Role of dietary polyamines in a phase III clinical trial of difluoromethylornithine (DFMO) and sulindac for prevention of sporadic colorectal adenomas.

BACKGROUND: The polyamine-inhibitory regimen difluoromethylornithine (DFMO)+sulindac has marked efficacy in preventing metachronous colorectal adenomas. Polyamines are synthesised endogenously and obtained from dietary sources. Here we investigate dietary polyamine intake and outcomes in the DFMO+sulindac colorectal adenoma prevention trial. METHODS: Dietary polyamine data were available for 188 of 267 patients completing the study. Total dietary polyamine content was derived by the sum of dietary putrescine, spermine and spermidine values and categorised into two groups: highest (>75-100%) vs the lower three quartiles (0-25, 25-50 and 50-75%). Baseline tissue polyamine concentration and ODC1 genotype were determined. Logistic regression models were used for risk estimation. RESULTS: A significant interaction was detected between dietary polyamine group and treatment with regard to adenoma recurrence (P=0.012). Significant metachronous adenoma risk reduction was observed after DFMO+sulindac treatment in dietary polyamine quartiles 1-3 (risk ratio (RR) 0.19; 95% confidence interval (CI) 0.08-0.42; P<0.0001) but not in quartile 4 (RR 1.51; 95% CI 0.53-4.29; P=0.44). However, a lower number of events in the placebo group within dietary quartile 4 confound the aforementioned risk estimates. CONCLUSION: These preliminary findings reveal complex relationships between diet and therapeutic prevention, and they support further clinical trial-based investigations where the dietary intervention itself is controlled.

Antagonism of p66shc by melanoma inhibitory activity.

The p66shc protein governs oxidant stress and mammalian lifespan. Here, we identify melanoma inhibitory activity (MIA), a protein secreted by melanoma cells, as a novel binding partner and antagonist of p66shc. The N-terminal collagen homology-2 (CH2) domain of p66shc binds to the Src Homology-3 (SH3)-like domain of MIA in vitro. In cells, ectopically expressed MIA and p66shc colocalize and co-precipitate. MIA also co-precipitates with the CH2 domain of p66shc in vivo. MIA expression in vivo suppresses p66shc-stimulated increase in endogenous hydrogen peroxide (H(2)O(2)), and inhibits basal and H(2)O(2)-induced phosphorylation of p66shc on serine 36 and H(2)O(2)-induced death. In human melanoma cells expressing MIA, endogenous MIA and p66shc co-precipitate. Downregulation of MIA in melanoma cells increases basal and ultraviolet radiation (UVR)-induced phosphorylation of p66shc on serine 36, augments endogenous H(2)O(2) levels, and increases their susceptibility to UVR-induced death. These findings show that MIA binds to p66shc, and suggest that this interaction antagonizes phosphorylation and function of p66shc.

Rationale for, and design of, a clinical trial targeting polyamine metabolism for colon cancer chemoprevention.

Polyamine metabolic genes are downstream targets of several genes commonly mutated in colon adenomas and cancers. Inhibitors of ornithine decarboxylase, such as difluoromethylornithine (DFMO), and agents that stimulate polyamine acetylation and export, such as non-steroidal anti-inflammatory drugs (NSAIDS), act at least additively to arrest growth in human cell models and suppress intestinal carcinogenesis in mice. These preclinical studies provided the rationale for colon cancer prevention trials in humans. A Phase IIb clinical study comparing the combination of DFMO and the NSAID sulindac versus placebo was conducted. Endpoints were colorectal tissue polyamine and prostaglandin E2 contents and overall toxicity to participants. Participants in the Phase IIb study served as a vanguard for a randomized, placebo-controlled prospective Phase III trial of the combination of DFMO and sulindac with the primary study endpoint the prevention of colon polyps. Seventy percent of participants will have completed the three years of treatment in December 2006.

HPV infection and number of lifetime sexual partners are strong predictors for 'natural' regression of CIN 2 and 3.

