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ORIGINAL RESEARCH ARTICLE

Doxycycline Influences Microcirculation Patterns in B16 Melanoma

Baocun Sun^*,,1, Shiwu Zhang^*,2,1, Danfang Zhang^*, Xiaojin Yin, Sen Wang, Yanjun Gu^* and Yalei Wang^*

^* Department of Pathology, Tianjin Cancer Hospital, Tianjin Medical University, Tianjin 300060, China; Department of Pathology, Tianjin Medical University, Tianjin 300070, China; and Jiangsu Simcere Pharmaceutical Co. Ltd., Nanjing 210000, China

To whom requests for reprints should be addressed at ² Department of Pathology, Tianjin Cancer Hospital, Tianjin Medical University, Tianjin 300060, PR China. E-mail: zhangshiwu666{at}yahoo.com.cn

To examine the effects of doxycycline on invasion-related protein expression and proliferation of melanoma cells and to evaluate its effect on microcirculation patterns in melanoma, we injected murine melanoma B16 cell suspensions into the groin areas of C57BL/6 mice that were randomly divided into treatment and control groups. Eight days after tumor cell injection, we administered doxycycline intraperitoneally (ip) at a dose of 0.15 mg/g/day in the treatment group and administered a physiological saline solution to the control group. Animals were sacrificed on Day 22, and we removed and weighed tumor masses and counted the numbers of vasculogenic mimicry (VM) and endothelium-dependent vessels. Immunohistochemical staining was used to analyze the expression of matrix metalloproteinase-2 (MMP-2), matrix metalloproteinase-9 (MMP-9), vascular endothelial growth factor (VEGF), and proliferating cell nuclear antigen (PCNA). We prepared protein extracts of the tumors, and we examined the activity of MMP-2 and MMP-9 in different groups by gelatin zymography. Real-time polymerase chain reaction (PCR) was used to detect MMP-2 and MMP-9 mRNA level in the fresh tumor tissue. Doxycycline treatment partly suppressed the growth of engrafted B16 melanoma, with an inhibition rate of 35.63%. There were more VM and endothelium-dependent vessels in the control group than in the treatment group. The expression level of MMP-2 and MMP-9 in the treatment group was lower than that in the control group (P < 0.01, P < 0.05). Compared with the control group, VEGF expression was increased with doxycycline treatment. The enzyme activities of MMP-9, active-MMP-2, and MMP-2/pro-MMP-2 in the treatment group were lower than those in the control group (P < 0.01). MMP-2 and MMP-9 mRNA levels in the treatment group were also lower than those in the control group were. Doxycycline inhibits the growth of engrafted melanoma and results in reduced expression of MMP-2, MMP-9, and VM formations.

Key Words: melanoma • doxycycline • vasculogenic mimicry • matrix metalloproteinases • endothelium-dependent vessels • angiogenesis