Telomerase inhibition with an oligonucleotide telomerase template antagonist: in vitro and in vivo studies in multiple myeloma and lymphoma

Abstract

The effects of telomerase inhibition with an oligonucleotide N3 3 P5 thiophosphoramidate (GRN163) complementary to the telomerase template region were examined on human multiple myeloma (MM) and non-Hodgkin lymphoma (NHL) cell lines, primary MM cells, and tumor xenografts. GRN163 treatment reduced telomerase levels in all cells and induced more rapid telomeric shortening. Continuous GRN163 treatment for 7 to 14 days resulted in proliferative arrest, morphologic changes, and apoptosis characteristic of cell crisis in tumor cell lines with short (1.7-5.4 kb) but not long (9-11 kb) telomeres. Intratumoral administration of GRN163 also inhibited the growth of MM and NHL xenografts established from cell lines with short telomeres (Hs602 lymphoma, 2.7 kb; CAG myeloma, 2.7 kb) and increased tumor apoptosis. However, GRN163 therapy of NHL xenografts established from cells with long telomeres (11.0 kb) had equivocal effects on tumor growth and did not induce apoptosis during this time frame. Systemic daily intraperitoneal administration of GRN163 in myeloma xenografts with short telomere lengths also decreased tumor telomerase levels and reduced tumor volumes. These data demonstrate that telomerase is important for the replication of mature B-cell neoplasia by stabilizing short telomeres, and they suggest that telomerase inhibition represents a novel therapeutic approach to MM and NHL. IntroductionThe preservation of telomeres, DNA-protein structures located at the ends of eukaryotic chromosomes, is essential to the immortalization process. In most normal somatic cells, telomeric DNA is progressively lost with each cell division until a critically short telomere length is obtained, and telomeres lose the ability to protect linear chromosomal ends. The resultant telomeric dysfunction induces cell "crisis" with chromosomal instability, end-to-end chromosome fusions, activation of DNA checkpoint responses, apoptosis, and cell death. 1 Human telomerase is a complex ribonucleoprotein reverse transcriptase composed of an RNA template (hTR) and a catalytic protein subunit (hTERT), which is responsible for synthesizing d-(TTAGGG) n telomeric repeats at chromosomal ends. Stabilizing telomeric DNA through telomerase up-regulation or activating alternative mechanisms of telomere maintenance is essential if cells are to survive and proliferate indefinitely. 2 Telomerase activity (TA) is not found in most normal somatic cells, which lack hTERT, but it has been detected in high levels in 85% to 90% of human cancers. 1 Although telomerase is not an oncogene, 3 transfecting hTERT into normal epithelial or endothelial cells transformed with the simian virus 40 large T-antigen and the N-ras oncogene allows cells to bypass crisis and ultimately to achieve malignancy, confirming the role of telomerase in cellular immortalization and tumorigenesis. 1 Telomerase inhibition by numerous strategies, including dominant-negative telomerase mutants, 4,5 small-molecular-weight compounds, 6 reversetranscriptase inhibitors, 7 G-quadruplex interactive...

The HSP90 inhibitor alvespimycin enhances the potency of telomerase inhibition by imetelstat in human osteosarcoma

“…11 Studies in various adult and pediatric cancer cell lines have demonstrated that imetelstat, but not a mismatch oligonucleotide control, inhibited cell proliferation, colony formation, and invasiveness. [11][12][13][14][15][16][17][18] Phase 1 and 2 clinical trials demonstrated a favorable pharmacokinetic and side effect profile for imetelstat, though with mixed clinical results. 14,[19][20][21][22][23] Although telomerase activity is regulated largely at the level of transcription of TERT, the gene that encodes the catalytic component of the telomerase enzyme complex, it has become clear that telomerase regulation is complex and also involves posttranslational modifications, alternative splicing, and binding to chaperone proteins.…”

Telomerase antagonists GRN163 and GRN163L inhibit tumor growth and increase chemosensitivity of human hepatoma

“…18 Preclinical studies revealed that a development candidate from this class of oligonucleotides, GRN163, inhibited telomerase activity in various cultured human cancer cell lines (breast, renal, prostate, epidermoid, cervix, lung, colon, leukemia, multiple myeloma, lymphoma) leading to telomere shortening, growth arrest, and apoptosis. [23][24][25][26][27] In addition, GRN163 inhibited tumor growth of prostate cancer, multiple myeloma, lymphoma, and glioblastoma in xenotransplant models. 24,26,27 To evaluate the potential use of NPSS oligonucleotides targeting the human telomerase RNA component for the treatment of HCC, we analyzed GRN163 and GRN163L, a lipid-conjugated derivative of GRN163 designed for increased bioavailability, 28 for antitumor effects against human hepatoma cells (Hep3B and Huh7) in vivo and in vitro.…”

“…[23][24][25][26][27] In addition, GRN163 inhibited tumor growth of prostate cancer, multiple myeloma, lymphoma, and glioblastoma in xenotransplant models. 24,26,27 To evaluate the potential use of NPSS oligonucleotides targeting the human telomerase RNA component for the treatment of HCC, we analyzed GRN163 and GRN163L, a lipid-conjugated derivative of GRN163 designed for increased bioavailability, 28 for antitumor effects against human hepatoma cells (Hep3B and Huh7) in vivo and in vitro. The results suggest that telomerase inhibition could be a valid approach for HCC treatment and that GRN163L is a promising drug development candidate with significant effects on tumor growth and increased chemosensitivity to doxorubicin.…”

New Therapeutic Strategies for the Treatment of Brain Tumor

“…GRN-163 has demonstrated potent inhibitory activity against human telomerase in several biochemical assays, with IC 50 values of < 1 nM (Gryaznov et al, 2001;Herbert et al, 2002). In vitro, telomerase inhibition by GRN-163 induced cellular senescence and apoptosis in various human cancer cell lines (Ozawa et al, 2004;Asai et al, 2003;Herbert, 2002;Akiyama et al, 2003;Wang et al, 2004). Although a potential limitation of oligonucleotide therapies is the bioavailability in tumor tissues (Corey, 2002), GRN-163 inhibited tumor growth in prostate cancer, multiple myeloma, lymphoma, hepatoma and glioblastoma xenografts in rodents (Ozawa et al, 2004;Asai et al, 2003;Wang et al, 2004;Hashizume et al, 2008;Djojosubroto et al, 2005).…”

“…In vitro, telomerase inhibition by GRN-163 induced cellular senescence and apoptosis in various human cancer cell lines (Ozawa et al, 2004;Asai et al, 2003;Herbert, 2002;Akiyama et al, 2003;Wang et al, 2004). Although a potential limitation of oligonucleotide therapies is the bioavailability in tumor tissues (Corey, 2002), GRN-163 inhibited tumor growth in prostate cancer, multiple myeloma, lymphoma, hepatoma and glioblastoma xenografts in rodents (Ozawa et al, 2004;Asai et al, 2003;Wang et al, 2004;Hashizume et al, 2008;Djojosubroto et al, 2005). GRN-163 has been delivered successfully into the brain using IND and shown impressive oncolytic activity without harming normal brain tissue (Hashizume et al, 2008).…”