The extracellular matrix as hallmark of cancer and metastasis: From biomechanics to therapeutic targets

The extracellular matrix (ECM) is essential for cell support during homeostasis and plays a critical role in cancer. Although research often concentrates on the tumor's cellular aspect, attention is growing for the importance of the cancer-associated ECM. Biochemical and physical ECM signals affect tumor formation, invasion, metastasis, and therapy resistance. Examining the tumor microenvironment uncovers intricate ECM dysregulation and interactions with cancer and stromal cells. Anticancer therapies targeting ECM sensors and remodelers, including integrins and matrix metalloproteinases, and ECM-remodeling cells, have seen limited success. This review explores the ECM's role in cancer and discusses potential therapeutic strategies for cell-ECM interactions.

Epithelial and stromal co-evolution and complicity in pancreatic cancer

Pancreatic ductal adenocarcinomas are distinguished by their robust desmoplasia, or fibroinflammatory response. Dominated by non-malignant cells, the mutated epithelium must therefore combat, cooperate with or co-opt the surrounding cells and signalling processes in its microenvironment. It is proposed that an invasive pancreatic ductal adenocarcinoma represents the coordinated evolution of malignant and non-malignant cells and mechanisms that subvert and repurpose normal tissue composition, architecture and physiology to foster tumorigenesis. The complex kinetics and stepwise development of pancreatic cancer suggests that it is governed by a discrete set of organizing rules and principles, and repeated attempts to target specific components within the microenvironment reveal self-regulating mechanisms of resistance. The histopathological and genetic progression models of the transforming ductal epithelium must therefore be considered together with a programme of stromal progression to create a comprehensive picture of pancreatic cancer evolution. Understanding the underlying organizational logic of the tumour to anticipate and pre-empt the almost inevitable compensatory mechanisms will be essential to eradicate the disease.

The complex interactions between the cellular and non-cellular components of the brain tumor microenvironmental landscape and their therapeutic implications

Glioblastoma (GBM), an aggressive high-grade glial tumor, is resistant to therapy and has a poor prognosis due to its universal recurrence rate. GBM cells interact with the non-cellular components in the tumor microenvironment (TME), facilitating their rapid growth, evolution, and invasion into the normal brain. Herein we discuss the complexity of the interactions between the cellular and non-cellular components of the TME and advances in the field as a whole. While the stroma of non-central nervous system (CNS) tissues is abundant in fibrillary collagens, laminins, and fibronectin, the normal brain extracellular matrix (ECM) predominantly includes proteoglycans, glycoproteins, and glycosaminoglycans, with fibrillary components typically found only in association with the vasculature. However, recent studies have found that in GBMs, the microenvironment evolves into a more complex array of components, with upregulated collagen gene expression and aligned fibrillary ECM networks. The interactions of glioma cells with the ECM and the degradation of matrix barriers are crucial for both single-cell and collective invasion into neighboring brain tissue. ECM-regulated mechanisms also contribute to immune exclusion, resulting in a major challenge to immunotherapy delivery and efficacy. Glioma cells chemically and physically control the function of their environment, co-opting complex signaling networks for their own benefit, resulting in radio- and chemo-resistance, tumor recurrence, and cancer progression. Targeting these interactions is an attractive strategy for overcoming therapy resistance, and we will discuss recent advances in preclinical studies, current clinical trials, and potential future clinical applications. In this review, we also provide a comprehensive discussion of the complexities of the interconnected cellular and non-cellular components of the microenvironmental landscape of brain tumors to guide the development of safe and effective therapeutic strategies against brain cancer.

Deep learning identification of stiffness markers in breast cancer

While essential to our understanding of solid tumor progression, the study of cell and tissue mechanics has yet to find traction in the clinic. Determining tissue stiffness, a mechanical property known to promote a malignant phenotype in vitro and in vivo, is not part of the standard algorithm for the diagnosis and treatment of breast cancer. Instead, clinicians routinely use mammograms to identify malignant lesions and radiographically dense breast tissue is associated with an increased risk of developing cancer. Whether breast density is related to tumor tissue stiffness, and what cellular and non-cellular components of the tumor contribute the most to its stiffness are not well understood. Through training of a deep learning network and mechanical measurements of fresh patient tissue, we create a bridge in understanding between clinical and mechanical markers. The automatic identification of cellular and extracellular features from hematoxylin and eosin (H&E)-stained slides reveals that global and local breast tissue stiffness best correlate with the percentage of straight collagen. Importantly, the percentage of dense breast tissue does not directly correlate with tissue stiffness or straight collagen content.

