Matrix stiffness induces epithelial-mesenchymal transition and promotes chemoresistance in pancreatic cancer cells

Microarchitectural mimicking of stroma-induced vasculature compression in pancreatic tumors using a 3D engineered model

Fibrotic tumors, such as pancreatic ductal adenocarcinoma (PDAC), are characterized for high desmoplastic reaction, which results in high intra-tumoral solid stress leading to the compression of blood vessels. These microarchitectural alterations cause loss of blood flow and poor intra-tumoral delivery of therapeutics. Currently, there is a lack of relevant in vitro models capable of replicating these mechanical characteristics and to test anti-desmoplastic compounds. Here, a multi-layered vascularized 3D PDAC model consisting of primary human pancreatic stellate cells (PSCs) embedded in collagen/fibrinogen (Col/Fib), mimicking tumor tissue within adjunct healthy tissue, is presented to study the fibrosis-induced compression of vasculature in PDAC. It is demonstrated how the mechanical and biological stimulation induce PSC activation, extracellular matrix production and eventually vessel compression. The clinical relevance is confirmed by correlating with patient transcriptomic data. Furthermore, the effects of gradual vessel compression on the fluid dynamics occurring within the channel is evaluated in silico. Finally, it is demonstrated how cancer-associated fibroblast (CAF)-modulatory therapeutics can inhibit the cell-mediated compression of blood vessels in PDAC in vitro, in silico and in vivo. It is envisioned that this 3D model is used to improve the understanding of mechanical characteristics in tumors and for evaluating novel anti-desmoplastic therapeutics.

The role of the Na+/Ca2+-exchanger (NCX) in cancer-associated fibroblasts

Cancer is characterized by uncontrolled growth, invasion, and metastasis. In addition to solid cancer cells, cancer-associated fibroblasts (CAFs) play important roles in cancer pathophysiology. They arise from "healthy" cells but get manipulated by solid cancer cells to supply them and develop a tumor microenvironment (TME) that protects the cancer cells from the immune defense. A wide variety of cell types can differentiate into CAFs, including fibroblasts, endothelial cells, and epithelial cells. Precise Ca²⁺ regulation is essential for each cell including CAFs. The electrogenic Na⁺/Ca²⁺ exchanger (NCX) is one of the ubiquitously expressed regulatory Ca²⁺ transport proteins that rapidly responds to changes of the intracellular ion concentrations. Its transport function is also influenced by the membrane potential and thereby indirectly by the activity of ion channels. NCX transports Ca²⁺ out of the cell (forward mode) or allows its influx (reverse mode), always in exchange for 3 Na⁺ ions that are moved into the opposite direction. In this review, we discuss the functional roles NCX has in CAFs and how these depend on the properties of the TME. NCX activity modifies migration and leads to a reduced proliferation and apoptosis. The effect of the NCX in fibrosis is still largely unknown.

Substrate stiffness induces nuclear localization of myosin regulatory light chain to suppress apoptosis

Stiffness of the extracellular matrix regulates various biological responses, but the response mechanisms are poorly understood. Here, we found that the nuclear diphosphorylated myosin regulatory light chain (2P-MRLC) is a critical mechanomediator that suppresses apoptosis in response to substrate stiffness. Stiff substrates promoted the nuclear localization of 2P-MRLC. Zipper-interacting protein kinase [ZIPK; also known as death-associated protein kinase 3 (DAPK3)], a kinase for MRLC, was localized in the nucleus in response to stiff substrates and promoted the nuclear localization of 2P-MRLC. Moreover, actin fiber formation induced by substrate stiffness promoted the nuclear localization of 2P-MRLC via ZIPK. 2P-MRLC in response to substrate stiffness suppressed the expression of MAF bZIP transcription factor B (MafB) and repressed apoptosis. These findings reveal a newly identified role of MRLC in mechanotransduction.

Stiff matrix induces exosome secretion to promote tumour growth

Tissue fibrosis and extracellular matrix (ECM) stiffening promote tumour progression. The mechanisms by which ECM regulates its contacting cells have been extensively studied. However, how stiffness influences intercellular communications in the microenvironment for tumour progression remains unknown. Here we report that stiff ECM stimulates the release of exosomes from cancer cells. We delineate a molecular pathway that links stiff ECM to activation of Akt, which in turn promotes GTP loading to Rab8 that drives exosome secretion. We further show that exosomes generated from cells grown on stiff ECM effectively promote tumour growth. Proteomic analysis revealed that the Notch signalling pathway is activated in cells treated with exosomes derived from tumour cells grown on stiff ECM, consistent with our gene expression analysis of liver tissues from patients. Our study reveals a molecular mechanism that regulates exosome secretion and provides insight into how mechanical properties of the ECM control the tumour microenvironment for tumour growth.

[Matrix stiffening related lncRNA SNHG8 regulates chemosensitivity of ovarian cancer]

Extracellular matrix (ECM) has been implicated in tumor progress and chemosensitivity. Ovarian cancer brings a great threat to the health of women with a significant feature of high mortality and poor prognosis. However, the potential significance of matrix stiffness in the pattern of long non-coding RNAs (lncRNAs) expression and ovarian cancer drug sensitivity is still largely unkown. Here, based on RNA-seq data of ovarian cancer cell cultured on substrates with different stiffness, we found that a great amount of lncRNAs were upregulated in stiff group, whereas SNHG8 was significantly downregulated, which was further verified in ovarian cancer cells cultured on polydimethylsiloxane (PDMS) hydrogel. Knockdown of SNHG8 led to an impaired efficiency of homologous repair, and decreased cellular sensitivity to both etoposide and cisplatin. Meanwhile, the results of the GEPIA analysis indicated that the expression of SNHG8 was significantly decreased in ovarian cancer tissues, which was negatively correlated with the overall survival of patients with ovarian cancer. In conclusion, matrix stiffening related lncRNA SNHG8 is closely related to chemosensitivity and prognosis of ovarian cancer, which might be a novel molecular marker for chemotherapy drug instruction and prognosis prediction.

microRNAs Associated with Gemcitabine Resistance via EMT, TME, and Drug Metabolism in Pancreatic Cancer

Despite extensive research, pancreatic cancer remains a lethal disease with an extremely poor prognosis. The difficulty in early detection and chemoresistance to therapeutic agents are major clinical concerns. To improve prognosis, novel biomarkers, and therapeutic strategies for chemoresistance are urgently needed. microRNAs (miRNAs) play important roles in the development, progression, and metastasis of several cancers. During the last few decades, the association between pancreatic cancer and miRNAs has been extensively elucidated, with several miRNAs found to be correlated with patient prognosis. Moreover, recent evidence has revealed that miRNAs are intimately involved in gemcitabine sensitivity and resistance through epithelial-to-mesenchymal transition, the tumor microenvironment, and drug metabolism. Gemcitabine is the gold standard drug for pancreatic cancer treatment, but gemcitabine resistance develops easily after chemotherapy initiation. Therefore, in this review, we summarize the gemcitabine resistance mechanisms associated with aberrantly expressed miRNAs in pancreatic cancer, especially focusing on the mechanisms associated with epithelial-to-mesenchymal transition, the tumor microenvironment, and metabolism. This novel evidence of gemcitabine resistance will drive further research to elucidate the mechanisms of chemoresistance and improve patient outcomes.

Dynamic Magneto-Softening of 3D Hydrogel Reverses Malignant Transformation of Cancer Cells and Enhances Drug Efficacy

High extracellular matrix stiffness is a prominent feature of malignant tumors associated with poor clinical prognosis. To elucidate mechanistic connections between increased matrix stiffness and tumor progression, a variety of hydrogel scaffolds with dynamic changes in stiffness have been developed. These approaches, however, are not biocompatible at high temperature, strong irradiation, and acidic/basic pH, often lack reversibility (can only stiffen and not soften), and do not allow study on the same cell population longitudinally. In this work, we develop a dynamic 3D magnetic hydrogel whose matrix stiffness can be wirelessly and reversibly stiffened and softened multiple times with different rates of change using an external magnet. With this platform, we found that matrix stiffness increased tumor malignancy including denser cell organization, epithelial-to-mesenchymal transition and hypoxia. More interestingly, these malignant transformations could be halted or reversed with matrix softening (i.e., mechanical rescue), to potentiate drug efficacy attributing to reduced solid stress from matrix and downregulation of cell mechano-transductors including YAP1. We propose that our platform can be used to deepen understanding of the impact of matrix softening on cancer biology, an important but rarely studied phenomenon.

