Pancreatic cancer microenvironment

Pancreatic ductal adenocarcinoma: From genetics to biology to radiobiology to oncoimmunology and all the way back to the clinic

Pancreatic ductal adenocarcinoma (PDAC) is the fourth leading cause of cancer death. Despite improvements in the clinical management, the prognosis of PDAC remains dismal. In the present comprehensive review, we will examine the knowledge of PDAC genetics and the new insights into human genome sequencing and clonal evolution. Additionally, the biology and the role of the stroma in tumour progression and response to treatment will be presented. Furthermore, we will describe the evidence on tumour chemoresistance and radioresistance and will provide an overview on the recent advances in PDAC metabolism and circulating tumour cells. Next, we will explore the characteristics and merits of the different mouse models of PDAC. The inflammatory milieu and the immunosuppressive microenvironment mediate tumour initiation and treatment failure. Hence, we will also review the inflammatory and immune escaping mechanisms and the new immunotherapies tested in PDAC. A better understanding of the different mechanisms of tumour formation and progression will help us to identify the best targets for testing in future clinical studies of PDAC.

Desmoplasia and chemoresistance in pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) occurs mainly in people older than 50 years of age. Although great strides have been taken in treating PDAC over the past decades its incidence nearly equals its mortality rate and it was quoted as the 4th leading cause of cancer deaths in the U.S. in 2012. This review aims to focus on research models and scientific developments that help to explain the extraordinary resistance of PDAC towards current therapeutic regimens. Furthermore, it highlights the main features of drug resistance including mechanisms promoted by cancer cells or cancer stem cells (CSCs), as well as stromal cells, and the acellular components surrounding the tumor cells-known as peritumoral desmoplasia-that affects intra-tumoral drug delivery. Finally, therapeutic concepts and avenues for future research are suggested, based on the topics discussed.

Depletion of RhoGDI2 expression inhibits the ability of invasion and migration in pancreatic carcinoma

Rho GDP dissociation inhibitor 2 (RhoGDI2) has been identified as a regulator of tumor metastasis, although its role in tumor progression remains controversial. In this study, we examined the expression of RhoGDI2 in PC tissues and cell lines. To investigate the function of RhoGDI2 in PC cells, RhoGDI2 expression was depleted in PANC-1 and Patu8988 cells by small interfering RNA (siRNA). RhoGDI2 was found to be overexpressed in pancreatic carcinoma (PC) tissues and PC cell lines. Additionally, the results showed that depletion of RhoGDI2 significantly inhibited cell motility and invasion in vitro, but did not affect cell proliferation. The clinical study together with the experimental data confirmed that RhoGDI2 modulated the expression of matrix metalloproteinase 2 (MMP2). Taken together, findings of the present study indicated that RhoGDI2 is involved in pancreatic tumor malignancy and metastasis. Thus, RhoGDI2 is a potential target for the gene therapy of PC.

Anti-Bv8 antibody and metronomic gemcitabine improve pancreatic adenocarcinoma treatment outcome following weekly gemcitabine therapy

Weekly gemcitabine therapy is the major treatment offered for patients with pancreatic adenocarcinoma cancer; however, relative resistance of tumor cells to chemotherapy, rapid regrowth, and metastasis are the main causes of death within a year. Recently, the daily continuous administration of chemotherapy in low doses--called metronomic chemotherapy (MC)--has been shown to inhibit primary tumor growth and delay metastases in several tumor types; however, its use as a single therapy is still in question due to its moderate therapeutic benefit. Here, we show that the combination of weekly gemcitabine with MC of the same drug delays tumor regrowth and inhibits metastasis in mice implanted orthotopically with pancreatic tumors. We further demonstrate that weekly gemcitabine, but not continuous MC gemcitabine or the combination of the two drug regimens, promotes rebound myeloid-derived suppressor cell (MDSC) mobilization and increases angiogenesis in this tumor model. Furthermore, Bv8 is highly expressed in MDSCs colonizing pancreatic tumors in mice treated with weekly gemcitabine compared to MC gemcitabine or the combination of the two regimens. Blocking Bv8 with antibodies in weekly gemcitabine-treated mice results in a significant reduction in tumor regrowth, angiogenesis, and metastasis. Overall, our results suggest that pro-tumorigenic effects induced by weekly gemcitabine are mediated in part by MDSCs expressing Bv8. Therefore, both Bv8 inhibition and MC can be used as legitimate 'add-on' treatments for preventing post-chemotherapy pancreatic cancer recurrence, progression, and metastasis following weekly gemcitabine therapy.

Phase II trial of vatalanib in patients with advanced or metastatic pancreatic adenocarcinoma after first-line gemcitabine therapy (PCRT O4-001)

PURPOSE

Vatalanib (PTK 787/ZK22584) is an oral poly-tyrosine kinase inhibitor with strong affinity for platelet-derived growth factor and vascular endothelial growth factor (VEGF) receptors. We conducted an open-label, phase II multicenter therapeutic trial investigating the efficacy and tolerability of vatalanib in patients with metastatic or advanced pancreatic cancer who failed first-line gemcitabine-based therapy.

METHODS

Vatalanib treatment consisted of a twice daily oral dosing using a "ramp-up schedule," beginning with 250 mg bid during week 1,500 mg bid during week 2, and 750 mg bid on week three and thereafter. The primary objective of this study was to evaluate the 6-month survival rate.

RESULTS

Sixty-seven patients were enrolled. The median age was 64, and 66% (N = 43) had only one prior regimen. Common grade 3/4 adverse events included hypertension (20%; N = 13), fatigue (17%; N = 11), abdominal pain (17%; N = 11), and elevated alkaline phosphatase (15%; N = 10). Among the 65 evaluable patients, the 6-month survival rate was 29% (95% CI 18-41%) and the median progression-free survival was 2 months. Fifteen patients survived 6 months or more. Two patients had objective partial responses, and 28% of patients had stable disease. Changes in biomarkers including soluble VEGF and vascular endothelial growth factor receptor did not correlate with response to drug.

CONCLUSION

Vatalanib was well tolerated as a second-line therapy and resulted in favorable 6-month survival rate in patients with metastatic pancreatic cancer, compared with historic controls.

A Listeria vaccine and depletion of T-regulatory cells activate immunity against early stage pancreatic intraepithelial neoplasms and prolong survival of mice

BACKGROUND & AIMS

Premalignant lesions and early stage tumors contain immunosuppressive microenvironments that create barriers for cancer vaccines. Kras(G12D/+);Trp53(R172H/+);Pdx-1-Cre (KPC) mice, which express an activated form of Kras in pancreatic tissues, develop pancreatic intraepithelial neoplasms (PanIN) that progress to pancreatic ductal adenocarcinoma (PDA). We used these mice to study immune suppression in PDA.

METHODS

We immunized KPC and Kras(G12D/+);Pdx-1-Cre mice with attenuated intracellular Listeria monocytogenes (which induces CD4(+) and CD8(+) T-cell immunity) engineered to express Kras(G12D) (LM-Kras). The vaccine was given alone or in sequence with an anti-CD25 antibody (PC61) and cyclophosphamide to deplete T-regulatory (Treg) cells. Survival times were measured; pancreatic and spleen tissues were collected and analyzed by histologic, flow cytometry, and immunohistochemical analyses.

RESULTS

Interferon γ-mediated, CD8(+) T-cell responses were observed in KPC and Kras(G12D/+);Pdx-1-Cre mice given LM-Kras, but not in unvaccinated mice. Administration of LM-Kras to KPC mice 4-6 weeks old (with early stage PanINs), depleted of Treg cells, significantly prolonged survival and reduced PanIN progression (median survival, 265 days), compared with unvaccinated mice (median survival, 150 days; P = .002), mice given only LM-Kras (median survival, 150 days; P = .050), and unvaccinated mice depleted of Treg cells (median survival, 170 days; P = .048). In 8- to 12-week-old mice (with late-stage PanINs), LM-Kras, alone or in combination with Treg cell depletion, did not increase survival time or slow PanIN progression. The combination of LM-Kras and Treg cell depletion reduced numbers of Foxp3(+)CD4(+) T cells in pancreatic lymph nodes, increased numbers of CD4(+) T cells that secrete interleukin 17 and interferon γ, and caused CD11b(+)Gr1(+) cells in the pancreas to acquire an immunostimulatory phenotype.

