Correction--malignant glioma.
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Antineoplastic Agents↗
Biomedical subjects
F L Meyskens
Publications and source records attributed to F L Meyskens.
Risk factors for lung cancer and for intervention effects in CARET, the Beta-Carotene and Retinol Efficacy Trial.
BACKGROUND: Evidence has accumulated from observational studies that people eating more fruits and vegetables, which are rich in beta-carotene (a violet to yellow plant pigment that acts as an antioxidant and can be converted to vitamin A by enzymes in the intestinal wall and liver) and retinol (an alcohol chemical form of vitamin A), and people having higher serum beta-carotene concentrations had lower rates of lung cancer. The Beta-Carotene and Retinol Efficacy Trial (CARET) tested the combination of 30 mg beta-carotene and 25,000 IU retinyl palmitate (vitamin A) taken daily against placebo in 18314 men and women at high risk of developing lung cancer. The CARET intervention was stopped 21 months early because of clear evidence of no benefit and substantial evidence of possible harm; there were 28% more lung cancers and 17% more deaths in the active intervention group (active = the daily combination of 30 mg beta-carotene and 25,000 IU retinyl palmitate). Promptly after the January 18, 1996, announcement that the CARET active intervention had been stopped, we published preliminary findings from CARET regarding cancer, heart disease, and total mortality. PURPOSE: We present for the first time results based on the pre-specified analytic method, details about risk factors for lung cancer, and analyses of subgroups and of factors that possibly influence response to the intervention. METHODS: CARET was a randomized, double-blinded, placebo-controlled chemoprevention trial, initiated with a pilot phase and then expanded 10-fold at six study centers. Cigarette smoking history and status and alcohol intake were assessed through participant self-report. Serum was collected from the participants at base line and periodically after randomization and was analyzed for beta-carotene concentration. An Endpoints Review Committee evaluated endpoint reports, including pathologic review of tissue specimens. The primary analysis is a stratified logrank test for intervention arm differences in lung cancer incidence, with weighting linearly to hypothesized full effect at 24 months after randomization. Relative risks (RRs) were estimated by use of Cox regression models; tests were performed for quantitative and qualitative interactions between the intervention and smoking status or alcohol intake. O'Brien-Fleming boundaries were used for stopping criteria at interim analyses. Statistical significance was set at the .05 alpha value, and all P values were derived from two-sided statistical tests. RESULTS: According to CARET's pre-specified analysis, there was an RR of 1.36 (95% confidence interval [CI] = 1.07-1.73; P = .01) for weighted lung cancer incidence for the active intervention group compared with the placebo group, and RR = 1.59 (95% CI = 1.13-2.23; P = .01) for weighted lung cancer mortality. All subgroups, except former smokers, had a point estimate of RR of 1.10 or greater for lung cancer. There are suggestions of associations of the excess lung cancer incidence with the highest quartile of alcohol intake (RR = 1.99; 95% CI = 1.28-3.09; test for heterogeneity of RR among quartiles of alcohol intake has P = .01, unadjusted for multiple comparisons) and with large-cell histology (RR = 1.89; 95% CI = 1.09-3.26; test for heterogeneity among histologic categories has P = .35), but not with base-line serum beta-carotene concentrations. CONCLUSIONS: CARET participants receiving the combination of beta-carotene and vitamin A had no chemopreventive benefit and had excess lung cancer incidence and mortality. The results are highly consistent with those found for beta-carotene in the Alpha-Tocopherol Beta-Carotene Cancer Prevention Study in 29133 male smokers in Finland.
Anticarcinogenic Agents↗
Effects of a combination of beta carotene and vitamin A on lung cancer and cardiovascular disease.