Suppressed Migration and Enhanced Cisplatin Chemosensitivity in Human Cancer Cell Lines by Tuning the Molecular Mobility of Supramolecular Biomaterials

Cancer cells recognize physical cues transmitted from the surrounding microenvironment, and accordingly alter the migration and chemosensitivity. Cell adhesive biomaterials with tunable physical properties can contribute to the understanding of cancer cell responses, and development of new cancer therapies. Previously, it was reported that polyrotaxane-based surfaces with molecular mobility effectively modulate cellular functions via the yes-associated protein (YAP)-related signaling pathway. In the present study, the impact of molecular mobility of polyrotaxane surfaces on the migration and chemosensitivity of lung (A549), pancreatic (BxPC-3), and breast cancer (MDA-MB-231) cell lines is investigated, and it is found that the cellular spreading of adherent A549 and BxPC-3 cells and nuclear YAP translocation are promoted on low-mobility surfaces, suggesting that cancer cells alter their subcellular YAP localization in response to molecular mobility. Furthermore, low-mobility surfaces suppress cellular migration more than high-mobility surfaces. Additionally, low-mobility surfaces promote the cisplatin chemosensitivity of each cancer cell line to a greater extent than high-mobility surfaces. These results suggest that the molecular mobility of polyrotaxane surfaces suppresses cellular migration and enhances chemosensitivity via the subcellular translocation of YAP in cancer cells. Biointerfaces based on polyrotaxanes can thus be a new platform for elucidating cancer cell migration and chemoresistance mechanisms.

Prognostic Significance of Integrin Subunit Alpha 2 (ITGA2) and Role of Mechanical Cues in Resistance to Gemcitabine in Pancreatic Ductal Adenocarcinoma (PDAC)

INTRODUCTION

PDAC is an extremely aggressive tumor with a poor prognosis and remarkable therapeutic resistance. The dense extracellular matrix (ECM) which characterizes PDAC progression is considered a fundamental determinant of chemoresistance, with major contributions from mechanical factors. This study combined biomechanical and pharmacological approaches to evaluate the role of the cell-adhesion molecule ITGA2, a key regulator of ECM, in PDAC resistance to gemcitabine.

METHODS

The prognostic value of ITGA2 was analysed in publicly available databases and tissue-microarrays of two cohorts of radically resected and metastatic patients treated with gemcitabine. PANC-1 and its gemcitabine-resistant clone (PANC-1R) were analysed by RNA-sequencing and label-free proteomics. The role of ITGA2 in migration, proliferation, and apoptosis was investigated using hydrogel-coated wells, siRNA-mediated knockdown and overexpression, while collagen-embedded spheroids assessed invasion and ECM remodeling.

RESULTS

High ITGA2 expression correlated with shorter progression-free and overall survival, supporting its impact on prognosis and the lack of efficacy of gemcitabine treatment. These findings were corroborated by transcriptomic and proteomic analyses showing that ITGA2 was upregulated in the PANC-1R clone. The aggressive behavior of these cells was significantly reduced by ITGA2 silencing both in vitro and in vivo, while PANC-1 cells growing under conditions resembling PDAC stiffness acquired resistance to gemcitabine, associated to increased ITGA2 expression. Collagen-embedded spheroids of PANC-1R showed a significant matrix remodeling and spreading potential via increased expression of CXCR4 and MMP2. Additionally, overexpression of ITGA2 in MiaPaCa-2 cells triggered gemcitabine resistance and increased proliferation, both in vitro and in vivo, associated to upregulation of phospho-AKT.

CONCLUSIONS

ITGA2 emerged as a new prognostic factor, highlighting the relevance of stroma mechanical properties as potential therapeutic targets to counteract gemcitabine resistance in PDAC.

Reprogramming of Activated Pancreatic Stellate Cells via Mechanical Modulation of Transmembrane Force-sensitive N-cadherin Receptor

Cancer has been the leading cause of death due mainly to tumor metastasis. The tumor microenvironment plays a key role in tumor metastasis. As the main stromal cells in tumor microenvironment originated from activated fibroblast, cancer-associated fibroblasts (CAFs) play a major role in promoting tumor metastasis. A promising therapeutic avenue is reprogramming of CAFs into tumor-restraining quiescence state. In this study, we observed that CAF-like active pancreatic stellate cells (PSCs) interact with each other via N-cadherin, a force-sensitive transmembrane receptor. Since N-cadherin ligation mediated mechanotransduction has been reported to restrict integrin mediated signalling, we thus hypothesized that the reprogramming of activated PSCs by mechanical modulation of N-cadherin ligation might be possible. To test this hypothesis, we grafted N-cadherin ligand (HAVDI peptide) onto soft polyethylene glycol hydrogel substrate prior to cell adhesion to mimic cell-cell interaction via N-cadherin ligation. We found that the activated PSCs could be reprogrammed to their original quiescent state when transferred onto the substrate with immobilized HAVDI peptide. These results reveal a key role of mechanosensing by intercellular transmembrane receptor in reprogramming of activated PSCs, and provide a potential way for designing novel therapeutic strategies for cancer treatment.

Pericentromeric satellite lncRNAs are induced in cancer-associated fibroblasts and regulate their functions in lung tumorigenesis

The abnormal tumor microenvironment (TME) often dictates the therapeutic response of cancer to chemo- and immuno-therapy. Aberrant expression of pericentromeric satellite repeats has been reported for epithelial cancers, including lung cancer. However, the transcription of tandemly repetitive elements in stromal cells of the TME has been unappreciated, limiting the optimal use of satellite transcripts as biomarkers or anti-cancer targets. We found that transcription of pericentromeric satellite DNA (satDNA) in mouse and human lung adenocarcinoma was observed in cancer-associated fibroblasts (CAFs). In vivo, lung fibroblasts expressed pericentromeric satellite repeats HS2/HS3 specifically in tumors. In vitro, transcription of satDNA was induced in lung fibroblasts in response to TGFβ, IL1α, matrix stiffness, direct contact with tumor cells and treatment with chemotherapeutic drugs. Single-cell transcriptome analysis of human lung adenocarcinoma confirmed that CAFs were the cell type with the highest number of satellite transcripts. Human HS2/HS3 pericentromeric transcripts were detected in the nucleus, cytoplasm, extracellularly and co-localized with extracellular vesicles in situ in human biopsies and activated fibroblasts in vitro. The transcripts were transmitted into recipient cells and entered their nuclei. Knock-down of satellite transcripts in human lung fibroblasts attenuated cellular senescence and blocked the formation of an inflammatory CAFs phenotype which resulted in the inhibition of their pro-tumorigenic functions. In sum, our data suggest that satellite long non-coding (lnc) RNAs are induced in CAFs, regulate expression of inflammatory genes and can be secreted from the cells, which potentially might present a new element of cell-cell communication in the TME.

Extracellular matrix physical properties govern the diffusion of nanoparticles in tumor microenvironment

Nanoparticles (NPs) are confronted with limited and disappointing delivery efficiency in tumors clinically. The tumor extracellular matrix (ECM), whose physical traits have recently been recognized as new hallmarks of cancer, forms a main steric obstacle for NP diffusion, yet the role of tumor ECM physical traits in NP diffusion remains largely unexplored. Here, we characterized the physical properties of clinical gastric tumor samples and observed limited distribution of NPs in decellularized tumor tissues. We also performed molecular dynamics simulations and in vitro hydrogel experiments through single-particle tracking to investigate the diffusion mechanism of NPs and understand the influence of tumor ECM physical properties on NP diffusion both individually and collectively. Furthermore, we developed an estimation matrix model with evaluation scores of NP diffusion efficiency through comprehensive analyses of the data. Thus, beyond finding that loose and soft ECM with aligned structure contribute to efficient diffusion, we now have a systemic model to predict NP diffusion efficiency based on ECM physical traits and provide critical guidance for personalized tumor diagnosis and treatment.

