Jayme B. Stokes

Inhibition of Focal Adhesion Kinase by PF-562,271 Inhibits the Growth and Metastasis of Pancreatic Cancer Concomitant with Altering the Tumor Microenvironment

Current therapies for pancreatic ductal adenocarcinoma (PDA) target individual tumor cells. Focal adhesion kinase (FAK) is activated in PDA, and levels are inversely associated with survival. We investigated the effects of PF-562,271 (a small-molecule inhibitor of FAK/PYK2) on (i) in vitro migration, invasion, and proliferation; (ii) tumor proliferation, invasion, and metastasis in a murine model; and (iii) stromal cell composition in the PDA microenvironment. Migration assays were conducted to assess tumor and stromal cell migration in response to cellular factors, collagen, and the effects of PF-562,271. An orthotopic murine model was used to assess the effects of PF-562,271 on tumor growth, invasion, and metastasis. Proliferation assays measured PF-562,271 effects on in vitro growth. Immunohistochemistry was used to examine the effects of FAK inhibition on the cellular composition of the tumor microenvironment. FAK and PYK2 were activated and expressed in patient-derived PDA tumors, stromal components, and human PDA cell lines. PF-562,271 blocked phosphorylation of FAK (phospho-FAK or Y397) in a dose-dependent manner. PF-562,271 inhibited migration of tumor cells, cancer-associated fibroblasts, and macrophages. Treatment of mice with PF-562,271 resulted in reduced tumor growth, invasion, and metastases. PF-562,271 had no effect on tumor necrosis, angiogenesis, or apoptosis, but it did decrease tumor cell proliferation and resulted in fewer tumor-associated macrophages and fibroblasts than control or gemcitabine. These data support a role for FAK in PDA and suggest that inhibitors of FAK may contribute to efficacious treatment of patients with PDA. Mol Cancer Ther; 10(11); 2135–45. ©2011 AACR.

Clinical, Molecular and Genetic Validation of a Murine Orthotopic Xenograft Model of Pancreatic Adenocarcinoma Using Fresh Human Specimens

Background Relevant preclinical models that recapitulate the key features of human pancreatic ductal adenocarcinoma (PDAC) are needed in order to provide biologically tractable models to probe disease progression and therapeutic responses and ultimately improve patient outcomes for this disease. Here, we describe the establishment and clinical, pathological, molecular and genetic validation of a murine, orthotopic xenograft model of PDAC. Methods Human PDACs were resected and orthotopically implanted and propagated in immunocompromised mice. Patient survival was correlated with xenograft growth and metastatic rate in mice. Human and mouse tumor pathology were compared. Tumors were analyzed for genetic mutations, gene expression, receptor tyrosine kinase activation, and cytokine expression. Results Fifteen human PDACs were propagated orthotopically in mice. Xenograft-bearing mice developed peritoneal and liver metastases. Time to tumor growth and metastatic efficiency in mice each correlated with patient survival. Tumor architecture, nuclear grade and stromal content were similar in patient and xenografted tumors. Propagated tumors closely exhibited the genetic and molecular features known to characterize pancreatic cancer (e.g. high rate of KRAS, P53, SMAD4 mutation and EGFR activation). The correlation coefficient of gene expression between patient tumors and xenografts propagated through multiple generations was 93 to 99%. Analysis of gene expression demonstrated distinct differences between xenografts from fresh patient tumors versus commercially available PDAC cell lines. Conclusions The orthotopic xenograft model derived from fresh human PDACs closely recapitulates the clinical, pathologic, genetic and molecular aspects of human disease. This model has resulted in the identification of rational therapeutic strategies to be tested in clinical trials and will permit additional therapeutic approaches and identification of biomarkers of response to therapy.

Use of a falciform ligament pedicle flap to decrease pancreatic fistula after distal pancreatectomy.

Objectives: Postoperative pancreatic fistula (POPF) remains a significant source of morbidity after distal pancreatectomy (DP). We describe a technique for coverage of the pancreatic stump after DP using a pedicled falciform ligament flap with a low POPF rate. Methods: A retrospective review of clinical, radiographic, and pathologic variables of patients undergoing open DP between November 2005 and August 2009 was performed. After standardized DP, the pancreatic stump was closed using a pedicled falciform ligament flap. Postoperative pancreatic fistula was defined using the International Study Group classification for pancreatic fistula definition. Results: Twenty-three consecutive patients underwent open DP and splenectomy with closure of the pancreatic stump using a pedicled falciform ligament flap. Pancreatic transection and stump closure was performed in a uniform fashion in all patients. Eight patients (35%) had additional organs resected. Two patients (8.7%) developed grade C POPFs, which were successfully managed with percutaneous drain placement. No additional patients developed a POPF or abdominal abscess. The median length of stay was 5 days. There were no perioperative mortalities. Conclusions: We conclude that use of a pedicled falciform ligament flap for coverage of the pancreatic stump is associated with a low incidence of POPF. Continued investigation of this technique is warranted.

