Dysregulated Immunity to Clostridioides difficile in IBD Patients Without a History of Recognized Infection

BACKGROUND & AIMS

Clostridioides difficile is a toxin-secreting bacteria that is an urgent antimicrobial resistance threat, with approximately 25% of patients developing recurrent infections. Inflammatory bowel disease (IBD) patients are at increased risk of severe, recurrent C. difficile infection.

METHODS

To investigate a role for C. difficile infection in IBD pathogenesis, we collected peripheral blood and stool from 20 each of ulcerative colitis patients, Crohn's disease patients, and healthy control subjects. We used a flow cytometric activation induced marker assay to quantify C. difficile toxin-specific CD4+ T cells and 16S ribosomal RNA sequencing to study microbiome diversity.

RESULTS

We found IBD patients had significantly increased levels of C. difficile toxin B-specific CD4+ T cells, but not immunoglobulin G or immunoglobulin A, compared with healthy control subjects. Within antigen-specific CD4+ T cells, T helper type 17 cells and cells expressing the gut homing receptor integrin β7 were reduced compared with healthy control subjects, similar to our previous study of non-IBD patients with recurrent C. difficile infection. Stool microbiome analysis revealed that gut homing, toxin-specific CD4+ T cells negatively associated with microbial diversity and, along with T helper type 17 cells, positively associated with bacteria enriched in healthy control subjects.

CONCLUSIONS

These data suggest that IBD patients, potentially due to underlying intestinal dysbiosis, experience undiagnosed C. difficile infections that result in impaired toxin-specific immunity. This may contribute to the development of inflammatory T cell responses toward commensal bacteria and provide a rationale for C. difficile testing in IBD patients.

Flagellin-specific human CAR Tregs for immune regulation in IBD

Regulatory T cell (Treg) therapy is a promising strategy to treat inflammatory bowel disease (IBD). Data from animal models has shown that Tregs specific for intestinal antigens are more potent than polyclonal Tregs at inhibiting colitis. Flagellins, the major structural proteins of bacterial flagella, are immunogenic antigens frequently targeted in IBD subjects, leading to the hypothesis that flagellin-specific Tregs could be an effective cell therapy for IBD. We developed a novel chimeric antigen receptor (CAR) specific for flagellin derived from Escherichia coli H18 (FliC). We used this CAR to confer FliC-specificity to human Tregs and investigated their therapeutic potential. FliC-CAR Tregs were activated by recombinant FliC protein but not a control flagellin protein, demonstrating CAR specificity and functionality. In a humanized mouse model, expression of the FliC-CAR drove preferential migration to the colon and expression of the activation marker PD1. In the presence of recombinant FliC protein in vitro, FliC-CAR Tregs were significantly more suppressive than control Tregs and promoted the establishment of colon-derived epithelial cell monolayers. These results demonstrate the potential of FliC-CAR Tregs to treat IBD and more broadly show the therapeutic potential of CARs targeting microbial-derived antigens.

Phage display of environmental protein toxins and virulence factors reveals the prevalence, persistence, and genetics of antibody responses

Microbial exposures are crucial environmental factors that impact healthspan by sculpting the immune system and microbiota. Antibody profiling via Phage ImmunoPrecipitation Sequencing (PhIP-Seq) provides a high-throughput, cost-effective approach for detecting exposure and response to microbial protein products. We designed and constructed a library of 95,601 56-amino acid peptide tiles spanning 14,430 proteins with "toxin" or "virulence factor" keyword annotations. We used PhIP-Seq to profile the antibodies of ∼1,000 individuals against this "ToxScan" library. In addition to enumerating immunodominant antibody epitopes, we studied the age-dependent stability of the ToxScan profile and used a genome-wide association study to find that the MHC-II locus modulates bacterial epitope selection. We detected previously described anti-flagellin antibody responses in a Crohn's disease cohort and identified an association between anti-flagellin antibodies and juvenile dermatomyositis. PhIP-Seq with the ToxScan library is thus an effective tool for studying the environmental determinants of health and disease at cohort scale.