Current Limitations and Novel Perspectives in Pancreatic Cancer Treatment

Simple Summary

This review article presents a synopsis of the key clinical developments, their limitations, and future perspectives in the treatment of pancreatic cancer. In the first part, we summarize the available treatments for pancreatic cancer patients according to tumor stage, as well as the most relevant clinical trials over the past two decades. Despite this progress, there is still much to be improved in terms of patient survival. Therefore, in the second part, we consider various components of the tumor microenvironment in pancreatic cancer, looking for the key drivers of therapy resistance and tumor progression, which may lead to the discovery of new potential targets. We also discuss the most prominent molecules targeting the stroma and immune compartment that are being investigated in either preclinical or clinical trials. Finally, we also outline interesting venues for further research, such as possible combinations of therapies that may have the potential for clinical application.

Abstract

Pancreatic cancer is one of the deadliest cancers worldwide, largely due to its aggressive development. Consequently, treatment options are often palliative, as only one-fifth of patients present with potentially curable tumors. The only available treatment with curative intent is surgery followed by adjuvant chemotherapy. However, even for patients that are eligible for surgery, the 5-year OS remains below 10%. Hence, there is an urgent need to find new therapeutic regimens. In the first part of this review, we discuss the tumor staging method and its impact on the corresponding current standard-of-care treatments for PDAC. We also consider the key clinical trials over the last 20 years that have improved patient survival. In the second part, we provide an overview of the major components and cell types involved in PDAC, as well as their respective roles and interactions with each other. A deeper knowledge of the interactions taking place in the TME may lead to the discovery of potential new therapeutic targets. Finally, we discuss promising treatment strategies targeting specific components of the TME and potential combinations thereof. Overall, this review provides an overview of the current challenges and future perspectives in the treatment of pancreatic cancer.

Microenvironmental modulation of the developing tumour: an immune-stromal dialogue

Successful establishment of a tumour relies on a cascade of interactions between cancer cells and stromal cells within an evolving microenvironment. Both immune and nonimmune cellular components are key factors in this process, and the individual players may change their role from tumour elimination to tumour promotion as the microenvironment develops. While the tumour-stroma crosstalk present in an established tumour is well-studied, aspects in the early tumour or premalignant microenvironment have received less attention. This is in part due to the challenges in studying this process in the clinic or in mouse models. Here, we review the key anti- and pro-tumour factors in the early microenvironment and discuss how understanding this process may be exploited in the clinic.

Cancer cell migration in collagen-hyaluronan composite extracellular matrices

Hyaluronan (HA) is a key component in the tumor microenvironment (TME) that participates in cancer growth and invasiveness. While the molecular weight (MW) dependent properties of HA can cause tumor-promoting and -repressing effects, the elevated levels of HA in the TME impedes drug delivery. The degradation of HA using hyaluronidases (HYALs), resulting in fragments of HA, is a way to overcome this, but the consequences of changes in HA molecular weight and concentration is currently unknown. Therefore, it is critical to understand the MW-dependent biological effects of HA. Here we examine the influence of HA molecular weight on biophysical properties that regulate cell migration and extracellular matrix (ECM) remodeling. In our study, we used vLMW, LMW and HMW HA at different physiologically relevant concentrations, with a particular interest in correlating the mechanical and structural properties to different cell functions. The elastic modulus, collagen network pore size and collagen fiber diameter increased with increasing HA concentration. Although the collagen network pore size increased, these pores were filled with the bulky HA molecules. Consequently, cell migration decreased with increase in HA concentration due to multiple, long-lived and unproductive protrusions, suggesting the influence of steric factors. Surprisingly, even though elastic modulus increased with HA molecular weight and concentration, gel compaction assays showed an increased degree of ECM compaction among HMW HA gels at high concentrations (2 and 4 mg mL^-1 [0.2 and 0.4%]). These results were not seen in collagen gels that lacked HA, but had similar stiffness. HA appears to have the effect of decreasing migration and increasing collagen network contraction, but only at high HA molecular weight. Consequently, changes in HA molecular weight can have relatively large effects on cancer cell behavior. STATEMENT OF SIGNIFICANCE: Hyaluronan (HA) is a critical component of the tumor microenvironment (TME). Overproduction of HA in the TME results in poor prognosis and collapse of blood vessels, inhibiting drug delivery. Hyaluronidases have been used to enhance drug delivery. However, they lead to low molecular weight (MW) HA, altering the mechanical and structural properties of the TME and cancer cell behavior. Understanding how HA degradation affects cancer cell behavior is critical for uncovering detrimental effects of this therapy. Very little is known about how HA MW affects cancer cell behavior in tumor-mimicking collagen-HA composite networks. Here we examine how MW and HA content in collagen-HA networks alter structural and mechanical properties to regulate cell migration and matrix remodeling in 3D TME-mimicking environments.

