Abstract 1697P
Background
High-grade serous ovarian cancer (HGSOC) is characterised by extensive intratumoral heterogeneity, which is associated with drug resistance. Our objective is to investigate the clonal dynamics effects of carboplatin (C), paclitaxel (P) and olaparib (O) in in-vivo and in-vitro HGSOC models.
Methods
We tracked clonal evolution in PEO1 (BRCA2-mutant) and UWB1.289 (non-BRCA-mutant) HGSOC cell line models by lentiviral transfection with a barcode (BC) library (CloneTrackerXP). Barcoded cells were grown in HYPERflasks, and exposed to C, P, and O, till cell population reduction to < 10% (bottleneck). Following that, drug pressure was removed, allowing cells to regrow (N=3). NGS was used to quantify BCs in the final cell populations and in the dead floating cells collected weekly from the culture media (to get information on the temporal dynamics). Barcoded cells were also implanted subcutaneously in NSG mice. Heterogeneity of the cell populations was estimated using the Shannon diversity index (SDI).
Results
For PEO1, the SDI of non-treated cells was 6.31 for C and 6.19 for P and O. After drug exposure, the SDI was reduced to 3.21, 2.52 and 4.75 respectively. A similar pattern of heterogeneity reduction was observed post-treatment in UWB1.289. Cell populations exposed to C and O share similar clonal selection, and, strikingly, pre-existing polyclonal drug resistance was demonstrated in both cell lines. Our in-vivo experiment showed that the average number of BCs remains stable during tumour growth, indicating minimal clonal extinction once tumour is established and without drug intervention.
Conclusions
For the first time, it was demonstrated that resistance to C, P and O pre-exists drug exposure in HGSOC models regardless of BRCA status, and drug treatment selects for resistant phenotypes. Heterogeneity followed by O therapy is greater than by C in a BRCA-mutant cell line. Regardless of BRCA status, the cell populations post-drug selection share more similarities in the C and O groups when compared to P-exposed cells, which suggests a correlation between the mechanism of action of drugs and drug resistance. Our results indicate that evolutionary dynamics are largely deterministic and hence can be used to predict patient outcomes and personalise treatments.
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
The Institute of Cancer Research.
Funding
Cancer Research UK / NIHR - National Institute for Health Research.
Disclosure
S. Banerjee: Financial Interests, Personal, Advisory Board: Amgen, Genmab, Immunogen, Mersana, Merck Sereno, MSD, Roche, Tesaro, AstraZeneca, GSK, Oncxerna; Financial Interests, Personal, Invited Speaker: Clovis, Pfizer, Tesaro, AstraZeneca, GSK, Takeda, Amgen, Medscape, Research to Practice, Peerview; Financial Interests, Personal, Stocks/Shares: PerciHealth; Financial Interests, Institutional, Research Grant: AstraZeneca, GSK, Tesaro; Non-Financial Interests, Principal Investigator, Phase II clinical trial Global lead, ENGOTov60/GOG3052/RAMP201: Verastem; Non-Financial Interests, Principal Investigator, ENGOT-GYN1/ATARI phase II international trial (academic sponsored): AstraZeneca; Non-Financial Interests, Advisory Role: Epsilogen; Non-Financial Interests, Other, Member of membership committee: ESGO; Non-Financial Interests, Advisory Role, Medical advisor to UK ovarian cancer charity: Ovacome Charity; Non-Financial Interests, Other, Received research funding from UK based charity I have provided medical advice (non-remunerated): Lady GardenFoundation Charity. U. Banerji: Financial Interests, Personal, Advisory Board, Advisory Board Member: Pegasy; Financial Interests, Personal, Full or part-time Employment, Employed by the Institute of Cancer Research: The Institute of Cancer Research; Financial Interests, Institutional, Research Grant: BTG international, Carrick Therapeutics, Chugai, Verastem Oncology; Non-Financial Interests, Principal Investigator: Various pharma companies. All other authors have declared no conflicts of interest.