First-in-Class Humanized Antibody against Alternatively Spliced Tissue Factor Augments Anti-Metastatic Efficacy of Chemotherapy in a Preclinical Model of Pancreatic Ductal Adenocarcinoma

Alternatively spliced tissue factor (asTF) promotes the progression of pancreatic ductal adenocarcinoma (PDAC) by activating β1-integrins on PDAC cell surfaces. hRabMab1, a first-in-class humanized inhibitory anti-asTF antibody we recently developed, can suppress PDAC primary tumor growth as a single agent. Whether hRabMab1 has the potential to suppress metastases in PDAC is unknown. Following in vivo screening of three asTF-proficient human PDAC cell lines, we chose to make use of KRAS G12V-mutant human PDAC cell line PaCa-44, which yields aggressive primary orthotopic tumors with spontaneous spread to PDAC-relevant anatomical sites, along with concomitant severe leukocytosis. The experimental design featured orthotopic tumors formed by luciferase labeled PaCa-44 cells; administration of hRabMab1 alone or in combination with gemcitabine/paclitaxel (gem/PTX); and the assessment of the treatment outcomes on the primary tumor tissue as well as systemic spread. When administered alone, hRabMab1 exhibited poor penetration of tumor tissue; however, hRabMab1 was abundant in tumor tissue when co-administered with gem/PTX, which resulted in a significant decrease in tumor cell proliferation; leukocyte infiltration; and neovascularization. Gem/PTX alone reduced primary tumor volume, but not metastatic spread; only the combination of hRabMab1 and gem/PTX significantly reduced metastatic spread. RNA-seq analysis of primary tumors showed that the addition of hRabMab1 to gem/PTX enhanced the downregulation of tubulin binding and microtubule motor activity. In the liver, hRabMab1 reduced liver metastasis as a single agent. Only the combination of hRabMab1 and gem/PTX eliminated tumor cell-induced leukocytosis. We here demonstrate for the first time that hRabMab1 may help suppress metastasis in PDAC. hRabMab1's ability to improve the efficacy of chemotherapy is significant and warrants further investigation.

Abstract 2359: Cellular origin and functional contribution of alternatively spliced tissue factor to the malignant progression of chronic liver disease

Background: Expression of alternatively spliced Tissue Factor (asTF), an activator of αvβ3 and α6β1 integrins, is low in the healthy liver. asTF levels in plasma exhibit a biphasic pattern in the progression of chronic liver disease (CLD): spiking in early fibrosis then declining until the onset of cirrhosis, after which asTF levels rise again in hepatocellular carcinoma (HCC). asTF can promote angiogenesis and monocyte invasion, two key features of early fibrosis and the development of HCC, the risk of which is up to 45-fold higher in cirrhotic patients. The cellular source of asTF in the liver and the mechanisms that promote its expression there are unknown. Aim: To explore the cellular origin and mechanistic underpinnings of asTF’s upregulation in CLD and HCC.

Methods: Extracellular microvesicles (MVs) and asTF protein were measured in CLD plasma. MVs were concentrated by ultracentrifugation, quantified using CountBright™ Plus Absolute Counting Beads and characterized by flow cytometry. Plasma asTF was measured by ELISA. Expression of asTF protein in liver sections of mice with experimental hepatic fibrosis (carbon tetrachloride (CCl4) or high trans-fat diet (HTFD)) and in human liver (healthy, early fibrotic, late fibrotic, cirrhotic, and HCC) was examined by immunohistochemistry. asTF mRNA and protein expression levels were studied in human hepatocyte-like HCC cell lines HepG2 and Huh7, LX-2 (stellate cells), and TMNK1 (liver sinusoidal endothelial cells). TMNK1 and LX-2 were stimulated with TNFα (20 ng/mL) and angiotensin II (10 nM).

Results: Plasma asTF levels associated positively with the levels of endothelial MVs; the level of significance rose with CLD severity. Compared to control mice, asTF staining was strong in central vein endothelium in CCl4-challenged and HTFD-fed mice. asTF co-localized with CD31 and CD68 in the human liver; again, asTF positivity rose with disease severity. In agreement with our earlier findings in human plasma, asTF expression was minimal in healthy tissue, high in early-stage fibrosis, and moderate in late-stage fibrosis; HCC tissues were highly positive for asTF. Constitutive asTF expression was low in HepG2 and Huh7 cells compared to LX-2 and TMNK1 cells. Treatment of TMNK1 cells with TNFα induced asTF protein expression, which persisted beyond 6 hours post-induction. TNFα treatment of TMNK1 cells increased the release of asTF protein and CD31+ MVs. Treatment of LX-2 cells with angiotensin II also induced transient asTF expression. Compared to control cells, asTF-overexpressing TMNK1 cells facilitated transmigration of monocytes in Boyden chamber assays.

