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Kazmierczak, Philipp M.; Burton, Neal C.; Keinrath, Georg; Hirner-Eppeneder, Heidrun; Schneider, Moritz J.; Eschbach, Ralf S.; Heimer, Maurice; Solyanik, Olga; Todica, Andrei; Reiser, Maximilian F.; Ricke, Jens; Cyran, Clemens C. (2018): Integrin-targeted quantitative optoacoustic imaging with MRI correlation for monitoring a BRAF/MEK inhibitor combination therapy in a murine model of human melanoma.
In: PLOS One 13(10), e0204930
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Abstract

Purpose To investigate alpha(v)beta(3)-integrin-targeted optoacoustic imaging and MRI for monitoring a BRAF/MEK inhibitor combination therapy in a murine model of human melanoma. Materials and methods Human BRAF V600E-positive melanoma xenograft (A375)-bearing Balb/c nude mice (n = 10) were imaged before (day 0) and after (day 7) a BRAF/MEK inhibitor combination therapy (encorafenib, 1.3 mg/kg/d;binimetinib, 0.6 mg/kg/d, n = 5) or placebo (n = 5), respectively. Optoacoustic imaging was performed on a preclinical system unenhanced and 5 h after i. v. injection of an alpha(v)beta(3)-integrin-targeted fluorescent probe. The alpha(v)beta(3)-integrin-specific tumor signal was derived by spectral unmixing. For morphology-based tumor response assessments, T2w MRI data sets were acquired on a clinical 3 Tesla scanner. The imaging results were validated by multiparametric immunohistochemistry (beta 3 -integrin expression, CD31 -microvascular density, Ki-67 -proliferation). Results The alpha(v)beta(3)-integrin-specific tumor signal was significantly reduced under therapy, showing a unidirectional decline in all animals (from 7.98 +/- 2.22 to 1.67 +/- 1.30;p = 0.043). No significant signal change was observed in the control group (from 6.60 +/- 6.51 to 3.67 +/- 1.93;p = 0.500). Immunohistochemistry revealed a significantly lower integrin expression (beta(3) : 0.20 +/- 0.02 vs. 0.39 +/- 0.05;p = 0.008) and microvascular density (CD31: 119 +/- 15 vs. 292 +/- 49;p = 0.008) in the therapy group. Tumor volumes increased with no significant intergroup difference (therapy: +107 +/- 42 mm(3);control +112 +/- 44mm(3), p = 0.841). In vivo blocking studies with alpha(v)beta(3-)integrin antagonist cilengitide confirmed the target specificity of the fluorescent probe. Conclusions alpha(v)beta(3)-integrin-targeted optoacoustic imaging allowed for the early non-invasive monitoring of a BRAF/MEK inhibitor combination therapy in a murine model of human melanoma, adding molecular information on tumor receptor status to morphology-based tumor response criteria.