BACKGROUND: Lung cancer and cardiovascular disease are major causes of death in the United States. It has been proposed that carotenoids and retinoids are agents that may prevent these disorders. METHODS: We conducted a multicenter, randomized, double-blind, placebo-controlled primary prevention trial -- the Beta Carotene and Retinol Efficacy Trial -- involving a total of 18,314 smokers, former smokers, and workers exposed to asbestos. The effects of a combination of 30 mg of beta carotene per day and 25,000 IU of retinol (vitamin A) in the form of retinyl palmitate per day on the primary end point, the incidence of lung cancer, were compared with those of placebo. RESULTS: A total of 388 new cases of lung cancer were diagnosed during the 73,135 person-years of follow-up (mean length of follow-up, 4.0 years). The active-treatment group had a relative risk of lung cancer of 1.28 (95 percent confidence interval, 1.04 to 1.57; P=0.02), as compared with the placebo group. There were no statistically significant differences in the risks of other types of cancer. In the active-treatment group, the relative risk of death from any cause was 1.17 (95 percent confidence interval, 1.03 to 1.33); of death from lung cancer, 1.46 (95 percent confidence interval, 1.07 to 2.00); and of death from cardiovascular disease, 1.26 (95 percent confidence interval, 0.99 to 1.61). On the basis of these findings, the randomized trial was stopped 21 months earlier than planned; follow-up will continue for another 5 years. CONCLUSIONS: After an average of four years of supplementation, the combination of beta carotene and vitamin A had no benefit and may have had an adverse effect on the incidence of lung cancer and on the risk of death from lung cancer, cardiovascular disease, and any cause in smokers and workers exposed to asbestos.
Aged↗
Randomized trial of adjuvant human interferon gamma versus observation in high-risk cutaneous melanoma: a Southwest Oncology Group study.
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Adult↗
Development of difluoromethylornithine as a chemoprevention agent for the management of colon cancer.
Experimental studies have demonstrated that carcinogenesis is a multistep process in which inappropriate proliferation of cells is a critical determinant. Polyamines support sustained growth and are highly regulated in all cells. The rate limiting enzyme for this pathway is ornithine decarboxylase (ODC), an enzyme that exhibits rapid turnover, and converts the amino acid ornithine to putrescine, which in turn is converted to the longer chain amines spermidine and spermine. In animal models of colon carcinogenesis, inhibition of ODC by difluoromethylornithine (DFMO), an enzyme-activated irreversible inhibitor, reduces the number and size of colon adenomas and carcinomas. DFMO was first ineffective when used clinically to treat acute leukemia or melanoma and caused clinically significant but reversible ototoxicity. Subsequently, we performed a series of analyses demonstrating that hearing loss was rare below a total cumulative dose of 150 gm/m2 and increased with total cumulative dose of DFMO. The hearing loss was reversible with rapid reversion to baseline hearing. We and others have conducted Phase IIa trials to determine the lowest dose at which DFMO can decrease colon mucosa polyamine content, and found that an oral dose as low as 0.25 gm/m2 per day (perhaps lower) decreases colon tissue putrescine content and lowers the spermidine/spermine ratio. We are currently conducting a long-term randomized Phase IIb trial which serially measures the long-term effect of several low doses (and placebo) of DFMO on sustaining polyamine depletion in colon mucosa, as well as carefully monitoring hearing by audiometry and other sophisticated tests.(ABSTRACT TRUNCATED AT 250 WORDS)
Anticarcinogenic Agents↗
Effects of vitamin A on survival in patients with chronic myelogenous leukemia: a SWOG randomized trial.
