The biochemical approach to cancer therapy: a short essay

Specific intensity imaging for glioblastoma and neural cell cultures with 5-aminolevulinic acid-derived protoporphyrin IX

The fluorescence of protophorphyrin IX (PpIX) synthesized after incubation with 5-aminolevulinic acid (5-Ala) is used for the intraoperative visualisation of glioma cells in vivo. Such fluorescence may also be useful for the photodynamic therapy (PTD) of gliomas. A significant difference of fluorescence intensity in tumor cells compared to neurons is required for this application. To explore this, eight human glioma cell lines (LN-18, LN-428, U87MG, U373MG, D247MG, U251MG, LN-308, T98G) were compared with human astrocytes (SV-FHAS) and rat neurons after incubation for different periods of time in vitro with 5-Ala (1 mg/ml). Fluorescence intensity profiles were measured by a digital camera comparing glioma cell lines with control cells. All glioma cell lines could be discriminated from neural cells by their intensity of fluorescence by post-hoc tests for pairwise comparisons using Tukey's honestly significant difference test, at the global significance level of 5%. The glioma cell lines showed significant variation in this possibly limiting clinical use of fluorescence as a guide for resection.

Kidney-preserving tumour resection in renal cell carcinoma with photodynamic detection by 5-aminolaevulinic acid: preclinical and preliminary clinical results

OBJECTIVE

To identify the outer border of a renal cell carcinoma (RCC) during a kidney-preserving tumour resection by photodynamically detecting RCC after the exogenous administration of 5-aminolaevulinic acid (ALA) in an animal model and in humans.

PATIENTS, MATERIALS AND METHODS

Human RCC was xenotransplanted subcutaneously and orthotopically into the kidneys of nude mice. ALA was then administered orally or intravenously (100-400 mg/kg body weight). The tumours were removed and examined macroscopically and microscopically for fluorescence, and the concentrations of protoporphyrin IX (PPIX) evaluated in the subcutaneous tumours. In a pilot study, nine patients with RCC of <4 cm diameter underwent partial nephrectomy; 20 mg ALA/kg body weight was given orally 4 h before surgery. During the operation, the macroscopic fluorescence of the tumours was evaluated and any side-effects recorded.

RESULTS

In the mouse model, the RCC fluoresced in all tumours, both macro- and microscopically, reaching a maximum 1.5 h after intravenous and 4 h after oral administration. The tissue concentrations of PPIX in the subcutaneous tumours were also maximal 4 h after oral administration. In the patients undergoing surgery, the RCC also fluoresced clearly and was sufficiently intense to identify the outer margins of the tumours for kidney-preserving tumour resection. There were no side-effects of the ALA with the dosages and methods of administration used.

CONCLUSION

The photodynamic detection of RCC with ALA facilitates the identification of tumour margins in man and in the mouse model, producing no undesirable side-effects. It may be helpful in determining the boundaries of the resected tissue when carrying out conservative kidney-preserving surgery.

Adjuvant intraoperative photodynamic therapy diminishes the rate of local recurrence in a rat mammary tumour model

The use of photodynamic therapy (PDT) as an adjunct to curative tumour resection was investigated in a tumour recurrence model, using rat mammary adenocarcinoma BN472. Tumours were inoculated subcutaneously in 60 animals and resected after 21 days of growth. Immediately after removal, the operation site was exposed to 320-450 nm light of 0.1 W cm-2 and 60 J cm-2 after photosensitisation with either Photofrin (5 mg kg-1 i.v. 48 h before illumination) or 5-aminolaevulinic acid (ALA) (2 mg ml-1 in drinking water for 9 days). Porphyrin concentrations were measured in tissue samples. After 28 days, animals treated with adjunctive PDT had a significantly longer tumour-free interval than controls (P < 0.01); median 25 days (Photofrin), 18 days (ALA), 14 days (controls). Moreover, in the PDT groups significantly fewer rats had lymph node metastasis. A prophyrin concentration ratio between tumour and mammary tissue of 2:1 was found after Photofrin and 4:1 after ALA. The results indicate that adjuvant intraoperative PDT may be a safe and effective method of destroying residual tumour, thereby preventing locoregional tumour recurrence.