An in vitro chronic damage model impairs inflammatory and regenerative responses in human colonoid monolayers

Acute damage to the intestinal epithelium can be repaired via de-differentiation of mature intestinal epithelial cells (IECs) to a stem-like state, but there is a lack of knowledge on how intestinal stem cells function after chronic injury, such as in inflammatory bowel disease (IBD). We developed a chronic-injury model in human colonoid monolayers by repeated rounds of air-liquid interface and submerged culture. We use this model to understand how chronic intestinal damage affects the ability of IECs to (1) respond to microbial stimulation, using the Toll-like receptor 5 (TLR5) agonist FliC and (2) regenerate and protect the epithelium from further damage. Repeated rounds of damage impair the ability of IECs to regrow and respond to TLR stimulation. We also identify mRNA expression and DNA methylation changes in genes associated with IBD and colon cancer. This methodology results in a human model of recurrent IEC injury like that which occurs in IBD.

Induction of stable human FOXP3+ Tregs by a parasite-derived TGF-β mimic

Immune homeostasis in the intestine is tightly controlled by FOXP3⁺ regulatory T cells (Tregs), defects of which are linked to the development of chronic conditions, such as inflammatory bowel disease (IBD). As a mechanism of immune evasion, several species of intestinal parasites boost Treg activity. The parasite Heligmosomoides polygyrus is known to secrete a molecule (Hp-TGM) that mimics the ability of TGF-β to induce FOXP3 expression in CD4⁺ T cells. The study aimed to investigate whether Hp-TGM could induce human FOXP3⁺ Tregs as a potential therapeutic approach for inflammatory diseases. CD4⁺ T cells from healthy volunteers were expanded in the presence of Hp-TGM or TGF-β. Treg induction was measured by flow cytometric detection of FOXP3 and other Treg markers, such as CD25 and CTLA-4. Epigenetic changes were detected using ChIP-Seq and pyrosequencing of FOXP3. Treg phenotype stability was assessed following inflammatory cytokine challenge and Treg function was evaluated by cellular co-culture suppression assays and cytometric bead arrays for secreted cytokines. Hp-TGM efficiently induced FOXP3 expression (> 60%), in addition to CD25 and CTLA-4, and caused epigenetic modification of the FOXP3 locus to a greater extent than TGF-β. Hp-TGM-induced Tregs had superior suppressive function compared with TGF-β-induced Tregs, and retained their phenotype following exposure to inflammatory cytokines. Furthermore, Hp-TGM induced a Treg-like phenotype in in vivo differentiated Th1 and Th17 cells, indicating its potential to re-program memory cells to enhance immune tolerance. These data indicate Hp-TGM has potential to be used to generate stable human FOXP3⁺ Tregs to treat IBD and other inflammatory diseases.

A method for expansion and retroviral transduction of mouse regulatory T cells

Adoptive cell therapy with genetically modified regulatory T cells (Tregs) is under clinical investigation for the treatment of transplant rejection and various autoimmune conditions. A limitation of modelling this approach in mice is the lack of optimized protocols for expanding and transducing mouse Tregs. Here we describe a protocol for purifying, expanding and retrovirally transducing mouse Tregs with a vector encoding a chimeric antigen receptor as a model transgene. We found that isolation of Tregs from C57Bl/6J Foxp3EGFP mice solely based on eGFP expression resulted in sufficiently pure cells; co-sorting of CD25hi cells was not essential. Although expansion with rapamycin reduced Treg expansion, it promoted maximal in vitro suppressive activity. Retroviral transduction of Tregs following 2 days of stimulation with anti-CD3/CD28 beads achieved a transduction efficiency of ~40% and did not impair their suppressive capacity. When injected into a conventional T cell (Tconv)-transfer-induced colitis model, transduced Tregs inhibited colitis progression at ratios as low as 1 Treg to 100 Tconvs, and maintained Foxp3 and transgene expression throughout an 8-week period. This method facilitates the study of transduced Tregs in animal models and will enable the study of genetically engineered Treg therapy for a variety of inflammatory diseases.

