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High expression of integrin αvβ3 enables uptake of targeted fluorescent probes into ovarian cancer cells and tumors.

ABSTRACT: The cell line OVCAR-4 was recently ranked as one of the most representative cell lines for high grade serous ovarian cancer (HGSOC). However, little work has been done to assess the susceptibility of OVCAR-4 cells and tumors to the more common types of molecular targeting. Proteome profiles suggest OVCAR-4 express high levels of integrin αvβ3 receptors. Using flow cytometry with fluorescent antibodies we determined that OVCAR-4 cells have high number of integrin αvβ3 receptors ([9.8 ± 2.5] × 10⁴/cell) compared to the well-characterized cell line U87-MG ([5.2 ± 1.4] × 10⁴/cell). However, OVCAR-4 cells also have roughly three times the surface area of U87-MG cells, so the average αvβ3 receptor density is actually lower (11 ± 3 versus 18 ± 6 receptors/µm²). A series of new fluorescent molecular probes was prepared with structures comprised of a deep-red squaraine fluorophore (∼680 nm emission) covalently attached to zero, one, or two cyclic pentapeptide cRGD sequences for integrin targeting. Microscopy studies showed that uptake of the divalent probe into cultured OVCAR-4 cells was 2.2 ± 0.4 higher than the monovalent probe, which in turn was 2.2 ± 0.4 higher than the untargeted probe. This probe targeting trend was also seen in OVCAR-4 mouse tumor models. The results suggest that clinically relevant OVCAR-4 cells can be targeted using molecular probes based on αvβ3 integrin receptor antagonists such as the cRGD peptide. Furthermore, deep-red fluorescent cRGD-squaraine probes have potential as targeted stains of cancerous tissue associated with HGSOC in surgery and pathology settings.

SUBMITTER: Shaw SK

PROVIDER: S-EPMC5963687 | biostudies-literature | 2018 May

REPOSITORIES: biostudies-literature

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High expression of integrin αvβ3 enables uptake of targeted fluorescent probes into ovarian cancer cells and tumors.

Shaw Scott K SK Schreiber Cynthia L CL Roland Felicia M FM Battles Paul M PM Brennan Seamus P SP Padanilam Simon J SJ Smith Bradley D BD

Bioorganic & medicinal chemistry 20180306 8

The cell line OVCAR-4 was recently ranked as one of the most representative cell lines for high grade serous ovarian cancer (HGSOC). However, little work has been done to assess the susceptibility of OVCAR-4 cells and tumors to the more common types of molecular targeting. Proteome profiles suggest OVCAR-4 express high levels of integrin αvβ3 receptors. Using flow cytometry with fluorescent antibodies we determined that OVCAR-4 cells have high number of integrin αvβ3 receptors ([9.8 ± 2.5] × 10< ...[more]

PMID: 29548784

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Project description:This study sought to evaluate FITC-conjugated cyclic RGD peptides (FITC-RGD2, FITC-3P-RGD2, and FITC-Galacto-RGD2) as fluorescent probes for in vitro assays of integrin αvβ3/αvβ5 expression in tumor tissues. FITC-RGD2, FITC-3P-RGD2, and FITC-Galacto-RGD2 were prepared, and their integrin αvβ3/αvβ5 binding affinity was determined using the displacement assay against (125)I-echistatin bound to U87MG glioma cells. IC50 values of FITC-Galacto-RGD2, FITC-3P-RGD2, and FITC-RGD2 were calculated to be 28 ± 8, 32 ± 7, and 89 ± 17 nM, respectively. The integrin αvβ3/αvβ5 binding affinity followed a general trend: FITC-Galacto-RGD2 ∼ FITC-3P-RGD2 > FITC-RGD2. The xenografted tumor-bearing models were established by subcutaneous injection of 5 × 10(6) tumor cells into shoulder flank (U87MG, A549, HT29, and PC-3) or mammary fat pad (MDA-MB-435) of each athymic nude mouse. Three to six weeks after inoculation, the tumor size was 0.1-0.3 g. Tumors were harvested for integrin αvβ3/αvβ5 staining, as well as hematoxylin and eosin (H&E) staining. Six human carcinoma tissues (colon cancer, pancreatic cancer, lung adenocarcinoma, squamous cell lung cancer, gastric cancer, and esophageal cancer) were obtained from recently diagnosed cancer patients. Human carcinoma slides were deparaffinized in xylene, rehydrated with ethanol, and then used for integrin αvβ3/αvβ5 staining, as well as H&E staining. It was found that the tumor staining procedures with FITC-conjugated cyclic RGD peptides were much simpler than those with the fluorescence-labeled integrin αvβ3 antibodies. Since FITC-RGD2, FITC-3P-RGD2, and FITC-Galacto-RGD2 were able to co-localize with the fluorescence-labeled integrin β3 antibody, their tumor localization and tumor cell binding are integrin αvβ3-specific. Quantification of the fluorescent intensity in five xenografted tumors (U87MG, MDA-MB-435, A549, HT29, and PC-3) and six human carcinoma tissues revealed an excellent linear relationship between the relative integrin αvβ3/αvβ5 expression levels determined with FITC-Galacto-RGD2 and those obtained with the fluorescence-labeled anti-human integrin β3 antibody. There was also an excellent linear relationship between the tumor uptake (%ID/g) of (99m)Tc-3P-RGD2 (an integrin αvβ3/αvβ5-targeted radiotracer) and the relative integrin αvβ3/αvβ5 expression levels from the quantification of fluorescent intensity in the tumor tissues stained with FITC-Galacto-RGD2. These results suggest that FITC-conjugated cyclic RGD peptides might be useful to correlate the in vitro findings with the in vivo imaging data from an integrin αvβ3/αvβ5-targeted radiotracer. The results from this study clearly showed that the FITC-conjugated cyclic RGD peptides (particularly FITC-3P-RGD2 and FITC-Galacto-RGD2) are useful fluorescent probes for assaying relative integrin αvβ3/αvβ5 expression levels in tumor tissues.

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High expression of integrin αvβ3 enables uptake of targeted fluorescent probes into ovarian cancer cells and tumors.

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High expression of integrin αvβ3 enables uptake of targeted fluorescent probes into ovarian cancer cells and tumors.

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