Modulation of Extracellular Matrix Rigidity Via Riboflavin-mediated Photocrosslinking Regulates Invasive Motility and Treatment Response in a 3D Pancreatic Tumor Model

PD-L1 Immune Checkpoint Targeted Photoactivable Liposomes (iTPALs) Prime the Stroma of Pancreatic Tumors and Promote Self-Delivery

Desmoplasia in pancreatic ductal adenocarcinoma (PDAC) limits the penetration and efficacy of therapies. It has been previously shown that photodynamic priming (PDP) using EGFR targeted photoactivable multi-inhibitor liposomes remediates desmoplasia in PDAC and doubles overall survival. Here, bifunctional PD-L1 immune checkpoint targeted photoactivable liposomes (iTPALs) that mediate both PDP and PD-L1 blockade are presented. iTPALs also improve phototoxicity in PDAC cells and induce immunogenic cell death. PDP using iTPALs reduces collagen density, thereby promoting self-delivery by 5.4-fold in collagen hydrogels, and by 2.4-fold in syngeneic CT1BA5 murine PDAC tumors. PDP also reduces tumor fibroblast content by 39.4%. Importantly, iTPALs also block the PD-1/PD-L1 immune checkpoint more efficiently than free α-PD-L1 antibodies. Only a single sub-curative priming dose using iTPALs provides 54.1% tumor growth inhibition and prolongs overall survival in mice by 42.9%. Overall survival directly correlates with the extent of tumor iTPAL self-delivery following PDP (Pearson's r = 0.670, p = 0.034), while no relationship is found for sham non-specific IgG constructs activated with light. When applied over multiple cycles, as is typical for immune checkpoint therapy, PDP using iTPALs promises to offer durable tumor growth delay and significant survival benefit in PDAC patients, especially when used to promote self-delivery of integrated chemo-immunotherapy regimens.

Immunofluorescence profiling of collagen subtypes is a predictor of treatment outcomes in pancreatic cancer

Desmoplasia in pancreatic ductal adenocarcinoma (PDAC) is characterized by elevated levels of tumor collagen. Desmoplasia restricts drug delivery in PDAC, contributes to treatment resistance, and is associated with poor survival outcomes. We have previously shown that photodynamic therapy (PDT)-based treatment remediates desmoplasia in orthotopic PDAC tumors by reducing second harmonic generation signals from collagen by >90% and by reducing collagen alignment by >103-fold [19]. Remediating desmoplasia correlated with improved survival outcomes in mice. To understand this phenomenon at a fundamental level, it is important to dissect the impact of therapy on collagen subtypes. In this study, we demonstrate that immunofluorescence profiling of collagen subtypes I, II, III and IV in PDAC tumors 72 h following multiple treatment regimens is predictive of long-term outcomes. Treatment regimens include nanoliposomal irinotecan chemotherapy (nal-IRI; akin to ONIVYDE™), a combination of nal-IRI chemotherapy with PDT encapsulated in a single photoactivable multi-inhibitor liposome (PMIL) and an EGFR-targeted PMIL construct (TPMIL). Results show that the relative tumor content of collagen I, II and III was inversely correlated with overall survival (P ≤ 0.0013, P ≤ 0.0001, P ≤ 0.0011, respectively), while, surprisingly, the relative tumor content of collagen IV was directly correlated with overall survival (P ≤ 0.0001). Similar relationships were observed between the relative tumor content of collagen subtypes and the residual tumor volume at day 88 following treatment. Considering that the relationship between collagen subtypes and treatment outcomes is observed across multiple treatment regimens, immunofluorescence profiling at 72 h following treatment appears to be predictive of tumor growth inhibition and survival in PDAC. Early immunofluorescence collagen subtype profiling may therefore aid in treatment personalization and may inform the dosimetry and scheduling of combination regimens for PDAC, such as chemotherapy and emerging PDT-based combinations, to maximize patient survival benefit.

Photodynamic Stromal Depletion in Pancreatic Ductal Adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is one of the deadliest solid malignancies, with a five-year survival of less than 10%. The resistance of the disease and the associated lack of therapeutic response is attributed primarily to its dense, fibrotic stroma, which acts as a barrier to drug perfusion and permits tumour survival and invasion. As clinical trials of chemotherapy (CT), radiotherapy (RT), and targeted agents have not been successful, improving the survival rate in unresectable PDAC remains an urgent clinical need. Photodynamic stromal depletion (PSD) is a recent approach that uses visible or near-infrared light to destroy the desmoplastic tissue. Preclinical evidence suggests this can resensitise tumour cells to subsequent therapies whilst averting the tumorigenic effects of tumour-stromal cell interactions. So far, the pre-clinical studies have suggested that PDT can successfully mediate the destruction of various stromal elements without increasing the aggressiveness of the tumour. However, the complexity of this interplay, including the combined tumour promoting and suppressing effects, poses unknowns for the clinical application of photodynamic stromal depletion in PDAC.