Working a second job: Cell adhesion proteins that moonlight in the nucleus

Cells are adept at sensing changes in their environment, transmitting signals internally to coordinate responses to external stimuli, and thereby influencing adaptive changes in cell states and behavior. Often, this response involves modulation of gene expression in the nucleus, which is seen largely as a physically separated process from the rest of the cell. Mechanosensing, whereby a cell senses physical stimuli, and integrates and converts these inputs into downstream responses including signaling cascades and gene regulatory changes, involves the participation of several macromolecular structures. Of note, the extracellular matrix (ECM) and its constituent macromolecules comprise an essential part of the cellular microenvironment, allowing cells to interact with each other, and providing both structural and biochemical stimuli sensed by adhesion transmembrane receptors. This highway of information between the ECM, cell adhesion proteins, and the cytoskeleton regulates cellular behavior, the disruption of which results in disease. Emerging evidence suggests a more direct role for some of these adhesion proteins in chromatin structure and gene regulation, RNA maturation and other non-canonical functions. While many of these discoveries were previously limited to observations of cytoplasmic-nuclear transport, recent advances in microscopy, and biochemical, proteomic and genomic technologies have begun to significantly enhance our understanding of the impact of nuclear localization of these proteins. This review will briefly cover known cell adhesion proteins that migrate to the nucleus, and their downstream functions. We will outline recent advances in this very exciting yet still emerging field, with impact ranging from basic biology to disease states like cancer.

The role of RAS oncogenes in controlling epithelial mechanics

Mutations in RAS are key oncogenic drivers and therapeutic targets. Oncogenic Ras proteins activate a network of downstream signalling pathways, including extracellular signal-regulated kinase (ERK) and phosphatidylinositol 3-kinase (PI3K), promoting cell proliferation and survival. However, there is increasing evidence that RAS oncogenes also alter the mechanical properties of both individual malignant cells and transformed tissues. Here we discuss the role of oncogenic RAS in controlling mechanical cell phenotypes and how these mechanical changes promote oncogenic transformation in single cells and tissues. RAS activation alters actin organisation and actomyosin contractility. These changes alter cell rheology and impact mechanosensing through changes in substrate adhesion and YAP/TAZ-dependent mechanotransduction. We then discuss how these changes play out in cell collectives and epithelial tissues by driving large-scale tissue deformations and the expansion of malignant cells. Uncovering how RAS oncogenes alter cell mechanics will lead to a better understanding of the morphogenetic processes that underlie tumour formation in RAS-mutant cancers.

Gastrointestinal pan-cancer landscape of tumor matrix heterogeneity identifies biologically distinct matrix stiffness subtypes predicting prognosis and chemotherapy efficacy

Gastrointestinal (GI) cancers are a heterogeneous group of primary solid tumors, arising in GI tract from the esophagus to rectum. Matrix stiffness (MS) is a critical physical factor for cancer progression; however, its importance in tumor progression remains to be comprehensively recognized. Herein, we conducted a comprehensive pan-cancer analysis of MS subtypes across seven GI-cancer types. Using unsupervised clustering based on literature-derived MS-specific pathway signatures, the GI-tumor samples were divided into three MS subtypes, termed as the Soft, Mixed and Stiff. Then, distinct prognoses, biological features, tumor microenvironments and mutation landscapes among three MS subtypes were revealed. The Stiff tumor subtype was associated with the poorest prognosis, the most malignant biological behaviors, and the immunosuppressive tumor stromal microenvironment. Furthermore, multiple machine learning algorithms were used to develop an 11-gene MS-signature to identify the MS subtypes of GI-caner and predict chemotherapy sensitivity, which were further validated in two external GI-cancer cohorts. This novel MS-based classification on GI-cancers could enhance our understanding of the important role of MS in tumor progression, and may have implications for the optimization of individualized cancer management.

Collagen VI expression is negatively mechanosensitive in pancreatic cancer cells and supports the metastatic niche

Pancreatic cancer is a deadly and highly metastatic disease, although how metastatic lesions establish is not fully understood. A key feature of pancreatic tumours is extensive fibrosis and deposition of extracellular matrix (ECM). While pancreatic cancer cells are programmed by stimuli derived from a stiff ECM, metastasis requires loss of attachment and adaptation to a softer microenvironment at distant sites. Growing evidence suggests that stiff ECM influences pancreatic cancer cell behaviour. Here, we argue that this influence is reversible and that pancreatic cancer cells can be reprogrammed upon sensing soft substrates. Using engineered polyacrylamide hydrogels with tuneable mechanical properties, we show that collagen VI is specifically upregulated in pancreatic cancer cells on soft substrates, due to a lack of integrin engagement. Furthermore, the expression of collagen VI is inversely correlated with mechanosensing and activity of YAP (also known as YAP1), which might be due to a direct or indirect effect on transcription of genes encoding collagen VI. Collagen VI supports migration in vitro and metastasis formation in vivo. Metastatic nodules formed by pancreatic cancer cells lacking Col6a1 display stromal cell-derived collagen VI deposition, suggesting that collagen VI derived from either cancer cells or the stroma is an essential component of the metastatic niche. This article has an associated First Person interview with Vasileios Papalazarou, joint first author of the paper.

Three-Dimensional Collagen Topology Shapes Cell Morphology, beyond Stiffness

Cellular heterogeneity is associated with many physiological processes, including pathological ones, such as morphogenesis and tumorigenesis. The extracellular matrix (ECM) is a key player in the generation of cellular heterogeneity. Advances in our understanding rely on our ability to provide relevant in vitro models. This requires obtainment of the characteristics of the tissues that are essential for controlling cell fate. To do this, we must consider the diversity of tissues, the diversity of physiological contexts, and the constant remodeling of the ECM along these processes. To this aim, we have fabricated a library of ECM models for reproducing the scaffold of connective tissues and the basement membrane by using different biofabrication routes based on the electrospinning and drop casting of biopolymers from the ECM. Using a combination of electron microscopy, multiphoton imaging, and AFM nanoindentation, we show that we can vary independently protein composition, topology, and stiffness of ECM models. This in turns allows one to generate the in vivo complexity of the phenotypic landscape of ovarian cancer cells. We show that, while this phenotypic shift cannot be directly correlated with a unique ECM feature, the three-dimensional collagen fibril topology patterns cell shape, beyond protein composition and stiffness of the ECM. On this line, this work is a further step toward the development of ECM models recapitulating the constantly remodeled environment that cells face and thus provides new insights for cancer model engineering and drug testing.

Targeting the tumor stroma for cancer therapy

Tumors are comprised of both cancer cells and surrounding stromal components. As an essential part of the tumor microenvironment, the tumor stroma is highly dynamic, heterogeneous and commonly tumor-type specific, and it mainly includes noncellular compositions such as the extracellular matrix and the unique cancer-associated vascular system as well as a wide variety of cellular components including activated cancer-associated fibroblasts, mesenchymal stromal cells, pericytes. All these elements operate with each other in a coordinated fashion and collectively promote cancer initiation, progression, metastasis and therapeutic resistance. Over the past few decades, numerous studies have been conducted to study the interaction and crosstalk between stromal components and neoplastic cells. Meanwhile, we have also witnessed an exponential increase in the investigation and recognition of the critical roles of tumor stroma in solid tumors. A series of clinical trials targeting the tumor stroma have been launched continually. In this review, we introduce and discuss current advances in the understanding of various stromal elements and their roles in cancers. We also elaborate on potential novel approaches for tumor-stroma-based therapeutic targeting, with the aim to promote the leap from bench to bedside.