A national cooperative group trial was conducted in 153 patients with chronic myelogenous leukemia (CML) in chronic phase treated with oral pulse busulfan to determine if oral vitamin A can increase the time to blast crisis and enhance survival of patients. Patients diagnosed within 1 year and in the chronic phase of CML were randomized to receive oral pulse busulfan or the alkylator plus continuous oral vitamin A. Distributions of clinical progression and overall survival were estimated using the method of Kaplan and Meier. Associations of these endpoints with treatment and other patient characteristics were analyzed using the proportional hazards regression method of Cox. Both regimes were well tolerated. Patients in the busulfan plus vitamin A arm had somewhat longer durations of clinical progression-free survival (median 46 months) and overall survival (51 months) compared to those in the busulfan arm (medians 38 and 44 months). However, the differences were not statistically significant (one-tailed P = 0.11 for clinical progression-free survival, 0.081 for survival). After adjustment for significant factors identified in an additional exploratory multivariate analysis, risk of clinical progression or death was 53% (P = 0.022) greater and risk of death 60% (P = 0.014) greater among busulfan patients. Given the relatively large though non-significant difference between treatment arms, the limited statistical power of the study, and the likelihood that oral vitamin A may not be the most effective means of delivering retinoid therapy, we conclude that further investigation of retinoids in chronic phase CML is warranted.
Antineoplastic Agents, Alkylating↗
Prevention of cervical intraepithelial neoplasia and cervical cancer.
We review the current status of prevention trials in the management of cervical intraepithelial neoplasia (CIN) and cervical cancer. Two large, randomized controlled trials have shown that folic acid is inactive in reversing low to moderate grade CIN. A large randomized trial of locally applied beta-trans retinoic acid showed that the agent was effective in reversing moderate but not severe CIN. Results from a pilot trial involving 30 patients with CIN I (mild dysplasia) and CIN II (moderate dysplasia) indicate that beta-carotene can suppress CIN; a large ongoing randomized trial will answer the question more definitively.
Antioxidants↗
Evaluation and treatment of the patient with early melanoma.
In summary, prospective studies within the last 10 years have made a significant impact on our understanding of the natural history of early melanoma. Surgeons can now excise the melanoma with narrower and more selective margins that preserve function and cosmetic appearance. Early melanomas are now, and will continue to be the most common presentation of this cutaneous malignancy. This reflects an enhanced awareness of the public and the medical community about the value of increased detection, and serious attempts at protection from intense ultra-violet light exposure. Current research is now focusing on the inherited forms of melanoma, the effects of ultra-violet light on melanocytes and the immune cells of the skin, and the molecular measurement of the abnormal cytogenetics seen in malignant melanocytes. These studies will allow physicians to detect a melanoma at an earlier and earlier time point in its natural history, and perhaps prevent or reverse the formation of melanoma early in life.
Humans↗
Chemoprevention of cervical cancer with folic acid: a phase III Southwest Oncology Group Intergroup study.
Several epidemiological reports and experimental investigations have suggested a preventive role for folic acid in the etiology of cervical cancer. The effect of p.o. folic acid supplementation on the natural history of cervical intraepithelial neoplasia (CIN) was evaluated in a multiinstitutional prospective, randomized, double-blind, placebo-controlled trial. Three hundred thirty-one women with biopsy-proven koilocytic atypia, mild CIN, or moderate CIN were randomized to receive oral folic acid (5 mg) or a similar-appearing placebo daily for 6 months following a 1-month run-in placebo period. Colposcopy, Papanicolaou smear, and serum vitamin levels (folate, retinol, alpha-tocopherol, beta-carotene, and retinyl palmitate) were monitored every 3 months. Demographic, medical, dietary, and sexual history data were obtained from personal interviews. The primary end point of the study was improvement in both Papanicolaou smear and colposcopic picture after 3 and 6 months of treatment as compared to the start of treatment. After 6 months of treatment there was no significant difference between the two study groups in the percentage of patients improved. Median serum folate levels in the treatment arm at 3 and 6 months (29.0 and 20.0 micrograms/dl) were significantly higher than those in the placebo arm (7.8 and 7.1 micrograms/dl, respectively). Mean serum levels of retinol, retinyl palmitate, alpha-tocopherol, and beta-carotene did not differ significantly between the two treatment arms. Our data support the conclusion that supplementation with folic acid (5 mg/day) does not enhance the regression of early epithelial abnormalities of the cervix.(ABSTRACT TRUNCATED AT 250 WORDS)
Administration, Oral↗
Dose de-escalation chemoprevention trial of alpha-difluoromethylornithine in patients with colon polyps.