Suppressive and Gut-Reparative Functions of Human Type 1 T Regulatory Cells

BACKGROUND & AIMS

T-regulatory (Treg) cells suppress the immune response to maintain homeostasis. There are 2 main subsets of Treg cells: FOXP3 (forkhead box protein 3)-positive Treg cells, which do not produce high levels of effector cytokines, and type 1 Treg (Tr1) cells, which are FOXP3-negative and secrete interleukin (IL) 10. IL10 is an anti-inflammatory cytokine, so Tr1 cells might be used in the treatment of inflammatory bowel diseases. We aimed to develop methods to isolate and expand human Tr1 cells and define their functions.

METHODS

We obtained blood and colon biopsy samples from patients with Crohn's disease or ulcerative colitis or healthy individuals (controls). CD4+ T cells were isolated from blood samples and stimulated with anti-CD3 and anti-CD28 beads, and Tr1 cells were purified by using an IL10 cytokine-capture assay and cell sorting. FOXP3-positive Treg cells were sorted as CD4+CD25highCD127low cells from unstimulated cells. Tr1 and FOXP3-positive Treg cells were expanded, and phenotypes and gene expression profiles were compared. T cells in peripheral blood mononuclear cells from healthy donors were stimulated with anti-CD3 and anti-CD28 beads, and the suppressive abilities of Tr1 and FOXP3-positive Treg cells were measured. Human colon organoid cultures were established, cultured with supernatants from Tr1 or FOXP3-positive cells, and analyzed by immunofluorescence and flow cytometry. T84 cells (human colon adenocarcinoma epithelial cells) were incubated with supernatants from Tr1 or FOXP3-positive cells, and transepithelial electrical resistance was measured to determine epithelial cell barrier function.

RESULTS

Phenotypes of Tr1 cells isolated from control individuals vs patients with Crohn's disease or ulcerative colitis did not differ significantly after expansion. Tr1 cells and FOXP3-positive Treg cells suppressed proliferation of effector T cells, but only Tr1 cells suppressed secretion of IL1B and tumor necrosis factor from myeloid cells. Tr1 cells, but not FOXP3-positive Treg cells, isolated from healthy individuals and patients with Crohn's disease or ulcerative colitis secreted IL22, which promoted barrier function of human intestinal epithelial cells. Tr1 cell culture supernatants promoted differentiation of mucin-producing goblet cells in intestinal organoid cultures.

CONCLUSIONS

Human Tr1 cells suppress proliferation of effector T cells (adaptive immune response) and production of IL1B and TNF by myeloid cells (inmate immune response). They also secrete IL22 to promote barrier function. They might be developed as a cell-based therapy for intestinal inflammatory disorders.

Analysis of Flagellin-Specific Adaptive Immunity Reveals Links to Dysbiosis in Patients With Inflammatory Bowel Disease

BACKGROUND & AIMS

Bacterial flagellin is an important antigen in inflammatory bowel disease, but the role of flagellin-specific CD4⁺ T cells in disease pathogenesis remains unclear. Also unknown is how changes in intestinal microbiome intersect with those in microbiota-specific CD4⁺ T cells. We aimed to quantify and characterize flagellin-specific CD4⁺ T cells in Crohn's disease (CD) and ulcerative colitis (UC) patients and study their relationship with intestinal microbiome diversity.

METHODS

Blood was collected from 3 cohorts that included CD patients, UC patients, and healthy controls. Flow cytometry analyzed CD4⁺ T cells specific for Lachnospiraceae-derived A4-Fla2 and Escherichia coli H18 FliC flagellins, or control vaccine antigens. Serum antiflagellin IgG and IgA antibodies were detected by enzyme-linked immunosorbent assay and stool samples were collected and subjected to 16S ribosomal DNA sequencing.

