Animal Experimental And Clinical Study On Multiple Tracers PET/CT In Glioma

Objective In recent years, accumulated evidences have shown that the generation of glioma involve pathologic and molecular biology processes such as cell cycle, development and differentiation, signal transduction, apoptosis and cellular metabolism and so on. So it is a critical challenge to make an exact evaluation of biological behaviors in glioma for imaging. PET, as a non-invasive molecular imaging technology, is becoming an increasingly important tool for the measurement of physiological, biochemical, and pharmacological function an the molecular level or gene level. There are three parts in this study. The objective of PartⅠis①to compare the value of 18F-FDQ 11C-MET and 11C-CHO PET/CT for differentiating tumors from acute or chronic inflammatory and granuloma in experiment rat models;②to investigate the relationship of FDG, MET, CHO uptake with HIF-1α, GLUT-1, CD98, VEGF, MVD and Ki67 in C6 glioma. In partⅡ, the objective is to assess the metabolic activity of human gliomas using FDG, MET, CHO PET/CT and to explore the correlation between the metabolic activity and histopathologic features. In partⅢ, the objective is①to assess the metabolic activity of C6 glioma before and after treatment with aspirin using 11C-PD153035 PET/CT;②to explore the correlation between the PD153035 uptake with EGFR, Ki67, MMP-2 and MMP-9.Materials and Methods PartⅠ:①52 male SD rats were randomly divided into 7 groups:group A or B consisted of 8 rats bearing both C6 glioma and turpentine oil-induce acute inflammation; group C or D consisted of 8 rats bearing both C6 glioma and turpentine oil-induce chronic inflammation; group E or F consisted of 8 rats bearing both C6 glioma and BCG-induced granuloma; group G as a control group consisted 4 blank rats.②FDG and MET PET/CT were performed on group A, C and E; FDG and CHO PET/CT were performed on group B, D and F; 3 tracers of PET/CT were performed on group G. After that, the lesions were excised. Immunohistochemical stain and western blot methods were used to demonstrate the situation of GLUT1, CD98, HIF-1αand VEGF expression and quantitatively measure the MVD and Ki67.③The lesion-to-muscle(L/M) ratios and the tumor selectivity index were calculated.σA one-way ANOVA, a unpaired t test and a multiple regression and correlation were used to make statistical analyses. PartⅡ:①All consecutive 159 patients with suspected primary glioma underwent PET scanning in our center. PET examination were performed on 131 patients with FDG, on 95 patients with MET, on 44 patients with both CHO and FDG, on 87 patients with both MET and FDG. and on 8 patients with three tracers. MRI was performed within 2 weeks before PET examination. Pathologic diagnosis was obtained by biopsy or open surgery in all patients with tumors. The lesions included 108 gliomas(3 WHOⅠtumors,42Ⅱtumors,42Ⅲtumors and 21Ⅳtumors),18 other tumors and 33 non-neoplasm lesions.②PET imaging were analysed in visual and semi-quantitative approaches. The SUVmax and L/WM were calculated. To analyze the relations among the tracer uptake, tumor grade, tumor type, tumor Gd-DTPA enhancement and tumor proliferation activity (Ki67) using ANCOVAs, one-way ANOVA, ROC curve and Spearman's test. PartⅢ:①18 SD rats bearing C6 glioma were randomly divided into 3 groups(6 in each group):group 1 was treated with ASA into C6 glioma; group 2 was treated with acetone; group 3 was control group. All received 11C-PD153035 PET/CT scanning.②Immunohistochemical stain and western blot methods were used to demonstrate the situation of EGFR, MMP-2 and MMP-9 expression and quantitatively measure the Ki67.③To analyze the significance of differences and correlations of the PD153035 uptake, EGFR, MMP-2, MMP-9 and Ki67 among 3 groups using one-way ANOVA, nonparametric Kruskal-Wallis H test and Peasrson's test.Results PartⅠ:①The FDG uptake from high to low level in different lesions is:C6 glioma>acute inflammation>chronic inflammation>granuloma. And the differences between C6 glioma and acute inflammation, C6 glioma and chronic inflammation, and C6 glioma and granuloma were significant.②The MET uptake from high to low level in different lesions is:C6 glioma>chronic inflammation>acute inflammation>granuloma. And the differences between C6 glioma and acute inflammation, C6 glioma and chronic inflammation, and C6 glioma and granuloma were also significant. And the SIMET is significantly higher than SIFDG.