CONCLUSIONS

Immunization of KPC mice with Listeria monocytogenes engineered to express Kras(G12D), along with depletion of Treg cells, reduces progression of early stage, but not late-stage, PanINs. This approach increases infiltration of the lesion with inflammatory cells. It might be possible to design immunotherapies against premalignant pancreatic lesions to slow or prevent progression to PDA.

Pancreatic cancer cell glycosylation regulates cell adhesion and invasion through the modulation of α2β1 integrin and E-cadherin function

In our previous studies we have described that ST3Gal III transfected pancreatic adenocarcinoma Capan-1 and MDAPanc-28 cells show increased membrane expression levels of sialyl-Lewis x (SLe(x)) along with a concomitant decrease in α2,6-sialic acid compared to control cells. Here we have addressed the role of this glycosylation pattern in the functional properties of two glycoproteins involved in the processes of cancer cell invasion and migration, α2β1 integrin, the main receptor for type 1 collagen, and E-cadherin, responsible for cell-cell contacts and whose deregulation determines cell invasive capabilities. Our results demonstrate that ST3Gal III transfectants showed reduced cell-cell aggregation and increased invasive capacities. ST3Gal III transfected Capan-1 cells exhibited higher SLe(x) and lower α2,6-sialic acid content on the glycans of their α2β1 integrin molecules. As a consequence, higher phosphorylation of focal adhesion kinase tyrosine 397, which is recognized as one of the first steps of integrin-derived signaling pathways, was observed in these cells upon adhesion to type 1 collagen. This molecular mechanism underlies the increased migration through collagen of these cells. In addition, the pancreatic adenocarcinoma cell lines as well as human pancreatic tumor tissues showed colocalization of SLe(x) and E-cadherin, which was higher in the ST3Gal III transfectants. In conclusion, changes in the sialylation pattern of α2β1 integrin and E-cadherin appear to influence the functional role of these two glycoproteins supporting the role of these glycans as an underlying mechanism regulating pancreatic cancer cell adhesion and invasion.

Comparative characterization of stroma cells and ductal epithelium in chronic pancreatitis and pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is characterized by an extensive stroma being also present in chronic pancreatitis (CP). Using immunohistochemistry, the stroma of CP and PDAC was comprehensively analyzed and correlated with epithelial/carcinoma-related alterations and clinicopathological patient characteristics. While there were no significant differences between CP and PDAC regarding the distribution of CD3+ T cells and α-SMA+ fibroblasts, proportions of CD4+ and CD8+ T cells were significantly lower and numbers of CD25+(CD4+) and FoxP3+(CD4+) regulatory T cells were greater in PDAC compared with CP. Macrophages were more prevalent in CP, but localized more closely to carcinoma cells in PDAC, as were γδ-T cells. Duct-related FoxP3 and L1CAM expression increased from CP to PDAC, while vimentin expression was similarly abundant in both diseases. Moreover, stromal and epithelial compartments of well-differentiated tumors and CPs shared considerable similarities, while moderately and poorly differentiated tumors significantly differed from CP tissues. Analysis of 27 parameters within each pancreatic disease revealed a significant correlation of i) CD4+ and FoxP3+CD4+ T cells with FoxP3 expression in PDAC cells, ii) α-SMA+ fibroblasts with L1CAM expression and proliferation in PDAC cells, iii) CD3 and CD8 expression with γδ-TCR expression in both pancreatic diseases and iv) CD68+ and CD163+ macrophages with vimentin expression in PDAC cells. High expression of FoxP3, vimentin and L1CAM in PDAC cells as well as a tumor-related localization of macrophages each tended to correlate with higher tumor grade. Multivariate survival analysis revealed a younger age at time of surgery as a positive prognostic marker for PDAC patients with the most frequently operated disease stage T3N1M0. Overall this study identified several interrelationships between stroma and epithelial/carcinoma cells in PDACs but also in CP, which in light of previous experimental data strongly support the view that the inflammatory stroma contributes to malignancy-associated alterations already in precursor cells during CP.

L1CAM promotes enrichment of immunosuppressive T cells in human pancreatic cancer correlating with malignant progression

Regulatory T cell (T-reg) enrichment in the tumor microenvironment is regarded as an important mechanism of tumor immune escape. Hence, the presence of T-regs in highly malignant pancreatic ductal adenocarcinoma (PDAC) is correlated with short survival. Likewise, the adhesion molecule L1CAM is upregulated during PDAC progression in the pancreatic ductal epithelium also being associated with poor prognosis. To investigate whether L1CAM contributes to enrichment of T-regs in PDAC, human CD4(+)CD25(+)CD127(-)CD49d(-) T-regs and CD4(+)CD25(-) T-effector cells (T-effs) were isolated by magnetic bead separation from blood of healthy donors. Their phenotype and functional behavior were analyzed in dependence on human premalignant (H6c7) or malignant (Panc1) pancreatic ductal epithelial cells, either exhibiting or lacking L1CAM expression. T cells derived from blood and tumors of PDAC patients were analyzed by flow cytometry and findings were correlated with clinical parameters. Predominantly T-regs but not T-effs showed an increased migration on L1CAM expressing H6c7 and Panc1 cells. Whereas proliferation of T-regs did not change in the presence of L1CAM, T-effs proliferated less, exhibited a decreased CD25 expression and an increased expression of CD69. Moreover, these T-effs exhibited a regulatory phenotype as they inhibited proliferation of autologous T cells. Accordingly, CD4(+)CD25(-)CD69(+) T cells were highly abundant in PDAC tissues compared to blood being associated with nodal invasion and higher grading in PDAC patients. Overall, these data point to an important role of L1CAM in the enrichment of immunosuppressive T cells in particular of a CD4(+)CD25(-)CD69(+)-phenotype in PDAC providing a novel mechanism of tumor immune escape which contributes to tumor progression.

Tumor-associated macrophages exhibit pro- and anti-inflammatory properties by which they impact on pancreatic tumorigenesis

Pancreatic ductal adenocarcinoma (PDAC) still ranking 4th in the order of fatal tumor diseases is characterized by a profound tumor stroma with high numbers of tumor-associated macrophages (TAMs). Driven by environmental factors, monocytes differentiate into M1- or M2-macrophages, the latter commonly regarded as being protumorigenic. Because a detailed analysis of TAMs in human PDAC development is still lacking, freshly isolated PDAC-derived TAMs were analyzed for their phenotype and impact on epithelial-mesenchymal-transition (EMT) of benign (H6c7) and malignant (Colo357) pancreatic ductal epithelial cells. TAMs exhibited characteristics of M1-macrophages (expression of HLA-DR, IL-1β, or TNF-α) and M2-macrophages (expression of CD163 and IL-10). In the presence of TAMs, H6c7, and Colo357 cells showed an elongated cell shape along with an increased expression of mesenchymal markers such as vimentin and reduced expression of epithelial E-cadherin. Similar to TAMs, in vitro generated M1- and M2-macrophages both mediated EMT in H6c7 and Colo357 cells. M1-macrophages acquired M2-characteristics during coculture that could be prevented by GM-CSF treatment. However, M1-macrophages still potently induced EMT in H6c7 and Colo357 cells although lacking M2-characteristics. Overall, these data demonstrate that TAMs exhibit anti- as well as proinflammatory properties that equally contribute to EMT induction in PDAC initiation and development.

Cell surface sialic acid modulates extracellular matrix adhesion and migration in pancreatic adenocarcinoma cells

OBJECTIVES

Tumor cells modulate their extracellular matrix (ECM) adhesion and migration to become more metastatic. Moreover, they show an increase in sialic acid, which could have an effect on their ECM adhesion and migration. This work describes the influence of pancreatic adenocarcinoma cell surface α2,3- and α2,6-sialic acid determinants on the aforementioned processes.

METHODS

We have characterized the cell surface α2,3- and α2,6-sialic acids, and sialyl-Lewis x levels and the integrin levels of 2 pancreatic adenocarcinoma cell lines, Capan-1 and MDAPanc-28, grown at different cell densities, and also of the ST3Gal III overexpressing Capan-1 cells, C31. We have measured their adhesion to several ECM proteins and their migration through collagen with and without blocking their sialic acid determinants.

RESULTS

Adhesion to ECM proteins of Capan-1 and MDAPanc-28 grown at different cell densities, and of C31, depended on their cell surface sialic acid determinants repertoire, correlating the higher α2,6-sialic acid levels with their increased ECM adhesion. Cell migration also depended on their sialic acid determinants expression; and in this case, higher α2,3-sialic acid levels correlated with a more migratory phenotype.

CONCLUSION

This study shows how the intrinsic heterogeneity of cell membrane sialylation regulates the adhesive and migratory potential of pancreatic adenocarcinoma cells.

