Role and Regulation of EphA2 in Pancreatic Cancer

Pancreatic ductal adenocarcinoma (PDAC) is the fourth leading cancer cause of death in the US. Gemcitabine is the first-line therapy for this disease, but unfortunately it shows only very modest benefit. The focus of the current study was to investigate the role and regulation of EphA2, a receptor tyrosine kinase expressed in PDAC, to further understand this disease and identify new therapeutic targets. The role of EphA2 was determined in PDAC by siRNA mediated silencing. In combination with gemcitabine, silencing of EphA2 caused a dramatic increase in apoptosis even in highly resistant cells in vitro. Furthermore, EphA2 silencing was found to be useful in 2 orthotopic models in vivo: 1) shRNA-pretreated Miapaca-2 cells, and 2) in vivo delivery of siRNA to established MPanc96 tumors. Silencing of EphA2 alone reduced tumor growth in Miapaca-2 cells. In MPanc96, only the combination treatment of gemcitabine plus siEphA2 significantly reduced tumor growth, as well as the number of lung and liver metastases. Taken together, these observations support EphA2 as a target for combination therapies for PDAC. The regulation of EphA2 was further explored with a focus on the role of Ras. K-Ras activating mutations are the most important initiating event in PDAC. We demonstrated that Ras regulates EphA2 expression through activation of MEK2 and phosphorylation of ERK. Downstream of ERK, silencing of the transcription factor AP-1 subunit c-Jun or inhibition of the ERK effector RSK caused a decrease in EphA2 expression, supporting their roles in this process. Further examination of Ras/MEK/ERK pathway modulators revealed that PEA-15, a protein that sequesters ERK to the cytoplasm, inhibited expression of EphA2. A significant inverse correlation between EphA2 and PEA-15 levels was observed in mouse models of PDAC. In cells where an EGFR inhibitor reduced phospho-Erk, expression of EphA2 was also reduced, indicating that changes in EphA2 levels may allow monitoring the effectiveness of anti-Ras/MEK/ERK therapies. In conclusion, EphA2 levels may be a good prognostic factor for anti-EGFR/anti-Ras therapies, and EphA2 itself is a relevant target for the development of new therapies.

Altered Responses to Endoplasmic Reticulum Stress in Pancreatic Cancer

Pancreatic ductal adenocarcinoma (PDAC) represents the fourth most common cause of cancer-associated death in the United States. Little progress has been made in understanding how proteotoxic stress affects rapidly proliferating pancreatic tumor cells. Endoplasmic reticulum (ER) stress occurs when protein homeostasis in the ER lumen is perturbed. ER stress activates the unfolded protein response (UPR) to reduce the protein load in the ER. Under conditions of moderate ER stress, the UPR promotes cell cycle arrest which allows time for successful protein load reduction and enables cell survival. However, under conditions of high levels of ER stress the UPR induces cellular apoptosis. In this dissertation, I investigated the role of endoplasmic reticulum (ER) stress and its effects on the cell cycle in pancreatic cancer cells. Activation of the unfolded protein response after ER stress induction was determined by comparing expression of key UPR mediators in non-tumorigenic pancreatic ductal cells to pancreatic cancer cells. Two arms of the UPR were assessed: eIF2α/ATF4/CHOP and IRE1α/XBP1s. Pancreatic cancer cells exhibited altered UPR activation characterized by a delay in both phosphorylation of eIF2α and induction of spliced XBP1. Further evaluation of the UPR-mediated effects on cell cycle progression revealed that pancreatic cancer cells showed a compromised ability to inhibit G1 to S phase progression after ER stress. This reduced ability to arrest proliferation was found to be due to an impaired ability to downregulate cyclin D1, a key gatekeeper of the G1/S checkpoint. Abrogation of cyclin D1 repression was mediated through a slow induction of phosphorylation of eIF2α, a critical mediator of translational attenuation in response to ER stress. In conclusion, pancreatic cancer cells demonstrate a globally compromised ability to regulate the unfolded protein response. This deficiency results in reduced cyclin D1 repression through an eIF2α-mediated mechanism. These findings indicate that pancreatic cancer cells have increased tolerance for elevated ER stress compared to normal cells, and this tolerance results in continued tumor cell proliferation under proteotoxic conditions.

