During the past decade, proof of the principle that peptide receptors can be used successfully for in vivo targeting of human cancers has been provided. The molecular basis for targeting rests on the in vitro observation that peptide receptors can be expressed in large quantities in certain tumors. The clinical impact is at the diagnostic level: in vivo receptor scintigraphy uses radiolabeled peptides for the localization of tumors and their metastases. It is also at the therapeutic level: peptide receptor radiotherapy of tumors emerges as a serious treatment option. Peptides linked to cytotoxic agents are also considered for therapeutic applications. The use of nonradiolabeled, noncytotoxic peptide analogs for long-term antiproliferative treatment of tumors appears promising for only a few tumor types, whereas the symptomatic treatment of neuroendocrine tumors by somatostatin analogs is clearly successful. The present review summarizes and critically evaluates the in vitro data on peptide and peptide receptor expression in human cancers. These data are considered to be the molecular basis for peptide receptor targeting of tumors. The paradigmatic peptide somatostatin and its receptors are extensively reviewed in the light of in vivo targeting of neuroendocrine tumors. The role of the more recently described targeting peptides vasoactive intestinal peptide, gastrin-releasing peptide, and cholecystokinin/gastrin is discussed. Other emerging and promising peptides and their respective receptors, including neurotensin, substance P, and neuropeptide Y, are introduced. This information relates to established and potential clinical applications in oncology.

/pdf/peptide-receptors-as-molecular-targets-for-cancer-diagnosis-43jzca3l3a.pdf

Peptide receptors as molecular targets for cancer diagnosis and therapy.

Human cancer cells overexpress many peptide receptors as molecular targets. Radiolabeled peptides that bind with high affinity and specificity to the receptors on tumor cells hold great potential for both diagnostic imaging and targeted radionuclide therapy. The advantage of solid-phase peptide synthesis, the availability of different chelating agents and prosthetic groups and bioconjugation techniques permit the facile preparation of a wide variety of peptide-based targeting molecules with diverse biological and tumor targeting properties. Some of these peptides, including somatostatin, bombesin, vasoactive intestinal peptide, gastrin, neurotensin, exendin and RGD are currently under investigation. It is anticipated that in the near future many of these peptides may find applications in nuclear oncology. This article presents recent developments in the field of small peptides, and their applications in the diagnosis and treatment of cancer.

/pdf/radiolabeled-peptides-valuable-tools-for-the-detection-and-3zt22ucn15.pdf

Radiolabeled peptides: valuable tools for the detection and treatment of cancer.

Pituitary adenylate cyclase-activating polypeptide (PACAP) has been originally isolated from the sheep hypothalamus on the basis of its ability to stimulate cAMP formation in anterior pituitary cells. Post-translational processing of the PACAP precursor generates two biologically active molecular forms, PACAP38 and PACAP27, and a novel peptide called PACAP-related peptide whose activity remains unknown. The primary structure of PACAP has been remarkably conserved during evolution, from protochordates to mammals, suggesting that the peptide exerts important activities throughout the vertebrate phylum. The sequence of PACAP27 exhibits substantial similarities with those of vasoactive intestinal polypeptide (VIP), glucagon and secretin. The gene encoding the PACAP precursor is widely expressed in the brain and in various peripheral organs, notably in endocrine glands, the gastro-intestinal and uro-genital tracts and the respiratory system. In vivo and in vitro studies have shown that PACAP exerts multiple activities as a hormone, neurohormone, neurotransmitter or trophic factor. For instance, PACAP triggers the release of insulin and glucagon, activates steroidogenesis in the adrenal gland and gonads, and stimulates the secretion of most hypophysial cells. PACAP exerts a potent relaxant activity on smooth muscle fibers in blood vessels, lung and gut. In the brain, PACAP stimulates the electrical activity of various populations of neurons and increases tyrosine hydroxylase gene expression. Recent studies have shown that PACAP exerts a trophic activity during ontogenesis, notably in the adrenal medulla and in the central nervous system. The biological effects of PACAP are mediated through three distinct receptor subtypes which exhibit differential affinities for PACAP and VIP. The PAC1 receptor, which shows high selectivity for PACAP, is coupled to several transduction systems. In contrast, VPAC1 and VPAC2, which bind with the same affinity PACAP and VIP, are mainly coupled to the adenylyl cyclase pathway. The bronchodilatator and vasorelaxant effects of PACAP, as well as the antiproliferative and neuroprotective actions of the peptide, make it a valuable target for new drug development.

