Ultra-small superparamagnetic iron oxide mediated magnetic hyperthermia in treatment of neck lymph node metastasis in rabbit pyriform sinus VX2 carcinoma.

Lymph node metastasis of rabbit VX2 pyriform sinus carcinoma can be enhanced by MR scanning after injecting ultra-small superparamagnetic iron oxide (USPIO) into the submucosa beside the tumor. The metastasis lymph node which fit in with the diagnostic criteria will be placed into the alternating magnetic field after MR scanning. Then, magnetic particles can be heated to the effective therapeutic temperature. And it evaluates the possibility of diagnosis together with therapy in cervical metastasis of pyriform sinus carcinoma. Twenty rabbits bearing VX2 tumor in pyriform sinuses were randomly divided into hyperthermia group and control group after USPIO MR scanning; each group contained 10 rabbits. The hyperthermia for the experimental group was conducted by the alternating magnetic field. After hyperthermia, the detection of apoptosis for the two groups was tested by terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick end labeling (TUNEL), transmission electron microscopy (TEM), and the expression of Bcl-2 and Bax evaluated by immunohistochemical analysis. The apoptosis rate detected by TUNEL in hyperthermia group was 100 %, while the control group was only 20 % (p < 0.05). TEM observation showed that cell chromatin condensation and clumping, condensed cytoplasm, endoplasmic reticulum membrane fusion with loose change, and the formation of a bubble could be seen in the hyperthermia group. However, the control group showed a more complete cytoplasm and nucleus. Bcl-2 protein expression in the hyperthermia group was lower than the control group, and Bax protein expression in hyperthermia group was higher (p < 0.05). USPIO indirect lymphography could localize the metastatic lymph nodes for hyperthermia. And it could make the metastatic cervical lymph nodes apoptosis when placed into the alternating magnetic field.