvironment in which tumors grow consists of fibroblasts, immune cells, extracellular matrix (ECM), and cytokines that enable progression and metastasis. Novel biomaterials that mimic these complex surroundings give insight into the biological, chemical, and physical environment that cause cancer cells to metastasize and invade into other tissues. Two-dimensional (2D) cultures are useful for gaining limited information about cancer cell behavior; however, they do not accurately represent the environments that cells experience in vivo. Recent advances in the design and tunability of diverse three-dimensional (3D) biomaterials complement biological knowledge and allow for improved recapitulation of in vivo conditions. Understanding cell-ECM and cell-cell interactions that facilitate tumor survival will accelerate the design of more effective therapies. This review discusses innovative materials currently being used to study tumor and immune cell behavior and interactions, including materials that mimic the ECM composition, mechanical stiffness, and integrin binding sites of the tumor microenvironment.

Wnt Activation After Inhibition Restores Trabecular Meshwork Cells Toward a Normal Phenotype

Purpose

Wnt is a spatiotemporally regulated signaling pathway whose inhibition is associated with glaucoma, elevated intraocular pressure (IOP), and cell stiffening. Whether such changes are permanent or may be reversed is unclear. Here, we determine if activation of Wnt pathway after inhibition reverses the pathologic phenotype.

Methods

Primary human trabecular meshwork (hTM) cells from nonglaucomatous donors were cultured for 12 days in the absence or presence of Wnt modulators: (i) LGK974 (Porcn inhibitor, 10 µM); (ii) LY2090314 (pGSK3β inhibitor, 250 nM); or (iii) 9 days of LGK974 followed by 3 days of LY2090314. Wnt modulation were determined by Western blotting and extracellular matrix (ECM) related genes were evaluated by quantitative PCR. Cytoskeletal morphology was determined by immunofluorescence and cell stiffness by atomic force microscopy.

Results

Wnt activation was confirmed by downregulation of pGSK3β (0.3-fold; P < 0.01), overexpression of AXIN2 (6.7-fold; P < 0.001), and LEF1 (3.8-fold; P < 0.001). Wnt inhibition resulted in dramatic changes in F-actin, which were resolved with subsequent Wnt activation. Concurrently, cell stiffness that was elevated with Wnt inhibition (11.86 kPa; P < 0.01) decreased with subsequent Wnt activation (4.195 kPa; P < 0.01) accompanied by significant overexpression of phosphorylated YAP (1.8-fold; P < 0.001) and TAZ (1.4-fold; P < 0.001). Additionally, Wnt activation after inhibition significantly repressed ECM genes (SPARC and CTGF, P < 0.01), cross-linking genes (LOX and TGM2, P < 0.05), inhibitors of matrix metalloproteinases (TIMP1 and PAI1, P < 0.001), and overexpressed MMP 1/9/14 (P < 0.01).

Conclusions

These data strongly demonstrate that, in normal hTM cells, activation of the Wnt pathway reverses the pathological phenotype caused by Wnt inhibition and may thus be a viable therapeutic for lowering IOP.

Collagen microarchitecture mechanically controls myofibroblast differentiation

Altered microarchitecture of collagen type I is a hallmark of wound healing and cancer that is commonly attributed to myofibroblasts. However, it remains unknown which effect collagen microarchitecture has on myofibroblast differentiation. Here, we combined experimental and computational approaches to investigate the hypothesis that the microarchitecture of fibrillar collagen networks mechanically regulates myofibroblast differentiation of adipose stromal cells (ASCs) independent of bulk stiffness. Collagen gels with controlled fiber thickness and pore size were microfabricated by adjusting the gelation temperature while keeping their concentration constant. Rheological characterization and simulation data indicated that networks with thicker fibers and larger pores exhibited increased strain-stiffening relative to networks with thinner fibers and smaller pores. Accordingly, ASCs cultured in scaffolds with thicker fibers were more contractile, expressed myofibroblast markers, and deposited more extended fibronectin fibers. Consistent with elevated myofibroblast differentiation, ASCs in scaffolds with thicker fibers exhibited a more proangiogenic phenotype that promoted endothelial sprouting in a contractility-dependent manner. Our findings suggest that changes of collagen microarchitecture regulate myofibroblast differentiation and fibrosis independent of collagen quantity and bulk stiffness by locally modulating cellular mechanosignaling. These findings have implications for regenerative medicine and anticancer treatments.

