Intermediate endpoint biomarkers for chemoprevention

Abstract

The understanding of intermediate endpoint biomarker expression in relation to the sequential events in bladder tumorigenesis establishes a useful approach for evaluating chemopreventive agents. Biomarkers may be genotypic or phenotypic and function as biomarkers of susceptibility, exposure, effect, or disease. This paper reviews several years of research on biomarkers and their use in monitoring chemoprevention therapy. In initial animal experiments, mice were dosed with Kbutyl-N(4-hydroxybutyl)nitrosamine (OH-BBN) while co-administering K(4-hydroxypheny1)retinamide (4-HPR).4-HPR did not statistically reduce tumor incidence, but did affect tumor differentiation and, consequently, nuclear size and DNA ploidy. These results suggest that nuclear size and ploidy may function as intermediate endpoint biomarkers of effect for oncogenesis and that epigenetic as well as genetic mechanisms may be primary in the oncogenic process. Early biomarkers of effect which occur prior to genetic effects or chromosome aberration may portend a higher probability of being modulated by differentiating agents such as retinoids. In v i m studies demonstrated that RPMI-7666 cells cultured with a phorbol estertumor promoter (1 2-Otetradecanoyl-phorbol-13-acetate) could be redifferentiated with 13-cis-retinoic acid and dimethyl sulfoxide (DMSO). F-actin, a cytoskeletal biomarker with a presumed function in the epigenetic mechanisms of carcinogenesis, could also be normalized in HL-60 cells treated with 4-HPR or DMSO.A clinical evaluation of F-actin in patients with varying degrees of risk confirmed the value of F-actin as a differentiating biomarker useful for bladder cancer risk assessment. The clarification of when the phenotypic changes of F-actin occur in the oncogenic process was achieved when a variety of biochemical changes were mapped in the patients with bladder cancer. These studies confirmed that G-actin, a reciprocal form of F-actin, is increased relatively early in bladder cancer oncogenesis when multiple biomarkers are quantitated in the field, adjacent area, and the tumor. Comparison of each individual biomarker's expression from field, adjacent to tumor, and tumor, and subsequent cluster analysis of these biomarkers, indicated that the possible sequence of phenotypic expression of biomarkers in bladder cancer oncogenesis is from G-actin, to p300 antigen, to epidermal growth factor receptor (EGFR), to p185 (neu oncogene product), to DNA aneuploidy and, finally, to visual morphology. To date, a battery of three biomarkers, G-actin, M344, and DNA, with routine cytology has been used to monitor eleven patients receiving Bacillus Calmette-Guerin (BCG) immunotherapy and eight patients clinically free of bladder cancer (negative cytology and biopsy) who were treated with the differentiation agent, DMSO. These results indicate that G-actin may be a useful biomarker for evaluating the efficacy of chemopreventive agents.

Alterations in phenotypic biochemical markers in bladder epithelium during tumorigenesis.

“…Four nonexclusive mechanisms may produce field disease: (i) hypersusceptibility of all the cells in a bladder resulting from inherited heterozygosity for a defective suppressor function (35,36), (ii) widespread genotypic changes from carcinogenic exposure affecting a significant portion or all of the bladder epithelium that increases the pool of cells immediately susceptible to ultimate carcinogenic conversion (37), (iii) altered growth and differentiation resulting from alterations in the complex tissue ecology induced by cytokines secreted by tumor cells (38), and (iv) "seeding" of either tumor or dysplastic cells from a single precursor lesion (25) (24). We suggest that by using quantitative phenotypic marker profiles the way is now open to investigate the cancer risk faced by an individual.…”

“…A corresponding negative control slide omitting primary antibodies was also prepared. All reagent concentrations were optimized to achieve saturation of cellular binding sites (22,24). Each batch of reagent was individually titrated to determine the appropriate concentration that produced saturation and, hence, proportionality between immunofluorescence and the target biomolecule.…”

Urinary Cytodiagnosis: Can It Have a Different Prognostic Implication than a Diagnostic Test?

“…TCC is associated with a urothelial field change [25][26][27]. Random bladder biopsy or histologic mapping of cys tectomy specimens reveals a high incidence of atypia and carcinoma in situ in grossly normal urothelium.…”

Biomarker analysis on breast ductal lavage cells in women with and without breast cancer

“…13 DNA5cER, the percentage of cells with a DNA content of more than 5c, is a marker of overall genetic instability. 15 Previous studies from our laboratory showed the feasibility of measuring these 2 markers simultaneously on archived fine-needle aspiration slides by quantitative fluorescence image analysis (QFIA), and over-expression of both markers might be potential risk indicators for developing breast cancer. 16 The QFIA approach allows the analysis of multiple cellular markers simultaneously on single-cell basis after the completion of conventional morphological evaluation on the same slide; therefore, the conventional morphological evaluation would not be compromised.…”