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Background: Tumour hypoxia is associated with increased metastasis, invasion, poor therapy response and prognosis. Most PET radiotracers developed and used for clinical hypoxia imaging belong to the 2-nitroimidazole family. Recently we have developed novel 2-nitroimidazole-derived PET radiotracer [ 18 F]FBNA (N-(4-[ 18 F]fluoro-benzyl)-2-(2-nitro-1H-imidazol-1-yl)-acet-amide), an 18 F-labeled analogue of antiparasitic drug benznidazole. The present study aimed to analyze its radio-pharmacological properties and systematically compare its PET imaging profiles with [ 18 F]FMISO and [ 18 F]FAZA in preclinical triple-negative (MDA-MB231) and estrogen receptor-positive (MCF-7) breast cancer models., Methods: In vitro cellular uptake experiments were carried out in MDA-MB321 and MCF-7 cells under normoxic and hypoxic conditions. Metabolic stability in vivo was determined in BALB/c mice using radio-TLC analysis. Dynamic PET experiments over 3 h post-injection were performed in MDA-MB231 and MCF-7 tumour-bearing mice. Those PET data were used for kinetic modelling analysis utilizing the reversible two-tissue-compartment model. Autoradiography was carried out in tumour tissue slices and compared to HIF-1α immunohistochemistry. Detailed ex vivo biodistribution was accomplished in BALB/c mice, and this biodistribution data were used for dosimetry calculation., Results: Under hypoxic conditions in vitro cellular uptake was elevated in both cell lines, MCF-7 and MDA-MB231, for all three radiotracers. After intravenous injection, [ 18 F]FBNA formed two radiometabolites, resulting in a final fraction of 65 ± 9 % intact [ 18 F]FBNA after 60 min p.i. After 3 h p.i., [ 18 F]FBNA tumour uptake reached SUV values of 0.78 ± 0.01 in MCF-7 and 0.61 ± 0.04 in MDA-MB231 tumours (both n = 3), representing tumour-to-muscle ratios of 2.19 ± 0.04 and 1.98 ± 0.15, respectively. [ 18 F]FMISO resulted in higher tumour uptakes (SUV 1.36 ± 0.04 in MCF-7 and 1.23 ± 0.08 in MDA-MB231 (both n = 4; p < 0.05) than [ 18 F]FAZA (0.66 ± 0.11 in MCF-7 and 0.63 ± 0.14 in MDA-MB231 (both n = 4; n.s.)), representing tumour-to-muscle ratios of 3.24 ± 0.30 and 3.32 ± 0.50 for [ 18 F]FMISO, and 2.92 ± 0.74 and 3.00 ± 0.42 for [ 18 F]FAZA, respectively. While the fraction per time of radiotracer entering the second compartment (k3) was similar within uncertainties for all three radiotracers in MDA-MB231 tumours, it was different in MCF-7 tumours. The ratios k3/(k3 + k2) and K1*k3/(k3 + k2) in MCF-7 tumours were also significantly different, indicating dissimilar fractions of radiotracer bound and trapped intracellularly: K1*k3/(k2 + k3) [ 18 F]FMISO (0.0088 ± 0.001)/min, n = 4; p < 0.001) > [ 18 F]FAZA (0.0052 ± 0.002)/min, n = 4; p < 0.01) > [ 18 F]FBNA (0.003 ± 0.001)/min, n = 3). In contrast, in MDA-MB231 tumours, only K1 was significantly elevated for [ 18 F]FMISO. However, this did not result in significant differences for K1*k3/(k2 + k3) for all three 2-nitroimidazoles in MDA-MB231 tumours., Conclusion: Novel 2-nitroimidazole PET radiotracer [ 18 F]FBNA showed uptake into hypoxic breast cancer cells and tumour tissue presumably associated with elevated HIF1-α expression. Systematic comparison of PET imaging performance with [ 18 F]FMISO and [ 18 F]FAZA in different types of preclinical breast cancer models revealed a similar tumour uptake profile for [ 18 F]FBNA with [ 18 F]FAZA and, despite its higher lipophilicity, still a slightly higher muscle tissue clearance compared to [ 18 F]FMISO., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Increased energy metabolism followed by enhanced glucose consumption is a hallmark of cancer. Most cancer cells show overexpression of facilitated hexose transporter GLUT1, including breast cancer. GLUT1 is the main transporter for 2-deoxy-2-[ 18 F]fluoro-d-glucose (2-[ 18 