RESULTS

Compared with healthy controls, CD and UC patients had lower frequencies of vaccine-antigen-specific CD4⁺ T cells and, as a proportion of vaccine-specific cells, higher frequencies of flagellin-specific CD4⁺ T cells. The proportion of flagellin-specific CD4⁺ T cells that were CXCR3^negCCR4⁺CCR6⁺ Th17 cells was reduced in CD and UC patients, with increased proportions of CD39⁺, PD-1⁺, and integrin β7⁺ cells. Microbiome analysis showed differentially abundant bacterial species in patient groups that correlated with immune responses to flagellin.

CONCLUSIONS

Both CD and UC patients have relative increases in the proportion of circulating Fla2-specific CD4⁺ T cells, which may be associated with changes in the intestinal microbiome. Evidence that the phenotype of these cells strongly correlate with disease severity provides insight into the potential roles of flagellin-specific CD4⁺ T cells in inflammatory bowel disease.

The differential effects of metronomic gemcitabine and antiangiogenic treatment in patient-derived xenografts of pancreatic cancer: treatment effects on metabolism, vascular function, cell proliferation, and tumor growth

BACKGROUND

Metronomic chemotherapy has shown promising activity against solid tumors and is believed to act in an antiangiogenic manner. The current study describes and quantifies the therapeutic efficacy, and mode of activity, of metronomic gemcitabine and a dedicated antiangiogenic agent (DC101) in patient-derived xenografts of pancreatic cancer.

METHODS

Two primary human pancreatic cancer xenograft lines were dosed metronomically with gemcitabine or DC101 weekly. Changes in tumor growth, vascular function, and metabolism over time were measured with magnetic resonance imaging, positron emission tomography, and immunofluorescence microscopy to determine the anti-tumor effects of the respective treatments.

RESULTS

Tumors treated with metronomic gemcitabine were 10-fold smaller than those in the control and DC101 groups. Metronomic gemcitabine, but not DC101, reduced the tumors' avidity for glucose, proliferation, and apoptosis. Metronomic gemcitabine-treated tumors had higher perfusion rates and uniformly distributed blood flow within the tumor, whereas perfusion rates in DC101-treated tumors were lower and confined to the periphery. DC101 treatment reduced the tumor's vascular density, but did not change their function. In contrast, metronomic gemcitabine increased vessel density, improved tumor perfusion transiently, and decreased hypoxia.

CONCLUSION

The aggregate data suggest that metronomic gemcitabine treatment affects both tumor vasculature and tumor cells continuously, and the overall effect is to significantly slow tumor growth. The observed increase in tumor perfusion induced by metronomic gemcitabine may be used as a therapeutic window for the administration of a second drug or radiation therapy. Non-invasive imaging could be used to detect early changes in tumor physiology before reductions in tumor volume were evident.

Kit-like 18F-labeling of RGD-19F-arytrifluroborate in high yield and at extraordinarily high specific activity with preliminary in vivo tumor imaging

INTRODUCTION

Positron Emission Tomography (PET) is a rapidly expanding, cutting edge technology for preclinical evaluation, cancer diagnosis and staging, and patient management. A one-step aqueous (18)F-labeling method, which can be applied to peptides to provide functional in vivo images, has been a long-standing challenge in PET imaging. Over the past few years, we have sought a rapid and mild radiolabeling method based on the aqueous radiosynthesis of in vivo stable aryltrifluoroborate (ArBF(3)(-)) conjugates. Recent access to production levels of (18)F-Fluoride led to a fluorescent-(18)F-ArBF(3)(-) at unprecedentedly high specific activities of 15Ci/μmol. However, extending this method to labeling peptides as imaging agents has not been explored.

METHODS

In order to extend these results to a peptide of clinical interest in the context of production-level radiosynthesis, we applied this new technology for labeling RGD, measured its specific activity by standard curve analysis, and carried out a preliminary evaluation of its imaging properties.

