Behavioral facets of cancer chemoprevention trials

Few studies have explored factors related to participation in cancer chemoprevention trials. The purpose of this dissertation was to conduct investigations in this emerging field by studying aspects of participation at three phases of cancer chemoprevention trials: at enrollment, during a placebo run-in period, and post-trial. In all three studies, subjects had a history of cancer and were at high risk of recurrence or second primary tumors.^ The first study explored correlates of enrollment in a head and neck cancer chemoprevention trial by comparing participants and eligible nonparticipants. Of 148 subjects who met the trial's preliminary eligibility criteria, 40% enrolled. In multivariate analysis, enrollment was positively associated with being male (OR 2.36) and being employed (OR 2.73). The most commonly cited reason for declining participation among nonparticipants was transportation.^ The second study examined outcomes of an eight-week placebo run-in period in a head and neck cancer chemoprevention trial. Of 391 subjects, 91.3% were randomized after the run-in. Adherence to drug capsules ranged from 0% to 120.3% (mean $\pm$ SD, 95.8% $\pm$ 15.1). In multivariate analysis, the main variable predicting run-in outcome was race; white subjects were 3.45 times more likely to be randomized than non-white subjects. Subjects with Karnofsky scores of 100 were 2.13 times more likely to be randomized than were subjects with lower scores.^ The third study used post-trial questionnaires to assess subjects' (n = 64) perceptions of participation in a cancer chemoprevention trial. The most highly rated trial benefit was the perception of potential colon cancer prevention, and the most troublesome barrier was erroneous billing for study visits. Perceived benefits were positively associated with interest in participating in future trials of the same (p = 0.05) and longer (p = 0.02) duration, and difficulty with trial pills and procedures was inversely related to interest in future placebo-controlled trials (p = 0.01).^ These are among the first behavioral studies to be completed in the rapidly growing field of cancer chemoprevention. Much work has yet to be done, however, to advance our understanding of the complex issues relating to chemoprevention trial participation. ^

DISEASE-RELATED INFORMATION NEEDS OF CANCER PATIENTS AGES 11-20: A COMPARISON OF PATIENT-PARENT AND PATIENT-PHYSICIAN PERCEPTIONS

Innovative, aggressive treatments and prolonged survival rates for patients with childhood cancers have placed new demands on the patient, parent and physician. As a result, counterproductive coping behaviors are often noted in adolescent cancer patients.^ One of the main ways the environment is manipulated by the individual to achieve personal comfort is through selectivity of information. An individual will usually pull the support personally needed to cope from the environment if sufficient resources are available. However, information provided young cancer patients is often filtered through the physicians and parents perspectives of the patient's needs without systematic input from the patient. In order to ensure that adequate information resources are available to help teenage patients cope with their illness, health professionals must have insights into the information needs of those patients. No previous efforts to address this subject were found in the literature.^ This study was designed to identify adolescent perspectives of their disease-related information needs and to compare their viewpoints with those of their parents and physicians. Sixty-five outpatient cancer patients (ages 11-20) receiving treatment at the University of Texas M. D. Anderson Hospital and Tumor Institute in Houston, Texas, 60 of their parents, and 53 physicians, who were involved in the treatment of pediatric patients at M. D. Anderson, were asked to complete self-administered questionnaires. The questionnaires used were developed, administered and analyzed by the investigator. Specific areas addressed in the questionnaires included: Perceptions of cancer-related tests and treatments, the importance of 30 disease-related items of information, responses evoked by receipt of information, current and preferred sources of information, delivery of information at the time of diagnosis, and disease-related information requested for patients, family, friends and teachers.^ Adolescent perceptions of their information needs and their preferences for delivery of information were determined. The relationships between patient-parent and patient-physician perceptions were then analyzed to determine areas in which agreements and disparities in viewpoint existed. Programmatic and research recommendations were then provided.^ Hopefully, through these efforts, the adolescent patient will be helped to receive relevant information support from those deemed to be most important to his/her efforts to cope with cancer. ^

