Positron emission tomography computed tomography in oncology

Synthesis and evaluation of a 68Ga-labeled bradykinin B1 receptor agonist for imaging with positron emission tomography

A novel ⁶⁸Ga-labeled bradykinin B1 receptor (B1R) agonist, ⁶⁸Ga-Z01115, was synthesized and evaluated for imaging with positron emission tomography (PET). Z01115 exhibited good binding affinity (K_i=25.4±5.1nM) to hB1R. ⁶⁸Ga-Z01115 was prepared in 74±5 decay-corrected radiochemical yield with >99% radiochemical purity and 155±89GBq/µmol (4.2±2.4Ci/μmol) specific activity. ⁶⁸Ga-Z01115 was stable in vitro in mouse plasma (93% remaining intact after 60min incubation), and relatively stable in vivo (51±5% remaining intact at 5min post-injection). PET imaging and biodistribution studies in mice showed that ⁶⁸Ga-Z01115 cleared rapidly from nontarget tissues/organs, and generated high target-to-nontarget contrast images. The uptake of ⁶⁸Ga-Z01115 in B1R-positive (B1R+) tumor was 5.65±0.59%ID/g at 1h post-injection. Average contrast ratios of B1R+ tumor-to-B1R- tumor, -to-blood and -to-muscle were 24.3, 24.4 and 82.9, respectively. Uptake of ⁶⁸Ga-Z01115 in B1R+ tumors was reduced by ∼90% with co-injection of cold standard, confirming it was mediated by B1R. Our data suggest that ⁶⁸Ga-Z01115 is a promising tracer for imaging the expression of B1R that is overexpressed in a variety of cancers.

Differential phosphofructokinase-1 isoenzyme patterns associated with glycolytic efficiency in human breast cancer and paracancer tissues

Cancers are characterized by an increasing glycolytic activity, which is called the Warburg effect. Although this phenomenon is well known, the mechanism of the enhanced rate of glycolysis in cancer has not yet been clearly recognized. The present study investigated the glycolytic rate, regulatory enzymatic activities and the expression of phosphofructokinase-1 (PFK-1) in human breast cancer and paracancer tissues. Human breast cancer tissues have an increased degree of glycolytic efficiency and regulatory enzymatic activities, which have been shown in previous studies. However, the present study identified a number of novel observations. The total PFK-1 levels were higher in human breast cancer tissues than in paracancer tissues, and further investigations revealed differential PFK-1 isoenzyme expression patterns between human breast cancer and paracancer tissues. The human breast cancer and paracancer tissues mainly expressed PFK-P and PFK-L isoforms, respectively. Linear-regression analysis showed that, depending on the pathological stage of breast cancer, the expression of PFK-P was significantly positively correlated with the activity of PFK-1. Thus, during the development of human breast cancer, the enhancement of glycolytic activity depends primarily on the conversion of the PFK-1, from PFK-L to PFK-P.