Objective To establish an appropriate animal model of brain metastases from lung cancer in nude mice by thoracic orthotopic implantation in the chest or left ventricular injection , and to serve further studies on the mechanisms of lung cancer brain metastasis .Methods PC-9 cells (1 ×106/0.1 mL) in logarithmic phase were respectively injected into 18 nude mice by orthotopic implantation in the chest or left ventricular injection ( n=9 each group ) .The statuses of nude mice were observed after implantation .Animals showing clear signs of dyscrasia were killed .At autopsy, the lung, brain, liver and kidney were removed and histological sections were stained with H /E to detect the presence of tumor cells . Results In the thoracic orthotopic implantation group , three weeks after implantation , the number 4, 6, 9 mice showed tumor nodules in the chest wall , they began to lose weight in the fourth to sixth week differently , showing signs of dyscrasia gradually , and were sacrificed at the fifth to seventh week .The thoracotomy revealed that the whole thorax was occupied by many large lung cancer masses , spreading into bilateral ribs , pleura and spinal vertebra , with scarce eroded , compressed , pale and distorted lung tissues left .Histological examination with HE staining showed the presence of neoplasms in their lung tissues but only the number 6 mouse showed metastatic lesions in the brain tissue .In the left ventricular injection group, the mice almost began to lose weight in the third week simultaneously and became moribund slowly , which were all sacrificed at the fourth week .After thoracotomy , the thoraxes were clear except the number 11 and 18 mice which appeared 2-3 tiny tumor foci in the chest wall , with normal lung tissues .Histological examination with HE staining showed the pres-ence of brain metastases in all the nine mice .The rate of brain metastases from lung cancer in the left ventricular injection group was 100%, compared with 11.1% in the thoracic orthotopic implantation group .Conclusions The establishment method of mouse model by left ventricular injection shows significantly higher rate of lung cancer brain metastases than that by thoracic orthotopic implantation .

Objective To establish a mouse model of lung adenocarcinoma brain metastasis with human luc+-PC?9 cells stably expressing luciferase and to compare the evaluation values of bioluminescence imaging and18 F?FDG ( 18 F?flu?orodeoxyglucose) SPECT/CT in these models. Methods Suspension of luc+?PC?9 cells was injected into the left ventri?cle of BALB/c nude mice to establish a mouse model of brain metastasis from lung cancer. Bioluminescence imaging and18 F?FDG SPECT/CT were used to evaluate the metastasis of tumors as compared with HE?staining pathology as a golden standard. Results The success rate of brain metastases was 85% through injecting luc+?PC?9 cells into the left ventricle. The number of tumor cells was positively related to the intensity of light, with a linear correlation (R2 =0. 96). Fluores?cence was observed in the brain, spine and femur by bioluminescence imaging, and the metastases were confirmed by H&E pathological examination. 18 F?FDG SPECT/CT observed abnormal density collective foci in the spine or femur but not in the brain. Conclusions Injection of tumor cell suspension into the mouse left ventricle is a good method to establish a brain metastasis of lung cancer. Bioluminescence has a higher sensitivity and specificity in detecting brain metastasis and bone metastasis, with advantages of real?time, dynamical and non?invasive detection of tumor metastasis growth. 18 F?FDG SPECT/CT does not have superiority in detection of brain metastases but is suitable for detecting bone metastasis.

Objective To observe the ultrastructure of blood-brain barrier in the nude mouse model of brain me-tastases from lung cancer by transmission electron microscopy using lanthanum nitrate tracing.Methods PC-9 cells (1 × 106/0.1 mL) in logarithmic phase were respectively injected into six nude mice ( model group) selected from eight nude mice randomly via the left ventricle, the other two mice without any treatment as the control group.The general status of the mice was observed after implantation.In the fourth week all the mice were sacrificed and brain tissue samples were taken and prepared for transmission electron microscopic observation using lanthanum nitrate tracing.besides, the lung and brain were removed and stained with HE to detect the presence of tumor metastasis.Results Mice in the model group began to lose weight almost simultaneously in the third week and became moribund slowly, and were all sacrificed at the fourth week when showing clear signs of cachexia.At autopsy, the thoraxes were clear, with normal lungs.Histology showed evidence of brain metastasis in all the six mice.The electron microscopy showed that lathanum nitrate tracer was escaped from the capillaries and diffusely or sparsely distributed in the brain tissues of the model group mice, however lathanum nitrate tracer was still confined in the capillary lumen in the mice of control group.Conclusions The diffuse lathanum nitrate tracer in the brain parenchymal tissue indicates the impairment of blood-brain barrier in the nude mouse model of lung cancer brain metastasis and the formation of these metastases is accompanied with the destruction of blood brain barrier.