Human pancreatic stellate cells modulate 3D collagen alignment to promote the migration of pancreatic ductal adenocarcinoma cells

Imaging at the nexus: how state of the art imaging techniques can enhance our understanding of cancer and fibrosis

Both cancer and fibrosis are diseases involving dysregulation of cell signaling pathways resulting in an altered cellular microenvironment which ultimately leads to progression of the condition. The two disease entities share common molecular pathophysiology and recent research has illuminated the how each promotes the other. Multiple imaging techniques have been developed to aid in the early and accurate diagnosis of each disease, and given the commonalities between the pathophysiology of the conditions, advances in imaging one disease have opened new avenues to study the other. Here, we detail the most up-to-date advances in imaging techniques for each disease and how they have crossed over to improve detection and monitoring of the other. We explore techniques in positron emission tomography (PET), magnetic resonance imaging (MRI), second generation harmonic Imaging (SGHI), ultrasound (US), radiomics, and artificial intelligence (AI). A new diagnostic imaging tool in PET/computed tomography (CT) is the use of radiolabeled fibroblast activation protein inhibitor (FAPI). SGHI uses high-frequency sound waves to penetrate deeper into the tissue, providing a more detailed view of the tumor microenvironment. Artificial intelligence with the aid of advanced deep learning (DL) algorithms has been highly effective in training computer systems to diagnose and classify neoplastic lesions in multiple organs. Ultimately, advancing imaging techniques in cancer and fibrosis can lead to significantly more timely and accurate diagnoses of both diseases resulting in better patient outcomes.

CCK Receptor Inhibition Reduces Pancreatic Tumor Fibrosis and Promotes Nanoparticle Delivery

The poor prognosis for pancreatic ductal adenocarcinoma (PDAC) patients is due in part to the highly fibrotic nature of the tumors that impedes delivery of therapeutics, including nanoparticles (NPs). Our prior studies demonstrated that proglumide, a cholecystokinin receptor (CCKR) antagonist, reduced fibrosis pervading PanIN lesions in mice. Here, we further detail how the reduced fibrosis elicited by proglumide achieves the normalization of the desmoplastic tumor microenvironment (TME) and improves nanoparticle uptake. One week following the orthotopic injection of PDAC cells, mice were randomized to normal or proglumide-treated water for 3-6 weeks. Tumors were analyzed ex vivo for fibrosis, vascularity, stellate cell activation, vascular patency, and nanoparticle distribution. The histological staining and three-dimensional imaging of tumors each indicated a reduction in stromal collagen in proglumide-treated mice. Proglumide treatment increased tumor vascularity and decreased the activation of cancer-associated fibroblasts (CAFs). Additionally, PANC-1 cells with the shRNA-mediated knockdown of the CCK2 receptor showed an even greater reduction in collagen, indicating the CCK2 receptors on tumor cells contribute to the desmoplastic TME. Proglumide-mediated reduction in fibrosis also led to functional changes in the TME as evidenced by the enhanced intra-tumoral distribution of small (<12 nm) Rhodamine-loaded nanoparticles. The documented in vivo, tumor cell-intrinsic anti-fibrotic effects of CCK2R blockade in both an immunocompetent syngeneic murine PDAC model as well as a human PDAC xenograft model demonstrates that CCK2R antagonists, such as proglumide, can improve the delivery of nano-encapsulated therapeutics or imaging agents to pancreatic tumors.

The Effect of Intratumor Heterogeneity in Pancreatic Ductal Adenocarcinoma Progression and Treatment

BACKGROUND AND OBJECTIVES

Pancreatic cancer is one of the most lethal malignancies. Even though many substantial improvements in the survival rates for other major cancer forms were made, pancreatic cancer survival rates have remained relatively unchanged since the 1960s. Even more, no standard classification system for pancreatic cancer is based on cellular biomarkers. This review will discuss and provide updates about the role of stem cells in the progression of PC, the genetic changes associated with it, and the promising biomarkers for diagnosis.

MATERIALS AND METHODS

The search process used PubMed, Cochrane Library, and Scopus databases to identify the relevant and related articles. Articles had to be published in English to be considered.

RESULTS

The increasing number of studies in recent years has revealed that the diversity of cancer-associated fibroblasts is far greater than previously acknowledged, which highlights the need for further research to better understand the various cancer-associated fibroblast subpopulations. Despite the huge diversity in pancreatic cancer, some common features can be noted to be shared among patients. Mutations involving CDKN2, P53, and K-RAS can be seen in a big number of patients, for example. Similarly, some patterns of genes and biomarkers expression and the level of their expression can help in predicting cancer behavior such as metastasis and drug resistance. The current trend in cancer research, especially with the advancement in technology, is to sequence everything in hopes of finding disease-related mutations.

CONCLUSION

Optimizing pancreatic cancer treatment requires clear classification, understanding CAF roles, and exploring stroma reshaping approaches.

