A NOD/SCID Model of Primary Human Breast Cancer

Abstract

Background: Breast cancer kills about 400 000 people annually worldwide. Whilst the conventional therapy of surgery, radiation, chemotherapy and hormone therapy has increased survival rates dramatically, the relapse rate is intol- erably high. New therapies, particularly immunotherapies, required to combat this residual disease would ideally be tested on an animal model. Current animal models of human breast cancer available for testing new therapies are unreliable. We therefore sought to develop a protocol that will enable the reliable and reproducible production of a xenograft murine model of human breast cancer. Methods: Female NOD/SCID mice, under specific pathogen-free conditions, were inoculated subcutaneously in the ingui- nal mammary fat pad area with either dissociated primary breast tumours or the breast cancer cell line MCF7. Variables tested included irradiation of mice prior to inoculation, differing tumour cell numbers and the use of the commercial basement membrane Matrigel. Results: 100% engraftment and growth of both MCF7 cells and dissociated primary breast tumour cells, coinoculated with Matrigel, was achieved regardless of whether the mouse was irradiated or not, however larger tumour volume was achieved in the non-irradiated mice. The largest inoculum, 5 x 10 6 cells of MCF7 cells, gave the largest tumours after 3 months in situ (p=0.006). The number of cells injected from primary tumours did not correlate with final tumour size. Both MCF7 and primary human breast tumours exhibited the layered nature of breast tumours, with living cells on the pe- riphery and necrotic cells in the interior. MCF7 cells that engrafted maintained their ER+, CD24+, CD44+ BC2+ (MUC1+) status after in vivo growth. All tumours became vascularised but no metastasis was evident. Conclusions: This is a simple and reliable protocol that ensures human breast tumour growth in the NOD/SCID mouse. This model is valid, in that the tumours are orthotopic, they have the layered nature of human breast tumours, become vascularised and maintained the surface and nuclear marker status tested for. It has potential as a valid human breast can- cer test bed for preclinical testing of immunotherapies and anti-angiogenesis agents.