Hjem
Klinisk institutt 2

Midtveisevaluering - Katrin Kleinmanns

Hovedinnhold

ABSTRAKT

Image-guided surgery and personalised postoperative immunotherapy to improve cancer outcome -

Development of a humanized ovarian cancer PDX mouse model

 

Introduction: High grade serous ovarian cancer (HGSOC) patients are most often diagnosed at an advanced stage with metastatic spread into the abdominal cavity resulting in the most lethal gynecological malignancies in developing countries. Current strategies to overcome the overall poor survival (<45%) are to improve complete debulking surgery, followed by chemotherapy and new innovative treatment options like targeted therapy or immunotherapy. Therefore, the aim of this thesis is to develop an immunocompetent patient derived xenograft (PDX) model for HGSOC where we enhance the engraftment efficacy of patient material, optimize the completeness of resection with fluorescence image-guided surgery (FIGS) followed by immunotherapy. For the latter, the implementation of a human immune system into the murine model is indispensable.

 

Methods: To enhance the engraftment rate in HGSOC PDX models, we dissociated the heterogeneous tumours with eight differential enzymatic cocktails and injected the cell suspension through three different injection routes (intraperitoneally, subcutaneously and orthotopically). Engrafted PDX mice were monitored by fluorescence optical imaging for disease progression. The optimal biomarker was identified by flow cytometry and compared to the bioluminescence imaging approach in xenograft models in vivo. For FIGS, OV90luc+/GFP+ xenograft models underwent surgery after injection of a near infrared conjugated monoclonal antibody and tumour lesions were detected with a real-time based FIGS camera system.

For the implementation of a human immune system, CD34+ cells were isolated from volunteer cord blood donors and injected into immunodeficient mice. Blood was drawn every 4 weeks and the mouse-human chimerism was evaluated. Different mouse strains, genders and precondition parameters were tested and optimized. After 8 weeks OV90luc+/GFP+ cells were injected and tumour infiltration was analysed.

 

Results: The implantation of 44 different patient samples resulted in 9 PDX models. We demonstrated that HGSOC cell lines express high levels of the stem cell marker CD24. The monoclonal antibody CD24 conjugated to AF680 achieved a comparable detection sensitivity to bioluminescence imaging in xenografts and was in addition capable to detect tumour lesions by optical fluorescence imaging in PDX models as well as micrometastasis in the IGS setting. The anti-CD24 FIGS probe enables visualisation of cancer cells in ovaries and the abdomen which appear grossly normal to the naked eye. For the humanization of immunodeficient mice, female preconditioned NSGS mice showed the highest human-mouse chimerism. Further, tumour growth in humanized xenografts were not impeded and tumour infiltrating T cells could be identified.

 

Conclusion & Future Perspective: We demonstrated that the stem cell marker CD24 conjugated to AF680 enables tumour detection and visualisation of metastatic spread in xenograft and PDX models through optical and intra-operative imaging. The humanization of immunodeficient mice allows to investigate cancer immunotherapies and offers a powerful tool to understand the low clinical efficacy of immune checkpoint inhibitors in HGSOC. The combination of improved debulking surgery by fluorescence guidance together with personalised immunotherapy is capable to prolong the lifespan of HGSOC patients.