Abstract 3128: Efficacy of diethyldihydroxyhomospermine against human pancreatic adenocarcinoma using orthotopic implantation of human pancreatic L3.6pl cells into the pancreas of nude mice

Purpose: To determine the anti-neoplastic effects of (S,S)N1,N14-diethyl-3,12-dihydroxyhomospermine ([HO]2DEHSPM, SUN-101) after subcutaneous (s.c.) administration after orthotopic transplantation of human pancreatic cancer cells (L3.6pl) in the pancreas of nude mice.

Methods: L3.6pl cells were injected into the pancreas of nude mice and seven to ten days later the treatment groups were:

Study 1: mice (n=10/group) with saline (control), SUN-101 (25 mg/kg), SUN-101 (50 mg/kg), and SUN-101 (100 mg/kg) QD for 4 to 6 weeks.

Study 2: mice (n=10/group) with saline (control), SUN-101 (25 mg/kg, QD), SUN-101 (25 mg/kg three times a week, QOD), SUN-101 (15 mg/kg, QOD), and SUN-101 (5 mg/kg, QOD) for 4 to 6 weeks

Study 3: mice (n=10/group) with saline (control), Gemzar (100 mg/kg, intraperitoneal (i.p.), twice a week), SUN-101 (25 mg/kg, QOD), and Gemzar plus SUN-101 for 4 to 6 weeks.

Results: In study 1, the optimal dose of SUN-101 was determined to be 25 mg/kg QD. This dose reduced up to 82.9% the weight of human pancreatic tumors in mice. Treatment with 50 and 100 mg/kg doses resulted in decreased body weight and proved to be toxic in mice. Histologic changes in the liver included hepatocyte reparative change and in the exocrine pancreas included a mild decrease of cytoplasmic granules in the epithelium of the pancreatic acini.

In study 2, the optimal dose of 25 mg/kg administrated QOD was less toxic than daily 25 mg/kg administrations. The pancreatic weight and volume were decreased (47.8% and 66.6%, respectively) with 25 mg/kg administrated QOD and dose related decreases were observed at the 15 mg/kg QOD (20.1% and 52.6%, respectively). No decrease in tumor weight or volume was noted with 5 mg/kg administrated QOD.

In study 3, the treatment of Gemzar, SUN-101, and Gemzar plus SUN-101 resulted in 18.7%, 35.6%, and 42.4% decreases in the body weight, respectively. Compared with tumor-bearing control, the treatment of Gemzar, SUN-101, and Gemzar plus SUN-101 resulted in 24.7%, 58.8%, and 67.2% decreases in the pancreas weight, respectively, and 37.8%, 58.4%, and 72.9% decreases in the tumor volumes, respectively.

The incidence of liver metastasis was also decreased with SUN-101, Gemzar, and combination of Gemzar plus SUN-101.

Conclusions: SUN-101 administered QD or QOD 25 mg/kg inhibited the growth of human pancreatic carcinoma in mice. SUN-101 demonstrated higher toxicity including disruption of the digestive process at daily 50 and 100 mg/kg doses. Co-administration of SUN-101 with gemcitabine appeared to have an additive or synergistic effect on reduction in the pancreatic tumor.

Citation Format: Ajit K. Shah, Michael T. Cullen, Cheryl H. Baker. Efficacy of diethyldihydroxyhomospermine against human pancreatic adenocarcinoma using orthotopic implantation of human pancreatic L3.6pl cells into the pancreas of nude mice. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3128. doi:10.1158/1538-7445.AM2014-3128

Sensitization of pancreatic cancer cells to radiation by cerium oxide nanoparticle-induced ROS production

Side effect of radiation therapy (RT) remains the most challenging issue for pancreatic cancer treatment. In this report we determined whether and how cerium oxide nanoparticles (CONPs) sensitize pancreatic cancer cells to RT. CONP pretreatment enhanced radiation-induced reactive oxygen species (ROS) production preferentially in acidic cell-free solutions as well as acidic human pancreatic cancer cells. In acidic environments, CONPs favor the scavenging of superoxide radical over the hydroxyl peroxide resulting in accumulation of the latter whereas in neutral pH CONPs scavenge both. CONP treatment prior to RT markedly potentiated the cancer cell apoptosis both in culture and in tumors and the inhibition of the pancreatic tumor growth without harming the normal tissues or host mice. Taken together, these results identify CONPs as a potentially novel RT-sensitizer as well as protectant for improving pancreatic cancer treatment.

FROM THE CLINICAL EDITOR

Pancreatic tumors remain some of the most notoriously treatment-unresponsive malignancies. Cerium oxide nanoparticles may be capable of sensitizing such cells to radiotherapy, as demonstrated in this study.

MGMT inhibition restores ERα functional sensitivity to antiestrogen therapy

Antiestrogen therapy resistance remains a huge stumbling block in the treatment of breast cancer. We have found significant elevation of O(6) methylguanine DNA methyl transferase (MGMT) expression in a small sample of consecutive patients who have failed tamoxifen treatment. Here, we show that tamoxifen resistance is accompanied by upregulation of MGMT. Further we show that administration of the MGMT inhibitor, O(6)-benzylguanine (BG), at nontoxic doses, leads to restoration of a favorable estrogen receptor alpha (ERα) phosphorylation phenotype (high p-ERα Ser167/low p-ERα Ser118), which has been reported to correlate with sensitivity to endocrine therapy and improved survival. We also show BG to be a dual inhibitor of MGMT and ERα. In tamoxifen-resistant breast cancer cells, BG alone or in combination with antiestrogen (tamoxifen [TAM]/ICI 182,780 [fulvestrant, Faslodex]) therapy enhances p53 upregulated modulator of apoptosis (PUMA) expression, cytochrome C release and poly (ADP-ribose) polymerase (PARP) cleavage, all indicative of apoptosis. In addition, BG increases the expression of p21(cip1/waf1). We also show that BG, alone or in combination therapy, curtails the growth of tamoxifen-resistant breast cancer in vitro and in vivo. In tamoxifen-resistant MCF7 breast cancer xenografts, BG alone or in combination treatment causes significant delay in tumor growth. Immunohistochemistry confirms that BG increases p21(cip1/waf1) and p-ERα Ser167 expression and inhibits MGMT, ERα, p-ERα Ser118 and ki-67 expression. Collectively, our results suggest that MGMT inhibition leads to growth inhibition of tamoxifen-resistant breast cancer in vitro and in vivo and resensitizes tamoxifen-resistant breast cancer cells to antiestrogen therapy. These findings suggest that MGMT inhibition may provide a novel therapeutic strategy for overcoming antiestrogen resistance.

Abstract 1468: Cerium oxide nanoparticles sensitize pancreatic cancer cells to radiation by modulating the JNK pathway

Pancreatic cancer, one of the most lethal cancers, has a poor prognosis and a high mortality rate. Currently, the absence of effective therapies increases reliance on radiation therapy (RT) to treat pancreatic cancer. We have previously reported that Cerium Oxide Nanoparticles (CONPs) are selectively toxic to cancer cells and possess the ability to selectively sensitize pancreatic cancer cells to radiation-induced cell death. Radiation-induced H2O2 production was significantly increased in the presence of less than or equal to 10 µM of CONPs and radiation-induced ROS production was increased in human L3.6pl pancreatic cancer cells pre-treated with 10 µM CONPs, which correlated with a significant decrease in cell viability and clonogenicity as compared to radiation alone. Conversely, ROS production was decreased in normal hTERT-HPNE pancreatic cells without impacting cell viability. The volume of pancreatic tumors was reduced by 48% in mice treated with combination therapy compared to radiation alone. Immunohistochemical (IHC) analysis revealed that combination therapy resulted in a significant increase in tumor cell apoptosis. In the most recent study, we determined the mechanism responsible for the increase in apoptosis as a result of increased ROS levels. L3.6pl cells (radiation sensitive), PANC-1 (radiation resistant) and HPNE (normal pancreatic cells) were treated with 5 Gy radiation in the presence or absence of 10 µM CONPs. CONPs selectively increased RT-induced Thioredoxin (TRX) oxidation in the cancer cells (L3.6pl: 14.2%, p<0.001; PANC-1: 23.5%, p<0.005) which correlated with a 35-40% increase in ASK-1 phosphorylation in both cell lines. Excitingly, western blot analyses showed a selective increase in JNK phosphorylation in both radiation sensitive (L3.6pl: JNK1 at 15%, JNK2 at 20%) and radiation resistant (PANC-1: JNK1 at 36%, JNK2 at 37%) cells which correlated with an increase in Caspase 3/7 activity (L3.6pl: 36.4%, p<0.05; PANC-1: 43.1%, p<0.05) compared to radiation alone. Knockdown of JNK expression by siRNA resulted in abrogation of Caspase 3/7 activity and corresponding cell death. Combination therapy of CONPs and radiation in an orthotopic murine model produced significant increases in JNK phosphorylation and Caspase 3 cleavage shown by IHC analysis. These data suggest that CONPs may act as a radiosensitizer in treatment of pancreatic cancer through the induction of JNK activation.

