Christiana Polydorou

Remodeling components of the tumor microenvironment to enhance cancer therapy

Solid tumor pathophysiology is characterized by an abnormal microenvironment that guides tumor progression and poses barriers to the efficacy of cancer therapies. Most common among tumor types are abnormalities in the structure of the tumor vasculature and stroma. Remodeling the tumor microenvironment with the aim to normalize any aberrant properties has the potential to improve therapy. In this review, we discuss structural abnormalities of the tumor microenvironment and summarize the therapeutic strategies that have been developed to normalize tumors as well as their potential to enhance therapy. Finally, we present different in vitro models that have been developed to analyze and better understand the effects of the tumor microenvironment on cancer cell behavior.

Pirfenidone normalizes the tumor microenvironment to improve chemotherapy

Normalization of the tumor microenvironment by selectively targeting components of the tumor extracellular matrix has been recently proposed to have the potential to decompress tumor blood vessels, increase vessel perfusion and thus, improve drug delivery and the efficacy of cancer therapy. Therefore, we now need to identify safe and well tolerated pharmaceutical agents that are able to remodel the microenvironment of solid tumors and enhance chemotherapy. In this study, we repurposed Pirfenidone, a clinically approved anti-fibrotic drug for the treatment of idiopathic pulmonary fibrosis, to investigate its possible role on tumor microenvironment normalization. Using two orthotopic mammary tumor models we demonstrate that Pirfenidone reduces collagen and hyaluronan levels and, as a result, significantly increases blood vessel functionality and perfusion and improves the anti-tumor efficacy of doxorubicin. Reduction of extracellular matrix components were mediated via TGFβ signaling pathway inhibition due to downregulation of TGFβ1, COL1A1, COL3A1, HAS2, HAS3 expression levels. Our findings provide evidence that repurposing Pirfenidone could be used as a promising strategy to enhance drug delivery to solid tumors by normalizing the tumor microenvironment.

Hyaluronan-Derived Swelling of Solid Tumors, the Contribution of Collagen and Cancer Cells, and Implications for Cancer Therapy

Despite the important role that mechanical forces play in tumor growth and therapy, the contribution of swelling to tumor mechanopathology remains unexplored. Tumors rich in hyaluronan exhibit a highly negative fixed charge density. Repulsive forces among these negative charges as well as swelling of cancer cells due to regulation of intracellular tonicity can cause tumor swelling and development of stress that might compress blood vessels, compromising tumor perfusion and drug delivery. Here, we designed an experimental strategy, using four orthotopic tumor models, to measure swelling stress and related swelling to extracellular matrix components, hyaluronan and collagen, as well as to tumor perfusion. Subsequently, interventions were performed to measure tumor swelling using matrix-modifying enzymes (hyaluronidase and collagenase) and by repurposing pirfenidone, an approved antifibrotic drug. Finally, in vitro experiments on cancer cell spheroids were performed to identify their contribution to tissue swelling. Swelling stress was measured in the range of 16 to 75 mm Hg, high enough to cause vessel collapse. Interestingly, while depletion of hyaluronan decreased swelling, collagen depletion had the opposite effect, whereas the contribution of cancer cells was negligible. Furthermore, histological analysis revealed the same linear correlation between tumor swelling and the ratio of hyaluronan to collagen content when data from all tumor models were combined. Our data further revealed an inverse relation between tumor perfusion and swelling, suggesting that reduction of swelling decompresses tumor vessels. These results provide guidelines for emerging therapeutic strategies that target the tumor microenvironment to alleviate intratumoral stresses and improve vessel functionality and drug delivery.

