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Despite efforts, cancer is still one of the leading causes of morbidity and mortality worldwide, with approximately 14 million new cases and 8.2 million cancer-related deaths each year, according to the World Health Organization. Among the strategies to reduce cancer progression and improving its management, implementing early detection technologies is crucial. Based on the fact that several types of cancer cells overexpress surface receptors, small molecule ligands, such as peptides, have been developed to allow tumor identification at earlier stages. Allied with imaging techniques such as PET and SPECT, radiolabeled peptides play a pivotal role in nuclear medicine. Bombesin, a peptide of 14 amino acids, is an amphibian homolog to the mammalian gastrin-releasing peptide (GRP), that has been extensively studied as a targeting ligand for diagnosis and therapy of GRP positive tumors, such as breast, pancreas, lungs and prostate cancers. In this context, herein we provide a review of reported bombesin derivatives radiolabeled with a multitude of radioactive isotopes for diagnostic purposes in the preclinical setting. Moreover, since animal models are highly relevant for assessing the potential of clinical translation of this radiopeptides, a brief report of the currently used GRP-positive tumor-bearing animal models is described. [ABSTRACT FROM AUTHOR]

Bombesin is a tetradecapeptide that binds specifically to gastrin releasing peptide receptors in humans. Several forms of cancer, including lung, prostate, breast, and colon express receptors for bombesin-like peptides. Radiolabeled bombesin analogs with a high affinity for these receptors might therefore be used for scintigraphic imaging of these tumor types. A truncated bombesin derivative (HYNIC-βAla-Bombesin) was radiolabeled with technetium-99m using EDDA and tricine as coligands. In vitro stability was evaluated in presence of plasma and excess of cysteine. The receptor-binding affinity assays was evaluated in MDA-MB-231 cancer cell line. In addition, in vivo biodistribution was performed in nude mice bearing breast tumor. In vitro assay showed a good affinity for the MDA-MB-231 cell line, showing 20.0 % of internalization at 4 h post-administration. Tc-HYNIC-βAla-Bombesin biodistribution revealed a rapid clearance and a significant renal excretion. In addition, tumor uptake was higher than non-excretory organs, such as the spleen, the liver, and muscles. Tumor-to-muscle and tumor-to-blood ratios for Tc-HYNIC-βAla-Bombesin showed high values at 4 h post-injection (5.34 and 4.55, respectively). Furthermore, blocked studies using cold bombesin peptide were performed, which demonstrated an important decrease in tumor uptake, indicating a tumor specificity for Tc-HYNIC-βAla-Bombesin. The Tc-HYNIC-βAla-Bombesin displayed suitable radiochemical characteristics, and adequate affinity to breast tumor cells (MDA-MB-231). Therefore, this analog can be considered as a candidate for the identification of bombesin-positive tumors. [ABSTRACT FROM AUTHOR]

Abstract: Bombesin (BBN) is a tetradecapeptide that binds specifically to gastrin-releasing peptide receptors. Several forms of cancer, including lung, prostate, breast, and colon express receptors for bombesin-like peptides. Radiolabeled BBN analogs with a high affinity for these receptors might be used for scintigraphic imaging. Kit formulations for labeling these molecules are important for routine preparation. A freeze-dried kit for labeling HYNIC-βAla-Bombesin(7–14) with technetium-99m was prepared, and its storage stability was evaluated by in vitro and in vivo assays. [Copyright &y& Elsevier]

Abstract: A bombesin derivative was successfully radiolabeled in high labeling yield. Biodistribution studies and scintigraphic images in Ehrlich tumor-bearing mice were performed. This compound showed high accumulation in tumor tissue with high tumor-to-muscle and tumor-to-blood ratios. Thus, 99mTc-HYNIC-Bombesin(7–14) could be used as an agent for tumor diagnosis. [ABSTRACT FROM AUTHOR]