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 1468. doi:1538-7445.AM2012-1468

Blockade of MUC1 expression by glycerol guaiacolate inhibits proliferation of human breast cancer cells

We sought to determine whether administration of glycerol guaiacolate at an optimal biological dose inhibits human breast cancer cell growth. Human breast cancer MCF-7 and ZR-75-1 cells were treated with glycerol guaiacolate and the therapeutic efficacy and biological activity of this drug was investigated on breast cancer cell growth. MCF-7 cells were injected into the mammary fat pad of overectamized female athymic nude mice. Ten days later, animals were treated with daily intraperitoneal injections of glycerol guaiacolate for six weeks. Tumor size and volume was monitored and immunohistochemistry analysis on MUC1, p21 and ki-67 was performed. Glycerol guaiacolate decreased breast cancer cell growth in a dose-dependent manner, decreased cell migration, and caused G1 cell cycle arrest. Our results demonstrate that glycerol guaiacolate inhibits MUC1 protein and mRNA expression levels and significantly increased p21 expression in human breast cancer cells as well as induced PARP cleavage. Similarly, glycerol guaiacolate inhibited breast tumor growth in vivo as well as enhanced p21 expression and decreased breast tumor cell proliferation (ki-67 expression). Collectively, our results demonstrate that glycerol guaiacolate decreased MUC1 expression and enhanced cell growth inhibition by inducing p21 expression in breast cancer cells. These findings suggest that glycerol guaiacolate may provide a novel and effective approach for the treatment of human breast cancer.

A facile nanoparticle immunoassay for cancer biomarker discovery

BACKGROUND

Gold nanoparticles (AuNPs) scatter light intensely at or near their surface plasmon wavelength region. Using AuNPs coupled with dynamic light scattering (DLS) detection, we developed a facile nanoparticle immunoassay for serum protein biomarker detection and analysis. A serum sample was first mixed with a citrate-protected AuNP solution. Proteins from the serum were adsorbed to the AuNPs to form a protein corona on the nanoparticle surface. An antibody solution was then added to the assay solution to analyze the target proteins of interest that are present in the protein corona. The protein corona formation and the subsequent binding of antibody to the target proteins in the protein corona were detected by DLS.

RESULTS

Using this simple assay, we discovered multiple molecular aberrations associated with prostate cancer from both mice and human blood serum samples. From the mice serum study, we observed difference in the size of the protein corona and mouse IgG level between different mice groups (i.e., mice with aggressive or less aggressive prostate cancer, and normal healthy controls). Furthermore, it was found from both the mice model and the human serum sample study that the level of vascular endothelial growth factor (VEGF, a protein that is associated with tumor angiogenesis) adsorbed to the AuNPs is decreased in cancer samples compared to non-cancerous or less malignant cancer samples.

CONCLUSION

The molecular aberrations observed from this study may become new biomarkers for prostate cancer detection. The nanoparticle immunoassay reported here can be used as a convenient and general tool to screen and analyze serum proteins and to discover new biomarkers associated with cancer and other human diseases.

Abstract 4316: Suppression of Sp protein expression with Tolfenamic Acid inhibits oral Squamous Cell Carcinoma

OBJECTIVE: Upregulation of members of the Sp protein family is associated with cell proliferation and metastasis in multiple cancer types. Tolfenamic acid (TA) is a nonsteroidal anti-inflammatory drug shown to inhibit the expression of Sp proteins. We tested the hypothesis that TA inhibits Sp protein expression in human head and neck squamous cell carcinoma lines to suppress cell growth.

METHODS: An oral Squamous cell carcinoma cell line (UMSCC-1) was screened for Sp-1 expression, a known target for Tolfenamic Acid (TA). To assess the effect of TA on UMSCC-1 cells, in vitro cell proliferation assays were performed at 24, 48, 72, 96 and 120Hrs, in order to correlate the cell growth response to different drug concentrations (25, 50, 75 and 100 µM). In parallel, Western blot analyses were use to measure Sp-1 expression after 72hrs of drug treatment. In subsequent experiments, we analyzed the effect of TA and radiation on UMSCC-1 under two conditions. Experiment 1: Tolfenamic acid was added 24 hrs after the cells were seeded, and underwent different doses of radiation (5, 10 or 20 Gy) 24 hrs after drug treatment was started. Experiment 2: 24 hrs after seeding UMSCC-1 cells were exposed to different doses of radiation (5, 10 and 20 Gy) and TA was added 24 hrs post-radiation. Cell growth was measure ATP assays.

RESULTS: Preliminary results confirmed the presence of Sp-1 expression in the head and neck squamous cell carcinoma cell line, UMSCC-1. In vitro growth analysis showed a direct correlation between cell death and TA concentration. Additionally a synergistic effect was observed when using TA and radiation. Sp-1 has been identified as a transcription factor for the production of Survivin, a protein which is known to be overexpressed in most cancer cells and has been directly linked to the radiation-resistant phenomenon. By regulating the expression of SP-1 using tolfenamic acid, we have demonstrated a reduction and/or complete inhibition of the cancer cells capability to produce Survivin, sensitizing them to radiation.

CONCLUSIONS: Our study suggests that TA bears potential in the treatment of oral squamous cell carcinomas as a concomitant agent for traditional chemotherapeutic regimens. In parallel, preliminary data suggest that TA potentiates radiation sensitivity in human head and neck cancer cells. Animal's studies are warranted to further investigate TA in squamous cell carcinoma.

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 4316. doi:10.1158/1538-7445.AM2011-4316

Abstract 619: O6-Benzylguanine inhibits tamoxifen-resistant breast cancer cell growth and resensitizes breast cancer cells to anti-estrogen therapy

Endocrine therapies using anti-estrogens are less toxic and very effective for breast cancers however tumor resistance to tamoxifen remains a stumbling block for successful therapy. Based on our recent study on the involvement of the DNA repair protein MGMT in pancreatic cancer (Clin Cancer Res. 15, 6087, 2009), we investigated whether MGMT overexpression mediates tamoxifen resistance. Specifically, we determined whether administration of MGMT inhibitor [O6-benzylguanine (BG)] at a non-toxic dose alone or in combination with the anti-estrogens (tamoxifen/fulvestrant) curtails human tamoxifen resistant breast cancer cell growth. Furthermore, we also determined whether BG sensitizes breast cancer cells to tamoxifen using tamoxifen resistant cells.

MGMT expression was found to be increased in breast cancer cells relative to normal breast epithelial cells. Also, MGMT levels were significantly higher in tamoxifen resistant MCF-7 compared to the parent cells. Silencing of the ER-α expression using a specific siRNA resulted in augmentation of MGMT mRNA and protein levels by two fold. We also observed an inverse correlation between MGMT and p53 levels in breast cancer cell lines; moreover, p53 downregulation was accompanied by increased MGMT expression. Other experiments showed that BG alone or BG in combination with tamoxifen or fulvestrant decreased ER-α expression, whereas tamoxifen alone and fulvestrant alone increased and decreased the same respectively. All these treatments increased the p21cip1 mRNA and protein expression significantly. BG inhibited tamoxifen resistant breast cancer growth in a dose-dependent manner and it also resensitized resistant breast cancer cells to anti-estrogen therapy (TAM/ICI). These combinations also enhanced the cytochrome C release and PARP cleavage, indicative of apoptosis. In breast cancer xenografts, BG alone or a combination of BG with tamoxifen or fulvestrant caused a significant tumor growth delay and immunohistochemistry revealed that BG inhibited the expression of MGMT, ER- α, ki-67 and increased p21cip1 staining. These findings suggest that MGMT inhibition may provide a novel and effective approach for overcoming tamoxifen resistance (supported by a Florida Biomedical grant to SK).

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 619. doi:10.1158/1538-7445.AM2011-619

Loss of tyrosine phosphatase-dependent inhibition promotes activation of tyrosine kinase c-Src in detached pancreatic cells

Despite an intense focus on novel therapeutic strategies, pancreatic adenocarcinoma remains one of the deadliest human malignancies. The frequent and rapid mortality associated with pancreatic cancer may be attributed to several factors, including late diagnosis, rapid tumor invasion into surrounding tissues, and formation of distant metastases. Both local invasion and metastasis require disruption of tumor cell contacts with the extracellular matrix. Detachment of normal cells from the extracellular matrix leads to a form of programmed cell death termed anoikis. Pancreatic cancer cells avert anoikis by activation of signaling pathways that allow for adhesion-independent survival. In the present studies, cellular signaling pathways activated in detached pancreatic cancer cells were examined. We demonstrate a rapid and robust activation of Src kinase in detached pancreatic cancer cells, relative to adherent. Src autophosphorylation rapidly returned to baseline levels upon reattachment to tissue culture plastic, in the presence or absence of specific extracellular matrix proteins. Treatment of pancreatic cancer cells with tyrosine phosphatase inhibitors increased steady-state Src autophosphorylation in adherent cells and abrogated the detachment-induced increase in Src autophosphorylation. Src was found to co-immunoprecipitate with the Src homology 2 (SH2) domain containing protein tyrosine phosphatase (SHP-2) in pancreatic cancer cells, suggesting that SHP-2 may participate in regulation of Src autophosphorylation in adherent cells. Src family kinase (SFK) dependent increases in Akt and Jun N-terminal kinase (JNK) phosphorylation were observed in detached cells, indicating the potential for Src-dependent activation of survival and stress pathways in pancreatic cancer cells that have detached from the extracellular matrix.

