Small animal imaging modalities to evaluate immune cells dynamics in response to radiotherapy and immunotherapy
PURPOSE: The primary objective in this project is to develop novel PET-imaging procedures to study the dynamics of immune cell infiltration/activation in solid malignancies, and to use these processes to i) predict responses to immunotherapeutic treatments; and ii) study the immunoregulatory potential of imaging guided tumor-targeted radiotherapy.
VALUE for SOCIETY: Currently, there is a pressing need to find alternative treatment strategies to increase response rates of cancer immunotherapies, and to identify biomarkers that may guide patient selection and assist in the evaluation of treatment responses. Radiation therapy has emerged as an appealing partner for cancer immunotherapy, given its dual cytotoxic and immunomodulatory properties. However, additional knowledge on the immunoregulatory potential of radiotherapy is needed to optimize potential synergies and enhance patient benefits. Non-invasive molecular imaging approaches, such as immuno-positron emission tomography (immuno-PET) have the potential to serve as robust biomarker for cancer treatment.
METHODS: For experimentation we will use unilateral and bilateral subcutaneous tumor models, created by injection of transplantable tumor cells in the rear flanks of syngeneic mice. Bilateral tumors are very relevant in this project, as we aim for studying abscopal (remote) effects of radiotherapy. Individual tumors in animals will be precisely exposed to different radiation regimens. The resulting local and distant immune responses will be studied by PET-imaging and by flow-cytometry over 2 weeks after radiation treatment. To ensure accurate delivery of radiation to tumors, radiation experiments will be conducted under the assistance of radiation physicists specialists. In parallel experiments, immune responses will be also studied in animals treated by immunotherapy, alone or in combination with radiation.
PAIN & DISCOMFORT: The tumor models that we will use are considered to cause minor discomfort/pain into animals. Animals are not expected to suffer during or after the radiation treatment protocols, nor by the different imaging methods. In addition, animals will be sedated, kept warm and closely monitored for vital parameters during imaging and treatment procedures. Animals will be humanely euthanized at the end of the protocol. Radiation regimen protocols, MR/CT/PET/BLI imaging protocols and tumor models are currently being standardized under the approved FOTS (ID# 18956).
NUMBER of ANIMALS: The full project contemplates the use of 10 different immune-PET radiotracers to target different immune cell subtypes. Hence, we are applying for using a total of 1.696 mice. New radiotracers will be validated first in pilot experiments and data for analysis will be collected in large experiments. To increase the robustness and reproducibility of results, identical experiments will be reproduced in two different tumor models comprising two different mouse strains (C57Bl/6 and BALB/c).
ETHICS: The techniques applied here contribute to the 3R’s for optimal animal welfare: 1) REDUCTION: preclinical imaging allows serial non-invasive examination and multiple data collection of individual animals. 2) REFINEMENT: Before main experiments, pilot studies will be carried out with small number of animals to test bio-distribution, clearance, and performance of PET radiotracers and to monitor potential toxicities. 3) REPLACEMENT: the use of tumor-bearing animals is unavoidable to study imaging and to investigate effects from radiation therapy, because biodistribution of radiotracers and analysis of immune activation cannot be carried out otherwise, like in vitro or with phantoms.
VALUE for SOCIETY: Currently, there is a pressing need to find alternative treatment strategies to increase response rates of cancer immunotherapies, and to identify biomarkers that may guide patient selection and assist in the evaluation of treatment responses. Radiation therapy has emerged as an appealing partner for cancer immunotherapy, given its dual cytotoxic and immunomodulatory properties. However, additional knowledge on the immunoregulatory potential of radiotherapy is needed to optimize potential synergies and enhance patient benefits. Non-invasive molecular imaging approaches, such as immuno-positron emission tomography (immuno-PET) have the potential to serve as robust biomarker for cancer treatment.
METHODS: For experimentation we will use unilateral and bilateral subcutaneous tumor models, created by injection of transplantable tumor cells in the rear flanks of syngeneic mice. Bilateral tumors are very relevant in this project, as we aim for studying abscopal (remote) effects of radiotherapy. Individual tumors in animals will be precisely exposed to different radiation regimens. The resulting local and distant immune responses will be studied by PET-imaging and by flow-cytometry over 2 weeks after radiation treatment. To ensure accurate delivery of radiation to tumors, radiation experiments will be conducted under the assistance of radiation physicists specialists. In parallel experiments, immune responses will be also studied in animals treated by immunotherapy, alone or in combination with radiation.
PAIN & DISCOMFORT: The tumor models that we will use are considered to cause minor discomfort/pain into animals. Animals are not expected to suffer during or after the radiation treatment protocols, nor by the different imaging methods. In addition, animals will be sedated, kept warm and closely monitored for vital parameters during imaging and treatment procedures. Animals will be humanely euthanized at the end of the protocol. Radiation regimen protocols, MR/CT/PET/BLI imaging protocols and tumor models are currently being standardized under the approved FOTS (ID# 18956).
NUMBER of ANIMALS: The full project contemplates the use of 10 different immune-PET radiotracers to target different immune cell subtypes. Hence, we are applying for using a total of 1.696 mice. New radiotracers will be validated first in pilot experiments and data for analysis will be collected in large experiments. To increase the robustness and reproducibility of results, identical experiments will be reproduced in two different tumor models comprising two different mouse strains (C57Bl/6 and BALB/c).
ETHICS: The techniques applied here contribute to the 3R’s for optimal animal welfare: 1) REDUCTION: preclinical imaging allows serial non-invasive examination and multiple data collection of individual animals. 2) REFINEMENT: Before main experiments, pilot studies will be carried out with small number of animals to test bio-distribution, clearance, and performance of PET radiotracers and to monitor potential toxicities. 3) REPLACEMENT: the use of tumor-bearing animals is unavoidable to study imaging and to investigate effects from radiation therapy, because biodistribution of radiotracers and analysis of immune activation cannot be carried out otherwise, like in vitro or with phantoms.