High serum levels of the C-propetide of type V collagen (PRO-C5) are prognostic for short overall survival in patients with pancreatic ductal adenocarcinoma

Introduction: Pancreatic ductal adenocarcinoma (PDAC) is characterized by a pronounced fibrotic tumor microenvironment, which impairs treatment response. Type I and V collagens are responsible for the densely packed fibrils in the tumor fibrosis environment. While the role of the major type I collagen in cancer is well described, less is known about the minor type V collagen. Quantifying collagen propeptides in serum has been shown to have prognostic and predictive value. In this study, we evaluated the clinical utility of measuring the propeptide of type V collagen (PRO-C5) in serum from a discovery cohort and a validation cohort of patients with PDAC as well as in non-pancreatic solid tumor types to explore the relevance of the PRO-C5 biomarker in cancer.

Methods: Serum PRO-C5 was measured in three cohorts: a discovery cohort (19 healthy controls, 12 patients with chronic pancreatitis and 33 patients with PDAC (stage I-IV)), a validation cohort (800 patients with PDAC (stage I-IV)), and a non-pancreatic solid tumor type cohort of 33 healthy controls and 200 patients with 10 different non-pancreatic solid tumor types. The levels of serum PRO-C5 in patients with cancer were compared to levels in healthy controls. The association between PRO-C5 levels and overall survival (OS) was evaluated in patients with PDAC after adjusting for established prognostic factors.

Results: PRO-C5 was significantly increased in serum from patients with PDAC compared to healthy controls (p &lt; 0.001). High PRO-C5 levels were significantly associated with short OS in both the discovery- and the validation cohort, especially in early stages of PDAC (validation cohort stage II, HR = 2.0, 95%CI1.2-3.4). The association was independent of other prognostic parameters including stage, performance status and CA19-9. Furthermore, serum levels of PRO-C5 were significantly increased in serum from patients with other non-pancreatic solid tumor types compared to healthy controls.

Conclusion: High levels of serum PRO-C5 is prognostic for short OS in patients with PDAC and may provide clinical value in many other tumor types beyond PDAC. This underlines the importance of type V collagen in tumor fibrosis. PRO-C5 could have the potential to be used in several aspects within drug discovery, patient stratification and drug efficacy.

Multiscale anisotropy analysis of second-harmonic generation collagen imaging of human pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is one of the deadliest cancers with a minority (< 10%) of patients surviving five years past diagnosis. This could be improved with the development of new imaging modalities for early differentiation of benign and cancerous fibrosis. This study intends to explore the application of a two-photon microscopy technique known as second harmonic generation to PDAC using the 2D Wavelet Transform Modulus Maxima (WTMM) Anisotropy method to quantify collagen organization in fibrotic pancreatic tissue. Forty slides from PDAC patients were obtained and eight images were captured per each tissue category on each slide. Brownian surface motion and white noise images were generated for calibration and testing of a new variable binning approach to the 2D WTMM Anisotropy method. The variable binning method had greater resistance to wavelet scaling effects and white noise images were found to have the lowest anisotropy factor. Cancer and fibrosis had greater anisotropy factors (Fa) at small wavelet scales than normal and normal adjacent tissue. At a larger scale of 21 μm this relationship changed with normal tissue having a higher Fa than all other tissue groups. White noise is the best representative image for isotropy and the 2D WTMM anisotropy method is sensitive to changes induced in collagen by PDAC.

Predictive value of collagen in cancer

Cancer is a complex disease and a significant cause of mortality worldwide. Over the course of nearly all cancer types, collagen within the tumor microenvironment influences emergence, progression, and metastasis. This review discusses collagen regulation within the tumor microenvironment, pathological involvement of collagen, and predictive values of collagen and related extracellular matrix components in main cancer types. A survey of predictive tests leveraging collagen assays using clinical cohorts is presented. A conclusion is that collagen has high predictive value in monitoring cancer processes and stratifying by outcomes. New approaches should be considered that continue to define molecular facets of collagen related to cancer.

Collagen Biomarkers Quantify Fibroblast Activity In Vitro and Predict Survival in Patients with Pancreatic Ductal Adenocarcinoma

The use of novel tools to understand tumour-fibrosis in pancreatic ductal adenocarcinoma (PDAC) and novel anti-fibrotic treatments are highly needed. We established a pseudo-3D in vitro model including humane pancreatic fibroblasts (PFs) and pancreatic cancer-associated fibroblasts (CAFs) in combination with clinical collagen biomarkers, as a translational anti-fibrotic drug screening tool. Furthermore, we investigated the prognostic potential of serum collagen biomarkers in 810 patients with PDAC. PFs and CAFs were cultured in Ficoll-media. Cells were treated w/wo TGF-ß1 and the anti-fibrotic compound ALK5i. Biomarkers measuring the formation of type III (PRO-C3) and VI (PRO-C6) collagens were measured by ELISA in supernatant at days 3, 6, 9, and 12. PRO-C3 and PRO-C6, and their association with overall survival (OS), were evaluated in serum with PDAC (n = 810). PRO-C3 and PRO-C6 were upregulated in CAFs compared to PFs (p < 0.0001.). TGF-ß1 increased PRO-C3 in both PFs and CAFs (p < 0.0001). The anti-fibrotic compound ALK5i inhibited both PRO-C3 and PRO-C6 (p < 0.0001). High serum levels of PRO-C3 and PRO-C6 in patients with PDAC were associated with short OS (PRO-C3: HR = 1.48, 95%CI: 1.29-1.71, p < 0.0001 and PRO-C6: HR = 1.31, 95%CI: 1.14-1.50, p = 0.0002). PRO-C3 and PRO-C6 have the potential to be used both pre-clinically and clinically as a measure of tumor fibrosis and CAF activity.

