Poster Presentation Melbourne Immunotherapy Network Winter Symposium 2021

Ovarian carcinosarcoma engrafted in NSG MHCnull mice as a pre-clinical patient derived xenograft (PDX) model to explore personalised T-cell receptor therapy  (#112)

Gwo Ho 1 2 , Jessica Wu 2 , Holly Barker 3 4 , Tu Nguyen-Dumont 2 5 , Janet Chang 2 , Ashleigh Fell 2 , Peter Eggenhuizen 2 , Jason Steen 2 , Tom Manolitsas 1 , Pouya Faridi 6 , Sophia Frentzas 1 , Stafford Fox Rare Cancer Program 4 , Justin Bedo 4 7 , Cassandra Vandenberg 3 4 , Tony Papenfuss 3 4 , Clare Scott 3 4 , Joshua Ooi 2 , Eva Segelov 1 2
  1. Monash Health, Clayton, VIC, Australia
  2. School of Clinical Sciences, Monash University, Clayton , Victoria
  3. Department of Medical Biology, University of Melbourne, Parkville
  4. Walter and Eliza Hall Institute of Medical Research, Parkville, VIC, Australia
  5. Department of Clinical Pathology, University of Melbourne, Parkville
  6. Monash Biomedicine Discovery Institute, Monash University, Clayton
  7. Department of Computing and Information Systems, University of Melbourne, Parkville

Ovarian carcinosarcoma (OCS) are rare and aggressive cancers with poor prognosis due to limited effective treatments1. OCS tumorigenesis is not driven by tumour somatic mutation but via reprogramming of gene expression. Therefore, the tumour mutation burden (TMB) in OCS is often low and these tumours are relatively non-responsive to single agent immunotherapy, i.e. immunologically “cold”2.

Here we describe an OCS pre-clinical model, SFRC01177, where the tumour has been established subcutaneously in NOD-scid IL2Rgammanull (NSG) MHCnull mice. These NSG MHCnull mice are deficient in MHC class I/II expression, thus lacking acute graft-versus-host disease following injection of human peripheral mononuclear cells3. The tumour in vivo platinum chemotherapy refractory response was consistent with the patient’s clinical outcome.

Whole genome and exome sequencing together with RNA sequencing were performed on the tumour for tumour neoantigen (TNA) discovery. Despite a low TMB of <4 mutations/Mb, up to 5500 predicted neoantigens have been identified in-silico to bind to the patient’s human leukocyte antigen (HLA) class I complexes and thus presented to CD8+ T-cytotoxic cells. Mutant MHC-bound neo-epitopes are now being assessed using nano-ultra-performance liquid chromatography coupled to high-resolution mass spectrometry based on the predicted mutant TNAs.

One million HLA matched donor CD8+ T cells were injected into OCS tumour bearing mice (n = 3). Consistent with the immunologically “cold” nature of the OCS, we observed no tumour regression following CD8+ T cell injections. Importantly, all mice treated remained healthy up to 35 days with no recorded immune toxicities and weight loss.

In summary, the immunologically “cold” OCS PDX model established in NSG MHCnull mouse model recapitulate the tumour biology and tolerate human immune cells injection. We plan to utilise the mutant neoantigen identified for this tumour to engineer TCR-T for personalised cell-based therapy, which can then be tested in this pre-clinical PDX model.

  1. Rauh-Hain, J.A., Birrer, M. & Del Carmen, M.G. "Carcinosarcoma of the ovary, fallopian tube, and peritoneum: Prognostic factors and treatment modalities". Gynecol Oncol 142, 248-254 (2016).
  2. Wu et al. T-Cell Receptor Therapy in the Treatment of Ovarian Cancer: A Mini Review. Front. Immunol., 13 April 2021 | https://doi.org/10.3389/fimmu.2021.672502.
  3. Brehm, M.A., et al. Lack of acute xenogeneic graft- versus-host disease, but retention of T-cell function following engraftment of human peripheral blood mononuclear cells in NSG mice deficient in MHC class I and II expression. FASEB J 33, 3137-3151 (2019).