Therapeutic Targeting of the Tumor Microenvironment

Strategies to therapeutically target the tumor microenvironment (TME) have emerged as a promising approach for cancer treatment in recent years due to the critical roles of the TME in regulating tumor progression and modulating response to standard-of-care therapies. Here, we summarize the current knowledge regarding the most advanced TME-directed therapies, which have either been clinically approved or are currently being evaluated in trials, including immunotherapies, antiangiogenic drugs, and treatments directed against cancer-associated fibroblasts and the extracellular matrix. We also discuss some of the challenges associated with TME therapies, and future perspectives in this evolving field. SIGNIFICANCE: This review provides a comprehensive analysis of the current therapies targeting the TME, combining a discussion of the underlying basic biology with clinical evaluation of different therapeutic approaches, and highlighting the challenges and future perspectives.

Future directions in drug development in pancreatic cancer

Pancreatic cancer is still one of the most lethal cancers with a reported 5-year relative survival rate of approximatively 9% and medical treatment remains a major challenge. Systemic treatment is recommended in every setting: resectable, borderline resectable, locally advanced and metastatic. Yet, few groundbreaking changes in practice have occurred in the last 30 years compared to other cancers and new treatments options are highly desirable. Most treatment approaches using chemotherapy have failed to improve patients' life expectancy and the few therapies finally found to have statistically significant benefit actually have modest clinical impact. It is becoming imperative to find new paths for improvement, such as encapsulated agents, new generation targeted therapies and treatments directed against the tumor microenvironment. We report here the new drugs of interest in pancreatic cancer and analyze the most recent failures.

Stromal regulation of tumor-associated lymphatics

Recent advances have identified a growing array of roles played by lymphatics in the tumor microenvironment, from providing a route of metastasis to immune modulation. The tumor microenvironment represents an exceptionally complex, dynamic niche comprised of a diverse mixture of cancer cells and normal host cells termed the stroma. This review discusses our current understanding of stromal elements and how they regulate lymphatic growth and functional properties in the tumor context.

Pressure-enabled delivery of gemcitabine in an orthotopic pancreatic cancer mouse model

BACKGROUND

We describe the use of pancreatic retrograde venous infusion in an orthotopic murine model of pancreatic ductal adenocarcinoma and hypothesize that pancreatic retrograde venous infusion delivery of gemcitabine will increase concentrations of gemcitabine in the tumor and the subsequent tumor response to treatment.

METHODS

Murine pancreatic ductal adenocarcinoma (KPC4580P) was transplanted onto the pancreatic tail of C57BL/6J mice. Groups (n = 15) of mice were assigned to sham laparotomy and 100 mg/kg intraperitoneal infusion of gemcitabine (systemic gemcitabine), pancreatic venous isolation with pancreatic retrograde venous infusion of 100 mg/kg gemcitabine, or pancreatic retrograde venous infusion with saline infusion. Tumor pressures were recorded during pancreatic retrograde venous infusion. Mice were killed at 1 hour or 7 days after infusion.