Impact of hydrogel biophysical properties on tumor spheroid growth and drug response

The extracellular matrix (ECM) plays a critical role in regulating cell-matrix interactions during tumor progression. These interactions are due in large part to the biophysical properties responding to cancer cell interactions. Within in vitro models, the ECM is mimicked by hydrogels, which possess adjustable biophysical properties that are integral to tumor development. This work presents a systematic and comparative study on the impact of the biophysical properties of two widely used natural hydrogels, Matrigel and collagen gel, on tumor growth and drug response. The biophysical properties of Matrigel and collagen including complex modulus, loss tangent, diffusive permeability, and pore size, were characterised. Then the spheroid growth rates in these two hydrogels were monitored for spheroids with two different sizes (140 μm and 500 μm in diameters). An increased migratory growth was observed in the lower concentration of both the gels. The effect of spheroid incorporation within the hydrogel had a minimal impact on the hydrogel's complex modulus. Finally, 3D tumor models using different concentrations of hydrogels were applied for drug treatment using paclitaxel. Spheroids cultured in hydrogels with different concentrations showed different drug response, demonstrating the significant effect of the choice of hydrogels and their concentrations on the drug response results despite using the same spheroids. This study provides useful insights into the effect of hydrogel biophysical properties on spheroid growth and drug response and highlights the importance of hydrogel selection and in vitro model design.

Cancer-Associated Fibroblasts in a 3D Engineered Tissue Model Induce Tumor-like Matrix Stiffening and EMT Transition

Simple Summary

The physical properties of a tumor, such as stiffness, are important drivers of tumor progression. However, current in vitro tumor models fail to recapitulate the full range of physical properties observed in solid tumors. Here, we proposed a 3D self-assembly engineered bladder model using cancer-associated fibroblasts in which stromal cells produce their extracellular matrix. We then proceeded to assess how our model recapitulates biological and mechanical features found in tumors. We confirmed that stroma assembled by cancer-associated fibroblasts have increased extracellular matrix content and display increased remodeling and higher stiffness. Moreover, normal urothelial cells seeded on the tumor model displayed a mechanotransduction response, increased cell proliferation, cell infiltration within stroma, and displayed features of the epithelial-to-mesenchymal transition. Altogether, we demonstrated that our cancer-associated fibroblast-derived tumor stroma recapitulates several biological and physical features expected from a tumor-like environment and, thus, provides the basis for more accurate cancer models.

Abstract

A tumor microenvironment is characterized by its altered mechanical properties. However, most models remain unable to faithfully recreate the mechanical properties of a tumor. Engineered models based on the self-assembly method have the potential to better recapitulate the stroma architecture and composition. Here, we used the self-assembly method based on a bladder tissue model to engineer a tumor-like environment. The tissue-engineered tumor models were reconstituted from stroma-derived healthy primary fibroblasts (HFs) induced into cancer-associated fibroblast cells (iCAFs) along with an urothelium overlay. The iCAFs-derived extracellular matrix (ECM) composition was found to be stiffer, with increased ECM deposition and remodeling. The urothelial cells overlaid on the iCAFs-derived ECM were more contractile, as measured by quantitative polarization microscopy, and displayed increased YAP nuclear translocation. We further showed that the proliferation and expression of epithelial-to-mesenchymal transition (EMT) marker in the urothelial cells correlate with the increased stiffness of the iCAFs-derived ECM. Our data showed an increased expression of EMT markers within the urothelium on the iCAFs-derived ECM. Together, our results demonstrate that our tissue-engineered tumor model can achieve stiffness levels comparable to that of a bladder tumor, while triggering a tumor-like response from the urothelium.