High type I collagen density fails to increase breast cancer stem cell phenotype

Breast cancer is a highly frequent and lethal malignancy which metastasis and relapse frequently associates with the existence of breast cancer stem cells (CSCs). CSCs are undifferentiated, aggressive and highly resistant to therapy, with traits modulated by microenvironmental cells and the extracellular matrix (ECM), a biologically complex and dynamic structure composed mainly by type I collagen (Col-I). Col-I enrichment in the tumor-associated ECM leads to microenvironment stiffness and higher tumor aggressiveness and metastatic potential. While Col-I is also known to induce tumor stemness, it is unknown if such effect is dependent of Col-I density. To answer this question, we evaluated the stemness phenotype of MDA-MB-231 and MCF-7 human breast cancer cells cultured within gels of varying Col-I densities. High Col-I density increased CD44⁺CD24⁻ breast cancer stem cell (BCSC) immunophenotype but failed to potentiate Col-I fiber alignment, cell self-renewal and clonogenicity in MDA-MB-231 cells. In MCF-7 cells, high Col-I density decreased total levels of variant CD44 (CD44v). Common to both cell types, high Col-I density induced neither markers related to CSC nor those related with mechanically-induced cell response. We conclude that high Col-I density per se is not sufficient to fully develop the BCSC phenotype.

Regulation of Hippo signaling and triple negative breast cancer progression by an ubiquitin ligase RNF187

Breast cancer is the most common malignancy for women worldwide, while Triple Negative Breast Cancer (TNBC) accounts for 20% in all patients. Compared with estrogen receptor positive breast cancer, which could be effectively controlled via endocrine therapy, TNBC is more aggressive and worse in prognosis. It is therefore urgent and necessary to develop a novel therapeutic strategy for TNBC treatment. Recent studies identified Hippo signaling is highly activated in TNBC, which could be a driving pathway for TNBC progression. In our study, we determine RNF187 as a negative regulator for Hippo signaling activation. RNF187 depletion significantly decreases cell migration and invasion capacity in TNBC. These effects could be rescued by further YAP depletion. Depletion of RNF187 increases the YAP protein level and Hippo signaling target genes, such as CTGF and CYR61 in TNBC. Immuno-precipitation assay shows that RNF187 associates with YAP, promoting its degradation possibly via inducing YAP K48-dependent poly-ubiquitination. Interestingly, Our clinical data reveals that RNF187 reversely correlates with YAP protein level and Hippo target genes. RNF187 tends to correlate with good prognosis in TNBC patients. Our study provides evidence to establish a proteolytic mechanism in regulation Hippo signaling activation in TNBC.

Photoacoustic imaging of cells in a three-dimensional microenvironment

Imaging live cells in a three-dimensional (3D) culture system yields more accurate information and spatial visualization of the interplay of cells and the surrounding matrix components compared to using a two-dimensional (2D) cell culture system. However, the thickness of 3D cultures results in a high degree of scattering that makes it difficult for the light to penetrate deeply to allow clear optical imaging. Photoacoustic (PA) imaging is a powerful imaging modality that relies on a PA effect generated when light is absorbed by exogenous contrast agents or endogenous molecules in a medium. It combines a high optical contrast with a high acoustic spatiotemporal resolution, allowing the noninvasive visualization of 3D cellular scaffolds at considerable depths with a high resolution and no image distortion. Moreover, advances in targeted contrast agents have also made PA imaging capable of molecular and cellular characterization for use in preclinical personalized diagnostics or PA imaging-guided therapeutics. Here we review the applications and challenges of PA imaging in a 3D cellular microenvironment. Potential future developments of PA imaging in preclinical applications are also discussed.