Cancer as a biophysical disease: Targeting the mechanical-adaptability program

With the number of cancer cases projected to significantly increase over time, researchers are currently exploring "nontraditional" research fields in the pursuit of novel therapeutics. One emerging area that is steadily gathering interest revolves around cellular mechanical machinery. When looking broadly at the physical properties of cancer, it has been debated whether a cancer could be defined as either stiffer or softer across cancer types. With numerous articles supporting both sides, the evidence instead suggests that cancer is not particularly regimented. Instead, cancer is highly adaptable, allowing it to endure the constantly changing microenvironments cancer cells encounter, such as tumor compression and the shear forces in the vascular system and body. What allows cancer cells to achieve this adaptability are the particular proteins that make up the mechanical network, leading to a particular mechanical program of the cancer cell. Coincidentally, some of these proteins, such as myosin II, α-actinins, filamins, and actin, have either altered expression in cancer and/or some type of direct involvement in cancer progression. For this reason, targeting the mechanical system as a therapeutic strategy may lead to more efficacious treatments in the future. However, targeting the mechanical program is far from trivial. As involved as the mechanical program is in cancer development and metastasis, it also helps drive many other key cellular processes, such as cell division, cell adhesion, metabolism, and motility. Therefore, anti-cancer treatments targeting the mechanical program must take great care to avoid potential side effects. Here, we introduce the potential of targeting the mechanical program while also providing its challenges and shortcomings as a strategy for cancer treatment.

Deeper insights into transcriptional features of cancer-associated fibroblasts: An integrated meta-analysis of single-cell and bulk RNA-sequencing data

Cancer-associated fibroblasts (CAFs) have long been known as one of the most important players in tumor initiation and progression. Even so, there is an incomplete understanding of the identification of CAFs among tumor microenvironment cells as the list of CAF marker genes varies greatly in the literature, therefore it is imperative to find a better way to identify reliable markers of CAFs. To this end, we summarized a large number of single-cell RNA-sequencing data of multiple tumor types and corresponding normal tissues. As a result, for 9 different types of cancer, we identified CAF-specific gene expression signatures and found 10 protein markers that showed strongly positive staining of tumor stroma according to the analysis of IHC images from the Human Protein Atlas database. Our results give an insight into selecting the most appropriate combination of cancer-associated fibroblast markers. Furthermore, comparison of different approaches for studying differences between cancer-associated and normal fibroblasts (NFs) illustrates the superiority of transcriptome analysis of fibroblasts obtained from fresh tissue samples. Using single-cell RNA sequencing data, we identified common differences in gene expression patterns between normal and cancer-associated fibroblasts, which do not depend on the type of tumor.

The roles of intratumour heterogeneity in the biology and treatment of pancreatic ductal adenocarcinoma

Intratumour heterogeneity (ITH) has become an important focus of cancer research in recent years. ITH describes the cellular variation that enables tumour evolution, including tumour progression, metastasis and resistance to treatment. The selection and expansion of genetically distinct treatment-resistant cancer cell clones provides one explanation for treatment failure. However, tumour cell variation need not be genetically encoded. In pancreatic ductal adenocarcinoma (PDAC) in particular, the complex tumour microenvironment as well as crosstalk between tumour and stromal cells result in exceptionally variable tumour cell phenotypes that are also highly adaptable. In this review we discuss four different types of phenotypic heterogeneity within PDAC, from morphological to metabolic heterogeneity. We suggest that these different types of ITH are not independent, but, rather, can inform one another. Lastly, we highlight recent findings that suggest how therapeutic efforts may halt PDAC progression by constraining cellular heterogeneity.

Tissue Rigidity Increased during Carcinogenesis of NTCU-Induced Lung Squamous Cell Carcinoma In Vivo

Increased tissue rigidity is an emerging hallmark of cancer as it plays a critical role in promoting cancer growth. However, the field lacks a defined characterization of tissue rigidity in dual-stage carcinogenesis of lung squamous cell carcinoma (SCC) in vivo. Pre-malignant and malignant lung SCC was developed in BALB/c mice using N-nitroso-tris-chloroethylurea (NTCU). Picro sirius red staining and atomic force microscopy were performed to measure collagen content and collagen (diameter and rigidity), respectively. Then, the expression of tenascin C (TNC) protein was determined using immunohistochemistry staining. Briefly, all tissue rigidity parameters were found to be increased in the Cancer group as compared with the Vehicle group. Importantly, collagen content (33.63 ± 2.39%) and TNC expression (7.97 ± 2.04%) were found to be significantly higher (p < 0.05) in the Malignant Cancer group, as compared with the collagen content (18.08 ± 1.75%) and TNC expression (0.45 ± 0.53%) in the Pre-malignant Cancer group, indicating increased tissue rigidity during carcinogenesis of lung SCC. Overall, tissue rigidity of lung SCC was suggested to be increased during carcinogenesis as indicated by the overexpression of collagen and TNC protein, which may warrant further research as novel therapeutic targets to treat lung SCC effectively.

The extracellular matrix alteration, implication in modulation of drug resistance mechanism: friends or foes?

The extracellular matrix (ECM) is an important component of the tumor microenvironment (TME), having several important roles related to the hallmarks of cancer. In cancer, multiple components of the ECM have been shown to be altered. Although most of these alterations are represented by the increased or decreased quantity of the ECM components, changes regarding the functional alteration of a particular ECM component or of the ECM as a whole have been described. These alterations can be induced by the cancer cells directly or by the TME cells, with cancer-associated fibroblasts being of particular interest in this regard. Because the ECM has this wide array of functions in the tumor, preclinical and clinical studies have assessed the possibility of targeting the ECM, with some of them showing encouraging results. In the present review, we will highlight the most relevant ECM components presenting a comprehensive description of their physical, cellular and molecular properties which can alter the therapy response of the tumor cells. Lastly, some evidences regarding important biological processes were discussed, offering a more detailed understanding of how to modulate altered signalling pathways and to counteract drug resistance mechanisms in tumor cells.

Substrate stiffness effect on molecular crosstalk of epithelial-mesenchymal transition mediators of human glioblastoma cells

The complexity of the microenvironment effects on cell response, show accumulating evidence that glioblastoma (GBM) migration and invasiveness are influenced by the mechanical rigidity of their surroundings. The epithelial–mesenchymal transition (EMT) is a well-recognized driving force of the invasive behavior of cancer. However, the primary mechanisms of EMT initiation and progression remain unclear. We have previously showed that certain substrate stiffness can selectively stimulate human GBM U251-MG and GL15 glioblastoma cell lines motility. The present study unifies several known EMT mediators to uncover the reason of the regulation and response to these stiffnesses. Our results revealed that changing the rigidity of the mechanical environment tuned the response of both cell lines through change in morphological features, epithelial-mesenchymal markers (E-, N-Cadherin), EGFR and ROS expressions in an interrelated manner. Specifically, a stiffer microenvironment induced a mesenchymal cell shape, a more fragmented morphology, higher intracellular cytosolic ROS expression and lower mitochondrial ROS. Finally, we observed that cells more motile showed a more depolarized mitochondrial membrane potential. Unravelling the process that regulates GBM cells’ infiltrative behavior could provide new opportunities for identification of new targets and less invasive approaches for treatment.

Mechanical regulation of signal transduction in angiogenesis

Biophysical and biochemical cues work in concert to regulate angiogenesis. These cues guide angiogenesis during development and wound healing. Abnormal cues contribute to pathological angiogenesis during tumor progression. In this review, we summarize the known signaling pathways involved in mechanotransduction important to angiogenesis. We discuss how variation in the mechanical microenvironment, in terms of stiffness, ligand availability, and topography, can modulate the angiogenesis process. We also present an integrated view on how mechanical perturbations, such as stretching and fluid shearing, alter angiogenesis-related signal transduction acutely, leading to downstream gene expression. Tissue engineering-based approaches to study angiogenesis are reviewed too. Future directions to aid the efforts in unveiling the comprehensive picture of angiogenesis are proposed.

The Extracellular Matrix: A Key Accomplice of Cancer Stem Cell Migration, Metastasis Formation, and Drug Resistance in PDAC

Pancreatic ductal adenocarcinoma (PDAC) is rich in dense fibrotic stroma that are composed of extracellular matrix (ECM) proteins. A disruption of the balance between ECM synthesis and secretion and the altered expression of matrix remodeling enzymes lead to abnormal ECM dynamics in PDAC. This pathological ECM promotes cancer growth, survival, invasion, and alters the behavior of fibroblasts and immune cells leading to metastasis formation and chemotherapy resistance, which contribute to the high lethality of PDAC. Additionally, recent evidence highlights that ECM, as a major structural component of the tumor microenvironment, is a highly dynamic structure in which ECM proteins establish a physical and biochemical niche for cancer stem cells (CSCs). CSCs are characterized by self-renewal, tumor initiation, and resistance to chemotherapeutics. In this review, we will discuss the effects of the ECM on tumor biological behavior and its molecular impact on the fundamental signaling pathways in PDAC. We will also provide an overview of how the different ECM components are able to modulate CSCs properties and finally discuss the current and ongoing therapeutic strategies targeting the ECM. Given the many challenges facing current targeted therapies for PDAC, a better understanding of molecular events involving the interplay of ECM and CSC will be key in identifying more effective therapeutic strategies to eliminate CSCs and ultimately to improve survival in patients that are suffering from this deadly disease.

