PET Imaging of tumor hypoxia with Cu-64 radiopharmaceuticals: a pilot study
1 Purpose
Tumor hypoxia (oxygen deficiency) is a common adverse tumor microenvironment in solid tumors. It is a key indicator for cancer progression and poor prognosis, and a key contributor for chemo- and radiotherapy resistance. Currently diagnostic methods of tumor hypoxia are imprecise and immature, if not at all impossible. In this study we will test and compare two Cu-64 based Positron Emission Tomography (PET) tracers (64Cu-Compound A and 64Cu-Compound E) to image tumor hypoxia in human prostate cancer mice xenografts.
Cu-64 has a complex decay scheme, of which low energy, high linear energy transfer (LET) Auger electron emission could be used for therapeutic purposes. Prior studies in mice from the literatures have consistently demonstrated high degrees of tumor volume reduction and significantly prolonged survival after treatment. Combined with PET, Cu-64 based tracers are well suited for simultaneous detection and treatment in solid tumors, effectively "theranostic" tracers, which we have extensively discussed in our recent publication.
The general aim for this experiment is as following:
- To test and analyze the overall bio-distribution of two Cu-64 based PET tracers in mice;
- To test the accumulation of the tracers in tumors and compare with ex vivo oxygenation immunohistochemical measurements;
- To investigate the hypoxia and copper transport signaling pathways and their correlations in human prostate cancer.
2 Distress
This study has minimum distress to the animals.
3 Expected benefit
Development of PET tracers for tumor hypoxia is clinically relevant for both doctors and patients. Detection of hypoxic regions of tumor helps to provide individualized cancer treatments to optimize efficiency and reduce adverse effects [1]. Successful development of a theranostic pharmaceutical may improve overall treatment efficiency and survival among cancer patients.
4 Number and types of animals
In this pilot study we planned to use 25 mice in total. Based on prior studies in literature male BALB/c nude mice will be used [2].
5 How to adhere to 3R
This experiment was designed in compliance with the 3R principle.
Replacement
The two tracer candidates have been extensively studied during our in vitro experiments and in vivo/in vitro studies in literatures. Both Cu-A and Cu-E, for different purposes using natural Cu, have been involved in clinical studies previously. The characteristic and toxicity have been extensively characterized in literatures in vitro. However, the transportation, distribution, dosimetry of the radiotracers are much more complex in vivo than in vitro or while using natural Cu, thus in vivo experiments are needed.
Reduction
The tracers have been extensively tested in vitro and have demostrated promising results (sections below). Only the most necessary experiments will be performed in vivo and only the minimum number of animal to achieve scientific significance will be used.
Refinement
All the animals will be treated with care during the experiment. Upon injection of tracers and during experiment, the animals will be under general anesthesia and kept on a heated blanket to maintain their body temperature. Based on similar experiments subcutaneous tumors are expected to cause minimum distress to the animals.
Tumor hypoxia (oxygen deficiency) is a common adverse tumor microenvironment in solid tumors. It is a key indicator for cancer progression and poor prognosis, and a key contributor for chemo- and radiotherapy resistance. Currently diagnostic methods of tumor hypoxia are imprecise and immature, if not at all impossible. In this study we will test and compare two Cu-64 based Positron Emission Tomography (PET) tracers (64Cu-Compound A and 64Cu-Compound E) to image tumor hypoxia in human prostate cancer mice xenografts.
Cu-64 has a complex decay scheme, of which low energy, high linear energy transfer (LET) Auger electron emission could be used for therapeutic purposes. Prior studies in mice from the literatures have consistently demonstrated high degrees of tumor volume reduction and significantly prolonged survival after treatment. Combined with PET, Cu-64 based tracers are well suited for simultaneous detection and treatment in solid tumors, effectively "theranostic" tracers, which we have extensively discussed in our recent publication.
The general aim for this experiment is as following:
- To test and analyze the overall bio-distribution of two Cu-64 based PET tracers in mice;
- To test the accumulation of the tracers in tumors and compare with ex vivo oxygenation immunohistochemical measurements;
- To investigate the hypoxia and copper transport signaling pathways and their correlations in human prostate cancer.
2 Distress
This study has minimum distress to the animals.
3 Expected benefit
Development of PET tracers for tumor hypoxia is clinically relevant for both doctors and patients. Detection of hypoxic regions of tumor helps to provide individualized cancer treatments to optimize efficiency and reduce adverse effects [1]. Successful development of a theranostic pharmaceutical may improve overall treatment efficiency and survival among cancer patients.
4 Number and types of animals
In this pilot study we planned to use 25 mice in total. Based on prior studies in literature male BALB/c nude mice will be used [2].
5 How to adhere to 3R
This experiment was designed in compliance with the 3R principle.
Replacement
The two tracer candidates have been extensively studied during our in vitro experiments and in vivo/in vitro studies in literatures. Both Cu-A and Cu-E, for different purposes using natural Cu, have been involved in clinical studies previously. The characteristic and toxicity have been extensively characterized in literatures in vitro. However, the transportation, distribution, dosimetry of the radiotracers are much more complex in vivo than in vitro or while using natural Cu, thus in vivo experiments are needed.
Reduction
The tracers have been extensively tested in vitro and have demostrated promising results (sections below). Only the most necessary experiments will be performed in vivo and only the minimum number of animal to achieve scientific significance will be used.
Refinement
All the animals will be treated with care during the experiment. Upon injection of tracers and during experiment, the animals will be under general anesthesia and kept on a heated blanket to maintain their body temperature. Based on similar experiments subcutaneous tumors are expected to cause minimum distress to the animals.