Abstract 3002: The PARP inhibitor, Rucaparib enhance the sensitivity to Trabectedin in soft tissue sarcomas cell lines and in patient xenograft model
Authors: Audrey Laroche-Clary , Vanessa Chaire , Marie Karanian , Antoine Italiano 
Published: July 2016

Background: Soft tissue sarcomas (STS) constitute a group of rare tumors and represent less than 1% of all adult cancer. Trabectedin (trabectedin®) is a synthetic molecule derived from Caribean tunicate and is a potent antitumor agent approved for patients with advanced STS. Trabectedin binds to minor groove and interferes with the DNA repair pathway, cell cycle and interacts with transcription factors. PARP-1 and 2 are two proteins implicated in DNA repair; in response to DNA damage, PARP binds to sites of damage and catalyzes the poly (ADP-ribosyl)ation of target proteins and recruit proteins at the DNA break. The aim of this study was to evaluate if the antitumor activity of Trabectedin is potentiated by PARP inhibitor, Rucaparib, in preclinical model of liposarcoma dedifferentiated and leimyosarcoma cell lines and in a patient-derived xenograft (PDX) model.

Methods: The LPS cell lines (IB115, IB111), the LMS cells (IB136) and the PDX model have been established from human surgical specimens tumor in our laboratory, after obtaining written informed patient consent. Cells were exposed for 72h to an increasing concentration range of Trabectedin, Rucaparib or drugs in combination and viability was assessed by the MTT assay. Apoptosis was assessed by Annexin V/PI staining and cell cycle analysis was studied by DNA content by fluorescence-activated cells sorting, apoptosis and cycle cell results were analyzed using the Cell Quest Pro software (BD Biosciences, San Jose, USA). DNA strand breaks were evaluated by testing for the presence of intranuclear foci γH2ax after 48h of treatment with drugs alone or in combination by immunofluorescence and microscopy confocal analysis. Combination drugs analysis was also assessed in patient-derived xenograft mice model.

Results: As expected, sarcoma cells are very sensitive to Trabectedin (IC50 were comprised between 0.0007μM and 0.02μM), Rucaparib was less effective on proliferation with a median of IC50 at 12μM ± 5μM. The combination of Rucaparib and Trabectedin is highly synergistic, inhibiting cell proliferation, inducing apoptosis, and the accumulation of G2/M. By using the Chou-Talalay method for drug combination, we observed index combination ranging from 0.3 to 0.8. The drug combination also enhanced γH2AX intranuclear accumulation as a result of DNA damage induction. The effect of the drug combination was corroborated in vivo by using a STS patient-derived xenograft (PDX) models in which the tumors showed sustained regression.

Conclusion: The combination of Trabectedin and Rucaparib is highly synergistic in pre-clinical models of STS and is worth to investigate in the clinical setting.

Citation Format: Laroche-Clary Audrey, Chaire Vanessa, Karanian Marie, Italiano Antoine. The PARP inhibitor, Rucaparib enhance the sensitivity to Trabectedin in soft tissue sarcomas cell lines and in patient xenograft model. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3002.