Chemopreventive effects of tolfenamic acid against esophageal tumorigenesis in rats

The primary objective of this study is to identify small molecules that target critical transcription factors for potential application in the chemoprevention of esophageal cancer. Specificity proteins (Sp) play a critical role in the growth and metastasis of several malignancies including esophageal cancer. Researchers at the M. D. Anderson Cancer Center Orlando Cancer Research Institute have reported previously that tolfenamic acid (TA) inhibits cancer cell proliferation and tumor growth through the degradation of Sp1, Sp3, and Sp4. We evaluated the chemopreventive properties of TA against esophageal tumorigenesis in N-nitrosomethylbenzylamine (NMBA)-induced murine tumor model. Fischer-344 rats were treated with NMBA (0.5 mg/kg s.c. 3 times a week) for 5 weeks to initiate the tumor formation, and then treated with 50 mg/kg TA from week 6 through week 25. Tumor incidence, tumor multiplicity (number of papilloma per rat), and tumor volume were evaluated after 25 weeks. All rats in the control group that received only NMBA developed lesions (100% incidence), while the TA-treated group showed significantly lower (33%) tumor incidence and tumor multiplicity. Furthermore, the tumor volume was significantly diminished in the TA-treated group when compared with the control group. Using small molecules such as TA to target key transcription factors associated with tumorigenesis for the prevention of esophageal malignancies is a new and promising strategy. Results of the current study provide evidence that TA, when given orally after tumor initiation, can significantly suppress tumorigenesis induced by carcinogenic nitrosamines in rats. These appealing results demonstrate that TA may potentially serve as an effective chemopreventive agent in patient populations vulnerable to esophageal cancer.

Therapeutic applications of NSAIDS in cancer: special emphasis on tolfenamic acid

Non-steroidal anti-inflammatory drugs (NSAIDs) are primarily used for the treatment of acute or chronic conditions with pain and inflammation. Evidence from a wide range of sources suggested that chronic administration of NSAIDs reduced the risk of cancer incidences. Both the epidemiological and animal studies showed an inverse association between the incidence of various cancers and the use of aspirin or other NSAIDs. The chemopreventive and therapeutic interventions of NSAIDs in cancer are obvious; however, the instigation of drug and treatment period depends on the study objective. Typically, prevention involves initiating the medication before the appearance of clinical symptoms and lasts long-term; while treatment could be short-term and contingent to the response of patient to the medication. Recent studies from our laboratories provided substantial evidence on the anti-cancer activity of tolfenamic acid, a NSAID for the potential applications in pancreatic, esophageal and lung cancers. In this review, we provide a summary on the potential benefits of NSAIDs in a variety of human cancers with more emphasis on tolfenamic acid.

Bioluminescence imaging correlates with tumor progression in an orthotopic mouse model of lung cancer

BACKGROUND AND OBJECTIVES

To determine whether bioluminescence imaging of human lung cancer cells growing in an orthotopic murine model provides a sensitive tool for monitoring tumor progression in athymic nude mice.

METHODS

Human lung cancer (A549) cells were stably transfected with the firefly luciferase gene and inoculated into the right lung of athymic nude mice. Seven days after inoculation tumor growth was evaluated using the Kodak in-vivo Imaging System FX and continued to be monitored on a weekly basis.

RESULTS

In duplicate experiments, human lung cancer tumors formed in 90% of animal's injected orthotopically. The mean intensity of the bioluminescence signal emitted from the lung cancer cells increased logarithmically during the course of study. Mice with positive bioluminescence signaling had confirmed tumors by microscopic histological analysis. Bioluminescence activity had a strong correlation with the tumor volume as determined histologically.

CONCLUSIONS

Bioluminescence intensity directly correlates with tumor volume and therefore offers a reliable approach for detecting and monitoring the growth of human lung cancer cells in orthotopic murine models.

Multicolored redox active upconverter cerium oxide nanoparticle for bio-imaging and therapeutics

Cytocompatible, co-doped cerium oxide nanoparticles exhibited strong upconversion properties that were found to kill lung cancer cells by inducing apoptosis thereby demonstrating the potential to be used as clinical contrast agents for imaging and as therapeutic agents for treatment of cancer.

Probability of Signal Detection in a Vigilance Task

It is hypothesized that the probability of detecting a signal in a vigilance task depends upon its temporal location with respect to the preceding series of signals. Probability of detection should be at a maximum when the signal occurs after a temporal interval which is equivalent to the mean of the intervals between the preceding signals detected. The experimental results support this hypothesis.

Levetiracetam enhances p53-mediated MGMT inhibition and sensitizes glioblastoma cells to temozolomide

Antiepileptic drugs (AEDs) are frequently used to treat seizures in glioma patients. AEDs may have an unrecognized impact in modulating O(6)-methylguanine-DNA methyltransferase (MGMT), a DNA repair protein that has an important role in tumor cell resistance to alkylating agents. We report that levetiracetam (LEV) is the most potent MGMT inhibitor among several AEDs with diverse MGMT regulatory actions. In vitro, when used at concentrations within the human therapeutic range for seizure prophylaxis, LEV decreases MGMT protein and mRNA expression levels. Chromatin immunoprecipitation analysis reveals that LEV enhances p53 binding on the MGMT promoter by recruiting the mSin3A/histone deacetylase 1 (HDAC1) corepressor complex. However, LEV does not exert any MGMT inhibitory activity when the expression of either p53, mSin3A, or HDAC1 is abrogated. LEV inhibits malignant glioma cell proliferation and increases glioma cell sensitivity to the monofunctional alkylating agent temozolomide. In 4 newly diagnosed patients who had 2 craniotomies 7-14 days apart, prior to the initiation of any tumor-specific treatment, samples obtained before and after LEV treatment showed the inhibition of MGMT expression. Our results suggest that the choice of AED in patients with malignant gliomas may have an unrecognized impact in clinical practice and research trial design.

Phosphate ester hydrolysis of biologically relevant molecules by cerium oxide nanoparticles

In an effort to characterize the interaction of cerium oxide nanoparticles (CNPs) in biological systems, we explored the reactivity of CNPs with the phosphate ester bonds of p-nitrophenylphosphate (pNPP), ATP, o-phospho-l-tyrosine, and DNA. The activity of the bond cleavage for pNPP at pH 7 is calculated to be 0.860 ± 0.010 nmol p-nitrophenol/min/μg CNPs. Interestingly, when CNPs bind to plasmid DNA, no cleavage products are detected. While cerium(IV) complexes generally exhibit the ability to break phosphorus-oxygen bonds, the reactions we report appear to be dependent on the availability of cerium(III) sites, not cerium(IV) sites. We investigated the dephosphorylation mechanism from the first principles and find the reaction proceeds through inversion of the phosphate group similar to an S(N)2 mechanism. The ability of CNPs to interact with phosphate ester bonds of biologically relevant molecules has important implications for their use as potential therapeutics.

Abstract 4097: Protein tyrosine phosphatase SHP-2 regulates human pancreatic cancer cell biology on collagen I

With a five year survival rate of less than 5%, pancreatic cancer stands as one of the deadliest human malignancies. There is a great need for novel therapeutic strategies for this illness, and improving our understanding of pancreatic cancer biology will be a key step in developing these therapies. The purpose of these studies is to investigate the regulation and function of the Src Homology 2 (SH2) domain containing protein tyrosine phosphatase SHP-2 in human pancreatic cancer cells and to determine its potential value as a therapeutic target for this disease. In other cellular systems, SHP-2 is crucial for integrin and receptor tyrosine kinase-mediated activation of diverse signaling pathways, regulating many of the cellular events necessary for oncogenesis, including cell division, motility, adhesion, and survival. We hypothesized that inhibition of SHP-2 function would negatively impact integrin-mediated cell signaling and biology in response to the extracellular matrix protein collagen I, an abundant component of pancreatic tumor stroma in vivo. Initial results demonstrate that SHP-2 expression and tyrosine phosphorylation/activity are elevated in pancreatic cancer cells, relative to immortalized normal human pancreatic cells. Phosphorylation of SHP-2 is further elevated in the presence of collagen I. SHP-2 tyrosine phosphorylation in pancreatic cancer cells occurrs in a Src family kinase-dependent fashion. Initial results using miRNA-mediated knock-down of SHP-2 expression indicate the importance of SHP-2 for the ability of pancreatic cancer cells to proliferate, migrate and heal cell culture wounds on collagen I. Additionally, SHP-2 knockdown cells grown on collagen I demonstate altered tyrosine phosphorylation patterns of several signal transduction proteins, including focal adhesion kinase (FAK), in comparison to controls. These data suggest, for the first time, an importance for SHP-2 in pancreatic cancer cell biology and the potential value of SHP-2 as a therapeutic target for this disease. Ongoing and future experiments will compare the effects of SHP-2 inhibition on pancreatic tumor growth in vivo.

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 4097.

Abstract 1561: Guaiacol glyceryl ether, a novel agent to reduce MUC1 expression in breast cancer cells

Purpose: The overexpression and loss of polarity of Mucin1 (MUC1) has been documented in aggressive breast cancer. We have identified guaifenesin as a novel treatment to reduce or eliminate MUC1 expression on human breast cancer cells.

