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

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.

[1]  F. Kiessling,et al.  Functional and molecular ultrasound imaging: concepts and contrast agents. , 2009, Current medicinal chemistry.

[2]  M. Sekine,et al.  Vascular Endothelial Growth Factor Mediates Intracrine Survival in Human Breast Carcinoma Cells through Internally Expressed VEGFR1/FLT1 , 2007, PLoS medicine.

[3]  Aaron Fenster,et al.  Functional neoangiogenesis imaging of genetically engineered mouse prostate cancer using three-dimensional power Doppler ultrasound. , 2007, Cancer research.

[4]  T. Bettinger,et al.  Gene therapy progress and prospects: Ultrasound for gene transfer , 2007, Gene Therapy.

[5]  Rolf A. Brekken,et al.  Monitoring Response to Anticancer Therapy by Targeting Microbubbles to Tumor Vasculature , 2007, Clinical Cancer Research.

[6]  H. Klocker,et al.  Microbubble-enhanced ultrasound to deliver an antisense oligodeoxynucleotide targeting the human androgen receptor into prostate tumours , 2006, The Journal of Steroid Biochemistry and Molecular Biology.

[7]  Raffi Bekeredjian,et al.  Efficient gene delivery to pancreatic islets with ultrasonic microbubble destruction technology. , 2006, Proceedings of the National Academy of Sciences of the United States of America.

[8]  Alexander L. Klibanov,et al.  Microbubble Contrast Agents: Targeted Ultrasound Imaging and Ultrasound-Assisted Drug-Delivery Applications , 2006, Investigative radiology.

[9]  E. Shimoni,et al.  Therapeutic ultrasound-mediated DNA to cell and nucleus: bioeffects revealed by confocal and atomic force microscopy , 2006, Gene Therapy.

[10]  A. Fenster,et al.  Establishment of a Serum Tumor Marker for Preclinical Trials of Mouse Prostate Cancer Models , 2005, Clinical Cancer Research.

[11]  Aaron Fenster,et al.  A new three-dimensional ultrasound microimaging technology for preclinical studies using a transgenic prostate cancer mouse model. , 2005, Cancer research.

[12]  S. Kaul,et al.  Assessment of Endogenous and Therapeutic Arteriogenesis by Contrast Ultrasound Molecular Imaging of Integrin Expression , 2005, Circulation.

[13]  Tso‐Hsiao Chen,et al.  Ultrasound-microbubble-mediated gene transfer of inducible Smad7 blocks transforming growth factor-beta signaling and fibrosis in rat remnant kidney. , 2005, The American journal of pathology.

[14]  Guojun Wu,et al.  A novel knock-in prostate cancer model demonstrates biology similar to that of human prostate cancer and suitable for preclinical studies. , 2005, Molecular therapy : the journal of the American Society of Gene Therapy.

[15]  M. Moussa,et al.  Knockin of SV40 Tag oncogene in a mouse adenocarcinoma of the prostate model demonstrates advantageous features over the transgenic model , 2005, Oncogene.

[16]  William R Wagner,et al.  Ultrasonic imaging of tumor angiogenesis using contrast microbubbles targeted via the tumor-binding peptide arginine-arginine-leucine. , 2005, Cancer research.

[17]  D. Hicklin,et al.  Elevated Flk1 (Vascular Endothelial Growth Factor Receptor 2) Signaling Mediates Enhanced Angiogenesis in β3-Integrin–Deficient Mice , 2004, Cancer Research.

[18]  T. Ratliff.  Prostate Pathology of Genetically Engineered Mice: Definitions and Classification. The Consensus Report From the Bar Harbor Meeting of the Mouse Models of Human Cancer Consortium Prostate Pathology Committee , 2004 .

[19]  J. Wood,et al.  Targeting Vascular Endothelial Growth Factor (VEGF) for Anti-tumor Therapy, by Anti-VEGF Neutralizing Monoclonal Antibodies or by VEGF Receptor Tyrosine-kinase Inhibitors , 2004, Cancer and Metastasis Reviews.

[20]  Sanjiv Kaul,et al.  Targeted tissue transfection with ultrasound destruction of plasmid-bearing cationic microbubbles. , 2003, Ultrasound in medicine & biology.

[21]  J. Chin,et al.  Prostate targeting: PSP94 gene promoter/enhancer region directed prostate tissue-specific expression in a transgenic mouse prostate cancer model , 2002, Gene Therapy.

[22]  M. Shen,et al.  Mouse models of prostate carcinogenesis. , 2002, Trends in genetics : TIG.

[23]  N. Greenberg,et al.  Autochthonous mouse models for prostate cancer: past, present and future. , 2001, Seminars in cancer biology.

[24]  J. Simons,et al.  Angiogenesis and prostate cancer: identification of a molecular progression switch. , 2001, Cancer research.

[25]  Jun Yamashita,et al.  Flk1-positive cells derived from embryonic stem cells serve as vascular progenitors , 2000, Nature.

[26]  G. Breier,et al.  Tumor endothelium-specific transgene expression directed by vascular endothelial growth factor receptor-2 (Flk-1) promoter/enhancer sequences. , 2000, Cancer research.

[27]  T. Nelson,et al.  Three-dimensional ultrasound imaging. , 1998, Ultrasound in medicine & biology.

[28]  R. Matusik,et al.  Prostate cancer in a transgenic mouse. , 1995, Proceedings of the National Academy of Sciences of the United States of America.

[29]  Margaret J. Cook,et al.  The anatomy of the laboratory mouse , 1965 .