| OBJECTIVE:To determine the heating ability of magnetic fluid(MF) in an alternating magnetic field(AMF) in vitro and its application to hyperthermia for mouse pancreatic cancer model established by MPC-83 in vivo.METHOD:The MPC-83 cell line established by ourselves was identified through morphological observation,chromosome karyotype analysis,immunofluorescence of chymotrypsin and pan-cytokeratin,as well as tumor formation rate.Different concentration of MF were prepared in virtro,and heated for 30 min in an intermediate frequency AMF.The phagocytosis phenomenon was observed by transmission electron microscopy(TEM).A murine pancreatic cancer cell line(MPC-83) established by ourselves was used to prepare for tumor-bearing animal models. Tumor-bearing mice were divided into four groups which received,respectively,no treatment(control);MF injection alone;AMF irradiation alone;and MF injection and hyperthermia generated by applying an AMF(300 kHz,110 Gs) to the subaxillary region.The hyperthermia group had 2 subgroups;the central temperature of their tumors reached 47℃and 51℃,respectively,for about 30 min.MF was injected into the subcutaneous nodules 10 days after tumor transplantation and the distribution of magnetic nanoparticles pre- and post-MF hyperthermia were assessed through X-ray. In groupⅣ,24 h after MF was directly injected into their tumors,a magnetic induction apparatus was used to apply an intermediate-frequency magnetic field to the subaxillary region.The therapeutic effect was evaluated in terms of tumor volume changes,survival times and pathological examinations.RESULT:MPC-83 grows adhering to the bottom of its vessel,and displays as an irregular form through inverted microscope observation.The microvilli from cell surface convex to cavity with large nuclear and abundant ribosomes under TEM. Giemsa staining showed MPC-83 had a mouse karyotype with 30-34 pairs of chromosomes,including 20%abnormal submedian centromeres.Immunofluorescence staining of pan-cytokeratin and chymotrypsin showed positive expression.Tumor formation rate of MPC-83 is 100%.The temperature of MF rised rapidly in the AMF. The increase of the temperature was positively correlated to the concentration of MF (n=5,r=0.937,P=0.019).TEM(×120000) showed that the magnetic nanoparticles were phagocytosed by the MPC-83 cells.In vivo experiment the temperature at the tumors' centers reached approximately 47℃or 51℃rapidly,and was kept at the same temperature by varying the current intensity in magnetic field.In contrast,rectal temperatures remained below 36℃.Tumor growth was inhibited and survival significantly prolonged in the hyperthermia group compared with other groups (P＜0.05).X-ray examination showed that the distribution of magnetic nanoparticles in nodules is homogeneous 24 h after MF injection;and 14 days after hyperthermia, there are no subcutaneous nodules with only the MF remains.Tumor cells near the MF in the hyperthermia group apoptosed or necrosed immediately after hyperthermia. By day 14,there were no subcutaneous nodules;and residual magnetic nanoparticles were ingested by phagocytes.Nuclear proliferating cell nuclear antigen(PCNA) decreased in hyperthermia group tumor cells compared to the other groups;and cytoplasmic heat shock protein 70(HSP 70) was conspicuously higher immediately after hyperthermia(P＜0.05).CONCLUSION:MPC-83 is characterized as an epithelial line originating from a mouse pancreatic acinus.MF used for tumor therapy has a good heating ability in an AMF in vitro and its temperature can be controlled by changing the concentration of the MF.Magnetic nanoparticles can be simultaneously phagocytosed by MPC-83 cells.MF hyperthermia using magnetic nanoparticles might be safely applied in the treatment of pancreatic cancer and that therapeutic temperatures can be achieved efficiently through this novel technique.Magnetic fluid hyperthermia(MFH) can inhibit the growth of mouse pancreatic cancer and prolong the survival time of the mice,which had a good therapeutic efficacy.
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