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Updated: Aug 19, 2026
Utilizing Murine Inducible Telomerase Alleles in the Studies of Tissue Degeneration/Regeneration and Cancer
Published on: April 13, 2015
Evidence for inactivation of distinct telomerase repressor genes in different types of human cancers
Hiromi Tanaka1, Izumi Horikawa, J Carl Barrett
1Department of Molecular and Cell Genetics, School of Life Sciences, Faculty of Medicine, Tottori University, Tottori, Japan. hirtanak@iupui.edu
Abstract:
Telomerase activation, a critical event in human carcinogenesis, may result from defects in telomerase-repressing mechanisms. Data from microcell-mediated chromosome transfer (MMCT) suggests the presence of telomerase repressor genes that become inactivated during carcinogenic processes. The transfer of a normal human chromosome 3 represses telomerase activity of both human renal cell carcinoma (RCC) and breast carcinoma (BC) cells. For a genetic complementation analysis of telomerase repression, 2 RCC cell lines (KC12 and RCC23) and a BC cell line (21NT) were used to make somatic cell hybrids. All of the self-hybrids (KC12 x KC12 and 21NT x 21NT) and hybrids from 2 RCC cell lines (KC12 x RCC23) expressed the telomerase activity similarly to their parental cells, excluding the possibility of a ploidy-associated change in telomerase activity and suggesting the same genetic defect shared by the 2 RCC cell lines. In contrast, the fusion of BC and RCC cells (21NT x KC12 and 21NT x RCC23) produced a significant number of telomerase-negative hybrids, suggesting that the RCC and BC cells have different defects in the telomerase repression, which are functionally corrected through genetic complementation in the hybrids. This notion was supported by the mapping of the RCC telomerase repressor gene to a 5.7-Mb region on 3p21, which is different from the candidate region for the BC telomerase repressor gene on the same chromosomal band. These findings provide direct evidence for inactivation of distinct telomerase repressor genes in different types of human cancers and may have implications in the tissue-specific regulation of telomerase during human development and carcinogenesis.
Insights
Telomerase activation in cancer may stem from faulty repressor genes. This study shows distinct chromosome 3 defects in renal and breast cancers, corrected by gene complementation, revealing separate inactivation pathways in carcinogenesis.
Area of Science:
- Cancer Biology
- Genetics
- Molecular Oncology
Background:
- Telomerase activation is crucial for human carcinogenesis.
- Defects in telomere-repressing mechanisms are implicated in cancer development.
- Previous studies suggest the existence of telomerase repressor genes inactivated during cancer progression.
Purpose of the Study:
- To investigate the genetic basis of telomerase repression defects in human cancers.
- To determine if different cancer types share common or distinct telomerase repressor genes.
- To identify candidate regions for telomerase repressor genes on human chromosome 3.
Main Methods:
- Microcell-mediated chromosome transfer (MMCT) was used to introduce normal human chromosome 3.
- Somatic cell hybrids were generated by fusing renal cell carcinoma (RCC) and breast carcinoma (BC) cell lines.
- Telomerase activity was assessed in parental cells and resulting hybrid cell lines.
Main Results:
- Fusion of two RCC cell lines or two BC cells did not alter telomerase activity, indicating a shared defect in RCCs.
- Fusion of BC and RCC cells resulted in telomerase-negative hybrids, suggesting complementation of distinct defects.
- The RCC telomerase repressor gene was mapped to 3p21, distinct from the candidate BC repressor gene locus on the same band.
Conclusions:
- Provides direct evidence for the inactivation of distinct telomerase repressor genes in different human cancers.
- Highlights the role of specific genetic defects in telomerase regulation during carcinogenesis.
- Suggests implications for tissue-specific telomerase regulation in human development and cancer.
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