ras and c-myc oncoproteins during tumor progression in the uterine cervix

Altered oncogenic activity is a feature associated with many malignant and premalignant conditions. Among the many oncogenes, ras and myc are commonly altered in many tumors. This study aims to evaluate the expression of ras and c-myc oncoproteins in a total of 204 cervical tissue samples, including premalignant and malignant lesions as well as apparently normal cervical tissue.

Mouse monoclonal antibodies against the three mammalian ras gene products (c-H-ras, c-K-ras, c-N-ras) and the c-myc protein were used to evaluate oncoprotein expression by immunocytochemistry.

None of the samples analyzed displayed immunoreactivity for H-ras and K-ras. Normal cervical epithelium showed minimal immunoreactivity for N-ras with about 33% of the samples expressing the protein. More conspicuous expression in normal tissue was displayed by c-myc, with about 90% of the samples expressing the protein (mean value of cells positive=34%). The immunoreactivity for N-ras increased with increasing histological abnormality from low-grade squamous intraepithelial lesions (SIL) to invasive carcinoma. Increased immunoreactivity for N-ras was evident in the basaloid cells of malignant lesions, with the maximum value of 66% found in poorly differentiated squamous cell carcinoma (PDSCC). The percentage of nuclei positive for c-myc also showed a gradual increase from low-grade SIL onwards, the highest positivity being found in PDSCC, where the mean value was 85%. Statistical analysis revealed a good correlation between the expression of N-ras (r=0.8922, P=0.001) and c-myc (r=0.8856, P=0.001) and various histological stages of tumor progression in the cervical epithelium.

These results therefore suggest that c-myc and N-ras oncoproteins are important during tumor progression in the uterine cervix.