Advances in Clinical and Experimental Medicine
2019, vol. 28, nr 4, April, p. 507–513
Publication type: original article
Correlations between the expression of hTERT and α and β splice variants in human brain tumors
1 Pediatric Inherited Diseases Research Center, Research Institute for Primordial Prevention of Non-Communicable Disease and Department of Genetics and Molecular Biology, School of Medicine, Isfahan University of Medical Sciences, Iran
2 Neurology Department, Faculty of Medicine, Isfahan University of Medical Sciences, Iran
Background. Astrocytomas are diffusible infiltrative and aggressive brain tumors that are extensive and heterogeneous clusters of neoplastic growths in the central nervous system (CNS). Meningioma tumors are commonly benign but may demonstrate an invasive pattern with frequent recurrences. Human telomerase reverse transcriptase (hTERT) is an unfavorable prognostic factor for several types of cancers, and there are controversies about its role.
Objectives. In the present study, we investigated the relative expression of hTERT splice variants in 2 groups of brain tumors compared to non-tumor samples.
Material and Methods. The mRNA of 40 brain tumor samples and 4 control samples was extracted; mRNA expression of hTERT α-deletion and β-deletion variants, as well as the wild type isoform, was quantified using quantitative reverse transcription polymerase chain reaction (RT-qPCR).
Results. The α-deletion variant was significantly expressed in primary benign meningeal tumors (p = 0.01). The results indicate a positive correlation between the relative expression of hTERT mRNA transcript and α-deletion and β-deletion variants in both groups of tumors (meningiomas and astrocytomas). A strong association between the expression of the full-length splice variant and the β-deletion variant was observed in astrocytoma tumors (p = 0.045). The most significant correlations were found between the hTERT full-length and β-deletion variants in high-grade meningiomas (p = 0.018, correlation coefficient (CC) = 0.964) and grade II astrocytomas (p = 0.015; CC = 0.580). In addition, in low grades of both types of tumors, the hTERT full-length variant and especially the α-deletion variant were the predominant isoforms. The overexpression of hTERT and β-deletion variants in high grades of these tumors was statistically significant. Our findings indicate that α-deletion and β-deletion isoforms are associated with high levels of full-length hTERT mRNA in both groups of brain tumor patients.
Conclusion. Changes in the splicing pattern of hTERT splice variants in brain tumors and their correlation with pathological alterations in cells could be applied as diagnostic or prognostic biomarkers, or possibly as targets for cancer therapy. However, the function and biological role of hTERT splice variants remain to be clarified.
meningioma, astrocytoma, human telomerase reverse transcriptase, α-deletion splice variant, β-deletion splice variant
- Giese A, Loo MA, Tran N, Haskett D, Coons SW, Berens ME. Dichotomy of astrocytoma migration and proliferation. Int J Cancer. 1996;67(2): 275–282.
- Wick W, Platten M, Meisner C, et al. Temozolomide chemotherapy alone versus radiotherapy alone for malignant astrocytoma in the elderly: The NOA-08 randomised, phase 3 trial. Lancet Oncol. 2012; 13(7):707–715.
- Richardson TE, Snuderl M, Serrano J, et al. Rapid progression to glioblastoma in a subset of IDH-mutated astrocytomas: A genome-wide analysis. J Neurooncol. 2017;133(1):183–192. doi:10.1007/s11060-017-2431-y
- Louis DN, Perry A, Reifenberger G, et al. The 2016 World Health Organization Classification of Tumors of the Central Nervous System: A summary. Acta Neuropathol. 2016;131(131):803–820.
- Li J, Fang L, Killer HE, Flammer J, Meyer P, Neutzner A. Meningothelial cells as part of the central nervous system host defence. Biol Cell. 2013;105(7):304–315.
- Abedalthagafi MS, Merrill PH, Bi WL, et al. Angiomatous meningiomas have a distinct genetic profile with multiple chromosomal polysomies including polysomy of chromosome 5. Oncotarget. 2014;5(21):10596–10606.
