Tumor-stroma interaction of human pancreatic cancer: acquired resistance to anticancer drugs and proliferation regulation is dependent on extracellular matrix proteins

Stromal fibronectin expression in patients with resected pancreatic ductal adenocarcinoma

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) is characterized by an extremely dense stroma, which has a fundamental role in tumor progression. Fibronectin (FN1) is the main constituent of the tumor stroma in pancreatic cancer. This study aimed to explore the association between FN1 and clinicopathological characteristics and disease survival.

METHODS

Formalin-fixed paraffin-embedded tissue samples from 138 patients with PDAC were constructed into a tissue microarray, followed by immunohistochemical analysis with a recombinant monoclonal FN1 antibody. Chi-square test or Fisher's exact test were used for comparison of FN1 expression and relevant clinicopathological parameters. Kaplan-Meier survival curves and Cox regression analyses were used to assess the association between FN1 and survival.

RESULTS

FN1 was detected in the stromal compartment in most cases (117/138, 84.8%). Compared to the low FN1 expression group, the high FN1 expression group had significantly larger tumor size (P = 0.002), more advanced T stage (P = 0.039) and N stage (P = 0.009), and also worse AJCC stage (P = 0.003). However, stromal FN1 expression was not associated with disease-free survival or overall survival.

CONCLUSIONS

This study suggests that high stromal FN1 expression is associated with aggressive tumor characteristics in patients with resected PDAC. However, no association between FN1 expression and survival was found.

Pancreatic cancer microenvironment: a current dilemma

Pancreatic cancer is one of the leading causes of cancer-related death in the United States and survival outcomes remain dismal despite significant advances in molecular diagnostics and therapeutics in clinical practice. The microenvironment of pancreatic cancer carries unique features with increased desmoplastic reaction and is infiltrated by regulatory T cells and myeloid-derived suppressor cells which negatively impact the effector immune cells. Current evidence suggests that stellate cell-induced hypovascular stroma may have direct effects on aggressive behavior of pancreatic cancer. Preclinical studies suggested improvement in drug delivery to cancer cells with stroma modifying agents. However these findings so far have not been confirmed in clinical trials. In this article, we elaborate current-state-of-the science of the pancreatic cancer microenvironment and its impact on molecular behavior of cancer cells, chemotherapy resistance and druggability of stroma elements in combination with other agents to enhance the efficacy of therapeutic approaches.

Pancreatic cancer chemo-resistance is driven by tumor phenotype rather than tumor genotype

Pancreatic Ductal Adenocarcinoma (PDAC) is one of the deadliest forms of cancer. A major reason for this situation is the fact that these tumors are already resistant or become rapidly resistant to all conventional therapies. Like any transformation process, initiation and development of PDCA are driven by a well known panel of genetic alterations, few of them are shared with most cancers, but many mutations are specific to PDAC and are partially responsible for the great inter-tumor heterogeneity. Importantly, this knowledge has been inefficient in predicting response to anticancer therapy, or in establishing diagnosis and prognosis. Hence, the pre-existing or rapidly acquired resistance of pancreatic cancer cells to therapeutic drugs rely on other parameters and features developed by the cells and/or the micro-environment, that are independent of their genetic profiles. This review sheds light on all major phenotypic, non genetic, alterations known to play important roles in PDAC cells resistance to treatments and therapeutic escape.

Myotilin, a New Topotecan Resistant Protein in Ovarian Cancer Cell Lines

Background: Low effectiveness of chemotherapy in ovarian cancer results from development of drug resistance during treatment. Topotecan (TOP) is a chemotherapeutic drug used in second-line chemotherapy of this cancer. Unfortunately, during treatment cancer can develop diverse cellular and tissue specific mechanisms of resistance to cytotoxic drugs.

Methods: We analyzed development of TOP resistance in ovarian cancer cell lines (A2780 and W1). On the base of our previous results where a set of “new genes” with different functions that can be related to TOP-resistance was described hereby we performed detailed analysis of MYOT expression. MYOT mRNA level (real time PCR analysis), protein expression in cell lysates and cell culture medium (western blot analysis) and protein expression in cancer cells (immunofluorescence analysis) were determined in this study.

Results: We observed increased expression of MYOT in TOP resistant cell lines at both mRNA and protein level. MYOT, together with extracellular matrix molecules like COL1A2 and COL15A1 were also secreted to corresponding cell culture media.

Conclusion: Our results suggest that upregulation of MYOT can be related to TOP resistance in ovarian cancer cell lines.

Tumor⁻Stroma Cross-Talk in Human Pancreatic Ductal Adenocarcinoma: A Focus on the Effect of the Extracellular Matrix on Tumor Cell Phenotype and Invasive Potential

The extracellular matrix (ECM) in the tumor microenvironment modulates the cancer cell phenotype, especially in pancreatic ductal adenocarcinoma (PDAC), a tumor characterized by an intense desmoplastic reaction. Because the epithelial-to-mesenchymal transition (EMT), a process that provides cancer cells with a metastatic phenotype, plays an important role in PDAC progression, the authors aimed to explore in vitro the interactions between human PDAC cells and ECM components of the PDAC microenvironment, focusing on the expression of EMT markers and matrix metalloproteinases (MMPs) that are able to digest the basement membrane during tumor invasion. EMT markers and the invasive potential of HPAF-II, HPAC, and PL45 cells grown on different ECM substrates (fibronectin, laminin, and collagen) were analyzed. While N-cadherin, αSMA, and type I collagen were not significantly affected by ECM components, the E-cadherin/β-catenin complex was highly expressed in all the experimental conditions, and E-cadherin was upregulated by collagen in PL45 cells. Cell migration was unaffected by fibronectin and delayed by laminin. In contrast, collagen significantly stimulated cell migration and the secretion of MMPs. This study's results showed that ECM components impacted cell migration and invasive potential differently. Collagen exerted a more evident effect, providing new insights into the understanding of the intricate interplay between ECM molecules and cancer cells, in order to find novel therapeutic targets for PDAC treatment.

Tumor-stromal cross-talk modulating the therapeutic response in pancreatic cancer

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) is a highly malignant solid tumor with a dismal prognosis. The stroma component makes up to 90% of the tumor mass and is thought to be one of the main reasons for the tumor's high chemoresistance. Cancer associated fibroblasts (CAFs) have previously been identified to be the key stromal players. This is the first time we provide detailed in vitro experiments investigating tumor-stromal interactions when exposed to three well-known chemotherapeutic agents.

METHODS

Monocultures, indirect and direct co-cultures of two PDAC cell lines (AsPC and Panc-1) and six primary patients derived CAFs were treated with gemcitabine, nab-paclitaxel and the γ-secretase-inhibitor (GSI) DAPT. The cell viability of each component was measured with XTT. Finally, IL-6 concentrations of the supernatants were analyzed.

RESULTS

On the contrary to PDAC cell lines, CAF monocultures hardly responded to any treatment which suggested that stroma (CAFs) itself is more resistant to standard chemo-treatments than the epithelial cancer cells. Moreover, only a weak chemotherapeutic response was observed in direct co-cultures of cancer cells with CAFs. A change in the morphology of direct co-cultures was accompanied with the chemoresistance. CAFs were observed to build cage-like structures around agglomerates of tumor cells. High levels of IL-6 were also associated with a reduced response to therapy. Indirect co-cultures make the tumor-stromal interaction more complex.

CONCLUSIONS

CAFs are highly chemoresistant. Direct cell-cell contact and high levels of IL-6 correlate with a high chemoresistance.

