Telomerase reverse transcriptase promotes epithelial-mesenchymal transition and stem cell-like traits in cancer cells.

Telomerase activation through induction of telomerase reverse transcriptase (hTERT) contributes to malignant transformation by stabilizing telomeres. Clinical studies demonstrate that higher hTERT expression is associated with cancer progression and poor outcomes, but the underlying mechanism is unclear. Because epithelial-mesenchymal transition (EMT) and cancer stem cells (CSCs) are key factors in cancer metastasis and relapse, and hTERT has been shown to exhibit multiple biological activities independently of its telomere-lengthening function, we address a potential role of hTERT in EMT and CSCs using gastric cancer (GC) as a model. hTERT overexpression promotes, whereas its inhibition suppresses, EMT and stemness of GC cells, respectively. Transforming growth factor (TGF)-ß1 and ß-catenin-mediated EMT was abolished by small interfering RNA depletion of hTERT expression. hTERT interacts with ß-catenin, enhances its nuclear localization and transcriptional activity, and occupies the ß-catenin target vimentin promoter. All these hTERT effects were independent of its telomere-lengthening function or telomerase activity. hTERT and EMT marker expression correlates positively in GC samples. Mouse experiments demonstrate the in vivo stimulation of hTERT on cancer cell colonization. Collectively, hTERT stimulates EMT and induces stemness of cancer cells, thereby promoting cancer metastasis and recurrence. Thus, targeting hTERT may prevent cancer progression by inhibiting EMT and CSCs.

Molecular cytogenetic characterization of acute myeloid leukemia and myelodysplastic syndromes with multiple chromosome rearrangements.

BACKGROUND AND OBJECTIVES: Multiple chromosome rearrangements (MCRs) are found in 5-10% of newly diagnosed patients with acute myeloid leukemia (AML) and 15-30% of patients with myelodysplastic syndromes (MDS). However, the initial causes of MCRs and the molecular mechanisms involved are largely unresolved. Nor are the karyotypic patterns well studied, mainly because of the difficulties of obtaining complete karyotypes by G-banding. In this study, we applied spectral karyotyping (SKY) and comparative genomic hybridization (CGH) to investigate further the resulting chromosome imbalances and rearrangements in AML and MDS bone marrow cells with MCRs. DESIGN AND METHODS: Bone marrow cells from 12 AML and 10 MDS patients with MCRs were collected at diagnosis and analyzed by G-banding, SKY and CGH. The patients' characteristics were also collected to pinpoint potential similarities and/or differences between the patients. RESULTS: Our results show that some MCRs seen in AML are similar to MCRs seen in MDS. These MCRs often result in chromosome loss of 5q, 7q and 17p and gain of chromosome 8. INTERPRETATION AND CONCLUSIONS: The characteristics associated with MRCs include old age, previous exposure to radio- and/or chemotherapy and a short survival time. Probably, these patients should be distinguished from AML patients with primary chromosome rearrangements among other unbalanced chromosome rearrangements. In our experience, SKY and CGH facilitated this process.

Frequent amplification of the telomerase reverse transcriptase gene in human tumors.

Activation of telomerase is a crucial step during cellular immortalization and malignant transformation of human cells and requires the induction of the catalytic component, human telomerase reverse transcriptase (hTERT), encoded by the hTERT gene. It is poorly understood how the hTERT gene is activated in human cancer cells. In the present study, we examined the hTERT gene copy number in human cancer cell lines and in primary tumor tissues. Amplification of the hTERT gene was observed in 8 of 26 (31%) tumor cell lines and 17 of 58 (30%) primary tumors examined (8 of 21 lung tumors, 3 of 10 cervical tumors, 5 of 19 breast carcinomas, and 1 of 8 neuroblastomas). In addition, 13 of 26 (50%) cell lines and 13 of 58 (22%) primary tumors displayed gain of hTERT gene copies with 3-4 copies/cell. The present findings imply that the hTERT locus may be a frequent target for amplification during tumorigenesis and that this genetic event probably contributes to the dysregulation of telomerase activity occurring in human tumors.

RT-PCR analysis of the MOZ-CBP and CBP-MOZ chimeric transcripts in acute myeloid leukemias with t(8;16)(p11;p13).

The translocation t(8;16)(p11;p13) is associated with a subtype of acute monocytic leukemia (AML M5) characterized morphologically by erythrophagocytosis and clinically by a poor prognosis. The t(8;16) fuses the MOZ gene from 8p11 with the CBP (also named CREBBP) gene from 16p13. Previously published studies of MOZ and CBP rearrangements in t(8;16)-positive AML have used fluorescence in situ hybridization and Southern blot methodologies, whereas attempts to amplify and to analyze further the chimeric MOZ-CBP and CBP-MOZ transcripts by means of reverse transcriptase-polymerase chain reaction (RT-PCR) have largely been unsuccessful. In the only t(8;16) that has been described at the sequence level using RT-PCR, the CBP-MOZ fusion was found to be out-of-frame, suggesting that the reciprocal MOZ-CBP transcript is the essential one for leukemogenesis. We have developed an RT-PCR strategy that enables us to detect the MOZ-CBP as well as the CBP-MOZ fusions in the two AML M5 with t(8;16)(p11;p13) analyzed. In both leukemias, the combination of a MOZ forward and a CBP reverse primer amplified a strongly expressed 1,128 bp fragment (type I transcript) and a weakly expressed 415 bp fragment (type II transcript). In the type I transcript, nucleotide (nt) 3,745 of MOZ was fused in-frame with nt 284 of CBP, whereas in the type II transcript, nt 3,745 of MOZ was fused out-of-frame with nt 997 of CBP. Nested PCR with a combination of two forward CBP and two reverse MOZ primers amplified CBP-MOZ chimeric transcripts in both cases. Direct sequence analysis showed that nt 283 of CBP was fused in-frame with nt 3,746 of MOZ, that the initiation ATG codon of the CBP gene remained intact, and that there was no mutation or deletion in the part of the CBP gene included in the CBP-MOZ transcript. Thus, the data we present are not informative with regard to the question whether it is the MOZ-CBP or the CBP-MOZ transcript that is leukemogenic. The present RT-PCR method may be of value for rapid identification of the t(8;16) and also for further molecular genetic studies of the two fusion transcripts and their roles in leukemogenesis.