RESULTS

RGD was labeled in excellent radiochemical yields at exceptionally high specific activity (~14Ci/μmol) (n = 3). Preliminary tumor-specific images corroborated by ex vivo biodistribution data with blocking controls show statistically significant albeit relatively low tumor uptake along with reasonably high tumor:blood ratios (n = 3).

CONCLUSIONS

Isotope exchange on a clinically useful (18)F-ArBF(3)(-) radiotracer leads to excellent radiochemical yields and exceptionally high specific activities while the anionic nature of the aryltrifluoroborate prosthetic results in very rapid clearance. Since rapid clearance of the radioactive tracer is generally desirable for tracer development, these results suggest new directions for varying linker arm composition to slightly retard clearance rather than enhancing it.

ADVANCES IN KNOWLEDGE AND IMPLICATIONS FOR PATIENT CARE

This work is the first to use production levels of (18)F-activity to directly label RGD at specific activities that are an order of magnitude higher than most reports and thereby increases the distribution window for radiotracer production and delivery.

Imaging tumor vasculature noninvasively with positron emission tomography and RGD peptides labeled with copper 64 using the bifunctonal chelates DOTA, oxo-DO3a. and PCTA

Two novel bifunctional chelates, 3,6,9,15-tetraazabicyclo[9.3.1]pentadeca-1(15),11,13-triene-3,6,9-triacetic acid (PCTA) and 1-oxa-4,7,10-triazacyclododecane-4,7,10-triacetic acid (Oxo-DO3A), were found to radiolabel antibodies with copper 64 (64Cu) well for positron emission tomography (PET). In this study, the same chelators were used to radiolabel peptides with 64Cu for PET imaging of angiogenesis. PCTA, Oxo-DO3A, and 1,4,7,10-tetraazacyclododecane-N,N',N'',N'''-tetraacetic acid (DOTA) were conjugated to cyclic-(RGDyK), and their binding affinities were confirmed. Conditions for 64Cu radiolabeling were optimized for maximum yield and specific activity. The in vitro stability of the radiolabeled compounds was challenged with serum incubation. PET studies were carried out in a non-αvβ3-expressing tumor model to evaluate the compounds' specificity for proliferating tumor vasculature and their in vivo pharmacokinetics. The PCTA and Oxo-DO3A bioconjugates were labeled with 64Cu at higher effective specific activity and radiochemical yield than the DOTA bioconjugate. In the imaging studies, all the 64Cu bioconjugates could be used to visualize the tumor and the radiotracer uptake was blocked with cyclic-(RGDyK). Target uptake of each bioconjugate was similar, but differences in other tissues were observed. 64Cu-PCTA-RGD showed the best clearance from nontarget tissue and the highest tumor to nontarget ratios. PCTA was the most promising bifunctional chelate for 64Cu peptide imaging and warrants further investigation.

