CGB and GNRH1 expression analysis as a method of tumor cells metastatic spread detection in patients with gynecological malignances

BACKGROUND: Metastasis is a common feature of many advanced stage cancers and metastatic spread is thought to be responsible for cancer progression. Most cancer cells are localized in the primary tumor and only a small population of circulating tumor cells (CTC) has metastatic potential. CTC amount reflects the aggressiveness of tumors, therefore their detection can be used to determine the prognosis and treatment of cancer patients. The aim of this study was to evaluate human chorionic gonadotropin beta subunit (CGB) and gonadoliberin type 1 (GNRH1) expression as markers of tumor cells circulating in peripheral blood of gynecological cancer patients, indicating the metastatic spread of tumor. METHODS: CGB and GNRH1 expression level in tumor tissue and blood of cancer patients was assessed by real-time RT-PCR. The data was analyzed using the Mann-Whitney U and Spearman tests. In order to distinguish populations with homogeneous genes' expression the maximal likelihood method for one- and multiplied normal distribution was used. RESULT: Real time RT-PCR results revealed CGB and GNRH1 genes activity in both tumor tissue and blood of gynecological cancers patients. While the expression of both genes characterized all examined tumor tissues, in case of blood analysis, the transcripts of GNRH1 were found in all cancer patients while CGB were present in 93% of patients. CGB and GNRH1 activity was detected also in control group, which consisted of tissue lacking cancerous changes and blood of healthy volunteers. The log-transformation of raw data fitted to multiplied normal distribution model showed that CGB and GNRH1 expression is heterogeneous and more than one population can be distinguished within defined groups. Based on CGB gene activity a critical value indicating the presence of cancer cells in studied blood was distinguished. In case of GNRH1 this value was not established since the results of the gene expression in blood of cancer patients and healthy volunteers were overlapping. However one subpopulation consists of cancer patient with much higher GNRH1 expression than in control group was found. CONCLUSIONS: Assessment of CGB and GNRH1 expression level in cancer patients' blood may be useful for indicating metastatic spread of tumor cells.