Telomerase a prognostic marker an therapeutic target

Abstract

Malignant glioma is the most common and aggressive form of tumours and is usually refractory to therapy. Telomerase and its altered activity, distinguishing cancer cells, is an attractive molecular target in glioma therapeutics. The aim of this thesis was to silence telomerase at the genetic level with a view to highlight the changes caused in the cancer proteome and identify the potential downstream pathways controlled by telomerase in tumour progression and maintenance. A comprehensive proteomic study utilizing 2D-DIGE and MALDI-TOF were used to assess the effect of inhibiting two different regulatory mechanisms of telomerase in glioma. RNAi was used to target hTERT and Hsp90α.
Inhibition of telomerase activity resulted in down regulation of various cytoskeletal proteins with correlative evidence of the involvement of telomerase in regulating the expression of vimentin. Vimentin plays an important role in tumour metastasis and is used as an indicator of glioma metastasis. Inhibition of telomerase via sihTERT results in the down regulation of vimentin expression in glioma cell lines in a grade specific manner. While, 9 of 12 glioblastoma tissues (grade IV) showed vimentin to be highly expressed, its expression was absent in lower grades and normal tissues. This suggests that vimentin can be potentially used as a glioma progressive marker. This is the first study to report the potential involvement of telomerase in the regulation of vimentin expression. This study also identified that combination therapy, comprising siRNA targeted towards telomerase regulatory mechanisms and the natural product Epigallocatechin-3-gallate (ECGC), results in decreased cell viability producing comparable results to that of other chemotherapeutic drugs.