Comparison of gene expression in squamous cell carcinoma and adenocarcinoma of the uterine cervix

Microarray expression analysis of cervical tumors has revealed differential expression of genes that may be useful as markers or targets for treatment. We question the application of array findings across the major categories of cervical cancer. We sought to identify differences between normal squamous epithelium (NSQ) and glandular epithelium (NGL) of the uterine cervix and their malignant variants: squamous cell cancer (SCC) and adenocarcinoma (ACA). Eight genes were selected: 12-lipoxygenase (12-LOX), keratin 4, trypsinogen 2 (TRY2), Rh glycoprotein C (RhGC), collagen type V alpha 2, integrin alpha 5, integrin alpha 6, and c-myc. Ten cases each of SCC and ACA of the cervix were selected from our tumor bank. NSQ and NGL epithelia were obtained from consecutive patients undergoing surgery for benign disease. RNA extraction, cDNA synthesis, and DNA amplification of all samples were performed according to an established protocol. Electrophoresis of the multiplexed polymerase chain reaction (PCR) products was performed under standard conditions, followed by digital image capture. A ratio of target to control gene (β-actin) was obtained for each sample. Analysis of variance was applied to the mean ratios for each tissue to establish significant differences. Individual pairwise comparisons were made by Student t tests and verified with the Tukey-Kramer test. Clinically valid comparisons are NSQ to NGL, NSQ to SCC, NGL to ACA, and SCC to ACA. Various expression patterns were observed between the epithelia and their malignant phenotypes. Significant differences in gene expression were observed between benign squamous and glandular epithelium in four of the eight genes and between malignant squamous and glandular epithelium in three of the eight genes. Significant differences in gene expression between benign and malignant tissues were demonstrated in four of the eight genes. We have defined significant differential expression changes between the two principal cervical tumor types. Differences in genes are demonstrated and must be considered if array technology is applied to the study of the biologic behavior of these tumors as well as their screening and management. The observed differential expression should be a compelling argument to perform type-specific expression analysis for other tumors with histological variants.