- Riemenschneider MJ, Perry A, Reifenberger G. Histological classification and molecular genetics of meningiomas. Lancet Neurol. 2006; 5(12):1045–1054.
- Maes L, Van Neste L, Van Damme K, et al. Relation between telomerase activity, hTERT and telomere length for intracranial tumours. Oncol Rep. 2007;18(6):1571–1576.
- Kheirollahi M, Koulivand L. Telomere structure and its role in DNA damage and genetic disorders. Journal of Isfahan Medical School. 2012;30(222):1730–1744.
- Kheirollahi M, Kolahdouz M, Ahangari F, Koulivand L, Khorvash F. The role of telomere in cell: Telomere dysfunction and tumorigenesis. Journal of Isfahan Medical School. 2013;30(222):2554–2583.
- Khosravi-Maharlooei M, Jaberipour M, Tashnizi AH, Attar A, Amirmoezi F, Habibagahi M. Expression pattern of alternative splicing variants of human telomerase reverse transcriptase (hTERT) in cancer cell lines was not associated with the origin of the cells. Int J Mol Cell Med. 2015;4(2):109–119.
- Hsu C-P, Lee L-W, Shai S-E, Chen C-Y. Clinical significance of telomerase and its associate genes expression in the maintenance of telomere length in squamous cell carcinoma of the esophagus. World J Gastroenterol. 2005;11(44):6941–6947.
- Dagarag M, Evazyan T, Rao N, Effros RB. Genetic manipulation of telomerase in HIV-specific CD8+ T cells: Enhanced antiviral functions accompany the increased proliferative potential and telomere length stabilization. J Immunol. 2004;173(10):6303–6311.
- Hosgood HD, Cawthon R, He X, Chanock S, Lan Q. Genetic variation in telomere maintenance genes, telomere length, and lung cancer susceptibility. Lung Cancer. 2009;66(2):157–161.
- Kheirollahi M, Mehrazin M, Kamalian N, Mohammadi-asl M, Mehdipour M. Telomerase activity in human brain tumors: Astrocytoma and meningioma. Cell Mol Neurobiol. 2013;33(4):569–574.
- Kheirollahi M, Mehrazin M, Kamalian N, Mehdipour P. Alterations of telomere length in human brain tumors. Med Oncol. 2011;28(3):864–870.
- Khaw AK, Silasudjana M, Banerjee B, Suzuki M, Baskar R, Hande MP. Inhibition of telomerase activity and human telomerase reverse transcriptase gene expression by histone deacetylase inhibitor in human brain cancer cells. Mutat Res. 2007;625(1):134–144.
- Hathcock KS, Jeffrey Chiang Y, Hodes RJ. In vivo regulation of telomerase activity and telomere length. Immunol Rev. 2005;205(1):104–113.
- Artandi SE, Attardi LD. Pathways connecting telomeres and p53 in senescence, apoptosis, and cancer. Biochem Biophys Res Commun. 2005;331(3):881–890.
- Chau MN, El Touny LH, Jagadeesh S, Banerjee PP. Physiologically achievable concentrations of genistein enhance telomerase activity in prostate cancer cells via the activation of STAT3. Carcinogenesis. 2007;28(11):2282–2290.
- Kim CH, Cheong JH, Bak KH, Kim JM, Oh SJ. Prognostic implication of telomerase activity in patients with brain tumors. J Korean Med Sci. 2006;21(1):126–130.
- Dome JS, Chung S, Bergemann T, et al. High telomerase reverse transcriptase (hTERT) messenger RNA level correlates with tumor recurrence in patients with favorable histology Wilms’ tumor. Cancer Res. 1999;59(17):4301–4307.
- Mavrogiannou E, Strati A, Stathopoulou A, Tsaroucha EG, Kaklamanis L, Lianidou ES. Real-time RT-PCR quantification of human telomerase reverse transcriptase splice variants in tumor cell lines and non-small cell lung cancer. Clin Chem. 2007;53(1):53–61.
- Dong W, Qian Y, Yang L. Telomerase, hTERT and splice variants in patients with myelodysplastic syndromes. Leuk Res. 2014;38(7): 830–835.
