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Experimental study on residual tumor angiogenesis after cryoablation.

OBJECTIVE
To explore the mechanism and significance of tumor angiogenesis by observing changes of micro-vessel density (MVD) and expression of vascular endothelial growth factor (VEGF) in residual tumor tissues after cryoablation.


MATERIALS AND METHODS
A total of 18 nude mice xenograft models with transplanted lung adenocarcinoma cell line A549 were established and randomly divided into 3 groups when the maximum diameter of tumor reached 1 cm: control, cisplatin (DDP) and cryoablation. The nude mice were sacrificed after 21-d cryoablation to obtain the tumor tissues. Then immunohistochemistry was applied to determine MVD and the expression of VEGF in tumor tissues.


RESULTS
The tumor volumes of control group, DDP group and cryoablation group were 1.48 ± 0.14 cm3, 1.03 ± 0.12 cm3 and 0.99 ± 0.06 cm3 respectively and the differences were significant (P < 0.01), whereas MVD values were 21.1 ± 0.86, 24.7 ± 0.72 and 29.2 ± 0.96 (P < 0.01) and the positive expression rates of VEGF were 36.2 ± 1.72%, 39.0 ± 1.79% and 50.8 ± 2.14% (P < 0.01), respectively, showing that MVD was proportional to the positive expression of VEGF (r = 0.928, P < 0.01).


CONCLUSIONS
Cryoablation can effectively inhibit tumor growth, but tumor angiogenesis significantly increases in residual tumors, with high expression of VEGF playing an important role in the residual tumor angiogenesis.