α-MSH Receptor Autoradiography on Mouse and Human Melanoma Tissue Sections and Biopsies

Abstract

MSH receptors and their binding characteristics of [125I]-labelled derivatives of alpha-MSH have been studied extensively on various mouse and human melanoma cell lines in culture. The aim of this study was to determine the binding characteristics of alpha-MSH radioligands to MSH receptors occurring in experimental mouse and human melanoma tumours as well as in human melanoma biopsies. For this reason, solid tumours were grown on experimental animals by inoculation of murine B16-F1 and human D10 and HBL melanoma cells. After excision and cryosectioning of the tumours, frozen tissue sections were incubated with [(125I)Tyr2]-alpha-MSH or [(125I)Tyr2,Nle4,D-Phe7]-alpha-MSH and specific alpha-MSH binding sites were visualized by subsequent autoradiography. The presence of increasing concentrations of unlabelled alpha-MSH during incubation with tracer led to a dose-dependent displacement of the radioligand. Quantitative analysis of the autoradiograms produced dissociation constants which were comparable with those obtained with cell binding assays: KD = 1.87 and 1.31 nmol/l for B16 tumours and cells, respectively; 0.32 and 0.33 nmol/l for D10, and 2.24 and 1.36 nmol/l for HBL tumours and cells, respectively. This indicates similar binding properties of alpha-MSH radioligands to both cultured melanoma cells and tissue sections of melanoma tumours from experimental animals. Similar binding characteristics were also observed with human melanoma tissue sections originating from biopsies of melanoma patients.

Synthetic Peptide Drugs for Targeting Skin Cancer: Malignant Melanoma and Melanotic Lesions

“…This is followed by a kinetic analysis of the cellular uptake of the radiopeptide and retention of the radionuclide by melanoma cells, an example of which is presented in Figure 3. In addition, receptor autoradiography with melanoma tissue sections in vitro is frequently applied to examine MC1R distribution in the tumor [75]. In vivo, PET, planar scintigraphy or SPECT have become the primary examination methods, but autoradiography of tumor sections taken after in vivo biodistribution studies may complement imaging because it can unveil unconspicuous details of tumor lesions [79].…”

“…As mentioned above, open-chain DTPA was the chelator employed for the initial studies of radiotargeting melanoma, not least because of the mild conditions for complex formation with 111 In [71][72][73][74][75]. However, the stability of DTPA-radiometal complexes in vivo was frequently insufficient, in particular that of [ 90 Y]DTPA [93].…”

Radiochemical and radiopharmacological characterization of a 64Cu‐labeled α‐MSH analog conjugated with different chelators

“…Melanocortin‐1 receptor (MC1R), a member of G‐protein‐coupled receptors, is well known to be overexpressed in isolated melanoma cells and melanoma tissues. It represents one of the few specific targets potentially useful for diagnosis and therapy of metastatic melanoma . α‐melanocyte‐stimulating hormone (α‐MSH, sequence: Ac‐Ser‐Tyr‐Ser‐Met‐Glu‐His‐Phe‐Arg‐Trp‐Gly‐Lys‐Pro‐Val‐NH 2 ) is a proopiomelanocortin (POMC)–derived peptide hormone with the biological active sequence His‐Phe‐Arg‐Trp, but it displays a short biological half‐life in human (4.8 min for iodinated and 25 min for tritiated α‐MSH) .…”

Radiolabeled α‐melanocyte‐stimulating hormone analogs for receptor‐mediated targeting of melanoma: from tritium to indium

“…Thus, radiolabeled monoclonal antibodies or antibody fragments directed against specific melanoma cell epitopes (Beaumier et al, 1985;Salk, 1988;Taylor et al, 1988;Marchitto et al, 1989) have been studied but their clinical application has been restrained because of the occurrence of individual tumor variants. The finding that isolated melanoma cells and melanoma tissues (over)express melanocortin-1 receptors (MC1R) (Siegrist et al, 1989(Siegrist et al, , 1992Tatro et al, 1990a;Bagutti et al, 1995;Jiang et al, 1996;Loir et al, 1999) has opened up the perspective of using radiolabeled -MSH analogs as imaging tools. As compared with the use of antibodies or antibody fragments, the application of small peptides as vectors offers several advantages such as negligible immunogenicity, better tumor penetration and faster blood clearance.…”