Mucins in pancreatic cancer and its microenvironment

Pancreatic cancer remains a lethal malignancy with poor prognosis owing to therapeutic resistance, frequent recurrence and the absence of treatment strategies that specifically target the tumour and its supporting stroma. Deregulated cell-surface proteins drive neoplastic transformations and are envisioned to mediate crosstalk between the tumour and its microenvironment. Emerging studies have elaborated on the role of mucins in diverse biological functions, including enhanced tumorigenicity, invasiveness, metastasis and drug resistance through their characteristic O-linked and N-linked oligosaccharides (glycans), extended structures and unique domains. Multiple mucin domains differentially interact and regulate different components of the tumour microenvironment. This Review discusses: the expression pattern of various mucins in the pancreas under healthy, inflammatory, and cancerous conditions; the context-dependent attributes of mucins that differ under healthy and pathological conditions; the contribution of the tumour microenvironment in pancreatic cancer development and/or progression; diagnostic and/or prognostic efficacy of mucins; and mucin-based therapeutic strategies. Overall, this information should help to delineate the intricacies of pancreatic cancer by exploring the family of mucins, which, through various mechanisms in both tumour cells and the microenvironment, worsen disease outcome.

Tumoral epithelial and stromal expression of SMAD proteins in pancreatic ductal adenocarcinomas

BACKGROUND

SMAD proteins, intracellular mediators of the transforming growth factor (TGF)-beta pathway, function within two axes, the SMAD1/5/8 and SMAD2/3, connected to TGF-beta and bone morphogenetic protein (BMP) ligands. The SMAD proteins of these two axes dimerize with SMAD4 and translocate to the nucleus. SMAD signaling is characterized by a dichotomic functioning, with tumor-suppressive functions and with loss of normal growth inhibitory responses, depending on the carcinogenesis stage. SMAD proteins also have pro-tumor effects including abnormal extracellular matrix production. Among tumors, pancreatic cancers harbor SMAD4 inactivation the most frequently and the SMAD proteins are considered to be key factors in pancreatic carcinogenesis.

METHODS

Our aims were to study the expression patterns of the different types of SMAD proteins in pancreatic ductal adenocarcinomas treated by surgical resection (without neoadjuvant treatment) and their correlations with morphological and clinical characteristics. We examined the immunohistochemical expression of SMAD4, SMAD1/5/8, and SMAD2/3 in 99 pancreatic ductal adenocarcinomas. Antibodies directed against the activated, phosphorylated forms of proteins were used when appropriate (SMAD1/5/8, SMAD2/3). Protein expression in the epithelial tumor cells and in stromal fibroblasts was analyzed with regard to morphological and clinical data.

RESULTS

Epithelial tumor cells showed SMAD1/5/8, SMAD2/3, and, SMAD4 expression in 13, 93, and 45 tumors, respectively, and stromal fibroblast expression in 5, 11, and 22 tumors, respectively. Epithelial SMAD4 was associated with a low, T1 or T2, TNM stage, and with the presence of an abundant stroma (p = 0.05 and <0.01, respectively). Activated stromal fibroblast SMAD2/3 expression was correlated with the presence of a fibrotic focus (p = 0.01), whereas fibroblast SMAD4 was related to a tendency for shorter postsurgical overall survival (p = 0.07). The relationship of stromal, fibroblast SMAD4 to a worse outcome attained statistical significance in the group of patients with T1 and with N1 stage tumors (p < 0.01 and p = 0.04, respectively).

CONCLUSION

In pancreatic ductal adenocarcinomas, SMAD protein expression in epithelial tumor cells or in stromal fibroblasts was related to stromal features and to a shorter postsurgical overall survival. Our results point out that the SMAD proteins play a role in the microenvironment of this highly fibrotic tumor type.

Immune infiltrates as predictive markers of survival in pancreatic cancer patients

Pancreatic cancer is a devastating disease with dismal prognosis. The tumor microenvironment is composed by multiple cell types, molecular factors, and extracellular matrix forming a strong desmoplastic reaction, which is a hallmark of the disease. A complex cross-talk between tumor cells and the stroma exists with reciprocal influence that dictates tumor progression and ultimately the clinical outcome. In this context, tumor infiltrating immune cells through secretion of chemokine and cytokines exert an important regulatory role. Here we review the correlation between the immune infiltrates, evaluated on tumor samples of pancreatic cancer patients underwent surgical resection, and disease free and/or overall survival after surgery. Specifically, we focus on tumor infiltrating lymphocytes (TILs), mast cells (MCs) and macrophages that all contribute to a Th2-type inflammatory and immunosuppressive microenvironment. In these patients tumor immune infiltrates not only do not contribute to disease eradication but rather the features of Th2-type inflammation and immunosuppression is significantly associated with more rapid disease progression and reduced survival.

Monoclonal antibodies and other targeted therapies for pancreatic cancer

Pancreatic cancer continues to be a challenging disease to treat because of its aggressive nature, advanced stage at the time of diagnosis, and limited treatment options that are available. Traditional cytotoxic chemotherapy provides modest benefit to patients with pancreatic adenocarcinoma. Recently, a FOLFIRINOX regimen revealed improved response in overall and progression-free survival over single-agent gemcitabine in metastatic pancreatic cancer, but there is still much needed advancement in the systemic treatment of pancreatic cancer. There is a growing interest in the development of novel agents, while our understanding of molecular pathogenesis of pancreatic adenocarcinoma continues to expand. With identification of various molecular pathways in pancreatic cancer tumorigenesis, potential targets for drug development have been pursued with the use of monoclonal antibodies and small-molecule inhibitors. Although preclinical studies with multiple targeted therapies demonstrated encouraging results in pancreatic cancer, only erlotinib, an epidermal growth factor receptor inhibitor, showed a marginal survival benefit in a phase III clinical trial, when combined with gemcitabine. As further signaling pathways and their importance in pancreatic cancer tumorigenesis are better understood, further clinical trials will need to be designed to study these targeted agents as single agents, in combination with other novel agents or in combination with cytotoxic chemotherapy. In this review, we present the current knowledge on targeted therapy in pancreatic adenocarcinoma and its application in clinical practice.

Tumour-stroma interactions in pancreatic ductal adenocarcinoma: rationale and current evidence for new therapeutic strategies

Most patients with pancreatic cancer present with advanced/metastatic disease and have a dismal prognosis. Despite the proven albeit modest benefits of gemcitabine demonstrated over a decade ago, subsequent advances have been slow, suggesting it may be time to take a different approach. It is thought that some key characteristics of pancreatic cancer, such as the desmoplasia, restricted vasculature and hypoxic environment, may prevent the delivery of chemotherapy to the tumour thereby explaining the limited benefits observed to-date. Moreover, there is evidence to suggest that the stroma is not only a mechanical barrier but also constitutes a dynamic compartment of pancreatic tumours that is critically involved in tumour formation, progression and metastasis. Thus, targeting the stroma and the tumour represents a promising therapeutic strategy. Currently, several stroma-targeting agents are entering clinical development. Among these, nab-paclitaxel appears promising since it combines cytotoxic therapy with targeted delivery via its proposed ability to bind SPARC on tumour and stromal cells. Preclinical data indicate that co-treatment with nab-paclitaxel and gemcitabine results in stromal depletion, increased tumour vascularization and intratumoural gemcitabine concentration, and increased tumour regression compared with either agent alone. Phase I/II study data also suggest that a high level of antitumor activity can be achieved with this combination in pancreatic cancer. This was recently confirmed in a Phase III study which showed that nab-paclitaxel plus gemcitabine significantly improved overall survival (HR 0.72) and progression-free survival (HR 0.69) versus gemcitabine alone for the first-line treatment of patients with metastatic pancreatic cancer.

Detection of hypoxia with 18F-fluoromisonidazole (18F-FMISO) PET/CT in suspected or proven pancreatic cancer

PURPOSE OF THE REPORT

Pancreatic carcinoma is known to demonstrate molecular features of hypoxia. The aim of this prospective pilot study is to analyze the hypoxia agent fluoromisonidazole (FMISO) using PET/CT in pancreatic carcinoma and to compare FMISO activity with glucose metabolism reflected by FDG.

PATIENTS AND METHODS

Ten patients with pancreatic carcinoma underwent FMISO and FDG PET scans. FMISO and FDG PET/CT scans were analyzed by 2 PET physicians. Regions of interest drawn on the FDG images were transposed to the FMISO images after study coregistration. The FDG SUVmax was used to quantify metabolic activity and FMISO SUVmax and tumor-to-background (muscle) ratio to quantify hypoxia.

