Slit2 promotes tumor growth and invasion in chemically induced skin carcinogenesis

Abstract

Slit, a neuronal guidance cue, binds to Roundabout (Robo) receptors to modulate neuronal, leukocytic, and endothelial migration. Slit has been reported to have an important effect on tumor growth and metastasis. In the current study, we evaluated the role of Slit2 in skin tumor growth and invasion in mice using a two-step chemical carcinogenesis protocol. We found that Slit2 expression correlated with the loss of basement membrane in the samples of human skin squamous cell carcinoma at different stages of disease progression. Slit2-Tg mice developed significantly more skin tumors than wild-type mice. Furthermore, the skin tumors that occurred in Slit2-Tg mice were significantly larger than those in the wild-type mice 10 weeks after 7,12-dimethylbenz[a]anthracene initiation until the end of the experiment. We also found that pathological development of the wild-type mice was delayed compared with that of Slit2-Tg mice. To further investigate the mechanism of increasing tumors in Slit2-Tg mice, we analyzed the expression of 5-bromo-2 0 -deoxyuridine (BrdU) in mouse skin lesions and found that the number of BrdU-positive cells and microvessel density in skin lesions were significantly higher in Slit2-Tg mice than in wild-type mice. Histological staining of PAS and type IV collagen and the colocalization of Slit2 and type IV collagen demonstrated varying degrees of loss of the basement membrane in the skin lesions from Slit2-Tg mice that were at the stage of carcinoma in situ. However, the basement membrane was well defined in the wild-type mice. In addition, MMP2, but not MMP9, was upregulated in the skin tissue of Slit2-Tg mice. Interruption of Slit2-Robo1 signaling by the antibody R5 significantly repressed the invasive capability of the squamous cell carcinoma cell line A431. Taken together, our findings reveal that Slit2 promotes DMBA/TPA-induced skin tumorigenesis by increasing cell proliferation, microvessel density, and invasive behavior of cutaneous squamous cell carcinoma, along with loss of basement membrane, by upregulation of MMP2 expression. Skin cancer is one of the most common malignant tumors. Approximately 2 to 3 million cases of nonmelanoma skin cancer occur annually worldwide, and its incidence has been rising rapidly over the past several decades. 1 Skin cancer develops through a multistage process that includes initiation, promotion, and progression, as shown in experimental animal models. 2 The two-stage murine skin carcinogenesis model, which comprises two distinctly separate stages (initiation and promotion), is one of the most well-established in vivo models of experimental carcinogenesis. After 7, anthracene (DMBA) initiation, repeated applications of the tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) promote papillomas and eventually carcinomas. 3 Slit, a member of neuronal guidance cues, has been implicated to play an important role in tumor progression. 4 The Slit family consists of three members (Slit1, Slit2, and Slit3) that are expressed in the nervous system, whereas Slit...

Effects of Slit3 silencing on the invasive ability of lung carcinoma A549 cells

“…Although a number of studies have explored the roles of Slit2 in tumor progression, relatively little progress has been made in defining the effects of Slit3 on tumors. In contrast to Slit2, which was reported to be upregulated in various tumors (18,20), few results concerning Slit3 upregulation in tumor tissues have been reported. Although microarray analysis revealed Slit3 upregulation in separated invasive hepatocellular carcinoma cells, no evidence of protein level upregulation has been provided (37).…”

“…The prometastatic or antimetastatic effects of Slit are likely associated with MMP expression or protein activities. Qi et al recently reported upregulation of MMP2, yet not MMP9 in skin tissue of Slit2-transgenic mice and proposed that MMP2 upregulation accounted for loss of the basement membrane in Slit2-transgenic mice, indicating a positive correlation between Slit2 and MMP2 expression (20). However, Prasad et al reported that Slit2 inhibits the CXCL12-induced activities of MMP2 and MMP9 in breast cancer cells (43).…”

“…Although most results support the inhibitory effects of Slit2 on tumor growth and metastasis, the role of Slit2 in growth and metastasis is still controversial. Several studies have validated a stimulative role of Slit2 on tumor growth and metastasis (20)(21)(22), and this discrepancy reflects the complexity of Slit/Robo signaling in different types of cancers.…”

Slit2 and Robo1 induce opposing effects on metastasis of hepatocellular carcinoma Sk-hep-1 cells

“…was upregulated in chemically-induced skin tumors (17). Moreover, a Robo1 blocking monoclonal antibody inhibited the activity of MMP2 and MMP9 in tongue cancer cells (18).…”

Slit2/Robo1 signaling promotes intestinal tumorigenesis through Src-mediated activation of the Wnt/β-catenin pathway

“…Previous reports have indicated a clear association between the Slit2 expression and tumor invasion in several cancer types, including CRC, glioma, and skin cancer [ 6 - 8 , 26 , 27 ]. Our study has confirmed that increased Slit2/Robo1 signaling may exert an oncogenic role during the early initiation of intestinal tumorigenesis.…”