The aim of this paper was to evaluate the factors that predict regression of untreated CIN 2 and 3. A total of 93 patients with colposcopic persistent CIN 2 and 3 lesions after biopsy were followed for 6 months. Human papillomavirus (HPV) types were determined by polymerase chain reaction at enrolment. We analysed the biologic and demographic predictors of natural regression using univariate and multivariate methods. The overall regression rate was 52% (48 out of 93), including 58% (22 out of 38) of CIN 2 and 47% (26 out of 55) of CIN 3 lesions (P=0.31 for difference). Human papillomavirus was detected in 84% (78 out of 93) of patients. In univariate analysis, 80% (12 out of 15) of lesions without HPV regressed compared to 46% (36 out of 78) of lesions with HPV infection (P=0.016). Women without HPV and those who had a resolution of HPV had a four-fold higher chance of regression than those with persistent HPV (relative odds=3.5, 95% CI=1.4-8.6). Women with five or fewer lifetime sexual partners had higher rates of regression than women with more than five partners (P=0.003). In multivariate analysis, HPV status and number of sexual partners remained as significant independent predictors of regression. In conclusion, HPV status and number of lifetime sexual partners were strongly predictive of regression of untreated CIN 2 and 3.

A randomized, double blind, Phase III trial using oral beta-carotene supplementation for women with high-grade cervical intraepithelial neoplasia.

To evaluate the effect of daily beta-carotene (30 mg) versus placebo over a 2-year period on cervical intraepithelial neoplasia (CIN) 2 and 3 lesions. Human papillomavirus (HPV) typing was done to determine whether lesion regression was related to HPV. Micronutrient levels were measured to determine whether levels were predictive of regression. Variables that influence the risk of HPV infection and CIN, such as cigarette smoking and sexual behavior, were evaluated. Women were randomized to beta-carotene or placebo, with cytology and colposcopy every 3 months. Cervical biopsies were performed before treatment and after 6 and 24 months to evaluate response. Persistence of or progression to CIN 3 resulted in removal from the study, whereas treatment continued for 2 years on all others. The presence and type of HPV was determined by PCR. Response was defined as an improvement in CIN by 2 grades. Mantel-Haenszel chi(2) test was used to analyze response to treatment. Fisher's exact test was used to determine the effect of HPV and CIN grade on response Wilcoxon's rank-sum tests were used to compare micronutrient levels between groups. Twenty-one of 124 enrolled women were not randomized because they either moved, became pregnant, voluntarily withdrew, or the pathological review of their initial cervical biopsies did not confirm CIN 2 or 3. Of the remaining 103 women, 33 experienced lesion regression, 45 had persistent or progressive disease, and 25 women did not complete the study and were considered nonresponders in the final analysis. The overall regression rate (32%) was similar between treatment arms and when stratified for CIN grade. Data on 99 women with HPV typing showed that 77% were HPV-positive and 23% HPV-negative at enrollment. HPV-positive lesions were subdivided into indeterminate-, low-, and high-risk categories; the response rate was highest for women with no HPV detected (61%), lower for indeterminate/low-risk (30%), and lowest for high-risk (18%; P =.001). CIN regression was negatively correlated with retinol levels. In conclusion, beta-carotene does not enhance the regression of high-grade CIN, especially in HPV-positive subjects.

Aberrant redox regulation in human metastatic melanoma cells compared to normal melanocytes.

Melanocytes and melanoma cells contain melanin, a complex polymer that modulates redox changes in these cells. Relative intracellular hydrogen peroxide levels measured by dichlorodihydrofluorescein are similar in the two cell types, but the levels of superoxide anion measured by dihydroethidium were markedly increased in melanoma cells. Chelator-induced oxidative stress is efficiently suppressed by melanocytes without substantial recruitment of the transcription factors NF-kappaB and AP-1 as measured by electrophoretic mobility shift assay and quantitated by densitometry or by a change in frequency of apoptosis as determined by annexin V binding. In contrast, NF-kappaB in melanoma cells is strongly recruited by changes in redox status and exhibits a correlative relationship to intracellular hydrogen peroxide (but not superoxide anion). However, the response of the NF-kappaB pathway to intracellular hydrogen peroxide is anomalous, including downregulation of p65 and IkappaBalpha RNA expression (Northern blot). Additionally, recruitment of AP-1 binding in melanoma cells was directly correlated with intracellular levels of superoxide anion (but not hydrogen peroxide). Neither the degree of NF-kappaB nor AP-1 binding in melanoma cells was related to the frequency of apoptosis. The responsiveness of NF-kappaB and AP-1 recruitment to intracellular levels of hydrogen peroxide and superoxide anion without concomitant control of apoptosis provides a general mechanism by which these cells can escape noxious injury (e.g., chemotherapy). The marked enhancement of apoptosis in melanoma cells by chelators indicates, however, that this alteration can be circumvented and offers a unique therapeutic window to explore.