RESULTS

Seven patients were diagnosed with pancreatic adenocarcinoma. The remaining patients had a neuroendocrine tumor, poorly differentiated/sarcomatoid carcinoma, and mucinous neoplasm. Visual analysis demonstrated increased FMISO activity in 2 pancreatic adenocarcinomas. All patients, however, had increased FDG activity at the tumor site. Mean FDG SUVmax was 6 (range: 3.8 to 9.5) compared to 2.3 for FMISO (range: 1 to 3.4). The 2 positive studies on visual analysis of FMISO did not correspond to the largest tumors, the studies with the highest FMISO or FDG SUVmax. There was no significant correlation between FMISO and FDG SUVmax values.

CONCLUSIONS

The hypoxia imaging agent, FMISO, demonstrates minimal activity in pancreatic tumors. If FMISO PET/CT is to be included in clinical trial protocols of hypoxia in pancreatic cancer, it would require correlation with other imaging modalities to localize the tumor and allow semiquantitative analysis.

A preclinical evaluation of Minnelide as a therapeutic agent against pancreatic cancer

Pancreatic cancer is one of the most lethal human malignancies with an all-stage 5-year survival frequency of <5%, which highlights the urgent need for more effective therapeutic strategies. We have previously shown that triptolide, a diterpenoid, is effective against pancreatic cancer cells in vitro as well as in vivo. However, triptolide is poorly soluble in water, limiting its clinical use. We therefore synthesized a water-soluble analog of triptolide, named Minnelide. The efficacy of Minnelide was tested both in vitro and in multiple independent yet complementary in vivo models of pancreatic cancer: an orthotopic model of pancreatic cancer using human pancreatic cancer cell lines in athymic nude mice, a xenograft model where human pancreatic tumors were transplanted into severe combined immunodeficient mice, and a spontaneous pancreatic cancer mouse model (KRas(G12D); Trp53(R172H); Pdx-1Cre). In these multiple complementary models of pancreatic cancer, Minnelide was highly effective in reducing pancreatic tumor growth and spread, and improving survival. Together, our results suggest that Minnelide shows promise as a potent chemotherapeutic agent against pancreatic cancer, and support the evaluation of Minnelide in clinical trials against this deadly disease.

Persistent activation of pancreatic stellate cells creates a microenvironment favorable for the malignant behavior of pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is one of the most common malignant tumors with poor prognosis due to extremely high malignancy, low rate of eligibility for surgical resection and chemoradiation resistance. Increasing evidence indicate that the interaction between activated pancreatic stellate cells (PSCs) and PDAC cells plays an important role in the development of PDAC. By producing high levels of cytokines, chemotactic factors, growth factors and excessive extracellular matrix (ECM), PSCs create desmoplasia and a hypoxic microenvironment that promote the initiation, development, evasion of immune surveillance, invasion, metastasis and resistance to chemoradiation of PDAC. Therefore, targeting the interaction between PSCs and PDAC cells may represent a novel therapeutic approach to advanced PDAC, especially therapies that target PSCs of the pancreatic tumor microenvironment.

3D pancreatic carcinoma spheroids induce a matrix-rich, chemoresistant phenotype offering a better model for drug testing

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) is the fourth most common cause of cancer related death. It is lethal in nearly all patients, due to an almost complete chemoresistance. Most if not all drugs that pass preclinical tests successfully, fail miserably in the patient. This raises the question whether traditional 2D cell culture is the correct tool for drug screening. The objective of this study is to develop a simple, high-throughput 3D model of human PDAC cell lines, and to explore mechanisms underlying the transition from 2D to 3D that might be responsible for chemoresistance.

METHODS

Several established human PDAC and a KPC mouse cell lines were tested, whereby Panc-1 was studied in more detail. 3D spheroid formation was facilitated with methylcellulose. Spheroids were studied morphologically, electron microscopically and by qRT-PCR for selected matrix genes, related factors and miRNA. Metabolic studies were performed, and a panel of novel drugs was tested against gemcitabine.

RESULTS

Comparing 3D to 2D cell culture, matrix proteins were significantly increased as were lumican, SNED1, DARP32, and miR-146a. Cell metabolism in 3D was shifted towards glycolysis. All drugs tested were less effective in 3D, except for allicin, MT100 and AX, which demonstrated effect.

CONCLUSIONS

We developed a high-throughput 3D cell culture drug screening system for pancreatic cancer, which displays a strongly increased chemoresistance. Features associated to the 3D cell model are increased expression of matrix proteins and miRNA as well as stromal markers such as PPP1R1B and SNED1. This is supporting the concept of cell adhesion mediated drug resistance.

Low-dose gemcitabine depletes regulatory T cells and improves survival in the orthotopic Panc02 model of pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is one of the most aggressive human neoplasms with extremely poor prognosis and a low survival rate. Immunosuppressive cell populations, e.g. regulatory T cells (Treg), appear to be important in PDAC, contributing to patient's poor prognosis. Therefore, we investigated the PDAC microenvironment with a focus on conventional and regulatory T cells in view of their potential therapeutic importance. We found that tumors from the murine Panc02 orthotopic model of PDAC were infiltrated with high numbers of Treg. Remarkably, these cells exhibited the effector/memory phenotype, suggesting their enhanced suppressive activity and higher proliferation capacity. Although we observed a steady increase in transforming growth factor-β (TGF-β) levels in the tumors, treatment with a specific inhibitor of TGF-β receptor I kinase failed to abrogate Treg accumulation. A CCR4 antagonist did not affect Treg percentage in the tumor either. However, intense Treg cell division in the tumor microenvironment was demonstrated, suggesting local proliferation as a major mechanism of Treg accumulation in PDAC. Notably, this accumulation was reduced by low-dose gemcitabine administration, resulting in a modestly increased survival of PDAC mice. Our results provide an insight into mechanisms of immunosuppression in PDAC, suggesting an important role for proliferative expansion of effector/memory Treg. Low-dose gemcitabine therapy selectively depletes Treg, providing a basis for new modalities of PDAC therapy.

Tumor-stromal interactions in pancreatic cancer

Pancreatic adenocarcinoma has one of the worse prognoses of any cancer with a 5-year survival of only 3%. Pancreatic cancer displays one of the most prominent stromal reactions of all tumors and it is evident that this is a key contributing factor to disease outcome. The tumor microenvironment of pancreatic cancer harbors a wide spectrum of cell types and a complex network of mechanisms which all serve to promote tumor progression. It is clear that the symbiotic relationship between pancreatic cancer cells and stellate cells is the chief factor creating this unique tumor milieu. Pancreatic stellate cells play critical roles in evasion of cancer cell apoptosis, invasion and metastases, angiogenesis, and promotion of an immunosuppressive environment, all key hallmarks of malignancy. Existing treatments for pancreatic cancer focus on targeting the cancer cells rather than the whole tumor, of which cancer cells represent a small proportion. It is now increasingly evident that research targeted towards the interactions between these cell types, ideally at an early stage of tumor development, is imperative in order to propel the way forward to more effective treatments.

Polymorphonuclear neutrophils promote dyshesion of tumor cells and elastase-mediated degradation of E-cadherin in pancreatic tumors

Pancreatic ductal adenocarcinoma (PDAC) presenting with a micropapillary growth pattern is frequently associated with a prominent neutrophil infiltration into the tumor. The relevance of neutrophil infiltrates for tumor progression, however, is still debated. To gain insight into the role of polymorphonuclear neutrophils (PMNs) in PDAC, we assessed their effect on pancreatic tumor cells grown in vitro as monolayers. Time-lapse video microscopy showed a PMN-induced dyshesion of the tumor cells, and subsequent experiments revealed that this dyshesion was due to PMN elastase-mediated degradation of E-cadherin, an adhesion molecule that mediates the intercellular contact of the tumor cells. E-cadherin degradation by elastase or--(for comparison) down-modulation by specific siRNA, significantly increased the migratory capacity of the pancreatic tumor cells, leading to the hypothesis that PMNs could contribute to the invasive tumor growth. To address this issue, biopsies of patients with PDAC (n = 112) were analyzed. We found that E-cadherin expression correlated negatively with PMN infiltration, compatible with the notion that E-cadherin is cleaved by PMN-derived elastase, which in turn could result in the dispersal of the tumor cells, enhanced migratory capacity and thus invasive tumor growth.