LY2109761, a novel transforming growth factor beta receptor type I and type II dual inhibitor, as a therapeutic approach to suppressing pancreatic cancer metastasis.

Most pancreatic cancer patients present with inoperable disease or develop metastases after surgery. Conventional therapies are usually ineffective in treating metastatic disease. It is evident that novel therapies remain to be developed. Transforming growth factor beta (TGF-beta) plays a key role in cancer metastasis, signaling through the TGF-beta type I/II receptors (TbetaRI/II). We hypothesized that targeting TbetaRI/II kinase activity with the novel inhibitor LY2109761 would suppress pancreatic cancer metastatic processes. The effect of LY2109761 has been evaluated on soft agar growth, migration, invasion using a fibroblast coculture model, and detachment-induced apoptosis (anoikis) by Annexin V flow cytometric analysis. The efficacy of LY2109761 on tumor growth, survival, and reduction of spontaneous metastasis have been evaluated in an orthotopic murine model of metastatic pancreatic cancer expressing both luciferase and green fluorescence proteins (L3.6pl/GLT). To determine whether pancreatic cancer cells or the cells in the liver microenvironment were involved in LY2109761-mediated reduction of liver metastasis, we used a model of experimental liver metastasis. LY2109761 significantly inhibited the L3.6pl/GLT soft agar growth, suppressed both basal and TGF-beta1-induced cell migration and invasion, and induced anoikis. In vivo, LY2109761, in combination with gemcitabine, significantly reduced the tumor burden, prolonged survival, and reduced spontaneous abdominal metastases. Results from the experimental liver metastasis models indicate an important role for targeting TbetaRI/II kinase activity on tumor and liver microenvironment cells in suppressing liver metastasis. Targeting TbetaRI/II kinase activity on pancreatic cancer cells or the cells of the liver microenvironment represents a novel therapeutic approach to prevent pancreatic cancer metastasis.

ROLE OF PROSTAGLANDIN E2 IN THE REGULATION OF PANCREATIC STELLATE CELLS HYPER ACTIVITY ASSOCIATED WITH PANCREATIC CANCER

Pancreatic cancer is one of the most lethal type of cancer due to its high metastasis rate and resistance to chemotherapy. Pancreatic fibrosis is a constant pathological feature of chronic pancreatitis and the hyperactive stroma associated with pancreatic cancer. Strong evidence supports an important role of cyclooxygenase-2 (COX-2) and COX-2 generated prostaglandin E2 (PGE2) during pancreatic fibrosis. Pancreatic stellate cells (PSC) are the predominant source of extracellular matrix production (ECM), thus being the key players in both diseases. Given this background, the primary objective is to delineate the role of PGE2 on human pancreatic stellate cells (PSC) hyper activation associated with pancreatic cancer. This study showed that human PSC cells express COX-2 and synthesize high levels of PGE2. PGE2 stimulated PSC migration and invasion; expression of extra cellular matrix (ECM) genes and tissue degrading matrix metallo proteinases (MMP) genes. I further identified the PGE2 EP receptor responsible for mediating these effects on PSC. Using genetic and pharmacological approaches I identified the receptor required for PGE2 mediates PSC hyper activation. Treating PSC with Specific antagonists against EP1, EP2 and EP4, demonstrated that blocking EP4 receptor only, resulted in a complete reduction of PGE2 mediated PSC activation. Furthermore, siRNA mediated silencing of EP4, but not other EP receptors, blocked the effects of PGE2 on PSC fibrogenic activity. Further examination of the downstream pathway modulators revealed that PGE2 stimulation of PSC involved CREB and not AKT pathway. The regulation of PSC by PGE2 was further investigated at the molecular level, with a focus on COL1A1. Collagen I deposition by PSC is one of the most important events in pancreatic cancer. I found that PGE2 regulates PSC through activation of COL1A1 expression and transcriptional activity. Downstream of PGE2, silencing of EP4 receptor caused a complete reduction of COL1A1 expression and activity supporting the role of EP4 mediated stimulation of PSC. Taken together, this data indicate that PGE2 regulates PSC via EP4 and suggest that EP4 can be a better therapeutic target for pancreatic cancer to reduce the extensive stromal reaction, possibly in combination with chemotherapeutic drugs can further kill pancreatic cancer cells.