Remediating Desmoplasia with EGFR-Targeted Photoactivable Multi-Inhibitor Liposomes Doubles Overall Survival in Pancreatic Cancer

Desmoplasia is characteristic of pancreatic ductal adenocarcinoma (PDAC), which exhibits 5-year survival rates of 3%. Desmoplasia presents physical and biochemical barriers that contribute to treatment resistance, yet depleting the stroma alone is unsuccessful and even detrimental to patient outcomes. This study is the first demonstration of targeted photoactivable multi-inhibitor liposomes (TPMILs) that induce both photodynamic and chemotherapeutic tumor insult, while simultaneously remediating desmoplasia in orthotopic PDAC. TPMILs targeted with cetuximab (anti-EGFR mAb) contain lipidated benzoporphyrin derivative (BPD-PC) photosensitizer and irinotecan. The desmoplastic tumors comprise human PDAC cells and patient-derived cancer-associated fibroblasts. Upon photoactivation, the TPMILs induce 90% tumor growth inhibition at only 8.1% of the patient equivalent dose of nanoliposomal irinotecan (nal-IRI). Without EGFR targeting, PMIL photoactivation is ineffective. TPMIL photoactivation is also sixfold more effective at inhibiting tumor growth than a cocktail of Visudyne-photodynamic therapy (PDT) and nal-IRI, and also doubles survival and extends progression-free survival by greater than fivefold. Second harmonic generation imaging reveals that TPMIL photoactivation reduces collagen density by >90% and increases collagen nonalignment by >103 -fold. Collagen nonalignment correlates with a reduction in tumor burden and survival. This single-construct phototoxic, chemotherapeutic, and desmoplasia-remediating regimen offers unprecedented opportunities to substantially extend survival in patients with otherwise dismal prognoses.

Photoimmunotherapy Retains Its Anti-Tumor Efficacy with Increasing Stromal Content in Heterotypic Pancreatic Cancer Spheroids

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive disease characterized by increased levels of desmoplasia that contribute to reduced drug delivery and poor treatment outcomes. In PDAC, the stromal content can account for up to 90% of the total tumor volume. The complex interplay between stromal components, including pancreatic cancer-associated fibroblasts (PCAFs), and PDAC cells in the tumor microenvironment has a significant impact on the prognoses and thus needs to be recapitulated in vitro when evaluating various treatment strategies. This study is a systematic evaluation of photodynamic therapy (PDT) in 3D heterotypic coculture models of PDAC with varying ratios of patient-derived PCAFs that simulate heterogeneous PDAC tumors with increasing stromal content. The efficacy of antibody-targeted PDT (photoimmunotherapy; PIT) using cetuximab (a clinically approved anti-EGFR antibody) photoimmunoconjugates (PICs) of a benzoporphyrin derivative (BPD) is contrasted with that of liposomal BPD (Visudyne), which is currently in clinical trials for PDT of PDAC. We demonstrate that both Visudyne-PDT and PIT were effective in heterotypic PDAC 3D spheroids with a low stromal content. However, as the stromal content increases above 50% in the 3D spheroids, the efficacy of Visudyne-PDT is reduced by up to 10-fold, while PIT retains its efficacy. PIT was found to be 10-, 19-, and 14-fold more phototoxic in spheroids with 50, 75, and 90% PCAFs, respectively, as compared to Visudyne-PDT. This marked difference in efficacy is attributed to the ability of PICs to penetrate and distribute homogeneously within spheroids with a higher stromal content and the mechanistically different modes of action of the two formulations. This study thus demonstrates how the stromal content in PDAC spheroids directly impacts their responsiveness to PDT and proposes PIT to be a highly suited treatment option for desmoplastic tumors with particularly high degrees of stromal content.

Engineering hydrogels for personalized disease modeling and regenerative medicine

Technological innovations and advances in scientific understanding have created an environment where data can be collected, analyzed, and interpreted at scale, ushering in the era of personalized medicine. The ability to isolate cells from individual patients offers tremendous promise if those cells can be used to generate functional tissue replacements or used in disease modeling to determine optimal treatment strategies. Here, we review recent progress in the use of hydrogels to create artificial cellular microenvironments for personalized tissue engineering and regenerative medicine applications, as well as to develop personalized disease models. We highlight engineering strategies to control stem cell fate through hydrogel design, and the use of hydrogels in combination with organoids, advanced imaging methods, and novel bioprinting techniques to generate functional tissues. We also discuss the use of hydrogels to study molecular mechanisms underlying diseases and to create personalized in vitro disease models to complement existing pre-clinical models. Continued progress in the development of engineered hydrogels, in combination with other emerging technologies, will be essential to realize the immense potential of personalized medicine. STATEMENT OF SIGNIFICANCE: In this review, we cover recent advances in hydrogel engineering strategies with applications in personalized medicine. Specifically, we focus on material systems to expand or control differentiation of patient-derived stem cells, and hydrogels to reprogram somatic cells to pluripotent states. We then review applications of hydrogels in developing personalized engineered tissues. We also highlight the use of hydrogel systems as personalized disease models, focusing on specific examples in fibrosis and cancer, and more broadly on drug screening strategies using patient-derived cells and hydrogels. We believe this review will be a valuable contribution to the Special Issue and the readership of Acta Biomaterialia will appreciate the comprehensive overview of the utility of hydrogels in the developing field of personalized medicine.