The Role of Matrix Gla Protein (MGP) Expression in Paclitaxel and Topotecan Resistant Ovarian Cancer Cell Lines

The major cause of ovarian cancer treatment failure in cancer patients is inherent or acquired during treatment drug resistance of cancer. Matrix Gla protein (MGP) is a secreted, non-collagenous extracellular matrix protein involved in inhibition of tissue calcification. Recently, MGP expression was related to cellular differentiation and tumor progression. A detailed MGP expression analysis in sensitive (A2780) and resistant to paclitaxel (PAC) (A2780PR) and topotecan (TOP) (A2780TR) ovarian cancer cell lines and their corresponding media was performed. MGP mRNA level (real time PCR analysis) and protein expression in cell lysates and cell culture medium (Western blot analysis) and protein expression in cancer cells (immunofluorescence analysis) and cancer patient lesions (immunohistochemistry) were determined in this study. We observed increased expression of MGP in PAC and TOP resistant cell lines at both mRNA and protein level. MGP protein was also detected in the corresponding culture media. Finally, we detected expression of MGP protein in ovarian cancer lesions from different histological type of cancer. MGP is an important factor that might contribute to cancer resistance mechanism by augmenting the interaction of cells with ECM components leading to increased resistance of ovarian cancer cells to paclitaxel and topotecan. Expression found in ovarian cancer tissue suggests its possible role in ovarian cancer pathogenesis.

The Extracellular Matrix and Pancreatic Cancer: A Complex Relationship

Pancreatic ductal adenocarcinoma (PDAC) has an extraordinarily dense fibrotic stroma that impedes tumor perfusion and delivery of anticancer drugs. Since the extracellular matrix (ECM) comprises the bulk of the stroma, it is primarily responsible for the increased interstitial tissue pressure and stiff mechanical properties of the stroma. Besides its mechanical influence, the ECM provides important biochemical and physical cues that promote survival, proliferation, and metastasis. By serving as a nutritional source, the ECM also enables PDAC cells to survive under the nutrient-poor conditions. While therapeutic strategies using stroma-depleting drugs have yielded disappointing results, an increasing body of research indicates the ECM may offer a variety of potential therapeutic targets. As preclinical studies of ECM-targeted drugs have shown promising effects, a number of clinical trials are currently investigating agents with the potential to advance the future treatment of PDAC. Thus, the present review seeks to give an overview of the complex relationship between the ECM and PDAC.

Double-sided effect of tumor microenvironment on platelets targeting nanoparticles

The cancer cells and stromal cells in tumor microenvironment secrete cytokines and recruit "homing" cells (macrophage, lymphocytes, platelets, etc.). Platelets can interact with tumor microenvironment and specifically aggregate at tumor sites. Surprising, we observed different "homing" effects of activated platelets in breast cancer model and pancreatic cancer model which is highly related with the blood supply of tumors. Besides, platelets targeting magnetic nanoparticles (MNPs) can home to breast cancer but be repelled from pancreatic cancer. We observed the targeting effect of MNPs is highly related with the expressions of collagen Ⅰ (marker of extracellular matrix) and CD34 (marker of tumor neovascularization). The homing nanoparticles such as platelets targeting MNPs could realize the tumor targeting ability, photo-thermal effect and tumor immunotherapeutic ability in the accessible tumor (e.g. breast cancer) but not the hypovascular tumor (e.g. pancreatic cancer).

A 3D bioinspired highly porous polymeric scaffolding system for in vitro simulation of pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma is an aggressive disease with an extremely low survival rate. This is due to the (i) poor prognosis and (ii) high resistance of the disease to current treatment options. The latter is partly due to the very complex and dense tissue/tumour microenvironment of pancreatic cancer, which contributes to the disease's progression and the inhibition of apoptotic pathways. Over the last years, advances in tissue engineering and the development of three-dimensional (3D) culture systems have shed more light into cancer research by enabling a more realistic recapitulation of the niches and structure of the tumour microenvironment. Herein, for the first time, 3D porous polyurethane scaffolds were fabricated and coated with fibronectin to mimic features of the structure and extracellular matrix present in the pancreatic cancer tumour microenvironment. The developed 3D scaffold could support the proliferation of the pancreatic tumour cells, which was enhanced with the presence of fibronectin, for a month, which is a significantly prolonged in vitro culturing duration. Furthermore, in situ imaging of cellular and biomarker distribution showed the formation of dense cellular masses, the production of collagen-I by the cells and the formation of environmental stress gradients (e.g. HIF-1α) with similar heterogeneity trends to the ones reported in in vivo studies. The results obtained in this study suggest that this bioinspired porous polyurethane based scaffold has great potential for in vitro high throughput studies of pancreatic cancer including drug and treatment screening.

TRPM2 promotes the proliferation and invasion of pancreatic ductal adenocarcinoma

The aim of the present study was to investigate transient receptor potential cation channel subfamily M member 2 (TRPM2), a promising therapeutic target and biomarker for pancreatic ductal adenocarcinoma (PDAC) prognosis, in addition to determining its effects regarding tumor progression and invasion. PDAC is a fatal disease with a poor prognosis, and its associated pathogenic molecular mechanisms remain to be determined. In the present study, combined analysis using genomic and transcriptomic data from two PDAC studies was performed to discover a survival‑associated biomarker of PDAC. Survival analysis for genes mutated in ≥10 patients was performed using a Kaplan‑Meier curve and tested for significance using a log‑rank test. Furthermore, gene‑expression correlation analysis was performed to determine the genes with the strongest correlations to TRPM2. In addition, a Cell Counting Kit‑8 assay, a scratch wound‑healing assay and a Transwell assay were performed in the present study to investigate the proliferative, invasive and metastatic ability of PANC‑1 cells in TRPM2‑overexpressing and downregulated groups. The mutated TRPM2 gene had a strong negative correlation with patient survival probability compared with the normal control group (P=1.06x10‑4). Expression of TRPM2 was strongly correlated with expression of probable phospholipid‑transporting ATPase IM, γ‑parvin, tudor domain containing 9, Toll‑like receptor 7 and Scm‑like with four MBT domains protein 2 according to the criterion of a correlation coefficient >0.5. Furthermore, the results of the present study demonstrated that the TRPM2 overexpression in a PDAC cell line (PANC‑1) promoted cell proliferation, invasion and metastatic ability. TRPM2 represents a potential therapeutic target and prognostic marker for patients with PDAC. TRPM2 regulates cell proliferation, invasion and migration; however, the underlying mechanism requires further investigation in future studies.

Towards an advanced cell-based in vitro glioma model system

The modulation of tumor growth and development in vitro has always been one of the key factors in the research of the malignant transformation, including gliomas, prevalent and most deadly cancers of the brain. Indeed, cellular and molecular biology research employing in vitro model cell-based systems have great potential to advance both the mechanistic understanding and the treatment of human glial tumors, as it facilitates not only the understanding of glioma biology and its regulatory mechanisms Additionally they promise to afford the screening of the putative anti-tumor agents and alternative treatment approaches in a personalized manner, i.e. by virtue of using the patient-derived tumor material for such tests. However, in order to become reliable and representative, glioma model systems need to move towards including most inherent cancer features such as local hypoxia, specific genetic aberrations, native tumor microenvironment, and the three-dimensional extracellular matrix. This review starts with a brief introduction on the general epidemiological and molecular characteristics of gliomas followed by an overview of the cell-based in vitro models currently used in glioma research. As a conclusion, we suggest approaches to move to innovative cell-based in vitro glioma models. We consider that main criteria for selecting these approaches should include the adequate resemblance to the key in vivo characteristics, robustness, cost-effectiveness and ease to use, as well as the amenability to high throughput handling to allow the standardized drug screening.

Breast cancer cells obtain an osteomimetic feature via epithelial-mesenchymal transition that have undergone BMP2/RUNX2 signaling pathway induction

Bone is one of the most common organs of breast cancer metastasis. Cancer cells that mimic osteoblasts by expressing bone matrix proteins and factors have a higher likelihood of metastasizing to bone. However, the molecular mechanisms of osteomimicry formation of cancer cells remain undefined. Herein, we identified a set of bone-related genes (BRGs) that are ectopically co-expressed in primary breast cancer tissues and determined that osteomimetic feature is obtained due to the osteoblast-like transformation of epithelial breast cancer cells that have undergone epithelial-mesenchymal transition (EMT) followed by bone morphogenetic protein-2 (BMP2) stimulation. Furthermore, we demonstrated that breast cancer cells that transformed into osteoblast-like cells with high expression of BRGs showed enhanced chemotaxis, adhesion, proliferation and multidrug resistance in an osteoblast-mimic bone microenvironment in vitro. During these processes, runt-related transcription factor 2 (RUNX2) functioned as a master mediator by suppressing or activating the transcription of BRGs that underlie the dynamic antagonism between the TGF-β/SMAD and BMP/SMAD signaling pathways in breast cancer cells. Our findings suggest a novel mechanism of osteomimicry formation that arises in primary breast tumors, which may explain the propensity of breast cancer to metastasize to the skeleton and contribute to potential strategies for predicting and targeting breast cancer bone metastasis and multidrug resistance.