Conclusions: Non-parenchymal cells likely contribute to the increased levels of asTF in CLD. While the precise role of asTF in progression of CLD requires further study, monocyte accumulation in liver tissue is likely to be facilitated by asTF.

Citation Format: Clayton S. Lewis, Kateryna Stone, Damaris Kuhnell, Scott Langevin, Alejandro Soto-Gutierrez, Patrick Van Dreden, Jiang Wang, James Luyendyk, Vladimir Bogdanov. Cellular origin and functional contribution of alternatively spliced tissue factor to the malignant progression of chronic liver disease [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2359.

Potential utility of a multi-component coagulation factor panel to calculate MELD scores and assess the risk of portal vein thrombosis in chronic liver disease

BACKGROUND

Current quantitative approaches to assess chronic liver disease (CLD) severity have limitations. Further, portal vein thrombosis (PVT) pre-liver transplant (LT) is a major contributor to morbidity in CLD; the means of detecting and/or predicting PVT are limited. We sought to explore whether plasma coagulation factor activity levels can serve as a substitute for prothrombin time/international normalized ratio (PT/INR) in the Model for End-stage Liver Disease (MELD), and/or help assess the risk of PVT.

METHODS

Plasma activity levels of Factor V (FV), Factor VIII (FVIII), Protein C (PC), and Protein S (PS) and the concentrations of D-dimer, sP-selectin, and asTF were assessed in two cohorts of CLD patients (ambulatory, n = 42; LT, n = 43).

RESULTS

FV and PC activity levels strongly correlated with MELD scores, which enabled the development of a novel scoring system based on multiple linear regressions of the correlations of FV and PC activity with MELD-Na that substitutes PT/INR. Six-month and 1-year follow-up revealed that our novel approach was non-inferior to MELD-Na at predicting mortality. A significant inverse correlation between FVIII activity levels and PVT was found in the LT cohort (p = 0.010); FV and PS activity levels were in-trend (p = 0.069, p = 0.064). We developed a logistic regression-based compensation score to identify patients at risk of PVT.

CONCLUSIONS

We demonstrate that FV and PC activity levels may be used to replace PT/INR in MELD scoring. We also show the potential of using the combination of FV, FVIII, and PS activity levels to assess the risk of PVT in CLD.

Integrin regulation by tissue factor promotes cancer stemness and metastatic dissemination in breast cancer

Tissue Factor (TF) is the initiator of blood coagulation but also functions as a signal transduction receptor. TF expression in breast cancer is associated with higher tumor grade, metastasis and poor survival. The role of TF signaling on the early phases of metastasis has never been addressed. Here, we show an association between TF expression and metastasis as well as cancer stemness in 574 breast cancer patients. In preclinical models, blockade of TF signaling inhibited metastasis tenfold independent of primary tumor growth. TF blockade caused a reduction in epithelial-to-mesenchymal-transition, cancer stemness and expression of the pro-metastatic markers Slug and SOX9 in several breast cancer cell lines and in ex vivo cultured tumor cells. Mechanistically, TF forms a complex with β1-integrin leading to inactivation of β1-integrin. Inhibition of TF signaling induces a shift in TF-binding from α3β1-integrin to α6β4 and dictates FAK recruitment, leading to reduced epithelial-to-mesenchymal-transition and tumor cell differentiation. In conclusion, TF signaling inhibition leads to reduced pro-metastatic transcriptional programs, and a subsequent integrin β1 and β4-dependent reduction in metastasic dissemination.

A First-In-Class, Humanized Antibody Targeting Alternatively Spliced Tissue Factor: Preclinical Evaluation in an Orthotopic Model of Pancreatic Ductal Adenocarcinoma

In 2021, pancreatic ductal adenocarcinoma (PDAC) is the 3^rd leading cause of cancer deaths in the United States. This is largely due to a lack of symptoms and limited treatment options, which extend survival by only a few weeks. There is thus an urgent need to develop new therapies effective against PDAC. Previously, we have shown that the growth of PDAC cells is suppressed when they are co-implanted with RabMab1, a rabbit monoclonal antibody specific for human alternatively spliced tissue factor (asTF). Here, we report on humanization of RabMab1, evaluation of its binding characteristics, and assessment of its in vivo properties. hRabMab1 binds asTF with a K_D in the picomolar range; suppresses the migration of high-grade Pt45.P1 cells in Boyden chamber assays; has a long half-life in circulation (~ 5 weeks); and significantly slows the growth of pre-formed orthotopic Pt45.P1 tumors in athymic nude mice when administered intravenously. Immunohistochemical analysis of tumor tissue demonstrates the suppression of i) PDAC cell proliferation, ii) macrophage infiltration, and iii) neovascularization, whereas RNAseq analysis of tumor tissue reveals the suppression of pathways that promote cell division and focal adhesion. This is the first proof-of-concept study whereby a novel biologic targeting asTF has been investigated as a systemically administered single agent, with encouraging results. Given that hRabMab1 has a favorable PK profile and is able to suppress the growth of human PDAC cells in vivo, it comprises a promising candidate for further clinical development.

