OBJECTIVETo investigate the correlation of contrast-enhanced pattern with expression of hypoxia inducible factor-1α (HIF-1α) and microvessel density (MVD) in mice breast cancer.

METHODSA total of 22 mice were implanted with breast cancer cells (Ca761) subcutanously in the thigh. The tumors were examined with conventional ultrasound and contrast-enhanced ultrasound (CEUS) on days 4,6,7,8,9,10,and 11 after implantation and then sacrificed. Three or four mice were included each time. Expressions of HIF-1α and MVD in cancer tissues were detected immunohistochemically. Correlation of contrast-enhanced patterns with expression of HIF-1α and MVD in breast cancer was analyzed.

RESULTSMice were divided into 3 groups according to the tumor volume:group 1 (volume<0.05 cm(3),n=5),group 2 (volume 0.05-0.75 cm(3),n=9),and group 3 (volume>0.75 cm(3),n=8). The CEUS pattern was different in different groups:four mice in group 1 presented as type 1 (peripheral ring enhancement with no enhancement within the tumor) and 1 case presented as type 2 (peripheral ring enhancement with deep penetration). Most mice in group 2 presented as type 3 (homogeneous or heterogeneous enhancement in the whole tumor,n=5). In group 3,most mice presented as type 4 (peripheral ring enhancement with focal nodular enhancement within the tumor,n=7). Contrast-enhanced pattern was significantly different in different volume groups (P<0.01). Enhanced pattern (type 1-4) was closely correlated with tumor volume (r=0.841,P<0.05). The expression of HIF-1α was negatively correlated with enhanced patterns (type 1-4) (r=-0.596,P＝0.003),but not with tumor volume (P>0.05). There was no significant difference in MVD values between different enhanced patterns (type 1-4),and there was no correlation between the MVD and tumor volumes (P>0.05).

CONCLUSIONCEUS can be used as a noninvasive tool to monitor tumor angiogenesis in tumor and the enhanced patterns may reflect the expression of HIF-1α inside the tumor.