AN ASSESSMENT OF THE RELATION OF CANCER MORTALITY RATES AND SOURCES OF DRINKING WATER IN TEXAS

The geographic distribution of average annual age-adjusted mortality rates (1964-1976) for four types of cancer (all cancer sites combined, gastrointestinal, urinary, and lung cancer) were compared by sources of drinking water for 254 Texas counties and county rural areas and 301 Texas cities. Exposure variables considered were surface versus ground water, public water supplies versus individuals wells, and trihalomethane levels in municipal water supplies. Each general source of "surface" and "ground" water was further divided by aggregating ground water using areas by aquifers and surface water using study areas by river basins. Potential confounding variables taken into account included median education, employment in cancer risk industries, population mobility, ethnicity, and urbanicity. A pattern of higher and lower cancer mortality rates was found for populations using some aquifers and river basins. Further study is required to determine whether the differences in cancer mortality rates that were observed are related to drinking water content or are coincidental with differences in personal characteristics which could not be taken into account in this ecologic study design. ^

Mechanisms Underlying the Heterogeneous Sensitivities of Cancer Cells to Proteasome Inhibitors

The mechanisms underlying cellular response to proteasome inhibitors have not been clearly elucidated in solid tumor models. Evidence suggests that the ability of a cell to manage the amount of proteotoxic stress following proteasome inhibition dictates survival. In this study using the FDA-approved proteasome inhibitor bortezomib (Velcade®) in solid tumor cells, we demonstrated that perhaps the most critical response to proteasome inhibition is repression of global protein synthesis by phosphorylation of the eukaryotic initiation factor 2-α subunit (eIF2α). In a panel of 10 distinct human pancreatic cancer cells, we showed marked heterogeneity in the ability of cancer cells to induce eIF2α phosphorylation upon stress (eIF2α-P); lack of inducible eIF2α-P led to excessive accumulation of aggregated proteins, reactive oxygen species, and ultimately cell death. In addition, we examined complementary cytoprotective mechanisms involving the activation of the heat shock response (HSR), and found that induction of heat shock protein 70 kDa (Hsp72) protected against proteasome inhibitor-induced cell death in human bladder cancer cells. Finally, investigation of a novel histone deacetylase 6 (HDAC6)-selective inhibitor suggested that the cytoprotective role of the cytoplasmic histone deacetylase 6 (HDAC6) in response to proteasome inhibition may have been previously overestimated.

Improving follow-up of abnormal cancer screens using electronic health records: trust but verify test result communication.

BACKGROUND: Early detection of colorectal cancer through timely follow-up of positive Fecal Occult Blood Tests (FOBTs) remains a challenge. In our previous work, we found 40% of positive FOBT results eligible for colonoscopy had no documented response by a treating clinician at two weeks despite procedures for electronic result notification. We determined if technical and/or workflow-related aspects of automated communication in the electronic health record could lead to the lack of response. METHODS: Using both qualitative and quantitative methods, we evaluated positive FOBT communication in the electronic health record of a large, urban facility between May 2008 and March 2009. We identified the source of test result communication breakdown, and developed an intervention to fix the problem. Explicit medical record reviews measured timely follow-up (defined as response within 30 days of positive FOBT) pre- and post-intervention. RESULTS: Data from 11 interviews and tracking information from 490 FOBT alerts revealed that the software intended to alert primary care practitioners (PCPs) of positive FOBT results was not configured correctly and over a third of positive FOBTs were not transmitted to PCPs. Upon correction of the technical problem, lack of timely follow-up decreased immediately from 29.9% to 5.4% (p<0.01) and was sustained at month 4 following the intervention. CONCLUSION: Electronic communication of positive FOBT results should be monitored to avoid limiting colorectal cancer screening benefits. Robust quality assurance and oversight systems are needed to achieve this. Our methods may be useful for others seeking to improve follow-up of FOBTs in their systems.