Methods: MCF-7 and ZR-75-1 human breast cancer cells were grown for 48 hours in varying concentrations of guaifenesin to determine if a dose dependent effect on MUC1 protein expression resulted with treatment. In addition, cells were also harvested, RNA isolated, reverse transcribed and PCR was performed using ABI quantitative real time PCR machine. In another set of experiments, MCF-7 cells were plated and grown for 72 hours in the absence or presence of 12.5 mM guaifenesin and the cells were harvested and stained with propidium iodine for analysis by flow cytometry. The Cell-Titer Glo assay was performed on MCF-7 and ZR-75-1 cells incubated for 48 hours in the presence of guaifenesin at varying concentrations and the LD50 was determined. In a final set of experiments, MCF-7 cells, incubated in the presence or absence of guaifenesin, were analyzed for their ability to migrate /proliferate in vitro by using a standard scratch assay. For in vivo studies ovarectomized female nude mice were injected with MCF-7-luciferase tagged cells into the mammary fat pad 24 hours after an estrogen pellet was implanted into the right flank. Treatment (vehicle or 400 mg/kg/daily) was initiated after 10 days and tumor growth was monitored through Kodak imaging system. Six weeks after the treatment tumors were isolated, measured and processed for immunohistochemistry to analyze the expression of MUC1, TUNEL and CD31.

Results: Initially, MUC1 gene expression was confirmed in MCF-7 and ZR-75-1 human breast cancer cell lines. Following confirmation, the LD50 was determined to be 12.5 mM. MUC1 gene expression was successfully decreased in a dose-dependent manner in both MCF-7 and ZR-75-1 cell lines when treated with guaifenesin. When MCF-7 cells are treated with 12.5mM guaifenesin, G1 arrest occurs within 24 hours and by 72 hours, 94.2% of cells are in G1 compared to 76.2% in control (drug free) conditions. In addition, there was a significant decrease in the ability of guaifenesin treated MCF-7 cells to migrate into the scratch compared to the control (untreated) cells. In vivo studies revealed that guaifenesin significantly decreased the breast tumor weight and volume which was associated with a low expression of MUC1 in tumor sections as evaluated by immunohistochemistry.

Conclusion: These findings suggest that guaifenesin may provide a novel approach to inhibit breast cancer growth.

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 1561.

Abstract 1618: Tolfenamic Acid Inhibits Ovarian Cancer Cells Growth and Decreases the Expression of c-Met and Survivin Through Suppressing the Transcription Factors Sp1 and Sp3

The aberrant expression of hepatocyte growth factor (HGF) and its receptor c-Met are associated with poor prognosis in a variety of human malignancies including ovarian cancer. Survivin, which belongs to inhibitor of apoptosis gene family, plays an important role in ovarian tumor resistance to chemo- and radiotherapy. Specificity protein (Sp) transcription factors regulate the expression of c-Met and survivin. We have previously shown that the non-steroidal anti-inflammatory drug, Tolfenamic acid (TA), induces the degradation of Sp proteins in cancer cells and tumors. Our aim was to explore the anti-ovarian cancer activity of TA in an in vitro model, as preliminary screening to investigate the therapeutic applications of this small molecule. We developed three ovarian cancer cell-lines, (SKOV3-AF1, SKOV3-AF2, and SKOV3-AF3) which express red fluorescent protein (RFP), derived from the original SKOV-3 line. The AF1 and AF2 lines are more resistant to IFNα-2b and are more tumorigenic in nude mice than the parental SKOV-3 cells. The inhibitory effects of TA on ovarian cancer cells were tested using SKOV-3-derived cells. Cells were grown in the presence of DMSO (vehicle) or TA at increasing concentrations (25, 50 and 100 µM) and cell viability assay was performed using the Cell Titr Glo kit (Promega) at 24, 48, and 72 h, post-treatment. Cell lysates were prepared from cells exposed to DMSO or 50 µM TA for 48 h and the expression of Sp proteins (Sp1 and Sp3), c-Met and survivin was analyzed using Western blot analysis. SKOV-3-derived cells showed marked inhibition with TA treatment and this effect was dose and time dependent. At the maximal dose (100 µM), TA treatment showed significant inhibitory response (RFP:67%; AF1:96%;AF2:88%; AF3:92%) at 48 h post-treatment, while the response at 50 µM TA was 30-60% (RFP:34%; AF1:58%; AF2:59%; AF3:60%). TA-induced cell proliferation arrest was associated with the decreased expression of Sp1, Sp3, c-Met and survivin. These data clearly suggest that TA has a profound inhibitory effect on ovarian cancer cell proliferation, presumably through the degradation of Sp proteins. These studies also suggest that targeting c-Met through Sp proteins degradation could be a promising strategy in the therapeutic applications for ovarian cancer. In addition to its tumor suppressant effects, TA can also enhances tumor response to chemo- and/or radiotherapy due to its inhibitory actions on survivin expression. Using small molecules like TA to target key transcription factors associated with ovarian cancer growth and progression can be a promising treatment approach. TA is currently in Phase I clinical trial at M. D. Anderson Cancer Center Orlando to test on upper GI cancer patients.

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 1618.

Abstract 3463: Chemopreventive effect of tolfenamic acid against esophageal tumorigenesis in rats

Specificity proteins (Sp) play a critical role in the growth and metastasis of several malignancies including esophageal cancer and Sp1 expression is a negative prognostic factor in cancer patients. We have reported previously that tolfenamic acid (TA) inhibits cancer cells proliferation and tumor growth through degradation of Sp1, Sp3 and Sp4. Interestingly TA also significantly inhibited the proto-oncogene c-Met. In the current study the efficacy of TA for prevention of esophageal tumorigenesis in N-nitrosomethylbenzylamine (NMBA)-induced murine tumor model is evaluated.

A well established chemically-induced esophageal tumor model is used in the current studies where Fisher-344 rats were treated with NMBA (0.5 mg/kg s.c.) three times a week for 5 weeks. Two groups of rats received TA (50 mg/kg by oral gavage) three times a week either concurrently with (Weeks 1- 25) or sequentially after (Weeks 6-25) NMBA treatment. Tumor incidence, Tumor multiplicity (number of papilloma per animal) and tumor volume were compared after 25 weeks.

All the rats in the control group which received only NMBA developed tumor lesions. Tumor lesions in the oesophagi were seen as irregular, multiple, exophytic swellings arising from esophageal epithelium, mostly ovoid in shape and oriented along the axis of esophagus. No ulceration was noted in any part of the esophagus. Most of the abnormal oesophagi showed hyperkeratosis and papilloma. TA treated (sequential and concurrent exposure) groups showed significantly lower tumor incidence (33%) and tumor multiplicity when compared to control; however the concurrent TA-exposure group showed the least number of papilloma per rat. Furthermore, the tumor volume was significantly diminished in concurrent TA-exposure group when compared with other control and treatment groups.

Using small molecules such as TA to target key transcription factors associated with tumorigenesis and angiogenesis for the prevention of esophageal malignancies is a new and promising strategy and results of the current study provide evidence that TA when give orally at the time of tumor initiation, promotion and progression can significantly suppress tumorigenesis induced by carcinogenic nitrosamines in rats. Since nitrosamines such as NMBA have been isolated in human gastric juice and often implicated as a causative agent in human esophageal cancer, TA may serve as an effective chemopreventive agent in patient populations vulnerable to esophageal cancer. Seeking in depth knowledge of the molecular mechanisms underlying this beneficial effect of TA, further studies are being carried out presently at our laboratory. Benefits of such exploration are well-warranted to understand better this molecular pathway-targeted prevention of esophageal 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 3463.

Angiogenesis: an update and potential drug approaches (review)

The therapeutic potential of targeting tumor endothelium and vascular supply is now widely recognized to treat different diseases. One such disease is cancer; where endothelial cells are actively proliferating to support the tumor growth. Solid tumors cannot grow beyond the size of a few millimeters without inducing the proliferation of endothelium and formation of new blood vessels. Hence it is crucial to search for new agents that selectively block tumor blood supply. These include anti-angiogenic molecules, vascular disrupting agents or endothelial disrupting agents. The anti-angiogenic molecules such as monoclonal antibodies and tyrosine kinase inhibitors disrupt endothelial cell survival mechanisms and new blood vessel formation, and vascular disrupting agents for instance ligand-directed and small molecules can be used to disrupt the already existing abnormal vasculature that support tumors by targeting their dysmorphic endothelial cells. The recent advances in this area of research have identified a variety of investigational agents which are currently in clinical development at various stages and some of these candidates are already approved in cancer treatment. This report will review some of the recent developments and most significant advances in this field and outline future challenges and directions.

Tolfenamic acid decreases c-Met expression through Sp proteins degradation and inhibits lung cancer cells growth and tumor formation in orthotopic mice

The nonsteroidal anti-inflammatory drug (NSAID), tolfenamic acid (TA) is emerging as a new anti-cancer agent. TA induces the degradation of specific Specificity protein (Sp) transcription factors, Sp1, Sp3 and Sp4 which are associated with tumor growth and metastasis. In this study we have evaluated the effect of TA on lung cancer using both in vitro and in vivo models. TA in a dose dependent manner inhibited proliferation and cell viability of two different lung cancer cells, A549 and CRL5803. TA treatment for 48 h significantly decreased the expression of Sp1, Sp3 and Sp4. The hepatocyte growth factor receptor, c-Met is overexpressed in a variety of cancers including lung cancer and Sp proteins mediate the regulation of c-Met. TA diminished the expression of c-Met protein and modulates its downstream signaling pathway. Furthermore, TA treatment significantly increased the number of apoptotic cells and pro-apoptotic markers c-PARP and Bax confirming the activation of apoptotic pathways. In vivo studies using the orthotopic mice model for lung cancer showed that TA (25 mg/kg/2 days and 50 mg/kg/2 days) resulted in a dose dependent decrease in tumor formation. The immunohistochemical staining of lung tissue showed high expression of Sp1, Sp3, Sp4, c-Met and phospho Met in control group and a dose dependent decrease in TA treated groups. The crucial findings of this study support that targeting c-Met with a potent inhibitor of Sp proteins is a robust strategy for the implications in lung cancer treatment and TA can serve as a therapeutic agent for this devastating disease.