Molecular markers associated with outcome and metastasis in human pancreatic cancer

Background

Pancreatic ductal adenocarcinoma (PDAC) is a heterogeneous cancer in which differences in survival rates might be related to a variety in gene expression profiles. Although the molecular biology of PDAC begins to be revealed, genes or pathways that specifically drive tumour progression or metastasis are not well understood.

Methods

We performed microarray analyses on whole-tumour samples of 2 human PDAC subpopulations with similar clinicopathological features, but extremely distinct survival rates after potentially curative surgery, i.e. good outcome (OS and DFS > 50 months, n = 7) versus bad outcome (OS < 19 months and DFS < 7 months, n = 10). Additionally, liver- and peritoneal metastases were analysed and compared to primary cancer tissue (n = 11).

Results

The integrin and ephrin receptor families were upregulated in all PDAC samples, irrespective of outcome, supporting an important role of the interaction between pancreatic cancer cells and the surrounding desmoplastic reaction in tumorigenesis and cancer progression. Moreover, some components such as ITGB1 and EPHA2 were upregulated in PDAC samples with a poor outcome, Additionally, overexpression of the non-canonical Wnt/β-catenin pathway and EMT genes in PDAC samples with bad versus good outcome suggests their contribution to the invasiveness of pancreatic cancer, with β-catenin being also highly upregulated in metastatic tissue.

Conclusions

Components of the integrin and ephrin pathways and EMT related genes, might serve as molecular markers in pancreatic cancer as their expression seems to be related with prognosis.

Oncogenic Kras-induced GM-CSF production promotes the development of pancreatic neoplasia

Stromal responses elicited by early stage neoplastic lesions can promote tumor growth. However, the molecular mechanisms that underlie the early recruitment of stromal cells to sites of neoplasia remain poorly understood. Here, we demonstrate an oncogenic Kras(G12D)-dependent upregulation of GM-CSF in mouse pancreatic ductal epithelial cells (PDECs). An enhanced GM-CSF production is also observed in human PanIN lesions. Kras(G12D)-dependent production of GM-CSF in vivo is required for the recruitment of Gr1(+)CD11b(+) myeloid cells. The suppression of GM-CSF production inhibits the in vivo growth of Kras(G12D)-PDECs, and, consistent with the role of GM-CSF in Gr1(+)CD11b(+) mobilization, this effect is mediated by CD8(+) T cells. These results identify a pathway that links oncogenic activation to the evasion of antitumor immunity.

A KrasG12D-driven genetic mouse model of pancreatic cancer requires glypican-1 for efficient proliferation and angiogenesis

Pancreatic ductal adenocarcinomas (PDACs) exhibit multiple molecular alterations and overexpress heparin-binding growth factors (HBGFs) and glypican-1 (GPC1), a heparan sulfate proteoglycan that promotes efficient signaling by HBGFs. It is not known, however, whether GPC1 has a role in genetic mouse models of PDAC. Therefore, we generated a GPC1 null mouse that combines pancreas-specific Cre-mediated activation of oncogenic Kras (Kras(G12D)) with deletion of a conditional INK4A/Arf allele (Pdx1-Cre;LSL-Kras(G12D);INK4A/Arf(lox/lox);GPC1(-/-) mice). By comparison with Pdx1-Cre;LSL-Kras(G12D);INK4A/Arf(lox/lox) mice that were wild type for GPC1, the Pdx1-Cre;LSL-Kras(G12D);INK4A/Arf(lox/lox);GPC1(-/-) mice exhibited attenuated pancreatic tumor growth and invasiveness, decreased cancer cell proliferation and mitogen-activated protein kinase activation. These mice also exhibited suppressed angiogenesis in conjunction with decreased expression of messenger RNAs encoding several pro-angiogenic factors and molecules, including vascular endothelial growth factor-A (VEGF-A), SRY-box containing gene (SOX17), chemokine C-X3-C motif ligand 1 (CX3CL1) and integrin β3 (ITGB3). Moreover, pancreatic cancer cells isolated from the tumors of GPC1(-/-) mice were not as invasive in response to fibroblast growth factor-2 (FGF-2) as cancer cells isolated from wild-type mice, and formed smaller tumors that exhibited an attenuated metastatic potential. Similarly, VEGF-A and FGF-2 did not enhance the migration of hepatic endothelial cells and immortalized murine embryonic fibroblasts isolated from GPC1 null mice. These data demonstrate in an oncogenic Kras-driven genetic mouse model of PDAC that tumor growth, angiogenesis and invasion are enhanced by GPC1, and suggest that suppression of GPC1 may be an important component of therapeutic strategies in PDAC.

Identification of serum biomarker signatures associated with pancreatic cancer

Pancreatic cancer is an aggressive disease with poor prognosis, due, in part, to the lack of disease-specific biomarkers that could afford early and accurate diagnosis. With a recombinant antibody microarray platform, targeting mainly immunoregulatory proteins, we screened sera from 148 patients with pancreatic cancer, chronic pancreatitis, autoimmune pancreatitis (AIP), and healthy controls (N). Serum biomarker signatures were derived from training cohorts and the predictive power was evaluated using independent test cohorts. The results identified serum portraits distinguishing pancreatic cancer from N [receiver operating characteristics area under the curve (AUC) of 0.95], chronic pancreatitis (0.86), and AIP (0.99). Importantly, a 25-serum biomarker signature discriminating pancreatic cancer from the combined group of N, chronic pancreatitis, and AIP was determined. This signature exhibited a high diagnostic potential (AUC of 0.88). In summary, we present the first prevalidated, multiplexed serum biomarker signature for diagnosis of pancreatic cancer that may improve diagnosis and prevention in premalignant diseases and in screening of high-risk individuals.

Cationic liposomal paclitaxel plus gemcitabine or gemcitabine alone in patients with advanced pancreatic cancer: a randomized controlled phase II trial

BACKGROUND

Paclitaxel embedded in cationic liposomes (EndoTAG™-1; ET) is an innovative agent targeting tumor endothelial cells. This randomized controlled phase II trial evaluated the safety and efficacy of ET in combination with gemcitabine (GEM) in advanced pancreatic cancer (PDAC).

PATIENTS AND METHODS

Chemotherapy-naive patients with locally advanced or metastatic disease were randomly assigned to receive weekly GEM 1000 mg/m(2) or GEM plus twice-weekly ET 11, 22 or 44 mg/m(2) for 7 weeks. After a safety run-in of 100 patients, a second cohort continued treatment. End points included overall survival (OS), progression-free survival (PFS), tumor response and safety.

RESULTS

Two hundred and twelve patients were randomly allocated to the study and 200 were treated (80% metastatic, 20% locally advanced). Adverse events were manageable and reversible. Transient thrombocytopenia and infusion reactions with chills and pyrexia mostly grade 1 or 2 occurred in the ET groups. Disease control rate after the first treatment cycle was 43% with GEM and 60%, 65% and 52% in the GEM + ET cohorts. Median PFS reached 2.7 compared with 4.1, 4.6 and 4.4 months, respectively. Median OS was 6.8 compared with 8.1, 8.7 and 9.3 months, respectively.

CONCLUSIONS

Treatment of advanced PDAC with GEM + ET was generally well tolerated. GEM + ET showed beneficial survival and efficacy. A randomized phase III trial should confirm this positive trend.

Syndecan-2 promotes perineural invasion and cooperates with K-ras to induce an invasive pancreatic cancer cell phenotype

Background

We have identified syndecan-2 as a protein potentially involved in perineural invasion of pancreatic adenocarcinoma (PDAC) cells.

Methods

Syndecan-2 (SDC-2) expression was analyzed in human normal pancreas, chronic pancreatitis and PDAC tissues. Functional in vitro assays were carried out to determine its role in invasion, migration and signaling.

Results

SDC-2 was expressed in the majority of the tested pancreatic cancer cell lines while it was upregulated in nerve-invasive PDAC cell clones. There were 2 distinct expression patterns of SDC-2 in PDAC tissue samples: SDC-2 positivity in the cancer cell cytoplasm and a peritumoral expression. Though SDC-2 silencing (using specific siRNA oligonucleotides) did not affect anchorage-dependent growth, it significantly reduced cell motility and invasiveness in the pancreatic cancer cell lines T3M4 and Su8686. On the transcriptional level, migration-and invasion-associated genes were down-regulated following SDC-2 RNAi. Furthermore, SDC-2 silencing reduced K-ras activity, phosphorylation of Src and - further downstream - phosphorylation of ERK2 while levels of the putative SDC-2 signal transducer p120GAP remained unaltered.

