Poly-ADP-Ribose Polymerase inhibitors (PARPi) constitute a class of drugs that interfere with DNA damage response and are already available or in current advanced development either alone or in combination with DNA damaging agents such as chemotherapeutics. Some features of colorectal cancer (CRC), like microsatellite instability and MAPK-induced replication stress, make it a good candidate for exploring the combination of PARPi with chemotherapeutics. Previous data have evidenced how PARPi/chemotherapy combinations are effective in various cancers, albeit early clinical trials showed only modest activity in unselected CRC patients.
We tested the activity of the PARPi niraparib (MK-4827) used alone or in combination with either 5-fluorouracil, oxaliplatin or irinotecan (SN38) in a panel of 12 CRC cell lines with known molecular characteristics. Proliferation, cell cycle and apoptosis assays were performed. A correlation between combination synergism and the following molecular features was obtained: RAS/BRAF mutation, HER2 amplification, microsatellite status, mutational and transcriptomic profiles from the Cancer Cell Line Encyclopedia (CCLE) database. Mice xenografts using the most representative cell lines are ongoing. Patient-derived 3D primary cultures (PDPCs) are being used to confirm the data obtained in vitro.
Niraparib is synergistic with the investigated chemotherapeutics in most of the cell lines explored. The best candidate for combination is SN38, which is synergistic in 9/12 cell lines analysed. MAPK activation, microsatellite instability (MSI) and mutations in genes involved in homologous recombination repair (HRR) are good predictors of synergism. Transcriptomic analysis is ongoing. Mice xenografts and PDPCs models are in progress and will be presented at the Congress.
The combination of niraparib and irinotecan/SN38 is effective in an in vitro model of CRC. MAPK activation, MSI and mutation in HRR-associated genes are predictors of synergism and are currently being validated in in vivo and ex vivo models. These findings could lead to a better patient selection for this combination in CRC.
The authors.
Università della Campania Luigi Vanvitelli; Associazione Italiana per la Ricerca sul Cancro (AIRC).
P.P. Vitiello: Research grant/Funding (institution), Travel/Accommodation/Expenses: Amgen; Research grant/Funding (institution): Bayer; Research grant/Funding (institution): Ipsen; Research grant/Funding (institution): Merck; Research grant/Funding (institution): Roche; Travel/Accommodation/Expenses: BMS; Travel/Accommodation/Expenses: Sanofi-Genzyme. D. Ciardiello: Travel/Accommodation/Expenses: Sanofi. C. Cardone: Research grant/Funding (institution): Ipsen; Research grant/Funding (institution): Roche; Research grant/Funding (institution): Merck; Research grant/Funding (institution): Amgen; Research grant/Funding (institution): Bayer. G. Martini: Research grant/Funding (self): Amgen. C. Borrelli: Travel/Accommodation/Expenses: BMS. L. Poliero: Travel/Accommodation/Expenses: BMS. V. De Falco: Travel/Accommodation/Expenses: BMS; Travel/Accommodation/Expenses: Novartis. E.F. Giunta: Travel/Accommodation/Expenses: Novartis; Travel/Accommodation/Expenses: BMS. M. Terminiello: Travel/Accommodation/Expenses: BMS. T. Troiani: Research grant/Funding (institution): Roche; Research grant/Funding (institution): Merck; Research grant/Funding (institution): Bayer; Travel/Accommodation/Expenses: Servier; Travel/Accommodation/Expenses: Amgen; Travel/Accommodation/Expenses: Sanofi; Travel/Accommodation/Expenses: Novartis. F. Ciardiello: Advisory/Consultancy, Research grant/Funding (institution): Merck; Advisory/Consultancy, Research grant/Funding (institution): Bayer; Advisory/Consultancy, Research grant/Funding (institution): Amgen; Advisory/Consultancy, Research grant/Funding (institution): Roche; Advisory/Consultancy: Servier; Advisory/Consultancy: Pfizer; Research grant/Funding (institution): Ipsen. E. Martinelli: Honoraria (self), Research grant/Funding (institution): Amgen; Honoraria (self), Research grant/Funding (institution): Bayer; Honoraria (self), Research grant/Funding (institution): Merck; Research grant/Funding (institution): Roche; Honoraria (self), Research grant/Funding (institution): Servier. All other authors have declared no conflicts of interest.