Selective Elimination of Osteosarcoma Cell Lines with Short Telomeres by Ataxia Telangiectasia and Rad3-Related Inhibitors.

Caterina Mancusi,Sandra J. Strauss,Tomas Goncalves,Kazunori Tomita,Georgia Zoumpoulidou,Carlos Alvarez-Mendoza,Sibylle Mittnacht,Laura C. Collopy

doi:10.1021/acsptsci.0c00125

Caterina Mancusi, Sandra J. Strauss + Show 6 more

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https://doi.org/10.1021/acsptsci.0c00125

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Abstract

To avoid replicative senescence or telomere-induced apoptosis, cancers employ telomere maintenance mechanisms (TMMs) involving either the upregulation of telomerase or the acquisition of recombination-based alternative telomere lengthening (ALT). The choice of TMM may differentially influence cancer evolution and be exploitable in targeted therapies. Here, we examine TMMs in a panel of 17 osteosarcoma-derived cell lines, defining three separate groups according to TMM and the length of telomeres maintained. Eight were ALT-positive, including the previously uncharacterized lines, KPD and LM7. While ALT-positive lines all showed excessive telomere length, ALT-negative cell lines fell into two groups according to their telomere length: HOS-MNNG, OHSN, SJSA-1, HAL, 143b, and HOS displayed subnormally short telomere length, while MG-63, MHM, and HuO-3N1 displayed long telomeres. Hence, we further subcategorized ALT-negative TMM into long-telomere (LT) and short-telomere (ST) maintenance groups. Importantly, subnormally short telomeres were significantly associated with hypersensitivity to three different therapeutics targeting the protein kinase ataxia telangiectasia and Rad3-related (ATR) (AZD-6738/Ceralasertib, VE-822/Berzoserib, and BAY-1895344) compared to long telomeres maintained via ALT or telomerase. Within 24 h of ATR inhibition, cells with short but not long telomeres displayed chromosome bridges and underwent cell death, indicating a selective dependency on ATR for chromosome stability. Collectively, our work provides a resource to identify links between the mode of telomere maintenance and drug sensitivity in osteosarcoma and indicates that telomere length predicts ATR inhibitor sensitivity in cancer.

Highlights

To avoid replicative senescence or telomere-induced apoptosis, cancers employ telomere maintenance mechanisms (TMMs) involving either the upregulation of telomerase or the acquisition of recombination-based alternative telomere lengthening (ALT)
In telomerase-expressing normal cells, telomerase preferentially elongates the shortest telomeres to extend overall telomere length.[18,19]. Such telomerase action appears to be compromised in cancer cells, resulting in retention of critically short telomeres and inefficient telomere lengthening.[20−22] These cancer cells evade activation of the DNA repair machinery or senescence pathways caused by shortened telomeres; the mechanisms to maintain such short telomeres by telomerase are thought to be unique to cancer.[2,21]
C-circles were detected through rolling circle amplification (RCA) followed by quantification of telomeric sequences using either dot-blot hybridization or monochrome-multiplex quantitative polymerase chain reaction (MM-qPCR) (Figures 1a and S-1a)

Summary

Introduction

To avoid replicative senescence or telomere-induced apoptosis, cancers employ telomere maintenance mechanisms (TMMs) involving either the upregulation of telomerase or the acquisition of recombination-based alternative telomere lengthening (ALT). We further subcategorized ALT-negative TMM into long-telomere (LT) and short-telomere (ST) maintenance groups. Telomeres are the protective ends of chromosomes, essential for all dividing cells.[1] While telomeres shorten with every chromosome replication cycle due to the endreplication problem, critically shortened telomeres elicit DNA damage checkpoint activation, leading to replicative senescence or apoptosis.[2] The vast majority of cancer cells maintain the ends of their chromosomes through a telomere maintenance mechanism (TMM), thereby avoiding senescence or death induced by critically shortened telomeres.[3] In about 90% of cancers, the reverse transcriptase enzyme telomerase, which replenishes telomeric DNA, is reactivated, permitting indefinite cell divisions.[4,5] TMMs may be bypassed only in exceptional circumstances where cancer cells retain substantially long telomeres.[6−8]. The cytotoxic effects of telomerase inhibition are not immediate as time is required to achieve telomere attrition and damage accumulation, and cancer cells able to propagate and evolve until their telomeres significantly shorten and become deprotected.[7,8,23,24]

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