THE MECHANISM OF TUMORIGENESIS IN THE IMMORTALIZED HUMAN PANCREATIC CELL LINES: CELL CULTURE MODELS OF HUMAN PANCREATIC CANCER

The mechanism of tumorigenesis in the immortalized human pancreatic cell lines: cell culture models of human pancreatic cancer Pancreatic ductal adenocarcinoma (PDAC) is the most lethal cancer in the world. The most common genetic lesions identified in PDAC include activation of K-ras (90%) and Her2 (70%), loss of p16 (95%) and p14 (40%), inactivation p53 (50-75%) and Smad4 (55%). However, the role of these signature gene alterations in PDAC is still not well understood, especially, how these genetic lesions individually or in combination contribute mechanistically to human pancreatic oncogenesis is still elusive. Moreover, a cell culture transformation model with sequential accumulation of signature genetic alterations in human pancreatic ductal cells that resembles the multiple-step human pancreatic carcinogenesis is still not established. In the present study, through the stepwise introduction of the signature genetic alterations in PDAC into the HPV16-E6E7 immortalized human pancreatic duct epithelial (HPDE) cell line and the hTERT immortalized human pancreatic ductal HPNE cell line, we developed the novel experimental cell culture transformation models with the most frequent gene alterations in PDAC and further dissected the molecular mechanism of transformation. We demonstrated that the combination of activation of K-ras and Her2, inactivation of p16/p14 and Smad4, or K-ras mutation plus p16 inactivation, was sufficient for the tumorigenic transformation of HPDE or HPNE cells respectively. We found that these transformed cells exhibited enhanced cell proliferation, anchorage-independent growth in soft agar, and grew tumors with PDAC histopathological features in orthotopic mouse model. Molecular analysis showed that the activation of K-ras and Her2 downstream effector pathways –MAPK, RalA, FAK, together with upregulation of cyclins and c-myc were involved in the malignant transformation. We discovered that MDM2, BMP7 and Bmi-1 were overexpressed in the tumorigenic HPDE cells, and that Smad4 played important roles in regulation of BMP7 and Bmi-1 gene expression and the tumorigenic transformation of HPDE cells. IPA signaling pathway analysis of microarray data revealed that abnormal signaling pathways are involved in transformation. This study is the first complete transformation model of human pancreatic ductal cells with the most common gene alterations in PDAC. Altogether, these novel transformation models more closely recapitulate the human pancreatic carcinogenesis from the cell origin, gene lesion, and activation of specific signaling pathway and histopathological features.

THE ROLE OF TAK1 IN PANCREATIC CANCER DEVELOPMENT

Pancreatic cancer is the fourth leading cause of cancer-related mortality in the United States and the fifth leading cause of cancer-related mortality worldwide. Pancreatic cancer is a big challenge in large due to the lack of early symptoms. In addition, drug resistance is a major obstacle to the success of chemotherapy in pancreatic cancer. The underlying mechanism of drug resistance in human pancreatic cancers is not well understood. Better understanding of the mechanism of molecular pathways in human pancreatic cancers can help to identify the novel therapeutic target candidates, and develop the new preventive and clinic strategies to improve patient survival. We discovered that TAK1 is overexpressed in pancreatic cancer cell lines and patient tumor tissues. We demonstrated that the elevated activity of TAK1 is caused by its binding partner TAB1. Knocking down of TAK1 in pancreatic cancer cells with RNAi technique resulted in cell apoptosis and significantly reduces the size of tumors in mice and made a chemotherapy drug more potent. Targeting the kinase activity of TAK1 with the selective inhibitor LY2610956 strongly synergized in vitro with the antitumor activity of gemcitabine, oxaliplatin, or irinotecan on pancreatic cancer cells. These findings highlighted that TAK1 could be a potential therapeutic target for pancreatic cancer. We also demonstrated that TAK activity is regulated by its binding protein TAB1. We defined a minimum TAB1 sequence which is required and sufficient for TAK1 kinase activity. We created a recombinant TAK1-TAB1 C68 fusion form which has highly kinase activity. This active form could is used for screening TAK1 inhibitors. In addition, several posttranslational modifications were identified in our study. The acetylation of lysine 158 on TAK1 is required for kinase activity. This site is conserved throughout all of kinase. Our findings may reveal a new mechanism by which kinase activity is regulated.