Abstract 908: Preclinical in vivo characterization of a first-in-class humanized antibody targeting alternatively spliced tissue factor

Tissue Factor, the initiator of the extrinsic pathway of coagulation, and its isoform alternatively spliced Tissue Factor (asTF) are often overexpressed in cancer cells. Previously, we have shown that RabMab1, a rabbit monoclonal antibody specific for human asTF, disrupts the binding of asTF to beta-integrins and thereby inhibits the growth of breast cancer and pancreatic ductal adenocarcinoma (PDAC) cell lines in vitro and in vivo. Here, we report on humanization of RabMab1, assessment of its binding characteristics, and determination of its in vivo properties. The variable regions of the heavy and light chains of hybridoma derived RabMab1 were cloned and used to generate a rabbit/human chimera (cRabMab1). Substitutions of species-specific residues were then carried out to produce humanized RabMab1 (hRabMab1; IgG1 isotype). Antigen binding was assessed via anti-human IgG Fc capture biosensor assays. cRabMab1 was found to have a KD of 4.24 nM whereas hRabMab1 was found to have a KD in the low picomolar range, which could not be precisely measured due to an extremely slow off-rate. The in vivo half-lives of each were determined to be 280 and 908 hours, respectively. Orthotopic co-implantation of cRabMab1 with high-grade, human PDAC cell line Pt45.P1 in athymic nude mice resulted in tumors that were 82% and 92% smaller than tumors in the vehicle and IgG control group groups, respectively, with no statistical difference between vehicle and IgG isotype control groups. Intravenous administration of hRabMab1 slowed the growth of pre-formed orthotopic Pt45.P1 tumors in athymic nude mice by 64% and 61% compared to vehicle and isotype control groups, respectively; again, there was no difference between vehicle and IgG isotype control groups. Immunohistochemical analysis of tumor tissue revealed a statistically significant 68% reduction in neovascularization (CD31), a 58% reduction in M2-polarized macrophages (CD206), and a 24% reduction in proliferating cells (Ki67) in the hRabMab1 cohort. RNAseq analysis of tumor tissue revealed that components of the focal adhesion system were the most affected by hRabMab1 treatment. In addition, a significant suppression of pathways that promote mitosis and the cell cycle was seen in hRabMab1-treated tumors. By qRT-PCR, we validated a greater than 82% reduction in the expression of HBEGF, a gene encoding a cell surface mitogen, and a greater than 68% reduction in the expression of STN1, a gene encoding a component of the CST-complex, a telomere replication and maintenance structure. This is the first proof-of-concept study whereby a novel biologic that inhibits asTF has been used as a systemically administered single agent, with encouraging results. Because hRabMab1 has a favorable pharmacokinetic profile and is able to suppress PDAC tumor cell growth in vivo, it is an attractive candidate for further clinical development.

Citation Format: Clayton S. Lewis, Aniruddha Karve, Kateryna Matiash, Timothy Stone, Jingxing Li, Jordan Wang, Henri Versteeg, Bruce Aronow, Syed Ahmad, Pankaj Desai, Vladimir Bogdanov. Preclinical in vivo characterization of a first-in-class humanized antibody targeting alternatively spliced tissue factor [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 908.

Abstract PO-041: Preclinical in vivo characterization of a first-in-class humanized antibody targeting alternatively spliced Tissue Factor

