Jun Aoi

Angiopoietin-like Protein 2 Is an Important Facilitator of Inflammatory Carcinogenesis and Metastasis

Chronic inflammation plays important roles at different stages of cancer development, including carcinogenesis, tumor invasion, and metastasis, but molecular mechanisms linking inflammation to cancer development have not been fully clarified. Here, we report that expression of angiopoietin-like protein 2 (Angptl2), recently identified as a chronic inflammation mediator, is highly correlated with the frequency of carcinogenesis in a chemically induced skin squamous cell carcinoma (SCC) mouse model. Furthermore, Angptl2 expression in SCC is highly correlated with the frequency of tumor cell metastasis to distant secondary organs and lymph nodes. When SCC was induced in transgenic mice expressing Angptl2 in skin epithelial cells, epithelial-to-mesenchymal transitions in SCC as well as tumor angiogenesis and lymphangiogenesis were significantly increased, resulting in increased tumor cell metastasis and shortened survival compared with wild-type mice. Conversely, in a chemically induced SCC mouse model, carcinogenesis and metastasis were markedly attenuated in Angptl2 knockout mice, resulting in extended survival compared with wild-type mice. Overall, we propose that Angptl2 contributes to increased carcinogenesis and metastasis and represents a novel target to antagonize these pathologies.

Tumor cell-derived angiopoietin-like protein ANGPTL2 is a critical driver of metastasis

Strategies to inhibit metastasis have been mainly unsuccessful in part due to insufficient mechanistic understanding. Here, we report evidence of critical role for the angiopoietin-like protein 2 (ANGPTL2) in metastatic progression. In mice, Angptl2 has been implicated in inflammatory carcinogenesis but it has not been studied in human tumors. In patients with lung cancer, elevated levels of ANGPTL2 expression in tumor cells within the primary tumor were associated with a reduction in the period of disease-free survival after surgical resection. Transcription factors NFATc, ATF2, and c-Jun upregulated in aggressive tumor cells promoted increased Angptl2 expression. Most notably, tumor cell-derived ANGPTL2 increased in vitro motility and invasion in an autocrine/paracrine manner, conferring an aggressive metastatic tumor phenotype. In xenograft mouse models, tumor cell-derived ANGPTL2 accelerated metastasis and shortened survival whereas attenuating ANGPTL2 expression in tumor cells-blunted metastasis and extended survival. Overall, our findings showed that tumor cell-derived ANGPTL2 drives metastasis and provided an initial proof of concept for blockade of its action as a strategy to antagonize the metastatic process.

Down-regulation of miR-124/-214 in cutaneous squamous cell carcinoma mediates abnormal cell proliferation via the induction of ERK.

Squamous cell carcinoma (SCC) is one of the most common skin cancers. Because its potential to recur and metastasize leads to a poor prognosis and significant mortality, it is necessary to develop new early diagnostic tools and new therapeutic approaches. In this study, we found protein levels of ERK1 and ERK2 were increased in SCC cell lines without changing mRNA levels and that ERK1/2 mediates abnormal cell proliferation in these cells. Then, mechanisms underlying the overexpression of ERK1/2 in SCC were investigated focusing on microRNA. We found that miR-214 is the regulator of ERK1, whereas ERK2 is regulated by miR-124 and miR-214. Expression of miR-124 and miR-214 was significantly down-regulated in SCC in vitro and in vivo. Treatment with 5-aza-deoxycytidine and trichostatin A synergistically recovered the miR-124/-214 down-regulation in SCC cell line. However, bisulphite sequencing revealed the methylation status of miR-124/-214 promoter was not increased in the SCC cell line and tumor tissue. Taken together, the down-regulation of miR-124/-214 in SCC is most likely caused, at least in part, by hypermethylation of other promoter regions rather than the miR-124/-214 promoter. Supplementation of these microRNAs in the SCC cell line reduced the abnormal cell proliferation by normalizing ERK1/2 levels. Additionally, serum concentration of miR-124 was correlated with miR-124 expression levels in the tumor tissues and inversely correlated with tumor progression. On the other hand, miR-214 was not detected in the serum. Investigation of the regulatory mechanisms of keratinocyte proliferation by microRNA may lead to develop new biomarkers and treatments using microRNA.

Myasthenic crisis and polymyositis induced by one dose of nivolumab

An 80‐year‐old man, who developed multiple lymph node and skin metastasis of malignant melanoma, received nivolumab monotherapy. Two weeks after the first dose, he experienced anorexia and fatigue, and suffered from progressive, severe dyspnea and muscle weakness. We diagnosed him with myocarditis, myositis, and myasthenic crisis induced by nivolumab. We commenced steroid therapy, immune absorption therapy, plasma exchange therapy, and i.v. immunoglobulin therapy, and succeeded in saving his life. Because his serum level of anti‐acetylcholine receptor antibodies in a sample collected before nivolumab treatment were positive and were elevated significantly after nivolumab, we suspected that nivolumab triggered a severe autoimmune response, which progressed subclinical myasthenia gravis to myasthenic crisis. We carried out T cell receptor repertoire analysis using next‐generation sequencing technologies and identified infiltration of clonally expanded T cell populations in the skeletal muscle after nivolumab treatment, implying a very strong T cell immune response against muscular cells. To avoid severe immune‐related adverse events, the exclusion of patients with subclinical autoimmune disease is very important for treatment with immune checkpoint inhibitors.