[Pituitary adenylate cyclase-activating polypeptide].

Peptide-based radiopharmaceuticals and cytotoxic conjugates: Potential tools against cancer

Molecular imaging is broadly defined as the characterization and measurement of biological processes in living animals, model systems, and humans at the cellular and molecular level using remote imaging detectors. One underlying premise of molecular imaging is that this emerging field is not defined by the imaging technologies that underpin acquisition of the final image per se, but rather is driven by the underlying biological questions. In practice, the choice of imaging modality and probe is usually reduced to choosing between high spatial resolution and high sensitivity to address a given biological system. Positron emission tomography (PET) and single-photon emission computed tomography (SPECT) inherently use image-enhancing agents (radiopharmaceuticals) that are synthesized at sufficiently high specific activity to enable use of tracer concentrations of the compound (picomolar to nanomolar) for detecting molecular signals while providing the desired levels of image contrast. The tracer technologies strategically provide high sensitivity for imaging small-capacity molecular systems in vivo (receptors, enzymes, transporters) at a cost of lower spatial resolution than other technologies. We review several significant PET and SPECT advances in imaging receptors (somatostatin receptor subtypes, neurotensin receptor subtypes, v3 integrin), enzymes (hexokinase, thymidine kinase), transporters (MDR1 P-glycoprotein, sodium-iodide symporter), and permeation peptides (human immunodeficiency virus type 1 (HIV-1) Tat conjugates), as well as innovative reporter gene constructs (herpes simplex virus 1 thymidine kinase, somatostatin receptor subtype 2, cytosine deaminase) for imaging gene promoter activation and repression, signal transduction pathways, and protein-protein interactions in vivo.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/jmri.10182

Molecular imaging of gene expression and protein function in vivo with PET and SPECT

99mTc labeled VIP analog: evaluation for imaging colorectal cancer.

Handle everyday research tasks with reliable, citation-backed results

Your personal Research Agent to handle research tasks with citation-backed results

Popular Tasks used by Researchers

How can I help with your research?

Meet SciSpace

Get more enhanced response by uploading the PDFs you want me to reference.

No relevant PDFs in your library

SciSpace is the AI research assistant for academics. Run systematic literature reviews on 280M+ papers, and write papers with cited sources. Trusted by 1M+ students, PhDs & researchers.

SciSpace | AI for Research

Analyze PDFs

Code & Manuscripts

Funding & Grants

Literature & Patents

Medical & Clinical Data

Systematic Review

Visualize & Present

Web & Data

Build a Google Scholar-like website for your research.

Build a website

Create charts and images for your research

Create a Chart

Write a paper for submission to a journal

Draft a manuscript

Patent Search

Design eye-catching scientific posters in minutes.

Scientific Poster Generation

Systematic Literature Review

One task is running at the moment. Your messages will be shown right after.

Drag and drop or click here to browse

Loved by <highlight>1 million+</highlight> researchers

Extract a list of specific topics and their sources from unstructured text

Topics

Compare and analyze relevant papers that matches with your search

Papers

Get insights from PDFs and bookmarked papers from your library

My library

Recent searches

Try searching for:

Catch AI-generated content in scholarly and non-scholarly content

{ai} Detector

Ai Writer

Get PDF Summaries, highlighted text explanations 

Chat with PDF

Effortlessly create in-text citations and bibliographies in APA and 2,500 other formats

Citation generator

Get explanations, summaries, and answers on academic papers

Ease up your research workflow with {scispace}'s cohort of exciting AI tools

Elevate your academic writing skills and convey your ideas the way you want

Paraphraser

Explore our range of reading and writing tools

Your file is being prepared and should be ready in a few minutes. If it's a large file, it might take a bit longer. You can close this window, and we'll email you the file when it's done.

You have reached a maximum limit of <strong>{limit}</strong> columns in the table. Remove at least <strong>1</strong> column to add or create another one.

C.S. Marcus

Author Tools

Chat about Author

Papers

99mTc labeled VIP analog: evaluation for imaging colorectal cancer.