Redox regulation in human melanocytes and melanoma.

The human melanocyte is continuously exposed to intrinsic and extrinsic sources of reactive biochemical species, but is finely tuned via the intrinsic anti-oxidant and radical properties of melanin to suppress the build-up of an altered redox phenotype. We propose that this control is lost during melanomagenesis and inappropriate redox-sensitive transcriptional factor activations occur which result in enhancement of an anti-apoptotic phenotype in the transformed cell. This conceptual framework offers testable steps to determine the role of redox alterations in the carcinogenic evolution, prevention and treatment of melanoma and other diseases of the melanocyte.

Effects of difluoromethylornithine chemoprevention on audiometry thresholds and otoacoustic emissions.

OBJECTIVES: To determine the effects of long-term, low-dose difluoromethylornithine (DFMO) on audiometric thresholds and distortion product otoacoustic emission (DPOAE) levels in humans. DESIGN: A prospective, randomized, placebo-controlled phase 2 clinical trial of DFMO in participants with a prior adenomatous colonic polyp. SETTING: Academic tertiary care referral center. PARTICIPANTS: One hundred twenty-three volunteer subjects with colorectal polyps and normal hearing for the frequencies 250 through 2000 Hz. INTERVENTIONS: Subjects were randomized to receive placebo or oral DFMO at daily dosages between 0.075 and 0.4 g/m(2) of body surface area for 12 months. OUTCOME MEASURES: Pure-tone audiometric thresholds for the frequencies 250, 500, 1000, 2000, 3000, 4000, 6000, and 8000 Hz and DPOAE levels were measured at baseline and 1, 3, 6, 9, and 12 months after starting treatment with DFMO or placebo and 3 months after cessation of treatment if there was a suggestion of possible changes at the 12-month measurement. RESULTS: At these low dosages, there was little evidence for shifts in auditory pure-tone thresholds, and there were no statistically significant shifts in DPOAE levels. For auditory pure-tone thresholds, there was a subtle, approximately 2- to 3-dB hearing level decrease in hearing sensitivity for the 2 higher DFMO dosages, but only at the 2 lowest frequencies, 250 and 500 Hz. CONCLUSIONS: Administration of low-dose DFMO for 12 months did not produce hearing loss, in contrast to prior studies that used higher dosages.

Executive Summary of the National Cancer Institute Workshop: Highlights and recommendations.