Advances in bioengineering pancreatic tumor-stroma physiomimetic Biomodels

Pancreatic cancer exhibits a unique bioarchitecture and desmoplastic cancer-stoma interplay that governs disease progression, multi-resistance, and metastasis. Emulating the biological features and microenvironment heterogeneity of pancreatic cancer stroma in vitro is remarkably complex, yet highly desirable for advancing the discovery of innovative therapeutics. Diverse bioengineering approaches exploiting patient-derived organoids, cancer-on-a-chip platforms, and 3D bioprinted living constructs have been rapidly emerging in an endeavor to seamlessly recapitulate major tumor-stroma biodynamic interactions in a preclinical setting. Gathering on this, herein we showcase and discuss the most recent advances in bio-assembling pancreatic tumor-stroma models that mimic key disease hallmarks and its desmoplastic biosignature. A reverse engineering perspective of pancreatic tumor-stroma key elementary units is also provided and complemented by a detailed description of biodesign guidelines that are to be considered for improving 3D models physiomimetic features. This overview provides valuable examples and starting guidelines for researchers envisioning to engineer and characterize stroma-rich biomimetic tumor models. All in all, leveraging advanced bioengineering tools for capturing stromal heterogeneity and dynamics, opens new avenues toward generating more predictive and patient-personalized organotypic 3D in vitro platforms for screening transformative therapeutics targeting the tumor-stroma interplay.

Increased Stiffness Downregulates Focal Adhesion Kinase Expression in Pancreatic Cancer Cells Cultured in 3D Self-Assembling Peptide Scaffolds

The focal adhesion kinase (FAK) is a non-receptor tyrosine kinase that participates in integrin-mediated signal transduction and contributes to different biological processes, such as cell migration, survival, proliferation and angiogenesis. Moreover, FAK can be activated by autophosphorylation at position Y397 and trigger different signaling pathways in response to increased extracellular matrix stiffness. In addition, FAK is overexpressed and/or hyperactivated in many epithelial cancers, and its expression correlates with tumor malignancy and invasion potential. One of the characteristics of solid tumors is an over deposition of ECM components, which generates a stiff microenvironment that promotes, among other features, sustained cell proliferation and survival. Researchers are, therefore, increasingly developing cell culture models to mimic the increased stiffness associated with these kinds of tumors. In the present work, we have developed a new 3D in vitro model to study the effect of matrix stiffness in pancreatic ductal adenocarcinoma (PDAC) cells as this kind of tumor is characterized by a desmoplastic stroma and an increased stiffness compared to its normal counterpart. For that, we have used a synthetic self-assembling peptide nanofiber matrix, RAD16-I, which does not suffer a significant degradation in vitro, thus allowing to maintain the same local stiffness along culture time. We show that increased matrix stiffness in synthetic 3D RAD16-I gels, but not in collagen type I scaffolds, promotes FAK downregulation at a protein level in all the cell lines analyzed. Moreover, even though it has classically been described that stiff 3D matrices promote an increase in pFAK^Y397/FAK proteins, we found that this ratio in soft and stiff RAD16-I gels is cell-type-dependent. This study highlights how cell response to increased matrix stiffness greatly depends on the nature of the matrix used for 3D culture.

Collagen XI Alpha 1 Chain, a Novel Therapeutic Target for Cancer Treatment

The extracellular matrix (ECM) plays an important role in the progression of cancer. Collagen is the most abundant component in ECM, and is involved in the biological formation of cancer. Although type XI collagen is a minor fibrillar collagen, collagen XI alpha 1 chain (COL11A1) expression has been found to be upregulated in a variety of human cancers including colorectal, esophagus, glioma, gastric, head and neck, lung, ovarian, pancreatic, salivary gland, and renal cancers. High levels of COL11A1 usually predict poor prognosis, owing to its association with angiogenesis, invasion, and drug resistance in cancer. However, little is known about the specific mechanism through which COL11A1 regulates tumor progression. Here, we have organized and summarized recent developments regarding the interactions between COL11A1 and intracellular signaling pathways and selected therapeutic agents targeting COL11A1, as these indicate its potential as a target for treatment of cancers, especially epithelial ovarian cancer.

The Desmoplastic Stroma of Pancreatic Cancer: Multilayered Levels of Heterogeneity, Clinical Significance, and Therapeutic Opportunities

Simple Summary

Pancreatic cancer is a highly malignant disease with treatment resistance to standardized chemotherapies. In addition, only a small fraction of patients with pancreatic cancer has, to date, actionable genetic aberrations, leading to a narrow therapeutic window for molecularly targeted therapies or immunotherapies. A lot of preclinical and translational studies are ongoing to discover potential vulnerabilities to treat pancreatic cancer. Histologically, human pancreatic cancer is characterized by abundant cancer-associated fibrotic stroma, called “desmoplastic stroma”. Recent technological advances have revealed that desmoplastic stroma in pancreatic cancer is much more complicated than previously thought, playing pleiotropic roles in manipulating tumor cell fate and anti-tumor immunity. Moreover, real-world specimen-based analyses of pancreatic cancer stroma have also uncovered spatial heterogeneity and an intertumoral variety associated with molecular alterations, clinicopathological factors, and patient outcomes. This review describes an overview of the current efforts in the field of pancreatic cancer stromal biology and discusses treatment opportunities of stroma-modifying therapies against this hard-to-treat cancer.

Abstract

Pancreatic cancer remains one of the most lethal malignancies and is becoming a dramatically increasing cause of cancer-related mortality worldwide. Abundant desmoplastic stroma is a histological hallmark of pancreatic ductal adenocarcinoma. Emerging evidence suggests a promising therapeutic effect of several stroma-modifying therapies that target desmoplastic stromal elements in the pancreatic cancer microenvironment. The evidence also unveils multifaceted roles of cancer-associated fibroblasts (CAFs) in manipulating pancreatic cancer progression, immunity, and chemotherapeutic response. Current state-of-the-art technologies, including single-cell transcriptomics and multiplexed tissue imaging techniques, have provided a more profound knowledge of CAF heterogeneity in real-world specimens from pancreatic cancer patients, as well as in genetically engineered mouse models. In this review, we describe recent advances in the understanding of the molecular pathology bases of pancreatic cancer desmoplastic stroma at multilayered levels of heterogeneity, namely, (1) variations in cellular and non-cellular members, including CAF subtypes and extracellular matrix (ECM) proteins; (2) geographical heterogeneity in relation to cell–cell interactions and signaling pathways at niche levels and spatial heterogeneity at locoregional levels or organ levels; and (3) intertumoral stromal heterogeneity at individual levels. This review further discusses the clinicopathological significance of desmoplastic stroma and the potential opportunities for stroma-targeted therapies against this lethal malignancy.

Targeting the tumor biophysical microenvironment to reduce resistance to immunotherapy

Immunotherapy based on immune checkpoint inhibitors has evolved into a new pillar of cancer treatment in clinics, but dealing with treatment resistance (either primary or acquired) is a major challenge. The tumor microenvironment (TME) has a substantial impact on the pathological behaviors and treatment response of many cancers. The biophysical clues in TME have recently been considered as important characteristics of cancer. Furthermore, there is mounting evidence that biophysical cues in TME play important roles in each step of the cascade of cancer immunotherapy that synergistically contribute to immunotherapy resistance. In this review, we summarize five main biophysical cues in TME that affect resistance to immunotherapy: extracellular matrix (ECM) structure, ECM stiffness, tumor interstitial fluid pressure (IFP), solid stress, and vascular shear stress. First, the biophysical factors involved in anti-tumor immunity and therapeutic antibody delivery processes are reviewed. Then, the causes of these five biophysical cues and how they contribute to immunotherapy resistance are discussed. Finally, the latest treatment strategies that aim to improve immunotherapy efficacy by targeting these biophysical cues are shared. This review highlights the biophysical cues that lead to immunotherapy resistance, also supplements their importance in related technologies for studying TME biophysical cues in vitro and therapeutic strategies targeting biophysical cues to improve the effects of immunotherapy.

