PDF - 569KB, Figure S1: Chemical structures of the compounds applied in this study. Figure S2: Results of the internalization studies of 177Lu-EC0800 performed with FR-positive and FR-negative tumor cell lines Figure S3: Results of a clonogenic assay performed with 177Lu-EC0800 with/without co-application of folic acid using KB and IGROV-1 tumor cells Figure S4: Representation of the area under the curve (AUC) necessary to determine the absorbed dose to the tumors and kidneys. Figure S5: Results of the biodistribution data obtained in KB tumor bearing nude mice injected with 3H-pemetrexed Figure S6: Graphs representing the body weight and survival of mice treated with pemetrexed compared to untreated control mice. Figure S7: Distribution of the cell fractions in a particular cell cycle phase after treatment with 177Lu-EC0800, PMX or both of these agents. Figure S8: Graphs representing the apoptotic fraction of KB and IGROV-1 cells after treatment with 177Lu-EC0800, PMX or both of these agents.
ARTICLE ABSTRACT
Targeted radionuclide therapy has shown impressive results for the palliative treatment of several types of cancer diseases. The folate receptor has been identified as specifically associated with a variety of frequent tumor types. Therefore, it is an attractive target for the development of new radionuclide therapies using folate-based radioconjugates. Previously, we found that pemetrexed (PMX) has a favorable effect in reducing undesired renal uptake of radiofolates. Moreover, PMX also acts as a chemotherapeutic and radiosensitizing agent on tumors. Thus, the aim of our study was to investigate the combined application of PMX and the therapeutic radiofolate 177Lu-EC0800. Determination of the combination index (CI) revealed a synergistic inhibitory effect of 177Lu-EC0800 and PMX on the viability of folate receptor–positive cervical (KB) and ovarian (IGROV-1) cancer cells in vitro (CI < 0.8). In an in vivo study, tumor-bearing mice were treated with 177Lu-EC0800 (20 MBq) and a subtherapeutic (0.4 mg) or therapeutic amount (1.6 mg) of PMX. Application of 177Lu-EC0800 with PMXther resulted in a two- to four-fold enhanced tumor growth delay and a prolonged survival of KB and IGROV-1 tumor-bearing mice, as compared to the combination with PMXsubther or untreated control mice. PMXsubther protected the kidneys from undesired side effects of 177Lu-EC0800 (20 MBq) by reducing the absorbed radiation dose. Intact kidney function was shown by determination of plasma parameters and quantitative single-photon emission computed tomography using 99mTc-DMSA. Our results confirmed the anticipated dual role of PMX. Its unique features resulted in an improved antitumor effect of folate-based radionuclide therapy and prevented undesired radio-nephrotoxicity. Mol Cancer Ther; 12(11); 2436–45. ©2013 AACR.
