F the highly metastatic K7M2 osteosarcoma cells [27]. Strikingly, Autophagy silencing FHL2 markedly reduced cell migration compared to control cells (Fig. 4A, B). In direct support of this finding, FHL2 silencing in K7M2 cells markedly decreased cell wounding compared to control cells (Fig. 4C, D). Given the 
large impact of FHL2 silencing on K7M2 migration, we analyzed whether FHL2 silencing may also reduce bone tumor cell invasion. We found that inhibitor Matrigel invasion was markedly reduced in shFHL2 transduced K7M2 cells compared to control cells (Fig. 4E, F). Taken together, these data show that silencing FHL2 reduces murine tumor cell invasion and migration in vitro.Osteosarcoma development arises in large part from deregulated cell growth [28]. We therefore investigated whether the inhibition of tumor growth induced by FHL2 silencing is related to decreased cancer cell replication. Analysis of cell replication using Ki67 immunostaining showed that FHL2 silencing decreased the number of Ki67-positive cells (Fig. 5C). Quantification revealed that cell replication was reduced by about 40 in the tumor (Fig. 5D). We also analyzed the effect of FHL2 silencing on osteosarcoma cell death using TUNEL analysis. Consistent with our in vitro data we found reduced apoptosis in tumors derived from shFHL2-infected K7M2 cells compared to tumors derived from control cells (Fig. 5E, F). These data indicate that shRNAtargeted FHL2 expression reduced tumor growth through a decreased cell replication and despite a slight reduction of apoptosis in murine osteosarcoma cells. We next analysed whether FHL2 silencing impacted Wnt responsive genes, as found in vitro (Fig. 2H). As shown in Fig. 5G, a quantitative PCR analysis of RNA isolated from the tumors revealed that FHL2 silencing markedly 18055761 reduced Wnt5a and Wnt10b mRNA level of expression. These results indicate that FHL2 silencing reduces Wnt family proteins expression and impacts Wnt signaling in murine osteosarcoma tumors in vivo. Because lung metastasis is a major clinical issue in osteosarcoma, we investigated whether FHL2 silencing may impact osteosarcoma cell invasiveness in mice. As shown in Fig. 6A, mice injected with shFHL2-infected K7M2 cells developed less lung metastasis than mice injected with shControl-K7M2 cells. Both the number and the surface of the lung metastasis were markedly reduced by FHL2 silencing (Fig. 6 B, C). Overall, the data indicate that FHL2 is overexpressed in osteosarcoma and demonstrate that silencing FHL2 reduces Wnt signaling and decrease osteosarcoma cell growth, invasiveness and tumorigenesis in vivo (Fig. 6D).DiscussionIn this study, we determined the role of the multifunctional protein FHL2 in primary bone cancer growth and tumorigenesis in vitro and in vivo. We first investigated whether FHL2 expression is deregulated in bone tumor cells. Our data indicate that FHL2 is expressed above normal in several human osteosarcoma cell lines and in the aggressive K7M2 murine osteosarcoma cells. Other studies have reported variable FHL2 gene expression in human soft tissue cancers, depending on the cell type. Notably, FHL2 was found to be increased in breast cancer [29], glioma [30], lung cancer [31], colon carcinoma [32] and gastrointestinal cancer [33] compared to normal tissues. In contrast, FHL2 was found to be down-regulated in rhabdomyosarcomas [14] and in prostate cancer [34]. The variable expression of FHL2 in cancer cells is likely related to its distinct roles depending on the ce.F the highly metastatic K7M2 osteosarcoma cells [27]. Strikingly, silencing FHL2 markedly reduced cell migration compared to control cells (Fig. 4A, B). In direct support of this finding, FHL2 silencing in K7M2 cells markedly decreased cell wounding compared to control cells (Fig. 4C, D). Given the large impact of FHL2 silencing on K7M2 migration, we analyzed whether FHL2 silencing may also reduce bone tumor cell invasion. We found that Matrigel invasion was markedly reduced in shFHL2 transduced K7M2 cells compared to control cells (Fig. 4E, F). Taken together, these data show that silencing FHL2 reduces murine tumor cell invasion and migration in vitro.Osteosarcoma development arises in large part from deregulated cell growth [28]. We therefore investigated whether the inhibition of tumor growth induced by FHL2 silencing is related to decreased cancer cell replication. Analysis of cell replication using Ki67 immunostaining showed that FHL2 silencing decreased the number of Ki67-positive cells (Fig. 5C). Quantification revealed that cell replication was reduced by about 40 in the tumor (Fig. 5D). We also analyzed the effect of FHL2 silencing on osteosarcoma cell death using TUNEL analysis. Consistent with our in vitro data we found reduced apoptosis in tumors derived from shFHL2-infected K7M2 cells compared to tumors derived from control cells (Fig. 5E, F). These data indicate that shRNAtargeted FHL2 
expression reduced tumor growth through a decreased cell replication and despite a slight reduction of apoptosis in murine osteosarcoma cells. We next analysed whether FHL2 silencing impacted Wnt responsive genes, as found in vitro (Fig. 2H). As shown in Fig. 5G, a quantitative PCR analysis of RNA isolated from the tumors revealed that FHL2 silencing markedly 18055761 reduced Wnt5a and Wnt10b mRNA level of expression. These results indicate that FHL2 silencing reduces Wnt family proteins expression and impacts Wnt signaling in murine osteosarcoma tumors in vivo. Because lung metastasis is a major clinical issue in osteosarcoma, we investigated whether FHL2 silencing may impact osteosarcoma cell invasiveness in mice. As shown in Fig. 6A, mice injected with shFHL2-infected K7M2 cells developed less lung metastasis than mice injected with shControl-K7M2 cells. Both the number and the surface of the lung metastasis were markedly reduced by FHL2 silencing (Fig. 6 B, C). Overall, the data indicate that FHL2 is overexpressed in osteosarcoma and demonstrate that silencing FHL2 reduces Wnt signaling and decrease osteosarcoma cell growth, invasiveness and tumorigenesis in vivo (Fig. 6D).DiscussionIn this study, we determined the role of the multifunctional protein FHL2 in primary bone cancer growth and tumorigenesis in vitro and in vivo. We first investigated whether FHL2 expression is deregulated in bone tumor cells. Our data indicate that FHL2 is expressed above normal in several human osteosarcoma cell lines and in the aggressive K7M2 murine osteosarcoma cells. Other studies have reported variable FHL2 gene expression in human soft tissue cancers, depending on the cell type. Notably, FHL2 was found to be increased in breast cancer [29], glioma [30], lung cancer [31], colon carcinoma [32] and gastrointestinal cancer [33] compared to normal tissues. In contrast, FHL2 was found to be down-regulated in rhabdomyosarcomas [14] and in prostate cancer [34]. The variable expression of FHL2 in cancer cells is likely related to its distinct roles depending on the ce.