Disruption of pancreatic stellate cell myofibroblast phenotype promotes pancreatic tumor invasion

In pancreatic ductal adenocarcinoma (PDAC), differentiation of pancreatic stellate cells (PSCs) into myofibroblast-like cancer-associated fibroblasts (CAFs) can both promote and suppress tumor progression. Here, we show that the Rho effector protein kinase N2 (PKN2) is critical for PSC myofibroblast differentiation. Loss of PKN2 is associated with reduced PSC proliferation, contractility, and alpha-smooth muscle actin (α-SMA) stress fibers. In spheroid co-cultures with PDAC cells, loss of PKN2 prevents PSC invasion but, counter-intuitively, promotes invasive cancer cell outgrowth. PKN2 deletion induces a myofibroblast to inflammatory CAF switch in the PSC matrisome signature both in vitro and in vivo. Further, deletion of PKN2 in the pancreatic stroma induces more locally invasive, orthotopic pancreatic tumors. Finally, we demonstrate that a PKN2KO matrisome signature predicts poor outcome in pancreatic and other solid human cancers. Our data indicate that suppressing PSC myofibroblast function can limit important stromal tumor-suppressive mechanisms, while promoting a switch to a cancer-supporting CAF phenotype.

3D modeling in cancer studies

The tumor microenvironment contributes significantly to tumor initiation, progression, and resistance to chemotherapy. Much of our understanding of the tumor and its microenvironment is developed using various methods of cell culture. Throughout the last two decades, research has increasingly shown that 3D cell culture systems can remarkably recapitulate the complexity of tumor architecture and physiology compared to traditional 2D models. Unlike the flat culture system, these novel models enabled more cell-cell and cell-extracellular matrix interactions. By mimicking in vivo microenvironment, 3D culture systems promise to become accurate tools ready to be used in diagnosis, drug screening, and personalized medicine. In this review, we discussed the importance of 3D culture in simulating the tumor microenvironment and focused on the effects of cancer cell-microenvironment interactions on cancer behavior, resistance, proliferation, and metastasis. Finally, we assessed the role of 3D cell culture systems in the contexts of drug screening. 2D culture system is used to study cancer cell growth, progression, behavior, and drug response. It provides contact between cells and supports paracrine crosstalk between host cells and cancer cells. However, this system fails to simulate the architecture and the physiological aspects of in vivo tumor microenvironment due to the absence of cell-cell/ cell-ECM interactions as well as unlimited access to O₂ and nutrients, and the absence of tumor heterogeneity. Recently advanced research has led researchers to generate 3D culture system that can better recapitulate the in vivo environment by providing hypoxic medium, facilitating cell-cell and cell-ECM, interactions, and recapitulating heterogeneity of the tumor. Several approaches are used to maintain and expand cancer cells in 3D culture systems such as tumor spheroids (cell aggregate that mimics the in vivo growth of tumor cells), scaffold-based approaches, bioreactors, microfluidic derives, and organoids. 3D systems are currently used for disease modeling and pre-clinical drug testing.

Collagen Organization Does Not Influence T-Cell Distribution in Stroma of Human Pancreatic Cancer

Simple Summary

The excessive desmoplasia is the hallmark of human pancreatic cancer that influences the local T-cell-based immune response. In the present work, the stromal collagen organization in normal and malignant pancreatic tissues as well as its relationsship to T-cell distribution in pancreatic cancer were studied. It was found that differences in collagen organization do not change the spatial orientation of T-cell migration and do not influence the availability of tumor cells for T-cells. The results of the study do not support the concept of use of stroma collagen organization for improvement of spatial T-cell distribution in the tumor.

Abstract

The dominant intrastromal T-cell infiltration in pancreatic cancer is mainly caused by the contact guidance through the excessive desmoplastic reaction and could represent one of the obstacles to an effective immune response in this tumor type. This study analyzed the collagen organization in normal and malignant pancreatic tissues as well as its influence on T-cell distribution in pancreatic cancer. Human pancreatic tissue was analyzed using immunofluorescence staining and multiphoton and SHG microscopy supported by multistep image processing. The influence of collagen alignment on activated T-cells was studied using 3D matrices and time-lapse microscopy. It was found that the stroma of malignant and normal pancreatic tissues was characterized by complex individual organization. T-cells were heterogeneously distributed in pancreatic cancer and there was no relationship between T-cell distribution and collagen organization. There was a difference in the angular orientation of collagen alignment in the peritumoral and tumor-cell-distant stroma regions in the pancreatic ductal adenocarcinoma tissue, but there was no correlation in the T-cell densities between these regions. The grade of collagen alignment did not influence the directionality of T-cell migration in the 3D collagen matrix. It can be concluded that differences in collagen organization do not change the spatial orientation of T-cell migration or influence stromal T-cell distribution in human pancreatic cancer. The results of the present study do not support the rationale of remodeling of stroma collagen organization for improvement of T-cell–tumor cell contact in pancreatic ductal adenocarcinoma.