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 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.

A quality of life subscale for terminally ill cancer patients

A subscale was developed to assess the quality of life of cancer patients with a life expectancy of six months or less. Phase I of this study identified the major concerns of 74 terminally ill cancer patients (19 with breast cancer, 19 with lung cancer, 18 with colorectal cancer, 9 with renal cell cancer, 9 with prostate cancer), 39 family caregivers, and 20 health care professionals. Patients interviewed were being treated at the University of Texas M. D. Anderson Cancer Center or at the Hospice at the Texas Medical Center in Houston. In Phase II, 120 patients (30 with breast cancer, 30 with lung cancer, 30 with colorectal cancer, 15 with prostate cancer, and 15 with renal cell cancer) rated the importance of these concerns for quality of life. Items retained for the subscale were rated as "extremely important" or "very important" by at least 60% of the sample and were reported as being applicable by at least two-thirds of the sample. The 61 concerns that were identified were formatted as a questionnaire for Phase III. In Phase III, 356 patients (89 with breast cancer, 88 with lung cancer, 88 with colorectal cancer, 44 with prostate cancer, and 47 with renal cell cancer) were interviewed to determine the subscale's reliability and sensitivity to change in clinical status. Both factor analysis and item response theory supported the inclusion of the same 35 items for the subscale. Internal consistency reliability was moderate to high for the subscale's domains: spiritual (0.87), existential (0.76), medical care (0.68), symptoms (0.67), social/family (0.66), and emotional (0.61). Test-retest correlation coefficients also were high for the domains: social/family (0.86), emotional (0.83), medical care (0.83), spiritual (0.75), existential (0.75), and symptoms (0.81).^ In addition, concurrent validity was supported by the high correlation between the subscale's symptom domain and symptom items from the European Organization for Research and Treatment of Cancer (EORTC) scale (r = 0.74). Patients' functional status was assessed with the Eastern Cooperative Oncology Group (ECOG) Performance status rating. When ECOG categories were compared to subscale domains, patients who scored lower in functional status had lower scores in the spiritual, existential, social/family, and emotional domains. Patients who scored lower in physical well-being had higher scores in the symptom domain. Patient scores in the medical care domain were similar for each ECOG category. The results of this study support the subscale's use in assessing quality of life and the outcomes of palliative treatment for cancer patients in their last six months of life. ^

Effects of galectin-1 and galectin-3 expression on prostate cancer cell adhesion, differentiation, proliferation, and tumorigenicity

The vertebrate $\beta$-galactoside-binding lectins galectin-1 and galectin-3 have been proposed to function in diverse cellular processes such as adhesion, proliferation, differentiation, and tumorigenesis. Experiments were initiated to further study the functional properties of these molecules. A prostate cancer cell line, LNCaP, was identified which expressed neither galectin. This line was stably transfected with cDNA for either galectin-1 or galectin-3. The resultant clones were used to study effects on critical cell processes. LNCaP cells expressing galectin-1 on the surface were found to bind more rapidly than control lines to the human extracellular matrix proteins laminin and fibronectin, although overall binding was not increased. To analyze effects on differentiation, LNCaP cells were studied which had either been transfected with galectin-1 or which had been induced to express endogenous galectin-1 by treatment with the differentiation agent sodium butyrate. In both cases, cells displayed a slower rate of growth and increased rate of apoptosis. A transient decrease in expression of prostate specific antigen was seen in the butyrate treated cells but not in the transfected cells. To investigate the role of galectins in the process of malignant transformation and progression, immunohistochemical analysis was performed on formalin-fixed, paraffin-embedded sections of human prostate tissue, the premalignant lesion prostatic intraepithelial neoplasia, primary adenocarcinoma of the prostate, and foci of metastatic prostate cancer. Galectin-1 expression was relatively constant throughout in contrast to galectin-3 which demonstrated significantly less expression in primary and metastatic tumors. LNCaP cells transfected with galectin-3 cDNA displayed lower proliferation rates, increased spontaneous apoptosis, and G1 growth phase arrest compared to controls. Four of six galectin-3 lines tested were less tumorigenic in nude mice than controls. The following conclusions are drawn regarding the role of galectin-1 and galectin-3 expression in the context of prostate cancer: (1) galectin-1 may participate in the early stages of cancer cell adhesion to extracellular matrix proteins; (2) galectin-1 expression results in a differentiated phenotype and may contribute to differentiation induction by butyrate; (3) galectin-3 expression correlates inversely with prostate cell tumorigenesis and prostate cancer metastasis. ^