THE EFFECTS OF CURCUMIN ON BODY COMPOSITION OF PATIENTS WITH ADVANCED PANCREATIC CANCER

Cachexia is very common among patients with advanced pancreatic cancer and is a marker of poor prognosis. Weight loss in cachexia is due to both adipose and muscle compartments, and sarcopenia (severe muscle depletion) is associated with worse outcomes. Curcumin has shown a myriad of biological effects, including anti-cancer and anti-inflammatory. The ability of curcumin to attenuate cachexia and muscle loss has been tested in animal models, with conflicting results so far. The hypothesis of this study was that patients with advanced pancreatic cancer treated with curcumin for two months have less fat and muscle loss as compared to matched controls not treated with this compound. A matched 1:2 case-control retrospective study was conducted with 22 patients with pancreatic cancer who were treated with curcumin on a previous protocol and 44 untreated controls with the same diagnosis matched by age, gender, time from advanced cancer, body mass index, and number of prior therapies. Data was collected regarding oncologic treatment, medication use, weights, heights, and survival. Body composition was determined by computerized tomography analyses at two timepoints separated by 60±20 days. For treated patients, the first image was at the beginning of treatment and for controls it was determined by the matching time from advanced cancer. The evolution of body composition over time was quantitatively analyzed comparing both groups. All patients lost weight both due to fat and muscle losses, and patients treated with curcumin presented greater losses both in lean adipose body mass. Use of medications, chemotherapy, age, time from advanced cancer, baseline albumin, performance status, and number of prior therapies were not independently correlated with changes in body composition variables. Patients treated with curcumin had borderline shorter survival when compared with untreated patients. Sarcopenic treated patients had significantly shorter survival than non-sarcopenic counterparts, and sarcopenia status was not associated with survival among the controls. Treated patients with shorter survival showed a tendency to lose more lean and especially fat body mass as compared to untreated patients, maybe suggesting an effect of curcumin on shifting weight loss towards the end of life by impacting its mechanisms.

Prognostic significance of xCT polymorphisms and expression in patients with advanced pancreatic cancer treated with chemotherapy

The plasma membrane xc- cystine/glutamate transporter mediates cellular uptake of cystine in exchange for intracellular glutamate and is highly expressed by pancreatic cancer cells. The xCT gene, encoding the cystine-specific xCT protein subunit of xc-, is important in regulating intracellular glutathione (GSH) levels, critical for cancer cell protection against oxidative stress, tumor growth and resistance to chemotherapeutic agents including platinum. We examined 4 single nucleotide polymorphisms (SNPs) of the xCT gene in 269 advanced pancreatic cancer patients who received first line gemcitabine with or without cisplatin or oxaliplatin. Genotyping was performed using Taqman real-time PCR assays. A statistically significant correlation was noted between the 3' untranslated region (UTR) xCT SNP rs7674870 and overall survival (OS): Median survival time (MST) was 10.9 and 13.6 months, respectively, for the TT and TC/CC genotypes (p = 0.027). Stratified analysis showed the genotype effect was significant in patients receiving gemcitabine in combination with platinum therapy (n = 145): MST was 10.5 versus 14.1 months for the TT and TC/CC genotypes, respectively (p = 0.013). The 3' UTR xCT SNP rs7674870 may correlate with OS in pancreatic cancer patients receiving gemcitabine and platinum combination therapy. Paraffin-embedded core and surgical biopsy tumor specimens from 98 patients with metastatic pancreatic adenocarcinoma were analyzed by immunohistochemistry using an xCT specific antibody. xCT protein IHC expression scores were analyzed in relation to overall survival in 86 patients and genotype in 12 patients and no statistically significant association was found between the level of xCT IHC expression score and overall survival (p = 0.514). When xCT expression was analyzed in terms of treatment response, no statistically significant associations could be determined (p = 0.908). These data suggest that polymorphic variants of xCT may have predictive value, and that the xc- transporter may represent an important target for therapy in pancreatic cancer.