Stroma Involvement in Pancreatic Ductal Adenocarcinoma: An Overview Focusing on Extracellular Matrix Proteins

Pancreatic cancer is the seventh leading cause of cancer-related deaths worldwide and is predicted to become second in 2030 in industrialized countries if no therapeutic progress is made. Among the different types of pancreatic cancers, Pancreatic Ductal Adenocarcinoma (PDAC) is by far the most represented one with an occurrence of more than 90%. This specific cancer is a devastating malignancy with an extremely poor prognosis, as shown by the 5-years survival rate of 2–9%, ranking firmly last amongst all cancer sites in terms of prognostic outcomes for patients. Pancreatic tumors progress with few specific symptoms and are thus at an advanced stage at diagnosis in most patients. This malignancy is characterized by an extremely dense stroma deposition around lesions, accompanied by tissue hypovascularization and a profound immune suppression. Altogether, these combined features make access to cancer cells almost impossible for conventional chemotherapeutics and new immunotherapeutic agents, thus contributing to the fatal outcomes of the disease. Initially ignored, the Tumor MicroEnvironment (TME) is now the subject of intensive research related to PDAC treatment and could contain new therapeutic targets. In this review, we will summarize the current state of knowledge in the field by focusing on TME composition to understand how this specific compartment could influence tumor progression and resistance to therapies. Attention will be paid to Tenascin-C, a matrix glycoprotein commonly upregulated during cancer that participates to PDAC progression and thus contributes to poor prognosis.

Tumor extracellular matrix: lessons from the second-harmonic generation microscopy

Extracellular matrix (ECM) represents more than a mere intercellular cement. It is physiologically active in cell communication, adhesion and proliferation. Collagen is the most abundant protein, making up to 90% of ECM, and 30% of total protein weight in humans. Second-harmonic generation (SHG) microscopy represents an important tool to study collagen organization of ECM in freshly unfixed tissues and paraffin-embedded tissue samples. This manuscript aims to review some of the applications of SHG microscopy in Oncologic Pathology, mainly in the study of ECM of epithelial tumors. It is shown how collagen parameters measured by this technique can aid in the differential diagnosis and in prognostic stratification. There is a tendency to associate higher amount, lower organization and higher linearity of collagen fibers with tumor progression and metastasizing. These represent complex processes, in which matrix remodeling plays a central role, together with cancer cell genetic modifications. Integration of studies on cancer cell biology and ECM are highly advantageous to give us a more complete picture of these processes. As microscopic techniques provide topographic information allied with biologic characteristics of tissue components, they represent important tools for a more complete understanding of cancer progression. In this context, SHG has provided significant insights in human tumor specimens, readily available for Pathologists.

Exosomal integrins and their influence on pancreatic cancer progression and metastasis

As one of the most lethal and untreatable types of cancer so far, pancreatic cancer is not benefitting from advancements in research. Despite all the efforts, this malignancy is still very difficult to diagnose in time, resistant to treatments, and prone to relapses. The appearance of metastasis-notoriously difficult to fight and a signal of unfortunate prognosis-is the event most dreaded by every cancer patient, especially by those with pancreatic cancer. Strategies for early detection and treatment of metastases are limited, and new action plans are desperately awaited. Recently, the importance of cell-secreted vesicles, or exosomes, in cell-cell communication and, particularly, their key role in promoting pathological conditions, such as infectious diseases and cancer, have attracted the attention of the scientific community. The discovery of some exosome membrane components, such as adhesion receptors and integrins, and their ability to influence cancer cell functions and metastasis progression, has added some important understanding of the metastatic process and will hopefully open the door to the development of new tools for identifying and targeting metastases. The aim of this review is to discuss the role played by integrins in exosomal-mediated pancreatic cancer progression and metastasis.

Morphological Heterogeneity in Pancreatic Cancer Reflects Structural and Functional Divergence

Simple Summary

Pancreatic cancer has a poor prognosis, which is largely due to resistance to treatment. Tumor heterogeneity is a known cause for treatment failure and has been studied at the molecular level. Morphological heterogeneity is common but has not been investigated, despite the fact that pathology examination is an integral part of clinical diagnostics. This study assessed whether morphological heterogeneity reflects structural and functional diversity in key cancer biological processes. Using archival tissues from resected pancreatic cancer, we selected four common and distinct morphological phenotypes and demonstrated that these differed significantly for a panel of 26 structural and functional features of the cancer-cell and stromal compartments. The strong link between these features and morphological phenotypes allowed prediction of the latter based on the results for the panel of features. The findings of this study indicate that morphological heterogeneity reflects biological diversity and that its assessment may potentially provide clinically relevant information.

Abstract

Inter- and intratumor heterogeneity is an important cause of treatment failure. In human pancreatic cancer (PC), heterogeneity has been investigated almost exclusively at the genomic and transcriptional level. Morphological heterogeneity, though prominent and potentially easily assessable in clinical practice, remains unexplored. This proof-of-concept study aims at demonstrating that morphological heterogeneity reflects structural and functional divergence. From the wide morphological spectrum of conventional PC, four common and distinctive patterns were investigated in 233 foci from 39 surgical specimens. Twenty-six features involved in key biological processes in PC were analyzed (immuno-)histochemically and morphometrically: cancer cell proliferation (Ki67) and migration (collagen fiber alignment, MMP14), cancer stem cells (CD44, CD133, ALDH1), amount, composition and spatial arrangement of extracellular matrix (epithelial proximity, total collagen, collagen I and III, fibronectin, hyaluronan), cancer-associated fibroblasts (density, αSMA), and cancer-stroma interactions (integrins α2, α5, α1; caveolin-1). All features differed significantly between at least two of the patterns. Stromal and cancer-cell-related features co-varied with morphology and allowed prediction of the morphological pattern. In conclusion, morphological heterogeneity in the cancer-cell and stromal compartments of PC correlates with structural and functional diversity. As such, histopathology has the potential to inform on the operationality of key biological processes in individual tumors.