Blockade of MGMT expression by O6 benzyl guanine leads to inhibition of pancreatic cancer growth and induction of apoptosis

PURPOSE

We sought to determine whether administration of a MGMT blocker, O(6)-benzyl guanine (O(6)BG), at an optimal biological dose alone or in combination with gemcitabine inhibits human pancreatic cancer cell growth.

EXPERIMENTAL DESIGN

Human pancreatic cancer L3.6pl and PANC1 cells were treated with O(6)BG, either alone or in combination with gemcitabine, and the therapeutic efficacy and biological activity of these drug combinations were investigated.

RESULTS

O(6)BG sensitized pancreatic cancer cells to gemcitabine. Protein and mRNA expression of MGMT, cyclin B1, cyclin B2, cyclin A, and ki-67 were significantly decreased in the presence of O(6)BG. In sharp contrast, protein expression and mRNA message of p21(cip1) were significantly increased. Interestingly, O(6)BG increases p53-mediated p21(cip1) transcriptional activity and suppresses cyclin B1. In addition, our results indicate that p53 is recruited to p21 promoter. Furthermore, an increase in p21(cip1) and a decrease in cyclin transcription are p53 dependent. The volume of pancreatic tumors was reduced by 27% in mice treated with gemcitabine alone, by 47% in those treated with O(6)BG alone, and by 65% in those mice given combination. Immunohistochemical analysis showed that O(6)BG inhibited expression of MGMT and cyclins, and increased expression of p21(cip1). Furthermore, there was a significant decrease in tumor cell proliferation and an increase in tumor cell apoptosis.

CONCLUSIONS

Collectively, our results show that decreased MGMT expression is correlated with p53 activation, and significantly reduced primary pancreatic tumor growth. These findings suggest that O(6)BG either alone or in combination with gemcitabine may provide a novel and effective approach for the treatment of human pancreatic cancer.

A metastatic colon cancer model using nonoperative transanal rectal injection

BACKGROUND

This study aimed to develop a noninvasive orthotopic model for metastasis of colon and rectal cancer using a transanal approach. Currently, the most accurate orthotopic representation of metastatic human colon cancer is via a cecal injection. The transanal model allows for further examination of systemic immune responses, tumor take, and onset of metastasis without prior surgical intervention.

METHODS

For this study, 60 Balb/c mice were anesthetized and subjected to gentle anal dilation using blunt-tipped forceps at the anal opening. Murine colon cancer parental CT26 or luciferase-labeled CT26 (CT26-luc) cells were injected submucosally into the distal posterior rectum (30 CT26 and 30 CT26 injections) at concentrations of 2.5 x 10(4), 1 x 10(5), and 1 x 10(6) in a volume of 50 microl. Tumor growth and metastatic development was monitored at 5-day intervals for 50 days. All the remaining mice were killed on postinjection day 50.

RESULTS

The optimal concentration for metastasis and survival of the mice was 2.5 x 10(4) cells. Higher concentrations of cells yielded higher mortality but did not result in metastasis. The overall success of tumor growth in both experiments using the transanal rectal injection was 65%. Histology showed that all tumors were poorly differentiated adenocarcinomas. Two mice (3.3%) from the 2.5 x 10(4) CT26-luc group showed metastatic colonic adenocarcinoma to the liver on postinjection day 50.

CONCLUSION

Transanal rectal injection of colon cancer cells offers a nonoperative orthotopic murine model for colon cancer that may lead to the development of metastasis. By using an orthotopic model, more aspects of metastatic colon cancer can be evaluated without the influence of a previous abdominal incision. These results warrant more investigation.

Tissue factor-bearing microparticles derived from tumor cells: impact on coagulation activation

BACKGROUND

Tissue factor (TF)-bearing microparticles (MP) from different origins are thought to be involved in the pathogenesis of cancer-associated thrombosis. However, the role of circulating tumor cell-derived TF is not well understood.

METHODS

TF antigen and activity were measured in MP generated in vitro from human TF-expressing cancer cells by ELISA and clotting or thrombin generation assays, respectively. TF antigen and activity were also measured in vivo in cell-free plasmas from mice previously injected with in vitro-generated MP or in cell-free plasmas from nude mice bearing orthotopically injected human cancer cells.

RESULTS

Tumor cell-derived MP (TMP) exhibited strong TF-dependent procoagulant activity (PCA) in vitro and in vivo. Injection of TMP into mice was associated with acute thrombocytopenia and signs of shock, which were prevented by prior heparinization. Human TF antigen and activity could be detected in mouse cell-free plasmas up to 30 min after TMP injections. Human TF was detected in the spleen of injected mice and its clearance from circulation was delayed in splenectomized mice, suggesting the involvement of the spleen in the rapid clearance of circulating MP in vivo. Detectable levels of TF-dependent PCA and thrombin-antithrombin complex were found in cell-free plasmas from mice growing pancreatic human tumors, suggesting that circulating tumor-derived TF causes coagulation activation in vivo.

CONCLUSIONS

MP derived from certain cancer cells exhibit TF-dependent PCA both in vitro and in vivo. These results provide new information about the specific contribution of tumor-derived MP to the hypercoagulable state observed in cancer.

Bcl-B expression in human epithelial and nonepithelial malignancies

PURPOSE

Apoptosis plays an important role in neoplastic processes. Bcl-B is an antiapoptotic Bcl-2 family member, which is known to change its phenotype upon binding to Nur77/TR3. The expression pattern of this protein in human malignancies has not been reported.

EXPERIMENTAL DESIGN

We investigated Bcl-B expression in normal human tissues and several types of human epithelial and nonepithelial malignancy by immunohistochemistry, correlating results with tumor stage, histologic grade, and patient survival.

RESULTS

Bcl-B protein was strongly expressed in all normal plasma cells but found in only 18% of multiple myelomas (n = 133). Bcl-B immunostaining was also present in normal germinal center centroblasts and centrocytes and in approximately half of diffuse large B-cell lymphoma (n = 48) specimens, whereas follicular lymphomas (n = 57) did not contain Bcl-B. In breast (n = 119), prostate (n = 66), gastric (n = 180), and colorectal (n = 106) adenocarcinomas, as well as in non-small cell lung cancers (n = 82), tumor-specific overexpression of Bcl-B was observed. Bcl-B expression was associated with variables of poor prognosis, such as high tumor grade in breast cancer (P = 0.009), microsatellite stability (P = 0.0002), and left-sided anatomic location (P = 0.02) of colorectal cancers, as well as with greater incidence of death from prostate cancer (P = 0.005) and shorter survival of patients with small cell lung cancer (P = 0.009). Conversely, although overexpressed in many gastric cancers, Bcl-B tended to correlate with better outcome (P = 0.01) and more differentiated tumor histology (P < 0.0001).

CONCLUSIONS

Tumor-specific alterations in Bcl-B expression may define subsets of nonepithelial and epithelial neoplasms with distinct clinical behaviors.

Successful inhibition of intracranial human glioblastoma multiforme xenograft growth via systemic adenoviral delivery of soluble endostatin and soluble vascular endothelial growth factor receptor-2: laboratory investigation

OBJECT

Glioblastoma multiforme (GBM) is characterized by neovascularization, raising the question of whether angiogenic blockade may be a useful therapeutic strategy for this disease. It has been suggested, however, that, to be useful, angiogenic blockade must be persistent and at levels sufficient to overcome proangiogenic signals from tumor cells. In this report, the authors tested the hypothesis that sustained high concentrations of 2 different antiangiogenic proteins, delivered using a systemic gene therapy strategy, could inhibit the growth of established intracranial U87 human GBM xenografts in nude mice.

METHODS

Mice harboring established U87 intracranial tumors received intravenous injections of adenoviral vectors encoding either the extracellular domain of vascular endothelial growth factor receptor-2-Fc fusion protein (Ad-VEGFR2-Fc) alone, soluble endostatin (Ad-ES) alone, a combination of Ad-VEGFR2-Fc and Ad-ES, or immunoglobulin 1-Fc (Ad-Fc) as a control.

RESULTS

Three weeks after treatment, magnetic resonance imaging-based determination of tumor volume showed that treatment with Ad-VEGFR2-Fc, Ad-ES, or Ad-VEGFR2-Fc in combination with Ad-ES, produced 69, 59, and 74% growth inhibition, respectively. Bioluminescent monitoring of tumor growth revealed growth inhibition in the same treatment groups to be 62, 74, and 72%, respectively. Staining with proliferating cell nuclear antigen and with terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling showed reduced tumor cell proliferation and increased apoptosis in all antiangiogenic treatment groups.

CONCLUSIONS

These results suggest that systemic delivery and sustained production of endostatin and soluble VEGFR2 can slow intracranial glial tumor growth by both reducing cell proliferation and increasing tumor apoptosis. This work adds further support to the concept of using antiangiogenesis therapy for intracranial GBM.