Regulation of vascular endothelial growth factor expression in human pancreatic cancer

Pancreatic adenocarcinoma is currently the fifth-leading cause of cancer-related death in the United States. Like with other solid tumors, the growth and metastasis of pancreatic adenocarcinoma are dependent on angiogenesis. Vascular endothelial growth factor (VEGF) is a key angiogenic molecule that plays an important role in angiogenesis, growth and metastasis of many types of human cancer, including pancreatic adenocarcinoma. However, the expression and regulation of VEGF in human pancreatic cancer cells are mostly unknown. ^ To examine the hypothesis that VEGF is constitutively expressed in human pancreatic cancer cells, and can be further induced by tumor environment factors such as nitric oxide, a panel of human pancreatic cancer cell lines were studied for constitutive and inducible VEGF expression. All the cell lines examined were shown to constitutively express various levels of VEGF. To identify the mechanisms responsible for the elevated expression of VEGF, its rates of turnover and transcription were then investigated. While the half-live of VEGF was unaffected, higher transcription rates and increased VEGF promoter activity were observed in tumor cells that constitutively expressed elevated levels of VEGF. Detailed VEGF promoter analyses revealed that the region from −267 to +50, which contains five putative Sp1 binding sites, was responsible for this VEGF promoter activity. Further deletion and point mutation analyses indicated that deletion of any of the four proximal Sp1 binding sites significantly diminished VEGF promoter activity and when all four binding sites were mutated, it was completely abrogated. Consistent with these observations, high levels of constitutive Sp1 expression and DNA binding activities were detected in pancreatic cancer cells expressing high levels of VEGF. Collectively, our data indicates that constitutively expressed Sp1 leads to the constitutive expression of VEGF, and implicates that both molecules involve in the aggressive pathogenesis of human pancreatic cancer. ^ Although constitutively expressed in pancreatic cancer cells, VEGF can be further induced. In human pancreatic cancer specimens, we found that in addition to VEGF, both inducible nitric oxide synthase (iNOS) and endothelial nitric oxide synthase (eNOS) were overexpressed, suggesting that nitric oxide might upregulate VEGF expression. Indeed, a nitric oxide donor S-nitroso-N-acetyl-D,L-penicillamine (SNAP) significantly induced VEGF mRNA expression and protein secretion in pancreatic adenocarcinoma cells in a time- and dose-dependant manner. Using a luciferase reporter containing both the VEGF promoter and the 3′ -UTR, we showed that SNAP significantly increased luciferase activity in human pancreatic cancer cells. Notwithstanding its ability to induce VEGF in vitro, pancreatic cancer cells genetically engineered to produce NO did not exhibit increased tumor growth. This inability of NO to promote tumor growth appears to be related to NO-mediated cytotoxicity. The balance between NO mediated effects on pro-angiogenesis and cytotoxicity would determine the biological outcome of NO action on tumor cells. ^ In summary, we have demonstrated that VEGF is constitutively expressed in human pancreatic cancer cells, and that overexpression of transcription factor Sp1 is primarily responsible. Although constitutively expressed in these cells, VEGF can be further induced by NO. However, using a mouse model, we have shown that NO inhibited tumor growth by promoting cytotoxicity. These studies suggest that both Sp1 and NO may be important targets for designing potentially effective therapies of human pancreatic cancer and warrant further investigation. ^

Molecular mechanisms of NF-kappaB activation in metastatic pancreatic cancer cells

