TSP-1 mRNA Expression in Invasive Cervical Cancer: Correlate with Angiogenesis and Clinicopathological Features

Kim, Yea Hong; Lee, Seon Kyung; Chi, Sung Gil; Lee, Ju Hee; Kim, Seung Bo

Abstract

OBJECTIVE
Acquisition of a proangiogenic environment is essential to the cervical cancer growth, invasion and metastasis, and the angiogenic phenotype in cervical cancer is strongly associated with clinical outcome. However, the regulation of the metastatic process in cervical cancer has not been well defined. Thrombospondin-1 (TSP-1) is a representative angiogenesis suppressor whose loss or reduced expression has been frequently observed in many types of human neoplasms. In this study, we examined whether expression of TSP-1 is associated with clinicopathological features, including microvessel density and evaluated its prognostic significance in patients with cervical cancer.
METHODS
The expression and mutation status of TSP-1 was examined by quantitative RT- and genomic PCR and RT-PCR-SSCP analysis and microvessel density was performed using immunohistochemical staining in 7 normal cervix and 37 cervical cancers.
RESULTS
All normal cervix tissues express easily detetable levels of TSP-1 transcript in range of 1.41-1.62 (mean 1.51 +/- 0.07). In contrast to normal tissue, mRNA expression of TSP-1 in primary cancer was detected in range of 0.51-1.69 (mean 1.03 +/- 0.36), and 35.1% (13 of 37) of carcinomas expressed abnormally low levels of TSP-1 (p<0.05). Moreover, abnormal reduction of TSP-1 expression was more frequently observed in IIa-IIb cancer (60%, 6 of 10) compared to Ib cancer (25.9%, 7 of 27) (p<0.05). None of carcinoma tissues we tested showed abnormal reduction of TSP-1 gene level and no evidences for sequence alterations leading to amino acid substitution were identified, indicating that allelic deletion or mutational alteration of TSP-1 might be a rare event in cervical carcinogenesis. Microvessel density was significantly higher in tumors showing decreased expression of TSP-1 (abnormal low group: 11.3 +/- 5.06, others: 6.64 +/- 7.15) (p<0.05). To detect the possible deletion of the gene and the presence of sequence alteration in TSP-1 transcripts, we performed quantitative genomic PCR and RT-PCR-SSCP analysis. However, none of carcinoma tissues we tested showed abnormal reduction of TSP-1 gene level and no evidence for sequence alterations leading to amino acid substitution were identified.
CONCLUSION
Our study demonstrates that abnormal reduction of TSP-1 mRNA expression is frequent in cervical cancer and correlates with the malignant progression of cervical cancers. Our data also show that allelic deletion or mutational alteration of TSP-1 is rare in cervical cancers, suggesting that abnormal reduction of TSP-1 mRNA expression in cervical cancers might be caused by altered transcriptional down regulation of the gene, such as epigenetic gene silencing. The inverse correlation between TSP expression and microvessel density also indicates that decreased TSP-1 expression might be associated with an angiogenic phenotype in cervical cancer.