Study of retinoic acid signaling in cancer cells: Cloning and characterization of retinoic acid responsive genes

Retinoids such as all-trans-retinoic acid (ATRA) are promising agents for cancer chemoprevention and therapy. ATRA can cause growth inhibition, induction of differentiation and apoptosis of a variety of cancer cells. These effects are thought to be mediated by nuclear retinoids receptors which are involved in ligand-dependent transcriptional activation of downstream target genes. Using differential display, we identified several retinoic acid responsive genes in the head and neck squamous carcinoma cells and lung cancer cells, including tissue type transglutaminase, cytochrome P450-related retinoic acid hydroxylase, and a novel gene, designated RAIG1. RAIG1 has two transcripts of 2.4 and 6.8 kbp, respectively, that are generated by alternative selection of polyadenylation sites. Both transcripts have the same open reading frame that encodes a protein comprised of 357 amino acid residues. The deduced RAIG1 protein sequence contains seven transmembrane domains, a signature structure of G protein-coupled receptors. RAIG1 mRNA is expressed at high level in fetal and adult lung tissues. Induction of RAIG1 expression by ATRA is rapid and dose-dependent. A fusion protein of RAIG1 and the green fluorescent protein was localized in the cell surface membrane and perinuclear vesicles in transiently transfected cells. The locus for RAIG1 gene was mapped to a region between D12S358 and D12S847 on chromosome 12p12.3-p13. Our study of the novel retinoic acid induced gene RAIG1 provide evidence for a possible interaction between retinoid and G protein signaling pathways.^ We further examined RAIG1 expression pattern in a panel of 84 cancer cell lines of different origin. The expression level varies greatly from very high to non-detectable. We selected a panel of different cancer cells to study the effects of retinoids and other differentiation agents. We observed: (1) In most cases, retinoids (including all-trans retinoic acid, 4HPR, CD437) could induce the expression of RAIG-1 in cells from cancers of the breast, colon, head and neck, lung, ovarian and prostate. (2) Compare to retinoids, butyrate is often a more potent inducer of RAIG-1 expression in many cancer cells. (3) Butyrate, Phenylacetate butyrate, (R)P-Butyrate and (S)P-Butyrate have different impact on RAIG1 expression which varies among different cell lines. Our results indicate that retinoids could restore RAIG1 expression that is down-regulated in many cancer cells.^ A mouse homologous gene, mRAIG1, was cloned by 5$\sp\prime$ RACE reaction. mRAIG1 cDNA has 2105 bp and shares 63% identity with RAIG1 cDNA. mRAIG1 encodes a polypeptide of 356 amino acid which is 76% identity with RAIG1 protein. mRAIG1 protein also has seven transmembrane domains which are structurally identical to those of RAIG1 protein. Only one 2.2 kbp mRAIG1 transcript could be detected. The mRAIG1 mRNA is also highly expressed in lung tissue. The expression of mRAIG1 gene could be induced by ATRA in several mouse embryonal carcinoma cells. The induction of mRAIG1 expression is associated with retinoic acid-induced neuroectoderm differentiation of P19 cells. Similarity in cDNA and protein sequence, secondary structure, tissue distribution and inducible expression by retinoic acid strongly suggest that the mouse gene is the homologue of the human RAIG1 gene. ^