Conclusion

SDC-2 is a novel (perineural) invasion-associated gene in PDAC which cooperates with K-ras to induce a more invasive phenotype.

MHC class II expression in pancreatic tumors: a link to intratumoral inflammation

Major histocompatibility complex class II antigens (MHC class II) are constitutively expressed by professional antigen presenting cells and present antigenic peptides to specific CD4+ T lymphocytes. MHC class II expression, however, can also be induced on epithelial cells and in a variety of solid tumors. We tested MHC class II expression on tissue samples derived from patients with pancreatic ductal adenocarcinoma (PDAC) and pancreatic endocrine tumors (PET). Immunohistochemistry revealed MHC class II expression in 86 of 112 (76.8%) PDAC samples and in 30 of 43 (70.0%) PET samples. In PDAC and PET, MHC class II expression correlated significantly with severity and activity of intratumoral inflammation, as well as with the infiltration of CD4+ T lymphocytes. High MHC class II expression significantly correlated with a better histological grade of differentiation in PDAC. In vitro MHC class II expression could be induced on PDAC tumor cell lines by interferon-γ. These cells were then able to present the staphylococci enterotoxin B superantigen to T lymphocytes, which resulted in T cell proliferation. Our findings suggest that MHC class II expression on pancreatic tumor cells is induced by the intratumoral inflammatory reaction in pancreatic tumors.

Distribution and clinical significance of Th17 cells in the tumor microenvironment and peripheral blood of pancreatic cancer patients

This study was designed to investigate the distribution of Th17 cells in the tumor microenvironment and peripheral blood of pancreatic cancer patients, its clinical significance, and the expression profile of Th17 cell-associated cytokines. The percentage of Th17 cells detected by flow cytometry analysis (FACS) was significantly higher in 46 pancreatic tumor tissues (5.28 ± 1.65%) compared with corresponding adjacent normal tissues (2.57 ± 0.83%) (P = 0.031). In addition, the percentage of Th17 cells was significantly higher in stage III-IV tumors than stage I-II tumors (P = 0.039). The percentage of Th17 cells in peripheral blood of 20 pancreatic cancer patients (3.99 ± 1.15%) was significantly higher than 15 healthy volunteers (1.98 ± 0.57%) (P = 0.027). Immunohistochemistry (IHC) was performed to detect IL-17⁺ cells in 46 pancreatic tumor tissues, as well as expression of CD34 in 24 tumor tissues. IL-17 was shown to mainly locate in cytoplasm, and the frequency of IL-17⁺ cells in tumor tissues (39/46) was higher than control (29/46). The presence of IL-17⁺ cells in tumor tissues was associated with tumor, node, and metastasis (TNM) stage, and lymph node metastasis (P = 0.012 and P = 0.009) but not with patient sex, age, tumor size, and histological grade (P > 0.05). Interestingly, distribution of Th17 cells in tumor tissues was positively correlated with microvessel density (MVD) (r = 0.86, P = 0.018). Furthermore, the median survival time of patients with high and low level of IL-17⁺ cells frequency was 14.5 and 18.5 months respectively (P = 0.023). The serum levels of Th17 cell-associated cytokines, IL-17 and IL-23 in 20 pancreatic patients detected by enzyme-linked immunosorbent assay (ELISA) were 69.2 ± 28.5 pg/mL and 266.5 ± 98.1 pg/mL, respectively, which were significantly higher than 15 healthy volunteers (P = 0.015 and P = 0.02). Moreover, levels of IL-17 and IL-23 were significantly higher in stage III-IV tumors than stage I-II tumors (P = 0.04 and P = 0.036). This study suggests that increase in Th17 cells frequency and its related cytokines levels in pancreatic tumor tissues may indicate involvement in the invasion and metastasis of pancreatic cancer, which may thereby affect patient prognosis. Therefore, Th17 cells and related cytokines may be served as important immune indicators for predicting the prognosis of pancreatic cancer patients.

Randomized controlled phase I/II study to investigate immune stimulatory effects by low dose radiotherapy in primarily operable pancreatic cancer

Background

The efficiencies of T cell based immunotherapies are affected by insufficient migration and activation of tumor specific effector T cells in the tumor. Accumulating evidence exists on the ability of ionizing radiation to modify the tumor microenvironment and generate inflammation. The aim of this phase I/II clinical trial is to evaluate whether low dose single fraction radiotherapy can improve T cell associated antitumor immune response in patients with pancreatic cancer.

Methods/Design

This trial has been designed as an investigator initiated; prospective randomised, 4-armed, controlled Phase I/II trial. Patients who are candidates for resection of pancreatic cancer will be randomized into 4 arms. A total of 40 patients will be enrolled. The patients receive 0 Gy, 0.5 Gy, 2 Gy or 5 Gy radiation precisely targeted to their pancreatic carcinoma. Radiation will be delivered by external beam radiotherapy using a 6 MV Linac with IMRT technique 48 h prior to the surgical resection. The primary objective is the determination of an active local external beam radiation dose, leading to tumor infiltrating T cells as a surrogate parameter for antitumor activity. Secondary objectives include local tumor control and recurrence patterns, survival, radiogenic treatment toxicity and postoperative morbidity and mortality, as well as quality of life. Further, frequencies of tumor reactive T cells in blood and bone marrow as well as whole blood cell transcriptomics and plasma-proteomics will be correlated with clinical outcome. An interim analysis will be performed after the enrolment of 20 patients for safety reasons. The evaluation of the primary endpoint will start four weeks after the last patient's enrolment.

Discussion

This trial will answer the question whether a low dose radiotherapy localized to the pancreatic tumor only can increase the number of tumor infiltrating T cells and thus potentially enhance the antitumor immune response. The study will also investigate the prognostic and predictive value of radiation-induced T cell activity along with transcriptomic and proteomic data with respect to clinical outcome.

Trial registration

ClinicalTrials.gov - NCT01027221

Intratumor T helper type 2 cell infiltrate correlates with cancer-associated fibroblast thymic stromal lymphopoietin production and reduced survival in pancreatic cancer

Expression of TSLP in pancreatic cancer correlates with Th2 deviation of antitumor immunity that is associated with decrease of patient survival.

Pancreatic cancer is a very aggressive disease characterized by a marked desmoplasia with a predominant Th2 (GATA-3⁺) over Th1 (T-bet⁺) lymphoid infiltrate. We found that the ratio of GATA-3⁺/T-bet⁺ tumor-infiltrating lymphoid cells is an independent predictive marker of patient survival. Patients surgically treated for stage IB/III disease with a ratio inferior to the median value had a statistically significant prolonged overall survival, implying an active role for Th2 responses in disease progression. Thymic stromal lymphopoietin (TSLP), which favors Th2 cell polarization through myeloid dendritic cell (DC) conditioning, was secreted by cancer-associated fibroblasts (CAFs) after activation with tumor-derived tumor necrosis factor α and interleukin 1β. TSLP-containing supernatants from activated CAFs induced in vitro myeloid DCs to up-regulate the TSLP receptor (TSLPR), secrete Th2-attracting chemokines, and acquire TSLP-dependent Th2-polarizing capability in vitro. In vivo, Th2 chemoattractants were expressed in the tumor and in the stroma, and TSLPR-expressing DCs were present in the tumor stroma and in tumor-draining but not in nondraining lymph nodes. Collectively, this study identifies in pancreatic cancer a cross talk between tumor cells and CAFs, resulting in a TSLP-dependent induction of Th2-type inflammation which associates with reduced patient survival. Thus, blocking TSLP production by CAFs might help to improve prognosis in pancreatic cancer.

Enhancement of NK cell antitumor responses using an oncolytic parvovirus

Natural killer (NK) cells play a vital role in the rejection of tumors. Pancreatic ductal adenocarcinoma (PDAC), however, remains a poor prognosis malignancy, due to its resistance to radio- and chemotherapy, and low immunogenicity. We demonstrate here that IL-2-activated human NK cells are able to kill PDAC cells. Currently, novel strategies are being pursued to combat PDAC. In this regard, oncolytic viruses, in addition to killing tumor cells, may also have the potential to augment antitumor immune responses. We found that, besides having an intrinsic oncolytic activity, parvovirus H-1PV is able to enhance NK cell-mediated killing of PDAC cells. Our results show that H-1PV infection of Panc-1 cells increases NK cell capacity to release IFN-γ, TNF-α and MIP-1α/β. Multiple activating receptors are involved in the NK cell-mediated killing of Panc-1 cells. Indeed, blocking of the natural cytotoxicity receptors-NKp30, 44 and 46 in combination, and NKG2D and DNAM1 alone inhibit the killing of Panc-1 cells. Interestingly, H-1PV infection of Panc-1 cells overcomes the part of inhibitory effects suggesting that parvovirus may induce additional NK cell ligands on Panc-1 cells. The enhanced sensitivity of H-1PV-infected PDAC cells to NK cell-dependent killing could be traced back to the upregulation of the DNAM-1 ligand, CD155 and to the downregulation of MHC class I expression. Our data suggests that NK cells display antitumor potential against PDAC and that H-1PV-based oncolytic immunotherapy could further boost NK cell-mediated immune responses and help to develop a combinatorial therapeutic approach against PDAC.

