Expression of chemokines CCL5 and CCL11 by smooth muscle tumor cells of the uterus and its possible role in the recruitment of mast cells.

Objective: Smooth muscle tumors of uterus have been reported to contain considerable number of mast cells, especially cellular leiomyoma. However, to our knowledge the mechanism by which mast cells increased in them is not known. The purpose of this study was to reveal the different mast cell subsets in smooth muscle tumors of uterus and to investigate the mechanism of local increase of mast cells.

Methods: Tissue sections from 85 uterine smooth muscle tumors were studied using immunohistochemical double labeling techniques, including 40 cases of ordinary leiomyomas, 30 cases of cellular leiomyomas and 15 cases of leiomyosarcomas. The sections were double immunostained for mast cell tryptase and chymase, mast cell tryptase and ki-67, mast cell tryptase and chemokines (i.e., CCL2, CCL5, CCL11, TGFbeta), as well as tryptase and CCR3.

Results: MC(TC)-type of mast cells was the predominant type in ordinary leiomyoma and cellular leiomyoma, whereas MC(T)-type was seldom found in them. There was no MC(C) in smooth muscle tumors. The total intratumoral number of mast cells in cellular leiomyoma group was significantly higher than that in both leiomyosarcoma and ordinary leiomyoma (P<0.01). Mast cells proliferation was rarely detected in smooth muscle tumors, as revealed by constant negative labeling of the proliferation marker Ki-67 in mast cells. Almost all mast cells (tryptase positive) in smooth muscle tumors were also CCL2, CCL5, CCL11 and TGFbeta positive. Expressions of CCL5 and CCL11 in tumor cells in cellular leiomyoma were all significantly higher than that in both ordinary leiomyoma and leiomyosarcoma (P<0.01). While the expression of TGFbeta in tumor cells in cellular leiomyoma was not significantly different from that in ordinary leiomyoma, expression of CCL2 was not observed in smooth muscle tumor cells. There were positive correlations between CCL5 and the number of mast cells (r(s)=0.801, P<0.01) and between CCL11 and the number of mast cells (r(s)=0.744, P<0.01) in smooth muscle tumors as well. The vast majority of the mast cells in cellular leiomyoma were CCR3 positive.

Conclusions: Using the monoclonal anti-mast cell tryptase antibody could detect all mast cells in smooth muscle tumor. The increased intratumoral mast cell counts in cellular leiomyoma might be the result of mast cells recruitment from the peripheral blood rather than local mast cells proliferation. CCL5 and CCL11, which are expressed by smooth muscle tumor cells, are possibly responsible for the recruitment of mast cells in uterine cellular leiomyoma. Whether they combine to CCR3 expressed by mast cells need further study.