Tissue Factor, the initiator of the extrinsic pathway of coagulation, and its isoform alternatively spliced Tissue Factor (asTF) are often overexpressed in cancer cells. While asTF is only minimally procoagulant, it activates both the extracellular mechanical and intracellular signaling functions of beta-integrins. This leads to activation of multiple MAPK pathways thereby promoting increases in proliferation, migration, and angiogenesis. Previously, we have shown that RabMab1, a rabbit monoclonal antibody specific for human asTF, disrupts the binding of asTF to beta-integrins and thereby inhibits the growth of breast cancer and pancreatic ductal adenocarcinoma (PDAC) cell lines in vitro and in vivo. Here, we report on humanization of RabMab1, assessment of its binding characteristics, and determination of its in vivo properties. The variable regions of the heavy and light chains of hybridoma derived RabMab1 were cloned and used to generate a rabbit/human chimera (cRabMab1). Substitutions of species-specific residues were then carried out to produce humanized RabMab1 (hRabMab1; IgG1 isotype). Antigen binding was assessed via anti-human IgG Fc capture biosensor assays. cRabMab1 was found to have a KD of 4.24 nM whereas hRabMab1 was found to have a KD in the low picomolar range, which could not be precisely measured due to an extremely slow off-rate. The in vivo half-lives of each were determined to be 280 and 908 hours, respectively. Orthotopic co-implantation of cRabMab1 with high-grade, human PDAC cell line Pt45.P1 in athymic nude mice resulted in tumors that were 82% and 92% smaller than tumors in the vehicle and IgG control group groups, respectively, with no statistical difference between vehicle and IgG isotype control groups. Intravenous administration of hRabMab1 slowed the growth of pre-formed orthotopic Pt45.P1 tumors in athymic nude mice by 64% and 61% compared to vehicle and isotype control groups, respectively; again, there was no difference between vehicle and IgG isotype control groups. Immunohistochemical analysis of tumor tissue revealed a statistically significant 68% reduction in neovascularization (CD31), a 58% reduction in M2-polarized macrophages (CD206), and a 24% reduction in proliferating cells (Ki67) in the hRabMab1 cohort. RNAseq analysis of tumor tissue revealed a significant suppression of pathways that promote mitosis and the cell cycle. By qRT-PCR, we validated a greater than 82% reduction in the expression of HBEGF, a gene encoding a cell surface mitogen, and a greater than 68% reduction in the expression of STN1, a gene encoding a component of the CST-complex, a telomere replication and maintenance structure. This is the first proof-of-concept study whereby a novel biologic that targets asTF has been used as a systemically administered single agent, with encouraging results. Because hRabMab1 has a favorable pharmacokinetic profile and is able to suppress PDAC tumor growth in vivo, it comprises an attractive candidate for further clinical development.

Citation Format: Clayton S. Lewis, Aniruddha Karve, Kateryna Matiash, Timothy Stone, Pankaj Desai, Vladimir Y. Bogdanov. Preclinical in vivo characterization of a first-in-class humanized antibody targeting alternatively spliced Tissue Factor [abstract]. In: Proceedings of the AACR Virtual Special Conference on Pancreatic Cancer; 2020 Sep 29-30. Philadelphia (PA): AACR; Cancer Res 2020;80(22 Suppl):Abstract nr PO-041.

Enhanced Efficacy of Combination of Gemcitabine and Phosphatidylserine-Targeted Nanovesicles against Pancreatic Cancer

Phosphatidylserine (PS) is often externalized in viable pancreatic cancer cells and is therapeutically targetable using PS-selective drugs. One of the first-line treatments for advanced pancreatic cancer disease, gemcitabine (GEM), provides only marginal benefit to patients. We therefore investigated the therapeutic benefits of combining GEM and the PS-targeting drug, saposin C-dioleoylphosphatidylserine (SapC-DOPS), for treating pancreatic ductal adenocarcinoma (PDAC). Using cell-cycle analyses and a cell surface PS-based sorting method in vitro, we observed an increase in surface PS as cells progress through the cell cycle from G1 to G2/M. We also observed that GEM treatment preferentially targets G1 phase cells that have low surface PS, resulting in an increased median surface PS level of PDAC cells. Inversely, SapC-DOPS preferentially targets high surface PS cells that are predominantly in the G2/M phase. Finally, combination therapy in subcutaneous and orthotopic PDAC tumors in vivo with SapC-DOPS and GEM or Abraxane (Abr)/GEM (one of the current standards of care) significantly inhibits tumor growth and increases survival compared with individual treatments. Our studies confirm a surface PS and cell cycle-based enhancement of cancer cytotoxicity following SapC-DOPS treatment in combination with GEM or Abr/GEM. Thus, PDAC patients treated with Abr/GEM may benefit from concurrent administration of SapC-DOPS.

mTOR kinase inhibition reduces tissue factor expression and growth of pancreatic neuroendocrine tumors

