GRP and in situ carcinoma: This study investigated possible candidate biomarkers for NSCLC by measuring the AIC and its free antigen for four proteins (CYFRA21-1, ProGRP, neutrophil gelatinase-associated lipocalin [NGAL], and NSE), using a 9-guanine DNA chip to detect stage 0 (carcinoma in situ [CIS])–IV NSCLC.