BACKGROUND: alpha-Difluoromethylornithine (DFMO) is a potent inhibitor of carcinogenesis in experimental animal models. In these animal models, DFMO has been especially active in preventing carcinogen-induced epithelial cancers, including those of the skin, colon, breast, and urinary bladder. Although DFMO is known to exert its diverse biological effects by suppressing intracellular pools of the polyamines putrescine and spermidine, the precise mechanism by which polyamine depletion, induced by DFMO, suppresses carcinogenesis is unknown. PURPOSE: The specific aim of our study was to determine the lowest dose of DFMO that would deplete target tissue (colorectal mucosa) levels of these polyamines in humans who had undergone prior removal of colon polyps while producing minimal toxic effects. METHODS: A dose de-escalation chemoprevention trial of DFMO was conducted in 111 patients (36 female and 75 male) who were in generally good health, aged 39-79, and who had undergone colonoscopy for surgical removal of an adenomatous colon polyp greater than 3 mm within 5 years prior to entering the study. Groups of patients (12-20 patients per group) were orally treated with single, daily doses of DFMO ranging from 3.0 to 0.1 g/m2 for 4 weeks (28 days). Prior to initiation of DFMO treatment and at the end of treatment, six colorectal biopsy specimens were collected from each patient, along with serum samples. All biopsies were performed between 9 AM and noon to avoid possible effects of diurnal variations in laboratory end points. Samples for analysis of plasma DFMO levels were also collected during this time period on the day after the last day of drug administration. RESULTS: DFMO caused a decrease in both putrescine content and the ratio of spermidine to spermine for all dose groups down to 0.25 g/m2. Both putrescine content and the ratio of spermidine to spermine and changes in these parameters as a function of DFMO treatment decreased as a function of donor age. None of the 30 patients receiving either 0.25 or 0.5 g/m2 experienced any clinical ototoxicity in this trial. CONCLUSIONS: DFMO is both safe and effective in reducing colorectal mucosal polyamine contents when it is administered orally to patients at doses as low as 0.25 g/m2 for 28 days. No ototoxicity was observed at doses up to twice this amount. IMPLICATIONS: If DFMO is also found to be effective in suppressing polyamine contents in other target tissues, it may be useful in preventing a wide range of human epithelial cancers, including those of the prostate and breast.
Administration, Oral↗
Enhancement of regression of cervical intraepithelial neoplasia II (moderate dysplasia) with topically applied all-trans-retinoic acid: a randomized trial.
BACKGROUND: Retinoids enhance differentiation of most epithelial tissues. Epidemiologic studies have shown an inverse relationship between dietary intake or serum levels of vitamin A and the development of cervical dysplasia and/or cervical cancer. Pilot and phase I investigations demonstrated the feasibility of the local delivery of all-trans-retinoic acid (RA) to the cervix using a collagen sponge insert and cervical cap. A phase II trial produced a clinical complete response rate of 50%. PURPOSE: This randomized phase III trial was designed to determine whether topically applied RA reversed moderate cervical intraepithelial neoplasia (CIN) II or severe CIN. METHODS: Analyses were based on 301 women with CIN (moderate dysplasia, 151 women; severe dysplasia, 150 women), evaluated by serial colposcopy, Papanicolaou cytology, and cervical biopsy. Cervical caps with sponges containing either 1.0 mL of 0.372% beta-trans-RA or a placebo were inserted daily for 4 days when women entered the trial, and for 2 days at months 3 and 6. Patients receiving treatment and those receiving placebo were similar with respect to age, ethnicity, birth-control methods, histologic features of the endocervical biopsy specimen and koilocytotic atypia, and percentage of involvement of the cervix at study. Treatment effects were compared using Fisher's exact test and logistic regression methods. Side effects were recorded, and differences were compared using Fisher's exact test. RESULTS: RA increased the complete histologic regression rate of CIN II from 27% in the placebo group to 43% in the retinoic acid treatment group (P = .041). No treatment difference between the two arms was evident in the severe dysplasia group. More vaginal and vulvar side effects were seen in the patients receiving RA, but these effects were mild and reversible. CONCLUSIONS: A short course of locally applied RA can reverse CIN II, but not more advanced dysplasia, with acceptable local side effects. IMPLICATIONS: A derivative of vitamin A can reverse or suppress an epithelial preneoplasia, lending further support to the notion that chemoprevention of human cancer is feasible.