Pancreatic adenocarcinoma is the fourth leading cause of adult cancer death in the United States. At the time of diagnosis, most patients with pancreatic cancer have advanced and metastatic disease, which makes most of the traditional therapeutic strategies are ineffective for pancreatic cancer. A better understanding of the molecular basis of pancreatic cancer will provide the approach to identify the new strategies for early diagnosis and treatment. NF-κB is a family of transcription factor that play important roles in immune response, cell growth, apoptosis, and tumor development. We have shown that NF-κB is constitutively activated in most human pancreatic tumor tissues and cell lines, but not in the normal tissues and HPV E6E7 gene-immortalized human pancreatic ductal epithelial cells (HPDE/E6E7). By infecting the pancreatic cancer cell line Aspc-1 with a replication defective retrovirus expressing phosphorylation-defective IκBα (IκBαM), the constitutive NF-κB activation is blocked. Subsequent injection of this Aspc-1/IκBαM cells into the pancreas of athymic nude mice showed that liver metastasis is suppressed by the blockade of NF-κB activation. Current studies showed that an autocrine mechanism accounts for the constitutive activation of NF-κB in metastatic human pancreatic cancer cell lines, but not in nonmetastatic human pancreatic cancer cell lines. Further investigation showed that interleukin-1α (IL-1α) was the primary cytokine secreted by these cells that activates NF-κB. Inhibition of IL-1α activity suppressed the constitutive activation of NF-κB and the expression of its downstream target gene, uPA, in metastatic pancreatic cancer cell lines. Even though IL-1α is one of the previously identified NF-κB downstream target genes, our results demonstrate that regulation of IL-1α expression is independent of NF-κB and primarily dependent on AP-1 activity, which is in part induced by overexpression of EGF receptors and activation of MAP kinases. In conclusion, our findings suggest a possible mechanism by which NF-κB is constitutively activated in metastatic human pancreatic cancer cells and a possible missing mechanistic links between inflammation and cancer. ^

Induction of endoplasmic reticular stress by bortezomib: A novel therapeutic strategy for pancreatic cancer

Bortezomib (VELCADE™, formerly known as PS-341) is a selective and potent inhibitor of the proteasome that was recently FDA-approved for the treatment of multiple myeloma. Despite its success in multiple myeloma and progression into clinical trials for other malignancies, bortezomib's exact mechanism of action remains undefined. The major objective of this study was to evaluate the anticancer activity of this drug using in vitro and in vivo pancreatic cancer models and determine whether bortezomib-induced apoptosis occurs via induction of endoplasmic reticular (ER) stress. The investigation revealed that bortezomib inhibited tumor cell proliferation via abrogation of cdk activity and induced apoptosis in pancreatic cancer cell lines. I hypothesized that bortezomib-induced apoptosis was triggered by a large accumulation ubiquitin-conjugated proteins that resulted in ER stress. My data demonstrated that bortezomib induced a unique type of ER stress in that it inhibited PKR-like ER kinase (PERK) and subsequent phosphorylation of eukaryotic initiation factor 2α (eif2α), a key event in translational suppression. The combined effects of proteasome inhibition and the failure to attenuate translation resulted in an accumulation of aggregated proteins (proteotoxicity), JNK activation, cytochrome c release, caspase-3 activation, and DNA fragmentation. Bortezomib also enhanced apoptosis induced by other agents that stimulated the unfolded protein response (UPR), demonstrating that translational suppression is a critical cytoprotective mechanism during ER stress. Tumor cells attempt to survive bortezomib-induced ER stress by sequestering aggregated proteins into large structures, termed aggresomes. Since histone deacetylase 6 (HDAC6) is essential for aggresome formation, tumor cells may be sensitized to bortezomib-induced apoptosis by blocking HDAC function. My results demonstrated that HDAC inhibitors disrupted aggresome formation and synergized with bortezomib to induce apoptosis in pancreatic cancer or multiple myeloma cells in vitro and in orthotopic pancreatic tumors in vivo. Taken together, my data establish a mechanistic link between bortezomib-induced aggresome formation, ER stress, and apoptosis and identify a novel therapeutic strategy for the treatment of pancreatic cancer and other hematologic and solid malignancies. ^