(68)Ga small peptide imaging: comparison of NOTA and PCTA

In this study, a bifunctional version of the chelate PCTA was compared to the analogous NOTA derivative for peptide conjugation, (68)Ga radiolabeling, and small peptide imaging. Both p-SCN-Bn-PCTA and p-SCN-Bn-NOTA were conjugated to cyclo-RGDyK. The resulting conjugates, PCTA-RGD and NOTA-RGD, retained their affinity for the peptide target, the α(v)β(3) receptor. Both PCTA-RGD and NOTA-RGD could be radiolabeled with (68)Ga in >95% radiochemical yield (RCY) at room temperature within 5 min. For PCTA-RGD, higher effective specific activities, up to 55 MBq/nmol, could be achieved in 95% RCY with gentle heating at 40 °C. The (68)Ga-radiolabeled conjugates were >90% stable in serum and in the presence of excess apo-transferrin over 4 h; (68)Ga-PCTA-RGD did have slightly lower stability than (68)Ga-NOTA-RGD, 93 ± 2% compared to 98 ± 1%, at the 4 h time point. Finally, the tumor and nontarget organ uptake and clearance of (68)Ga-radiolabeled PCTA-RGD and NOTA-RGD was compared in mice bearing HT-29 colorectal tumor xenografts. Activity cleared quickly from the blood and muscle tissue with >90% and >70% of the initial activity cleared within the first 40 min, respectively. The majority of activity was observed in the kidney, liver, and tumor tissue. The observed tumor uptake was specific with up to 75% of the tumor uptake blocked when the mice were preinjected with 160 nmol (100 μg) of unlabeled peptide. Uptake observed in the blocked tumors was not significantly different than the background activity observed in muscle tissue. The only significant difference between the two (68)Ga-radiolabeled bioconjugates in vivo was the kidney uptake. (68)Ga-radiolabeled PCTA-RGD had significantly lower (p < 0.05) kidney uptake (1.1 ± 0.5%) at 2 h postinjection compared to (68)Ga-radiolabeled NOTA-RGD (2.7 ± 1.3%). Overall, (68)Ga-radiolabeled PCTA-RGD and NOTA-RGD performed similarly, but the lower kidney uptake for (68)Ga-radiolabeled PCTA-RGD may be advantageous in some imaging applications.

Abstract 5261: Irinophore C, a liposomal formulation of irinotecan, has anti-vascular effects in primary tumors of colorectal cancer grown orthotopically in mice

Introduction: Colorectal cancer accounts for ∼10% of cancer deaths in North America. Our group has developed a series of primary tumors from human colorectal cancer tissue obtained during surgery. These tumors are passaged orthotopically in mice and maintain the complexity and heterogeneity of the original patient sample. We have used these tumors to examine the cytotoxic and anti-vascular effects of Irinophore CTM, a liposomal form of irinotecan, which is more efficacious and less toxic than the parent drug. Materials and Methods: Primary tumor tissues from colorectal cancer patients, were validated by a reference pathologist and implanted subcutaneously in SCID mice. Tumors that grew successfully were then passaged orthotopically on the ascending colon of new mice. When these tumors reached ∼200mm3, groups of mice were treated with saline, irinotecan (50mg/kg), or IrinophoreCTM (25mg/kg) once a week for 6 weeks. Separate groups of tumors, A, B and C were harvested on days 3, 21 and 42 after treatment started, respectively. Magnetic resonance imaging (MRI) was used to assess tumor perfusion in mice from group B. Treatment effects on tumor metabolism were assessed with 18F -fluorodeoxyglucose and positron emission tomography (FDG-PET) for groups A and C mice. Immunofluorescence staining was carried out on tumors from all treatment groups to determine levels of cell proliferation, apoptosis, hypoxia, and vessel density. Results: 4 of 14 samples were successfully propagated and maintain their original morphology. Irinophore CTM treatment reduced tumor volume by 54% to 92% compared to the untreated controls depending on the tumor line. No toxic effects were seen with Irinophore CTM. The aggregate data for cell proliferation (Ki67), necrosis (H&E) and cell death (TUNEL) indicate that Irinophore CTM has sustained cytotoxic activity compared to the free drug. Immunostaining data show irinotecan treatment did not change blood vessel density in the tumors; however, Irinophore CTM treatment did reduce vascular density in the tumors. The volume transfer coefficient, Ktrans, derived from MRI, decreased when tumors were treated with irinotecan, but increased with Irinophore CTM treatment. Differences in the metabolic activity of the tumors were also seen. Conclusion: Orthotopic models of colorectal cancer propagated from patient tumors were successfully developed. These models retain the characteristics of the original patient sample and are a good alternative to xenograft models grown from immortalized cell-lines. The anti-tumor activity of Irinophore CTM at lower doses is greater than irinotecan's, and with fewer side effects. Treatment with Irinophore CTM also reduces tumor metabolism and appears to improve vascular function. The data imply that Irinophore CTM has sustained anti-tumor activity and multiple mechanisms of action compared to irinotecan.