The ratio of cancer cells to stroma within the invasive area is a histologic prognostic parameter of lung adenocarcinoma

OBJECTIVES

This study evaluated whether the proportion of cancer cells to non-cancerous stroma within the invasive area is associated with the prognosis of patients with lung adenocarcinoma.

MATERIALS AND METHODS

A total of 127 patients with lung adenocarcinomas with tumors larger than 3 cm in total size were enrolled in this study. We classified the tumors according to the ratio of area occupied by cancer cells within the invasive area (Type A: more than 50% of the invasive area, Type B: 10-50%, and Type C: less than 10%) and analyzed the clinicopathological differences between Types A, B, and C.

RESULTS

The invasive size of Type A tumors (n = 35) was significantly larger than those of the other two tumor types; however, there was no significant difference in the invasive size between Types B (n = 65) and C (n = 25) tumors. The recurrence-free survival time of patients with Type C tumors was significantly longer than those of patients with Type A and B (P < .001) tumors. Multivariate analysis revealed that Type C tumor was an independent favorable prognostic factor (P = .037) but that invasive size was not. The invasive area of Type C tumor was composed of a significantly higher proportion of collapsed elastic fibers than the invasive areas of Type A and B tumors (P < .001).

CONCLUSION

A lower cancer cell to stroma ratio within the invasive area could be a significant prognostic factor in lung adenocarcinoma, suggesting that not only the invasive size but also the invasive character might be an important histologic prognostic parameter.

Extracellular Influences: Molecular Subclasses and the Microenvironment in Pancreatic Cancer

Pancreatic ductal adenocarcinoma (PDAC) is the most prevalent form of pancreatic cancer and carries the worst prognosis of all common cancers. Five-year survival rates have not surpassed 6% for some decades and this lack of improvement in outcome urges a better understanding of the PDAC-specific features which contribute to this poor result. One of the most defining features of PDAC known to contribute to its progression is the abundance of non-tumor cells and material collectively known as the stroma. It is now well recognized that the different non-cancer cell types, signalling molecules, and mechanical properties within a tumor can have both tumor-promoting as well as –inhibitory effects. However, the net effect of this intratumour heterogeneity is not well understood. Heterogeneity in the stromal makeup between patients is even less well established. Such intertumour heterogeneity is likely to be affected by the relative contributions of individual stromal constituents, but how these contributions exactly relate to existing classifications that demarcate intertumour heterogeneity in PDAC is not fully known. In this review, we give an overview of the available evidence by delineating the elements of the PDAC stroma and their contribution to tumour growth. We do so by interpreting the heterogeneity at the gene expression level in PDAC, and how stromal elements contribute to, or interconnect, with this.

Doxorubicin resistance in breast cancer cells is mediated by extracellular matrix proteins

Background

Cancer cell resistance to therapeutics can result from acquired or de novo-mediated factors. Here, we have utilised advanced breast cancer cell culture models to elucidate de novo doxorubicin resistance mechanisms.

Methods

The response of breast cancer cell lines (MCF-7 and MDA-MB-231) to doxorubicin was examined in an in vitro three-dimensional (3D) cell culture model. Cells were cultured with Matrigel™ enabling cellular arrangements into a 3D architecture in conjunction with cell-to-extracellular matrix (ECM) contact.

Results

Breast cancer cells cultured in a 3D ECM-based model demonstrated altered sensitivity to doxorubicin, when compared to those grown in corresponding two-dimensional (2D) monolayer culture conditions. Investigations into the factors triggering the observed doxorubicin resistance revealed that cell-to-ECM interactions played a pivotal role. This finding correlated with the up-regulation of pro-survival proteins in 3D ECM-containing cell culture conditions following exposure to doxorubicin. Inhibition of integrin signalling in combination with doxorubicin significantly reduced breast cancer cell viability. Furthermore, breast cancer cells grown in a 3D ECM-based model demonstrated a significantly reduced proliferation rate in comparison to cells cultured in 2D conditions.

Conclusion

Collectively, these novel findings reveal resistance mechanisms which may contribute to reduced doxorubicin sensitivity.

Image-Based Profiling of Patient-Derived Pancreatic Tumor-Stromal Cell Interactions Within a Micropatterned Tumor Model

Pancreatic cancer is one of the most aggressive cancers with a 5-year patient survival rate of 8.2% and limited availability of therapeutic agents to target metastatic disease. Pancreatic cancer is characterized by a dense stromal cell population with unknown contribution to the progression or suppression of tumor growth. In this study, we describe a microengineered tumor stromal assay of patient-derived pancreatic cancer cells to study the heterotypic interactions of patient pancreatic cancer cells with different types of stromal fibroblasts under basal and drug-treated conditions. The population dynamics of tumor cells in terms of migration and viability were visualized as a functional end point. Coculture with cancer-associated fibroblasts increased the migration of cancer cells when compared to dermal fibroblasts. Finally, we imaged the response of a bromodomain and extraterminal inhibitor on the viability of pancreatic cancer clusters surrounding by stroma in microengineered tumor stromal assay. We visualized a codynamic reduction in both cancer and stromal cells with bromodomain and extraterminal treatment compared to the dimethyl sulfoxide-treated group. This study demonstrates the ability to engineer tumor–stromal assays with patient-derived cells, study the role of diverse types of stromal cells on cancer progression, and precisely visualize a coculture during the screening of therapeutic compounds.

Complex roles of the stroma in the intrinsic resistance to gemcitabine in pancreatic cancer: where we are and where we are going

Pancreatic ductal adenocarcinoma (PDAC) is among the most devastating human malignancies. The poor clinical outcome in PDAC is partly attributed to a growth-permissive tumor microenvironment. In the PDAC microenvironment, the stroma is characterized by the development of extensive fibrosis, with stromal components outnumbering pancreatic cancer cells. Each of the components within the stroma has a distinct role in conferring chemoresistance to PDAC, and intrinsic chemoresistance has further worsened this pessimistic prognosis. The nucleoside analog gemcitabine (GEM) is usually the recommended first-line chemotherapeutic agent for PDAC patients and is given alone or in combination with other agents. The mechanisms of intrinsic resistance to GEM are an active area of ongoing research. This review highlights the important role the complex structure of stroma in PDAC plays in the intrinsic resistance to GEM and discusses whether antistroma therapy improves the efficacy of GEM. The addition of antistroma therapy combined with GEM is expected to be a novel therapeutic strategy with significant survival benefits for PDAC patients.

Intratumoral stromal morphometry predicts disease recurrence but not response to 5-fluorouracil-results from the QUASAR trial of colorectal cancer

AIMS

The biological importance of tumour-associated stroma is becoming increasingly apparent, but its clinical utility remains ill-defined. For stage II/Dukes B colorectal cancer (CRC), clinical biomarkers are urgently required to direct therapeutic options. We report here prognostic/predictive analyses, and molecular associations, of stromal morphometric quantification in the Quick and Simple and Reliable (QUASAR) trial of CRC.