Cancer associated fibroblast: Mediators of tumorigenesis

It is well accepted that the tumor microenvironment plays a pivotal role in cancer onset, development, and progression. The majority of clinical interventions are designed to target either cancer or stroma cells. These emphases have been directed by one of two prevailing theories in the field, the Somatic Mutation Theory and the Tissue Organization Field Theory, which represent two seemingly opposing concepts. This review proposes that the two theories are mutually inclusive and should be concurrently considered for cancer treatments. Specifically, this review discusses the dynamic and reciprocal processes between stromal cells and extracellular matrices, using pancreatic cancer as an example, to demonstrate the inclusivity of the theories. Furthermore, this review highlights the functions of cancer associated fibroblasts, which represent the major stromal cell type, as important mediators of the known cancer hallmarks that the two theories attempt to explain.

A Novel Scaffold-Based Hybrid Multicellular Model for Pancreatic Ductal Adenocarcinoma-Toward a Better Mimicry of the in vivo Tumor Microenvironment

With a very low survival rate, pancreatic ductal adenocarcinoma (PDAC) is a deadly disease. This has been primarily attributed to (i) its late diagnosis and (ii) its high resistance to current treatment methods. The latter specifically requires the development of robust, realistic in vitro models of PDAC, capable of accurately mimicking the in vivo tumor niche. Advancements in the field of tissue engineering (TE) have helped the development of such models for PDAC. Herein, we report for the first time a novel hybrid, polyurethane (PU) scaffold-based, long-term, multicellular (tri-culture) model of pancreatic cancer involving cancer cells, endothelial cells, and stellate cells. Recognizing the importance of ECM proteins for optimal growth of different cell types, the model consists of two different zones/compartments: an inner tumor compartment consisting of cancer cells [fibronectin (FN)-coated] and a surrounding stromal compartment consisting of stellate and endothelial cells [collagen I (COL)-coated]. Our developed novel hybrid, tri-culture model supports the proliferation of all different cell types for 35 days (5 weeks), which is the longest reported timeframe in vitro. Furthermore, the hybrid model showed extensive COL production by the cells, mimicking desmoplasia, one of PDAC's hallmark features. Fibril alignment of the stellate cells was observed, which attested to their activated state. All three cell types expressed various cell-specific markers within the scaffolds, throughout the culture period and showed cellular migration between the two zones of the hybrid scaffold. Our novel model has great potential as a low-cost tool for in vitro studies of PDAC, as well as for treatment screening.

3D approaches to model the tumor microenvironment of pancreatic cancer

In tumor engineering, 3D approaches are used to model components of the tumor microenvironment and to test new treatments. Pancreatic cancers are a cancer of substantial unmet need and survival rates are lower compared to any other cancer. Bioengineering techniques are increasingly applied to understand the unique biology of pancreatic tumors and to design patient-specific models. Here we summarize how extracellular and cellular elements of the pancreatic tumor microenvironment and their interactions have been studied in 3D cell cultures. We review selected clinical trials, assess the benefits of therapies interfering with the tumor microenvironment and address their limitations and future perspectives.

Pancreatic stellate cells: Aiding and abetting pancreatic cancer progression

Tumour-stromal interactions have now been acknowledged to play a major role in pancreatic cancer (PC) progression. The abundant collagenous stroma is produced by a specific cell type in the pancreas-the pancreatic stellate cell (PSC). Pancreatic stellate cells (PSCs) are a unique resident cell type of pancreas and with a critical role in both healthy and diseased pancreas. Accumulating evidence indicates that PSCs interact closely with cancer cells as well as with other cell types of the stroma such as immune cells, endothelial cells and neuronal cells, to set up a growth permissive microenvironment for pancreatic tumours, which facilitates local tumour growth as well as distant metastasis. Consequently, recent work in the field has focused on the development of novel therapeutic approaches targeting the stroma to inhibit PC progression. Such a multi-pronged approach targeting both tumour and stromal elements of PC has been successfully applied in pre-clinical settings. The challenge now is to translate the pre-clinical findings into the clinical setting to achieve better outcomes for pancreatic cancer patients.

Extracellular matrix anisotropy is determined by TFAP2C-dependent regulation of cell collisions

The isotropic or anisotropic organization of biological extracellular matrices has important consequences for tissue function. We study emergent anisotropy using fibroblasts that generate varying degrees of matrix alignment from uniform starting conditions. This reveals that the early migratory paths of fibroblasts are correlated with subsequent matrix organization. Combined experimentation and adaptation of Vicsek modelling demonstrates that the reorientation of cells relative to each other following collision plays a role in generating matrix anisotropy. We term this behaviour 'cell collision guidance'. The transcription factor TFAP2C regulates cell collision guidance in part by controlling the expression of RND3. RND3 localizes to cell-cell collision zones where it downregulates actomyosin activity. Cell collision guidance fails without this mechanism in place, leading to isotropic matrix generation. The cross-referencing of alignment and TFAP2C gene expression signatures against existing datasets enables the identification and validation of several classes of pharmacological agents that disrupt matrix anisotropy.