Administration, Intravaginal↗
Randomized trial of vitamin A versus observation as adjuvant therapy in high-risk primary malignant melanoma: a Southwest Oncology Group study.
PURPOSE: A national cooperative group trial was conducted in patients with early-stage cutaneous malignant melanoma to determine if oral vitamin A can increase disease-free survival or survival. PATIENTS AND METHODS: Two hundred forty-eight patients with completely resected melanoma of Breslow's thickness greater than 0.75 mm and clinically negative lymph nodes were randomized to oral vitamin A (100,000 IU/d) for 18 months or to observation. Patients were stratified by Breslow's thickness of primary lesion (0.76 to 1.50 mm, 1.51 to 3.00 mm, or > 3.00 mm), sex, and type of therapy (excision, excision plus node dissection, excision plus perfusion, or excision plus both). The median duration of follow-up observation of living patients is greater than 8 years. The relative risk (RR) in disease-free survival and overall survival in the treatment compared with the observation group was calculated using Cox proportional hazards models. RESULTS: Overall, there was no difference in disease-free survival or overall survival between the two groups. Examination of treatment by stratification interactions and subset analysis did not show any treatment-effect differences based on sex or type of therapy. There was also no difference between groups in disease-free survival based on Breslow's thickness of the primary lesion. Overall, 12% of patients who received vitamin A experienced grade 3 or 4 toxicities. CONCLUSION: Based on the lack of overall survival benefit, further evaluation of vitamin A as adjuvant therapy for melanoma does not appear warranted.
Administration, Oral↗
Alterations in gene expression and signal transductions in human melanocytes and melanoma cells.
The development of techniques to cultivate human primary melanocytes in vitro has provided the technical foundation for understanding the biology of this cell. Human melanocytes require various growth factors and agents for proliferation in vitro. These compounds activate two major signal transduction pathways: a calcium- and phospholipid-dependent (protein kinase C or PKC) pathway and a cyclic AMP (cAMP)-dependent (protein kinase A or PKA) pathway. Alterations in these signal transduction pathways coupled with changes in specific genes (protooncogenes, growth factors, and tumor suppressor genes) have been observed in human melanoma cells compared with normal melanocytes. Our own work indicates that loss in the expression of the PKC beta II isotype is a common, if not universal, alteration that occurs early in human melanocyte transformation. In this review, we concentrate on alterations in the signal transduction pathways in human melanocytes and melanoma cells and delineate how an understanding of these changes may allow us to understand the molecular mechanisms involved in human melanocyte transformation.
Cell Differentiation↗
Ventral mesencephalic and cortical transplants into the rat striatum display enhanced activity for neutral endopeptidase 24.11 ('enkephalinase'; CALLA).
