Molecular Targeted Enhanced Ultrasound Imaging of Flk1 Reveals Diagnosis and Prognosis Potential in a Genetically Engineered Mouse Prostate Cancer Model

Abstract

Molecular imaging techniques used to detect the initiation of disease have the potential to provide the best opportunity for early treatment and cure. This report aimed at testing the possibility that Flk1+ (vascular endothelial growth factor receptor 2), a crucial angiogenesis factor of most tumor cells, could be a molecular targeted imaging marker for the diagnosis and prognosis of cancer. We performed Flk1-targeted microbubble-enhanced ultrasound (US) imaging of prostate cancer in a genetically engineered mouse model with normal-appearing intact US (negative) prostates and with three different tumor sizes (small, medium, and large). Higher levels of Flk1+ molecular signals were identified in the intact US (negative) prostate group by US-targeted imaging and immunohistochemical analysis. The increase in Flk1+ expression occurred prior to the angiogenesis switch-on phase and vascularity peak. After this peak accumulation stage of Flk1+ molecules, lower and stabilized levels of Flk1+ signals were maintained together with tumor growth from small, to medium, to large size. In a longitudinal observation in a subset (n = 5) of mice with established tumors, elevated Flk1+ signals were observed in tissues surrounding the prostate cancer, for example, the ipsilateral boundary zones between two developing tumor lobes, new tumor blood vessel recruits, the urethra border, and the pelvic node basin. The potential of Flk1-targeted US imaging as a predictive imaging tool was confirmed by correlation studies of three-dimensional US B-mode imaging, gross pathology, and histology analyses. The results of the application in a genetically engineered mouse model with prostate cancer of molecular Flk1-targeted US imaging support the contention that Flk1 can be used as a molecular imaging marker for small tumors undetectable by microimaging and as a molecular diagnostic and prognosis marker for tumor metastasis and progression.

Vascular Endothelial Growth Factor Receptor 2-Specific Microbubbles for Molecular Ultrasound Detection of Prostate Cancer in a Rat Model

“…In these studies, different tumors were used, such as human squamous cell carcinoma, 17 breast cancer, 16 human ovarian cancer, 19 orthotopic pancreatic tumor, 15 angiosarcoma, malignant glioma, 18 and prostate cancer. 46 The present study indicates that target-specific VEGFR2 binding microbubbles can be used for noninvasive in vivo visualization and detection of orthotopic prostate cancer in a rat tumor model. The results show that the specific contrast agent investigated could be of great interest for animal studies on new drugs directed against endothelial receptors.…”

“…In further studies, [15][16][17][18][19]46 it had been shown that molecular US using microbubbles binding to VEGFR2 allow visualization and quantification of angiogenesis and VEGFR2 expression in xenograft tumor models in mice. In these studies, different tumors were used, such as human squamous cell carcinoma, 17 breast cancer, 16 human ovarian cancer, 19 orthotopic pancreatic tumor, 15 angiosarcoma, malignant glioma, 18 and prostate cancer.…”

TRIM59, a novel multiple cancer biomarker for immunohistochemical detection of tumorigenesis

“…As a multiple biomarker associated with epithelium origin (very rarely arisen from mesenchymal tissue, see table 2) TRIM59 may be used as an EMT (epithelium–mesenchymal transition) specific cobiomarker. The TRIM59 antibody may also be used for molecular-targeted imaging as a new diagnostic marker, for example, in the context of targeted microbubble ultrasound destruction technology,23 before the protocol of a serum TRIM59 test can be established.

Strengths and limitations of this study

TRIM59 may be used a novel multiple tumor marker for immunohistochemical detecting early tumorigenesis and could direct a novel strategy for molecular-targeted diagnosis and therapy of cancer.

The work was mostly on human tumor samples by immunohistochemistry.

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“…22). In a transgenic mouse test of TRIM59 upregulation specifically in the prostate, TRIM59 demonstrated full oncogenic activity in directing tumorigenesis and progression to highest-grade CaP 17 23. The signal pathway of TRIM59 may be possibly linked with two large oncogene routes: the Ras/Raf/MEK/ERK/PI3K/AKT and the SV40 Tag/p53/pRB routes 17.…”

An experimental study on the stiffness of size-isolated microbubbles using atomic force microscopy

“…Microbubbles have been widely used as contrast agents to increase the blood backscatter in diagnostic ultrasound imaging [1]–[3]. More recently, it has been shown that microbubbles may also hold great potential for disease treatment, including oxygen delivery to hypoxic tissues [4], drug and gene delivery [5], [6], cavitation-assisted thrombolysis [7] as well as localized and transient opening of the blood–brain barrier (BBB) for targeted drug and gene delivery [8]–[10].…”