99mTc-Labeled Vasopressin Peptide as a Radiopharmaceutical for Small-Cell Lung Cancer (SCLC) Diagnosis

A snake toxin as a theranostic agent for the type 2 vasopressin receptor

Rationale: MQ1, a snake toxin which targets with high nanomolar affinity and absolute selectivity for the type 2 vasopressin receptor (V2R), is a drug candidate for renal diseases and a molecular probe for imaging cells or organs expressing V2R.

Methods: MQ1's pharmacological properties were characterized and applied to a rat model of hyponatremia. Its PK/PD parameters were determined as well as its therapeutic index. Fluorescently and radioactively labeled MQ1 were chemically synthesized and associated with moderate loss of affinity. MQ1's dynamic biodistribution was monitored by positron emission tomography. Confocal imaging was used to observe the labeling of three cancer cell lines.

Results: The inverse agonist property of MQ1 very efficiently prevented dDAVP-induced hyponatremia in rats with low nanomolar/kg doses and with a very large therapeutic index. PK (plasma MQ1 concentrations) and PD (diuresis) exhibited a parallel biphasic decrease. The dynamic biodistribution showed that MQ1 targets the kidneys and then exhibits a blood and kidney biphasic decrease. Whatever the approach used, we found a T1/2α between 0.9 and 3.8 h and a T1/2β between 25 and 46 h and demonstrated that the kidneys were able to retain MQ1. Finally, the presence of functional V2R expressed at the membrane of cancer cells was, for the first time, demonstrated with a specific fluorescent ligand.

Conclusion: As the most selective V2 binder, MQ1 is a new promising drug for aquaresis-related diseases and a molecular probe to visualize in vitro and in vivo V2R expressed physiologically or under pathological conditions.

Research Progress Evaluating the Function and Mechanism of Anti-Tumor Peptides

Malignant tumors cause a high mortality rate worldwide, and they severely threaten human health and negatively affect the economy. Despite the advancements in tumor-related molecular genetics and effective new processes in anti-tumor drug development, the anti-tumor drugs currently used in clinical practice are inadequate due to their poor efficacy or severe side effects. Therefore, developing new safe and efficient drugs is a top priority for curing cancer. The peptide has become a suitable agent due to its exact molecular weight between whole protein and small molecule, and it has high targeting ability, high penetrability, low immunogenicity, and is convenient to synthesize and easy to modify. Because of these advantages, peptides have excellent prospect for application as anti-tumor agents. This article reviews the recent research progress evaluating anti-tumor peptides and their anti-tumor mechanisms, and may act as a reference for the future development and clinical application of anti-tumor peptides.

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Radiolabeling and in vitro evaluation of a new 5-fluorouracil derivative with cell culture studies

The clinical impact and accessibility of ^99m Tc tracers for cancer diagnosis would be greatly enhanced by the availability of a new, simple, and easy labeling process and radiopharmaceuticals. 5-Fluorouracil is an antitumor drug, which has played an important role for the treatment of breast carcinoma. In the present study, a new derivative of 5-Fluorouracil was synthesized as (1-[{1'-(1''-deoxy-2'',3'':4'',5''-di-O-isopropylidene-β-D-fructopyranose-1''-yl)-1'H-1',2', 3'-triazol-4'-yl}methyl]-5-fluorouracil) (E) and radiolabeled with ^99m Tc. It was analyzed by radio thin layer chromatography for quality control and stability. The radiolabeled complex was subjected to in vitro cell-binding studies to determine healthy and cancer cell affinity using HaCaT and MCF-7 cells, respectively. In addition, in vitro cytotoxicity studies of compound E were performed with HaCaT and MCF-5 cells. The radiochemical purity of the [^99m Tc]TcE was found to be higher than 90% at room temperature up to 6 hours. The radiolabeled complex showed higher specific binding to MCF-7 cells than HaCaT cells. IC₅₀ values of E were found 31.5 ± 3.4 μM and 20.7 ± 2.77 μM for MCF-7 and HaCaT cells, respectively. The results demonstrated the potential of a new radiolabeled E with ^99m Tc has selective for breast cancer cells.

Chelators and metal complex stability for radiopharmaceutical applications

Diagnostic and therapeutic nuclear medicine relies heavily on radiometal nuclides. The most widely used and well-known radionuclide is technetium-99m (99mTc), which has dominated diagnostic nuclear medicine since the advent of the 99Mo/99mTc generator in the 1960s. Since that time, many more radiometals have been developed and incorporated into potential radiopharmaceuticals. One critical aspect of radiometal-containing radiopharmaceuticals is their stability under in vivo conditions. The chelator that is coordinated to the radiometal is a key factor in determining radiometal complex stability. The chelators that have shown the most promise and are under investigation in the development of diagnostic and therapeutic radiopharmaceuticals over the last 5 years are discussed in this review.