③The CHO uptake from high to low level in different lesions is: acute inflammation>granuloma>C6 glioma>chronic inflammation. And there were no significant difference between different lesions.④The Tu/Mu_FDG positively correlated with GLUT-1, HIF-1α, VEGF, MVD, Ki67 in order. There were no correlations between Tu/Mu_FDG with size of tumor and cell density.⑤The Tu/Mu_MET positively correlated with CD98, VEGF, MVD, Ki67, HIF-1αin order. There were no correlations between Tu/Mu_MET with size of tumor and cell density.⑥The Tu/Mu_CHO positively correlated with Ki67, MVD, VEGF in order. There were no correlations between Tu/Mu_CHO with size of tumor, cell density and HIF-1α. PartⅡ:①Visual analysis:The diagnostic accuracy of FDG, MET, CHO PET/CT in brain tumor are 71.0%,92.6%, and 61.4%, respectively. The accuracy of combination two tracers PET/CT is no more than that of MET PET/CT alone.②Semi-quantitative analysis:Glioma grade influenced FDG, MET and CHO uptake, and glioma type influenced FDG, MET uptake only. The L/WMFDG and L/WMMET of oligodendroglial tumors was significantly higher than astrocytic tumors. The best ratio to differentiate low- from high-grade tumors is L/WMCHO by ROC, and the cut-off value of L/WMCHO is 5.05.③There were significant differences between high-grade tumors and non-neoplasm lesions for three tracers, but there was difference between low-grade tumors and non-neoplasm lesions only for MET. There were no significant difference of 3 traces uptake among high-grade glioma, brain metastasis and lymphoma, but FDG PET/CT body scan is helpful to identify brain metastasis.④In astrocytic tumors, there were significant correlations between L/WM ratios of each tracer and Ki67 and tumor Gd-DTPA enhancement. However, for oligodendroglial tumors and oligoastrocytic tumors, the significant correlations were not shown in all of the tracers. PartⅢ:①PD153035 PET/CT showed a marked intense PD153035 accumulation in the C6 glioma of group 3, the mean Tu/Mu was 1.39±0.16. After treatment with ASA, the PD153035 uptake was a marked reduction in the group 1, the mean Tu/Mu was 1.04±0.02. There were statistical significance between group 1 and 3, group 1 and group 2, and was no statistical significance between group 2 and 3.②Immunohistochemical study and western blot showed that there were significant differences of the expression of EGFR, MMP-2, MMP-9, Ki67 between group 1 and 3, group 1 and group 2, and no significances of expression of these proteins between group 2 and 3.③There were positive correlations between Tu/Mu_PD 153035 and EGFR, MMP-2, MMP-9 and Ki67(r=0.593,0.468,0.638 and 0.566, respectively P<0.05).Conclusions (1) MET is more tumor selective than FDG and CHO, therefore, MET PET/CT is able to differentiate glioma from non-neoplasm lesions. CHO PET/CT is not able to differentiate glioma from non-neoplasm lesions. (2) Human glioma grade influenced FDG, MET and CHO uptake, and glioma type influenced FDG, MET uptake only. The L/WMFDG and L/WMMET of oligodendroglial tumors was significantly higher than those of astrocytic tumors. The best ratio to differentiate low- from high-grade glioma is L/WMCHO; (3) FDG, MET, CHO PET/CT can give some information of biologic character of C6 glioma, such as the transform of glucose/amino acid, hypoxia, angiogenesis and proliferation. The FDG uptake is influenced by glucose transform, hypoxia, angiogenesis, proliferation, in order; The MET uptake is influenced by amino transform, angiogenesis, proliferation, hypoxia, in order; The CHO uptake is influenced by proliferation, angiogenesis, in order. (4) In astrocytic tumors, the FDG, MET and CHO uptake correlated with Gd-DTPA enhancement and Ki67. The correlations between CHO uptake with Gd-DTPA enhancement and Ki67 were more obvious than uptake of FDG and MET, suggesting that CHO PET could more effectively reflect the integrity of BBB and proliferative activity than FDG, MET PET. However, for oligodendroglial tumors and oligoastrocytic tumors, the significant correlations were not shown in all of the tracers. (5) ASA can significantly downregulate the expression of EGFR of rat C6 glioma in vivo, and the findings may provide a new approach to the EGFR targeted therapy of glioma.(6) There were positive correlations between Tu/Mu_PD153035 and EGFR, Ki67, MMP-2 and MMP-9 in rat C6 glioma, suggesting that PD153035 PET could effectively reflect EGFR expression, proliferative and invasion. PD153035 is a promising tracer of PET for monitoring EGFR targeted therapy in glioma.