Experimental Study Of ～(99)Tc～m-Sandostatin Somatostatin Receptor Imaging In Diagnosis Of Pancreatic Cancer

Part I Expression of somatostatin receptor mRNA in human pancreatic cancer Objective To investigate the expression of somatostatin receptor(SSTR) mRNA inhuman pancreatic cancer. Methods The expression of SSTR subtype 1-5 mRNA were determined by reverse transcription polymerase chain reaction method in 30 cases of pancreatic cancer and in 12 cases of normal pancreas tissues. Results 1. The expression of SSTR1 -5 mRNA in pancreatic cancer were(2.29 0.87), (3.72+1.42), (1.91 0.92), (1.80 0.98) and (2.25 0.92) respectively. The expression of SSTR2 mRNA was significantly higher than the expression of SSTR1 3 4 5mRNA(P<0.01). 2. The expression of SSTR1-5 mRNA in normal pancreas tissues were(1.37 0.74), (1.38 0.98), (1.26 + 0.79), (1.21 0.42) and (1.33 0.92)respectively. There is no significant difference between the expression of SSTR1-5 mRNA(P>0.05). 3.The expression of SSTR1 2 5 mRNA in pancreatic cancer were significantly higher than those in normal pancreas tissues(P<0.04). So did the expression of SSTR3 mRNA(P<0.05). Conclusions The expression of SSTR1 2 3 5mRNA in pancreatic cancer were significantly higher than those in normal pancreas tissues. The expression of SSTR2 mRNA was significantly higher than the expression of SSTR 1 3 4 5mRNA in pancreatic cancer.Part II Study on biodistribution and somatostatin receptor imaging of 99Tcm-Sandostatin in nude mice bearing human pancreatic cancer xenograftObjective To study the biodistribution of 99Tcm-Sandostatin in nude mice bearing human pancreatic cancer xenograft and the imaging efficacy of Tcm-Sandostatin somatostatin receptor imaging for pancreatic cancer. Methods The nude mice bearing human pancreatic cancer xenograft were constructed by injecting BXPC3 pancreatic cancer cell lines subcutaneously on the right back of nude mice. 37MBq 99Tcm-Sandostatin wasinjected into the tumor-bearing nude mice via the tail vein and somatostatin receptor imaging(SRI) was performed 2,4 and 6h postinjection. The images were processed by region of interest(ROI) method to acquire the counts ratios of tumor to contralateral normal tissue. The mice were killed after 6h postinjection imaging and tissue distribution was measured. Cpm/g and tumor to normal tissue(TTNT) ratios were calculated. Results SRI showed that the tumor was visualized 2h postinjection and the radioactivity in tumor reached its peak between 4h ~ 6h postinjection. At the peak time of accumulation the tumor could be viewed clearly and the best image displayed. The tumor which diameter was only 0.52cm could also be imaged clearly. The T/NT ratios was increased with time. Biodistribution results showed that the radioactivity counts in tumor were significantly higher than those in normal tissues except for the kidney. T/NT ratios for muscle, blood, stomach, spleen, heart, lung and liver were 7.59, 5.39, 3.91, 3.21, 2.96, 2.57 and 1.17, respectively. Conclusions 99Tcm-Sandostatin somatostatin receptor imaging is a promising noninvasive method for pancreatic cancer. It is readily available, safe, economical and effective. It possesses high sensitivity and high specificity to screen out pancreatic cancer. This method has potential value for clinical diagnosis of early stage. 99Tcm-Sandostatin is a promising radiopharmaceutical for somatostatin receptor imaging of pancreatic cancer.