Decellularized mice colons as models to study the contribution of the extracellular matrix to cell behavior and colon cancer progression

Current 3D culture models to study colorectal cancer lack architectural support and signaling proteins provided by the tissue extracellular matrix (ECM) which may influence cell behavior and cancer progression. Therefore, the ability to study cancer cells in the context of a matrix that is physiologically more relevant and to understand how the ECM affects cancer progression has been understudied. To address this, we developed an ex-vivo 3D system, provided by intact wild type (WT) and colon cancer susceptible decellularized mouse colons (DMC), to support the growth of human cancer cells. DMC are free of viable cells but still contain extracellular matrix proteins including subsets of collagens. Stiffness, an important mechanical property, is also maintained in DMCs. Importantly, we observed that the DMC is permissive for cell proliferation and differentiation of a human colon cancer cell line (HT-29). Notably, the ability of cells in the WT DMC to differentiate was also greater when compared to Matrigel™, an extracellular matrix extract from a mouse tumor cell line. Additionally, we observed in invasion assays that DMC obtained from polyps from a colon cancer susceptible mouse model facilitated increased cell migration/invasion of colorectal cancer cells and immortalized non-tumor colonic epithelial cells compared to DMC from WT mice. Finally, using mass spectrometry, we identified extracellular matrix proteins that are more abundant in DMC from a colorectal cancer mouse model compared to age and sex-matched WT mice. We propose that these abundantly expressed proteins in the tumor microenvironment are potentially involved in colorectal cancer progression. STATEMENT OF SIGNIFICANCE: Decellularized matrices, when properly produced, are attractive biomaterials for tissue regeneration and replacement. We show here that the mouse decellularized matrices can also be repurposed to elucidate how the extracellular matrix influences human cell behavior and cancer progression. To do this we produce decellularized matrices, from mice colonic tissue, that have preserved tissue mechanical and structural properties. We demonstrate that the matrix better supports the differentiation of HT-29 cells, a colonic cancer cell line, compared to Matrigel™. Additionally, we show that the extracellular matrix contributes to colon cancer progression via invasion assays using extracellular matrix extracts. Finally, we use mass spectrometry to identify ECM proteins that are more abundant in colonic polyps compared to adjacent tissue regions. This model system may have therapeutic implications for colorectal cancer patients.

Matrix stiffness modulates ILK-mediated YAP activation to control the drug resistance of breast cancer cells

One of the hallmarks of cancer progression is strong drug resistance during clinical treatments. The tumor microenvironment is closely associated with multidrug resistance, the optimization of tumor microenvironments may have a strong therapeutic effect. In this study, we configured polyacrylamide hydrogels of varying stiffness [low (10 kPa), intermediate (38 kPa) and high (57 kPa)] to simulate tissue physical matrix stiffness across different stages of breast cancer. After treatment with doxorubicin, cell survival rates on intermediate stiffness substrate are significantly higher. We find that high expression of ILK and YAP reduces the survival rates of breast cancer patients. Drug resistance is closely associated with the inactivation of the hippo pathway protein Merlin/MST/LATS and the activation of YAP. These results not only highlight the understanding of drug resistance mechanisms but also serve as a new basis for developing breast cancer treatment delivery systems.

Identification of cell context-dependent YAP-associated proteins reveals β1 and β4 integrin mediate YAP translocation independently of cell spreading

Yes-associated protein (YAP) is a transcriptional regulator and mechanotransducer, relaying extracellular matrix (ECM) stiffness into proliferative gene expression in 2D culture. Previous studies show that YAP activation is dependent on F-actin stress fiber mediated nuclear pore opening, however the protein mediators of YAP translocation remain unclear. Here, we show that YAP co-localizes with F-actin during activating conditions, such as sparse plating and culturing on stiff 2D substrates. To identify proteins mediating YAP translocation, we performed co-immunoprecipitation followed by mass spectrometry (co-IP/MS) for proteins that differentially associated with YAP under activating conditions. Interestingly, YAP preferentially associates with β1 integrin under activating conditions, and β4 integrin under inactivating conditions. In activating conditions, CRISPR/Cas9 knockout (KO) of β1 integrin (ΔITGB1) resulted in decreased cell area, which correlated with decreased YAP nuclear localization. ΔITGB1 did not significantly affect the slope of the correlation between YAP nuclear localization with area, but did decrease overall nuclear YAP independently of cell spreading. In contrast, β4 integrin KO (ΔITGB4) cells showed no change in cell area and similarly decreased nuclear YAP. These results reveal proteins that differentially associate with YAP during activation, which may aid in regulating YAP nuclear translocation.