Effects of substrate stiffness on the viscoelasticity and migration of prostate cancer cells examined by atomic force microscopy

The stiffness of the extracellular matrix of tumour cells plays a key role in tumour cell metastasis. However, it is unclear how mechanical properties regulate the cellular response to the environmental matrix. In this study, atomic force microscopy (AFM) and laser confocal imaging were used to qualitatively evaluate the relationship between substrate stiffness and migration of prostate cancer (PCa) cells. Cells cultured on stiff substrates (35 kPa) undergone several interesting phenomena compared to those on soft substrates (3 kPa). Here, the stimulation generated by the stiff substrates triggered the F-actin skeleton to bundle its filaments, increasing the polarity index of the external contour of PCa cells. Analysis of AFM force-distance curves indicated that the elasticity of the cells cultured on 35 kPa substrates increased while the viscosity decreased. Wound-healing experiments showed that PCa cells cultured on 35 kPa substrates have higher migration potential. These phenomena suggested that the mechanical properties may be correlated with the migration of PCa cells. After actin depolymerisation, the elasticity of the PCa cells decreased while the viscosity increased, and the migration ability was correspondingly decreased. In conclusion, this study clearly demonstrated the relationship between substrate stiffness and the mechanical properties of cells in prostate tumour metastasis, providing a basis for understanding the changes in the biomechanical properties at a single-cell level.

The RAGE/multiligand axis: a new actor in tumor biology

The receptor for advanced glycation end-products (RAGE) is a multiligand binding and single-pass transmembrane protein which actively participates in several chronic inflammation-related diseases. RAGE, in addition to AGEs, has a wide repertoire of ligands, including several damage-associated molecular pattern molecules or alarmins such as HMGB1 and members of the S100 family proteins.

Over the last years, a large and compelling body of evidence has revealed the active participation of the RAGE axis in tumor biology based on its active involvement in several crucial mechanisms involved in tumor growth, immune evasion, dissemination, as well as by sculpturing of the tumor microenvironment as a tumor-supportive niche. In the present review, we will detail the consequences of the RAGE axis activation to fuel essential mechanisms to guarantee tumor growth and spreading.

Biophysics Role and Biomimetic Culture Systems of ECM Stiffness in Cancer EMT

Oncological diseases have become the second leading cause of death from noncommunicable diseases worldwide and a major threat to human health. With the continuous progress in cancer research, the mechanical cues from the tumor microenvironment environment (TME) have been found to play an irreplaceable role in the progression of many cancers. As the main extracellular mechanical signal carrier, extracellular matrix (ECM) stiffness may influence cancer progression through biomechanical transduction to modify downstream gene expression, promote epithelial-mesenchymal transition (EMT), and regulate the stemness of cancer cells. EMT is an important mechanism that induces cancer cell metastasis and is closely influenced by ECM stiffness, either independently or in conjunction with other molecules. In this review, the unique role of ECM stiffness in EMT in different kinds of cancers is first summarized. By continually examining the significance of ECM stiffness in cancer progression, a biomimetic culture system based on 3D manufacturing and novel material technologies is developed to mimic ECM stiffness. The authors then look back on the novel development of the ECM stiffness biomimetic culture systems and finally provide new insights into ECM stiffness in cancer progression which can broaden the fields' horizons with a view toward developing new cancer diagnosis methods and therapies.

Progesterone receptor expression contributes to gemcitabine resistance at higher ECM stiffness in breast cancer cell lines

Chemoresistance poses a great barrier to breast cancer treatment and is thought to correlate with increased matrix stiffness. We developed two-dimensional (2D) polyacrylamide (PAA) and three-dimensional (3D) alginate in vitro models of tissue stiffness that mimic the stiffness of normal breast and breast cancer. We then used these to compare cell viability in response to chemotherapeutic treatment. In both 2D and 3D we observed that breast cancer cell growth and size was increased at a higher stiffness corresponding to tumours compared to normal tissue. When chemotherapeutic response was measured, a specific differential response in cell viability was observed for gemcitabine in 2 of the 7 breast cancer cell lines investigated. MCF7 and T-47D cell lines showed gemcitabine resistance at 4 kPa compared to 500 Pa. These cell lines share a common phenotype of progesterone receptor (PGR) expression and, indeed, pre-treatment with the selective progesterone receptor modulator (SPRM) mifepristone abolished resistance to gemcitabine at high stiffness. Our data reveals that combined treatment with SPRMs may therefore help in reducing resistance to gemcitabine in stiffer breast tumours which are PGR positive.

Resistance to Gemcitabine in Pancreatic Ductal Adenocarcinoma: A Physiopathologic and Pharmacologic Review

Pancreatic ductal adenocarcinoma (PDAC) is a very aggressive tumor with a poor prognosis and inadequate response to treatment. Many factors contribute to this therapeutic failure: lack of symptoms until the tumor reaches an advanced stage, leading to late diagnosis; early lymphatic and hematic spread; advanced age of patients; important development of a pro-tumoral and hyperfibrotic stroma; high genetic and metabolic heterogeneity; poor vascular supply; a highly acidic matrix; extreme hypoxia; and early development of resistance to the available therapeutic options. In most cases, the disease is silent for a long time, andwhen it does become symptomatic, it is too late for ablative surgery; this is one of the major reasons explaining the short survival associated with the disease. Even when surgery is possible, relapsesare frequent, andthe causes of this devastating picture are the low efficacy ofand early resistance to all known chemotherapeutic treatments. Thus, it is imperative to analyze the roots of this resistance in order to improve the benefits of therapy. PDAC chemoresistance is the final product of different, but to some extent, interconnected factors. Surgery, being the most adequate treatment for pancreatic cancer and the only one that in a few selected cases can achieve longer survival, is only possible in less than 20% of patients. Thus, the treatment burden relies on chemotherapy in mostcases. While the FOLFIRINOX scheme has a slightly longer overall survival, it also produces many more adverse eventsso that gemcitabine is still considered the first choice for treatment, especially in combination with other compounds/agents. This review discusses the multiple causes of gemcitabine resistance in PDAC.

Biomechanical Dependence of SARS-CoV-2 Infections

Older people have been disproportionately vulnerable to the current SARS-CoV-2 pandemic, with an increased risk of severe complications and death compared to other age groups. A mix of underlying factors has been speculated to give rise to this differential infection outcome including changes in lung physiology, weakened immunity, and severe immune response. Our study focuses on the impact of biomechanical changes in lungs that occur as individuals age, that is, the stiffening of the lung parenchyma and increased matrix fiber density. We used hydrogels with an elastic modulus of 0.2 and 50 kPa and conventional tissue culture surfaces to investigate how infection rate changes with parenchymal tissue stiffness in lung epithelial cells challenged with SARS-CoV-2 Spike (S) protein pseudotyped lentiviruses. Further, we employed electrospun fiber matrices to isolate the effect of matrix density. Given the recent data highlighting the importance of alternative virulent strains, we included both the native strain identified in early 2020 and an early S protein variant (D614G) that was shown to increase the viral infectivity markedly. Our results show that cells on softer and sparser scaffolds, closer resembling younger lungs, exhibit higher infection rates by the WT and D614G variant. This suggests that natural changes in lung biomechanics do not increase the propensity for SARS-CoV-2 infection and that other factors, such as a weaker immune system, may contribute to increased disease burden in the elderly.