Prostate cancer chemoprevention represents a relatively new and promising strategy for reducing the immense public health burden of this devastating cancer of men in the United States and Western societies. Chemoprevention is defined as the administration of agents (drugs, biologics, and natural products) that modulate (inhibit) one or more steps in the multistage carcinogenesis process culminating in invasive adenocarcinoma of the prostate. In 2000, there were an estimated 170,000 new cases of prostate cancer and 31,000 deaths in the United States. During the past decade, the National Cancer Institute (NCI) organized the chemoprevention research program and began testing the first generation of promising agents (eg, 4-(hydroxy)-fenretinide [4-HPR], difluoromethylornithine [DFMO], antiandrogens) in high-risk cohorts and launched the first-large scale US phase 3 primary prevention trial, known as Prostate Cancer Prevention Trial (PCPT-1), in 18,000 average-risk men (age more than 55 years and prostate-specific antigen [PSA] less than 3 ng/mL) treated for 7 years with finasteride or placebo. In the summer of 1998, the NCI Prostate Cancer Progress Review Group (PRG) Report to the director of NCI was published in response to the leadership of the prostate cancer advocacy community in conjunction with Congress. To further elucidate and address critical issues identified in this report and to develop a research agenda for the newly created Prostate and Urologic Cancer Research Group in the Division of Cancer Prevention at NCI, the NCI organized the workshop "New Clinical Trial Strategies for Prostate Cancer Chemoprevention." The major objectives were to promote understanding and cooperation among the NCI, US Food and Drug Administration (FDA), academia, pharmaceutical industry, and the public regarding new opportunities for clinical prevention trials for prostate cancer. The workshop was divided into three concurrent breakout panels and a fourth joint integrative panel. The workshop addressed multiple key areas identified in the PRG report in the following panels: (1) Molecular Targets and Promising Agents in Clinical Development; (2) Intermediate Endpoint Biomarkers for Prevention Trials; (3) High-Risk Study Populations for Prevention Trials, and (4) Preventive Clinical Trial Designs and Regulatory Issues. Expert panelists were drawn from leading academic, pharmaceutical, and government scientists in basic research and clinical investigation. Key pharmaceutical, biotechnology, academic, and National Institutes of Health scientists presented overviews of their new agents and products in clinical development (representing the next generation of promising agents). Senior FDA physicians from the Center for Drugs and Center for Biologics presented on current standards for new drug and biologic approval for chemoprevention efficacy. Some of the key topics included recent advances in the state of knowledge of promising agents in the clinic based on molecular targets as well as bottlenecks in drug development for pharmaceutical sponsors; strategic modulable biomarkers that can serve as primary endpoints in phase 1/2 trials to assess preventive efficacy; high-risk cohorts with precancer (high-grade prostatic intraepithelial neoplasia) and representative clinical trial designs that are ready for immediate translation into efficient prevention trials, such as Bayesian sequential monitoring for early assessment of biologic activity and factorial designs for assessment of multiagent combinations. Finally, each expert panel generated recommendations for areas of future research emphasizing opportunities and infrastructure needs.

Potential target populations and clinical models for testing chemopreventive agents.

Target populations for chemoprevention trials should include those at higher than average risk for the development of prostate cancer as defined by explicit epidemiologic and genetic criteria. Such populations include a "primary prevention" group without histologic or clinical evidence of cancer, and several clinical models of "secondary prevention," including those with clinically evident disease prior to definitive therapy and those at high risk of recurrence after therapy based on histological or biochemical status. Each risk group and clinical model has potential advantages and disadvantages, and the mechanisms that underlie disease development and progression in each group may be unique. These observations give rise to many potential clinical trials of specific agents. These trials should also include collection of data on potentially confounding influences on disease development and progression.

African American men and hereditary/familial prostate cancer: Intermediate-risk populations for chemoprevention trials.

The risk of prostate cancer diagnosis among African Americans is 66% greater than among European American men. For African Americans with a family history of hereditary prostate cancer the increased risk of diagnosis is even greater. Thus, this population should be a prime target for chemoprevention strategies. In addition to the higher incidence of prostate cancer among African Americans compared with other populations, the mortality of prostate cancer among this high-risk population is significantly greater than 100% compared with other populations, thus further demonstrating the need for chemoprevention in this target population. Autopsy studies and clinical findings support the argument that prostate cancer exhibits more aggressive biological behavior and perhaps more rapid growth among African Americans compared with European Americans. It is hypothesized that genetic and epigenetic factors may be responsible for a more rapid growth rate among African Americans compared with other populations. Accumulating evidence indicates that a diet high in fat content is closely associated with prostate cancer progression. Investigators have reported that fat intake and percentage of energy from fat were highest in African Americans, followed by European Americans, Japanese Americans, and Chinese Americans. In conclusion, African Americans are an important target population to include in chemoprevention trials that include dietary factors as preventive agents.

Development of difluoromethyl-ornithine and Bowman-Birk inhibitor as chemopreventive agents by assessment of relevant biomarker modulation: some lessons learned.

A major goal in the development of chemopreventive agents has been to develop markers that reflect the underlying process of carcinogenesis and which are modulatable by the agent under study. An important application of such markers will be to select cohorts that are at elevated risk for cancer development, which should allow use of smaller sample sizes in definitive phase III trials as well as shorter duration (and lower cost), without loss of statistical power. Susceptibility and surrogate end-point biomarkers are particularly important in this respect. Intermediate markers are probably best assessed in terms of proportionate rather than relative risk. The systematic development of difluoromethylornithine for use in chemoprevention against human cancer has involved pilot, phase IIa and IIb trials using participants with prior colonic polyps as the study group. A unique feature of the phase IIa study was the use of a dose de-escalation design which allowed selection of the lowest effective non-toxic dose of difluoromethylornithine. The phase IIb trial now in progress is using a combination of sulindac with difluoromethylornithine; the rationale for selection of markers for this study and for a randomized phase III registration trial is discussed. We also review the findings in phase I and IIa trials of Bowman-Birk inhibitor concentrate, in which patients with measurable oral leukoplakia are the study group.

