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

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.

ALT Positivity in Human Cancers: Prevalence and Clinical Insights

“…The first strategy is the use of ATR inhibitors against ALT+ cell lines, which initially showed great promise as a potential targeted therapy for ALT cancers [ 61 ]. However, a few recent studies challenged the specificity of ATR inhibitors towards ALT cancers [ 183 , 188 , 189 ]. ATR is an important kinase that functions in a variety of DNA damage response (DDR) pathways, including the activation of replication stress checkpoint and HR [ 190 , 191 ].…”

“…Using the identical inhibitor (VE-821) as well as the same OS cell lines and assays, they argued that Flynn and colleagues’ original findings were confounded by a lack of control for the well-established variable growth rates of the assessed cell lines. Most recently, Goncalves and colleagues demonstrated that ATR inhibitor sensitivity in OS appears to be another TMM-independent therapeutic modality [ 189 ]. Using a panel of eight ALT+ OS and nine ALT− OS, they assessed the efficacy of three ATR inhibitors, AZD-6738, VE-822, and BAY-1895344.…”

“…For other ATR inhibitors, there was no TMM-dependent statistical difference. Second, ALT− OS with short telomeres were the most sensitive to ATR inhibition [ 189 ]. These results are consistent with recent studies in Ewing Sarcoma, a ubiquitously ALT− bone tumor ( Table 2 ), showing sensitivity to ATR inhibition [ 192 ] and similar ALT-independent ATR inhibitor sensitivity found in multiple soft tissue sarcomas including leiomyosarcoma, myxofibrosarcoma, and well-differentiated or de-differentiated LPS [ 183 ].…”

“…Most recently, Goncalves and colleagues demonstrated that ATR inhibitor sensitivity in OS appears to be another TMM-independent therapeutic modality [189]. Using a panel of eight ALT+ OS and nine ALT− OS, they assessed the efficacy of three ATR inhibitors, AZD-6738, VE-822, and BAY-1895344.…”

Patient Derived Xenografts for Genome-Driven Therapy of Osteosarcoma

“…Matched treatment recommendations based on genomic profiling and in vivo PDX drug testing results will be made available, potentially providing patients with individualized cancer treatment options. In the phase 2 clinical study (NCT04417062) proposed by the Dana-Farber Cancer Institute to evaluate the effectiveness of using two drugs (olaparib and ceralasertib) to treat patients with OS that have not responded to conventional treatments, the derivation of PDX models and paired pre/post-treatment tumor samples are included and may offer additional treatment opportunities [ 101 , 102 ].…”