RESULTS

Baseline tumor pressures were 45 ± 8 mm Hg, and pancreatic retrograde venous infusion increased tumor pressures by 29 ± 6 mm Hg (P < .01). Pancreatic retrograde venous infusion gemcitabine mice had greater tumor gemcitabine concentrations compared with systemic gemcitabine (127 vs 19 ng/mg; P < .01) and lesser tumor volumes compared with both systemic gem and pancreatic retrograde venous infusion with saline (274 vs 857 vs 629 mm³; P < .01).

CONCLUSION

Pancreatic retrograde venous infusion increased tumor pressures greater than baseline, improved gemcitabine delivery, and increased the treatment response. These findings suggest that pressurized, regional delivery overcomes the increased pressure barrier in pancreatic ductal adenocarcinoma. Additional preclinical studies with cytotoxic and immunotherapeutic agents and clinical trials using pressure-enabled drug delivery with pancreatic retrograde venous infusion devices are underway.

Proteomic analyses of ECM during pancreatic ductal adenocarcinoma progression reveal different contributions by tumor and stromal cells

Pancreatic ductal adenocarcinoma (PDAC) has prominent extracellular matrix (ECM) that compromises treatments yet cannot be nonselectively disrupted without adverse consequences. ECM of PDAC, despite the recognition of its importance, has not been comprehensively studied in patients. In this study, we used quantitative mass spectrometry (MS)-based proteomics to characterize ECM proteins in normal pancreas and pancreatic intraepithelial neoplasia (PanIN)- and PDAC-bearing pancreas from both human patients and mouse genetic models, as well as chronic pancreatitis patient samples. We describe detailed changes in both abundance and complexity of matrisome proteins in the course of PDAC progression. We reveal an early up-regulated group of matrisome proteins in PanIN, which are further up-regulated in PDAC, and we uncover notable similarities in matrix changes between pancreatitis and PDAC. We further assigned cellular origins to matrisome proteins by performing MS on multiple lines of human-to-mouse xenograft tumors. We found that, although stromal cells produce over 90% of the ECM mass, elevated levels of ECM proteins derived from the tumor cells, but not those produced exclusively by stromal cells, tend to correlate with poor patient survival. Furthermore, distinct pathways were implicated in regulating expression of matrisome proteins in cancer cells and stromal cells. We suggest that, rather than global suppression of ECM production, more precise ECM manipulations, such as targeting tumor-promoting ECM proteins and their regulators in cancer cells, could be more effective therapeutically.

Biomaterial substrate-derived compact cellular spheroids mimicking the behavior of pancreatic cancer and microenvironment

Pancreatic stromal cells especially pancreatic stellate cells (PSCs) play a critical role in the progression of human pancreatic ductal adenocarcinoma (PDAC). However, the exact interaction between cancer cells and PSCs remains to be elucidated in order to develop more effective therapeutic approaches to treat PDAC. The microenvironment of PDAC shows higher hyaluronan (HA) levels, which is associated with poor prognosis of PDAC patients. In the current study, an efficient three-dimensional tumor spheroid model for PDAC was established. The pancreatic cancer cells and PSCs were co-cultured on hyaluronan grafted chitosan (CS-HA) coated plates to generate 3D tumor-like co-spheroids. The pancreatic cancer cells and PSCs (1:9 ratio) co-cultured on CS-HA coated plates were assembled into tumor-like co-spheroids with 3D core-shell structure in 48 h. These spheroids displayed potent in vitro tumorigenicity such as up-regulated expression of stemness and migration markers. The migration rate of cancer cells in spheroids (from 1:9 cell ratio) was much faster (3.2-fold) than that of cancer cells alone. Meanwhile, this unique co-spheroidal cancer cell structure with the outer wrap of PSCs contributed to the chemo-resistance of pancreatic cancer cells to gemcitabine as well as sensitivity to the combined gemcitabine and Abraxane treatment in vitro. The metastatic nature of the spheroids was confirmed by the zebrafish xenograft model in vivo. The compact and dynamic pancreatic cancer-PSC co-spheroids generated by the unique 3D co-culture platform on CS-HA biomaterials can mimic the PSC-constituting microenvironment of PDAC and demonstrate the chemo-resistant, invasive, and metastatic phenotypes. They have potential applications in personalized and high-throughput drug screening.