Binding of Cu+ and Cu2+ with peptides: Peptides = oxytocin, Arg8 -vasopressin, bradykinin, angiotensin-I, substance-P, somatostatin, and neurotensin

The intrinsic binding ability of 7 natural peptides (oxytocin, arg⁸ -vasopressin, bradykinin, angiotensin-I, substance-P, somatostatin, and neurotensin) with copper in 2 different oxidation states (Cu^I/II ) derived from different Cu^+/2+ precursor sources have been investigated for their charge-dependent binding characteristics. The peptide-Cu^I/II complexes, [M - (n-1)H + nCu^I ] and [M - (2n-1)H + nCu^II ], are prepared/generated by the reaction of peptides with CuI solution/Cu-target and CuSO₄ solution and are analyzed by using matrix-assisted laser desorption/ionization (MALDI) time-of-flight mass spectrometry. The MALDI mass spectra of both [M - (n-1)H + nCu^I ] and [M - (2n-1)H + nCu^II ] complexes show no mass shift due to the loss of ─H atoms in the main chain ─NH of these peptides by Cu⁺ and Cu²⁺ deprotonation. The measured m/z value indicates the reduction of Cu^I/II oxidation state into Cu⁰ during MALDI processes. The number and relative abundance of Cu⁺ bound to the peptides are greater compared with the Cu²⁺ bound peptides. Oxytocin, arg⁸ -vasopressin, bradykinin, substance-P, and somatostatin show the binding of 5Cu⁺ , and angiotensin-I and neurotensin show the binding of 7Cu⁺ from both CuI and Cu targets, while bradykinin shows the binding of 2Cu²⁺ , oxytocin, arg⁸ -vasopressin, angiotensin-I, and substance-P; somatostatin shows the binding of 3Cu²⁺ ; and neurotensin shows 4Cu²⁺ binding. The binding of more Cu⁺ with these small peptides signifies that the bonding characteristics of both Cu⁺ and Cu²⁺ are different. The amino acid residues responsible for the binding of both Cu⁺ and Cu²⁺ in these peptides have been identified based on the density functional theory computed binding energy values of Cu⁺ and the fragment transformation method predicted binding preference of Cu²⁺ for individual amino acids.

Exploiting cancer's phenotypic guise against itself: targeting ectopically expressed peptide G-protein coupled receptors for lung cancer therapy

Lung cancer, claiming millions of lives annually, has the highest mortality rate worldwide. This advocates the development of novel cancer therapies that are highly toxic for cancer cells but negligibly toxic for healthy cells. One of the effective treatments is targeting overexpressed surface receptors of cancer cells with receptor-specific drugs. The receptors-in-focus in the current review are the G-protein coupled receptors (GPCRs), which are often overexpressed in various types of tumors. The peptide subfamily of GPCRs is the pivot of the current article owing to the high affinity and specificity to and of their cognate peptide ligands, and the proven efficacy of peptide-based therapeutics. The article summarizes various ectopically expressed peptide GPCRs in lung cancer, namely, Cholecystokinin-B/Gastrin receptor, the Bombesin receptor family, Bradykinin B1 and B2 receptors, Arginine vasopressin receptors 1a, 1b and 2, and the Somatostatin receptor type 2. The autocrine growth and pro-proliferative pathways they mediate, and the distinct tumor-inhibitory effects of somatostatin receptors are then discussed. The next section covers how these pathways may be influenced or 'corrected' through therapeutics (involving agonists and antagonists) targeting the overexpressed peptide GPCRs. The review proceeds on to Nano-scaled delivery platforms, which enclose chemotherapeutic agents and are decorated with peptide ligands on their external surface, as an effective means of targeting cancer cells. We conclude that targeting these overexpressed peptide GPCRs is potentially evolving as a highly promising form of lung cancer therapy.

Nanobubbles as ultrasound contrast agent for facilitating small cell lung cancer imaging

Background

This study is to investigate whether liposome-loaded nanobubbles (NBs) have the potentials to carry anti-pro-gastrin releasing peptide (proGRP) antibody and enhance ultrasound imaging of small cell lung cancer (SCLC).

Methods

NBs were loaded with an antibody against SCLC (H446 cell line). A nude mouse model of SCLC tumor was established by a subcutaneous injection of tumor cell suspension in the dorsal skin. Images for contrast-enhanced ultrasound (CEUS) of xenograft tumors in the model were obtained through an intravenous injection of blank and targeting NBs.

