Primary Human Pancreatic Tumors Research Articles

Sustained degradation of hyaluronic acid using an in situ forming implant.

In pancreatic cancer, excessive hyaluronic acid (HA) in the tumor microenvironment creates a viscous stroma, which reduces systemic drug transport into the tumor and correlates with poor patient prognosis. HA can be degraded through both enzymatic and nonenzymatic methods to improve mass transport properties. Here, we use an in situ forming implant to provide sustained degradation of HA directly at a local, targeted site. We formulated and characterized an implant capable of sustained release of hyaluronidase (HAase) using 15kDa poly(lactic-co-glycolic) acid and bovine testicular HAase. The implant releases bioactive HAase to degrade the HA through enzymatic hydrolysis at early timepoints. In the first 24 h, 17.9% of the HAase is released, which can reduce the viscosity of a 10mg/mL HA solution by 94.1% and deplete the HA content within primary human pancreatic tumor samples and ex vivo murine tumors. At later timepoints, as lower quantities of HAase are released (51.4% released in total over 21 d), the degradation of HA is supplemented by the acidic by-products that accumulate as a result of implant degradation. Acidic conditions degrade HA through nonenzymatic methods. This formulation has potential as an intratumoral injection to allow sustained degradation of HA at the pancreatic tumor site.

Patient Derived Xenografts Expand Human Primary Pancreatic Tumor Tissue Availability for ex vivo Irreversible Electroporation Testing

New methods of tumor ablation have shown exciting efficacy in pre-clinical models but often demonstrate limited success in the clinic. Due to a lack of quality or quantity in primary malignant tissue specimens, therapeutic development and optimization studies are typically conducted on healthy tissue or cell-line derived rodent tumors that don't allow for high resolution modeling of mechanical, chemical, and biological properties. These surrogates do not accurately recapitulate many critical components of the tumor microenvironment that can impact in situ treatment success. Here, we propose utilizing patient-derived xenograft (PDX) models to propagate clinically relevant tumor specimens for the optimization and development of novel tumor ablation modalities. Specimens from three individual pancreatic ductal adenocarcinoma (PDAC) patients were utilized to generate PDX models. This process generated 15–18 tumors that were allowed to expand to 1.5 cm in diameter over the course of 50–70 days. The PDX tumors were morphologically and pathologically identical to primary tumor tissue. Likewise, the PDX tumors were also found to be physiologically superior to other in vitro and ex vivo models based on immortalized cell lines. We utilized the PDX tumors to refine and optimize irreversible electroporation (IRE) treatment parameters. IRE, a novel, non-thermal tumor ablation modality, is being evaluated in a diverse range of cancer clinical trials including pancreatic cancer. The PDX tumors were compared against either Pan02 mouse derived tumors or resected tissue from human PDAC patients. The PDX tumors demonstrated similar changes in electrical conductivity and Joule heating following IRE treatment. Computational modeling revealed a high similarity in the predicted ablation size of the PDX tumors that closely correlate with the data generated with the primary human pancreatic tumor tissue. Gene expression analysis revealed that IRE treatment resulted in an increase in biological pathway signaling associated with interferon gamma signaling, necrosis and mitochondria dysfunction, suggesting potential co-therapy targets. Together, these findings highlight the utility of the PDX system in tumor ablation modeling for IRE and increasing clinical application efficacy. It is also feasible that the use of PDX models will significantly benefit other ablation modality testing beyond IRE.

Phosphorylation at Ser-181 of Oncogenic KRAS Is Required for Tumor Growth

KRAS phosphorylation has been reported recently to modulate the activity of mutant KRAS protein in vitro. In this study, we defined S181 as a specific phosphorylation site required to license the oncogenic function of mutant KRAS in vivo. The phosphomutant S181A failed to induce tumors in mice, whereas the phosphomimetic mutant S181D exhibited an enhanced tumor formation capacity, compared with the wild-type KRAS protein. Reduced growth of tumors composed of cells expressing the nonphosphorylatable KRAS S181A mutant was correlated with increased apoptosis. Conversely, increased growth of tumors composed of cells expressing the phosphomimetic KRAS S181D mutant was correlated with increased activation of AKT and ERK, two major downstream effectors of KRAS. Pharmacologic treatment with PKC inhibitors impaired tumor growth associated with reduced levels of phosphorylated KRAS and reduced effector activation. In a panel of human tumor cell lines expressing various KRAS isoforms, we showed that KRAS phosphorylation was essential for survival and tumorigenic activity. Furthermore, we identified phosphorylated KRAS in a panel of primary human pancreatic tumors. Taken together, our findings establish that KRAS requires S181 phosphorylation to manifest its oncogenic properties, implying that its inhibition represents a relevant target to attack KRAS-driven tumors.