Novel murine model for colon cancer: non-operative trans-anal rectal injection

BACKGROUND

This study was conducted to develop a modified murine model of colon cancer that is non-operative. Currently, the most accurate orthotopic murine model of colon cancer requires an invasive procedure involving cecal injection of colon cancer cells and therefore limits the ability to perform immunological studies subsequent to cecal resections.

MATERIALS AND METHODS

Murine colon cancer (CT26) cells were injected submucosally into the distal, posterior rectum of BALB/c mice. Care was taken not to pass transmurally into the pelvic cavity. Different magnifications (10x versus 100x) were used for injection, and primary tumor growth and metastatic disease were studied.

RESULTS

In the initial study, 3/7 mice injected using 10x magnifications had notable, large tumor originating from the rectal wall, and histology revealed that all excised tumors were poorly differentiated adenocarcinoma. In the second study, 8/10 mice injected using 100x magnifications had notable tumor originating from the rectal well, and 4/8 mice had abnormal lung tissue with pathological evidence of hemorrhagic pulmonary edema. The use of 10x magnification resulted in 43% tumor take. In sharp contrast, 80% tumor take was observed with 100x magnification. The overall success of tumor take was 65% using the trans-anal rectal injection model.

CONCLUSIONS

Our modified orthotopic murine model of colon cancer offers an alternative non-operative murine model for colon cancer and is less invasive than the traditional orthotopic model (i.e., cecal injection). This model may allow for more accurate investigations of inflammation and immune responses to surgical intervention without the influence of previous abdominal surgery.

Expression of epidermal growth factor (EGF)/transforming growth factor-alpha by human lung cancer cells determines their response to EGF receptor tyrosine kinase inhibition in the lungs of mice

Epidermal growth factor receptor (EGFR) has been extensively targeted in the treatment of non-small cell lung cancer, producing responses in a small number of patients. To study the role of ligand expression in mediating response to EGFR antagonism, we injected NCI-H441 [EGFR and EGF/transforming growth factor-alpha (TGF-alpha) positive] or PC14-PE6 (EGFR positive and EGF/TGF-alpha negative) human lung adenocarcinoma cells into the lungs of nude mice. We randomized the mice to receive treatment with the EGFR tyrosine kinase inhibitors gefitinib or AEE788 or vehicle. Treatment of mice bearing NCI-H441 but not PC14-PE6 lung tumors resulted in a significant reduction in primary tumor growth, pleural effusion, and lymph node metastasis. Immunohistochemical analyses revealed that NCI-H441 and PC14-PE6 cells expressed EGFR but that the expression of EGF/TGF-alpha was high in NCI-H441 cells and very low in PC14-PE6 cells. Consequently, EGFR was activated in both tumor and tumor-associated endothelial cells in the NCI-H441 tumors but not in the PC14-PE6 tumors. Antagonism of EGFR signaling by treatment of mice with AEE788 decreased proliferation and increased apoptosis of both tumor cells and tumor-associated endothelial cells in NCI-H441 tumors but not in PC14-PE6 tumors. However, after transfection of PC14-PE6 cells with TGF-alpha, lung tumors derived from the transfected cells expressed and activated EGFR in both tumor and tumor-associated endothelial cells and tumors responded to treatment with AEE788. Collectively, these results strongly suggest that the response of human lung cancers growing orthotopically in mice to the inhibition of EGFR signaling is determined by ligand (EGF/TGF-alpha) expression by tumor cells. Our findings provide an additional explanation for the susceptibility of lung cancers to treatment with EGFR tyrosine kinase inhibitors.

Regulation of vascular endothelial growth factor receptor-1 expression by specificity proteins 1, 3, and 4 in pancreatic cancer cells

Vascular endothelial growth factor receptor-1 (VEGFR1) is expressed in cancer cell lines and tumors and, in pancreatic and colon cancer cells, activation of VEGFR1 is linked to increased tumor migration and invasiveness. Tolfenamic acid, a nonsteroidal anti-inflammatory drug, decreases Sp protein expression in Panc-1 and L3.6pl pancreatic cancer cells, and this was accompanied by decreased VEGFR1 protein and mRNA and decreased luciferase activity on cells transfected with constructs (pVEGFR1) containing VEGFR1 promoter inserts. Comparable results were obtained in pancreatic cancer cells transfected with small inhibitory RNAs for Sp1, Sp3, and Sp4 and all three proteins bound to GC-rich elements in the VEGFR1 promoter. These results show that VEGFR1 is regulated by Sp proteins and that treatment with tolfenamic acid decreases expression of this critical angiogenic factor. Moreover, in vitro studies in Panc-1 cells show that activation of VEGFR1 by VEGFB to increase mitogen-activated protein kinase 1/2 phosphorylation and cell migration on collagen-coated plates is also inhibited by tolfenamic acid. Thus, targeted degradation of Sp proteins is highly effective for inhibiting VEGFR1 and associated angiogenic responses in pancreatic cancer.

Phosphorylated epidermal growth factor receptor on tumor-associated endothelial cells in human renal cell carcinoma is a primary target for therapy by tyrosine kinase inhibitors

We determined whether therapy for human renal cell carcinoma (HRCC) that grows in the kidney of nude mice by the specific epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor, PKI166, is directed against phosphorylated EGFR on tumor cells or on tumor-associated endothelial cells. EGFR+/transforming growth factor alpha (TGF-alpha)- SN12-PM6 HRCC cells were transfected with full-length sense TGF-alpha cDNA or vector control. SN12-PM6 cells expressing low or high levels of TGF-alpha were implanted into the kidney of nude mice. Only tumors produced by TGF-alpha+ HRCC cells contained tumor-associated endothelial cells expressing activated EGFR. Oral administration of PKI166 produced significant therapy only in TGF-alpha+ tumors, which correlated with apoptosis of tumor-associated endothelial cells. These data suggest that the production of TGF-alpha by HRCC cells leads to the activation of EGFR on tumor-associated endothelial cells that serve as an essential target for therapy with tyrosine kinase inhibitors.

Inhibition of PDGFR phosphorylation and Src and Akt activity by GN963 leads to therapy of human pancreatic cancer growing orthotopically in nude mice

GN963 is a tyrosine kinase inhibitor with activity against platelet-derived growth factor receptor (PDGFR) and Src kinases. We determined whether oral administration of GN963, alone or in combination with gemcitabine produces therapy against L3.6pl human pancreatic cancer cells growing orthotopically in nude mice. The optimal biological dosage of oral GN963 was determined to be 100 mg/kg every 48 h. Seven days after injection of L3.6pl cells into the pancreas of nude mice, mice (n=10) were treated with vehicle (control), thrice-weekly oral GN963 (100 mg/kg), twice-weekly intraperitoneal gemcitabine (100 mg/kg), or GN963 plus gemcitabine. Treatment with gemcitabine did not significantly differ from control. In contrast, treatment with GN963 (100 mg/kg) or GN963 plus gemcitabine produced a 52% and 81% decrease in tumor volume, respectively. GN963 plus gemcitabine completely inhibited the incidence of liver metastasis. Administration of GN963 inhibited PDGFR phosphorylation in both tumor and tumor-associated endothelial cells, decreased Src and Akt kinase activity in tumor cells, decreased microvessel density, and decreased tumor cell proliferation, while increasing apoptosis of tumor and tumor-associated endothelial cells. Collectively, these data indicate that targeting PDGFR, Src, and Akt on tumor and tumor-associated endothelial cells may be an effective therapy for human pancreatic carcinoma.

Tolfenamic acid and pancreatic cancer growth, angiogenesis, and Sp protein degradation

BACKGROUND

Sp1, Sp3, and Sp4 are transcription factors that regulate cell proliferation and vascular endothelial growth factor (VEGF) expression and are overexpressed in many cancer cell lines. For some cancers, Sp1 overexpression is associated with poor survival. Cyclooxygenase inhibitors decrease Sp1 expression in cancer cells, and therefore different structural classes of nonsteroidal anti-inflammatory drugs (NSAIDs) were screened for their ability to decrease levels of Sp1, Sp3, and Sp4 and to decrease pancreatic tumor growth and metastasis in an in vivo model.

METHODS

Levels of Sp1, Sp3, Sp4, and VEGF proteins in pancreatic cancer cell lines were assessed by immunoblot analysis. mRNA was assessed by reverse transcription-polymerase chain reaction. Panc-1 pancreatic cancer cells transfected with VEGF promoter constructs were used to assess VEGF promoter activation. Pancreatic tumor weight and size and liver metastasis were assessed in an orthotopic mouse model of pancreatic cancer (groups of 10 mice). Protein expression in tumors was assessed immunohistochemically.

RESULTS

Tolfenamic acid and structurally related biaryl derivatives induced degradation of Sp1, Sp3, and Sp4 in pancreatic cancer cells. Tolfenamic acid also inhibited VEGF mRNA and protein expression in pancreatic cancer cells; this inhibition was associated with the decreased Sp-dependent activation of the VEGF promoter. In the mouse model for pancreatic cancer, treatment with tolfenamic acid (50 mg/kg of body weight), compared with control treatment, statistically significantly decreased tumor growth and weight (P = .005), liver metastasis (P = .027), and levels of Sp3 and VEGF (P = .009) and Sp1 and Sp4 (P = .006) proteins in tumors. For example, tumors from mice treated with tolfenamic acid (50 mg/kg) had statistically significantly lower VEGF levels (45%, 95% confidence interval = 39% to 51%; P = .009) than tumors from control mice.