METHODS AND RESULTS

Relative proportions of tumour epithelium (PoT) or stroma (PoS) were morphometrically quantified on digitised haematoxylin and eosin (H&E) sections derived from 1800 patients enrolled in QUASAR, which randomised 3239 (91% stage II) CRC patients between adjuvant fluorouracil/folinic acid (FUFA) chemotherapy and observation. The prognostic and predictive values of PoT/PoS measurements were determined by the use of stratified log-rank analyses. A high proportion of tumour stroma (≥50%) was associated with an increased recurrence risk: 31.3% (143/457) recurrence for ≥50% versus 21.9% (294/1343) for <50% [rate ratio (RR) 1.62; 95% confidence interval (CI) 1.30-2.02; P < 0.0001]. Of patients with stromal proportions of ≥65%, 40% (46/115) had recurrent disease within 10 years. The adverse prognostic effect of a high stromal proportion was independent of established prognostic variables, and was maintained in stage II/Dukes B patients (RR 1.62; 95% CI 1.26-2.08; P = 0.0002). KRAS mutation in the presence of a high stromal proportion augmented recurrence risk (RR 2.93; 95% CI 1.87-4.59; P = 0.0005). Stromal morphometry did not predict response to FUFA chemotherapy.

CONCLUSIONS

Simple digital morphometry applied to a single representative H&E section identifies CRC patients with a >50% higher risk of disease recurrence. This technique can reliably partition patients into subpopulations with different risks of tumour recurrence in a simple and cost-effective manner. Further prospective validation is warranted.

The significance of lumican expression in ovarian cancer drug-resistant cell lines

PURPOSE

The aim of the present study is to determine the expression of LUM in drug-resistant ovarian cancer cell lines.

METHODS

Doxorubicin- (DOX), topotecan- (TOP) and vincristine- (VIN) resistant variants of the W1 ovarian cancer cell line were used in this study. We used quantitative real-time polymerase chain reactions to determine LUM mRNA levels. Protein expression was detected using Western blot and immunocytochemistry assays. Protein glycosylation was investigated using PGNase F digestion. Immunohistochemistry assays were used to determine protein expression in ovarian cancer patients.

RESULTS

We observed increased expression of LUM in drug-resistant cell lines at both the mRNA and the protein level. The most abundant LUM expression was observed in TOP-resistant cell line. We observed LUM bands that corresponded to different molecular masses, and the most abundant LUM form was the secreted form, which had a mass of 50 kDa. Double immunofluorescence analysis showed co-expression of LUM and COL3A1 as well as the presence of extracellular COL3A1 in the TOP-resistant cell line. Finally, we detected the LUM protein in ovarian cancer tissue.

CONCLUSION

The expression of LUM in cytostatic-resistant cell lines suggests its role in drug resistance. The co-expression of LUM and COL3A1 indicates the significance of LUM in collagen fibre assembly. Expression in ovarian cancer tissue suggests that LUM can play a role in ovarian cancer pathogenesis in ways similar to other cancers.

Blocking integrin β1 decreases adhesion in chemoresistant urothelial cancer cell lines

Treatment failure in metastatic bladder cancer is commonly caused by acquisition of resistance to chemotherapy in association with tumor progression. Since alterations of integrins can influence the adhesive and invasive behaviors of urothelial bladder cancer cell lines, the present study aimed to evaluate the role of integrins in bladder cancer cells with acquired resistance to standard first-line chemotherapy with gemcitabine, and cisplatin. Therefore, four gemcitabine- and four cisplatin-resistant sublines out of a panel of four parental urothelial bladder cancer cell lines (TCC-SUP, HT1376, T24, and 5637) were used. Expression of integrin subunits α3, α5, α6, β1, β3, and β4 was detected using flow cytometry. Adhesion and chemotaxis were analyzed. For functional assays, integrin β1 was attenuated with a blocking antibody. In untreated cells, chemotaxis was upregulated in 3/4 gemcitabine-resistant sublines. In cisplatin-resistant cells, chemotaxis was enhanced in 2/4 cell lines. Acquired chemoresistance induced the upregulation of integrin β1 in all four tested gemcitabine-resistant sublines, as well as an upregulation in 3/4 cisplatin-resistant sublines compared with parental cell lines. Following the inhibition of integrin β1, adhesion to extracellular matrix components was downregulated in 3/4 gemcitabine-resistant sublines and in all four tested cisplatin-resistant sublines. Since integrin β1 is frequently upregulated in chemoresistant urothelial cancer cell lines and inhibition of integrin β1 may influence adhesion, further studies are warranted to evaluate integrin β1 as a potential therapeutic target for bladder cancer in vivo.

Tumor engraftment in patient-derived xenografts of pancreatic ductal adenocarcinoma is associated with adverse clinicopathological features and poor survival

Patient-derived xenograft (PDX) tumors are powerful tools to study cancer biology. However, the ability of PDX tumors to model the biological and histological diversity of pancreatic ductal adenocarcinoma (PDAC) is not well known. In this study, we subcutaneously implanted 133 primary and metastatic PDAC tumors into immunodeficient mice. Fifty-seven tumors were successfully engrafted and even after extensive passaging, the histology of poorly-, moderately-, and well-differentiated tumors was maintained in the PDX models. Moreover, the fibroblast and collagen contents in the stroma of patient tumors were recapitulated in the corresponding PDX models. Analysis of the clinicopathological features of patients revealed xenograft tumor engraftment was associated with lymphovascular invasion (P = 0.001) and worse recurrence-free (median, 7 vs. 16 months, log-rank P = 0.047) and overall survival (median, 13 vs. 21 months, log-rank P = 0.038). Among successful engraftments, median time of growth required for reimplantation into new mice was 151 days. Reflective of the inherent biological diversity between PDX tumors with rapid (<151 days) and slow growth, differences in their growth were maintained during extensive passaging. Rapid growth was additionally associated with lymph node metastasis (P = 0.022). The association of lymphovascular invasion and lymph node metastasis with PDX formation and rapid growth may reflect an underlying biological mechanism that allows these tumors to adapt and grow in a new environment. While the ability of PDX tumors to mimic the cellular and non-cellular features of the parental tumor stroma provides a valuable model to study the interaction of PDAC cells with the tumor microenvironment, the association of successful engraftment with adverse clinicopathological features suggests PDX models over represent more aggressive forms of this disease.

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.

Expression of podoplanin in stromal fibroblasts plays a pivotal role in the prognosis of patients with pancreatic cancer

Purpose

To investigate the role of podoplanin (PDPN) expression in invasive ductal carcinoma of the pancreas (IDCP) in humans.

Methods

Tumor samples were obtained from 95 patients with IDCP. Immunohistochemical staining was done to evaluate the expression of PDPN in cancer tissues.

Results

PDPN was detected predominantly in stromal fibroblasts, stained with α-smooth muscle actin. The cutoff value of PDPN-positive areas was calculated according to a histogram. There was no significant difference in clinicopathologic factors between patients with high vs. those with low PDPN expression. The high PDPN group showed significantly poorer disease-free and disease-specific survival rates than the low PDPN group. Among patients from the high PDPN group, those with lymph node metastases and those with a tumor larger than 20 cm in diameter had significantly poorer prognoses than similar patients from the low PDPN group. Multivariate Cox proportional hazards analysis indicated that a high expression of PDPN was an independent risk factor for disease-specific survival.

Conclusions

PDPN expression in cancer-related fibrotic tissues is associated with a poor prognosis, especially in patients with large tumors or lymph node metastases.

Micro-RNA-21 Regulates Cancer-Associated Fibroblast-Mediated Drug Resistance in Pancreatic Cancer

Pancreatic ductal adenocarcinoma (PDAC) is one of the leading causes of cancer deaths due to its highly aggressive biological nature and resistance to chemotherapy. Previous studies indicate that miR-21 is an important regulator in the activation of cancer-associated fibroblasts (CAFs). However, whether miR-21 in CAFs would regulate PDAC’s tumor microenvironment and lead to drug resistance remain unknown. In this study, we evaluated the relationship between CAF activation, miR-21 expression, and drug resistance using tumor samples from PDAC patients. We changed the miR-21 expression level in CAFs and tested its roles in regulating the function of CAFs. In addition, we explored the roles of miR-21 in CAFs in the development of PDAC using an animal model. We found that PDAC patients who were resistant to gemcitabine treatment tended to have higher miR-21 expression and more activated CAFs. An in vitro study showed that CAFs with high miR-21 expression had elevated MMP-3, MMP-9, PDGF, and CCL-7 expression and promoted the invasion of PDAC cell lines. miR-21 overexpression also contributed to the activation of CAFs by regulating the PDCD4 gene. The in vivo study showed that upregulating miR-21 in CAFs promoted PDAC desmoplasia and increased its drug resistance to gemcitabine treatment, but downregulating miR-21 in CAFs suppressed desmoplasia and enhanced the effect of gemcitabine. We concluded that miR-21 promoted the activation of CAFs and contributed to the drug resistance of PDAC.

