Expression of human telomerase reverse transcriptase splice variants is well correlated with low telomerase activity in osteosarcoma cell lines.

The human telomerase reverse transcriptase (hTERT) gene is a catalytic subunit of telomerase that plays an important role in maintaining telomere length. Recently, post-transcriptional (alternative splicing) and epigenetic (promoter methylation) mechanisms affecting expression of the hTERT gene have been reported as negative regulators of telomerase activity (TA). To elucidate the significance of the telomere maintenance mechanism (TMM) in osteosarcoma (OS), we examined hTERT mRNA/protein expression and methylation status in 16 OS cell lines and compared them with TA. Five (31%) of 16 OS cell lines expressed both full-length and splice variants of hTERT mRNA/protein, and 3 (19%) exhibited only full-length hTERT mRNA/protein. No hTERT mRNA/protein expression was observed in 8 cell lines (50%). TA in OS cell lines exhibiting full-length hTERT mRNA/protein without any splice variants was higher than in cell lines expressing splice variants. The promoters of the 16 OS cell lines were relatively hypermethylated, but no inverse relationship between frequency of methyl-CpG sites and hTERT expression was observed. Treatment with a demethylating agent induced hTERT mRNA/protein in only one cell line. These results suggest that the epigenetic mechanism might contribute to the regulation of the hTERT gene in a small subset of OSs, and that alternative splicing might be involved in controlling the TA of OS cell lines, thereby contributing to their TMM.

Solid variant of aneurysmal bone cyst of the cervical spine.

STUDY DESIGN: A case of the solid variant of aneurysmal bone cyst affecting the posterior component of the fourth cervical vertebra is reported. Imaging studies showed an expansile destructive lesion. After curettage, autologous iliac bone grafting with posterior fusion was performed. There was no sign of local recurrence 2 years after surgery. OBJECTIVES: To emphasize the occurrence of the solid variant of aneurysmal bone cyst in the cervical spine. SUMMARY OF BACKGROUND DATA: The solid variant of aneurysmal bone cyst is rare, and only 12 cases occurring in the vertebrae, including 3 in the cervical vertebrae, have been reported. The condition is difficult to diagnose radiologically before biopsy or surgery. METHODS: A 9-year-old girl presented with pain in the nape of the neck without any neurologic deficit. She was found to have the solid variant of aneurysmal bone cyst in the posterior component of the fourth cervical vertebra, which had destroyed the lamina and spinous process. Part of the posterior aspect of the C4 vertebral body was also involved. Curettage of the lesion was performed, and the defect in the posterior component of the vertebra was reconstructed using an autologous iliac bone graft with posterior fusion using a halo vest. RESULTS: Magnetic resonance imaging disclosed a homogeneous low intensity mass at the lamina, spinous process, and vertebral body of C4 on T1-weighted images. The mass showed heterogeneous high signal intensity on Gd-enhanced images. Histologically, the resected specimen showed predominant fibroblastic proliferation, with minor foci of reactive osteoid formation and an area of osteoclast-like giant cells. Neither cellular atypia nor mitotic figures were evident. There was no sign of local recurrence 2 years after surgery. CONCLUSIONS: The solid variant of aneurysmal bone cyst should be included in the differential diagnosis of any lytic expansile lesion of the spine, even though it is a destructive lesion. Gd-enhanced magnetic resonance imaging may be helpful for distinguishing the solid variant from conventional aneurysmal bone cyst.

Human PinX1, a potent telomerase inhibitor, is not involved in human gastrointestinal tract carcinoma.

PinX1 was isolated as a Pin2/TRF1 binding protein that also binds to the telomerase catalytic subunit hTERT. The gene is a potent telomerase inhibitor and a putative tumor suppressor since it inhibits telomerase activity and affects tumorigenicity in nude mice. This study investigated aberrations of PinX1 gene in gastrointestinal tract carcinomas (GITCs). We examined mutations, mRNA expression and promoter methylation of PinX1 gene in 15 GITC cell lines, and 20 patients with primary GITC. We found a missense mutation at codon 254 (AGC/TGC) in a colon and an esophageal carcinoma cell line, and in cancerous and matching normal tissues of 2 patients with primary GITC (10%). It might be a benign polymorphism. No hyper-methylation was found in the promoter region and the treatment by 5-Aza-2'-deoxycytidine did not affect PinX1 mRNA expression level in any of the cell lines. It was concluded that the human PinX1 does not affect tumorigenesis of human GITC.