Ukrain^®, an alkaloid thiophosphoric acid derivative of Chelidonium majus L. protects human fibroblasts but not human tumour cells in vitro against ionizing radiation

N. CORDES¹, L. PLASSWILM², M. BAMBERG² and H. P. RODEMANN^1*

1) Section of Radiobiology and Molecular Environmental Research, Eberhard-Karls-University Tüebingen, Hoppe-Seyler-Strasse 3, 72076 Tüebingen, Germany.
2) Department of Radiation Oncology, Eberhard-Karls-University Tüebingen, Hoppe-Seyler-Strasse 3, 72076 Tüebingen, Germany.
*Author for correspondence

Abstract. Purpose: Ukrain^®, an alkaloid thiophosphoric acid derivative of Chelidonium majus L., has demonstrated a promising impact on chemotherapy in a variety of malignancies. The effects of the drug on cell survival, alteration of the cell cycle and induction of apoptosis were examined without and in combination with ionizing radiation (IR). The TP53 status of the cell lines used was also investigated. Materials and methods: Exponentially growing human tumour cell lines MDA-MB-231 (breast), PA-TU-8902 (pancreas), CCL-221 (colorectal), U-138MG (glioblastoma), and human skin and lung fibroblastic cells, HSF1, HSF2 and CCD32-LU were studied by colony assay, flow cytometry (cell-cycle, annexin-V staining for apoptosis) and Western blotting. Ukrain was used in concentra­tions from 0.1 to 50 μg ml-1 for 1,3 and 24h and radiation as single doses of l-10Gy. Combined drug-radiation exposure employed 1 μg ml-1 Ukrain for 24 h plus 2-8 Gy. Results: Ukrain cytotoxicity was time- and dose-dependent. The combination of Ukrain plus IR gave enhanced toxicity in CCL-221 and U-138MG cells, but not in MDA-MB-231 and PA-TU-8902 cells. Most strikingly, a radioprotective effect was found in normal human skin and lung fibroblasts. Flow-cytometry analyses supported the differential and cell line-specific cytotox­icity of Ukrain. CCL-221 and U-138MG cells accumulated in G2 after 24-h Ukrain treatment, whereas no alterations were detected in the other tumour cells and normal fibroblasts tested. Western blotting of TP53 demonstrated non-functional over-expression in all tumour cell lines without affecting p21. HSF1 presented wild-type TP53 and a p21 response after IR. Flow-cytometric analyses of annexin-V staining showed no induction of apoptosis after Ukrain treatment in comparison with untreated controls.
Conclusions: Differential effects of Ukrain in modulating radiation toxicity of human cancer cell lines and its protective effect in normal human fibroblasts suggest that this alkaloid may have potential properties for clinical radiochemotherapy.