Acquired resistance to combination therapy with lapatinib and MEK 1/2 inhibitor GSK1120212 in an in vivo murine model of pancreatic cancer.

208 Background: Mutations of the oncogene KRAS and activation of cell-surface receptor tyrosine kinases are important and preserved mechanisms of tumorgenicity in pancreatic cancer. Dual inhibition of the downstream KRAS effector MEK 1/2 and tyrosine kinases EGFR and Her2 results in effective inhibition of patient-derived tumor growth in a murine orthotopic transplantation model. Because combinatorial therapies are moving rapidly into clinical trials, we sought to develop a model of acquired tumor resistance to this combination therapy. METHODS Patient-derived pancreatic tumor xenografts MAD 09-366 (KRAS mut), MAD 08-608 (KRAS mut) and MAD 08-738 (KRAS wt) were implanted orthotopically in nude mice and treated with combination lapatinib (EGFR/Her2 inhibitor) and GSK1120212 (MEK1/2 inhibitor) and tumor volume was measured by MRI. Following 4-6wks of treatment, tumors were reimplanted in second and third generation mice and retreated. Tumors were evaluated by phospho-RTK and phospho-MAPKinase array. RESULTS Acquired resistance developed in all three tumor xenografts. Treated tumors demonstrated a relative volume decrease in the original (F0) generation. All second re-implantation (F2) tumors, demonstrated relative tumor volume increases despite treatment. A comparison of pre-treatment mean tumor volumes showed a significant decrease in tumor size from the F0 to F2 generations suggesting selection for slower growing tumors. Array data demonstrated increased activation of FGFR1, VEGFR1/3, GSK-3β, p38, and Akt in resistant tumors as compared to their pre-treatment controls. These may represent mechanisms of tumor resistance and warrant further investigation. CONCLUSIONS Repeated tumor exposure in vivo to combination treatment with GSK1120212 and lapatinib was used to develop a preclinical, orthotopic murine model of acquired drug resistance in patient-derived pancreatic cancers. This model provides the opportunity to define the mechanism of resistance in an appropriate tumor microenvironment and to develop alternative strategies for treating tumors resistant to this and other emerging therapies.

Abstract 5600: Acquired resistance of pancreatic cancers to combination therapy with lapatinib plus the MEK 1/2 inhibitor GSK1120212: Using a murine orthotopic xenograft model to identify resistance pathways

Proceedings: AACR 103rd Annual Meeting 2012‐‐ Mar 31‐Apr 4, 2012; Chicago, IL Background: The high incidence of KRAS mutations in human pancreatic cancers has driven the testing of MEK1/2 inhibitors (e.g. GSK1120212) in clinical trials for pancreatic cancer. We have recently shown that human patient-derived tumors expressing activated epidermal growth factor (EGF)/HER2 receptors exhibit enhanced response to combination therapy with GSK1120212 and lapatinib, using a mouse xenograft model. A phase I clinical trial of GSK1120212 plus lapatinib is now underway. We report here the analysis of tumors that have acquired resistance to this therapy in the setting of the mouse xenograft model with the goal of identifying additional effective combination therapies and improved strategies for treatment of patients with resistant disease. Methods: Three patient-derived pancreatic cancer xenografts expressing either mutant or wild type KRAS and activated EGF/HER2 receptors were implanted orthotopically in nude mice and treated with combination lapatinib (EGFR/HER2 inhibitor) and GSK1120212 (MEK1/2 inhibitor). Tumor volume was assessed by sequential MRI. Following treatment, tumors were reimplanted in second and third generation mice and retreated to generate therapy-resistant tumors. Drug-resistant and drug-naive tumors were compared using gene expression profiling, protein kinase arrays and Western blotting analysis. Results: Acquired resistance developed in all three tumor xenografts. Gene expression profiling identified multiple genes whose expression changed in response to drug treatment. Western blot analysis of tumor lysates from resistant and naive tumors revealed examples of select resistant tumors with either sustained activation of ERK1/2 or inactivation of ERK1/2 in the presence of inhibitor. Individual resistant tumors exhibiting inactivation of ERK1/2 exhibited increased activity of alternate survival signaling pathways including increased pAkt, pp38, pJNK, and pGSK3β levels relative to drug naive control tumors. Phospho-RTK array analysis revealed increased pFGFR1 and pVEGFR1 levels in select resistant tumors suggesting a possible role for up-regulated RTK signaling in acquired resistance. Conclusions: Using an orthotopic murine model bearing patient-derived pancreatic cancer xenografts, we have developed a model of acquired resistance to lapatinib plus GSK1120212. Interrogation of comparative gene expression and phospho-protein studies revealed alterations in signaling pathways that may contribute to drug resistance. Current studies aim to exploit these pathways to 1) derive strategies for treatment of drug-resistant tumors, and 2) develop additional rational combinatorial therapies. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 5600. doi:1538-7445.AM2012-5600

