^99mTc-Labeled Cyclic RGD Peptides for Noninvasive Monitoring of Tumor Integrin α_vβ₃ Expression

Abstract

This report describes the biologic evaluations of [99mTc(HYNIC-3P-RGD2)(tricine)(TPPTS)] (99mTc-3P-RGD2: 6-hydrazinonicotinyl; 3P-RGD2 = PEG4-E[PEG4-c(RGDfK)]2; PEG4 = 15-amino-4,7,10,13-tetraoxapentadecanoic acid; and TPPTS = trisodium triphenylphosphine-3,3',3''-trisulfonate), [99mTc(HYNIC-3G-RGD2)(tricine)(TPPTS)] (99mTc-3G-RGD2: 3G-RGD2 = G3-E[G3-c(RGDfK)]2 and G3 = Gly-Gly-Gly), and 99mTcO(MAG2-3G-RGD2) (MAG2 = mercaptoacetylglycylglycyl) as radiotracers for noninvasive imaging of tumor integrin αvβ3 expression in five xenografted tumor-bearing models. Biodistribution and imaging studies were performed in athymic nude mice bearing U87MG, MDA-MB-435, A549, HT29, or PC-3 tumor xenografts. Immunochemistry was performed using the cultured primary tumor cells and xenografted tumor tissues. It was found that the radiotracer tumor uptake followed the trend U87MG > MDA-MB-435 ≈ HT29 ≈ A549 > PC-3. The total integrin β3 expression levels followed the general trend: U87MG > MDA-MB-435 ≈ A549∼HT29 > PC-3. There is a linear relationship between the radiotracer injected dose per gram tumor uptake and the total integrin β3 expression levels. On the basis of these, it was concluded that radiotracer tumor uptake is contributed by integrin αvβ3 expressed on tumor cells and activated endothelial cells of the tumor neovasculature. 99mTc-3P-RGD2 has the capability to monitor integrin αvβ3 expression in a noninvasive fashion.

FITC-Conjugated Cyclic RGD Peptides as Fluorescent Probes for Staining Integrin αvβ3/αvβ5 in Tumor Tissues

“…64−66 The integrin α v β 3 /α v β 5 binding affinity followed a general trend: FITC-3P-RGD 2 ∼ FITC-Galacto-RGD 2 > FITC-RGD 2 ≫ c(RGDfK) > FITC-3P-RGK 2 , which was consistent with the results for their DOTA (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetracetic acid) and HYNIC (6-(2-(2-sulfonatobenzaldehyde)hydrazono)nicotinyl) derivatives. 44,60−71 The lower binding affinity of FITC-3P-RGK 2 (IC 50 = 589 ± 73 nM) than that of FITC-3P-RGD 2 (IC 50 = 32 ± 7 nM) clearly demonstrated the RGD-specificity of the FITC-conjugated cyclic RGD peptides.…”

“…36−39,60−62 The overlay experiments between FITC-Galacto-RGD 2 (green color) and CD31 antibody (red color) were performed using five different xenografted tumors (U87MG, MDA-MB-435, A549, HT29, and PC-3). CD31 is a biomarker for endothelial cells on blood vessels.…”

“…We have been using immunohistochemical (IHC) staining with anti-integrin α v β 3 monoclonal antibodies to determine the integrin α v β 3 expression levels on tumor cells (acetone-fixed or living) and in tumor tissues (acetone or methanol-fixed). 60,61 It was found that the IHC staining is an excellent technique to reflect the activation state of integrin α v β 3 because only the activated endothelial cells and some tumor cells are able to bind to the integrin α v β 3 monoclonal antibody. However, the procedures for cellular and tissue staining with fluorescence-labeled anti-integrin α v β 3 antibodies are often complicated and time-consuming because they involve the blocking of nonspecific binding and the use of secondary polyclonal antibody for the fluorescence detection.…”

Peptide Receptor Radionuclide Therapy: An Overview

“…167,187,[189][190][191][192][193][194][195] The receptor binding of one RGD peptide will significantly enhance the local concentration of the other RGD peptide in the vicinity of the receptor, which may lead to a faster rate of receptor binding or a slower rate of dissociation of the dimeric RGD probes. 167,196 While a series of radiolabeled cyclic RGD peptide derivatives, monomeric or multimeric, have been intensively investigated for single-photon emission computed tomography and positron emission tomography (PET) imaging of integrin a v b 3 expression, 186,187,[189][190][191][192][193][194][195][196][197][198][199][200][201][202][203][204][205][206] reports of utilization in receptor-targeted radionuclide therapy are typically still rare. In the last couple of years, a few reports have described the use of tumor-targeting properties of radiolabeled RGD peptides beyond diagnostic applications and therapy monitoring to targeted tumor therapy using therapeutic radionuclides, which primarily include 90 Y and 177 Lu.…”

Utilization of a novel electrochemical 90Sr/90Y generator for the preparation of 90Y-labeled RGD peptide dimer in clinically relevant dose

“…Incorporation of this sequence in cyclic penta-and hexapeptides containing D-amino acids, in a systematic manner resulted in highly potent and selective inhibitor of inegrins [11][12][13][14][15][16]. Based on this concept, a large number of radiolabeled cylic RGD peptides have been developed and evaluated for their potential as radiotracers as angiogenesis markers for non-invasive imaging of tumor growth and metastases in animal models as well as in human patients [14][15][16][17][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35]. In contrast to this, reports on the utilization of radiolabeled RGD peptides in receptor targeted radionuclide therapy are typically rare till date.…”