Heterodimeric Peptide Probe With High Affinity For Theranostic Targeting Breast Cancer

Project Ⅰ Dual-tracer 68Ga-DOTA-RGD-ATWLPPR in the Diagnosis of Breast CancerPurpose:Both Neuropilin-1(NRP-1)and integrin αvβ3 receptors are expressed in breast cancer.We synthesized a heterodimeric tracer dual peptides that simultaneously target integrin αvβ3 and NRP-1.Then,we investigated the diagnostic efficacy of RGDATWLPPR heterodimeric peptides in MCF-7 xenograft models in mice.Method:The carboxyl group on DOTA and the corresponding free amino group of the fusion peptide RGD-ATWLPPR were reacted and modified.The obtained precursor was further purified and radioactively labeled with 68Ga to determine the radiochemical purity and in vitro stability of the label.Small animal PET/CT imagingwas performed on human breast cancer MCF7 xenografts,and compared with 68GaDOTA-RGD and 68Ga-DOTA-ATWLPPR two single peptide imaging agents in imaging and specificity.After inj ection of 68Ga-DOTA-RGD-ATWLPPR,the biodistribution study was carried out immediately at 5,15,30 and 60 min.Results:68Ga-DOTA-RGD-ATWLPPR was labeled within 25min,the attenuation correction yield was 86.1±4.8%(n=3),and the specific activity was 59.1-73.9 GBq/μmol,which showed high stability in vitro.In the static PET/CT imaging study,MCF7 tumors can be clearly displayed 30min after 68Ga-DOTA-RGD-ATWLPPR injection,and show a higher uptake and drawing sense than 68Ga-DOTA-RGD or 68Ga-DOTAATWLPPR alone.Region of interest(ROI)to quantify the uptake of each group of tumors.The uptake of 68Ga-DOTA-RGD-ATWLPPR(4.94 ± 1.05%ID/g)by MCF7 is higher than 68Ga-DOTA-RGD(3.69±0.72%ID/g,P<0.05)and 68Ga-DOTAATWLPPR(2.59 ± 0.56)%ID/g,P<0.001).It shows that 68Ga-DOTA-RGDATWLPPR has higher targeting affinity.The uptake of 68Ga-DOTA-RGD-ATWLPPR by MCF7 tumors is still high after 60 min,which can clearly reflect the tumor site,and the T/N ratio analysis is performed,which is higher than that of 68Ga-DOTA-RGD and 68Ga-DOTA-ATWLPPR.Uptake at the tumor site after 60 min.The biodistribution showed that the intake of 68Ga-DOTA-RGD-ATWLPPR in most organs tested was the largest at 30 min,and then decreased to 60 min.The 68Ga-DOTA-RGD-ATWLPPR tracer was mainly cleared through renal urine.Conclusion:68Ga-DOTA-RGD-ATWLPPR is a dual receptor targeting tracer ofαvβ3 and VEGFR.Compared with monomer 68Ga-DOTA-RGD and 68Ga-DOTAATWLPPR,it has higher binding affinity and targeting Efficiency and longer tumor retention time.Its good in vivo performance makes it more effective and adequate to distinguish benign and malignant breast tumors.In the future,combined with therapeutic nuclides will provide ideas for breast cancer treatment with multiple targets.Project Ⅱ 177Lu-labeled fusion peptide DOTA-RGD-ATWLPPR radionuclide imaging and treatment researchPurpose:Based on the good biological properties of 68Ga-DOTA-RGDATWLPPR as an imaging agent for breast cancer malignant tumors,we will further study the therapeutic effect of 177Lu-DOTA-RGD-ATWLPPR in preclinical models of breast cancer。Method:Using DOTA-RGD-ATWLPPR as the ligand,selecting an appropriate amount of activity of 177LUCL3 to react under specific pH,reaction time,reaction temperature and other labeling conditions,the labeling rate was measured by a radioactivity detector,and a high-performance liquid chromatograph(HPLC)Deter 分钟 ation of radiochemical purity for quality control testing.In the body distribution study,inject 100ul of 177Lu-DOTA-RGD-ATWLPPR solution(about 3.7MBq)through the tail vein,and take out the heart,liver,spleen,lung,and kidney of each MCF7 tumor-bearing nude mouse 4,12,24,48,72h after injection,small intestine,stomach,bone tissue,muscle and blood,Measure the radioactivity count of each tissue and record the corresponding weight of each tissue.Toxicity experiment study injected 177Lu-DOTA-RGD-ATWLPPR at doses of control group and 29.6MBq group to monitor the activity and body weight of the mice.Four nude mice bearing MCF7 breast cancer were taken and injected with 18.5MBq 177Lu-DOTA-RGD-ATWLPPR via the tail vein.SPECT imaging was performed at 4,12,24,48,72h after injection.Nuclide treatment experiments were injected with different doses of 177Lu-DLTA-RGDATWLPPR through the tail vein.After the treatment started,the tumor size of the monitoring,continuous observation for 16 days.Determine the appropriate therapeutic dose by evaluating the best therapeutic effect.Results:The results of 177Lu-DOTA-RGD-ATWLPPR radionuclide therapy proved that it has an effective inhibitory effect on breast cancer tumors.The high dose group had higher tumor absorption and showed good tumor suppression.The growth inhibitory effect of 177Lu-DOTA-RGD-ATWLPPR can reach 14 days after treatment.The SPECT imaging of 177Lu-DOTA-RGD-ATWLPPR is more consistent with the biodistribution results.Regarding the safety of the 177Lu-DOTA-RGD-ATWLPPR radionuclide therapy,the treatment group did not die of tumor-bearing nude mice within a short period of time after treatment with 7.4MBq,18.5MBq,and 29.6MBq,and the weight recovered to A relatively stable and normal level,the safety of the drug is also confirmed by the hematoxylin-eosin staining experiment of vital organs and tissues.