OBJECTIVETo investigate the effect of high-intensity focused ultrasound (HIFU) on tumor metastasis in mouse model bearing melanoma xenograft.

METHODSMice bearing murine melanoma B16-F10 cell xenograft were randomized for sham-HIFU or HIFU exposure when the tumors grew to a maximum diameter of 7-10 mm, and the tumor size was measured every 3 days. The cumulative survival rate of the mice and tumor metastasis rate were calculated, and the circulating melanoma cells were detected using qRT-PCR. At 14 days after HIFU treatment, B16-F10 cells were retransplanted via the tail vein and the pulmonary metastatic nodules were counted.

RESULTSThe median survival time of the mice was 19.00 days (95% CI 17.14-20.86 days) in the sham group and 26.00 days (95%CI 24.76-27.25 days) in HIFU group. The cumulative survival rate in the HIFU group was significantly higher than that in sham-HIFU group (P<0.01), and the tumor size was significantly smaller in HIFU group at 20, 23, and 26 days after HIFU treatment (P<0.05). Compared with the sham-HIFU group, HIFU group had significantly lower levels of MAGE-A3, MART1 and PAX3 at 7 days after HIFU (P<0.05) with still lower MAGE-A3 level at 14 days (P<0.05). HIFU group showed a significantly smaller number of pulmonary metastatic nodules following tumor cell retransplantation than in sham-HIFU group (P<0.01) with a metastasis inhibition rate of 42.4%.

CONCLUSIONHIFU treatment can inhibit tumor metastasis in melanoma-bearing mice possibly by reducing tumor cell detachment from the primary tumor site and suppressing colonization of the circulating melanoma cells.