Targeting stroma in pancreatic cancer: Promises and failures of targeted therapies

Desmoplasia or abundant fibrotic stroma is a typical property of most malignancies, which has a great effect on tumorigenesis, angiogenesis, and resistance to therapy. The activated stroma cells comprises several cell types including endothelial cells, nerve cells, inflammatory/macrophages cells, stellate cells, and extracellular matrix. In other word, the interactions of cancer-stroma modulate tumorigenesis, therapy resistance, and poor delivery of drugs. Therefore, targeting the tumor stroma in combination with conventional chemotherapeutic agents could provide a promising approach in the treatment of pancreatic cancer. This review summarizes the current knowledge about pancreatic stellate cells, targeting stroma compartments with particular emphasis on preclinical, and clinical trials on targeting of stroma as an option in pancreatic cancer treatment.

Nanomedicine as a potent strategy in melanoma tumor microenvironment

Melanoma originated from melanocytes is the most aggressive type of skin cancer. Despite considerable progresses in clinical treatment with the discovery of BRAF or MEK inhibitors and monoclonal antibodies, the durability of response to treatment is often limited to the development of acquired resistance and systemic toxicity. The limited success of conventional treatment highlights the importance of understanding the role of melanoma tumor microenvironment in tumor developement and drug resistance. Nanoparticles represent a promising strategy for the development of new cancer treatments able to improve the bioavailability of drugs and increase their penetration by targeting specifically tumors cells and/or tumor environment. In this review, we will discuss the main influence of tumor microenvironment in melanoma growth and treatment outcome. Furthermore, third generation loaded nanotechnologies represent an exciting tool for detection, treatment, and escape from possible mechanism of resistance mediated by tumor microenvironment, and will be highlighted in this review.

Microenvironment in determining chemo-resistance in pancreatic cancer: Neighborhood matters

Every year, nearly 300,000 people are diagnosed with pancreatic cancer worldwide, and an equivalent number succumb to this disease. One of the major challenges of pancreatic cancer that contributes to its poor survival rates is the development of resistance to the standard chemotherapy. Heterogeneity of the tumor, the dense fibroblastic stroma, and the aggressive biology of the tumor all contribute to the chemoresistant phenotype. In addition, the acellular components of the tumor microenvironment like hypoxia, stress pathways in the stromal cells, and the cytokines that are secreted by the immune cells, have a definitive role in orchestrating the chemoresistant property of the tumor. In this review, we systematically focus on the role played by the different microenvironmental components in determining chemoresistance of pancreatic tumors.

Ex Vivo Testing of Patient-Derived Xenografts Mirrors the Clinical Outcome of Patients with Pancreatic Ductal Adenocarcinoma

PURPOSE

Translation of the patient-derived xenograft (PDX) model into a method for practical personalized cancer treatment is prevented by the intense resources and time necessary to generate and test each tumorgraft. We aimed to develop a high-throughput ex vivo drug testing approach that can be used for personalized cancer treatment design.

EXPERIMENTAL DESIGN

We developed a unique ex vivo live tissue sensitivity assay (LTSA), in which precision-cut and uniform small tissue slices derived from pancreatic ductal adenocarcinoma PDX tumors were arrayed in a 96-well plate and screened against clinically relevant regimens within 3 to 5 days. The correlation between the sensitivities of tissue slices to the regimens and patients' clinical responses and outcome were statistically analyzed. The results of LTSA assay were further confirmed with biochemical methods in vitro and animal PDX model in vivo RESULTS: The ex vivo tissue slices remain viable for at least 5 days, and the tumor parenchyma, including stroma, vascular structures, and signaling pathways, are all retained. The sensitivities of the ex vivo tissue slices to gemcitabine and irinotecan was consistent with the clinical responses and outcomes of the patients from whom the tumorgrafts were derived (r = 0.77; P = 0.0002). Retrospective analysis showed that the patients who received LTSA-sensitive regimens had remarkably longer progression-free survival than patients who received LTSA-resistant regimens (16.33 vs. 3.8 months; n = 18, P = 0.011).

CONCLUSIONS

The results from these PDX and LTSA methods reflect clinical patients' responses and could be used as a personalized strategy for improving systemic therapy effectiveness in patients with pancreatic cancer. Clin Cancer Res; 22(24); 6021-30. ©2016 AACR.

Tissue Transglutaminase Activates Cancer-Associated Fibroblasts and Contributes to Gemcitabine Resistance in Pancreatic Cancer

Resistance to chemotherapy is a hallmark of pancreatic ductal adenocarcinoma (PDA) and has been partly attributed to the dense desmoplastic stroma, which forms a protective niche for cancer cells. Tissue transglutaminase (TG2), a Ca²⁺-dependent enzyme, is secreted by PDA cells and cross-links proteins in the tumor microenvironment (TME) through acyl-transfer between glutamine and lysine residues, promoting PDA growth. The objective of the current study was to determine whether secreted TG2 by PDA cells alters the response of pancreatic tumors to gemcitabine. Orthotopic pancreatic xenografts and co-culture of PDA and stromal cells were employed to determine the mechanisms by which TG2 alters tumor-stroma interactions and response to gemcitabine. Analysis of the pancreatic The Cancer Genome Atlas (TCGA) database demonstrated that increased TG2 expression levels correlate with worse overall survival (hazard ratio = 1.37). Stable TG2 knockdown in PDA cells led to decreased size of pancreatic xenografts and increased sensitivity to gemcitabine in vivo. However, TG2 downregulation did not increase cytotoxicity of gemcitabine in vitro. Additionally, multivessel density and gemcitabine uptake in pancreatic tumor tissue, as measured by mass spectrometry (MS-HPLC), were not significantly different in tumors expressing TG2 versus tumors in which TG2 was knocked down. Fibroblasts, stimulated by TG2 secreted by PDA cells, secrete laminin A1, which protects cancer cells from gemcitabine-induced cytotoxicity. In all, our results demonstrate that TG2 secreted in the pancreatic TME orchestrates the cross talk between cancer cells and stroma, impacting tumor growth and response to chemotherapy. Our study supports TG2 inhibition to increase the antitumor effects of gemcitabine in PDA.

Pancreatic stellate cell secreted IL-6 stimulates STAT3 dependent invasiveness of pancreatic intraepithelial neoplasia and cancer cells

Pancreatic ductal adenocarcinoma (PDAC) is a dynamic tumor supported by several stromal elements such as pancreatic stellate cells (PSC). Significant crosstalk exists between PSCs and tumor cells to stimulate oncogenic signaling and malignant progression of PDAC. However, how PSCs activate intercellular signaling in PDAC cells remains to be elucidated. We have previously shown that activated signal transducer and activator of transcription 3 (STAT3) signaling is a key component in the progression of pancreatic neoplasia. We hypothesize that PSC secreted IL-6 activates STAT3 signaling to promote PanIN progression to PDAC. Human PDAC and mouse PanIN cells were treated with PSC-conditioned media (PSC-CM), and phospho- and total-STAT3 levels by immunoblot analysis were determined. IL-6 was quantified in PSC-CM and cell invasion and colony formation assays were performed in the presence or absence of a neutralizing IL-6 antibody and the JAK/STAT3 inhibitor AZD1480. Serum from Ptf1aCre/+;LSL-KrasG12D/+;Tgfbr2flox/flox (PKT) and LSL-KrasG12D/+; Trp53R172H/+; Pdx1Cre/+ (KPC) mice demonstrated increased levels of IL-6 compared to serum from non-PDAC bearing KC and PK mice. PSC secreted IL-6 activated STAT3 signaling in noninvasive, precursor PanIN cells as well as PDAC cells, resulting in enhanced cell invasion and colony formation in both cell types. There was a significant positive linear correlation between IL-6 concentration and the ratio of phosphorylated STAT3/total STAT3. IL-6 neutralization or STAT3 inhibition attenuated PSC-CM induced activation of STAT3 signaling and tumorigenicity. These data provide evidence that PSCs are directly involved in promoting the progression of PanINs towards invasive carcinoma. This study demonstrates a novel role of PSC secreted IL-6 in transitioning noninvasive pancreatic precursor cells into invasive PDAC through the activation of STAT3 signaling.