The transcription factor nuclear factor kappa B (NFkappaB) maintains TRAIL resistance in human pancreatic cancer cells

Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL/Apo2L) is a member of the TNF family of cytokines that induces apoptosis in a variety of tumor cells while sparing normal cells. However, many human cancer cell lines display resistance to TRAIL-induced apoptosis and the mechanisms contributing to resistance remain controversial. Previous studies have demonstrated that the dimeric transcription factor Nuclear Factor kappa B (NFκB) is constitutively active in a majority of human pancreatic cancer cell lines and primary tumors, and although its role in tumor progression remains unclear it has been suggested that NFκB contributes to TRAIL resistance. Based on this, I examined the effects of NFκB inhibitors on TRAIL sensitivity in a panel of nine pancreatic cancer cell lines. I show here that inhibitors of NFκB, including two inhibitors of the proteasome (bortezomib (Velcade™, PS-341) and NPI-0052), a small molecule inhibitor of IKK (PS1145), and a novel synthetic diterpene NIK inhibitor (NPI-1342) reverse TRAIL resistance in pancreatic cancer cell lines. Further analysis revealed that the expression of the anti-apoptosic proteins BclXL and XIAP was significantly decreased following exposure to these inhibitors alone and in combination with TRAIL. Additionally, treatment with NPI0052 and TRAIL significantly reduced tumor burden relative to the control tumors in an L3.6pl orthotopic pancreatic xenograft model. This was associated with a significant decrease in proliferation and an increase in caspase 3 and 8 cleavage. Combination therapy employing PS1145 or NPI-1342 in combination with TRAIL also resulted in a significant reduction in tumor burden compared to either agent alone in a Panc1 orthotopic xenograft model. My studies show that combination therapy with inhibitors of NFκB alone and TRAIL is effective in pre-clinical models of pancreatic cancer and suggests that the approach should be evaluated in patients. ^

Hormonal exposure and risk of pancreatic cancer in the United States

Background. In the United States, the incidence of pancreatic cancer has increased; more than 37,000 new cases of pancreatic cancer were diagnosed in the year 2007. Overall, the five-year survival rate is about 5% and pancreatic cancer ranks the fourth leading cause of cancer-related mortality among men and women. Despite the observed progress in cancer diagnosis and treatment, pancreatic cancer remains an unresolved significant public health problem in the United States. Familial pancreatic cancer has been confirmed to be responsible for approximately 10% of pancreatic cancer cases. However, 90% are still without known inherited predisposition. Until now, the role of oral contraceptive pills (OCPs) and hormonal replacement therapy (HRT) among women with pancreatic cancer remain unclear. We examined the association of exogenous hormonal uses in US women with risk of pancreatic cancer. ^ Methods. This was an active hospital-based case-control study which is conducted at the department of gastrointestinal medical oncology in The University of Texas M.D. Anderson Cancer Center. Between January 2005 and December 2007, a total of 287 women with pathologically confirmed pancreatic cancer (cases) and 287 healthy women (controls) were included in this investigation. Both cases and controls were frequency matched by age and race. Information about the use of hormonal contraceptives and hormonal replacement therapy (HRT) preparations as well as information about several risk factors of pancreatic cancer were collected by personal interview. Univariate and multivariate analyses were performed in this study to analyze the data. ^ Results. We found a statistical significant protective effect for use of exogenous hormone preparations on pancreatic cancer development (adjusted odds ratio [AOR], 0.4; 95% confidence interval [CI], 0.2–0.8). In addition, a 40% reduction in pancreatic cancer risk was observed among women who ever used any of the contraceptive methods including oral contraceptive pills (AOR, 6; 95% CI, 0.4–0.9). ^ Conclusions. Consistent with previous studies, the use of exogenous hormone preparations including oral contraceptive pills may confers a protective effect for pancreatic cancer development. More studies are warranted to explore for the underlying mechanism of such protection.^

Anticancer activity of OSW-1: Induction of apoptotic pathway in leukemia and autophagic death in pancreatic cancer through a calcium mediated mechanism