Emerging Therapies and Future Directions in Targeting the Tumor Stroma and Immune System in the Treatment of Pancreatic Adenocarcinoma

Pancreatic adenocarcinoma is typically refractory to conventional treatments and associated with poor prognosis. While therapeutic advances over the past several years have improved patient outcomes, the observed benefits have been modest at best, highlighting the need for continued development of alternate treatment strategies. The tumor microenvironment has been identified as being integral to oncogenesis through its direct effect on cellular pathway communication, immune inhibition, and promoting chemo-resistance. A more in depth understanding of the biology of the disease, in addition with our ability to develop more effective novel therapies have led to ongoing studies that are investigating several promising treatment options in this disease. Herein, we highlight and review the therapeutic landscape in pancreatic adenocarcinoma.

Frontiers in Gastrointestinal Oncology: Advances in Multi-Disciplinary Patient Care

Cancers of the digestive system remain highly lethal; therefore, the care of patients with malignant diseases of the digestive tract requires the expertise of providers from multiple health disciplines. Progress has been made to advance the understanding of epidemiology and genetics, diagnostic and screening evaluation, treatment modalities, and supportive care for patients with gastrointestinal cancers. At the Multi-Disciplinary Patient Care in Gastrointestinal Oncology conference at the Hershey Country Club in Hershey, Pennsylvania on 29 September 2017, the faculty members of the Penn State Health Milton S. Hershey Medical Center presented a variety of topics that focused on this oncological specialty. In this continuing medical education-certified conference, updates on the population sciences including health disparities and resistance training were presented. Progress made in various diagnostic evaluation and screening procedures was outlined. New developments in therapeutic modalities in surgical, radiation, and medical oncology were discussed. Cancer genetic testing and counseling and the supportive roles of music and arts in health and cancer were demonstrated. In summary, this disease-focused medical conference highlighted the new frontiers in gastrointestinal oncology, and showcase the multi-disciplinary care provided at the Penn State Cancer Institute.

Immunotherapy and Prevention of Pancreatic Cancer

Pancreatic cancer is the third-leading cause of cancer mortality in the USA, recently surpassing breast cancer. A key component of pancreatic cancer's lethality is its acquired immune privilege, which is driven by an immunosuppressive microenvironment, poor T cell infiltration, and a low mutational burden. Although immunotherapies such as checkpoint blockade or engineered T cells have yet to demonstrate efficacy, a growing body of evidence suggests that orthogonal combinations of these and other strategies could unlock immunotherapy in pancreatic cancer. In this Review article, we discuss promising immunotherapies currently under investigation in pancreatic cancer and provide a roadmap for the development of prevention vaccines for this and other cancers.

Biomarker-Based Therapy in Pancreatic Ductal Adenocarcinoma: An Emerging Reality?

Over the last decade, many of the major solid organ cancers have seen improvements in survival due to development of novel therapeutics and corresponding biomarkers that predict treatment efficacy or resistance. In contrast, favorable outcomes remain challenging in pancreatic ductal adenocarcinoma (PDAC), in part related to the lack of validated biomarkers for patient and treatment selection and thus optimal clinical decision-making. Increasingly, however, therapeutic development for PDAC is accompanied by bioassays to evaluate response and to study mechanism of actions with a corresponding increase in the number of trials in mid to late stage with integrated biomarkers. In addition, blood-based biomarkers that provide a measure of disease activity and allow for minimally invasive tumor analyses are emerging, including circulating tumor DNA, exosomes, and circulating tumor cells. In this article, we review potential biomarkers for currently approved therapies as well as emerging biomarkers for therapeutics under development. Clin Cancer Res; 24(10); 2241-50. ©2017 AACR.

Upper gastrointestinal malignancies in 2017: current perspectives and future approaches

The advent of immune checkpoint inhibitors (PD-1, PD-L1 and CTLA-4) has resulted in unprecedented long-term remissions of unresectable cancers. The efficacy of checkpoint inhibitors was recently demonstrated in gastrointestinal malignancies with mismatch repair deficiencies (dMMR). Pembrolizumab became the first tissue-agnostic US FDA-approved drug based on the presence of the predictive biomarker dMMR. In addition, the FDA in 2017 approved pembrolizumab for PD-L1-positive advanced gastric cancer in third-line and second-line hepatocellular therapy. Novel treatment strategies such as using anti-carcinoembryonic antigen (CEA) bispecific T cells have led to remarkable responses in microsatellite instability-low colorectal cancer. Other major breakthroughs in treating upper gastrointestinal malignancies in 2017 are discussed.