The Extracellular, Cellular, and Nuclear Stiffness, a Trinity in the Cancer Resistome-A Review

Alterations in mechano-physiological properties of a tissue instigate cancer burdens in parallel to common genetic and epigenetic alterations. The chronological and mechanistic interrelation between the various extra- and intracellular aspects remains largely elusive. Mechano-physiologically, integrins and other cell adhesion molecules present the main mediators for transferring and distributing forces between cells and the extracellular matrix (ECM). These cues are channeled via focal adhesion proteins, termed the focal adhesomes, to cytoskeleton and nucleus and vice versa thereby affecting the pathophysiology of multicellular cancer tissues. In combination with simultaneous activation of diverse downstream signaling pathways, the phenotypes of cancer cells are created and driven characterized by deregulated transcriptional and biochemical cues that elicit the hallmarks of cancer. It, however, remains unclear how elastostatic modifications, i.e., stiffness, in the extracellular, intracellular, and nuclear compartment contribute and control the resistance of cancer cells to therapy. In this review, we discuss how stiffness of unique tumor components dictates therapy response and what is known about the underlying molecular mechanisms.

NAD(P)H fluorescence lifetime measurements in fixed biological tissues

Autofluorescence based fluorescence lifetime imaging microscopy (AF-FLIM) techniques have come a long way from early studies on cancer characterization and have now been widely employed in several cellular and animal studies covering a wide range of diseases. The majority of research in autofluorescence imaging (AFI) study metabolic fluxes in live biological samples. However, tissues from clinical or scientific studies are often chemically fixed for preservation and stabilization of tissue morphology. Fixation is particularly crucial for enzymatic, functional, or histopathology studies. Interpretations of metabolic imaging such as optical redox intensity imaging and AF-FLIM, have often been viewed as potentially unreliable in a fixed sample due to lack of studies in this field. In this study, we carefully evaluate the possibility of extracting microenvironment information in fixed tissues using reduced nicotinamide adenine dinucleotide (phosphate) (NAD(P)H) endogenous fluorescence. The ability to distinguish changes such as metabolism and pH using intrinsic fluorescence in fixed tissues has great pathological value. In this work, we show that the lifetime based metabolic contrast in a sample is preserved after chemical fixation. The fluorescence lifetime of a sample increases with an additive fixative like formaldehyde; however, the fixed tissues retain metabolic signatures even after fixation. This study presents an opportunity to successfully image archived unstained histopathology tissues, and generate useful AF-FLIM signatures. We demonstrate the capability to draw metabolic interpretations in fixed tissues even after long periods of storage.

Rigidity controls human desmoplastic matrix anisotropy to enable pancreatic cancer cell spread via extracellular signal-regulated kinase 2

It is predicted that pancreatic ductal adenocarcinoma (PDAC) will become the second most lethal cancer in the US by 2030. PDAC includes a fibrous-like stroma, desmoplasia, encompassing most of the tumor mass, which is produced by cancer-associated fibroblasts (CAFs) and includes their cell-derived extracellular matrices (CDMs). Since elimination of desmoplasia has proven detrimental to patients, CDM reprogramming, as opposed to stromal ablation, is therapeutically desirable. Hence, efforts are being made to harness desmoplasia's anti-tumor functions. We conducted biomechanical manipulations, using variations of pathological and physiological substrates in vitro, to culture patient-harvested CAFs and generate CDMs that restrict PDAC growth and spread. We posited that extrinsic modulation of the environment, via substrate rigidity, influences CAF's cell-intrinsic forces affecting CDM production. Substrates used were polyacrylamide gels of physiological (~1.5 kPa) or pathological (~7 kPa) stiffnesses. Results showed that physiological substrates influenced CAFs to generate CDMs similar to normal/control fibroblasts. We found CDMs to be softer than the corresponding underlying substrates, and CDM fiber anisotropy (i.e., alignment) to be biphasic and informed via substrate-imparted morphological CAF aspect ratios. The biphasic nature of CDM fiber anisotropy was mathematically modeled and proposed a correlation between CAF aspect ratios and CDM alignment; regulated by extrinsic and intrinsic forces to conserve minimal free energy. Biomechanical manipulation of CDMs, generated on physiologically soft substrates, leads to reduction in nuclear translocation of pERK1/2 in KRAS mutated pancreatic cells. ERK2 was found essential for CDM-regulated tumor cell spread. In vitro findings correlated with in vivo observations; nuclear pERK1/2 is significantly high in human PDAC samples. The study suggests that altering underlying substrates enable CAFs to remodel CDMs and restrict pancreatic cancer cell spread in an ERK2 dependent manner.