OSW-1 is a natural compound found in the bulbs of Orninithogalum saudersiae, a member of the lily family. This compound exhibits potent antitumor activity in vitro with the IC50 values in the low nanomolar concentration range and demonstrating its ability to kill drug resistant cancer cells. In an effort to discover the unknown mechanism of action of this novel compound as a potential anticancer agent, the main objective of this research project was to test the cytotoxicity of OSW-1 against various cancer lines, and to elucidate the biochemical and molecular mechanism(s) responsible for the anticancer activity of OSW-1. My initial investigation revealed that OSW-1 is effective in killing various cancer cells including pancreatic cancer cells and primary leukemia cells resistant to standard chemotherapeutic agents, and that non-malignant cells were less sensitive to this compound. Further studies revealed that in leukemia cells, OSW-1 causes a significant increase in cytosolic calcium and activates rapid calcium-dependent apoptosis by the intrinsic pathway. Additionally, OSW-1 treatment leads to the degradation of the ER chaperone GRP78/BiP implicated in the survival of cancer cells. Meanwhile, it shows a reduced sensitivity in respiration-deficient sub-clones of leukemia cells which had higher basal levels of Ca2+. Mechanistically, it was further demonstrated that cytosolic Ca2+ elevations were observed together with Na+ decreases in the cytosol, suggesting OSW-1 caused the calcium overload through inhibition of the Na+/Ca 2+exchanger (NCX). Although similar calcium disturbances were observed in pancreatic cancer cells, mechanistic studies revealed that autophagy served as an initial pro-survival mechanism subsequent to OSW-1 treatment but extended autophagy caused inevitable cell death. Furthermore, combination of OSW-1 with autophagy inhibitors significantly enhances the cytotoxicity against pancreatic cancer cells. Taken together, this study revealed the novel mechanism of OSW-1 which is through inhibition of the Na+/Ca2+ exchanger and provides a basis for using this compound in combination with other agents for the treatment of pancreatic cancer which is resistant to available anticancer drugs. ^

Pancreatic cancer deaths in Texas veterans

Background/objective. Several studies have found an increased risk of pancreatic cancer in veterans deployed to Vietnam during the Vietnam War. Diabetes, a known risk factor for pancreatic cancer, has been designated as a service-connected illness in deployed Vietnam veterans. The majority of Vietnam veterans, now between the ages of 55 to 65, have not yet reached the ages of pancreatic cancer’s greatest prevalence, ages 65 to 79. This case-control study utilized 1998 electronic Texas death certificate data for white, black and Hispanic men to explore the question of whether military service was a risk factor for deaths due to pancreatic cancer among men who died in 1998.^ Methods. The primary study included men born between 1927 and 1953, and was a matched case-control study with two control groups; 431 pancreatic cancer cases were birth-year and race-matched one case to two non-neoplastic death controls and, for the second control group, were matched 1:1 with 431 accidental death controls. The exposure was military service, recorded as “yes”, “no” or “unknown” on the death certificate. Conditional logistic regression was used for the data analysis. Logistic regression was used in two additional unmatched analyses to examine the same exposure, military service, within different birth cohorts, again using pancreatic cancer cases with non-neoplastic and accidental death controls.^ Results. For pancreatic cancer cases matched to non-neoplastic controls, the association with military service showed an elevated odds ratio (OR) of 1.40 (95% confidence interval [CI] 1.10-1.79); matched to accidental death controls, a similar association with military service was detected [OR=1.40 (95% CI 1.04-1.89)]. The association was not seen in all time periods and was greatest for those within a birth cohort specific for Vietnam Era service. For men born between 1946 and 1950, OR=1.90 (95% CI 1.03-3.50) for comparison with non-neoplastic controls and OR=1.91 (95% CI 0.9995-3.64) for accidental death controls. ^ Conclusion. In Texas, for men aged 44-71, who died in 1998, military service was associated with an approximately 40% increased risk for pancreatic cancer. For men ages 48-52, military service was associated with an approximately 90% increased risk for pancreatic cancer.^