A role for neutral endopeptidase 24.11 (NEP) in growth and development is supported by the demonstration that NEP hydrolyses and inactivates a number of peptide growth factors including atrial natriuretic peptide, endothelins, bombesin-like peptides, and opioid peptides, including the enkephalins. In the present study, suspensions of cells obtained from the ventral mesencephalon or cortex of rat embryos (ED14) were implanted into the striatum of the adult rat brain. Three to 15 weeks after transplantation the relative distribution of NEP-positive cellular elements was visualized histochemically. NEP staining in the transplants consistently appeared before NEP staining in the surrounding host striatum supporting a relative increase in NEP activity in the transplants. The NEP staining richly visualized cells of varying size and morphology which lacked the normal organization of the host striatum. The histochemical staining in the transplants and the surrounding host tissue was completely blocked by a 100 nM concentration of the selective NEP inhibitors phosphoramidon or JHF-26, supporting the exclusive localization of NEP by this method. NEP localization in the embryonic (ED14) cortex and ventral mesencephalon was also confirmed, suggesting one possible origin for the NEP-positive cells visualized in the transplants. Fluorescent double-labeling studies for NEP and glial fibrillary acidic protein (GFAP) or transforming growth factor alpha precursor (TGF alpha p) revealed the presence of rich glial labeling within the transplants for both GFAP and TGFap. NEP-labeled cells in the transplants were closely associated with glial elements, however, only occasional glial elements in the transplants stained for NEP; supporting a non-astrocytic localization for the NEP in the transplants. The marked enhancement of NEP staining in the transplants may have significance for controlling the rate or pattern of growth of the transplanted cells through inactivation of peptide growth factors produced by, or in response to, the transplants.
Animals↗
Protein kinase C beta expression in melanoma cells and melanocytes: differential expression correlates with biological responses to 12-O-tetradecanoylphorbol 13-acetate.
Normal human melanocytes require 12-O-tetradecanoylphorbol 13-acetate (TPA) for prolonged growth in vitro. In contrast, the growth of human malignant melanoma cells is often inhibited by TPA. In this study, we have confirmed and extended these observations. Since protein kinase C (PKC) is an important mediator of the effects of TPA, we have investigated the nature of this differential growth response by examining PKC expression and activity in primary cultures of human neonatal melanocytes and metastatic melanoma cell strains. PKC, when measured by immunoreactivity or a functional assay, was found to be more abundant in melanoma cells than in melanocytes. When specific isotypes were examined by Northern analysis, PKC-alpha and -epsilon were expressed in both melanocytes and melanoma. PKC-beta was expressed in melanocytes, but was undetectable by Northern analysis in 10 out of 11 melanoma cell strains. Southern analysis revealed that no gross deletions or rearrangements of the PKC-beta gene had occurred. These data suggest that down-regulation of the PKC-beta gene occurs frequently during the process of transformation of melanocytes. Furthermore, differential expression of PKC isotypes may explain the different effects of TPA on melanocyte and melanoma cell growth.
Blotting, Northern↗
Retinoids as anticancer agents.
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Antineoplastic Agents↗
Differences in basic fibroblast growth factor RNA and protein levels in human primary melanocytes and metastatic melanoma cells.
Cultivation of human melanocytes requires several growth factors for cell proliferation. For example, basic fibroblast growth factor (bFGF) is an essential growth agent for melanocyte proliferation in vitro and has been proposed to be an autocrine growth factor in human melanoma cells. Studies using either anti-bFGF antibodies or antisense oligonucleotides partially inhibited the proliferation of human melanoma cells. However, one group was unable to detect bFGF RNA transcripts in human melanoma cells using a human complementary DNA probe. These contradictory results prompted us to investigate the bFGF gene expression in human primary melanocytes and metastatic melanoma cells using Southern, Northern, and Western blot analyses. No gross rearrangements in the bFGF gene were detected in the genomic DNA. Although high levels of bFGF RNA transcripts were detected in melanocytes, no bFGF protein was detected using Western blot analysis. In contrast, melanoma cells expressed much lower levels of bFGF RNA transcripts, and cells from three of four cell strains synthesized the multiple isoforms of bFGF protein. In one of the melanoma cell strains, no bFGF protein was detected using Western blot analysis. Although three of four melanoma cell strains expressed bFGF protein, this molecule does not appear to function as an autocrine growth factor, and expression of the bFGF protein was not a consistent alteration in all melanoma cell strains.
Blotting, Northern↗
Isn't skin cancer preventable?
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Anticarcinogenic Agents↗