F]FDG), the gold standard of positron emission tomography (PET) imaging in oncology. The present study's goal was to develop novel glucose-based dual imaging probes for their use in tandem PET and fluorescence (Fl) imaging. A glucosamine scaffold tagged with a fluorophore and an 18 F-label should confer selectivity to GLUT1. Out of five different compounds, 2-deoxy-2-((7-sulfonylfluoro-2,1,3-benzoxadiazol-4-yl)amino)-d-glucose (2-FBDG) possessed favorable fluorescent properties and a similar potency as 2-deoxy-2-((7-nitro-2,1,3-benzoxadiazol-4-yl)amino)-d-glucose (2-NBDG) in competing for GLUT1 transport against 2-[ 18 F]FDG in breast cancer cells. Radiolabeling with 18 F was achieved through the synthesis of prosthetic group 7-fluoro-2,1,3-benzoxadiazole-4-sulfonyl [ 18 F]fluoride ([ 18 F]FBDF) followed by the reaction with glucosamine. The radiotracer was finally analyzed in vivo in a breast cancer xenograft model and compared to 2-[ 18 F]FDG. Despite favourable in vitro fluorescence imaging properties, 2-[ 18 F]FBDG was found to lack metabolic stability in vivo, resulting in radiodefluorination. Glucose-based 2-[ 18 F]FBDG represents a novel dual-probe for GLUT1 imaging using FI and PET with the potential for further structural optimization for improved metabolic stability in vivo.

Introduction: Radiolabeled peptides play a central role in nuclear medicine as radiotheranostics for targeted imaging and therapy of cancer. We have recently proposed the use of metabolically stabilized GRPR antagonist BBN2 for radiolabeling with 18 F and 68 Ga and subsequent PET imaging of GRPRs in prostate cancer. The present work studied the impact of 44g Sc- and 68 Ga-labeled DOTA complexes attached to GRPR antagonist BBN2 on the in vitro GRPR binding affinity, and their biodistribution and tumor uptake profiles in MCF7 breast and PC3 prostate cancer models., Methods: DOTA-Ava-BBN2 was radiolabeled with radiometals 68 Ga and 44g Sc. Gastrin-releasing peptide receptor (GRPR) affinities of peptides were assessed in PC3 prostate cancer cells. GRPR expression profiles were studied in human breast cancer tissue samples and MCF7 breast cancer cells. PET imaging of 68 Ga- and 44g Sc-labeled peptides was performed in MCF7 and PC3 xenografts as breast and prostate cancer models., Results: Radiopeptides [ 68 Ga]Ga-DOTA-Ava-BBN2 and [ 44g Sc]Sc-DOTA-Ava BBN2 were prepared in radiochemical yields of 70-80% (decay-corrected), respectively. High binding affinities were found for both peptides (IC 50  = 15 nM ( nat Ga) and 5 nM ( nat Sc)). Gene expression microarray analysis revealed high GRPR mRNA expression levels in estrogen receptor (ER)-positive breast cancer, which was further confirmed with Western blot and immunohistochemistry. However, PET imaging showed only low tumor uptake of both radiotracers in MCF7 xenografts ([ 68 Ga]Ga-DOTA-BBN2 (SUV 60min 0.27 ± 0.06); [ 44g Sc]Sc-DOTA-BBN2 (SUV 60min 0.20 ± 0.03)). In contrast, high tumor uptake and retention were found for both radiopeptides in PC3 tumors ([ 68 Ga]Ga-DOTA-BBN2 (SUV 60min 0.46 ± 0.07); [ 44g Sc]Sc-DOTA-BBN2 (SUV 60min 0.51 ± 0.11))., Conclusions: Comparison of 68 Ga- and 44g Sc-labeled DOTA-Ava-BBN2 peptides revealed slight but noticeable differences of the radiometal with an impact on the in vitro GRPR receptor binding properties in PC3 cells. No differences were found in their in vivo biodistribution profiles in MCF7 and PC3 xenografts. Radiopeptides [ 68 Ga]Ga-DOTA-Ava-BBN2 and [ 44g Sc]Sc-DOTA-Ava-BBN2 displayed comparable tumor uptake and retention profiles with rapid blood and renal clearance profiles in both tumor models., Advances in Knowledge and Implications for Patient Care: The favorable PET imaging performance of [ 44g Sc]Sc-DOTA-Ava-BBN2 in prostate cancer should warrant the development of an [ 43 Sc]Sc-DOTA-Ava-BBN2 analog for clinical translation which comes with