4017

LOXL2

lysyl oxidase-like 2;LOXL2;lysyl oxidase-like 2

lysyl oxidase homolog 2|lysyl oxidase related 2|lysyl oxidase-like 2 delta e13|lysyl oxidase-like 2 protein|lysyl oxidase-like protein 2|lysyl oxidase-related protein 2|lysyl oxidase-related protein WS9-14

8p21.3

protein-coding

More than 90% of cancer patient mortality is attributed to metastasis. In this study, we investigated a role for the lysyl oxidase-related enzyme lysyl oxidase-like 2 (LOXL2) in breast cancer metastasis, in both patient samples and in vivo models. Analysis of a published microarray data set revealed that LOXL2 expression is correlated with metastasis and decreased survival in patients with aggressive breast cancer. In immunocompetent or immunocompromised orthotopic and transgenic breast cancer models we showed that genetic, chemical or antibody-mediated inhibition of LOXL2 resulted in decreased metastasis. Mechanistic investigations revealed that LOXL2 promotes invasion by regulating the expression and activity of the extracellular proteins tissue inhibitor of metalloproteinase-1 (TIMP1) and matrix metalloproteinase-9 (MMP9). We found that LOXL2, TIMP1, and MMP9 are coexpressed during mammary gland involution, suggesting they function together in glandular remodeling after weaning. Finally, we found that LOXL2 is highly expressed in the basal/myoepithelial mammary cell lineage, like many other genes that are upregulated in basal-like breast cancers. Our findings highlight the importance of LOXL2 in breast cancer progression and support the development of anti-LOXL2 therapeutics for the treatment of metastatic breast cancer.

Basal-like breast carcinoma is characterized by the expression of basal/myoepithelial markers, undifferentiated phenotype, highly aggressive behaviour and frequent triple negative status (ESR-, PR-, Her2neu-). We have previously shown that epithelial-mesenchymal transition (EMT) occurs in basal-like breast tumours and identified Lysyl-oxidase-like 2 (LOXL2) as an EMT player and poor prognosis marker in squamous cell carcinomas. We now show that LOXL2 mRNA is overexpressed in basal-like human breast carcinomas. Breast carcinoma cell lines with basal-like phenotype show a specific cytoplasmic/perinuclear LOXL2 expression, and this subcellular distribution is significantly associated with distant metastatic incidence in basal-like breast carcinomas. LOXL2 silencing in basal-like carcinoma cells induces a mesenchymal-epithelial transition (MET) associated with a decrease of tumourigenicity and suppression of metastatic potential. Mechanistic studies indicate that LOXL2 maintains the mesenchymal phenotype of basal-like carcinoma cells by a novel mechanism involving transcriptional downregulation of Lgl2 and claudin1 and disorganization of cell polarity and tight junction complexes. Therefore, intracellular LOXL2 is a new candidate marker of basal-like carcinomas and a target to block metastatic dissemination of this aggressive breast tumour subtype.

Prognosis of cancers with lymph node metastasis is known to be very poor; however, it is still controversial whether metastatic potential can be evaluated by expression profiles of primary tumors. Therefore, to address this issue, we compared gene expression profiles of 24 esophageal squamous cell carcinomas (ESCCs) with extensive lymph node metastasis and 11 ESCCs with no metastatic lymph node. However, there was no gene cluster distinguishing these two groups, suggesting that lymph node metastasis-associated genes are varied depending on cases or subgroups. Therefore, we applied a recently developed filtering method (S2N') to identify such genes, and successfully extracted 209 genes associated with node status. Among them, over-expression of CALB1, KRT7/CK7, MUC1 and CEA/CEACAM5 in poor prognostic cases with metastatic lymph nodes was confirmed in two sets of ESCCs by RT-PCR. Each often seemed to have glandular cell type-characteristics in both the gene expression and morphology. It was also revealed that FOXA1 siRNA treatment of esophageal cancer cells reduced the mRNA level of both KRT7 and a stabilizer of epithelial-mesenchymal transition (EMT) regulator LOXL2, and that both FOXA1 and LOXL2 siRNAs reduced invasion and migration of ESCC cells. In 15 KRT7-expressing ESCCs with metastatic lymph nodes, 60% expressed FOXA1 and 33% expressed both FOXA1 and LOXL2. These results suggest that FOXA1 induces not only KRT7 but also LOXL2 in a subset of poor prognostic ESCCs with metastatic lymph nodes, and it is also plausible, that other FOXA1 downstream genes could be therapeutic targets of poor prognostic ESCCs.