CONCLUSIONS

Tolfenamic acid is a new antipancreatic cancer NSAID that activates degradation of transcription factors Sp1, Sp3, and Sp4; reduces VEGF expression; and decreases tumor growth and metastasis.

Transforming growth factor alpha expression drives constitutive epidermal growth factor receptor pathway activation and sensitivity to gefitinib (Iressa) in human pancreatic cancer cell lines

The epidermal growth factor receptor (EGFR) is considered an important therapeutic target in pancreatic cancer, but it is currently impossible to identify those patients who are most likely to benefit from EGFR-directed therapy. We examined the biological effects of the EGFR tyrosine kinase inhibitor gefitinib (ZD1839, Iressa) in a panel of nine human pancreatic cancer cell lines. The drug strongly inhibited DNA synthesis and induced low levels of apoptosis at clinically relevant concentrations in a subset of three of the lines (L3.6pl, BxPC3, and Cfpac1). Sensitivity to gefitinib correlated directly with ligand [transforming growth factor-alpha (TGF-alpha)] expression (r(2) = 0.71, P = 0.004) but not with surface EGFR expression. The gefitinib-sensitive cells displayed constitutive baseline EGFR phosphorylation, whereas the gefitinib-resistant cells did not. Exposure to gefitinib or a small interfering RNA construct specific for TGF-alpha reversed the constitutive EGFR phosphorylation and downstream target [extracellular signal-regulated kinases (ERK), AKT] phosphorylation in the gefitinib-sensitive cells but had no effects on ERK or AKT phosphorylation in gefitinib-resistant cells. Baseline EGFR phosphorylation was lower in a subclone of L3.6pl selected for low TGF-alpha expression, and these cells were also resistant to gefitinib-mediated growth inhibition. Gefitinib blocked the growth of tumor xenografts derived from L3.6pl cells but had no effect on the growth of tumors derived from EGFR-independent MiaPaCa-2 cells. Together, our data show that TGF-alpha expression identifies a subset of human pancreatic cancer cells that is dependent on EGFR signaling in vitro and in vivo. Quantification of TGF-alpha expression may therefore represent an effective means of identifying EGFR-responsive primary tumors.

Inhibition of SRC expression and activity inhibits tumor progression and metastasis of human pancreatic adenocarcinoma cells in an orthotopic nude mouse model

The nonreceptor protein tyrosine kinase Src is overexpressed in 70% of pancreatic adenocarcinomas. Here, we describe the effect of molecular and pharmacological down-regulation of Src on incidence, growth, and metastasis of pancreatic tumor cells in an orthotopic model. Src expression in L3.6pl human pancreatic tumor cells was reduced by stable expression of a plasmid encoding small interfering RNA (siRNA) to c-src. In stable siRNA clones, Src expression was reduced >80%, with no change in expression of the related kinases c-Yes and c-Lyn, and proliferation rates were similar in all clones. Phosphorylation of Akt and p44/42 Erk mitogen-activated protein kinase and production of VEGF and IL-8 in culture supernatants were also reduced (P < 0.005). On orthotopic implantation of varying cell numbers into nude mice, tumor incidence was unchanged; however, in the siRNA clones, large tumors failed to develop, and incidence of metastasis was significantly reduced, suggesting that c-Src activity is critical to tumor progression. To examine this possibility further, animals bearing established wild-type tumors were treated with the Src/Abl-selective inhibitor BMS-354825 (dasatinib). Tumor size was decreased, and incidence of metastases was significantly reduced in treated mice compared with controls. These results demonstrate that Src activation contributes to pancreatic tumor progression in this model, offering Src as a candidate for targeted therapy.

AP23846, a novel and highly potent Src family kinase inhibitor, reduces vascular endothelial growth factor and interleukin-8 expression in human solid tumor cell lines and abrogates downstream angiogenic processes

c-Src is frequently activated in human malignancies, including colon, breast, and pancreatic carcinomas. Several recent studies have shown that activation of Src family kinases leads to tumor progression and metastasis by increasing cellular migration and invasion, promoting cell growth and survival, and deregulating expression of proangiogenic molecules. Therefore, selective inhibitors of Src are being developed for cancer therapy. In this study, we characterize the biological effects of the novel ATP-based Src family kinase inhibitor, AP23846, in tumor cells with high Src activity. As a lead compound, AP23846 is a potent c-Src kinase inhibitor (IC50 approximately 0.5 nmol/L in vitro, approximately 10-fold more potent than PP2, the most widely used commercially available Src family kinase inhibitor). At concentrations of 1 micromol/L, AP23846 led to complete Src inhibition for 48 hours in cells. No cytotoxicity was observed under these conditions, although proliferation rates were slower. Therefore, this was an excellent inhibitor to examine Src-regulated signaling pathways in tumor cells. AP23846 reduced cellular migration, vascular endothelial growth factor, and interleukin-8 in a dose-dependent fashion in pancreatic adenocarcinoma cells grown in vitro. Correspondingly, cell culture supernatants from L3.6pl pancreatic adenocarcinoma cells pretreated with AP23846 failed to promote migration of hepatic endothelial cells in vitro and failed to support angiogenesis into gel foams implanted s.c. in mice in vivo. These results suggest that Src inhibitors affect biological properties of tumor progression and may be useful as cancer therapeutic agents in more advanced disease.

Noninvasive Bioluminescence Imaging of Luciferase Expressing Intracranial U87 Xenografts: Correlation with Magnetic Resonance Imaging Determined Tumor Volume and Longitudinal Use in Assessing Tumor Growth and Antiangiogenic Treatment Effect

OBJECTIVE

Outcome studies in rodent tumor models rely on both histological and noninvasive study end points. Intracranial models require special tools to observe tumor growth over time noninvasively, such as magnetic resonance imaging (MRI), computed tomographic scanning, or cranial window techniques. These techniques share disadvantages in terms of cost, technical expertise required, and overall animal throughput for analysis. In this report, we sought to validate the use of the relatively newer technique of bioluminescence imaging (BLI) of intracranial glioblastoma xenograft growth by comparing it with gadolinium-enhanced MRI.

METHODS

U87MG glioma cell lines genetically engineered to express the firefly luciferase gene were stereotactically injected into nude mice in the left frontal lobe. Weekly BLI and MRI were performed after the inoculation of tumor cells. For BLI, tumor growth was assessed as the peak BLI after systemic injection of luciferin substrate. MRI-based growth curves were created by three-dimensional volumetric reconstruction of axial gadolinium-enhanced MRI data covering the whole brain. In a separate experiment, mice were treated with adenoviruses encoding antiangiogenic soluble vascular endothelial growth factor receptors, and treatment effect was monitored by BLI.

RESULTS

Untreated tumor growth was readily detected and observed over time by serial BLI measurements. Furthermore, tumor-derived light emission was highly correlated with volume of tumor as assessed by MRI. Furthermore, the tested antiangiogenic treatment effect was readily detected using this technique, suggesting the power of the technique for sensitive monitoring of novel therapeutics.

CONCLUSION

BLI offers a simple and rapid technique for assessing intracranial glioblastoma growth in rodent models noninvasively, which correlates well with MRI. The speed of the BLI technique can increase experimental throughput, allows for targeted histological analysis in animals showing the greatest treatment effects, and provides new insights into the kinetics of intracranial tumor growth in the setting of different treatments.

Simultaneous inhibition of EGFR, VEGFR, and platelet-derived growth factor receptor signaling combined with gemcitabine produces therapy of human pancreatic carcinoma and prolongs survival in an orthotopic nude mouse model

Although gemcitabine has been approved as the first-line chemotherapeutic reagent for pancreatic cancer, its response rate is low and average survival duration is still only marginal. Because epidermal growth factor receptor (EGFR), vascular endothelial growth factor receptor (VEGFR), and platelet-derived growth factor receptor (PDGFR) modulate tumor progression, we hypothesized that inhibition of phosphorylation of all three on tumor cells, tumor-associated endothelial cells, and stroma cells would improve the treatment efficacy of gemcitabine in an orthotopic pancreatic tumor model in nude mice and prolong survival. We implanted L3.6pl, a human pancreatic cancer cell, in the pancreas of nude mice. We found that tumor-associated endothelial cells in this model highly expressed phosphorylated EGFR, VEGFR, and PDGFR. Oral administration of AEE788, a dual tyrosine kinase inhibitor against EGFR and VEGFR, decreased phosphorylation of EGFR and VEGFR. PDGFR phosphorylation was inhibited by STI571. Although i.p. injection of gemcitabine did not inhibit tumor growth, its combination with AEE788 and STI571 produced >80% inhibition of tumor growth and prolonged survival in parallel with increases in number of tumor cells and tumor-associated endothelial cell apoptosis, decreased microvascular density, decreased proliferation rate, and prolonged survival. STI571 treatment also decreased pericyte coverage on tumor-associated endothelial cells. Thus, inhibiting phosphorylation of EGFR, VEGFR, and PDGFR in combination with gemcitabine enhanced the efficacy of gemcitabine, resulting in inhibition of experimental human pancreatic cancer growth and significant prolongation of survival.

