Intratumoral diversity of telomere length in individual neuroblastoma tumors

Abstract

The purpose of the work was to investigate telomere length (TL) and mechanisms involved in TL maintenance in individual neuroblastoma (NB) tumors. Primary NB tumors from 102 patients, ninety Italian and twelve Spanish, diagnosed from 2000 to 2008 were studied. TL was investigated by quantitative fluorescence in situ hybridization (IQ-FISH) that allows to analyze individual cells in paraffin-embedded tissues. Fluorescence intensity of chromosome 2 centromere was used as internal control to normalize TL values to ploidy. Human telomerase reverse transcriptase (hTERT) expression was detected by immunofluorescence in 99/102 NB specimens.The main findings are the following: 1) two intratumoral subpopulations of cancer cells displaying telomeres of different length were identified in 32/102 tumors belonging to all stages. 2) hTERT expression was detected in 99/102 tumors, of which 31 displayed high expression and 68 low expression. Alternative lengthening of telomeres (ALT)-mechanism was present in 60/102 tumors, 20 of which showed high hTERT expression. Neither ALT-mechanism nor hTERT expression correlated with heterogeneous TL. 3) High hTERT expression and ALT positivity were associated with significantly reduced Overall Survival. 4) High hTERT expression predicted relapse irrespective of patient age. Intratumoral diversity in TL represents a novel feature in NB.In conclusion, diversity of TL in individual NB tumors was strongly associated with disease progression and death, suggesting that these findings are of translational relevance. The combination of high hTERT expression and ALT positivity may represent a novel biomarker of poor prognosis that deserves further investigation.

ALTernative Telomere Maintenance and Cancer

“…However, there is no universal definition for ALT activity and most studies of patient samples investigate only one or two of the phenotypic markers. Additionally, tumors can have intratumoral heterogeneity in telomere lengths and TMM activity, with ALT and telomerase functioning in different cells within the same tumor [23,27]. Therefore, it is possible that the prevalence of ALT may be over- or under- represented by the markers currently used.…”

“…Indeed, utilization of ALT confers a poor prognosis in most settings, such as neuroblastoma and certain soft tissue sarcomas [21,23,42,43,45,63]. It can be speculated that this phenomenon is due to the chromosomal instability of these tumors, which may confer resistance to therapies [21].…”

Alternative Lengthening of Telomeres (ALT) in Tumors and Pluripotent Stem Cells

“…Nevertheless, the coexistence of ALT and telomerase has been identified both in vitro and in vivo [28,119]. Interestingly, osteosarcoma and neuroblastoma are characterized by inner-tumoral heterogeneity in TMM, where ALT and telomerase activity exist in different cells of the same tumor [120][121][122]. In contrast, breast cancer samples have revealed both telomerase and ALT within the same cell [123].…”

Neuroblastoma: morphological pattern, molecular genetic features, and prognostic factors

“…Все нейробластомы с амплификацией гена MYCN демонстрируют высокую теломеразную активность (это ассоциировано с плохим прогнозом и высокой генетической нестабильностью). Однако большинство нейробластом стадии IVS имели низкую теломеразную активность или короткие теломеры [5,36,37]. Таким образом, длина теломер является весьма важным прогностическим параметром клинической значимости у больных с диагнозом нейробластомы [38].…”