Micropallet arrays for the capture, isolation and culture of circulating tumor cells from whole blood of mice engrafted with primary human pancreatic adenocarcinoma

Circulating tumor cells (CTCs) are important biomarkers of cancer progression and metastatic potential. The rarity of CTCs in peripheral blood has driven the development of technologies to isolate these tumor cells with high specificity; however, there are limited techniques available for isolating target CTCs following enumeration. A strategy is described to capture and isolate viable tumor cells from whole blood using an array of releasable microstructures termed micropallets. Specific capture of nucleated cells or cells expressing epithelial cell adhesion molecules (EpCAM) was achieved by functionalizing micropallet surfaces with either fibronectin, Matrigel or anti-EpCAM antibody. Surface grafting of poly(acrylic acid) followed by covalent binding of protein A/G enabled efficient capture of EpCAM antibody on the micropallet surface. MCF-7 cells, a human breast adenocarcinoma, were retained on the array surface with 90±8% efficiency when using an anti-EpCAM-coated array. To demonstrate the efficiency of tumor cell retention on micropallet arrays in the presence of blood, MCF-7 cells were mixed into whole blood and added to small arrays (71mm2) coated with fibronectin, Matrigel or anti-EpCAM. These approaches achieved MCF-7 cell capture from ≤10µL of whole blood with efficiencies greater than 85%. Furthermore, MCF-7 cells intermixed with 1mL blood and loaded onto large arrays (7171mm2) were captured with high efficiencies (≥97%), could be isolated from the array by a laser-based approach and were demonstrated to yield a high rate of colony formation (≥85%) after removal from the array. Clinical utility of this technology was shown through the capture, isolation and successful culture of CTCs from the blood of mice engrafted with primary human pancreatic tumors. Direct capture and isolation of living tumor cells from blood followed by analysis or culture will be a valuable tool for cancer cell characterization.

Protein Kinase C Zeta Regulates Human Pancreatic Cancer Cell Transformed Growth and Invasion through a STAT3-Dependent Mechanism

Pancreatic cancer is a very aggressive disease with few therapeutic options. In this study, we investigate the role of protein kinase C zeta (PKCζ) in pancreatic cancer cells. PKCζ has been shown to act as either a tumor suppressor or tumor promoter depending upon the cellular context. We find that PKCζ expression is either maintained or elevated in primary human pancreatic tumors, but is never lost, consistent with PKCζ playing a promotive role in the pancreatic cancer phenotype. Genetic inhibition of PKCζ reduced adherent growth, cell survival and anchorage-independent growth of human pancreatic cancer cells in vitro. Furthermore, PKCζ inhibition reduced orthotopic tumor size in vivo by inhibiting tumor cell proliferation and increasing tumor necrosis. In addition, PKCζ inhibition reduced tumor metastases in vivo, and caused a corresponding reduction in pancreatic cancer cell invasion in vitro. Signal transducer and activator of transcription 3 (STAT3) is often constitutively active in pancreatic cancer, and plays an important role in pancreatic cancer cell survival and metastasis. Interestingly, inhibition of PKCζ significantly reduced constitutive STAT3 activation in pancreatic cancer cells in vitro and in vivo. Pharmacologic inhibition of STAT3 mimicked the phenotype of PKCζ inhibition, and expression of a constitutively active STAT3 construct rescued the transformed phenotype in PKCζ-deficient cells. We conclude that PKCζ is required for pancreatic cancer cell transformed growth and invasion in vitro and tumorigenesis in vivo, and that STAT3 is an important downstream mediator of the pro-carcinogenic effects of PKCζ in pancreatic cancer cells.

Metastatic Cancer Stem Cells—Quo Vadis?

Featured Article: Hermann PC, Huber SL, Herrler T, Aicher A, Ellwart JW, Guba M, et al. Distinct populations of cancer stem cells determine tumor growth and metastatic activity in human pancreatic cancer. Cell Stem Cell 2007;1:313–23.2 In 2003, Al-Hajj and colleagues demonstrated the existence and biological relevance of cancer stem cells (CSCs)3 in breast cancer, and thus for the first time in solid tumors (1). Then in 2007, our team (featured article) and a team from the US (2) independently reported the existence and functional features of CSCs in primary human pancreatic tumors. Interestingly, we not only demonstrated the existence of a CD133+ CSC population and its exclusive tumorigenicity but also described for the first time the inherent resistance of these cells to chemotherapy in pancreatic cancer. Most interesting, however, was our discovery that CD133+ CSCs were by no means a homogeneous population with respect to their functional properties. On the basis of the observation …