Essentials Tissue factor (TF) isoforms are expressed in pancreatic neuroendocrine tumors (pNET). TF knockdown inhibits proliferation of human pNET cells in vitro. mTOR kinase inhibitor sapanisertib/MLN0128 suppresses TF expression in human pNET cells. Sapanisertib suppresses TF expression and activity and reduces the growth of pNET tumors in vivo. SUMMARY: Background Full-length tissue factor (flTF) and alternatively spliced TF (asTF) contribute to growth and spread of pancreatic ductal adenocarcinoma. It is unknown, however, if flTF and/or asTF contribute to the pathobiology of pancreatic neuroendocrine tumors (pNETs). Objective To assess TF expression in pNETs and the effects of mTOR complex 1/2 (mTORC1/2) inhibition on pNET growth. Methods Human pNET specimens were immunostained for TF. Human pNET cell lines QGP1 and BON were evaluated for TF expression and responsiveness to mTOR inhibition. shRNA were used to knock down TF in BON. TF cofactor activity was assessed using a two-step FXa generation assay. TF promoter activity was assessed using transient transfection of human TF promoter-driven reporter constructs into cells. Mice bearing orthotopic BON tumors were treated with the mTORC1/2 ATP site competitive inhibitor sapanisertib/MLN0128 (3 mg kg-1 , oral gavage) for 34 days. Results Immunostaining of pNET tissue revealed flTF and asTF expression. BON and QGP1 expressed both TF isoforms, with BON exhibiting higher levels. shRNA directed against TF suppressed BON proliferation in vitro. Treatment of BON with sapanisertib inhibited mTOR signaling and suppressed TF levels. BON tumors grown in mice treated with sapanisertib had significantly less TF protein and cofactor activity, and were smaller compared with tumors grown in control mice. Conclusions TF isoforms are expressed in pNETs. Sapanisertib suppresses TF mRNA and protein expression as well as TF cofactor activity in vitro and in vivo. Thus, further studies are warranted to evaluate the clinical utility of TF-suppressing mTORC1/2 inhibitor sapanisertib in pNET management.

Antibody-based targeting of alternatively spliced tissue factor: a new approach to impede the primary growth and spread of pancreatic ductal adenocarcinoma

Alternatively spliced Tissue Factor (asTF) is a secreted form of Tissue Factor (TF), the trigger of blood coagulation whose expression levels are heightened in several forms of solid cancer, including pancreatic ductal adenocarcinoma (PDAC). asTF binds to β1 integrins on PDAC cells, whereby it promotes tumor growth, metastatic spread, and monocyte recruitment to the stroma. In this study, we determined if targeting asTF in PDAC would significantly impact tumor progression. We here report that a novel inhibitory anti-asTF monoclonal antibody curtails experimental PDAC progression. Moreover, we show that tumor-derived asTF is able to promote PDAC primary growth and spread during early as well as later stages of the disease. This raises the likelihood that asTF may comprise a viable target in early- and late-stage PDAC. In addition, we show that TF expressed by host cells plays a significant role in PDAC spread. Together, our data demonstrate that targeting asTF in PDAC is a novel strategy to stem PDAC progression and spread.

Abstract A39: Expression of alternatively spliced tissue factor in pancreatic neuroendocrine tumors

Background: Pancreatic cancer remains extremely difficult to treat, resulting in an 80% 1-year mortality rate. Tissue Factor (TF) serves as a co-factor for serine protease factor VIIa and the full-length (fl)TF/VIIa complex initiates blood coagulation. Alternatively spliced isoform of TF (asTF) occurs naturally, is minimally coagulant and, in contrast to flTF, dispensable for normal hemostasis. flTF is overexpressed in many forms of cancer and contributes to malignant growth; however, targeting flTF is risky due to the possibility of bleeding complications. We previously described that asTF is highly expressed in pancreatic ductal adenocarcinoma (PDAC) which account for ~75% of pancreatic cancer cases. Through non-canonical interactions with β1 integrins, asTF promotes activation of Akt and p42/44 MAPK, thus potentiating cancer cell migration and proliferation. We recently developed asTF-specific monoclonal antibody that inhibited growth and spread of PDAC in vivo in an orthotopic setting (Unruh et al, Oncotarget, in press). At this time it is not known whether, aside from PDAC, asTF also contributes to pathobiology of other pancreatic tumors such as pancreatic neuroendocrine tumors (pNET). Although pNETs comprise a minority subset of pancreatic cancer cases, pNET incidence is rapidly increasing and new therapies are thus needed for patients who ultimately progress on second line therapies which include mTOR inhibitors.

Objective: To evaluate i) expression of asTF in pNET, and ii) potential utility of targeting intracellular pathways engaged by asTF in pNET.

Methods: A tissue microarray containing 6 human pNET specimens was immunostained for asTF. Two human pNET cell lines, QGP1 and BON (a kind gift of Dr. Courtney Townsend, UTMB), were evaluated for TF isoform expression and their responsiveness to mTOR inhibition using the dual PI3K/mTOR ATP-site competitive inhibitor BEZ235.

