Functional loss of ATRX and TERC activates Alternative Lengthening of Telomeres (ALT) in LAPC4 prostate cancer cells

Mindy K. Graham, Jiyoung Kim, Joseph Da, Jacqueline A. Brosnan-Cashman, Anthony Rizzo, Javier A.Baena Del Valle, Lionel Chia, Michael Rubenstein, Christine Davis, Qizhi Zheng, Leslie Cope, Michael Considine, Michael Haffner, Angelo M. De Marzo, Alan K. Meeker, Christopher M. Heaphy

Research output: Contribution to journalArticle

Abstract

A key hallmark of cancer, unlimited replication, requires cancer cells to evade both replicative senescence and potentially lethal chromosomal instability induced by telomere dysfunction. The majority of cancers overcome these critical barriers by upregulating telomerase, a telomere-specific reverse transcriptase. However, a subset of cancers maintains telomere lengths by the telomerase-independent Alternative Lengthening of Telomeres (ALT) pathway. The presence of ALT is strongly associated with recurrent cancer-specific somatic inactivating mutations in the ATRX-DAXX chromatin-remodeling complex. Here, we generate an ALT-positive adenocarcinoma cell line following functional inactivation of ATRX and telomerase in a telomerase-positive adenocarcinoma cell line. Inactivating mutations in ATRX were introduced using CRISPR-cas9 nickase into two prostate cancer cell lines, LAPC-4 (derived from a lymph node metastasis) and CWR22Rv1 (sourced from a xenograft established from a primary prostate cancer). In LAPC-4, but not CWR22Rv1, abolishing ATRX was sufficient to induce multiple ALT-associated hallmarks, including the presence of ALT-associated promyelocytic leukemia bodies (APB), extrachromosomal telomere C-circles, and dramatic telomere length heterogeneity. However, telomerase activity was still present in these ATRXKO cells. Telomerase activity was subsequently crippled in these LAPC-4 ATRXKO cells by introducing mutations in the TERC locus, the essential RNA component of telomerase. These LAPC-4 ATRXKO TERCmut cells continued to proliferate long-term and retained ALT-associated hallmarks, thereby demonstrating their reliance on the ALT mechanism for telomere maintenance.

Original languageEnglish (US)
Pages (from-to)2480-2491
Number of pages12
JournalMolecular Cancer Research
Volume17
Issue number12
DOIs
StatePublished - Jan 1 2019

ASJC Scopus subject areas

  • Molecular Biology
  • Oncology
  • Cancer Research

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    Graham, M. K., Kim, J., Da, J., Brosnan-Cashman, J. A., Rizzo, A., Del Valle, J. A. B., Chia, L., Rubenstein, M., Davis, C., Zheng, Q., Cope, L., Considine, M., Haffner, M., De Marzo, A. M., Meeker, A. K., & Heaphy, C. M. (2019). Functional loss of ATRX and TERC activates Alternative Lengthening of Telomeres (ALT) in LAPC4 prostate cancer cells. Molecular Cancer Research, 17(12), 2480-2491. https://doi.org/10.1158/1541-7786.MCR-19-0654