Abstract 1592: Targeting proliferative signals in patient-derived pancreatic cancers propagated orthotopically in immunocompromised mice

Pancreatic ductal adenocarcinoma (PDAC) is associated with the shortest survival duration of any solid cancer. To improve treatment for this disease, better understanding of the proliferative signals that drive pancreatic cancer progression is imperative. To this end, we have established a transplantation model in which surgically resected human pancreatic cancers are propagated orthotopically in the pancreas of immunocompromised mice, permitting detailed molecular and cellular analysis. Approximately 70-85% of engrafted tumors grow and can be serially propagated in multiple generations of mice. Tumor architecture, desmoplastic character, and the metastatic properties of tumors are preserved between the original patient tumor and orthopically propagated tumors. The initial cohort of tumors reported herein was comprised of 4 early stage (Ib/IIb) and 3 late stage (IV) tumors. Five of 7 tumors had KRAS mutations in codon 12. Interrogation of tumor lysates with phospho-receptor tyrosine kinase arrays (R & D Systems) revealed activation of EGFR in all tumors, ERB2/HER2 receptors in 2 of 7 tumors, FGFR1/3 in 6 of 7 tumors, and Tie-2 receptor in 4 of 7 tumors. Based on the ubiquitous expression of EGFR family receptors and the presence of activated KRAS we assessed the efficacy of EGFR and MEK inhibitors on pancreatic cancer cell growth in culture and in the orthotopic xenograft model. A subset of patient-derived tumors adapted for growth in cell culture as well as 4 well established PDAC cell lines (MPanc96, L3.6pl, BxPC-3, PANC-1) were treated with erlotinib (EGFR inhibitor) or lapatinib (EGFR/HER2 inhibitor) and cell proliferation was assessed in a 5 day growth assay. None of the pancreatic cancer cell lines exhibited significant growth inhibition to either drug at concentrations known to be inhibitory in a sensitive cell line, SKBr3. In contrast, treatment of the pancreatic cancer cells with lapatinib in addition to a MEK inhibitor, GSK1120212, significantly inhibited cell growth in all but one of the cell lines tested. Three patient-derived tumors, including both KRAS wild type and mutant tumors, were tested in the orthotopic xenograft model for sensitivity to lapatinib, GSK1120212, or the combination of the two inhibitors. Treatment with lapatinib induced modest inhibition of tumor growth (approximately 30-50%), GSK1120212 treatment led to an approximate 60-80% reduction in tumor volume, whereas treatment with both lapatinib and GSK1120212 led to tumor regression in two tumors and greater than 80% inhibition in another. These data indicate that simultaneous inhibition of the EGF receptor and MAP kinase pathways may prove efficacious in inhibiting tumor proliferation in some primary PDACs. The effectiveness of this approach in inhibiting growth of other patient-derived tumors is under study. Supported by funding from NCI, ACS and UVa Cancer Center. 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 1592. doi:10.1158/1538-7445.AM2011-1592

Abstract LB-241: Cancer-associated fibroblasts modulate growth- and metastasis-promoting pathways in human pancreatic cancer cells and augment orthotopic tumor growth in mice