Results: All 6 pNET tissue specimens stained positive for asTF: 4 samples were highly positive and the remaining 2 moderately positive; normal pancreatic tissue specimens in the microarray exhibited minimal staining for asTF. qRT-PCR and western blotting analyses revealed that BON and QGP1 express flTF as well as asTF mRNA and protein, respectively. Compared to QGP1 cells, BON cells expressed ~3 fold more asTF and ~10 fold more flTF. Western blotting revealed that, compared to QGP1 cells, BON cells express significantly higher levels of β1 integrin. Treatment of QGP1 and BON cells with BEZ235 (400nM, 48 hours) markedly suppressed phosphorylation of mTOR targets including Akt, S6K1, 4E-BP1, and ULK1.

Conclusion: To our knowledge, this is the first study to report that flTF and asTF are expressed in pNET tumor tissue and cultured cells. In pNET cell lines QGP1 and BON, BEZ235 effectively reduced phosphorylation of Akt, a downstream target of the pathways activated by asTF:β1 interactions. Further studies are warranted to evaluate asTF as a potential target in pNET, specifically strategies aimed at concurrent inhibition of asTF:β1 interactions and Akt/S6K1 activity.

Citation Format: Clayton S. Lewis, Hala Elnakat Thomas, Fred V. Lucas, Vladimir Y. Bogdanov.{Authors}. Expression of alternatively spliced tissue factor in pancreatic neuroendocrine tumors. [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer: Advances in Science and Clinical Care; 2016 May 12-15; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2016;76(24 Suppl):Abstract nr A39.

Activation of carbonic anhydrase IX by alternatively spliced tissue factor under late-stage tumor conditions

Molecules of the coagulation pathway predispose patients to cancer-associated thrombosis and also trigger intracellular signaling pathways that promote cancer progression. The primary transcript of tissue factor, the main physiologic trigger of blood clotting, can undergo alternative splicing yielding a secreted variant, termed asTF (alternatively spliced tissue factor). asTF is not required for normal hemostasis, but its expression levels positively correlate with advanced tumor stages in several cancers, including pancreatic adenocarcinoma. The asTF-overexpressing pancreatic ductal adenocarcinoma cell line Pt45.P1/asTF+ and its parent cell line Pt45.P1 were tested for growth and mobility under normoxic conditions that model early-stage tumors, and in the hypoxic environment of late-stage cancers. asTF overexpression in Pt45.P1 cells conveys increased proliferative ability. According to cell cycle analysis, the major fraction of Pt45.P1/asTF+ cells reside in the dividing G₂/M phase of the cell cycle, whereas the parental Pt45.P1 cells are mostly confined to the quiescent G₀/G₁ phase. asTF overexpression is also associated with significantly higher mobility in cells plated under either normoxia or hypoxia. A hypoxic environment leads to upregulation of carbonic anhydrase IX (CAIX), which is more pronounced in Pt45.P1/asTF+ cells. Inhibition of CAIX by the compound U-104 significantly decreases cell growth and mobility of Pt45.P1/asTF+ cells in hypoxia, but not in normoxia. U-104 also reduces the growth of Pt45.P1/asTF+ orthotopic tumors in nude mice. CAIX is a novel downstream mediator of asTF in pancreatic cancer, particularly under hypoxic conditions that model late-stage tumor microenvironment.

LCL124, a cationic analog of ceramide, selectively induces pancreatic cancer cell death by accumulating in mitochondria

Treatment of pancreatic cancer that cannot be surgically resected currently relies on minimally beneficial cytotoxic chemotherapy with gemcitabine. As the fourth leading cause of cancer-related death in the United States with dismal survival statistics, pancreatic cancer demands new and more effective treatment approaches. Resistance to gemcitabine is nearly universal and appears to involve defects in the intrinsic/mitochondrial apoptotic pathway. The bioactive sphingolipid ceramide is a critical mediator of apoptosis initiated by a number of therapeutic modalities. It is noteworthy that insufficient ceramide accumulation has been linked to gemcitabine resistance in multiple cancer types, including pancreatic cancer. Taking advantage of the fact that cancer cells frequently have more negatively charged mitochondria, we investigated a means to circumvent resistance to gemcitabine by targeting delivery of a cationic ceramide (l-t-C6-CCPS [LCL124: ((2S,3S,4E)-2-N-[6'-(1″-pyridinium)-hexanoyl-sphingosine bromide)]) to cancer cell mitochondria. LCL124 was effective in initiating apoptosis by causing mitochondrial depolarization in pancreatic cancer cells but demonstrated significantly less activity against nonmalignant pancreatic ductal epithelial cells. Furthermore, we demonstrate that the mitochondrial membrane potentials of the cancer cells were more negative than nonmalignant cells and that dissipation of this potential abrogated cell killing by LCL124, establishing that the effectiveness of this compound is potential-dependent. LCL124 selectively accumulated in and inhibited the growth of xenografts in vivo, confirming the tumor selectivity and therapeutic potential of cationic ceramides in pancreatic cancer. It is noteworthy that gemcitabine-resistant pancreatic cancer cells became more sensitive to subsequent treatment with LCL124, suggesting that this compound may be a uniquely suited to overcome gemcitabine resistance in pancreatic cancer.

