Abstract 5219: Circulating hTERT (human telomerase) mRNA: mechanism of action and potential use for early diagnosis of malignancy

Abstract

Abstract In contrast to current impressive achievements in the biological knowledge and therapy of cancer, the field of early diagnosis lags behind and presents an unmet need. We hereby present the human telomerase as a potential tool for early diagnosis of cancer. Telomerase activation is a prerequisite for the perpetuation of the malignant clone during cancer progression as it elongates telomeres in each cell division. hTERT mRNA is shed into the serum and remains stable in vesicular forms named “Exosomes”. Exosomes are secreted by most cells containing nucleic acids, proteins and lipids. We established a method for the detection and quantification of hTERT mRNA products in exosomes derived from growth media of cancer cell lines and human sera for the future use as a diagnostic tool for the early detection of cancer. In four cancer cell lines we detected exosomal hTERT RNA expression, which also correlated with its telomerase activity and intracellular hTERT mRNA expression, compared to a non-telomerase expressing cell line. We studied the crosstalk between T cell leukemia derived exosomes and primary human fibroblast cells and revealed that primary cells can uptake exosomes derived from a different type of cell. The secreted exosomes affected the recipient cells by increasing the hTERT mRNA 6 hours post exposure and increasing telomerase levels and expression 24 hours post exposure, while the levels of the hTERT core promoter transcription factors did not change. For the future goal of establishing a method of early diagnosis of malignancies we screened 63 patients with different malignancies and compared their exosomal hTERT mRNA expression in the sera to that of 20 healthy volunteers. The results have shown that the expression of hTERT is variable among malignancies and between different patients with the same cancer type. To exclude some variables, such as drugs, that can influence exosome secretion from cells, we examined the influence of three chronically administered drugs on our chosen experimental cell lines. The drugs tested were Aspirin, Simvastatin and Captopril. While Simvastatin significantly decreased hTERT mRNA in exosomes derived from one cell line, neither aspirin nor Captopril effected the secretion of exosomes, indicated by a similar hTERT expression in the relevant treated cells. Furthermore, no change in the intracellular hTERT expression and telomerase activity after drug exposure was evident. In the light of these results we concluded that exosomes derived from tumor cells can affect the surrounding microenvironment by exploiting the recipient cell mechanism and promoting the activation of telomerase in those recipient cells. Understanding of these mechanisms may have a strong impact on deciphering metastases formation. Hopefully, promoting hTERT mRNA as a novel marker for malignancies will enable us to develop a new diagnostic tool for future use in the early diagnosis of cancer. Citation Format: Orit Uziel, Anna Gutkin, Einat Beery, Jardena Nordenberg, Hadar Goldvaser, Yair Zloof, Steven Henick, Meir Lahav. Circulating hTERT (human telomerase) mRNA: mechanism of action and potential use for early diagnosis of malignancy. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 5219. doi:10.1158/1538-7445.AM2015-5219