Supplementary Material for: Telomeric associations correlate with telomere length reduction and clonal chromosome aberrations in giant cell tumor of bone

Giant cell tumor of bone (GCTB) is characterized cytogenetically by frequent telomeric associations (tas). To explore the mechanisms behind the formation of tas in GCTB and to investigate their karyotypic consequences, the frequencies of tas and clonal aberrations other than tas in 20 GCTBs were compared to telomere length and status, as assessed by quantitative PCR, fluorescence in situ hybridization (FISH), and expression levels of four genes involved in telomere maintenance. Based on the G-banding results, the tumors were divided into two groups, one with a high frequency of tas and one with a low frequency. Clonal aberrations were found to be restricted to the group with a high level of tas, and the same group showed a significantly larger reduction in telomere length in tumor cells compared to peripheral blood cells. Furthermore, 65 out of 66 tas analyzed by FISH were negative for telomeric sequences. The expression levels of <i>TERT, TERF1, TERF2, </i>and <i>POT1 </i>did not correlate with telomere length or the frequency of tas. Thus, the present findings provide strong support for the notion that decreased telomere length is a prerequisite for tas in GCTBs and that the clonal changes occurring in GCTBs are derived from tas.

骨巨细胞瘤（Giant cell tumor of bone, GCTB）的细胞遗传学特征为频繁出现端粒关联（telomeric associations, tas）。为探究GCTB中tas形成的机制并分析其核型相关影响，本研究通过定量聚合酶链反应（quantitative PCR）、荧光原位杂交（fluorescence in situ hybridization, FISH）以及4个端粒维持相关基因的表达水平，对比分析了20例GCTB中tas的发生频率、除tas外的克隆性染色体异常发生率，以及其与端粒长度和端粒状态的关联。根据G显带检测结果，将受试肿瘤分为tas高频率组与tas低频率组。结果显示，克隆性染色体异常仅局限于tas高频率组，且该组肿瘤细胞的端粒长度较外周血细胞出现显著缩短。此外，经FISH分析的66例tas样本中，有65例未检测到端粒序列。TERT、TERF1、TERF2及POT1的表达水平与端粒长度或tas发生频率均无显著相关性。综上，本研究结果为‘端粒长度缩短是GCTB中tas形成的先决条件，且GCTB所发生的克隆性改变均源于tas’这一观点提供了强有力的实验依据。