6B,C). Furthermore, although imatinib mesylate treatment had little effect on the size of primary SC tumors, it significantly suppressed lung metastasis in primary selleck kinase inhibitor tumors (Fig. 6C). These data suggest that CD90+ cells are not only metastatic to the distant organ, but also help the metastasis of CD90− cells, including EpCAM+ cells, which originally have no distant metastatic capacity.
Our data further suggest that imatinib mesylate can inhibit distant organ metastasis by suppressing CD90+ metastatic CSCs, albeit with little effect on EpCAM+ tumorigenic epithelial stem-like CSCs. To explore the potential mechanism of how CD90+ cells dictate the metastasis of EpCAM+ cells, we utilized coculture systems and time-lapse image analysis. Wound-healing analysis clearly indicated that motility of HuH7 cells was enhanced when HLF cells were cocultured, and this effect was abolished by imatinib mesylate treatment (Fig. 6D; see Supporting Videos 1-3). HLF cells abundantly expressed TGFB1, compared with HuH7 cells, and its expression was dramatically suppressed by imatinib mesylate treatment (Fig. 6E). Mothers against decapentaplegic homolog 3 (Smad3) phosphorylation was augmented in
HuH7 cells when cocultured with HLF cells, and this effect was attenuated when cocultured with HLF cells pretreated with imatinib mesylate. Taken together, our data suggest that liver CSCs are not a single entity. Liver CSCs defined by different markers show selleckchem unique features of tumorigenicity/metastasis with phenotypes closely associated with committed liver lineages.
These distinct CSCs may collaborate to enhance tumorigenicity and metastasis of HCCs. The current investigation demonstrates that CSC marker expression status may be a key determinant of cancer phenotypes, in terms of metastatic propensity and chemosensitivity, to certain molecularly targeted therapies. EpCAM appears to be an epithelial tumorigenic CSC marker, whereas CD90 seems to be a mesenchymal metastatic CSC marker associated with expression Histidine ammonia-lyase of c-Kit and chemosensitivity to imatinib mesylate. Imatinib mesylate may be effective in inhibiting metastasis, but has little effect on primary EpCAM+ HCC cell growth. We investigated the frequency of three CSC markers (EpCAM, CD90, and CD133) in 15 primary HCCs with a confirmed cell viability of ≥70% and found that three HCCs contained CD133+ cells, seven HCCs contained EpCAM+ cells, and all HCCs contained CD90+ cells. Among them, we confirmed the perpetuation of CD133+ cells derived from three HCCs (P7, P12, and P14; data not shown), EpCAM+ cells derived from four HCCs (P4, P7, P13, and P14), and CD90+ cells derived from two HCCs (P12 and P15). Recent studies showed that at least 8 of 21 HCCs (38%)4 and 13 of 13 HCCs (100%)5 contained tumorigenic CD133+ or CD90+ CSCs, respectively.