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 5261. doi:1538-7445.AM2012-5261

Abstract 1422: Cancer-associated fibroblasts influence the sensitivity of pancreatic cancer cells to gemcitabine in pancreatic ductal adenocarcinoma

Introduction: Pancreatic ductal adenocarcinoma is chemo- and radio-resistant, and has the worst survival rates of all cancers. Gemcitabine improves quality of life, but only provides modest survival benefits. Notably, pancreatic cancer is characterized by a strong “reactive” stroma in association with extensive fibroblast proliferation. Our hypothesis is that the large population of cancer-associated fibroblasts (CAFs) in pancreatic tumors produces a plethora of growth factors and cytokines which in turn, influence the sensitivity of pancreatic cancer cells to gemcitabine. Methods: Fourteen primary pancreatic cancer-associated fibroblast (CAF) lines were established in culture using freshly resected pancreatic tumor tissues from 14 different patients. To assess whether these CAFs influence chemosensitivity, MiaPaCa-2 pancreatic cancer cells were injected alone or co-injected with one of the CAF lines CAF11 subcutaneously into SCID mice. When tumors reached ∼200 mm3, mice bearing MiaPaCa-2 tumors or MiaPaCa-2+CAF11 tumors were treated with the vehicle control (0.9% saline) or gemcitabine (120 mg/kg, q7d, i.p.). Tumor volume was measured weekly. Concurrently, Affymetrix U133 plus 2.0 arrays were used to determine the differentially expressed genes in pancreatic CAFs vs. normal fibroblasts. The genes were then analyzed with Ingenuity Systems to identify network and canonical pathways that are altered in CAFs, and which may mediate chemosensitivity. Selected genes were further validated by RT-PCR, western blotting, or ELISA. Results: Gemcitabine was found to suppress the growth of MiaPaCa-2 tumors but not that of MiaPaCa-2+CAF11 tumors, suggesting that the presence of CAF11 renders MiaPaCa-2 cells more resistant to the drug. Affymetrix results showed that 1704 probe sets representing 1183 unique genes were differentially expressed by 2-fold or greater (P&lt;0.05) in primary pancreatic CAFs, of which 382 gene were upregulated and 801 genes were downregulated. Thirty-four of these genes were mapped to the highest ranking network whose molecular functions include “cell cycle, cancer”. IL-6 was the most highly upregulated gene (8.3-fold; P=2.20e-05) in this network. Furthermore, 19 and 11 other genes were mapped to two significant canonical pathways, “hepatic fibrosis/hepatic stellate cell activation” and “IL-6 signaling”, respectively. IL-6 was the central component of both canonical pathways. RT-PCR and ELISA data confirmed the increased expression of IL-6 and other soluble factors in CAFs. Conclusion: Primary pancreatic CAFs secrete elevated levels of various growth factors and cytokines such as IL-6, which may promote survival of pancreatic cancer cells and reduce their sensitivity to gemcitabine. These soluble factors are potential therapeutic targets in 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 1422.

Abstract 1296: Metronomic chemotherapy and DC101 induce unique changes in tumor vascular function and metabolic activity in pancreatic cancer

Introduction: Pancreatic cancer is clinically resistant to chemotherapy and radiation therapy, and newer targeted therapies have not remarkably improved survival. In a phase III trial, the addition of bevacizumab to the gemcitabine-erlotinib combination significantly increased survival vs. the the gemcitabine-erlotinib combination alone in pancreatic cancer patients (van Cutsem et al, JCO, 2009). This suggests that the vasculature in pancreatic tumors is a valid therapeutic target. It has been shown that antiangiogenic agents ‘normalize’ vascular function, and improve drug delivery to the tumor. Interestingly, data from our group indicated that metronomic chemotherapy regimens may have similar effects. The objective of the present study was to compare the effects of DC101, a dedicated antiangiogenic drug, and metronomic dosing of gemcitabine (Met-Gem) on the vascular function and metabolic activity of primary pancreatic tumors.