Results

The targeted NBs showed a high binding affinity (90.2 ± 3.24%) of the H446 cells in vitro as compared to the blank NBs that have no affinity of the cells. In process of tumor imaging, no mice died of the NB application. CEUS imaging of the targeted NBs manifested significant increases in half-peak time, area under the curve and peak intensity as compared to the blank NBs. In the model of SCLC, treatment with targeting NBs resulted in a large amount of fluorescent dye accumulated in the tumor tissue but not the liver tissue.

Conclusion

Our results indicate that NBs can carry antibody traveling to the SCLC cells, whereas application of NBs is safe and reliable in serving as ultrasound contrast agents for improving SCLC imaging.

Radiolabeling in Biology

Chemistry is the science of chemical reactions, the study of chemical properties, composition, and structure of a molecule. When the molecule under observation is of a biological origin (proteins, carbohydrates, lipids, or nucleic acids), the study of its chemical properties, reactions, and structure is known as biochemistry. Similarly, if the molecule or a biochemical under observation is radioactive, the science becomes radiochemistry or radio biochemistry. So, chemistry is the science which fuses these two diverse fields of applied sciences. Fusion of these two sciences on chemistry platform has enabled the development of various new radioactive formulations which are called as radiopharmaceuticals and are being used the world over for clinical as well as experimental purposes. For the successful development of radiopharmaceuticals, we require in-depth understanding of both biochemistry as well as radiochemistry. So, the present review article summarizes basic relevant details and experimental advances in both these sciences with regard to development of radiopharmaceuticals.

Analysis of argentinated peptide complexes using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry: Peptide = oxytocin, arg(8) -vasopressin, bradykinin, bombesin, somatostatin, neurotensin

RATIONALE

The increased use of silver nanoparticles (AgNPs) for various biological applications, and over-expression of various peptide receptors in different tumors/cancer cells, necessitate the need for dedicated investigations on the intrinsic binding ability of Ag with various biologically important peptides for better understanding of AgNPs-peptide interactions and for the future development of contrasting agents as well as drugs for imaging/biomedical applications.

METHODS

The [M+(Ag)n ](+) complexes are prepared and characterized using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS).

RESULTS

Silver complexes of the peptides [M+(Ag)n ](+) , where M = oxytocin, arg(8) -vasopressin, bradykinin, bombesin, somatostatin, and neurotensin, have been investigated for their intrinsic Ag(+) -binding ability. Unusual binding of up to seven Ag(+) with these small peptides is observed. The mass spectra show n = 1-5 for bombesin and somatostatin, n = 1-6 for bradykinin and arg(8) -vasopressin, and n = 1-7 for oxytocin and neurotensin. In addition, oxytocin and arg(8) -vasopressin show the formation of dimers and their complexes [M2 +(Ag)n ](+) with n = 1-8 and n = 1-5, respectively. The possible amino acid residues responsible for Ag(+) binding in each peptide have been identified on the basis of density functional theory (DFT)-calculated binding energy values of Ag(+) towards individual amino acids.

CONCLUSIONS

Mass spectrometric evidence indicates that the peptides, viz., oxytocin, arg(8) -vasopressin, bradykinin, bombesin, somatostatin, and neurotensin, show greater affinity for Ag(+) . Hence, they may be used as carriers for AgNPs in targeted drug delivery as well as an alternative for iodinated contrasting agents in dual energy X-ray imaging techniques. Radio-labeled Ag with these peptides can also be used in radio-pharmaceuticals for diagnostic and therapeutic applications. Copyright © 2016 John Wiley & Sons, Ltd.

The chemistry and biology of guanidine natural products

The present review discusses the isolation, structure determination, synthesis, biosynthesis and biological activities of secondary metabolites bearing a guanidine group.

Peptide-Based Treatment: A Promising Cancer Therapy

Many new therapies are currently being used to treat cancer. Among these new methods, chemotherapy based on peptides has been of great interest due to the unique advantages of peptides, such as a low molecular weight, the ability to specifically target tumor cells, and low toxicity in normal tissues. In treating cancer, peptide-based chemotherapy can be mainly divided into three types, peptide-alone therapy, peptide vaccines, and peptide-conjugated nanomaterials. Peptide-alone therapy may specifically enhance the immune system's response to kill tumor cells. Peptide-based vaccines have been used in advanced cancers to improve patients' overall survival. Additionally, the combination of peptides with nanomaterials expands the therapeutic ability of peptides to treat cancer by enhancing drug delivery and sensitivity. In this review, we mainly focus on the new advances in the application of peptides in treating cancer in recent years, including diagnosis, treatment, and prognosis.