The Secreted Protein ANGPTL2 Promotes Metastasis of Osteosarcoma Cells Through Integrin α5β1, p38 MAPK, and Matrix Metalloproteinases

Preventing signaling by ANGPTL2, which is stimulated by the tumor microenvironment, could inhibit metastasis. Microenvironment Drives Osteosarcoma Metastasis The selective pressures of the tumor microenvironment alter the behavior of cancer cells. Odagiri et al. found that the expression of ANGPTL2, encoding the secreted angiopoietin-like protein 2, increased in osteosarcoma cells grown in xenografts in mice or cultured in conditions that mimic the tumor microenvironment. Silencing ANGPTL2 or overexpressing a proteolytically cleaved form decreased matrix metalloproteinase-9 (MMP-9) activity, delayed the onset of metastasis from xenografts, and prolonged survival in mice. The abundance of ANGPTL2 correlated with that of MMP-9 in patient samples, and both inversely correlated with metastasis-free survival in patients. The findings highlight the influence of the tumor microenvironment and implicate ANGPTL2 as a target to hinder metastasis in osteosarcoma. The tumor microenvironment can enhance the invasive capacity of tumor cells. We showed that expression of angiopoietin-like protein 2 (ANGPTL2) in osteosarcoma (OS) cell lines increased and the methylation of its promoter decreased with time when grown as xenografts in mice compared with culture. Compared with cells grown in normal culture conditions, the expression of genes encoding DNA demethylation–related enzymes increased in tumor cells implanted into mice or grown in hypoxic, serum-starved culture conditions. ANGPTL2 expression in OS cell lines correlated with increased tumor metastasis and decreased animal survival by promoting tumor cell intravasation mediated by the integrin α5β1, p38 mitogen-activated protein kinase, and matrix metalloproteinases. The tolloid-like 1 (TLL1) protease cleaved ANGPTL2 into fragments in vitro that did not enhance tumor progression when overexpressed in xenografts. Expression of TLL1 was weak in OS patient tumors, suggesting that ANGPTL2 may not be efficiently cleaved upon secretion from OS cells. These findings demonstrate that preventing ANGPTL2 signaling stimulated by the tumor microenvironment could inhibit tumor cell migration and metastasis.

microRNA-7 down-regulation mediates excessive collagen expression in localized scleroderma.

Localized scleroderma (LSc), a connective tissue disorder restricted to the skin and subcutaneous tissue, is characterized by skin fibrosis due to an excessive deposition of types I collagen. The mechanism of such fibrosis is still unknown, but epigenetics may play some roles in the excessive collagen expression. In the present study, we investigated the mechanism of fibrosis seen in LSc, focusing on microRNA (miRNA). miRNA expression was determined by PCR array, real-time PCR, and in situ hybridization. The function of miRNA was evaluated using specific inhibitor. Immunoblotting was performed to detect α2(I) collagen protein. PCR array analysis using tissue miRNA demonstrated miR-7 level was significantly decreased in LSc skin as well as keloid tissue compared to normal skin in vivo. In situ hybridization also showed miR-7 expression in dermal fibroblasts was decreased in LSc dermis. The transfection of specific inhibitor for miR-7 into cultured normal dermal fibroblasts resulted in the up-regulation of α2(I) collagen protein in vitro. Also, the serum levels of miR-7 were significantly decreased in LSc patients compared with healthy controls, but serum miR-29a levels not. Systemic or local down-regulation of miR-7 may contribute to the pathogenesis of LSc via the overexpression of α2(I) collagen, and serum miR-7 may be useful as a disease marker. Investigation of the regulatory mechanisms of LSc by miRNA may lead to new treatments by the transfection into the lesional skin of this disease.

Angiopoietin-like protein 2 accelerates carcinogenesis by activating chronic inflammation and oxidative stress

Chronic inflammation has received much attention as a risk factor for carcinogenesis. We recently reported that Angiopoietin-like protein 2 (Angptl2) facilitates inflammatory carcinogenesis and metastasis in a chemically induced squamous cell carcinoma (SCC) of the skin mouse model. In particular, we demonstrated that Angptl2-induced inflammation enhanced susceptibility of skin tissues to “preneoplastic change” and “malignant conversion” in SCC development; however, mechanisms underlying this activity remain unclear. Using this model, we now report that transgenic mice overexpressing Angptl2 in skin epithelial cells (K14-Angptl2 Tg mice) show enhanced oxidative stress in these tissues. Conversely, in the context of this model, Angptl2 knockout (KO) mice show significantly decreased oxidative stress in skin tissue as well as a lower incidence of SCC compared with wild-type mice. In the chemically induced SCC model, treatment of K14-Angptl2 Tg mice with the antioxidant N-acetyl cysteine (NAC) significantly reduced oxidative stress in skin tissue and the frequency of SCC development. Interestingly, K14-Angptl2 Tg mice in the model also showed significantly decreased expression of mRNA encoding the DNA mismatch repair enzyme Msh2 compared with wild-type mice and increased methylation of the Msh2 promoter in skin tissues. Msh2 expression in skin tissues of Tg mice was significantly increased by NAC treatment, as was Msh2 promoter demethylation. Overall, this study strongly suggests that the inflammatory mediator Angptl2 accelerates chemically induced carcinogenesis through increased oxidative stress and decreased Msh2 expression in skin tissue. Implications: Angptl2-induced inflammation increases susceptibility to microenvironmental changes, allowing increased oxidative stress and decreased Msh2 expression; therefore, Angptl2 might be a target to develop new strategies to antagonize these activities in premalignant tissue. Mol Cancer Res; 12(2); 239–49. ©2013 AACR.