Pim-3 promotes the growth of human pancreatic cancer in the orthotopic nude mouse model through vascular endothelium growth factor

BackgroundAs one of the most lethal cancers, pancreatic cancer presents poor prognosis with an overall 5-y survival of less than 5%. We previously reported that Pim-3, a member of the proto-oncogene Pim family that encodes serine/threonine kinases, is aberrantly expressed in human pancreatic cancer lesions. In the current study, we investigated the role of Pim-3 in promoting tumor growth and angiogenesis in an orthotopic nude mouse model of human pancreatic cancer. MethodsWe constructed retroviral vectors for human Pim-3 and a kinase-dead mutant of human Pim-3 (K69M); the retroviral supernatants generated from these vectors were then used to infect the human pancreatic cancer cell line MiaPaCa-2 to establish stable cell lines. We assessed cell proliferation using CCK-8, tumor growth, and angiogenesis in vivo in an orthotopic mouse model of pancreatic cancer. While tumor size was measured using magnetic resonance imaging, the tumor tissues were excised for protein extraction and histological analysis to detect vascular endothelium growth factor (VEGF) expression and vessel density. ResultsWe established an orthotopic nude mouse model of human pancreatic cancer. We observed that Pim-3 promoted the proliferation of human pancreatic cancer cells, both in vitro and in vivo. Moreover, Pim-3 is required for vasculogenesis of primary human pancreatic tumors in vivo and promotion of angiogenesis through the induction of VEGF expression. ConclusionsPim-3 can promote tumor growth and angiogenesis by stimulating the VEGF pathway.

Abstract 2454: Pancreatic cancer stem cells (CSCs) express MUC1 and MUC1-expressing pancreatic cancers encompass higher levels of CSCs

Abstract Introduction: Pancreatic ductal adenocarcinoma (PDA) has the worst prognosis of all cancers and is the fourth leading cause of cancer-related deaths in the United States. Cancer stem cells (CSCs), which are a small population of tumor cells that have the ability to self-renew and differentiate into the diverse cells that comprise the tumor, have been identified in pancreatic cancer patients as lineage-negative, CD133 (prominin-1)-expressing cells. In pancreatic cancer, MUC1 is a protein expressed with a high frequency and its expression correlates with high metastasis and poor prognosis. Recent reports from our lab have demonstrated the ability of MUC1 to drive epithelial-to-mesenchymal transition thus producing a cell with ‘stem-like’ properties. We therefore investigated the correlation between MUC1 expression and CSCs. Methods: Primary tumor tissues surgically resected from patients diagnosed with pancreatic adenocarcinoma (n=8) and human pancreatic cancer cell lines were assessed for CD133 and MUC1 expression by flow cytometry. Results: In pancreatic cancer patients, tumor MUC1 levels correlated with a higher percentage of CD133-expressing cells (R=0.76). Similarly, in MiaPaCa2, Capan-1, BxPC3 WT, BxPC3 MUC1, Su86.86 WT and Su86.86 MUC1 cells lines, MUC1 levels correlated with increased CD133 expression (R=0.83). The majority of CD133+ cells isolated from primary human pancreatic tumors (82.6 ± 12.7%) expressed MUC1. Similar results were obtained using cell lines, as 83.22 ± 30.9% of CD133-expressing cells were MUC1-positive. Conclusion: MUC1 is present on the majority of CSCs and its expression correlates with higher levels of cancer stem cells. This study demonstrates yet another oncogenic role of MUC1 in pancreatic cancer progression and suggests MUC1 as a novel marker for CSCs. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2454. doi:10.1158/1538-7445.AM2011-2454

Abstract 4290: The smoothened antagonist NVP-LDE225 targets stroma and cancer stem cells in primary human pancreatic tumor xenografts

