Intermediate biomarkers in upper aerodigestive tract and lung chemoprevention trials

Oral field cancerization: current evidence and future perspectives

INTRODUCTION

Oral field cancerization implies that oral cancer does not arise as an isolated cellular phenomenon but rather as an anaplastic tendency involving many cells at once and results in the multifocal development of cancer at various rates within the entire field in response to a carcinogen especially tobacco. This concept has been frequently used to explain the occurrence of multiple primary cancers and recurrences following complete excision of oral cancer.

DISCUSSION

This review deals in detail with the origin, principle, various theories used to explain this effect and molecular, genetic, as well as cytogenetic findings related to oral field cancerization. Further, the clinical implications and future research directives are also discussed.

Aberrant crypt foci in colon cancer epidemiology

Colonic carcinogenesis is characterized by progressive accumulations of genetic and epigenetic derangements. These molecular events are accompanied by histological changes that progress from mild cryptal architectural abnormalities in small adenomas to eventual invasive cancers. The transition steps from normal colonic epithelium to small adenomas are little understood. In experimental models of colonic carcinogenesis aberrant crypt foci (ACF), collections of abnormal appearing colonic crypts, are the earliest detectable abnormality and precede adenomas. Whether in fact ACF are precursors of colon cancer, however, remains controversial. Recent advances in magnification chromoendoscopy now allow these lesions to be identified in vivo and their natural history ascertained. While increasing lines of evidence suggest that dysplastic ACF harbor a malignant potential, there are few prospective studies to confirm causal relationships and supporting epidemiological studies are scarce. It would be very useful, for example, to clarify the relationship of ACF incidence to established risks for colon cancer, including age, smoking, sedentary lifestyle, and Western diets. In experimental animal models, carcinogens dose-dependently increase ACF, whereas most chemopreventive agents reduce ACF incidence or growth. In humans, however, few agents have been validated to be chemopreventive of colon cancer. It remains unproven, therefore, whether human ACF could be used as reliable surrogate markers of efficacy of chemopreventive agents. If these lesions could be used as reliable biomarkers of colon cancer risk and their reductions as predictors of effective chemopreventive agents, metrics to quantify ACF could greatly facilitate the study of colonic carcinogenesis and chemoprevention.

Assessing intraepithelial neoplasia and drug safety in cancer-preventive drug development

Despite significant interest from the research community and the population in general, drug approvals for cancer prevention and/or cancer risk reduction are few. This is due, in part, to the requirement that new cancer-preventive drugs must first be shown to be efficacious in reducing cancer incidence or mortality. Moreover, such drugs need to have proven safety for long-term administration. This process can be improved by focusing on precancer (intraepithelial neoplasia) to identify subjects at risk and prove efficacy in shorter, smaller trials as well as on detecting early markers of potential toxicities of chronic exposure to cancer-preventive drug regimens.

Positive impact of retinyl palmitate in leukoplakia of the larynx

Laryngeal leukoplakia can be a premalignant precursor of squamous cell carcinoma, is often tobacco-related and can usually be readily monitored by indirect laryngoscopy. One of the main motivations for using retinyl palmitate in patients with persistent leukoplakia was to avoid general anesthesia for elderly patients, who are considered to be high-risk patients when direct larynoscopy is required for possible tissue biopsy. Our study was the first to investigate the effectiveness and toxicity of high-dose retinyl palmitate in the treatment of laryngeal leukoplakia. Treatment was divided into two phases. In the first phase, all patients underwent induction therapy with 300,000 IU/day of retinyl palmitate for the 1st week, which was then adjusted up to 1,500,000 IU/day in the 5th week in patients with resistant lesions. Patients whose lesions progressed during this period were withdrawn from the study. In the second phase, patients whose lesions responded to treatment or remained stable were assigned to a maintenance therapy of 150,000 IU/day. Complete remission was observed in 15 of 20 patients (75% of cases). Partial response was seen in the remaining 5 patients, with 3 of the patients relapsing. The median duration of treatment and follow-up was 18 months (range, 12-24 months). These results indicate that retinyl palmitate has substantial activity in laryngeal leukoplakias. Since only minor side effects were seen, the medication is an excellent candidate as a preventive agent for laryngeal cancer.