RelA, p50 and inhibitor of kappa B alpha are elevated in human metastatic melanoma cells and respond aberrantly to ultraviolet light B.

Metastatic melanomas are typically resistant to radiation and chemotherapy. The underlying basis for this phenomenon may result in part from defects in apoptotic pathways. Nuclear factor kappa B (NFkappaB) has been shown to control apoptosis in many cell types and normally functions as an immediate stress response mechanism that is rigorously controlled by multiple inhibitory complexes. We have previously shown that NFkappaB binding is elevated in metastatic melanoma cells relative to normal melanocytes. In the current study, Western blot analysis showed that, compared with normal melanocytes, melanoma cell lines have higher nuclear levels of the NFkappaB subunits p50 (7-fold) and RelA (5-10-fold). In response to tumor necrosis factor-alpha (TNFalpha), both melanocytes and melanoma cells showed increased nuclear p50 and RelA levels, but levels in melanoma cells remained higher than in melanocytes. We also found that melanoma cells expressed higher cytoplasmic levels of RelA, p105/p50 and the inhibitory protein, inhibitor of kappa B alpha (IkappaBalpha) than melanocytes. To directly test whether RelA expression has an impact on melanoma cell survival, we used antisense RelA phosphorothioate oligonucleotides and found that melanoma cell viability was significantly decreased compared with untreated or control cultures. The constitutive activation of NFkappaB in metastatic melanoma cell cultures may, therefore, support an inappropriate cell survival pathway that can be therapeutically manipulated.

Development of Bowman-Birk inhibitor for chemoprevention of oral head and neck cancer.

Leukoplakia in the oral cavity has been used as a putative surrogate marker of head and neck cancer development. A class of chemoprevention compounds, called protease inhibitors, has been shown in vitro and in animal models to effectively suppress premalignant lesions. Bowman-Birk inhibitor (BBI) is a protease inhibitor derived from soybeans that has demonstrated chemoprevention activity in many in vitro and animal systems, including the hamster cheek pouch model. Pilot, Phase I and Phase IIa studies of Bowman-Birk Inhibitor in patients with oral leukoplakia have demonstrated no detectable side effects. In the Phase IIa trial, changes in the protease activity in oral mucosal cells after BBI Concentratec (BBIC) treatment correlated with the changes in neu protein levels. Additionally, evidence for a dose-related treatment effect of BBIC on oral leukoplakia was demonstrated. These results indicate that BBIC should be investigated for chemopreventive activity in a randomized clinical trial.

Challenges posed by non-random missing quality of life data in an advanced-stage colorectal cancer clinical trial.

Effects of variations in agent, dose, and route of treatment administration on patient reported quality of life (QOL) were examined for 279 patients enrolled on a seven-arm randomized clinical trial (S8905) of 5-FU and its modulation for advanced colorectal cancer. Patients completed QOL questionnaires at randomization and weeks 6, 11, and 21 post-randomization with five QOL endpoints considered primary: three treatment-specific symptoms (stomatitis, diarrhea, and hand/foot sensitivity); physical functioning; and emotional functioning. Patient compliance with the QOL assessment schedule was good, supporting the feasibility of including QOL measures in cooperative group trials. However, death and deteriorating health produced substantial missing data. Cross-sectional analyses indicated that the seven therapeutic arms did not differ in their impact on QOL. Unfortunately, longitudinal analyses of the QOL data were inappropriate given non-random missing data. Graphical presentation of non-random missing data identified the seriousness of this problem and its effect on potential conclusions about QOL during treatment. This problem appears to be particularly challenging in the context of advanced-stage disease. Failure to recognize the presence of non-random missing data can lead to serious overestimates of patient QOL over time.