Irreversible electroporation enhances delivery of gemcitabine to pancreatic adenocarcinoma

INTRODUCTION

Irreversible electroporation (IRE) utilizes short, high-voltage pulses to irreversibly permeabilize the cell membrane, resulting in apoptotic cell death. In addition to the irreversible zone, IRE creates a reversible zone that could be utilized for enhanced drug delivery. The hypothesis of this study is that a zone of reversible electroporation exists and allows for increased chemotherapy delivery.

METHODS

Ten immunocompromised mice with orthotopic human pancreatic adenocarcinoma tumors (Panc1) were treated with either IRE between two doses of gemcitabine (15 mg/kg) (ECT) (N = 5) or gemcitabine alone (N = 5). Gemcitabine levels in the serum, liver, and pancreas were analyzed with liquid chromatography/mass spectrometry (LC/MS).

RESULTS

Concentration of gemcitabine within reversibly electroporated pancreatic tissue was higher in mice receiving ECT compared to those receiving gemcitabine alone (13,567 ng/ml vs.4,126 ng/ml; P = 0.0009). Pancreatic gemcitabine levels were 5.52 and 5.96 times higher than liver and serum levels, respectively, in the ECT group compared to 2.85 and 2.53 times higher (P = 0.117, P = 0.058), respectively, in mice receiving gemcitabine alone.

CONCLUSION

IRE can potentially reduce local recurrence by allowing increased drug delivery to the tissue in the reversible electroporation zone. This holds significant potential in augmenting efficacy of gemcitabine in treatment of locally advanced and borderline resectable pancreatic adenocarcinoma. J. Surg. Oncol. 2016;114:181-186. © 2016 Wiley Periodicals, Inc.

Increased Expression of Several Collagen Genes is Associated with Drug Resistance in Ovarian Cancer Cell Lines

Ovarian cancer is the most lethal gynaecological cancer. The main reason for the high mortality among ovarian cancer patients is the development of drug resistance. The expression of collagen genes by cancer cells can increase drug resistance by inhibiting the penetration of the drug into the cancer tissue as well as increase apoptosis resistance. In this study, we present data that shows differential expression levels of collagen genes and proteins in cisplatin- (CIS), paclitaxel- (PAC), doxorubicin- (DOX), topotecan- (TOP), vincristine- (VIN) and methotrexate- (MTX) resistant ovarian cancer cell lines. Quantitative real-time polymerase chain reactions were performed to determine the mRNA levels. Protein expression was detected using Western blot and immunocytochemistry assays. In the drug resistant cell lines, we observed the upregulation of eight collagen genes at the mRNA level and based on these expression levels, we divided the collagen genes into the following three groups:

1. Genes with less than a 50-fold increase in expression: COL1A1, COL5A2, COL12A1 and COL17A1. 2. Genes with greater than a 50-fold increase in expression: COL1A2, COL15A1 and COL21A1. 3. Gene with a very high level of expression: COL3A1. Expression of collagen (COL) proteins from groups 2 and 3 were also confirmed using immunocytochemistry. Western blot analysis showed very high expression levels of COL3A1 protein, and immunocytochemistry analysis showed the presence of extracellular COL3A1 in the W1TR cell line. The cells mainly responsible for the extracellular COL3A1 production are aldehyde dehydrogenase-1A1 (ALDH1A1) positive cells. All correlations between the types of cytostatic drugs and the expression levels of different COL genes were studied, and our results suggest that the expression of fibrillar collagens may be involved in the TOP and PAC resistance of the ovarian cancer cells. The expression pattern of COL genes provide a preliminary view into the role of these proteins in cytostatic drug resistance of cancer cells. The exact role of these COL genes in drug resistance requires further investigation.

Diffusion-weighted and dynamic contrast-enhanced MRI of pancreatic adenocarcinoma xenografts: associations with tumor differentiation and collagen content

PURPOSE

The aggressiveness of pancreatic ductal adenocarcinoma (PDAC) is highly dependent on the level of differentiation and the composition of the stroma. In this preclinical study, we investigated the potential of diffusion-weighted magnetic resonance imaging (DW-MRI) and dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) as noninvasive methods for providing information on the differentiation and the stroma of PDACs.

METHODS

Xenografted tumors initiated from four PDAC cell lines (BxPC-3, Capan-2, MIAPaCa-2, and Panc-1) were included in the study. DW-MRI and DCE-MRI were carried out on a 7.05-T MR scanner, and tumor images of ADC (the apparent diffusion coefficient), K (trans) (the volume transfer constant of Gd-DOTA), and v e (the fractional distribution volume of Gd-DOTA) were produced. The level of differentiation and the amount and structure of collagen I and collagen IV were determined by examining histological preparations.

RESULTS

Differentiated tumors showed lower levels of collagen I and collagen IV than non-differentiated tumors. Significant correlations were found between ADC and v e, and both parameters differentiated clearly between collagen-rich non-differentiated tumors and differentiated tumors containing less collagen.

CONCLUSION

Differentiated PDAC xenografts show higher ADC values and higher v e values than their non-differentiated counterparts. This observation supports the application of parametric MR images as tumor biomarkers in PDAC. Patients showing low values of ADC and v e most likely have non-differentiated tumors with extensive stroma and, hence, poor prognosis.

Radiation Therapy Induces Macrophages to Suppress T-Cell Responses Against Pancreatic Tumors in Mice

BACKGROUND & AIMS

The role of radiation therapy in the treatment of patients with pancreatic ductal adenocarcinoma (PDA) is controversial. Randomized controlled trials investigating the efficacy of radiation therapy in patients with locally advanced unresectable PDA have reported mixed results, with effects ranging from modest benefit to worse outcomes compared with control therapies. We investigated whether radiation causes inflammatory cells to acquire an immune-suppressive phenotype that limits the therapeutic effects of radiation on invasive PDAs and accelerates progression of preinvasive foci.

METHODS

We investigated the effects of radiation therapy in p48(Cre);LSL-Kras(G12D) (KC) and p48(Cre);LSLKras(G12D);LSL-Trp53(R172H) (KPC) mice, as well as in C57BL/6 mice with orthotopic tumors grown from FC1242 cells derived from KPC mice. Some mice were given neutralizing antibodies against macrophage colony-stimulating factor 1 (CSF1 or MCSF) or F4/80. Pancreata were exposed to doses of radiation ranging from 2 to 12 Gy and analyzed by flow cytometry.

RESULTS

Pancreata of KC mice exposed to radiation had a higher frequency of advanced pancreatic intraepithelial lesions and more foci of invasive cancer than pancreata of unexposed mice (controls); radiation reduced survival time by more than 6 months. A greater proportion of macrophages from radiation treated invasive and preinvasive pancreatic tumors had an immune-suppressive, M2-like phenotype compared with control mice. Pancreata from mice exposed to radiation had fewer CD8(+) T cells than controls, and greater numbers of CD4(+) T cells of T-helper 2 and T-regulatory cell phenotypes. Adoptive transfer of T cells from irradiated PDA to tumors of control mice accelerated tumor growth. Radiation induced production of MCSF by PDA cells. A neutralizing antibody against MCSF prevented radiation from altering the phenotype of macrophages in tumors, increasing the anti-tumor T-cell response and slowing tumor growth.

