Antisense telomerase treatment: induction of two distinct pathways, apoptosis and differentiation

Abstract

Telomerase, the enzyme that elongates telomeric DNA (TTAGGG)n, may be involved in cellular immortality and oncogenesis. To investigate the effect of inhibition of telomerase on tumor cells, we transfected the antisense vector against the human telomerase RNA into human malignant glioma cells exhibiting telomerase activity. After 30 doublings, some subpopulations of transfectants expressed a high level of interleukin-1beta-converting enzyme (ICE) protein and underwent apoptosis. In contrast, other subpopulations also showed enhanced ICE protein but escaped from apoptotic crisis and continued to grow, although their DNA synthesis, invasive ability, and tumorigenicity in nude mice were significantly reduced. Surviving cells demonstrated increased expression of glial fibrillary acidic protein and decreased motility, consistent with a more differentiated state. These cells also contained enhanced expression of the cyclin-dependent kinase inhibitors (CDKIs) p21 and p27. Treatment of surviving nonapoptotic cells with antisense oligonucleotides against p27, but not p21, induced apoptotic cell death, suggesting that p27 may have protected differentiating glioma cells from apoptosis. These data show that treatment with antisense telomerase inhibits telomerase activity and subsequently induces either apoptosis or differentiation. Regulation of these two distinct pathways may be dependent on the expression of ICE or CDKIs.

Combination therapy of malignant glioma cells with 2-5A-antisense telomerase RNA and recombinant adenovirus p53

“…15,26 Therefore, it is expected that inhibition of telomerase Gene Therapy function may alter the growth properties of tumor cells and subsequently suppress the tumor growth. Since the RNA component of human telomerase (hTR) was first of all reported, 22 several strategies that target hTR with antisense RNA, [22][23][24] hammer head ribozyme 33 or peptide nucleic acids 34 were investigated. They reduced telomerase activity and tumor growth to some extent.…”

“…These facts strongly support the idea that telomerase inhibition may represent a novel targeting approach for the treatment of malignant gliomas. Recently, it has been demonstrated that targeting the RNA template of telomerase (hTR) with antisense RNA [22][23][24][25] or inhibiting the function of a catalytic protein subunit of telomerase (hTERT) with a dominant-negative mutant [26][27][28] showed a significant antitumor effect. We have recently synthesized a 19-mer antisense oligonucleotide against hTR linked 2-5A (5′-phosphorylated 2′-5′-linked oligoadenylate) (2-5A-anti-hTR) and demonstrated its cytotoxic effect on malignant glioma cells 29,30 or prostate cancer cells.…”

TGF-β and cancer: Is Smad3 a repressor of hTERT gene?

“…Expression of hTERT stimulates cell proliferation toward immortality [12][13][14][15][16] and contributes to tumor formation [17,18]. In contrast, inhibition of telomerase results in erosion of telomeres, compromise of growth capacity and apoptosis of highly proliferative cells [19][20][21][22][23][24]. Thus, hTERT is essentially a key element in telomerase activation, telomere maintenance and tumor development, and is proposed as a promising target for anticancer therapy.…”

Inhibition of telomerase activity in malignant glioma cells correlates with their sensitivity to temozolomide

“…Gaithernburg, MD, USA) according to the manufacturer's instruction with some minor modifications (Kondo et al, 1998a). Cells (10 6 ) were washed once in PBS and homogenised in 200 ml of ice-cold lysis buffer (0.5% 3-[3-cholamidopropyldimethylammonio]-1-propane-sulphonate (CHAPS), 10 mM TrisHCl, pH 7.5, 1 mM ethylenebis (oxyethylene-nitrilo) tetraacetic acid (EGTA), 5 mM b-mercaptoethanol, 0.1 mM 4-(2-aminoethyl) benzenesulphonyl fluoride (AEBSF), 10% glycerol).…”