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Development of molecular probes for imaging sigma-2 receptors in vitro and in vivo
Robert Henry Mach1, Kenneth Theodore Wheeler
1Mallinckrodt Institute of Radiology, Washington University School of Medicine, St. Louis, MO 63110, USA. rhmach@mir.wustl.edu
Abstract:
The sigma-2 (sigma(2)) receptor is proving to be an important protein in the field of cancer biology. The observations that sigma(2) receptors have a 10-fold higher density in proliferating tumor cells than in quiescent tumor cells, and that sigma(2) receptor agonists are capable of killing tumor cells via apoptotic and non-apoptotic mechanisms, indicate that this receptor is an important molecular target for the development of radiotracers for imaging tumors using techniques such as Positron Emission Tomography (PET) and Single Photon Emission Computed Tomography (SPECT) and for the development of cancer chemotherapeutic agents. In spite of recent promising results towards achieving these goals, research in this field has been hampered by the fact that the molecular identity of the protein sequence of the sigma(2) receptor is currently not known. Consequently, most of what is known about this protein has been obtained using either radiolabeled or fluorescent probes for this receptor, or biochemical analysis of the effect of sigma(2) selective ligands on cells growing under tissue culture conditions. This article provides a review of the development and use of sigma(2) receptor ligands, and how these ligands have been used with a variety of in vitro and in vivo models to gain a greater understanding of the role this receptor plays in cancer.
Insights
The sigma-2 (sigma(2)) receptor is a promising target for cancer imaging and therapy due to its higher density in tumor cells. Ligand development is crucial for understanding its role in cancer, despite its unknown molecular identity.
Area of Science:
- Oncology
- Molecular Biology
- Pharmacology
Background:
- The sigma-2 (sigma(2)) receptor is overexpressed in proliferating tumor cells compared to quiescent cells.
- Sigma-2 receptor agonists demonstrate potent tumor cell-killing capabilities through apoptotic and non-apoptotic pathways.
- This receptor represents a significant molecular target for novel cancer diagnostics and therapeutics.
Purpose of the Study:
- To review the development and application of sigma-2 receptor ligands.
- To explore the utility of these ligands in understanding the sigma-2 receptor's role in cancer.
- To highlight the potential of sigma-2 receptor-targeted agents for cancer imaging and therapy.
Main Methods:
- Review of existing literature on sigma-2 receptor ligands.
- Analysis of studies utilizing radiolabeled and fluorescent probes.
- Examination of biochemical analyses of sigma-2 selective ligand effects on cell cultures.
- In vitro and in vivo model studies.
Main Results:
- Sigma-2 receptor ligands have been instrumental in investigating the receptor's function in cancer.
- Despite the unknown molecular identity of the sigma-2 receptor, significant progress has been made.
- Ligand-based approaches have provided insights into the receptor's role in tumor cell proliferation and death.
Conclusions:
- The sigma-2 receptor is a validated target for cancer therapy and imaging.
- Further research into sigma-2 receptor ligands is essential for advancing cancer treatment strategies.
- Development of targeted radiotracers (PET, SPECT) and chemotherapeutic agents is a key focus.