- Ulaner GA, Hu JF, Vu TH, Oruganti H, Giudice LC, Hoffman AR. Regulation of telomerase by alternate splicing of human telomerase reverse transcriptase (hTERT) in normal and neoplastic ovary, endometrium and myometrium. Int J Cancer. 2000;85(3):330–335.
- Bollmann FM. Physiological and pathological significance of human telomerase reverse transcriptase splice variants. Biochimie. 2013; 95(11):1965–1970.
- Yi X, Shay JW, Wright WE. Quantitation of telomerase components and hTERT mRNA splicing patterns in immortal human cells. Nucleic Acids Res. 2001;29(23):4818–4825.
- Zhu S, Rousseau P, Lauzon C, Gandin V, Topisirovic I, Autexier C. Inactive C-terminal telomerase reverse transcriptase insertion splicing variants are dominant-negative inhibitors of telomerase. Biochimie. 2014;101:93–103.
- Sæbøe-Larssen S, Fossberg E, Gaudernack G. Characterization of novel alternative splicing sites in human telomerase reverse transcriptase (hTERT): Analysis of expression and mutual correlation in mRNA isoforms from normal and tumour tissues. BMC Mol Biol. 2006;7(1):26. doi:10.1186/1471-2199-7-26
- Kheirollahi M, Mehrazin M, Kamalian N, Mohammadi-asl J, Mehdipour P. Telomerase activity in human brain tumors: Astrocytoma and meningioma. Cell Mol Neurobiol. 2013;33(4):569–574.
- Le S, Zhu JJ, Anthony DC, Greider CW, Black PM. Telomerase activity in human gliomas. Neurosurgery. 1998;42(5):1120–1124.
- Shervington A, Patel R. Differential hTERT mRNA processing between young and older glioma patients. FEBS Lett. 2008;582(12):1707–1710.
- Kotoula V, Barbanis S, Nikolakaki E, Koufoyannis D, Papadimitriou C, Karkavelas G. Relative expression of human telomerase catalytic subunit (hTERT) transcripts in astrocytic gliomas. Acta Neuropathol. 2004;107(5):443–451.
- Fajkus J, Borsky M, Kunická Z, et al. Changes in telomerase activity, expression and splicing in response to differentiation of normal and carcinoma colon cells. Anticancer Res. 2002;23(2B):1605–1612.
- Nicholson P, Yepiskoposyan H, Metze S, Orozco RZ, Kleinschmidt N, Mühlemann O. Nonsense-mediated mRNA decay in human cells: Mechanistic insights, functions beyond quality control and the double-life of NMD factors. Cell Mol Life Sci. 2010;67(5):677–700.
- Yi X, White DM, Aisner DL, Baur JA, Wright WE, Shay JW. An alternate splicing variant of the human telomerase catalytic subunit inhibits telomerase activity. Neoplasia. 2000;2(5):433–440.
- Falchetti ML, Pallini R, Larocca LM, Verna R, D’Ambrosio E. Telomerase expression in intracranial tumours: Prognostic potential for malignant gliomas and meningiomas. J Clin Pathol. 1999;52(3):234–236.
- Lincz LF, Mudge L-M, Scorgie FE, Sakoff JA, Hamilton CS, Seldon M. Quantification of hTERT splice variants in melanoma by SYBR green real-time polymerase chain reaction indicates a negative regulatory role for the β deletion variant. Neoplasia. 2008;10(10):1131–1137.
- Liu Y, Wu B-q, Zhong H-h, Tian X-x, Fang W-g. Quantification of alternative splicing variants of human telomerase reverse transcriptase and correlations with telomerase activity in lung cancer. PLoS One. 2012;7(6):e38868. doi:10.1371/journal.pone.0038868
- Colgin LM, Wilkinso C, Englezou A, Kilian A, Robinson MO, Reddel RR. The hTERTα splice variant is a dominant negative inhibitor of telomerase activity. Neoplasia. 2000;2(5):426–432.