A multiscale Mueller polarimetry module for a stereo zoom microscope

Mueller polarimetry is a quantitative polarized light imaging modality that is capable of label-free visualization of tissue pathology, does not require extensive sample preparation, and is suitable for wide-field tissue analysis. It holds promise for selected applications in biomedicine, but polarimetry systems are often constrained by limited end-user accessibility and/or long-imaging times. In order to address these needs, we designed a multiscale-polarimetry module that easily couples to a commercially available stereo zoom microscope. This paper describes the module design and provides initial polarimetry imaging results from a murine preclinical breast cancer model and human breast cancer samples. The resultant polarimetry module has variable resolution and field of view, is low-cost, and is simple to switch in or out of a commercial microscope. The module can reduce long imaging times by adopting the main imaging approach used in pathology: scanning at low resolution to identify regions of interest, then at high resolution to inspect the regions in detail. Preliminary results show how the system can aid in region of interest identification for pathology, but also highlight that more work is needed to understand how tissue structures of pathological interest appear in Mueller polarimetry images across varying spatial zoom scales.

Degradation and Remodeling of Epitaxially Grown Collagen Fibrils

INTRODUCTION—

The extracellular matrix (ECM) in the tumor microenvironment contains high densities of collagen that are highly aligned, resulting in directional migration called contact guidance that facilitates efficient migration out of the tumor. Cancer cells can remodel the ECM through traction force controlled by myosin contractility or proteolytic activity controlled by matrix metalloproteinase (MMP) activity, leading to either enhanced or diminished contact guidance.

METHODS—

Recently, we have leveraged the ability of mica to epitaxially grow aligned collagen fibrils in order to assess contact guidance. In this article, we probe the mechanisms of remodeling of aligned collagen fibrils on mica by breast cancer cells.

RESULTS—

We show that cells that contact guide with high fidelity (MDA-MB-231 cells) exert more force on the underlying collagen fibrils than do cells that contact guide with low fidelity (MTLn3 cells). These high traction cells (MDA-MB-231 cells) remodel collagen fibrils over hours, pulling so hard that the collagen fibrils detach from the surface, effectively delaminating the entire contact guidance cue. Myosin or MMP inhibition decreases this effect. Interestingly, blocking MMP appears to increase the alignment of cells on these substrates, potentially allowing the alignment through myosin contractility to be uninhibited. Finally, amplification or dampening of contact guidance with respect to a particular collagen fibril organization is seen under different conditions.

CONCLUSIONS—

Both myosin II contractility and MMP activity allow MDA-MB-231 cells to remodel and eventually destroy epitaxially grown aligned collagen fibrils.

Targeting Pancreatic Stellate Cells in Cancer

Pancreatic stellate cells (PSCs) are the major contributor to the aggressive, metastatic, and resilient nature of pancreatic ductal adenocarcinoma (PDAC), which has a poor prognosis with a 5-year survival rate of 8%. PSCs constitute more than 50% of the tumor stroma in PDAC, where they induce extensive desmoplasia by secreting abundant extracellular matrix (ECM) proteins. In addition, they establish dynamic crosstalk with cancer cells and other stromal cells, which collectively supports tumor progression via various inter- and intracellular pathways. These cellular interactions and associated pathways may reveal novel therapeutic opportunities against this unmet clinical problem. In this review article, we discuss the role of PSCs in inducing tumor progression, their crosstalk with other cells, and therapeutic strategies to target PSCs.

Every step of the way: integrins in cancer progression and metastasis

Cell adhesion to the extracellular matrix is fundamental to tissue integrity and human health. Integrins are the main cellular adhesion receptors that through multifaceted roles as signalling molecules, mechanotransducers and key components of the cell migration machinery are implicated in nearly every step of cancer progression from primary tumour development to metastasis. Altered integrin expression is frequently detected in tumours, where integrins have roles in supporting oncogenic growth factor receptor (GFR) signalling and GFR-dependent cancer cell migration and invasion. In addition, integrins determine colonization of metastatic sites and facilitate anchorage-independent survival of circulating tumour cells. Investigations describing integrin engagement with a growing number of versatile cell surface molecules, including channels, receptors and secreted proteins, continue to lead to the identification of novel tumour-promoting pathways. Integrin-mediated sensing, stiffening and remodelling of the tumour stroma are key steps in cancer progression supporting invasion, acquisition of cancer stem cell characteristics and drug resistance. Given the complexity of integrins and their adaptable and sometimes antagonistic roles in cancer cells and the tumour microenvironment, therapeutic targeting of these receptors has been a challenge. However, novel approaches to target integrins and antagonism of specific integrin subunits in stringently stratified patient cohorts are emerging as potential ways forward.

How to Hit Mesenchymal Stromal Cells and Make the Tumor Microenvironment Immunostimulant Rather Than Immunosuppressive

Experimental evidence indicates that mesenchymal stromal cells (MSCs) may regulate tumor microenvironment (TME). It is conceivable that the interaction with MSC can influence neoplastic cell functional behavior, remodeling TME and generating a tumor cell niche that supports tissue neovascularization, tumor invasion and metastasization. In addition, MSC can release transforming growth factor-beta that is involved in the epithelial-mesenchymal transition of carcinoma cells; this transition is essential to give rise to aggressive tumor cells and favor cancer progression. Also, MSC can both affect the anti-tumor immune response and limit drug availability surrounding tumor cells, thus creating a sort of barrier. This mechanism, in principle, should limit tumor expansion but, on the contrary, often leads to the impairment of the immune system-mediated recognition of tumor cells. Furthermore, the cross-talk between MSC and anti-tumor lymphocytes of the innate and adaptive arms of the immune system strongly drives TME to become immunosuppressive. Indeed, MSC can trigger the generation of several types of regulatory cells which block immune response and eventually impair the elimination of tumor cells. Based on these considerations, it should be possible to favor the anti-tumor immune response acting on TME. First, we will review the molecular mechanisms involved in MSC-mediated regulation of immune response. Second, we will focus on the experimental data supporting that it is possible to convert TME from immunosuppressive to immunostimulant, specifically targeting MSC.