Beyond proteases: Basement membrane mechanics and cancer invasion

In epithelial cancers, cells must invade through basement membranes (BMs) to metastasize. The BM, a thin layer of extracellular matrix underlying epithelial and endothelial tissues, is primarily composed of laminin and collagen IV and serves as a structural barrier to cancer cell invasion, intravasation, and extravasation. BM invasion has been thought to require protease degradation since cells, which are typically on the order of 10 µm in size, are too large to squeeze through the nanometer-scale pores of the BM. However, recent studies point toward a more complex picture, with physical forces generated by cancer cells facilitating protease-independent BM invasion. Moreover, collective cell interactions, proliferation, cancer-associated fibroblasts, myoepithelial cells, and immune cells are all implicated in regulating BM invasion through physical forces. A comprehensive understanding of BM structure and mechanics and diverse modes of BM invasion may yield new strategies for blocking cancer progression and metastasis.

Transcriptomic analysis reveals that BMP4 sensitizes glioblastoma tumor-initiating cells to mechanical cues

The poor prognosis of glioblastoma (GBM) is associated with a highly invasive stem-like subpopulation of tumor-initiating cells (TICs), which drive recurrence and contribute to intra-tumoral heterogeneity through differentiation. These TICs are better able to escape extracellular matrix-imposed mechanical restrictions on invasion than their more differentiated progeny, and sensitization of TICs to extracellular matrix mechanics extends survival in preclinical models of GBM. However, little is known about the molecular basis of the relationship between TIC differentiation and mechanotransduction. Here we explore this relationship through a combination of transcriptomic analysis and studies with defined-stiffness matrices. We show that TIC differentiation induced by bone morphogenetic protein 4 (BMP4) suppresses expression of proteins relevant to extracellular matrix signaling and sensitizes TIC spreading to matrix stiffness. Moreover, our findings point towards a previously unappreciated connection between BMP4-induced differentiation, mechanotransduction, and metabolism. Notably, stiffness and differentiation modulate oxygen consumption, and inhibition of oxidative phosphorylation influences cell spreading in a stiffness- and differentiation-dependent manner. Our work integrates bioinformatic analysis with targeted molecular measurements and perturbations to yield new insight into how morphogen-induced differentiation influences how GBM TICs process mechanical inputs.

Mesenchymal stromal cell activation by breast cancer secretomes in bioengineered 3D microenvironments

This study shows the activation of tumour-associated mesenchymal stromal cells by breast cancer secretomes in bioengineered 3D microenvironments using comprehensive multiomics analysis methods.

Mesenchymal stromal cells (MSCs) are key contributors of the tumour microenvironment and are known to promote cancer progression through reciprocal communication with cancer cells, but how they become activated is not fully understood. Here, we investigate how breast cancer cells from different stages of the metastatic cascade convert MSCs into tumour-associated MSCs (TA-MSCs) using unbiased, global approaches. Using mass spectrometry, we compared the secretomes of MCF-7 cells, invasive MDA-MB-231 cells, and sublines isolated from bone, lung, and brain metastases and identified ECM and exosome components associated with invasion and organ-specific metastasis. Next, we used synthetic hydrogels to investigate how these different secretomes activate MSCs in bioengineered 3D microenvironments. Using kinase activity profiling and RNA sequencing, we found that only MDA-MB-231 breast cancer secretomes convert MSCs into TA-MSCs, resulting in an immunomodulatory phenotype that was particularly prominent in response to bone-tropic cancer cells. We have investigated paracrine signalling from breast cancer cells to TA-MSCs in 3D, which may highlight new potential targets for anticancer therapy approaches aimed at targeting tumour stroma.