Update in Systemic and Targeted Therapies in Gastrointestinal Oncology

Progress has been made in the treatment of gastrointestinal cancers through advances in systemic therapies, surgical interventions, and radiation therapy. At the Multi-Disciplinary Patient Care in Gastrointestinal Oncology conference, the faculty members of the Penn State Health Milton S. Hershey Medical Center presented a variety of topics that focused on this sub-specialty. This conference paper highlights the new development in systemic treatment of various malignant diseases in the digestive system. Results of the recent clinical trials that investigated the clinical efficacy of pegylated hyaluronidase, napabucasin, and L-asparaginase in pancreatic carcinoma are presented. The use of peri-operative chemotherapy comprised of 5-fluorouracil or capecitabine, leucovorin, oxaliplatin, and docetaxel (FLOT), and immunotherapy including pembrolizumab, nivolumab, and ipilimumab in gastroesophageal carcinoma are discussed. Data from clinical trials that investigated the targeted therapeutics including nivolumab, ramucirumab, lenvatinib, and BLU-554 are reported. The role of adjuvant capecitabine in resected biliary tract carcinoma (BTC) and nab-paclitaxel in combination with gemcitabine and cisplatin in advanced BTC are presented. In colorectal carcinoma, the efficacy of nivolumab, adjuvant FOLFOX or CAPOX, irinotecan/cetuximab/vemurafenib, and trifluridine/tipiracil/bevacizumab, is examined. In summary, some of the above systemic therapies have become or are expected to become new standard of care, while the others demonstrate the potential of becoming new treatment options.

Polymer Therapeutics: Biomarkers and New Approaches for Personalized Cancer Treatment

Polymer therapeutics (PTs) provides a potentially exciting approach for the treatment of many diseases by enhancing aqueous solubility and altering drug pharmacokinetics at both the whole organism and subcellular level leading to improved therapeutic outcomes. However, the failure of many polymer-drug conjugates in clinical trials suggests that we may need to stratify patients in order to match each patient to the right PT. In this concise review, we hope to assess potential PT-specific biomarkers for cancer treatment, with a focus on new studies, detection methods, new models and the opportunities this knowledge will bring for the development of novel PT-based anti-cancer strategies. We discuss the various "hurdles" that a given PT faces on its passage from the syringe to the tumor (and beyond), including the passage through the bloodstream, tumor targeting, tumor uptake and the intracellular release of the active agent. However, we also discuss other relevant concepts and new considerations in the field, which we hope will provide new insight into the possible applications of PT-related biomarkers.

Drug development and clinical trial design in pancreatico-biliary malignancies

Pancreatico-biliary (P-B) tumors arise from the pancreas, bile duct, and ampulla of Vater. Despite their close anatomical location, they have different etiology and biology. However, they uniformly share a poor prognosis, with no major improvements observed in overall survival over decades, even in the face of progress in diagnostic imaging and surgical techniques, and advances in systemic and loco-regional radiation therapies. To date, cytotoxic treatment has been associated with modest benefits in the advanced disease setting, and survival for patients with stage IV disease has not exceeded a year. Therefore, there is a pressing need to identify better treatments which may impact more significantly. Frequently, encouraging signals of potential efficacy for novel agents in early phase clinical trials have been followed by disappointing failures in larger phase III trials, raising the valid question of how drug development can be optimized for patients with pancreatic adenocarcinoma and biliary tract malignancies. In this article we summarize the current therapeutic options for these patients and their limitations. The biological context of these cancers is reviewed, highlighting features that may make them resistant to standard chemotherapeutics and could be potential therapeutic targets. We discuss the role of early phase clinical trials, defined as phase I and non-randomised phase II trials, within the clinical context and current therapeutic landscape of P-B tumors and postulate how translational studies and trial design may enable better realization of emerging targets together with a proposed model for future patient management. A detailed summary of current phase I clinical trials in P-B tumors is provided.

