The use of whole body irradiation to reduce tumour development in a mouse model of prostate cancer lawrence

The use of whole body irradiation to reduce tumour development in a

mouse model of prostate cancer

Mark Lawrence

Supervisors: Assoc. Prof. Pamela Sykes and Dr Rebecca Ormsby

The radiation adaptive response

“…a conditioning radiation dose lowers the biological effect of a subsequent (usually higher) radiation exposure.” BEIR VII (2006).

• (in vitro) i.e. cell death, DNA repair, mutation induction, chromosomal aberrations.

• (in vivo) i.e. immune function, survival, cancer latency and frequency.

Low dose radiation increases latency of radiation-induced lymphoma in mice

R.E.J. MITCHEL, J.S. JACKSON, D.P. MORRISON and S.M. CARLISLE “Low doses of radiation increase the latency of spontaneous lymphomas and spinal osteosarcomas in cancer-prone, radiation-sensitive Trp53 heterozygous mice” Radiation Research. 159 320 (2003).

• Dose, dose-rate, and timing of irradiation.

• Haematological cancer studied, almost exclusively.

Prostate cancer• Most common cancer in Australian men (>29% of all

diagnoses).

• High incidence in Western countries versus Asian countries.

• Dietary and environmental factors.

• Familial, early onset, prostate cancer is infrequent (<10% cases).

• Age is most significant predictor of prostate cancer.

Australian Institute of Health and Welfare: http://www.aihw.gov.au/cancer

The TRAMP mouse• Transgenic Adenocarcinoma of the Mouse Prostate.

• 100% of mice will get prostate cancer.

• Disease progression is reproducible.

• Model mirrors disease in humans.PIN (prostatic intraepithelial neoplasia)well moderately poorly differentiated adenocarcinomas.

• TRAMP tumours transiently regress following androgen withdrawal, but recur as androgen-independent prostate cancer (as observed in man).

Experiments

High dose

Adaptive response

Castration

Low dose

Determine high dose inducing and promoting potential; in this model.

Traditional experimental approach.

Test low dose radiation tumour suppressing effect.

Investigate phenomenon in conjunction with standard therapy.

Endpoints

• Prostate/GUT weight and volume.• Time to palpable tumour.

• Histopathological grade.

• Cell proliferation.• Programmed cell death (apoptosis).• DNA damage and repair.

Immunofluorescence for Ki-67

Automated Image Analysis

Immunofluorescence

γH2AX Large T-antigen

The mouse genitourinary tract

Light microscopy of whole mouse prostate sections

Figure: Mean proliferation frequency (±SE) in prostate lobes of 50 mGy and sham treated TRAMP mice, 3 days following treatment. n=10/group

Proliferation pilot study on archival TRAMP prostate tissue

•TRAMP mice treated with 50 mGy or sham and tissues taken 3 days following irradiation.

• Proliferation rates are lobe specific.

• Micro-dissection of prostate is vital.

• Significant effect observed in ventral prostate lobes.

- repeat experiment with micro-dissection and increased animal numbers required.

• Pilot study determined how many cells/images are required for analysis.

– optimised image analysis method.

*

High dose experiment

6 weeks

Remove prostate (and other tissues)

Mice 6 weeks old(carcinogenic process beginning)

2 Gy or Sham irradiated

Little is known regarding:

• radiation-induced prostate cancer

• radiation sensitivity of the TRAMP mouse

Figure: Prostate weight as a per cent of body weight in sham- and 2 Gy-irradiated TRAMP mice. P=0.05 Independent Samples T-test. n=10-11/group

Prostate weight increase following 2 Gy whole body irradiation of TRAMP mice

Dorso-lateral prostate proliferation six weeks following 2 Gy irradiation

N=10-11/treatment group

Prol

ifera

tion

inde

x (+

/-SE

)

• Still to analyse other lobes and histopathology.

• Further high dose experiments with >6 weeks between irradiation and tissue collection.

Summary• Radiation adaptive response.

– Can modulate a range of biological processes (including cancer)

• Expand investigation of adaptive response to an epithelial cancer.

– Prostate cancer

• Explore a range of dose and timing parameters.

• Through investigation of radiation adaptive response:

– Increased knowledge of fundamental processes in prostate cancer.

– New treatment strategies.

Acknowledgments SupervisorsA/Prof Pamela SykesDr Rebecca Ormsby

DOE labDr Benjamin Blyth Alex StaudacherMichelle NewmanAmi-Louise CochraneMonica DreimanisKatrina Bexis

Low Dose Radiation Research Program, Biological andEnvironmental Research, US Department of Energy Grant DE-FG02-05ER64104 and The Cancer Council of South Australia.

Royal Adelaide Hospital A/Prof Eva Bezak

Dame Roma Mitchell Cancer

Research LaboratoriesProf. Wayne Tilley

Dr Lisa Butler