Proceedings: AACR 101st Annual Meeting 2010‐‐ Apr 17‐21, 2010; Washington, DC Background: The role of cancer-associated fibroblasts (CAFs) in the development, progression, and metastasis of pancreatic ductal adenocarcinoma (PDAC) is not completely understood. We sought to better characterize the role of CAFs by evaluating the effect of co-culturing CAFs and pancreatic cancer cells on growth and metastasis pathways. Methods: Resected human PDACs were grown orthotopically in mice. From these tumors, human pancreatic cancer cells and mouse CAFs were isolated and grown in culture. Three cell culture environments were created: 1) pure (>99%) human pancreatic cancer cells, 2) pure (97%) mouse CAFs, and 3) co-culture of both cell types. IHC and FACS were used to confirm cell type and species of origin. Phospho-receptor tyrosine kinase (pRTK) and cytokine arrays were performed on the three groups. Additionally, the effect of CAFs on PDAC growth was evaluated in nude mice by orthotopically injecting cancer cells (1 × 106 cells) with and without CAFs (1 × 106 cells). Results: CAFs stained positively for -smooth muscle actin (-SMA) but were negative for E-cadherin, while cancer cells stained positively for E-cadherin, but not -SMA. FACS for MHC-I confirmed mouse origin of the CAFs (negative) and human origin of the cancer cells (positive). Co-culture of mouse fibroblasts and human tumor cells led to significant upregulation of cell proliferation pathways (evidenced by increased human pRTKs and cytokines, including EGFR1, EGFR2, c-Met, Ron, IGF-1R, and thrombospondin-2), angiogenic pathways (evidenced by increased secretion of VEGF, IL-8, and angiogenin) and matrix degradation and remodeling pathways (increased secretion of MMPs 8 and 9, TIMPs 1 and 4, and uPA). Orthotopic mouse injection of human pancreatic cancer cells in combination with mouse CAFs (1:1 ratio) led to larger tumors at 3 weeks as compared to injection with cancer cells alone (1129 mm3 vs. 443 mm3, p < 0.005). Conclusions: Using co-culture of CAFs and pancreatic cancer cells we have recapitulated the modulation of pathways responsible for cell proliferation, angiogenesis, and matrix remodeling thought to occur in vivo during tumor progression. Further, we show that co-injection of CAFs and pancreatic cancer cells significantly augments orthotopic tumor growth in mice. These studies lay the groundwork for future studies to define the critical factors produced by stromal fibroblasts and the role of such factors in PDAC progression, allowing new insights into improving patient therapy. 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-241.

Abstract LB-158: A human xenograft model for developing personalized targeted therapy for pancreatic cancer

Background: Effective treatment regimens for pancreatic ductal adenocarcinoma (PDAC) are currently lacking. Molecular-targeted therapies, while promising, have been ineffective likely due to the heterogeneity and redundancy of molecular signaling pathways. Identification of predictors of response to defined targeted therapies is critical for the development of effective and personalized therapies. Methods: We have established a human PDAC tumor bank and have orthotopically implanted patient tumors into the pancreas of immunocompromised mice. Clinicopathologic data has been collected for each patient9s tumor. Tumors successfully propagated in mice are routinely screened for six genetic mutations commonly found in pancreatic cancer. Gene expression profiling and phospho-receptor tyrosine kinase (pRTK) arrays, cytokine arrays, and reverse phase protein arrays (RPPAs) are used to profile the activated signaling pathways in individual tumors. A unique genetic and molecular profile is then constructed for each human tumor. Ingenuity pathway analysis software (Ingenuity Systems, Inc., Redwood, CA) is being implemented to map the unique signaling network for each tumor using the genetic and molecular data. Results: To date 7 tumors have been analyzed, including 2 metastatic tumors and 5 primary adenocarcinomas. All tumors contained TP53 gene mutation, whereas 5 tumors exhibited mutated KRAS and 3 contained mutations in the SMAD4 gene. Analysis using pRTK arrays revealed universal activation of EGFR and variable activation of ErbB2/Her2, RON, Tie-2, FGF-R1 and 3, and Axl. The profile of pRTKs appeared stable upon tumor passage both in vivo and in culture. RPPAs revealed significant variation among tumors in activation for MAPK, AKT, SAPK, and p38. Additional cytokine/growth factor array analysis and gene expression profiling is currently underway. Conclusion: The establishment of an orthotopic human pancreatic cancer xenograft model allows for the systematic analysis of genetic and molecular characteristics of human tumors propagated within a relevant tumor microenvironment. This model affords the ability to assess tumor growth responses to targeted therapies currently in use for multiple malignancies and to correlate tumor response with genetic perturbations, changes in gene expression and activation of cell signaling networks. This model will be a significant step toward developing personalized targeted therapy for pancreatic 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 LB-158.