Lysyl oxidase family members have various roles in cancer progression. The aim of this study was to investigate their expression and clinical significance in esophageal squamous cell carcinoma. We examined messenger RNA expression of lysyl oxidase family members including lysyl oxidase and lysyl oxidase-like proteins (lysyl oxidase L) in 10 esophageal squamous cell carcinoma cell lines and 83 pairs of tumor samples by quantitative real-time polymerase chain reaction. All except lysyl oxidase L3 were expressed at high levels in esophageal squamous cell carcinoma, but only lysyl oxidase L2 was associated with lymph node metastasis (P = .034). We examined lysyl oxidase L2 protein further by immunohistochemistry staining in 178 surgically resected esophageal squamous cell carcinoma tissue samples. The protein manifested decreased nuclear expression and increased cytoplasmic expression. Moreover, these 2 events both had significant correlation with the presence of lymph node metastasis (P = .001 and P < .001). Overall survival rates of the patients with esophageal squamous cell carcinoma with decreased nuclear expression or increased cytoplasmic expression of lysyl oxidase L2 were significantly lower than those of the patients with esophageal squamous cell carcinoma with the reverse expression pattern (P = .040 or P = .022). Multivariate analyses revealed that nuclear expression of lysyl oxidase L2 was an independent prognostic factor for esophageal squamous cell carcinoma. These results suggest that lysyl oxidase L2 exerts a critical effect on esophageal squamous cell carcinoma progression and can be a predictive marker of lymph node metastasis and outcome.

Poor prognosis of cancers, including hepatocellular carcinoma (HCC), is mainly associated with metastasis; however, the underlying mechanisms remain poorly understood. This article investigates the role of lysyl oxidase-like 2 (LOXL-2) in the biology of HCC metastasis. First, we showed that HCC metastasis relies on a collagen-modifying enzyme, LOXL2, which was significantly overexpressed in tumorous tissues and sera of HCC patients, indicating that LOXL2 may be a good diagnostic marker for HCC patients. Second, we delineated a complex, interlinked signaling network that involves multiple regulators, including hypoxia, transforming growth factor beta (TGF-beta), and microRNAs (miRNAs), converging to control the expression of LOXL2. We found not only that LOXL2 was regulated by hypoxia/hypoxia-inducible factor 1 alpha (HIF-1alpha), but also that TGF-beta activated LOXL2 transcription through mothers against decapentaplegic homolog 4 (Smad4), whereas two frequently underexpressed miRNA families, miR-26 and miR-29, cooperatively suppressed LOXL2 transcription through interacting with the 3' untranslated region of LOXL2. Third, we demonstrated the imperative roles of LOXL2 in modifying the extracellular matrix components in the tumor microenvironment and metastatic niche of HCC. LOXL2 promoted intrahepatic metastasis by increasing tissue stiffness, thereby enhancing the cytoskeletal reorganization of HCC cells. Furthermore, LOXL2 facilitated extrahepatic metastasis by enhancing recruitment of bone-marrow-derived cells to the metastatic site. CONCLUSION: These findings integrate the clinical relevance, molecular regulation, and functional implications of LOXL2 in HCC metastasis.

Several members of the lysyl oxidase family have recently emerged as important regulators of tumor progression. Among them, LOXL2 has been shown to be involved in tumor progression and metastasis of several tumor types, including breast carcinomas. Secreted LOXL2 participates in the remodeling of the extracellular matrix of the tumor microenvironment, in a similar fashion to prototypical lysyl oxidase. In addition, new intracellular functions of LOXL2 have been described, such as its involvement in the regulation of the epithelial-to-mesenchymal transition, epithelial cell polarity and differentiation mediated by transcriptional repression mechanisms. Importantly, intracellular (perinuclear) expression of LOXL2 is associated with poor prognosis and distant metastasis of specific tumor types, such as larynx squamous cell carcinoma and basal breast carcinomas. These recent findings open new avenues for the therapeutic utility of LOXL2.

cancer-associated fibroblasts enhance cancer progression when activated by tumor cells through mechanisms not yet fully understood. Blocking mammary tumor cell-derived lysyl oxidase-like 2 (LOXL2) significantly inhibited mammary tumor cell invasion and metastasis in transgenic and orthotopic mouse models. Here, we discovered that tumor-derived LOXL2 directly activated stromal fibroblasts in the tumor microenvironment. Genetic manipulation or antibody inhibition of LOXL2 in orthotopically grown mammary tumors reduced the expression of alpha-smooth muscle actin (alpha-SMA). Using a marker for reticular fibroblasts, it was determined that expression of alpha-SMA was localized to fibroblasts recruited from the host tissue. This marker also revealed that the matrix present in tumors with reduced levels of LOXL2 was more scattered compared with control tumors which exhibited matrices with dense, parallel alignments. Importantly, in vitro assays revealed that tumor-derived LOXL2 and a recombinant LOXL2 protein induced fibroblast branching on collagen matrices, as well as increased fibroblast-mediated collagen contraction and invasion of fibroblasts through extracellular matrix. Moreover, LOXL2 induced the expression of alpha-SMA in fibroblasts grown on collagen matrices. Mechanistically, it was determined that LOXL2 activated fibroblasts through integrin-mediated focal adhesion kinase activation. These results indicate that inhibition of LOXL2 in tumors not only reduces tumor cell invasion but also attenuates the activation of host cells in the tumor microenvironment. IMPLICATIONS: These findings reveal new insight into the mechanisms of fibroblast activation, a novel function of LOXL2, and further highlight the importance of generating LOXL2-targeted therapies for the prevention of tumor progression and metastasis.