Photodynamic Therapy for Pancreatic Ductal Adenocarcinoma

Simple Summary

Pancreatic ductal adenocarcinoma (PDAC) is among the most lethal of human cancers. Numerous clinical trials evaluating various combinations of chemotherapy and targeted agents and radiotherapy have failed to provide meaningful improvements in survival. A growing number of studies however have indicated that photodynamic therapy (PDT) may be a viable approach for treatment of some pancreatic tumors. PDT, which uses light to activate a photosensitizing agent in target tissue, has seen widespread adoption primarily for dermatological and other applications where superficial light delivery is relatively straightforward. Advances in fiber optic light delivery and dosimetry however have been leveraged to enable PDT even for challenging internal sites, including the pancreas. The aim of this article is to help inform future directions by reviewing relevant literature on the basic science, current clinical status, and potential challenges in the development of PDT as a treatment for PDAC.

Abstract

Pancreatic ductal adenocarcinoma (PDAC) is among the most lethal of human cancers. Clinical trials of various chemotherapy, radiotherapy, targeted agents and combination strategies have generally failed to provide meaningful improvement in survival for patients with unresectable disease. Photodynamic therapy (PDT) is a photochemistry-based approach that enables selective cell killing using tumor-localizing agents activated by visible or near-infrared light. In recent years, clinical studies have demonstrated the technical feasibility of PDT for patients with locally advanced PDAC while a growing body of preclinical literature has shown that PDT can overcome drug resistance and target problematic and aggressive disease. Emerging evidence also suggests the ability of PDT to target PDAC stroma, which is known to act as both a barrier to drug delivery and a tumor-promoting signaling partner. Here, we review the literature which indicates an emergent role of PDT in clinical management of PDAC, including the potential for combination with other targeted agents and RNA medicine.

3D Cell Culture: Recent Development in Materials with Tunable Stiffness

It is widely accepted that three-dimensional cell culture systems simulate physiological conditions better than traditional 2D systems. Although extracellular matrix components strongly modulate cell behavior, several studies underlined the importance of mechanosensing in the control of different cell functions such as growth, proliferation, differentiation, and migration. Human tissues are characterized by different degrees of stiffness, and various pathologies (e.g., tumor or fibrosis) cause changes in the mechanical properties through the alteration of the extracellular matrix structure. Additionally, these modifications have an impact on disease progression and on therapy response. Hence, the development of platforms whose stiffness could be modulated may improve our knowledge of cell behavior under different mechanical stress stimuli. In this review, we have analyzed the mechanical diversity of healthy and diseased tissues, and we have summarized recently developed materials with a wide range of stiffness.

Chemopreventive effect of riboflavin on the potassium bromate-induced renal toxicity in vivo

Potassium bromate (PB) is a general food additive, flavor enhancer, a by-product of water disinfection, and a class 2 carcinogen. It exerts various toxic effects in a dose- and time-dependent manner in vivo. This study is to explore the chemopreventive efficacy of vitamin B2 (riboflavin, RF) in PB-administered Swiss albino rats. The rats were distributed into five groups: control (group 1), PB alone (group 2, 150 mg/kg), RF alone (group 3, 2 mg/kg), PB + RF1 (group 4, 150 and 2 mg/kg), and PB + RF2 (group 5, 150 and 4 mg/kg). All the rodents were sacrificed after the completion of the treatment cycle. Then, blood and kidney samples were subjected to biochemical analysis. Group 2 demonstrated vivid signs of renal toxicities evidenced by altered renal function markers (urea, creatinine, albumin, glutathione-S-transferase) and redox status parameters (superoxide dismutase, catalase, glutathione reductase, reduced glutathione, lipid, and protein oxidation products). However, group 3 exhibited a slight alteration in many of the parameters while groups 4 and 5 demonstrated dose-dependent chemopreventive efficiency of RF against PB-induced alterations. Besides, RF seemed to facilitate apoptosis as well as inhibition of the necrosis in the PB-pre-challenged groups, as demonstrated by the cleaved PARP and lactate dehydrogenase activity. Also, the histopathological analysis and comet assay validate the biochemical results of the treatment groups significantly. All these results plead that RF has a significant chemopreventive property against PB-induced toxicity in vivo. Therefore, RF is a suitable agent in preventing the PB-induced toxicities at the clinical and industrial levels.