Method: Primary pancreatic tumors were grown orthotopically in SCID mice and treated with the vehicle control (0.9% saline), DC101 (800 ug, q3d, i.p.) or Met-Gem (30mg/kg, q3d, i.p.) for three weeks. Dynamic contrast-enhanced magnetic resonance imaging (DCE MRI) and 18F-Fluorodeoxygluose positron emission tomography (18F-FDG PET) were used to assess tumor perfusion and metabolism in situ, respectively, on days 3, 7 and 21 after treatment was initiated. Tumors were harvested at each time point after imaging. Immunofluorescence staining was performed on tumor cryosections followed by computerized image analysis to determine cell proliferation, apoptosis, and vessel density.

Results: On day 21, Met-Gem and DC101 reduced tumor volume by 97% (P&lt;0.05) and 26% (P&lt;0.05), respectively, compared to the vehicle control. 18F-FDG uptake was increased by 23% (P&lt;0.05) after DC101 treatment, but decreased by 35% (P&lt;0.05) following Met-Gem therapy. Ktrans values derived from DCE MRI indicated that Met-Gem-treated tumors were more perfused (+114%; P &lt;0.05) on day 7, but subsequently became less so on day 21 (−47%; P&lt;0.05). No significant changes in perfusion were observed with DC101 treatment. Immunostaining data showed that the percentage of CD31+ pixels was reduced by DC101 (−35%; P&lt;0.05), but increased by Met-Gem (+38%; P&lt;0.05), compared to the vehicle control. In addition, the average distance between blood vessels increased with DC101 (+53%; P&lt;0.05), but decreased with Met-Gem (−45%; P&lt;0.05) treatment, respectively.

Conclusion: Metronomic dosing of gemcitabine is more effective in controlling tumor growth, improving overall tumor perfusion, and reducing the overall metabolic activity in primary pancreatic adenocarcinoma compared to DC101. Based on these data, we postulate that using metronomic gemcitabine in combination therapies for pancreatic cancer may improve treatment efficacy by optimizing drug delivery to the cancer cells.

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 1296.

Systematic evaluation of candidate blood markers for detecting ovarian cancer

BACKGROUND

Epithelial ovarian cancer is a significant cause of mortality both in the United States and worldwide, due largely to the high proportion of cases that present at a late stage, when survival is extremely poor. Early detection of epithelial ovarian cancer, and of the serous subtype in particular, is a promising strategy for saving lives. The low prevalence of ovarian cancer makes the development of an adequately sensitive and specific test based on blood markers very challenging. We evaluated the performance of a set of candidate blood markers and combinations of these markers in detecting serous ovarian cancer.

METHODS AND FINDINGS

We selected 14 candidate blood markers of serous ovarian cancer for which assays were available to measure their levels in serum or plasma, based on our analysis of global gene expression data and on literature searches. We evaluated the performance of these candidate markers individually and in combination by measuring them in overlapping sets of serum (or plasma) samples from women with clinically detectable ovarian cancer and women without ovarian cancer. Based on sensitivity at high specificity, we determined that 4 of the 14 candidate markers--MUC16, WFDC2, MSLN and MMP7--warrant further evaluation in precious serum specimens collected months to years prior to clinical diagnosis to assess their utility in early detection. We also reported differences in the performance of these candidate blood markers across histological types of epithelial ovarian cancer.

CONCLUSIONS

By systematically analyzing the performance of candidate blood markers of ovarian cancer in distinguishing women with clinically apparent ovarian cancer from women without ovarian cancer, we identified a set of serum markers with adequate performance to warrant testing for their ability to identify ovarian cancer months to years prior to clinical diagnosis. We argued for the importance of sensitivity at high specificity and of magnitude of difference in marker levels between cases and controls as performance metrics and demonstrated the importance of stratifying analyses by histological type of ovarian cancer. Also, we discussed the limitations of studies (like this one) that use samples obtained from symptomatic women to assess potential utility in detection of disease months to years prior to clinical detection.