Long-term follow-up of larynx leukoplakia under treatment with retinyl palmitate

BACKGROUND

Larynx leukoplakia can be a premalignant precursor of squamous cell carcinoma, is often tobacco related, and can be monitored easily by indirect laryngoscopy. One of the main motivations for using retinyl palmitate in patients with larynx leukoplakia was to avoid general anesthesia for the elderly patients, who are considered to be at high risk for undergoing direct laryngoscopy. Our study investigates for the first time the effectiveness and toxicity of high-dose retinyl palmitate in the treatment of larynx leukoplakia.

METHODS

Treatment was divided into two phases. In the first phase, all patients underwent induction therapy with a high-dose of retinyl palmitate (A-Mulsin Hochkonzentrat, Mucos Pharma, Geretsried, Germany) with 300,000 IU/day for the first week and up to 1,500,000 IU/day, in patients with resistant lesions, in the fifth week. Patients whose lesions progressed during this period were withdrawn from the study. In the second phase, patients whose lesions responded to treatment or remained stable were then assigned to a maintenance therapy of 150,000 IU/day.

RESULTS

We observed a complete remission rate of 75% (15 of 20 patients). Among the 5 patients with partial response, 3 relapsed. The median duration of treatment and follow up was 18 months (range 12-24 months).

CONCLUSIONS

These results indicate that retinyl palmitate has substantial activity in larynx leukoplakias. Furthermore, only minor side effects make it an excellent candidate as a preventive agent for larynx cancer.

Proliferating cell nuclear antigen may be superior to argyrophilic nucleolar organizer regions in predicting shortened survival of patients with non-small cell lung cancer

We examined proliferating cell nuclear antigen (PCNA) in 102 patients with surgically treated non-small cell lung cancer (NSCLC). PCNA labelling index (LI) tended to be higher in tumours of higher stages than those of early stages, in squamous cell carcinomas than adenocarcinomas, or in poorly differentiated adenocarcinoma than in well-differentiated. A positive correlation was observed between the PCNA LI and argyrophilic nucleolar organizer regions (Ag-NOR) count which we previously examined (r = 0.31, P = 0.002). In survival analysis of 79 patients who died of lung cancer, only age, stage and PCNA LI were found to be significant prognostic factors on multivariate analysis among seven potential prognostic factors including sex, age, year of operation, histological type, stage, Ag-NOR count, and PCNA LI. We conclude that PCNA may be superior to Ag-NOR in predicting shortened survival of patients with non-small cell lung cancer. PCNA staining can be performed with ease and it may be applied in a clinical laboratory on a routine basis to help predict prognosis of NSCLC.

Molecular epidemiology of lung cancer and the modulation of markers of chronic carcinogen exposure by chemopreventive agents

Chronic inhalation exposure to environmental carcinogens such as polycyclic aromatic hydrocarbons (PAHs), cigarette smoke, 4-aminobiphenyl (4-ABP), ethylene oxide, and styrene is associated with elevations in biomarkers such as DNA adducts, protein adducts, sister chromatid exchanges (SCEs), chromosomal aberrations, gene mutation, and/or oncogene activation. These biomarkers indicate an increased cancer risk for the exposed population, although quantitative estimates cannot be made with certainty. There is convincing epidemiological evidence that the antioxidant and free radical-scavenging vitamins C and E and beta-carotene (beta-C) protect against cancer of the lung and other epithelial tissues, with somewhat weaker evidence for retinol. Experimental studies demonstrate that these micronutrients are capable of blocking or reducing tumor formation caused by diverse carcinogens. A variety of mechanisms appear to be involved, including suppression of carcinogen activation, enhancement of carcinogen detoxification, induction of cellular differentiation, inhibition of mutagenesis, enhancement of immunologic function, and/or reduction of the formation of carcinogen-DNA adducts, SCEs, micronuclei, and other markers of genotoxic damage. Therefore, we have recently investigated the possible modifying effect of serum vitamins C and E, beta-C, and retinol on a number of such biomarkers in a case-control study of lung cancer, and in a cross-sectional study of heavy smokers. Preliminary results indicate an inhibitory effect of certain vitamins on DNA adduct formation. A significant number of human intervention trials are ongoing involving these vitamins. It appears that biomarkers can provide useful intermediate endpoints for assessment of both the mechanisms and the efficacy of chemopreventive agents.