RNA interference in the clinic: challenges and future directions

Inherent difficulties with blocking many desirable targets using conventional approaches have prompted many to consider using RNA interference (RNAi) as a therapeutic approach. Although exploitation of RNAi has immense potential as a cancer therapeutic, many physiological obstacles stand in the way of successful and efficient delivery. This Review explores current challenges to the development of synthetic RNAi-based therapies and considers new approaches to circumvent biological barriers, to avoid intolerable side effects and to achieve controlled and sustained release.

Pilot study to relate clinical outcome in pancreatic carcinoma and angiogenic plasma factors/circulating mature/progenitor endothelial cells: Preliminary results

Circulating endothelial cells (CEC) and bone marrow-derived endothelial progenitors (ECP) play important roles in tumor growth and have been proposed as non-invasive markers of angiogenesis. However, CEC and ECP levels have not been investigated in pancreatic carcinoma patients. Using four-color flow cytometry procedures, we evaluated the count of resting (rCEC) and activated (aCEC) endothelial cells and ECP in the peripheral blood of pancreatic carcinoma patients before and after chemotherapy, consisting of gemcitabine (GEM) alone or in combination with oxaliplatin (OX), or with 5-fluorouracil (5-FU). We also correlated CEC and ECP levels with plasma levels of relevant angiogenic factors, such as vascular endothelial growth factor (VEGF)-A, VEGF-D, angiopoietin (Angio)-1, and chemokine C-X-C motif ligand (CXCL)12, measured by ELISA, and with clinical features of pancreatic cancer. The aCEC, rCEC, ECP, and VEGF-A plasma levels were significantly higher in locally-advanced and metastatic patients than controls. Both ECP and VEGF-A levels correlated positively with disease stage and inversely with patient's overall survival. Measurements after the treatment course showed that VEGF-A plasma concentrations and ECP counts had decreased significantly. In particular, VEGF-A and rCEC were significantly down after treatment with GEM alone or in combination with OX. No significant differences in terms of circulating angiogenic factor or endothelial cell subtype levels were found between responders (patients entering partial remission or with stable disease) and non-responders (patients with progressive disease). The study provides insights into angiogenesis mechanisms in pancreatic carcinoma, for which anti-angiogenic targeting of VEGF-A and ECP could be of interest.

Allosteric inhibition of lysyl oxidase-like-2 impedes the development of a pathologic microenvironment

We have identified a new role for the matrix enzyme lysyl oxidase-like-2 (LOXL2) in the creation and maintenance of the pathologic microenvironment of cancer and fibrotic disease. Our analysis of biopsies from human tumors and fibrotic lung and liver tissues revealed an increase in LOXL2 in disease-associated stroma and limited expression in healthy tissues. Targeting LOXL2 with an inhibitory monoclonal antibody (AB0023) was efficacious in both primary and metastatic xenograft models of cancer, as well as in liver and lung fibrosis models. Inhibition of LOXL2 resulted in a marked reduction in activated fibroblasts, desmoplasia and endothelial cells, decreased production of growth factors and cytokines and decreased transforming growth factor-beta (TGF-beta) pathway signaling. AB0023 outperformed the small-molecule lysyl oxidase inhibitor beta-aminoproprionitrile. The efficacy and safety of LOXL2-specific AB0023 represents a new therapeutic approach with broad applicability in oncologic and fibrotic diseases.

New advances on critical implications of tumor- and metastasis-initiating cells in cancer progression, treatment resistance and disease recurrence

Accumulating lines of experimental evidence have revealed that the malignant transformation of multipotent tissue-resident adult stem/progenitor cells into cancer stem/progenitor cells endowed with a high self-renewal capacity and aberrant multilineage differentiation potential may be at origin of the most types of human aggressive and recurrent cancers. Based on new cancer stem/progenitor cell concepts of carcinogenesis, it is suggested that a small subpopulation of highly tumorigenic and migrating cancer stem/progenitor cells, also designated as cancer- and metastasis-initiating cells, can provide critical roles for primary tumor growth, metastases at distant tissues and organs, treatment resistance and disease relapse. Particularly, cancer initiation and progression to locally invasive and metastatic stages is often associated with a persistent activation of distinct developmental signaling pathways in these immature cells during epithelial-mesenchymal transition program. The signaling cascades that are often deregulated in cancer stem/progenitor cells include hedgehog, epidermal growth factor receptor (EGFR), Wnt/beta-catenin, NOTCH, polycomb gene product BMI-1 and/or stromal cell-derived factor-1 (SDF-1)/CXC chemokine receptor 4 (CXCR4). Importantly, the results from recent investigations have also indicated that different cancer subtypes may harbor distinct subsets and/or number of cancer-initiating cells during cancer progression as well as before or after therapy initiation and disease recurrence. Therefore, the identification of the molecular transforming events that frequently occur in cancer- and metastasis-initiating cells versus their differentiated progenies is of immense interest to develop new targeting approach for improving current therapies against aggressive, metastatic, recurrent and lethal cancers.

Tumor initiating cells in pancreatic cancer: A critical view

Emerging evidence points to the existence of pancreatic cancer stem cells (CSC) as the culprit in the initiation, maintenance, metastasis, and treatment resistance of pancreatic cancer. The existence of such a cell population would have an important impact on the design of novel therapies against this devastating disease. However, no in vivo validation or rebuttal of the pancreatic CSC hypothesis exists. Major backlashes in the discussion on CSC are firstly, the confusion between the terms CSC and cell of origin of pancreatic ductal adenocarcinoma (PDAC), secondly the ambiguity of the cell of origin itself and thirdly, the fact that the CSC hypothesis is based on cell sorting and xenografting experiments; the latter of which often precludes solid conclusions because of the lack of a natural microenvironment and differences in drug delivery. Nonetheless, recent studies in other cancers partially support the CSC hypothesis by demonstrating a link between epithelial-to-mesenchymal transdifferentiation/transition (EMT) and CSC properties. Such a link is again open to dispute as EMT is a reversible process which is highly dependent on major oncogenic pathways in PDAC [e.g. K-Ras, transforming growth factor-β (TGF-β)] rather than on presumed cancer stem cell pathways. Hence, the available evidence does not robustly support the CSC concept in PDAC and a thorough validation of this hypothesis in well-defined genetically engineered mouse models of pancreatic cancer is required.

Desmoplasia of pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is the most common form of pancreatic cancer and is characterized by remarkable desmoplasia. The desmoplasia is composed of extracellular matrix (ECM) proteins, myofibroblastic pancreatic stellate cells, and immune cells associated with a multitude of cytokines, growth factors, and ECM metabolizing enzymes. The mechanisms of participation of this complex matrix process in carcinogenesis are only starting to be appreciated. Recent studies showed key roles for stellate cells in the production of ECM proteins as well as cytokines and growth factors that promote the growth of the cancer cells all present in the desmoplastic parts of PDAC. In addition, interactions of ECM proteins and desmoplastic secreted growth factors with the cancer cells of PDAC activate intracellular signals including reactive oxygen species that act to make the cancer cells resistant to dying. These findings suggest that the desmoplasia of PDAC is a key factor in regulating carcinogenesis of PDAC as well as responses to therapies. A better understanding of the biology of desmoplasia in the mechanism of PDAC will likely provide significant opportunities for better treatments for this devastating cancer.

Non-redundant role for IL-12 and IL-27 in modulating Th2 polarization of carcinoembryonic antigen specific CD4 T cells from pancreatic cancer patients

Background

Pancreatic cancer is a very aggressive disease with dismal prognosis; peculiar is the tumor microenvironment characterized by an extensive fibrotic stroma, which favors rapid tumor progression. We previously reported that pancreatic cancer patients have a selective Th2 skew in the anti-carcinoembryonic antigen (CEA) CD4⁺ T cell immunity, which correlates with the presence of a predominant GATA-3⁺ tumor lymphoid infiltrate. This has negative effects in both effective anti-tumor immunity and further favoring fibrinogenesis. Aim of this study was to evaluate whether the Th2 polarization of CEA-specific CD4⁺ T cells from pancreatic cancer patients is stable or can be reverted by immunomodulating cytokines.

