A new study suggests that a combination of an ATR inhibitor with cisplatin or a PARP inhibitor would be a treatment worth investigating for synovial sarcoma:
SE Jones, EDG Fleuren, J Frankum, A Konde, CT Williamson, DB Krastev, HN Pemberton, J Campbell, A Gulati, R Elliott, M Menon, JL Selfe, R Brough, SJ Pettitt, W Niedzwiedz, WTA van der Graaf, J Shipley, A Ashworth and CJ Lord,
Cancer research , 2017 15 12
Synovial sarcoma (SS) is an aggressive soft-tissue malignancy characterized by expression of SS18-SSX fusions, where treatment options are limited. To identify therapeutically actionable genetic dependencies in SS, we performed a series of parallel, high-throughput small interfering RNA (siRNA) screens and compared genetic dependencies in SS tumor cells with those in >130 non-SS tumor cell lines. This approach revealed a reliance of SS tumor cells upon the DNA damage response serine/threonine protein kinase ATR. Clinical ATR inhibitors (ATRi) elicited a synthetic lethal effect in SS tumor cells and impaired growth of SS patient-derived xenografts. Oncogenic SS18-SSX family fusion genes are known to alter the composition of the BAF chromatin-remodeling complex, causing ejection and degradation of wild-type SS18 and the tumor suppressor SMARCB1. Expression of oncogenic SS18-SSX fusion proteins caused profound ATRi sensitivity and a reduction in SS18 and SMARCB1 protein levels, but an SSX18-SSX1 Δ71-78 fusion containing a C-terminal deletion did not. ATRi sensitivity in SS was characterized by an increase in biomarkers of replication fork stress (increased γH2AX, decreased replication fork speed, and increased R-loops), an apoptotic response, and a dependence upon cyclin E expression. Combinations of cisplatin or PARP inhibitors enhanced the antitumor cell effect of ATRi, suggesting that either single-agent ATRi or combination therapy involving ATRi might be further assessed as candidate approaches for SS treatment. Cancer Res; 77(24); 7014-26. ©2017 AACR.
Such treatment is being investigated right now for refractory solid tumors:
Veliparib (ABT-888), an Oral PARP Inhibitor, and VX-970, an ATR Inhibitor, in Combination With Cisplatin in People With Refractory Solid Tumors - Full Text View.