The contribution of E-selectin to metastasis was studied in a cytokine-induced experimental lung metastasis model [40]

The contribution of E-selectin to metastasis was studied in a cytokine-induced experimental lung metastasis model [40]. cells. == Electronic supplementary material == The online version of this article (doi:10.1007/s12307-010-0043-6) contains supplementary material, which is available to authorized users. Keywords:Endothelium, Selectins, Metastasis, Carcinomas, Tumor microenvironment, Metastatic microenvironment == Introduction == The formation of metastatic lesions remains the major cause for cancer-related morbidity and mortality. Metastasis to vital organs such as liver or lungs occurs through hematogenous dissemination that encompasses multiple steps including intravasation, transportation and survival in circulation, extravasation and colonization of distant tissues [1,2]. In general, metastasis is an inefficient process, whereas tissue colonization is considered to be the rate-limiting step [3,4]. Tumor cells with a genetic make-up that allows them to adapt the new environment will successfully colonize distant organs [1,5,6]. Metastatic tumor VCA-2 cells interact with the local microenvironment, thereby forming a metastatic niche permissive for the establishment of metastatic lesions [6,7]. Depending on the target tissue, tumor cells exhibit a distinct set of properties required for metastasis [1,6,8]. Mammary carcinoma cells adopt and activate different molecular pathways depending on the colonized tissue, e.g. bone or lungs [911]. While the discontinuous endothelial lining of the hepatic or bone vasculature allows tumor cells to exit from the circulation rather rapidly, anatomy of the lung with C75 a tight capillary bed seems to be an especially hostile environment for metastasizing tumor cells [12]. During hematogenous phase, tumor cell interactions with blood elements (cells and soluble factors) and the pulmonary microvascular endothelium are critical for metastasis [6,1316]. Specifically, the interaction of platelets with tumor cells enhances the tumor cell survival within the metastatic, pulmonary microenvironment [1719]. The recruitment of leukocytes, mainly myeloid cells, to metastasizing tumor cells was shown to promote lung colonization in mice [2023]. Metastasis-promoting interactions of tumor cells with platelets and leukocytes were shown to be initiated by P- and L-selectins [19,21,23]. The absence of P- and/or L-selectin as well as the blockage of any of these selectins led to a significant attenuation of metastasis [19,21]. Furthermore, the effect of heparin on metastasis is to a large extent ascribed to the inhibition of P- and L-selectin mediated interactions [2426]. E-selectin is present only on activated endothelial cells from various vascular beds [27]. Several studies demonstrated that the hepatic sinusoidal endothelium is activated during the initial phase of metastatic liver colonization [2830]. This endothelial activation was associated with an upregulation of C75 cell adhesion molecules including E-selectin and VCAM-1, that was similar to a local inflammatory reaction [28]. Upregulation of E-selectin expression in the liver was associated with enhanced formation of C75 metastasis [31,32]. In this work we aimed to characterize the expression and the function of all three selectins (E-, P-, and L-) during lung colonization in an experimental metastasis model. == Material and Methods == == Cell Culture == MC-38 and MC-38GFP murine colon adenocarcinoma cells were grown as described previously [19]. Human colon carcinoma cells, LS180 tumor cells were grown in DMEM medium containing 10% FCS. Hybridomas producing L-selectin antibody C75 (MEL-14 clone from ATCC) were grown and C75 the antibody purified as described previously [21]. == Experimental Metastasis == LS180 tumor cells (350,000 cells, passage 24) were injected into the lateral tail vein of Rag2 deficient (Rag2-/-) or selectin deficient mice in a Rag2 background (Esel-/-/Rag2-/-; Psel-/-/Rag2-/-; or Lsel -/-/Rag2-/-). Mice (groups of 58) were euthanized 6 weeks later, and.