Long residence time of ultrasound microbubbles targeted to integrin in murine tumor model.
OBJECTIVE
The aim of this study was to evaluate the intratumoral residence time of microbubbles (MBs) targeted to alpha(v)beta(3) integrin expressed in the endothelial cells of mice during the process of tumor angiogenesis.


METHODS
For the preparation of MBs, decafluorobutane gas was sonically dispersed in phosphate buffer saline containing L-A-phosphatidylcholine-distearoyl, polyethylene glycol 40 stearate, and 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[biotinyl(polyethylene glycol)2000] in a 77:15:8 molar ratio. Avidin-fluorescein isothiocyanate and biotin-cyclic arginine-glycine-aspartate-D-tyrosine-lysine (cRGD) or biotin-alanine-glycine-aspartate (AGD) conjugates were added to the reaction mixture. Adhesion testing of the targeting MBs was performed for the MS-1 cell line expressing alpha(v)beta(3) integrin in vitro. The in vivo acoustic properties of the MBs were assessed by clinical ultrasound on the HT1080 fibrosarcoma model (n = 8) for 1 hour. Cryosections were stained with hematoxylin and eosin and by immunohistochemical staining to identify expression of alpha(v)beta(3) integrin in the HT1080 tumor.


RESULTS
The adherence of the MBs conjugated to cRGD was significantly greater than the adherence of the MBs conjugated to biotin-AGD (P < .01) for the MS-1 endothelial cell line. The acoustic enhancement on ultrasound was observed as a stable imaging window until 1 hour after injection of the MB conjugates in the mice. The MBs targeted via cRGD preferentially adhered to the vascular endothelium of the HT-1080 tumors. The findings of ultrasound imaging were correlated with immunohistochemical findings for the expression of alpha(v)beta(3) integrin on the vascular endothelium of the tumors.


CONCLUSIONS
The prepared MBs conjugated with cRGD demonstrated a sufficient residence time to attach to the target integrin of tumor tissues. This finding suggests that the MBs are a potential molecular contrast agent that enables characterization of tumor angiogenesis and the monitoring of antitumor and antiangiogenic therapy.
Jun
Hong Young
HY
Department of Radiology and the Institute for Radiological Imaging Science, Wonkwang University, Iksan, Jeonbuk 570-711, South Korea.
Park
Seong Hoon
SH
Kim
Hun Soo
HS
Yoon
Kwon-Ha
KH
D000818:Animals; D045744:Cell Line, Tumor; D003287:Contrast Media / Q000493:pharmacokinetics*; D004195:Disease Models, Animal; D005354:Fibrosarcoma / Q000098:blood supply / Q000000981:diagnostic imaging* / Q000378:metabolism*; D006801:Humans; D039302:Integrin alphaVbeta3 / Q000378:metabolism*; D008297:Male; D008657:Metabolic Clearance Rate; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D045423:Microbubbles; D009389:Neovascularization, Pathologic / Q000000981:diagnostic imaging* / Q000378:metabolism*; D014463:Ultrasonography
D003287:Contrast Media; D039302:Integrin alphaVbeta3