Expression and activity of SRC regulate interleukin-8 expression in pancreatic adenocarcinoma cells: implications for angiogenesis

Interleukin-8 (IL-8) is an angiogenic factor that promotes growth of pancreatic tumors. The purpose of this study was to determine if c-Src, a protein tyrosine kinase frequently overexpressed in pancreatic cancer, regulated IL-8 expression and to elucidate the Src-mediated signaling pathways that contribute to angiogenesis in pancreatic adenocarcinoma cells. In a panel of pancreatic cancer cell lines, expression of total and activated Src correlated with IL-8 production. Furthermore, ectopic expression of activated Src in PANC-1 cells with low endogenous Src activity significantly increased IL-8 production (P < 0.005). In contrast, pharmacologic inhibition of endogenous c-Src kinase activity or small interfering RNA-mediated "knockdown" of c-Src expression in L3.6pl cells with high Src expression and activity caused significant decreases in IL-8 production (P < 0.005). Inhibition of c-Src activity resulted in decreased phosphorylation of Akt, p38, and extracellular signal-regulated kinase (Erk)-1/2. Significant (P < 0.005) dose-dependent decreases were observed in IL-8 expression by inhibiting Src-dependent signaling molecules Erk-1/2 and p38 but not phosphatidylinositol 3-kinase. To assess the relevance of Src inhibition to angiogenesis, in vivo gelfoam assays were done. Robust infiltration of vessels was observed in gelfoam saturated with conditioned medium from pancreatic carcinoma cells. This angiogenesis was nearly abrogated in gelfoams saturated with conditioned medium from cells treated with the Src family kinase inhibitor, PP2 (P < 0.001). Thus, c-Src regulates critical "downstream" signaling pathways that contribute to expression of IL-8 in human pancreatic tumor cells, suggesting c-Src may be a target for therapeutic intervention in pancreatic adenocarcinoma.

c-Src regulates constitutive and EGF-mediated VEGF expression in pancreatic tumor cells through activation of phosphatidyl inositol-3 kinase and p38 MAPK

OBJECTIVES

Multiple signaling proteins may be aberrantly activated and/or overexpressed in pancreatic tumors, including the nonreceptor protein tyrosine kinase Src. The goal of this study was to determine the role of Src in regulating VEGF expression and angiogenic potential in pancreatic cancer cell lines.

METHODS

Src activity was inhibited using the Src family kinase selective inhibitor PP2, and c-Src expression was down-regulated via siRNA. The activities of downstream signaling molecules phosphatidyl inositol 3'-kinase (PI3K) and p38 mitogen-activated protein kinase (MAPK) were disrupted via selective inhibitors. In vivo angiogenesis was assessed through the use of a gel-foam assay.

RESULTS

Inhibition of Src activity or expression decreases both constitutive and EGF-induced VEGF production. Both the PI3K/Akt and p38 MAPK pathways are activated in a Src family kinase-dependent fashion on EGF-R activation and are important for EGF-mediated VEGF production in pancreatic cancer cells. Additionally, media from Src-inhibited L3.6pl cells fail to promote angiogenesis into gel foams implanted subcutaneously into mice, whereas media from control cells promote a robust angiogenic response.

CONCLUSIONS

Src activity contributes to constitutive and EGF-induced VEGF expression and angiogenic potential in pancreatic cancer cells. Therefore, Src may be a viable target for antiangiogenesis therapy in pancreatic cancer.

Differential effects of vascular endothelial growth factor receptor-2 inhibitor ZD6474 on circulating endothelial progenitors and mature circulating endothelial cells: implications for use as a surrogate marker of antiangiogenic activity

PURPOSE

Circulating endothelial cells (CEC) comprise at least two distinct populations: bone marrow-derived circulating endothelial progenitors (CEP) and mature CECs derived from existing vasculature. We hypothesized that antiangiogenic agents may have differential effects on CEPs and mature CECs and that these changes may serve as a marker of biological activity.

EXPERIMENTAL DESIGN

The effect of angiogenesis inhibitors on CECs was evaluated by flow cytometry after vascular endothelial growth factor (VEGF)-induced mobilization and in mice bearing Lewis lung carcinoma (LLC). Tumor angiogenesis was evaluated in parallel by immunohistochemistry.

RESULTS

In nontumor-bearing mice, VEGF administration increased both mature CECs and CEPs. This increase was inhibited by the VEGF receptor 2 inhibitor ZD6474 as well as the VEGF inhibitor-soluble Flt-1. ZD6474 had no significant effect on CECs in the absence of exogenous VEGF stimulation. In contrast, LLC-bearing mice had an increase in mature CECs but not CEPs after 3 days of treatment with ZD6474. The increase in mature CECs was dose-dependent, accompanied by a decrease in tumor microvessel density, and preceded reduction in tumor volume. Treatment of LLC-bearing mice with the vascular targeting agent ZD6126 also increased mature CECs.

CONCLUSIONS

VEGF inhibitors can have differential effects on mature CECs and CEPs, and agents inhibiting tumor angiogenesis may cause a concomitant increase in mature CECs. This increase occurs in tumor-bearing but not in nontumor-bearing mice, suggesting that tumor endothelium is a potential source of mature CECs. Therefore, assessing both mature CECs and CEPs may provide insights into the mechanism of antiangiogenic agents and serve as an early surrogate marker of biological activity.

Radioiodine therapy of colon cancer following tissue-specific sodium iodide symporter gene transfer

We investigated the feasibility of using radioiodine therapy in colon carcinoma cells (HCT 116) following tumor-specific expression of the human sodium iodide symporter (hNIS) using the carcinoembryonic antigen (CEA) promoter. HCT 116 cells were stably transfected with an expression vector, in which hNIS cDNA has been coupled to a CEA promoter fragment. This promoter is responsible for tissue-specific expression of CEA in gastrointestinal tract epithelium, and has been shown to target therapeutic genes to colorectal cancer cells. Functional NIS expression was confirmed by iodide uptake assay, Western blot analysis, immunostaining and in vitro clonogenic assay. The stably transfected HCT 116 cells concentrated (125)I about 10-fold in vitro without evidence of iodide organification. In contrast, transfection of control cancer cells without CEA expression did not result in iodide accumulation. Western blot analysis using a hNIS-specific antibody revealed a band of approximately 90 kDa. In addition, immunostaining of stably transfected HCT 116 cells revealed hNIS-specific membrane-associated immunoreactivity. In an in vitro clonogenic assay approximately 95% of stably transfected HCT 116 cells were killed by exposure to (131)I, while only about 5% of NIS-negative control cells were killed. Further, using an adenovirus carrying the NIS gene linked to the CEA promoter, high levels of tumor-specific radioiodide accumulation were induced in HCT 116 cells. In conclusion, a therapeutic effect of (131)I has been demonstrated in colon carcinoma cells following induction of tumor-specific iodide uptake activity by CEA promoter-directed NIS expression in vitro. This study demonstrates the potential of NIS as a therapeutic gene allowing radioiodine therapy of colon cancer following tumor-specific NIS gene transfer.

The sodium-iodide symporter

The sodium-iodide symporter (NIS) is an intrinsic plasma membrane protein that mediates active transport of iodide in the thyroid gland and several other extra-thyroidal tissues. This activity has been utilized for many years for imaging the thyroid gland and for treatment of thyroid disease both benign and malignant. Cloning and characterization of NIS has more recently allowed research into its use in non-thyroidal cancers through gene transfer for both diagnosis and treatment.

Administration of optimal biological dose and schedule of interferon alpha combined with gemcitabine induces apoptosis in tumor-associated endothelial cells and reduces growth of human pancreatic carcinoma implanted orthotopically in nude mice

PURPOSE

We determined whether chronic administration of IFN-alpha at optimal biological dose inhibits angiogenesis of human pancreatic carcinoma growing in the pancreas of nude mice.

EXPERIMENTAL DESIGN

Cells of the human pancreatic cancer cell line L3.6pl were implanted into the pancreas of nude mice. Seven days later, groups of mice received s.c. injection with IFN-alpha alone (50,000 units biweekly or 10,000 units daily), i.p. injection with gemcitabine alone (125 mg/kg biweekly), or injection with both daily IFN-alpha and biweekly gemcitabine for 35 days. In a survival study, the mice were treated until they became moribund.

RESULTS

Biweekly treatments with 50,000 units of IFN-alpha alone were ineffective. In contrast, daily injections of IFN-alpha (10,000 units/day) alone, biweekly injections of gemcitabine alone, or the combination of IFN-alpha and gemcitabine reduced tumor volume by 53%, 70%, and 87%, respectively. Immunohistochemical analysis revealed that treatment with IFN-alpha alone or with IFN-alpha plus gemcitabine inhibited expression of the proangiogenic molecules basic fibroblast growth factor and matrix metalloproteinase 9 more than did treatment with gemcitabine alone. These treatments also decreased the staining of proliferating cell nuclear antigen within the tumor and induced apoptosis in tumor-associated mouse endothelial cells (staining with CD31/terminal deoxynucleotidyl transferase-mediated nick end labeling), leading to a decrease in microvessel density.

CONCLUSIONS

These data show that administration of IFN-alpha at optimal biological dose and schedule in combination with gemcitabine induced apoptosis in tumor-associated endothelial cells and decreased growth of human pancreatic cancer cells in the pancreas, leading to a significant increase in survival.