Precise Tuning and Characterization of Viscoelastic Interfaces for the Study of Early Epithelial-Mesenchymal Transition Behaviors

There is growing evidence that cellular functions are regulated by the viscoelastic nature of surrounding matrices. This study aimed to investigate the impact of interfacial viscoelasticity on adhesion and epithelial-mesenchymal transition (EMT) behaviors of epithelial cells. The interfacial viscoelasticity was manipulated using spin-coated thin films composed of copolymers of ε-caprolactone and d,l-lactide photo-cross-linked with benzophenone, whose mechanical properties were characterized using atomic force microscopy and a rheometer. The critical range for the morphological transition of epithelial Madin-Darby canine kidney (MDCK) cells was of the order of 10² ms relaxation time, which was 1-2 orders of magnitude smaller than the relaxation times reported (10-10² s). An analysis of strain rate-dependent viscoelastic properties revealed that the difference was caused by the different strain rate/frequency used for the mechanical characterization of the interface and bulk. Furthermore, decoupling of the interfacial viscous and elastic terms demonstrated that E/N-cadherin expression levels were regulated differently by interfacial relaxation and elasticity. These results confirm the significance of precise manipulation and characterization of interfacial viscoelasticity in mechanobiology studies on EMT progression.

New progress in the mechanism of microenvironment-driven chemoradiotherapy resistance in digestive system tumors

Tumor microenvironment (TME) is the cornerstone of the survival of tumor cells. It generally presents unique physical and chemical characteristics such as hypoxia, immunosuppression, metabolic reprogramming, and matrix stiffening, which not only offer suitable soil to support tumorigenesis and progression, but also resist the effects of radiotherapy and chemotherapy. Here, we summarize new progress in the mechanism of hypoxia, immunosuppression, metabolic reprogramming, and matrix stiffness-driven chemoradiotherapy resistance in digestive system tumors, and discuss the new intervention strategy against matrix stiffness-driven chemoradiotherapy resistance, which underlines the contribution of physical and chemical characteristics of tumor microenvironment in drug resistance.

Locoregional therapies and their effects on the tumoral microenvironment of pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is expected to become the second leading cause of death from cancer by 2030. Despite intensive research in the field of therapeutics, the 5-year overall survival is approximately 8%, with only 20% of patients eligible for surgery at the time of diagnosis. The tumoral microenvironment (TME) of the PDAC is one of the main causes for resistance to antitumoral treatments due to the presence of tumor vasculature, stroma, and a modified immune response. The TME of PDAC is characterized by high stiffness due to fibrosis, with hypo microvascular perfusion, along with an immunosuppressive environment that constitutes a barrier to effective antitumoral treatment. While systemic therapies often produce severe side effects that can alter patients' quality of life, locoregional therapies have gained attention since their action is localized to the pancreas and can thus alleviate some of the barriers to effective antitumoral treatment due to their physical effects. Local hyperthermia using radiofrequency ablation and radiation therapy - most commonly using a local high single dose - are the two main modalities holding promise for clinical efficacy. Recently, irreversible electroporation and focused ultrasound-derived cavitation have gained increasing attention. To date, most of the data are limited to preclinical studies, but ongoing clinical trials may help better define the role of these locoregional therapies in the management of PDAC patients.

Targeting extracellular matrix stiffness and mechanotransducers to improve cancer therapy

Cancer microenvironment is critical for tumorigenesis and cancer progression. The extracellular matrix (ECM) interacts with tumor and stromal cells to promote cancer cells proliferation, migration, invasion, angiogenesis and immune evasion. Both ECM itself and ECM stiffening-induced mechanical stimuli may activate cell membrane receptors and mechanosensors such as integrin, Piezo1 and TRPV4, thereby modulating the malignant phenotype of tumor and stromal cells. A better understanding of how ECM stiffness regulates tumor progression will contribute to the development of new therapeutics. The rapidly expanding evidence in this research area suggests that the regulators and effectors of ECM stiffness represent potential therapeutic targets for cancer. This review summarizes recent work on the regulation of ECM stiffness in cancer, the effects of ECM stiffness on tumor progression, cancer immunity and drug resistance. We also discuss the potential targets that may be druggable to intervene ECM stiffness and tumor progression. Based on these advances, future efforts can be made to develop more effective and safe drugs to interrupt ECM stiffness-induced oncogenic signaling, cancer progression and drug resistance.

Current Advances in 3D Bioprinting for Cancer Modeling and Personalized Medicine

Tumor cells evolve in a complex and heterogeneous environment composed of different cell types and an extracellular matrix. Current 2D culture methods are very limited in their ability to mimic the cancer cell environment. In recent years, various 3D models of cancer cells have been developed, notably in the form of spheroids/organoids, using scaffold or cancer-on-chip devices. However, these models have the disadvantage of not being able to precisely control the organization of multiple cell types in complex architecture and are sometimes not very reproducible in their production, and this is especially true for spheroids. Three-dimensional bioprinting can produce complex, multi-cellular, and reproducible constructs in which the matrix composition and rigidity can be adapted locally or globally to the tumor model studied. For these reasons, 3D bioprinting seems to be the technique of choice to mimic the tumor microenvironment in vivo as closely as possible. In this review, we discuss different 3D-bioprinting technologies, including bioinks and crosslinkers that can be used for in vitro cancer models and the techniques used to study cells grown in hydrogels; finally, we provide some applications of bioprinted cancer models.

Substrate Stiffness-Driven Membrane Tension Modulates Vesicular Trafficking via Caveolin-1

Liver fibrosis, a condition characterized by extensive deposition and cross-linking of extracellular matrix (ECM) proteins, is idiosyncratic in cases of chronic liver injury. The dysregulation of ECM remodeling by hepatic stellate cells (HSCs), the main mediators of fibrosis, results in an elevated ECM stiffness that drives the development of chronic liver disease such as cirrhosis and hepatocellular carcinoma. Tissue inhibitor of matrix metalloproteinase-1 (TIMP-1) is a key element in the regulation of ECM remodeling, which modulates the degradation and turnover of ECM components. We have previously reported that a rigid, fibrotic-like substrate can impact TIMP-1 expression at the protein level in HSCs without altering its mRNA expression. While HSCs are known to be highly susceptible to mechanical stimuli, the mechanisms through which mechanical cues regulate TIMP-1 at the post-translational level remain unclear. Here, we show a mechanism of regulation of plasma membrane tension by matrix stiffness. We found that this effect is orchestrated by the β1 integrin/RhoA axis and results in elevated exocytosis and secretion of TIMP-1 in a caveolin-1- and dynamin-2-dependent manner. We then show that TIMP-1 and caveolin-1 expression increases in cirrhosis and hepatocellular carcinoma. These conditions are associated with fibrosis, and this effect can be recapitulated in 3D fibrosis models consisting of hepatic stellate cells encapsulated in a self-assembling polypeptide hydrogel. This work positions stiffness-dependent membrane tension as a key regulator of enzyme secretion and function and a potential target for therapeutic strategies that aim at modulating ECM remodeling in chronic liver disease.

Sequestration of Intestinal Acidic Toxins by Cationic Resin Attenuates Pancreatic Cancer Progression through Promoting Autophagic Flux for YAP Degradation

Simple Summary

Annually, more than 450,000 people are diagnosed with pancreatic cancer worldwide with over 430,000 mortalities. Pancreatic ductal carcinoma (PDAC) accounts for around 80% of pancreatic cancer cases with an extremely high mortality rate. Emerging research has demonstrated that gut dysbiosis is closely associated with pancreatic cancer, while the underlying mechanisms remain elusive. In this study, we found that elevated levels of endotoxin (LPS) and bile acids were associated with malignant progression in Kras-driven pancreatic cancer mice. Importantly, oral administration of cationic resins to sequestrate intestinal endotoxins and bile acids efficiently attenuated tumor progression. Thus, sequestration of intestinal acidic toxins by oral administration of cationic resins may have potential as an intervention strategy for pancreatic malignancy.