a main γ-line of much lower energy and intensity compared to 44g Sc., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Autotaxin catalyzes the formation of lysophosphatidic acid, which stimulates tumor growth and metastasis and decreases the effectiveness of cancer therapies. In breast cancer, autotaxin is secreted mainly by breast adipocytes, especially when stimulated by inflammatory cytokines produced by tumors. In this work, we studied the effects of an ATX inhibitor, GLPG1690, which is in phase III clinical trials for idiopathic pulmonary fibrosis, on responses to radiotherapy and chemotherapy in a syngeneic orthotopic mouse model of breast cancer. Tumors were treated with fractionated external beam irradiation, which was optimized to decrease tumor weight by approximately 80%. Mice were also dosed twice daily with GLPG1690 or vehicle beginning at 1 day before the radiation until 4 days after radiation was completed. GLPG1690 combined with irradiation did not decrease tumor growth further compared with radiation alone. However, GLPG1690 decreased the uptake of 3'-deoxy-3'-[ 18 F]-fluorothymidine by tumors and the percentage of Ki67-positive cells. This was also associated with increased cleaved caspase-3 and decreased Bcl-2 levels in these tumors. GLPG1690 decreased irradiation-induced C-C motif chemokine ligand-11 in tumors and levels of IL9, IL12p40, macrophage colony-stimulating factor, and IFNγ in adipose tissue adjacent to the tumor. In other experiments, mice were treated with doxorubicin every 2 days after the tumors developed. GLPG1690 acted synergistically with doxorubicin to decrease tumor growth and the percentage of Ki67-positive cells. GLPG1690 also increased 4-hydroxynonenal-protein adducts in these tumors. These results indicate that inhibiting ATX provides a promising adjuvant to improve the outcomes of radiotherapy and chemotherapy for breast cancer., (©2019 American Association for Cancer Research.)

Hereditary predisposition and causative environmental exposures have long been recognized in human malignancies. In most instances, cancer cases occur sporadically, suggesting that environmental influences are critical in determining cancer risk. To test the influence of genetic polymorphisms on breast cancer risk, we have measured 98 single nucleotide polymorphisms (SNPs) distributed over 45 genes of potential relevance to breast cancer etiology in 174 patients and have compared these with matched normal controls. Using machine learning techniques such as support vector machines (SVMs), decision trees, and naïve Bayes, we identified a subset of three SNPs as key discriminators between breast cancer and controls. The SVMs performed maximally among predictive models, achieving 69% predictive power in distinguishing between the two groups, compared with a 50% baseline predictive power obtained from the data after repeated random permutation of class labels (individuals with cancer or controls). However, the simpler naïve Bayes model as well as the decision tree model performed quite similarly to the SVM. The three SNP sites most useful in this model were (a) the +4536T/C site of the aldosterone synthase gene CYP11B2 at amino acid residue 386 Val/Ala (T/C) (rs4541); (b) the +4328C/G site of the aryl hydrocarbon hydroxylase CYP1B1 at amino acid residue 293 Leu/Val (C/G) (rs5292); and (c) the +4449C/T site of the transcription factor BCL6 at amino acid 387 Asp/Asp (rs1056932). No single SNP site on its own could achieve more than 60% in predictive accuracy. We have shown that multiple SNP sites from different genes over distant parts of the genome are better at identifying breast cancer patients than any one SNP alone. As high-throughput technology for SNPs improves and as more SNPs are identified, it is likely that much higher predictive accuracy will be achieved and a useful clinical tool developed.