Tranilast-induced stress alleviation in solid tumors improves the efficacy of chemo- and nanotherapeutics in a size-independent manner

Accumulation of mechanical stresses during cancer progression can induce blood and lymphatic vessel compression, creating hypo-perfusion, hypoxia and interstitial hypertension which decrease the efficacy of chemo- and nanotherapies. Stress alleviation treatment has been recently proposed to reduce mechanical stresses in order to decompress tumor vessels and improve perfusion and chemotherapy. However, it remains unclear if it improves the efficacy of nanomedicines, which present numerous advantages over traditional chemotherapeutic drugs. Furthermore, we need to identify safe and well-tolerated pharmaceutical agents that reduce stress levels and may be added to cancer patients’ treatment regimen. Here, we show mathematically and with a series of in vivo experiments that stress alleviation improves the delivery of drugs in a size-independent manner. Importantly, we propose the repurposing of tranilast, a clinically approved anti-fibrotic drug as stress-alleviating agent. Using two orthotopic mammary tumor models, we demonstrate that tranilast reduces mechanical stresses, decreases interstitial fluid pressure (IFP), improves tumor perfusion and significantly enhances the efficacy of different-sized drugs, doxorubicin, Abraxane and Doxil, by suppressing TGFβ signaling and expression of extracellular matrix components. Our findings strongly suggest that repurposing tranilast could be directly used as a promising strategy to enhance, not only chemotherapy, but also the efficacy of cancer nanomedicine.

Ets2-dependent trophoblast signalling is required for gastrulation progression after primitive streak initiation

Although extraembryonic ectoderm trophoblast signals the embryo for primitive streak initiation, a prerequisite for gastrulation, it is unknown whether it also signals for the progression of gastrulation after primitive streak initiation. Here, using Ets2-/- mice, we show that trophoblast signalling is also required in vivo for primitive streak elongation, completion of intraembryonic mesoderm epithelial-mesenchymal transition and the development of anterior primitive streak derivatives such as the node. We show that Ets2-dependent trophoblast signalling is required for the maintenance of high levels of Nodal and Wnt3 expression in the epiblast and for the induction of Snail expression in the primitive streak, between embryonic day 6.3 and 6.7. Within extraembryonic ectoderm trophoblast, Ets2 maintains the expression of the transcription factors Elf5, Cdx2 and Eomes, and that of the signalling molecule Bmp4. We propose a model that provides a genetic explanation as to how Ets2 in trophoblast mediates the progression of gastrulation within the epiblast.

Sonic-hedgehog pathway inhibition normalizes desmoplastic tumor microenvironment to improve chemo- and nanotherapy

Abstract Targeting the rich extracellular matrix of desmoplastic tumors has been successfully shown to normalize collagen and hyaluronan levels and re‐engineer intratumoral mechanical forces, improving tumor perfusion and chemotherapy. As far as targeting the abundant cancer‐associated fibroblasts (CAFs) in desmoplastic tumors is concerned, while both pharmacologic inhibition of the sonic‐hedgehog pathway and genetic depletion of fibroblasts have been employed in pancreatic cancers, the results between the two methods have been contradictory. In this study, we employed vismodegib to inhibit the sonic‐hedgehog pathway with the aim to i) elucidate the mechanism of how CAFs depletion improves drug delivery, ii) extent and evaluate the potential use of sonic‐hedgehog inhibitors to breast cancers, and iii) investigate whether sonic‐hedgehog inhibition improves not only chemotherapy, but also the efficacy of the most commonly used breast cancer nanomedicines, namely Abraxane® and Doxil®. We found that treatment with vismodegib normalizes the tumor microenvironment by reducing the proliferative CAFs and in cases the levels of collagen and hyaluronan. These modulations re‐engineered the solid and fluid stresses in the tumors, improving blood vessel functionality. As a result, the delivery and efficacy of chemotherapy was improved in two models of pancreatic cancer. Additionally, vismodegib treatment significantly improved the efficacy of both Abraxane and Doxil in xenograft breast tumors. Our results suggest the use of vismodegib, and sonic hedgehog inhibitors in general, to enhance cancer chemo‐ and nanotherapy. Graphical abstract Vismodegib normalizes cancer‐associated fibroblasts and tumor extracellular fibers, improving the delivery of chemotherapeutics and nanomedicines in pancreatic and breast cancers. Figure. No Caption available.