Antitumor activity of sphingosine kinase 2 inhibitor ABC294640 and sorafenib in hepatocellular carcinoma xenografts

The balance between the pro-apoptotic lipids ceramide and sphingosine and the pro-survival lipid sphingosine 1-phosphate (S1P) is termed the "sphingosine rheostat". Two isozymes, sphingosine kinase 1 and 2 (SK1 and SK2), are responsible for phosphorylation of pro-apoptotic sphingosine to form pro-survival S1P. We have previously reported the antitumor properties of an SK2 selective inhibitor, ABC294640, alone or in combination with the multikinase inhibitor sorafenib in mouse models of kidney carcinoma and pancreatic adenocarcinoma. Here we evaluated the combined antitumor effects of the aforementioned drug combination in two mouse models of hepatocellular carcinoma. Although combining the SK2 inhibitor, ABC294640, and sorafenib in vitro only afforded additive drug-drug effects, their combined antitumor properties in the mouse model bearing HepG2 cells mirrored effects previously observed in animals bearing kidney carcinoma and pancreatic adenocarcinoma cells. Combining ABC294640 and sorafenib led to a decrease in the levels of phosphorylated ERK in SK-HEP-1 cells, indicating that the antitumor effect of this drug combination is likely mediated through a suppression of the MAPK pathway in hepatocellular models. We also measured levels of S1P in the plasma of mice treated with two different doses of ABC294640 and sorafenib. We found decreases in the levels of S1P in plasma of mice treated daily with 100 mg/kg of ABC294640 for 5 weeks, and this decrease was not affected by co-administration of sorafenib. Taken together, these data support combining ABC294640 and sorafenib in clinical trials in HCC patients. Furthermore, monitoring levels of S1P may provide a pharmacodynamic marker of ABC294640 activity.

The oceanic carbonate system: a reassessment of biogenic controls

Fluxes of biogenic carbonates moving out of the euphotic zone and into deeper undersaturated waters of the North Pacific were estimated with free-drifting sediment traps. Short-duration (1 to 1.5 day) sampling between 100 and 2200 meters points to a major involvement in the oceanic carbonate system by a class of organisms which had been relegated to a secondary role-aragonitic pteropods. Pteropod fluxes through the base of the euphotic zone are almost large enough to balance the alkalinity budget for the Pacific Ocean. Dissolution experiments with freshly collected materials shed considerable light on a mystery surrounding these labile organisms: although plankton collections from net tows almost always contain large numbers of pteropods, these organisms are never a major component of biogenic materials in long-duration sediment trap collections. Their low abundance in long-duration collections results from dissolution subsequent to collection. Shortduration sampling showed significant increases in the ratio of calcitic foraminifera to aragonitic pteropods in undersaturated waters, indicating the more stable mineralogic form, calcite, was preserved relative to aragonite. Approximately 90 percent of the aragonite flux is remineralized in the upper 2.2 kilometers of the water column.

Role of stromelysin 1 and gelatinase B in experimental acute lung injury

Matrix metalloproteinases (MMPs) are upregulated locally in sites of inflammation, including the lung. Several MMP activities are upregulated in acute lung injury models but the exact role that these MMPs play in the development of the lung injury is unclear due to the absence of specific inhibitors. To determine the involvement of individual MMPs in the development of lung injury, mice genetically deficient in gelatinase B (MMP-9) and stromelysin 1 (MMP-3) were acutely injured with immunoglobulin G immune complexes and the intensity of the lung injury was compared with genetically identical wild-type (WT) mice with normal MMP activities. In the WT mice there was upregulation of gelatinase B and stromelysin 1 in the injured lungs which, as expected, was absent in the genetically deficient gelatinase B- and stromelysin 1-deficient mice, respectively. In the deficient mice there was little in the way of compensatory upregulation of other MMPs. The gelatinase B- and the stromelysin 1-deficient mice had less severe lung injury than did the WT controls, suggesting that both MMPs are involved in the pathogenesis of the lung injury. Further, the mechanism of their involvement in the lung injury appears to be different, with the stromelysin 1-deficient mice having a reduction in the numbers of neutrophils recruited into the lung whereas the gelatinase B-deficient mice had the same numbers of lung neutrophils as did the injured WT controls. These studies indicate, first, that both gelatinase B and stromelysin 1 are involved in the development of experimental acute lung injury, and second, that the mechanisms by which these individual MMPs function appear to differ.