Sensitive detection of melanoma metastasis using circulating microRNA expression profiles.

Numerous studies have indicated that the serum levels of microRNAs are useful for the diagnosis or evaluation of activity in human diseases. However, determining the level of only one of the nearly 2000 microRNAs identified so far may be less significant. Accordingly, we examined the possibility that the expression pattern of multiple microRNAs in each patient may be a more reliable disease marker for melanoma, especially metastatic disease, focusing on the interaction among microRNAs. Six microRNAs (miR-9, miR-145, miR-150, miR-155, miR-203, and miR-205) were evaluated using real-time PCR in 11 patients with metastatic melanoma and in 16 patients without melanoma. The expression of the six microRNAs was significantly different between the patients with metastasis and those without it. MiR-9 and miR-205 and miR-203 and miR-205 showed significant correlations, and the combination of miR-9, miR-145, miR-150, miR-155, and miR-205 was more sensitive than when each miR was used individually to distinguish the patients with metastasis from those without it. This is the first report demonstrating the expression profiles of multiple microRNAs in melanoma patients. Clarifying the involvement of the microRNA network in the pathogenesis of melanoma may contribute to the development of new diagnostic tools and to advancing the understanding of this disease.

Discoidin Domain Receptor 2–microRNA 196a–Mediated Negative Feedback against Excess Type I Collagen Expression Is Impaired in Scleroderma Dermal Fibroblasts

Systemic sclerosis (SSc) is characterized by excess collagen deposition in the skin, due to intrinsic transforming growth factor-β (TGF-β) activation. We tried to determine the expression and the role of discoidin domain receptor 2 (DDR2) in SSc. The expression of DDR2 mRNA and protein was significantly decreased in SSc dermal fibroblasts, which was recovered by knocking down TGF-β. The knockdown of DDR2 in normal fibroblasts induced microRNA-196a expression, which led to type I collagen downregulation, indicating that DDR2 itself has a negative effect on microRNA-196a expression and inducible effect on collagen expression. In SSc fibroblasts, however, the DDR2 knockdown did not affect TGF-β signaling and microRNA-196a expression. The microRNA-196a levels were significantly decreased in normal fibroblasts treated with TGF-β and in SSc fibroblasts. Taken together our data indicate that, in SSc fibroblasts, intrinsic TGF-β stimulation induces type I collagen expression, and also downregulates DDR2 expression. This probably acts as a negative feedback mechanism against excess collagen expression, as a decreased DDR2 expression is supposed to stimulate the microRNA-196a expression and further change the collagen expression. However, in SSc fibroblasts the microRNA-196a expression was downregulated by TGF-β signaling. DDR2-microRNA-196a pathway may be a previously unreported negative feedback system, and its impairment may be involved in the pathogenesis of SSc.

The rs2910164 G>C polymorphism in microRNA-146a is associated with the incidence of malignant melanoma.

MicroRNA-146a (miR-146a) is one of the microRNAs (miRNAs) implicated in the pathogenesis of various cancers. Recently, single nucleotide polymorphisms (SNPs) located in miRNAs themselves, so-called MIRSNPs, have attracted attention because of their possible involvement in the pathogenesis of various diseases. Such MIRSNPs may play functional roles because of the alteration of the miRNA. In this study, we investigated whether MIRSNP rs2910164 in miR-146a is involved in the pathogenesis of malignant melanoma (MM). DNA samples were collected from 50 patients with MM and 107 controls and genotyped by a PCR-restriction fragment. In patients with MM, the genotype distributions were 15 CC (30.0%), 35 CG (70.0%), and 0 GG (0.0%). The CG genotype was significantly increased in the patients compared with the controls (P=0.02). The minimum free energy between miR-146a and its complementary strand with the G allele was determined to be −26.8 kcal/mol, whereas that of the C allele was −24.0 kcal/mol, indicating that the change from C to G may increase the stability of the miR-146a. However, there was no significant difference between the CC and the CG genotypes in terms of the relative expression levels of miR-146a. Human melanoma cell lines with the G allele showed significantly higher proliferation, migration, and invasion than those with the C allele. In conclusion, miR-146a may be involved in the pathogenesis of MM, and individuals with the CG genotype have an increased risk of developing MM.