| We initiated the present study to evaluate the accuracy of new epithelial biomarkers and role of these markers in understanding lung carcinogenesis. The hypothesis of this research was that expression of tumor-associated antigens by sputum epithelial cells has greater accuracy (sensitivity and specificity) for detection of early (localized) lung cancer than routine screening methods. We compared the monoclonal antibody (Mab 703D4) detection of heterogenous nuclear Ribonuclear protein (hnRNP) with current cytology and radiographic screening under field condition to assess the accuracy and the timing of marker expression among miners highly exposed to tobacco smoke, radon and arsenic in Southwestern China.; A dynamic cohort was selected from an ongoing lung cancer screening program among radon/arsenic exposed tin miners in Yunnan China. The cohort consists of 7,873 miners at least 40 years old with at least ten years underground mining. Annual sputum specimens and chest radiographs have been collected and stored. In addition, a one time collection of blood, urine, and toenails are available on more than 50% of the participants. During its first three years, this cohort compiled 17,100 person-years of observation and identified and confirmed 178 cases of lung cancer. Although occupational exposures are the predominant risk factors, initial cohort analyses showed that lung cancer also was associated with chronic obstructive lung disease and a number of measures of exposure to tobacco smoke, including early age of first use, duration, and cumulative exposure.; In the past, viscoelastic properties of mucoid glycoprotein mixed with airway cells in the sputum have inhibited quantitative studies and cell sorting for further biomarker characterization. A preparation technique has been developed to enrich exfoliated cells for biomarker expression. We compared the safety and efficacy of homogenizing sputum with deoxyribonuclease I (DNAse I), dithiothreitol (DTT), N-Acetyl-L-Cysteine, Sodium EDTA, and Trypsin against standard mechanical blending to provide mucus-free single cell suspensions. Cell counts and Papanicolaou staining showed that homogenization of induced, preserved sputum with 0.5 mM DTT is safe and provides mucus-free monolayer for immunocytochemistry and single cell suspensions for flow cytometry. Mucolysis with 0.5 mM DTT resulted in a significant 16% increase in cells available. In contrast, blending resulted in up to a 24% reduction in specimen cellularity.; Finally, we determined that Mab detection of the hnRNP tumor-associated antigens expressed by sputum epithelial cells had greater accuracy (sensitivity and specificity) for detection of early (localized) lung cancer than routine screening methods. Among 57 cases and 76 non-cases at the first screening, the sensitivity of Mab detection of hnRNP exceeded standard methods (74% vs. 21-42%) but had limited specificity (70 vs. 90-100%). Detection of hnRNP expression may be an excellent initial screening test for lung carcinogenesis, distinguishing those with high probability of developing subsequent clinical cancer. Future studies might follow Mab detection with markers of increasing specificity (e.g., those which are expressed later in the morphologic progression or gene markers). Detection of carcinogenesis might be particularly important if future studies show that for lesions at this early stage, a non-invasive chemoprevention therapy effectively reverses the field carcinogenesis. Mab markers might also be useful as intermediate endpoints in such studies. |