Methodology/Principal Findings

We first evaluated the influence of IL-12 and IL-27, as single agents and in association, on the polarization of CEA-specific Th2 CD4⁺ T cell clones from a pancreatic cancer patient. We found that only the combination of IL-12 and IL-27 modified the polarization of Th2 effectors by both reduction of IL-5, GM-CSF and IL-13 and induction of IFN-γ production, which lasted after cytokine removal. Second, we evaluated the effect of the combined treatment on polyclonal CEA-specific CD4⁺ T cells in short-time re-stimulation assays. In agreement with the data obtained with the clones, we found that the combined treatment functionally modulated the Th2 polarization of CEA-specific CD4⁺ T cells and enhanced pre-existing Th1 type immunity.

Conclusions/Significance

Collectively, our results demonstrate that tumor antigen specific Th2 CD4⁺ T cells in pancreatic cancer are endowed with functional plasticity. Hence, loco-regional cytokines delivery or targeted therapy based on antibodies or molecules directed to the tumor stroma might improve anti-tumor immunity and ameliorate fibrosis, without systemic toxicity.

Bone marrow-derived progenitor cells could modulate pancreatic cancer tumorigenesis via peritumoral microenvironment in a rat model

Metaplastic tubular complexes (MTC) have been proposed as precursor lesions for pancreatic adenocarcinoma (PDAC). In this study, we investigated the potential role of bone marrow-derived progenitor cells (BMPC) in the formation of MTC and PDAC in a rat model. F344 rats defective for CD26 (dipeptidyl peptidase IV, DPPIV) expression were sublethally irradiated and received rescue bone marrow cells from wild-type F344 rats that express CD26. After confirming engraftment, recipient animals received dimethylbenzanthracene (DMBA) implantation in their pancreas. Animals were sacrificed monthly from 3 to 7 months. We observed both MTC and tumors in animals that received DMBA. These MTC were ductal complexes because they stained positive for cytokeratin but were negative for chymotrypsin and chromogranin A. Cells that expressed both CD26 and cytokeratin were rarely observed in the MTC. Cells expressing either both CD26 and CD45 or CD26 and smooth muscle actin were also found near the MTC. However, no CD26 signal was detected in the tumors. Within this model, there appeared to be no evidence supporting that BMPC turned into tumor cells directly. BMPC could modulate pancreatic cancer growth through tumor microenvironment.

Consensus transcriptome signature of perineural invasion in pancreatic carcinoma

Perineural invasion, the growth of tumor cells along nerves, is a key feature of pancreatic cancer. The cardinal symptom of pancreatic cancer, abdominal pain often radiating to the back, as well as the high frequency of local tumor recurrence following resection are both attributed to the unique ability of pancreatic tumor cells to invade the neuronal system. The molecular mechanisms underlying the neuroaffinity of pancreatic tumors are not completely understood. In this study, we developed a novel method to monitor ex vivo perineural invasion into surgically resected rat vagal nerves by different human pancreatic tumor cell lines. Genome-wide transcriptional analyses were employed to identify the consensus set of genes differentially regulated in all highly nerve-invasive (nerve invasion passage 3) versus less invasive (nerve invasion passage 0) pancreatic tumor cells. The critical involvement of kinesin family member 14 (KIF14) and Rho-GDP dissociation inhibitor beta (ARHGDIbeta) in perineural invasion was confirmed on RNA and protein levels in human pancreatic tumor specimens. We found significant up-regulation of KIF14 and ARHGDIbeta mRNA levels in patients with pancreatic cancer, and both proteins were differentially expressed in tumor cells invading the perineural niche of pancreatic cancer patients as detected by immunohistochemistry. Moreover, functional knockdown of KIF14 and ARHGDIbeta using small interfering RNA resulted in altered basal and/or perineural invasion of pancreatic tumor cells. Our work provides novel insights into the molecular determinants of perineural invasion in pancreatic cancer. The established nerve invasion model and the consensus signature of perineural invasion could be instrumental in the identification of novel therapeutic targets of pancreatic cancer as exemplified by KIF14 and ARHGDIbeta.

In vitro models of pancreatic cancer for translational oncology research

BACKGROUND: Pancreatic cancer is a disease of near uniform fatality and the overwhelming majority of patients succumb to their advanced malignancy within a few months of diagnosis. Despite considerable advances in our understanding of molecular mechanisms underlying pancreatic carcinogenesis, this knowledge has not yet been fully translated into clinically available treatment strategies that yield significant improvements in disease free or overall survival. OBJECTIVE: Cell line-based in vitro model systems provide powerful tools to identify potential molecular targets for therapeutic intervention as well as for initial pre-clinical evaluation of novel drug candidates. Here we provide a brief overview of recent literature on cell line-based model systems of pancreatic cancer and their application in the search for novel therapeutics against this vicious disease. CONCLUSION: While in vitro models of pancreatic cancer are of tremendous value for genetic studies and initial functional screenings in drug discovery, they carry several imanent drawbacks and are often poor in predicting therapeutic response in humans. Therefore, in most instances they are successfully exploited to generate hypothesis and identify molecular targets for novel therapeutics, which are subsequently subject to further in-depth characterization using more advanced in vivo model systems and clinical trials.

Carcinoembryonic antigen-specific but not antiviral CD4+ T cell immunity is impaired in pancreatic carcinoma patients

Pancreatic carcinoma is a very aggressive disease with dismal prognosis. Although evidences for tumor-specific T cell immunity exist, factors related to tumor microenvironment and the presence of immunosuppressive cytokines in patients' sera have been related to its aggressive behavior. Carcinoembryonic Ag (CEA) is overexpressed in 80-90% of pancreatic carcinomas and contains epitopes recognized by CD4(+) T cells. The aim of this study was to evaluate the extent of cancer-immune surveillance and immune suppression in pancreatic carcinoma patients by comparing the anti-CEA and antiviral CD4(+) T cell immunity. CD4(+) T cells from 23 normal donors and 44 patients undergoing surgical resection were tested for recognition of peptides corresponding to CEA and viral naturally processed promiscuous epitopes by proliferation and cytokine release assays. Anti-CEA CD4(+) T cell immunity was present in a significantly higher number of normal donors than pancreatic cancer patients. Importantly, whereas CD4(+) T cells from normal donors produced mainly GM-CSF and IFN-gamma, CD4(+) T cells from the patients produced mainly IL-5, demonstrating a skew toward a Th2 type. On the contrary, the extent of antiviral CD4(+) T cell immunity was comparable between the two groups and showed a Th1 type. The immunohistochemical analysis of tumor-infiltrating lymphocytes showed a significantly higher number of GATA-3(+) compared with T-bet(+) lymphoid cells, supporting a Th2 skew also at the tumor site. Collectively, these results demonstrate that Th2-immune deviation in pancreatic cancer is not generalized but tumor related and suggests that the skew might be possibly due to factor(s) present at the tumor site.

Bone marrow-derived progenitor cells could modulate pancreatic cancer tumorigenesis via peritumoral microenvironment in a rat model

Metaplastic tubular complexes (MTC) have been proposed as precursor lesions for pancreatic adenocarcinoma (PDAC). In this study, we investigated the potential role of bone marrow-derived progenitor cells (BMPC) in the formation of MTC and PDAC in a rat model. F344 rats defective for CD26 (dipeptidyl peptidase IV, DPPIV) expression were sublethally irradiated and received rescue bone marrow cells from wild-type F344 rats that express CD26. After confirming engraftment, recipient animals received dimethylbenzanthracene (DMBA) implantation in their pancreas. Animals were sacrificed monthly from 3 to 7 months. We observed both MTC and tumors in animals that received DMBA. These MTC were ductal complexes because they stained positive for cytokeratin but were negative for chymotrypsin and chromogranin A. Cells that expressed both CD26 and cytokeratin were rarely observed in the MTC. Cells expressing either both CD26 and CD45 or CD26 and smooth muscle actin were also found near the MTC. However, no CD26 signal was detected in the tumors. Within this model, there appeared to be no evidence supporting that BMPC turned into tumor cells directly. BMPC could modulate pancreatic cancer growth through tumor microenvironment.