The role of metalloelastase in immune complex-induced acute lung injury

Matrix metalloproteases (MMPs) are a group of zinc-dependent endopeptidases that can degrade every component of the extracellular matrix. Under normal circumstances, the levels of MMPs are tightly regulated at both transcriptional and posttranscriptional levels. However, they are up-regulated in pathological states such as inflammation. Previous investigations have suggested that MMP-12 (metalloelastase) may be an important mediator in the pathogenesis of chronic lung injury. In this study we investigated the role of metalloelastase in the pathogenesis of acute lung injury using mice containing a targeted disruption of the metalloelastase gene. Neutrophil influx into the alveolar space in metalloelastase-deficient animals was reduced to approximately 50% of that observed in parent strain mice following the induction of injury by immune complexes. In addition, lung permeability in metalloelastase-deficient mice was approximately 50% of that of injured parent strain animals with normal levels of metalloelastase and this was correlated with histological evidence of less lung injury in the metalloelastase-deficient animals. Collectively, the data suggest that metalloelastase is necessary for the full development of acute alveolitis in this model of lung injury. Further, the data suggest that reduced injury in metalloelastase-deficient mice is due in part to decreased neutrophil influx into the alveolar space.

Time-dependent inhibition of immune complex-induced lung injury by catalase: relationship to alterations in macrophage and neutrophil matrix metalloproteinase elaboration

Rats were subjected to acute lung injury by the intra-alveolar formation of IgG immune complexes of bovine serum albumin (BSA) and anti-BSA. In this model of injury, complement activation occurs and large numbers of neutrophils invade the interstitium and alveolar space. In the present study, animals were treated with intratracheal catalase concomitantly with anti-BSA or after a lag period of 5-120 min. Catalase treatment at time-zero or at 5 min post injury failed to prevent lung injury as indicated by permeability change, histological features, and neutrophil influx. However, treatment after a delay of 15-30 min (but not 120 min) afforded substantial protection. Consistent with past findings [19], lung injury was accompanied by an accumulation of matrix metalloproteinase 9 (MMP-9) in bronchoalveolar lavage (BAL) fluid. There was a strong correlation between inhibition of injury and reduction in MMP-9 levels. In vitro studies conducted in parallel revealed that unstimulated alveolar macrophages did not produce measurable MMP-9, while there was a large induction following exposure to the same immune complexes that initiated injury in vivo. MMP-2 was also slightly upregulated under the same conditions. Concomitant treatment with catalase greatly inhibited MMP-9 production by macrophages in response to immune complexes, but this treatment had little effect on basal production of either MMP-9 or MMP-2 by macrophage. The same concentration of catalase that suppressed MMP-9 elaboration also inhibited the production of tumor necrosis factor alpha. In contrast, when neutrophils were treated with catalase and then exposed to immune complexes, the antioxidant failed to prevent the release of either MMP-2 or MMP-9. Taken together, these findings demonstrate that antioxidant treatment interferes with elaboration of MMPs by alveolar macrophages. Protection against lung injury is correlated with reduction in MMP levels in the BAL fluid.

Leishmania mexicana amazonensis: differential display analysis and cloning of mRNAs from attenuated and infective forms

The virulence of Leishmania mexicana is determined by the concerted action of several parasite molecules. These cells lose their infectivity to host macrophages after prolonged cultivation in axenic growth media. Both virulent and attenuated variants of the parasite cells were cloned. The differential display reverse transcription-polymerase chain reaction technique was employed to understand whether this natural attenuation of the parasite cells is accompanied by differential expression of selected genes in those cells. Twelve different dinucleotide-anchored oligo(dT) antisense primers were used to make cDNAs from poly(A)+ mRNAs isolated from a clonal population of virulent and avirulent cells following a protocol optimized for Leishmania mRNAs. Those cDNAs were subjected to amplifications using each of the three different arbitrary decanucleotide primers and the corresponding anchored oligo(dT) primer. This procedure revealed four virulent-specific cDNA probes and one avirulent-specific cDNA probe. Differential expressions of these genes were confirmed by northern hybridization using the cloned cDNA probes. These results indicate that differential expression of genes may be the key in determining the molecular basis of leishmanial virulence.

The medical education system in Oklahoma

This paper provides a data base and analysis of the effectiveness of the public medical education system in Oklahoma. It provides the facts from which future decisions for Oklahoma health manpower policies might be developed.

Vibrio fluvialis and Vibrio furnissii isolated from a stool sample of one patient

Vibrio fluvialis and Vibrio furnissii have been associated with diarrhea but have rarely been isolated in the United States. We received strains of V. fluvialis and V. furnissii that were isolated from the stool of a 1-month-old baby. A description of these two strains and the case history of the patient are given in this report.