CONCLUSIONS

Radiation treatment causes macrophages murine PDA to acquire an immune-suppressive phenotype and disabled T-cell-mediated anti-tumor responses. MCSF blockade negates this effect, allowing radiation to have increased efficacy in slowing tumor growth.

Orchestrating the Tumor Microenvironment to Improve Survival for Patients With Pancreatic Cancer: Normalization, Not Destruction

Pancreatic cancer is the fourth leading cause of cancer death in the United States. The microenvironment of pancreatic cancer could be one of the "perfect storms" that support the growth of a cancer. Indeed, pancreatic cancer may be the poster child of a problem with the microenvironment. In this article, we review the rationale and attempts to date on modifying or targeting structural proteins in the microenvironment including hyaluronan (HA) (in primary and metastases), collagen, and SPARC (secreted protein, acidic, and rich in cysteine). Indeed, working in this area has produced a regimen that improves survival for patients with advanced pancreatic cancer (nab-paclitaxel + gemcitabine). In addition, in initial clinical trials, PEGylated hyaluronidase appears promising. We also review a new approach that is different than targeting/destroying the microenvironment and that is orchestrating, reengineering, reprogramming, or normalizing the microenvironment (including normalizing structural proteins, normalizing an immunologically tumor-friendly environment to a less friendly environment, reversing epithelial-to-mesenchymal transition, and so on). We believe this will be most effectively done by agents that have global effects on transcription. There is initial evidence that this can be done by agents such as vitamin D derivatives and other new agents. There is no doubt these opportunities can now be tried in the clinic with hopefully beneficial effects.

Phenotypic and functional heterogeneity of cancer-associated fibroblast within the tumor microenvironment

Cancer microenvironment is created not only by malignant epithelial cells, but also by several kinds of stromal cells. Since Paget proposed the "seed and soil" hypothesis, the biological importance of the cancer microenvironment has come to be widely accepted. The main compartment of host stromal cells are fibroblasts (Cancer-Associated Fibroblasts; CAFs), which are the main source of the collagen-producing cells. CAFs directly communicate with the cancer cells and other types of stromal cells to acquire a specific biological phenotype. CAFs play important roles in several aspects of the tumor progression process and the chemotherapeutic process. However, CAFs have heterogeneous origins, phenotypes, and functions under these conditions. A crucial challenge is to understand how much of this heterogeneity serves different biological responses to cancer cells. In this review, we highlight the issue of how diverse and heterogeneous functions given by CAFs can exert potent influences on tumor progression and therapeutic response. Furthermore, we also discuss the current advances in the development of novel therapeutic strategies against CAFs.

Chemotherapy-Induced Inflammatory Gene Signature and Protumorigenic Phenotype in Pancreatic CAFs via Stress-Associated MAPK

Pancreatic ductal adenocarcinoma (PDAC) has a characteristically dense stroma comprised predominantly of cancer-associated fibroblasts (CAF). CAFs promote tumor growth, metastasis, and treatment resistance. This study aimed to investigate the molecular changes and functional consequences associated with chemotherapy treatment of PDAC CAFs. Chemoresistant immortalized CAFs (R-CAF) were generated by continuous incubation in gemcitabine. Gene expression differences between treatment-naïve CAFs (N-CAF) and R-CAFs were compared by array analysis. Functionally, tumor cells (TC) were exposed to N-CAF- or R-CAF-conditioned media and assayed for migration, invasion, and viability in vitro Furthermore, a coinjection (TC and CAF) model was used to compare tumor growth in vivo R-CAFs increased TC viability, migration, and invasion compared with N-CAFs. In vivo, TCs coinjected with R-CAFs grew larger than those accompanied by N-CAFs. Genomic analysis demonstrated that R-CAFs had increased expression of various inflammatory mediators, similar to the previously described senescence-associated secretory phenotype (SASP). In addition, SASP mediators were found to be upregulated in response to short duration treatment with gemcitabine in both immortalized and primary CAFs. Inhibition of stress-associated MAPK signaling (P38 MAPK or JNK) attenuated SASP induction as well as the tumor-supportive functions of chemotherapy-treated CAFs in vitro and in vivo These results identify a negative consequence of chemotherapy on the PDAC microenvironment that could be targeted to improve the efficacy of current therapeutic regimens.

IMPLICATIONS

Chemotherapy treatment of pancreatic cancer-associated fibroblasts results in a proinflammatory response driven by stress-associated MAPK signaling that enhances tumor cell growth and invasiveness. Mol Cancer Res; 14(5); 437-47. ©2016 AACR.

An MMP-2 Responsive Liposome Integrating Antifibrosis and Chemotherapeutic Drugs for Enhanced Drug Perfusion and Efficacy in Pancreatic Cancer

Fibrotic stroma, a critical character of pancreatic tumor microenvironment, provides a critical barrier against the penetration and efficacy of various antitumor drugs. Therefore, new strategies are urgently needed to alleviate the fibrotic mass and increase the drug perfusion within pancreatic cancer tissue. In our current work, we developed a β-cyclodextrin (β-CD) modified matrix metalloproteinase-2 (MMP-2) responsive liposome, integrating antifibrosis and chemotherapeutic drugs for regulation of pancreatic stellate cells (PSCs), a key source of the fibrosis, and targeted delivery of cytotoxic drugs for pancreatic cancer therapy. These liposomes disassembed into two functional parts upon MMP-2 cleavage at the tumor site. One part was constituted by the β-CDs and the antifibrosis drug pirfenidone, which was kept in the stroma and inhibited the expression of collagen I and TGF-β in PSCs, down-regulating the fibrosis and decreasing the stromal barrier. The other segment, the RGD peptide-modified-liposome loading the chemotherapeutic drug gemcitabine, targeted and killed pancreatic tumor cells. This integrated nanomedicine, showing an increased drug perfusion without any overt side effects, may provide a potential strategy for improvement of the pancreatic cancer therapy.

Quantitative proteomics and phosphoproteomics on serial tumor biopsies from a sorafenib-treated HCC patient

Compensatory signaling pathways in tumors confer resistance to targeted therapy, but the pathways and their mechanisms of activation remain largely unknown. We describe a procedure for quantitative proteomics and phosphoproteomics on snap-frozen biopsies of hepatocellular carcinoma (HCC) and matched nontumor liver tissue. We applied this procedure to monitor signaling pathways in serial biopsies taken from an HCC patient before and during treatment with the multikinase inhibitor sorafenib. At diagnosis, the patient had an advanced HCC. At the time of the second biopsy, abdominal imaging revealed progressive disease despite sorafenib treatment. Sorafenib was confirmed to inhibit MAPK signaling in the tumor, as measured by reduced ribosomal protein S6 kinase phosphorylation. Hierarchical clustering and enrichment analysis revealed pathways broadly implicated in tumor progression and resistance, such as epithelial-to-mesenchymal transition and cell adhesion pathways. Thus, we describe a protocol for quantitative analysis of oncogenic pathways in HCC biopsies and obtained first insights into the effect of sorafenib in vivo. This protocol will allow elucidation of mechanisms of resistance and enable precision medicine.

Matrix control of pancreatic cancer: New insights into fibronectin signaling

Pancreatic ductal adenocarcinoma (PDA) is a highly metastatic disease that resists most current therapies. A defining characteristic of PDA is an intense fibrotic response that promotes tumor cell invasion and chemoresistance. Efforts to understand the complex relationship between the tumor and its extracellular network and to therapeutically perturb tumor-stroma interactions are ongoing. Fibronectin (FN), a provisional matrix protein abundant in PDA stroma but not normal tissues, supports metastatic spread and chemoresistance of this deadly disease. FN also supports angiogenesis, which is required for even hypovascular tumors such as PDA to develop and progress. Targeting components of the tumor stroma, such as FN, can effectively reduce tumor growth and spread while also enhancing delivery of chemotherapy. Here, we review the molecular mechanisms by which FN drives angiogenesis, metastasis and chemoresistance in PDA. In light of these new findings, we also discuss therapeutic strategies to inhibit FN signaling.