Effects of butyrate on the colon cancer cell phenotype-chemosensitization and upregulation of proteins implicated in cancer progression

Colon cancer is the second leading cause of cancer mortality in the U.S. Surgery is the only truly effective human colon cancer (HCC) therapy due to marked intrinsic drug resistance. The inefficacy of therapies developed for metastatic HCC suggests that advances in colon cancer chemoprevention and chemotherapy will be needed to reduce HCC mortality. The dietary fiber metabolite butyrate (NaB) is a candidate cancer chemopreventive agent that inhibits growth, promotes differentiation and stimulates apoptosis of HCC cells. Epidemiological and experimental studies suggest that dietary fiber protects against the development of HCC, however, recent large prospective trials have not found significant protection. ^ The first central hypothesis of this dissertation project is that the diversity of phenotypic changes induced by NaB in HCC cells includes molecular alterations that oppose its chemopreventive action and thereby limit its efficacy. We investigated the effect of NaB on the expression/activity of epidermal growth factor receptor (EGFR) and cyclooxygenase-2 (COX-2) in HCC HT29 cells. NaB treatment induced a 13-fold increase in EGFR expression in concert with its chemopreventive action in vitro, i.e., induction of growth suppression and G1 arrest, apoptosis and a differentiated phenotype. NaB-induced EGFR was active based on multiple lines of evidence. The EGFR was: (1) heavily phosphorylated at Tyrosine (P-Tyr); (2) associated with the cytoskeleton; (3) localized at the cell surface, and activated in response to EGF; and (4) NaB treatment of the cells induced activation of the EGFR effector Erk1/2. NaB treatment also induced a 7-fold increase in COX-2 expression. The NaB-induced COX-2 was active based on significantly increased PGE2 production. ^ The second central hypothesis is that NaB treatment would render HCC cells more chemosensitive to chemotherapy agents based on the increased apoptotic index induced by NaB. NaB treatment chemosensitized HT29 cells to 5-FU and doxorubicin, despite increases in the expression of P-glycoprotein and a related drug resistance protein (MRP). ^ These results raise the intriguing possibility that the chemopreventive effects of fiber may require concomitant treatment with EGFR and/or COX-2 inhibitors. Similarly, NaB may be a rational drug to combine with existing chemotherapeutic agents for the management of advanced HCC patients. ^

Delineation of a novel genetic region at 5q11 harboring tumor suppressor gene(s) and identification of the telomeric DNA as a marker for human prostate cancer

Prostate cancer is the most commonly diagnosed cancer and the second leading cause of cancer mortality in American men. The distinction between those cases of prostate cancer destined to progress rapidly to lethal metastatic disease and those with little likelihood of causing morbidity and mortality is a major goal of current research. Some type of diagnostic method is urgently needed to identify which histological prostate cancers have completed the progression to a stage that will produce a life-threatening disease, thus requiring immediate therapeutic intervention. The objectives of this dissertation are to delineate a novel genetic region harboring tumor suppressor gene(s) and to identify a marker for prostate tumorigenesis. I first established an in vitro cell model system from a human prostate epithelial cells derived from tissue fragments surrounding a prostate tumor in a patient with prostatic adenocarcinoma. Since chromosome 5 abnormality was present in early, middle and late passages of this cell model system, I examined long-term established prostate cancer cell lines for this chromosome abnormality. The results implicated the region surrounding marker D5S2068 as the locus of interest for further experimentation and location of a tumor suppressor gene in human prostate cancer. ^ Cancer is a group of complex genetic diseases with uncontrolled cell; division and prostate cancer is no exception. I determined if telomeric DNA, and telomerase activity, alone or together, could serve as biomarkers of prostate tumorigenesis. I studied three newly established human prostate cancer cell lines and three fibroblast cell cultures derived from prostate tissues. In conclusion, my data reveal that in the presence of telomerase activity, telomeric repeats are maintained at a certain optimal length, and analysis of telomeric DNA variations might serve as early diagnostic and prognostic biomarkers for prostate cancer. (Abstract shortened by UMI.)^