Remodeling of extracellular matrix due to solid stress accumulation during tumor growth

Abstract Solid stresses emerge as the expanding tumor displaces and deforms the surrounding normal tissue, and also as a result of intratumoral component interplay. Among other things, solid stresses are known to induce extensive extracellular matrix synthesis and reorganization. In this study, we developed a mathematical model of tumor growth that distinguishes the contribution to stress generation by collagenous and non-collagenous tumor structural components, and also investigates collagen fiber remodeling exclusively due to solid stress. To this end, we initially conducted in vivo experiments using an orthotopic mouse model for breast cancer to monitor primary tumor growth and derive the mechanical properties of the tumor. Subsequently, we fitted the mathematical model to experimental data to determine values of the model parameters. According to the model, intratumoral solid stress is compressive, whereas extratumoral stress in the tumor vicinity is compressive in the radial direction and tensile in the periphery. Furthermore, collagen fibers engaged in stress generation only in the peritumoral region, and not in the interior where they were slackened due to the compressive stress state. Peritumoral fibers were driven away from the radial direction, tended to realign tangent to the tumor–host interface, and were also significantly stretched by tensile circumferential stresses. By means of this remodeling, the model predicts that the tumor is enveloped by a progressively thickening capsule of collagen fibers. This prediction is consistent with long-standing observations of tumor encapsulation and histologic sections that we performed, and it further corroborates the expansive growth hypothesis for the capsule formation.

Semi-Interpenetrating Polymer Networks with Predefined Architecture for Metal Ion Fluorescence Monitoring

The development of new synthetic approaches for the preparation of efficient 3D luminescent chemosensors for transition metal ions receives considerable attention nowadays, owing to the key role of the latter as elements in biological systems and their harmful environmental effects when present in aquatic media. In this work, we describe an easy and versatile synthetic methodology that leads to the generation of nonconjugated 3D luminescent semi-interpenetrating amphiphilic networks (semi-IPN) with structure-defined characteristics. More precisely, the synthesis involves the encapsulation of well-defined poly(9-anthrylmethyl methacrylate) (pAnMMA) (hydrophobic, luminescent) linear polymer chains within a covalent poly(2-(dimethylamino)ethyl methacrylate) (pDMAEMA) hydrophilic polymer network, derived via the 1,2-bis-(2-iodoethoxy)ethane (BIEE)-induced crosslinking process of well-defined pDMAEMA linear chains. Characterization of their fluorescence properties demonstrated that these materials act as strong blue emitters when exposed to UV irradiation. This, combined with the presence of the metal-binding tertiary amino functionalities of the pDMAEMA segments, allowed for their applicability as sorbents and fluorescence chemosensors for transition metal ions (Fe3+, Cu2+) in solution via a chelation-enhanced fluorescence-quenching effect promoted within the semi-IPN network architecture. Ethylenediaminetetraacetic acid (EDTA)-induced metal ion desorption and thus material recyclability has been also demonstrated.

Author Correction: The epigenetic modifier Fam208a is required to maintain epiblast cell fitness

A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has been fixed in the paper.

The epigenetic modifier Fam208a is required to maintain epiblast cell fitness

Gastrulation initiates with the formation of the primitive streak, during which, cells of the epiblast delaminate to form the mesoderm and definitive endoderm. At this stage, the pluripotent cell population of the epiblast undergoes very rapid proliferation and extensive epigenetic programming. Here we show that Fam208a, a new epigenetic modifier, is essential for early post-implantation development. We show that Fam208a mutation leads to impaired primitive streak elongation and delayed epithelial-to-mesenchymal transition. Fam208a mutant epiblasts had increased expression of p53 pathway genes as well as several pluripotency-associated long non-coding RNAs. Fam208a mutants exhibited an increase in p53-driven apoptosis and complete removal of p53 could partially rescue their gastrulation block. This data demonstrates a new in vivo function of Fam208a in maintaining epiblast fitness, establishing it as an important factor at the onset of gastrulation when cells are exiting pluripotency.