RESUMEN
Objective To investigate the direct inhibitory effects of 153Sm- DTPA-c (Cys-Gly-Arg-Arg-Ala-Gly-Gly-Ser-Cys) NH2 ( 153 Sm-DTPA-c (CGRRAGGSC)) on human prostate cancer PC-3 cells. Methods 153Sm-DTPA-c(CGRRAGGSC) was synthesized by the reaction of 153SmCl3 with DTPA-c(CGRRAGGSC) using indirect synthesis method. PC-3 cells in vitro culture were divided into four study groups, groug A ( the control, with PBS only), group B with 1.5 mg/L c ( CGRRAGGSC), group C with 370 kBq 153 SmCl3 and group D with 370 kBq 153Sm-DTPA-c(CGRRAGGSC). PC-3 cell growth was assayed by 3-(4, 5-dimethylthiazol-2-yl ) -2, 5-diphenyltetrazolium bromide (MTT) method. Cell cycle and apoptosis were analyzed by flow cytometry. The expression changes of interleukin 11 (IL11 ) and IL11 receptor (IL1 1 R) in PC-3 cells were examined by Western Blot. One way analysis of variance (ANOVA) and paired-t test were applied for statistic analysis. Results The labeling yield of 153Sm-DTPA-c (CGRRAGGSC) was 85% and the radiochemical purity was 95.8%. The specific activity of 153Sm-DTPA-c(CGRRAGGSC) was 1.32 × 105 MBq/μmol. Significant inhibitory effects on the growth of PC-3 cells were found in both group C and D, with a time-dependent manner. However, no obvious inhibition was found either in group A or in group B. After 48 h,significant differences of sub-G1 peak area were found among groups, (0. 98 ± 0. 18)%, (0. 35 ±0. 10)%, (4.05 ±0.28)% and (13.38 ±0. 89)% for group A, B, C and D, respectively. Furthermore,sexpression of ILl 1R in group D was significantly lower than that in group B and C with absorbance values 0. 339 ~ 0.014, 0.338 ~ 0.019, 0.226 ~ 0. 015 for group B, C and D, respectively. Absorbance values in groups B and C were not significantly different after treatment, compared with those before treatment; however, there was difference between absorbance values after and before treatment in group D ( t = 0. 405,1. 163,135.989,P>0.05 >0.05, <0.05). Conchluion 153Sm-DTPA-c(CGRRAGGSC) can directly in hibit the cell growth and expression of human prostate cancer cells PC-3.
RESUMEN
Objective To assess the feasibility of a novel 99Tcm labelled polypeptide analogue for interleukin-11 receptor ( IL11R) imaging in a bone metastases model for prostate cancer. Methods A novel circular polypeptide analogue of IL11 ( c( CGRRAGGSC ) ) was indirectly labeled with 99Tcm and the product was named as 99Tcm-DTPA-IL11 RR. The labeling efficiency, radiochemical purity and stability of the product were measured with paper chromatography and high performance liquid chromatography (HPLC). The biodistribution of 99Tcm-DTPA-IL11RR was investigated in 28 ICR normal mice. The organ radioactivity was measured as percentage activity of injection dose per gram of tissue ( %ID/g). The models of bone metastases from prostate cancer were established at the tibias of BALB/c nude mice bearing human prostate cancer PC-3 cells. The tumor bearing ( n= 5 ) and standard closed fracture nude mice models underwent both 99Tcm-DTPA-IL11RR and 99Tcm-methylene diphosphonate (MDP) scintigraphy study. The images were acquired at 0.5, 1,2, 4, 6, 8, 24 h after intravenous injection of the tracers. The competitive inhibition imaging was perfomed in three tumor bearing mice. One-way variance analysis was used. Results The labeling efficiency was 90.7%. The radiochemical purity of 99Tcm-DTPA-IL11RR in normal saline solution was (99.57 ±0.09)%, (99.29 ±0.18)%, (98.95 ±0.78)%, (98.67 ±0.11)%, (96.53 ±0.91)%, (95.20±0.70)%, (88.38 ±0.22)% and (36.17±1.29)% at room temperature after0, 1,2, 3, 4, 6, 8 and 24 h, respectively. The tracer radiochemical purity in the blood of ICR mice remained over 90% at 37 C for 6 h. The labeling compounds were excreted mainly through kidney. The peak uptake of bone ( ( 1.910 ±0.109) %ID/g) and liver ( (0.366 ±0.030) %ID/g) was at 4 h after injection. In the tumor bearing mice, the uptake of spine marrow and large joints of extremities was mild. The highest uptake at tumor region was at 4 h and persistent at 6-8 h after injection. The tumor to non-tumor ratios (T/NT) were 1.17 ±0.17, 2.20 ±0.29, 3.20 ±0.15, 3.67 ±0.23, 13.61±0.85, 9.45 ±0.37 and 3.33 ±0.30 at 0.5,1, 2, 4, 6, 8 and 24 h, respectively (F=621.54, P＜0.05). In the standard closed fracture models,high uptake of 99Tcm-MDP was shown at the fracture site, with no increased 99Tcm-DTPA-IL11RR uptake noted. The tumor uptake was significantly depressed after a pre-injection of the unlabeled polypeptide analogue. Conclusions The synthesis of 99Tcm-DTPA-IL11RR is stable and the labeling efficiency is high. It may be a potential molecular probe in metastatic bone imaging for prostate cancer.