More than a Gel & Hyaluronic Acid, a Central Component in the Microenvironment of Pancreatic Cancer

Hyaluronic acid or hyaluronan (HA) is a major stromal component and its accumulation has been shown to play a central role in promoting tumourigenesis and progression of disease. Thus, overexpression of HA in tumours is associated with poor prognosis. Therapeutic targeting of HA is therefore an attractive strategy, particularly in pancreatic ductal adenocarcinoma (PDA), which is associated with an extremely poor prognosis and less sensitivity towards chemotherapy. PDA is characterised by a high stromal content. The accumulation of dense, fibrotic extracellular matrix components within the stroma, termed desmoplasia, results in increased tumour interstitial fluid pressure and vascular compression that impair the delivery and efficacy of therapeutic agents. While some elements of the stroma may be protective for the patient and prevent a more aggressive phenotype of PDA, a pegylated recombinant human hyaluronidase (pegvorhyaluronidase alfa) has been found to inhibit tumour growth in preclinical studies. In a clinical phase II randomised trial, the addition of pegvorhyaluronidase alfa to nab-paclitaxel and gemcitabine suggested significantly longer progression-free survival in patients with advanced PDA compared with nab-paclitaxel and gemcitabine alone. This benefit was even more pronounced in a subgroup of patients who expressed high levels of tumour HA.

Clinical Trials in Pancreatic Cancer: A Long Slog

Many investigators have turned their efforts toward improving the gemcitabine/nab‐paclitaxel combination by the addition of a third agent. This commentary highlights efforts to date, including the Clinical Trial Results by Ko et al.: A Randomized Double‐Blinded Phase II Trial of Gemcitabine and Nab‐Paclitaxel Plus Apatorsen or Placebo in Patients with Metastati Pancreatic Cancer: The RAINIER Trial.

HALO-109-301: a Phase III trial of PEGPH20 (with gemcitabine and nab-paclitaxel) in hyaluronic acid-high stage IV pancreatic cancer

The outlook for patients with advanced pancreatic cancer remains poor, despite significant advances in our understanding of pancreatic tumor biology. One emerging theme highlights the distinct composition of the pancreatic tumor microenvironment. Hyaluronic acid is a hydrophilic glycosaminoglycan whose production within the tumor leads to increased interstitial tumor pressure, thereby limiting the access of potentially effective circulating anticancer drugs via reduced tumor perfusion. PEGylated rHuPH20 is a multiply PEGylated recombinant human hyaluronidase that has shown promising efficacy in preclinical models and early phase clinical trials in pancreatic cancer patients. Here, we discuss these findings, and the rationale for the ongoing randomized Phase III trial (HALO-109-301), which seeks to definitively define the efficacy of PEGylated rHuPH20 alongside gemcitabine and nab-paclitaxel in previously untreated, hyaluronic acid-high, stage IV pancreatic cancer.

Polymer therapeutics at a crossroads? Finding the path for improved translation in the twenty-first century

Despite the relatively small early investment, first generation 'polymer therapeutics' have been remarkably successful with more than 25 products licenced for human use as polymeric drugs, sequestrants, conjugates, and as an imaging agent. Many exhibit both clinical and commercial success with new concepts already in clinical trials. Nevertheless after four decades of evolution, this field is arriving at an important crossroads. Over the last decade, the landscape has changed rapidly. There are an increasing number of failed clinical trials, the number of 'copy' and 'generic' products is growing (danger of ignoring the biological rationale for design and suppression of innovation), potential drawbacks of PEG are becoming more evident, and the 'nanomedicine' boom has brought danger of loss of scientific focus/hype. Grasping opportunities provided by advances in understanding of the patho-physiology and molecular basis of diseases, new polymer/conjugate synthetic and analytical methods, as well as the large database of clinical experience will surely ensure a successful future for innovative polymer therapeutics. Progress will, however, be in jeopardy if polymer safety is overlooked in respect of the specific route of administration/clinical use, poorly characterised materials/formulations are used to define biological or early clinical properties, and if clinical trial protocols fail to select patients most likely to benefit from these macromolecular therapeutics. Opportunities to improve clinical trial design for polymer-anticancer drug conjugates are discussed. This short personal perspective summarises some of the important challenges facing polymer therapeutics in R&D today, and future opportunities to improve successful translation.

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.