Abstract Pancreatic ductal adenocarcinoma (PDAC) is the fourth leading cause of cancer mortality. Despite surgical intervention and treatment with Gemcitabine, the standard of care, the 5-year survival rate remains less than 5%. Because the aberrant activation of the Hedgehog (Hh) pathway in stroma cells and cancer stem cells in PDAC has become evident during the last few years, therapeutic agents able to inhibit Smoothened (Smo), the positive regulator of the pathway, are under vigorous investigation. We have developed a selective Smo antagonist, NVP-LDE225, which is orally bioavailable and potently inhibits Hh signaling in vitro and in vivo. Using a combination of in vitro and in vivo assays, we evaluated the effects of NVP-LDE225 alone or in combination with Gemcitabine in primary human tumor xenograft models. In these models, NVP-LDE225 dosed together with Gemcitibine resulted in a trend towards combination activity. Tumor samples collected at the end of the studies showed that the Hh pathway was completely inhibited in the stroma of the NVP-LDE225 treated animals. Moreover, analysis of the ratio of tumor to stroma area demonstrated no differences between the drug treated as compared to vehicle treated tumors. After subcutaneous implantation of the human tumors in mice, the mouse stroma replaces the human stroma. Using mouse and human Affymetrix analysis of tumors following in vivo treatment, we were able to differentiate the changes occurring in murine stromal cells versus human epithelial cells. This analysis revealed changes in the regulation of several key developmental and growth factor pathways in the mouse stroma. To study cancer stem cells, we isolated Aldehyde Dehydrogenase (ALDH) positive cells from untreated xenograft tumors and confirmed up regulation of the Hh pathway genes, and that ALDH positive cells were more tumorigenic than ALDH negative cells when implanted in animals. Furthermore, we used 2 different stem cell functional assays, in vitro sphere formation and in vivo serial transplantation to evaluate the effect of NVP-LDE225 on cancer stem cells. We observed that upon NVP-LDE225 treatment the cells had impaired ability to form spheres in vitro and similarly, tumor growth was delayed following in vivo serial transplantation. These experiments suggest that Smo inhibitors can have a high impact on the treatment of this very aggressive cancer. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4290.

Abstract LB-257: c-Met: a new cancer stem cell marker and therapeutic target for pancreatic cancer

Abstract Pancreatic adenocarcinoma is a highly aggressive disease which is usually diagnosed in an advanced state and for which there are little/no effective therapies. The growth of many cancers depends on a subpopulation of self-renewing cells, termed cancer stem cells (CSC). We have previously identified such a CSC population in human pancreatic cancers which possess the cell surface marker phenotype CD44+CD24+ESA+. C-Met, a member of the receptor tyrosine kinases (RTKs) family and receptor for the hepatocyte growth factor (HGF) ligand, has been recently described as a marker of normal mouse pancreatic stem/progenitor cells. We hypothesized that c-Met may function as a cell surface marker and therapeutic target for human pancreatic CSCs. Studies were performed in low passage primary human pancreatic adenocarcinoma xenografts (n = 3) established in NOD-SCID mice. Self-renewal capacity of c-Methigh pancreatic cancer cells was assessed using in vitro sphere assays and in vivo tumorigenicity of c-Methigh pancreatic cancer cells was evaluated by cell implantation in NOD/SCID mice. In vitro studies demonstrated that c-Methigh cells formed spheres in non-adherent cultures, while c-Met− cells did not. Use of the c-Met inhibitor XL184 or c-Met knockdown with shRNA significantly inhibited tumor sphere formation. Pancreatic cancer cells expressing high c-Met had increased tumorigenic potential in vivo and cells expressing both CD44 and c-Methigh, representing 0.5-5% of pancreatic cancer cells, demonstrated the highest tumorigenic potential of all populations studied to date. C-Methigh CD44+ expressing pancreatic cancer cells demonstrated the capacity for self-renewal and production of differentiated progeny, properties that define CSCs. Further, c-Met inhibition of established primary human pancreatic tumors in NOD/SCID mice significantly inhibited tumor growth and depleted the pancreatic CSC population, when used alone or in combination with gemcitabine. Inhibition of c-Met also prevented the developmental of metastases using an intracardiac injection model. In this report, we define c-Met as a new marker for pancreatic CSC and define c-MethighCD44+ cells as a highly tumorigenic pancreatic CSC population. Our data also indicate that targeting c-Met may be useful in eradicating a CSC population and inhibiting the development of metastases. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr LB-257.

Characterization of a new primary human pancreatic tumor line.

A primary human pancreatic tumor line (BxPC-3) has been established from a biopsy specimen of a histologically confirmed adenocarcinoma of the body of the pancreas. Tumorigenicity was proven by xenograft in athymic nude mice. Upon re-establishment of tumor xenografts in tissue culture, the epithelial tumor cells retained their original morphology. Histopathologically, the tumors grown in nude mice exhibited the original characteristics of the primary adenocarcinoma in the patient, producing traceable mucin and displaying moderately well to poorly differentiated adenocarcinomas with occasional lymphocytic infiltrations at the tumor peripheries. Furthermore, the tumor xenografts differentially expressed carcinoembryonic antigen, human pancreas cancer-associated antigen, and human pancreas-specific antigen. Karyotyping and glucose-6-phosphate dehydrogenase isoenzyme characterization revealed that this tumor line was of human origin and devoid of HeLa cell contamination. The BxPC-3 tumor line has been maintained for more than four years in our laboratory and represents a valuable model for primary human pancreatic cancer.