Pancreatic stellate cells: what's new?

PURPOSE OF REVIEW

Pancreatic stellate cells (PSCs) play an integral role in the pathogenesis of pancreatitis and pancreatic cancer. With the developing knowledge of this important cell type, we are at the cusp of developing effective therapies for the above diseases based upon targeting the PSC and modulating its function.

RECENT FINDINGS

The major themes of the recent PSC literature include: PSC interactions with the extracellular matrix and other stromal components; intracellular calcium physiology as drivers of mechanical interactions and necrosis; the relationship between proinflammatory, protumoural, angiogenic, and metabolic pathways in pancreatic necrosis, fibrosis, and carcinogenesis; and targeting of the stroma for antitumoural and antifibrotic effects.

SUMMARY

Traditionally, there have been few treatment options for pancreatitis and pancreatic cancer. The elucidation of the wide-ranging functions of PSCs provide an opportunity for treatments based on stromal reprogramming.

A mechanopharmacology approach to overcome chemoresistance in pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is a highly chemoresistant malignancy. This chemoresistant phenotype has been historically associated with genetic factors. Major biomedical research efforts were concentrated that resulted in the identification of subtypes characterized by specific genetic lesions and gene expression signatures that suggest important biological differences. However, to date, these distinct differences could not be exploited for therapeutic interventions. Apart from these genetic factors, desmoplasia and tumor microenvironment have been recognized as key contributors to PDAC chemoresistance. However, while several strategies targeting tumor-stroma have been explored including drugs against members of the Hedgehog family, they failed to meet the expectations in the clinical setting. These unsatisfactory clinical results suggest that, an important link between genetics and the influence of tumor microenvironment on PDAC chemoresistance remains to be elucidated. In this respect, mechanobiology is an emerging multidisciplinary field that encompasses cell and developmental biology as well as biophysics and bioengineering. Herein we provide a comprehensive overview of the key players in pancreatic cancer chemoresistance from the perspective of mechanobiology, and discuss novel experimental avenues such as elastic micropillar arrays that could provide fresh insights for the development of mechanobiology-targeted therapeutic approaches (know as mechanopharmacology) to overcome anticancer drug resistance in pancreatic cancer.

Chemotherapy and tumor microenvironment of pancreatic cancer

Pancreatic cancer is an extremely dismal malignance. Chemotherapy has been widely applied to treat this intractable tumor. It has exclusive tumor microenvironment (TME), characterized by dense desmoplasia and profound infiltrations of immunosuppressive cells. Interactions between stromal cells and cancer cells play vital roles to affect the biological behaviors of pancreatic cancer. Targeting the stromal components of pancreatic cancer has shown promising results. In addition to the direct toxic effects of chemotherapeutic drugs on cancer cells, they can also remodel the TME, eventually affecting their efficacy. Herein, we reviewed the following four aspects; (1) clinical landmark advances of chemotherapy in pancreatic cancer, since 2000; (2) interactions and mechanisms between stromal cells and pancreatic cancer cells; (3) remodeling effects and mechanisms of chemotherapy on TME; (4) targeting stromal components in pancreatic cancer.

Increased dermal collagen bundle alignment in systemic sclerosis is associated with a cell migration signature and role of Arhgdib in directed fibroblast migration on aligned ECMs

Systemic sclerosis (SSc) is a devastating disease affecting the skin and internal organs. Dermal fibrosis manifests early and Modified Rodnan Skin Scores (MRSS) correlate with disease progression. Transcriptomics of SSc skin biopsies suggest the role of the in vivo microenvironment in maintaining the pathological myofibroblasts. Therefore, defining the structural changes in dermal collagen in SSc patients could inform our understanding of fibrosis pathogenesis. Here, we report a method for quantitative whole-slide image analysis of dermal collagen from SSc patients, and our findings of more aligned dermal collagen bundles in diffuse cutaneous SSc (dcSSc) patients. Using the bleomycin-induced mouse model of SSc, we identified a distinct high dermal collagen bundle alignment gene signature, characterized by a concerted upregulation in cell migration, adhesion, and guidance pathways, and downregulation of spindle, replication, and cytokinesis pathways. Furthermore, increased bundle alignment induced a cell migration gene signature in fibroblasts in vitro, and these cells demonstrated increased directed migration on aligned ECM fibers that is dependent on expression of Arhgdib (Rho GDP-dissociation inhibitor 2). Our results indicate that increased cell migration is a cellular response to the increased collagen bundle alignment featured in fibrotic skin. Moreover, many of the cell migration genes identified in our study are shared with human SSc skin and may be new targets for therapeutic intervention.