Tumor specific liposomes improve detection of pancreatic adenocarcinoma in vivo using optoacoustic tomography

Background

Pancreatic cancer often goes undiagnosed until late stage disease due in part to suboptimal early detection. Our goal was to develop a Syndecan-1 tagged liposome containing fluorescent dye as an improved contrast agent for detection of pancreatic adenocarcinoma in vivo using multispectral optoacoustic tomography.

Results

The diagnostic capabilities and specificity to pancreatic adenocarcinoma of Syndecan-1 targeted liposomes were evaluated both in vitro and in vivo. Immunocytochemistry showed that liposomes preferentially bound to and released their contents into cells expressing high levels of insulin-like growth factor 1 receptor. We determined that the contents of the liposome were released into the cell as noted by the change in propidium iodide fluorescence from green to red based upon nucleic acid binding. In an orthotopic mouse model, the liposomes preferentially targeted the pancreatic tumor with little off-target binding in the liver and spleen. Peak accumulation of the liposomes in the tumor occurred at 8 h post-injection. Multispectral optoacoustic tomographic imaging was able to provide high-resolution 3D images of the tumor and liposome location. Ex vivo analysis showed that non-targeted liposomes accumulated in the liver, suggesting that specificity of the liposomes for pancreatic adenocarcinoma was due to the presence of the Syndecan-1 ligand.

Conclusions

This study demonstrated that Syndecan-1 liposomes were able to release cargo into IGF1-R expressing tumor cells. The Syndecan-1 liposomes demonstrated tumor specificity in orthotopic pancreatic cancer as observed using multispectral optoacoustic tomography with reduced kidney and liver uptake. By targeting the liposome with Syndecan-1, this nanovehicle has potential as a targeted theranostic nanoparticle for both drug and contrast agent delivery to pancreatic tumors.

Electronic supplementary material

The online version of this article (doi:10.1186/s12951-015-0139-8) contains supplementary material, which is available to authorized users.

Gemcitabine-releasing mesenchymal stromal cells inhibit in vitro proliferation of human pancreatic carcinoma cells

BACKGROUND AIMS

Pancreatic cancer (pCa) is a tumor characterized by a fibrotic state and associated with a poor prognosis. The observation that mesenchymal stromal cells (MSCs) migrate toward inflammatory micro-environments and engraft into tumor stroma after systemic administration suggested new therapeutic approaches with the use of engineered MSCs to deliver and produce anti-cancer molecules directly within the tumor. Previously, we demonstrated that without any genetic modifications, MSCs are able to deliver anti-cancer drugs. MSCs loaded with paclitaxel by exposure to high concentrations release the drug both in vitro and in vivo, inhibiting tumor proliferation. On the basis of these observations, we evaluated the ability of MSCs (from bone marrow and pancreas) to uptake and release gemcitabine (GCB), a drug widely used in pCa treatment.

METHODS

MSCs were primed by 24-h exposure to 2000 ng/mL of GCB. The anti-tumor potential of primed MSCs was then investigated by in vitro anti-proliferation assays with the use of CFPAC-1, a pancreatic tumor cell line sensitive to GCB. The uptake/release ability was confirmed by means of high-performance liquid chromatography analysis. A cell-cycle study and secretome evaluation were also conducted to better understand the characteristics of primed MSCs.

RESULTS

GCB-releasing MSCs inhibit the growth of a human pCa cell line in vitro.

CONCLUSIONS

The use of MSCs as a "trojan horse" can open the way to a new pCa therapeutic approach; GCB-loaded MSCs that integrate into the tumor mass could deliver much higher concentrations of the drug in situ than can be achieved by intravenous injection.

Tissue Transglutaminase Mediated Tumor-Stroma Interaction Promotes Pancreatic Cancer Progression

PURPOSE

Aggressive pancreatic cancer is commonly associated with a dense desmoplastic stroma, which forms a protective niche for cancer cells. The objective of the study was to determine the functions of tissue transglutaminase (TG2), a Ca(2+)-dependent enzyme that cross-links proteins through transamidation and is abundantly expressed by pancreatic cancer cells in the pancreatic stroma.

EXPERIMENTAL DESIGN

Orthotopic pancreatic xenografts and coculture systems tested the mechanisms by which the enzyme modulates tumor-stroma interactions.

RESULTS

We show that TG2 secreted by cancer cells effectively molds the stroma by cross-linking collagen, which, in turn, activates fibroblasts and stimulates their proliferation. The stiff fibrotic stromal reaction conveys mechanical cues to cancer cells, leading to activation of the YAP/TAZ transcription factors, promoting cell proliferation and tumor growth. Stable knockdown of TG2 in pancreatic cancer cells leads to decreased size of pancreatic xenografts.

CONCLUSIONS

Taken together, our results demonstrate that TG2 secreted in the tumor microenvironment orchestrates the cross-talk between cancer cells and stroma fundamentally affecting tumor growth. Our study supports TG2 inhibition in the pancreatic stroma as a novel strategy to block pancreatic cancer progression.

The role of pancreatic stellate cells in pancreatic cancer

BACKGROUND

The prognosis of pancreatic cancer remains desperately poor, with little progress made over the past 30 years despite the development of new combination chemotherapy regimens. Stromal activity is especially prominent in the tissue surrounding pancreatic tumours, and has a profound influence in dictating tumour development and dissemination. Pancreatic stellate cells (PaSCs) have a key role in this tumour microenvironment, and have been the subject of much research in the past decade. This review examines the relationship between PaSCs and cancer cells.

METHODS

A comprehensive literature search was performed of multiple databases up to March 2014, including Medline, Pubmed and Google Scholar.

RESULTS

A complex bidirectional interplay exists between PaSCs and cancer cells, resulting in a perpetuating loop of increased activity and an overriding pro-tumorigenic effect. This involves a number of signalling pathways that also impacts on other stromal components and vasculature, contributing to chemoresistance. The Reverse Warburg Effect is also introduced as a novel concept in tumour stroma.

CONCLUSION

This review highlights the pancreatic tumour microenvironment, and in particular PaSCs, as an ideal target for therapeutics. There are a number of cellular processes involving PaSCs which could hold the key to more effectively treating pancreatic cancer. The feasibility of targeting these pathways warrant further in depth investigation, with the aim of reducing the aggressiveness of pancreatic cancer and improving chemodelivery.

The inhibition of renin-angiotensin system in advanced pancreatic cancer: an exploratory analysis in 349 patients

PURPOSE

The role of local renin-angiotensin system (RAS) as a target for the treatment of pancreatic cancer has been increasingly reported, but the addition of candesartan, one of angiotensin system inhibitors (ASIs), to gemcitabine in our prospective trial failed to demonstrate activity against pancreatic cancer. The aim of this study was to explore subgroups that would benefit from the inhibition of RAS by the use of ASIs.

METHODS

Consecutive patients with advanced pancreatic cancer receiving gemcitabine-based chemotherapy were retrospectively studied. Hazard ratios (HRs) for overall survival (OS) and progression-free survival (PFS) were estimated by a Cox proportional hazards model. Interactions between the use of ASIs and each subgroup were tested.

RESULTS

Between 2001 and 2013, 349 patients received gemcitabine-based chemotherapy for advanced pancreatic cancer; 232 were metastatic, 210 received gemcitabine monotherapy, 108 took ASIs, 166 were never smokers and 188 were diabetic. The median PFS and OS were 4.9 and 11.2 months, respectively. When the effects of the use of ASIs were evaluated by a Cox proportional hazard model, there were two subgroups with P interaction <0.10 both in PFS and OS: never smokers and gemcitabine monotherapy. HRs for PFS and OS by the inhibition of RAS were 0.71 (P = 0.021) and 0.68 (P = 0.014) in never smokers and 0.70 (P = 0.027) and 0.77 (P = 0.124) in patients receiving gemcitabine monotherapy.

CONCLUSION

The inhibition of RAS in advanced pancreatic cancer might improve clinical outcomes in cases without a history of smoking or in cases receiving gemcitabine monotherapy.