Prophylactic mastectomy and oophorectomy for women at risk of breast and ovarian cancer: Incorporating preferences in a decision analysis

The discoveries of the BRCA1 and BRCA2 genes have made it possible for women of families with hereditary breast/ovarian cancer to determine if they carry cancer-predisposing genetic mutations. Women with germline mutations have significantly higher probabilities of developing both cancers than the general population. Since the presence of a BRCA1 or BRCA2 mutation does not guarantee future cancer development, the appropriate course of action remains uncertain for these women. Prophylactic mastectomy and oophorectomy remain controversial since the underlying premise for surgical intervention is based more upon reduction in the estimated risk of cancer than on actual evidence of clinical benefit. Issues that are incorporated in a woman's decision making process include quality of life without breasts, ovaries, attitudes toward possible surgical morbidity as well as a remaining risk of future development of breast/ovarian cancer despite prophylactic surgery. The incorporation of patient preferences into decision analysis models can determine the quality-adjusted survival of different prophylactic approaches to breast/ovarian cancer prevention. Monte Carlo simulation was conducted on 4 separate decision models representing prophylactic oophorectomy, prophylactic mastectomy, prophylactic oophorectomy/mastectomy and screening. The use of 3 separate preference assessment methods across different populations of women allows researchers to determine how quality adjusted survival varies according to clinical strategy, method of preference assessment and the population from which preferences are assessed. ^

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. ^

4HPR-X radiation mechanisms of interactions in non-small cell lung cancer (NSCLC) cells in vitro

Lung cancer is the leading cause of cancer death. However, poor survival using conventional therapies fuel the search for more rational interventions. The objective of this study was to design and implement a 4HPR-radiation interaction model in NSCLC, employing a traditional clinical modality (radiation), a relatively new, therapeutically unexplored agent (4HPR) and rationally combining them based on molecular mechanistic findings pertaining to their interactions. To test the hypothesis that 4HPR sensitizes cells to radiation-induced cell death via G2+M accumulation, we designed a working model consisting of H522 adenocarcinoma cells (p53, K-ras mutated) derived from an NSCLC patient; 4HPR at concentrations up to 10 μM; and X radiation up to 6 Gy generated by a patient-dedicated Phillips RT-250 X ray unit at 250 KV, 15 mA, 1.85 Gy/min. We found that 4HPR produced time- and dose-dependent morphological changes, growth inhibition, and DNA damage-inducing enhancement of reactive oxygen species. A transient G2+M accumulation of cells maximal at 24 h of continuous 4HPR exposure was used for irradiation time scheduling. Our data demonstrated enhanced cell death (both apoptotic and necrotic) in irradiated cells pre-treated with 4HPR versus those with either stressor alone. 4HPR's effect of increased NSCLC cells' radioresponse was confirmed by clonogenic assay. To explore these practical findings from a molecular mechanistic perspective, we further investigated and showed that levels of cyclin B1 and p34cdc2 kinase—both components of the mitosis promoting factor (MPF) regulating the G2/M transition—did not change following 4HPR treatment. Likewise, cdc25C phosphatase was not altered. However, enhanced p34cdc2 phosphorylation on its Thr14Tyr15 residues—indicative of its inactivation and increased expression of MPF negative regulators chk1 and wee1 kinases—were supportive of explaining 4HPR-treated cells' accumulation. Hence, p34cdc2 phosphorylation, chk1, and wee1 warrant further evaluation as potential molecular targets for 4HPR-X radiation combination. In summary, we (1) demonstrated that 4HPR not only induces cell death by itself, but also increases NSCLC cells' subsequent radioresponse, indicative of potential clinical applicability, and (2) for the first time, shed light on deciphering 4HPR-X radiation molecular mechanisms of interaction, including the finding of 4HPR's role as a p34cdc2 inactivator via Thr14Tyr15 phosphorylation. ^