Abstract

Pancreatic cancer is driven by risk factors such as diabetes and chronic pancreatic injury, which are further associated with gut dysbiosis. Intestinal toxins such as bile acids and bacterial endotoxin (LPS), in excess and persistence, can provoke chronic inflammation and tumorigenesis. Of interest is that many intestinal toxins are negatively charged acidic components in essence, which prompted us to test whether oral administration of cationic resin can deplete intestinal toxins and ameliorate pancreatic cancer. Here, we found that increased plasma levels of endotoxin and bile acids in Pdx1-Cre: LSL-Kras^G12D/+ mice were associated with the transformation of the pancreatic ductal carcinoma (PDAC) state. Common bile-duct-ligation or LPS injection impeded autolysosomal flux, leading to Yap accumulation and malignant transformation. Conversely, oral administration of cholestyramine to sequestrate intestinal endotoxin and bile acids resumed autolysosomal flux for Yap degradation and attenuated metastatic incidence. Conversely, chloroquine treatment impaired autolysosomal flux and exacerbated malignance, showing jeopardization of p62/ Sqxtm1 turnover, leading to Yap accumulation, which is also consistent with overexpression of cystatin A (CSTA) in situ with pancreatic cancer cells and metastatic tumor. At cellular levels, chenodeoxycholic acid or LPS treatment activated the ligand–receptor-mediated AKT-mTOR pathway, resulting in autophagy-lysosomal stress for YAP accumulation and cellular dissemination. Thus, this work indicates a potential new strategy for intervention of pancreatic metastasis through sequestration of intestinal acidic toxins by oral administration of cationic resins.

Epithelial to mesenchymal transition during mammalian neural crest cell delamination

Epithelial to mesenchymal transition (EMT) is a well-defined cellular process that was discovered in chicken embryos and described as "epithelial to mesenchymal transformation" [1]. During EMT, epithelial cells lose their epithelial features and acquire mesenchymal character with migratory potential. EMT has subsequently been shown to be essential for both developmental and pathological processes including embryo morphogenesis, wound healing, tissue fibrosis and cancer [2]. During the past 5 years, interest and study of EMT especially in cancer biology have increased exponentially due to the implied role of EMT in multiple aspects of malignancy such as cell invasion, survival, stemness, metastasis, therapeutic resistance and tumor heterogeneity [3]. Since the process of EMT in embryogenesis and cancer progression shares similar phenotypic changes, core transcription factors and molecular mechanisms, it has been proposed that the initiation and development of carcinoma could be attributed to abnormal activation of EMT factors usually required for normal embryo development. Therefore, developmental EMT mechanisms, whose timing, location, and tissue origin are strictly regulated, could prove useful for uncovering new insights into the phenotypic changes and corresponding gene regulatory control of EMT under pathological conditions. In this review, we initially provide an overview of the phenotypic and molecular mechanisms involved in EMT and discuss the newly emerging concept of epithelial to mesenchymal plasticity (EMP). Then we focus on our current knowledge of a classic developmental EMT event, neural crest cell (NCC) delamination, highlighting key differences in our understanding of NCC EMT between mammalian and non-mammalian species. Lastly, we highlight available tools and future directions to advance our understanding of mammalian NCC EMT.

Exosome-delivered CD44v6/C1QBP complex drives pancreatic cancer liver metastasis by promoting fibrotic liver microenvironment

OBJECTIVE

Pancreatic ductal adenocarcinoma (PDAC) shows a remarkable predilection for liver metastasis. Pro-oncogenic secretome delivery and trafficking via exosomes are crucial for pre-metastatic microenvironment formation and metastasis. This study aimed to explore the underlying mechanisms of how PDAC-derived exosomes (Pex) modulate the liver microenvironment and promote metastasis.

DESIGN

C57BL/6 mice were 'educated' by tail vein Pex injection. The intrasplenic injection liver metastasis and PDAC orthotopic transplantation models were used to evaluate liver metastasis. Stable cell lines CD44v6 (CD44 variant isoform 6) or C1QBP (complement C1q binding protein) knockdown or overexpression was established using lentivirus transfection or gateway systems. A total of 142 patients with PDAC in Huashan Hospital were retrospectively enrolled. Prognosis and liver metastasis were predicted using Kaplan-Meier survival curves and logistic regression models.

RESULTS

Pex tail vein injection induced the deposition of liver fibrotic extracellular matrix, which promoted PDAC liver metastasis. Specifically, the exosomal CD44v6/C1QBP complex was delivered to the plasma membrane of hepatic satellite cells (HSCs), leading to phosphorylation of insulin-like growth factor 1 signalling molecules, which resulted in HSC activation and liver fibrosis. Expression of Pex CD44v6 and C1QBP in PDAC patients with liver metastasis was significantly higher than in PDAC patients without liver metastasis, and simultaneous high expression of exosomal CD44v6 and C1QBP correlated with a worse prognosis and a higher risk of postoperative PDAC liver metastasis.

CONCLUSION

The Pex-derived CD44v6/C1QBP complex is essential for the formation of a fibrotic liver microenvironment and PDAC liver metastasis. Highly expressed exosomal CD44v6 and C1QBP are promising biomarkers for predicting prognosis and liver metastasis in patients with PDAC.

Modeling the mechanical stiffness of pancreatic ductal adenocarcinoma

•

The PDAC stroma stiffness underlines its malignant behavior and drug resistance.

•

3D in vitro cultures must model the PDAC stroma to effectively drug efficacy.

•

PSCs are responsible for the stroma, and its activity is increased with TGF-β.

•

Develop a 3D culture model of PDAC, which includes PSCs and TGF-β.

•

Assess the mechanical stiffness, stain for collagen, and investigate gemcitabine efficacy.

Despite improvements in the understanding of disease biology, pancreatic ductal adenocarcinoma (PDAC) remains the most malignant cancer of the pancreas. PDAC constitutes ∼95% of all pancreatic cancers, and it is highly resistant to therapeutics. The increased tissue rigidity, which stems from the rich fibrotic stroma in the tumor microenvironment, is central to disease development, physiology, and resistance to drug perfusion. Pancreatic stellate cells (PSCs) are responsible for overproduction of extracellular matrix in the fibrotic stroma, and this is exacerbated by the overexpression of transforming growth factor-β (TGF-β). However, there are few in vitro PDAC models, which include both PSCs and TGF-β or mimic in vivo-like tumor stiffness. In this study, we present a three-dimensional in vitro PDAC model, which includes PSCs and TGF-β, and recapitulates PDAC tissue mechanical stiffness. Using oscillatory shear rheology, we show the mechanical stiffness of the model is within range of the PDAC tissue stiffness by day 21 of culture and highlight that the matrix environment is essential to adequately capture PDAC disease. PDAC is a complex, aggressive disease with poor prognosis, and biophysically relevant in vitro PDAC models, which take into account tissue mechanics, will provide improved tumor models for effective therapeutic assessment.

Mechanomimetic 3D Scaffolds as a Humanized In Vitro Model for Ovarian Cancer

The mechanical homeostasis of tissues can be altered in response to trauma or disease, such as cancer, resulting in altered mechanotransduction pathways that have been shown to impact tumor development, progression, and the efficacy of therapeutic approaches. Specifically, ovarian cancer progression is parallel to an increase in tissue stiffness and fibrosis. With in vivo models proving difficult to study, tying tissue mechanics to altered cellular and molecular properties necessitate advanced, tunable, in vitro 3D models able to mimic normal and tumor mechanic features. First, we characterized normal human ovary and high-grade serous (HGSC) ovarian cancer tissue stiffness to precisely mimic their mechanical features on collagen I-based sponge scaffolds, soft (NS) and stiff (MS), respectively. We utilized three ovarian cancer cell lines (OVCAR-3, Caov-3, and SKOV3) to evaluate changes in viability, morphology, proliferation, and sensitivity to doxorubicin and liposomal doxorubicin treatment in response to a mechanically different microenvironment. High substrate stiffness promoted the proliferation of Caov-3 and SKOV3 cells without changing their morphology, and upregulated mechanosensors YAP/TAZ only in SKOV3 cells. After 7 days in culture, both OVCAR3 and SKOV3 decreased the MS scaffold storage modulus (stiffness), suggesting a link between cell proliferation and the softening of the matrix. Finally, high matrix stiffness resulted in higher OVCAR-3 and SKOV3 cell cytotoxicity in response to doxorubicin. This study demonstrates the promise of biomimetic porous scaffolds for effective inclusion of mechanical parameters in 3D cancer modeling. Furthermore, this work establishes the use of porous scaffolds for studying ovarian cancer cells response to mechanical changes in the microenvironment and as a meaningful platform from which to investigate chemoresistance and drug response.