Suppression of tumour growth from transplanted astrocytoma cells transfected with luciferase in mice by bioluminescence mediated, systemic, photodynamic therapy

Background: Grade 4 astrocytomas are usually incurable due to their diffusely infiltrative nature. Photodynamic therapy (PDT) is a promising therapeutic option, but external light delivery is impractical when cancer cells infiltrate unknown areas of normal brain. Hence the search for endogenous sources to generate light at cancer cells. In vitro, astrocytoma cells, transfected with firefly luciferase, can be killed by bioluminescence-mediated PDT (bPDT). This study asks if bPDT can suppress tumour growth In vivo, when all components of treatment are administered systemically. Methods: Transfected astrocytoma cells were injected subcutaneously or intra-cranially in athymic CD1 nu/nu mice. bPDT required ip bolus of mTHPC (photosensitiser) and delivery of the D-luciferin substrate over 7 days via an implanted osmotic pump. Control animals had no treatment, photosensitiser only or D-luciferin only. For subcutaneous tumours, size and BLI (light emitted after D-luciferin bolus) were measured before and every 2 days after PDT. For intracranial tumours, monitoring was weekly BLI. Results: For subcutaneous tumours, there was significant suppression of the tumour growth rate (P<0.05), and absolute tumour size (P<0.01) after bPDT. Proliferation of subcutaneous and intracranial tumours (monitored by BrdU uptake) was significantly reduced in treated mice. (P<0.001) Conclusions: This study reports bPDT suppression of tumour growth from luciferase transfected astrocytoma cells with all components of treatment given systemically, as required for effective management of recurrent astrocytomas in unknown sites. However, research on systemic bPDT is needed to establish whether effects on nontransfected tumours can be achieved without any unacceptable effects on normal tissues.