Correlation between endothelial CXCR7 expression and clinicopathological factors in oral squamous cell carcinoma.

Oral squamous cell carcinoma (OSCC) impairs functionality and sensuousness resulting in poor quality of life. Biomarkers can predict disease trajectory and lead to effective treatments. Transcriptomics have identified genes that are upregulated in tumor endothelial cells (TECs) compared with normal endothelial cells (NECs). Among them, chemokine receptor 7 (CXCR7) is highly expressed in TECs of several cancers and involved in angiogenesis of TECs. However, levels of CXCR7 in OSCC blood vessels have not been fully investigated. In this study, we analyzed the correlation between CXCR7 expression in TECs and clinicopathological factors in OSCC. Immunohistochemistry for CXCR7 and CD34 was performed on 59 OSCC tissue specimens resected between 1996 and 2008 at Hokkaido University Hospital. CXCR7 expression in blood vessels was evaluated by the ratio of CXCR7+/CD34+ blood vessels. CXCR7 expression was 42% and 19% in tumor and non-tumor parts, respectively, suggesting that CXCR7 expression is higher in TECs than in NECs. CXCR7 expression in TECs correlated with advanced T-stage and cancer stage. Overall survival and disease-free survival rates were higher in low-expressing CXCR7 patients than in high-expressing. These results suggest that CXCR7 expression in blood vessels may be a useful diagnostic and prognostic marker for OSCC patients.

HuR translocation to the cytoplasm of cancer cells in actin-independent manner.

Human antigen R (HuR) is a RNA-binding protein, which binds to the AU-rich element (ARE) in the 3'-untranslated region (3'-UTR) of certain mRNA and is involved in the export and stabilization of ARE-mRNA. HuR constitutively relocates to the cytoplasm in many cancer cells, however the mechanism of intracellular HuR trafficking is poorly understood. To address this question, we examined the functional role of the cytoskeleton in HuR relocalization. We tested the effect of actin depolymerizing macrolide latrunculin A or myosin II ATPase activity inhibitor blebbistatin for HuR relocalization induced by the vasoactive hormone Angiotensin II in cancer and control normal cells. Western blot and confocal imaging data revealed that both inhibitors attenuated the cytoplasmic HuR in normal cells but no such alteration was observed in cancer cells. Concomitant with changes in intracellular HuR localization, both inhibitors markedly decreased the accumulation and half-lives of HuR target ARE-mRNAs in normal cells, whereas no change was observed in cancer cells. Furthermore, co-immunoprecipitation experiments with HuR proteins revealed clear physical interaction with ß-actin only in normal cells. The current study is the first to verify that cancer cells can implicate a microfilament independent HuR transport. We hypothesized that when cytoskeleton structure is impaired, cancer cells can acquire an alternative HuR trafficking strategy.

Adenovirus infection induces HuR relocalization to facilitate virus replication.

HuR is an RNA-binding protein of the embryonic lethal abnormal vision (ELAV) family, which binds to the AU-rich element (ARE) in the 3'-untranslated region (UTR) of certain mRNAs and is involved in the nucleo-cytoplasmic export and stabilization of ARE-mRNAs. The cytoplasmic relocalization of ARE-mRNAs with several proteins such as HuR and pp32 increases in cells transformed by the adenovirus oncogene product E4orf6. Additionally, these ARE-mRNAs were stabilized and acquired the potential to transform cells. Although, the relocalization of HuR and the stabilization of ARE-mRNAs are crucial for cell transformation, evidence regarding the relationship of HuR and ARE-mRNAs with adenovirus replication is lacking. In this report, we demonstrate that adenovirus infection induces the relocation of HuR to the cytoplasm of host cells. Analysis using the luciferase-ARE fusion gene and the tetracycline (tet)-off system revealed that the process of stabilizing ARE-mRNAs is activated in adenovirus-infected cells. Heat shock treatment or knockdown-mediated depletion of HuR reduced adenovirus production. Furthermore, expression of ARE-including viral IVa2 mRNA, decreased in HuR-depleted infected cells. These results indicate that HuR plays an important role in adenovirus replication, at least in part, by up-regulating IVa2 mRNA expression and that ARE-mRNA stabilization is required for both transformation and virus replication.

Patients with SATB2-associated syndrome exhibiting multiple odontomas.

Special AT-rich sequence-binding protein 2 (SATB2)-associated syndrome (SAS) is characterized by alterations of SATB2. Its clinical features include intellectual disability and craniofacial abnormalities, such as cleft palate, dysmorphic features, and dental abnormalities. Here, we describe three previously undiagnosed, unrelated patients with SAS who exhibited dental abnormalities, including multiple odontomas. Although isolated odontomas are common, multiple odontomas are rare. Individuals in families 1 and 3 underwent whole-exome sequencing. Patient 2 and parents underwent targeted amplicon sequencing. On the basis of the hg19/GRCh37 reference and the RefSeq mRNA NM_001172517, respective heterozygous mutations were found and validated in Patients 1, 2, and 3: a splice-site mutation (chr2:g.200137396C > T, c.1741-1G > A), a nonsense mutation (chr2:g.200213750G > A, c.847C > T, p.R283*), and a frame-shift mutations (chr2:g.200188589_200188590del, c.1478_1479del, p.Q493Rfs*19). All mutations occurred de novo. The mutations in Patients 1 and 3 were novel; the mutation in Patient 2 has been described previously. Tooth mesenchymal cells derived from Patient 2 showed diminished SATB2 expression. Multiple odontomas were evident in the patients in this report; however, this has not been recognized previously as a SAS-associated phenotype. We propose that multiple odontomas be considered as an occasional manifestation of SAS.

Tumor endothelial cells with high aldehyde dehydrogenase activity show drug resistance.

Tumor blood vessels play an important role in tumor progression and metastasis. We previously reported that tumor endothelial cells (TEC) exhibit several altered phenotypes compared with normal endothelial cells (NEC). For example, TEC have chromosomal abnormalities and are resistant to several anticancer drugs. Furthermore, TEC contain stem cell-like populations with high aldehyde dehydrogenase (ALDH) activity (ALDHhigh TEC). ALDHhigh TEC have proangiogenic properties compared with ALDHlow TEC. However, the association between ALDHhigh TEC and drug resistance remains unclear. In the present study, we found that ALDH mRNA expression and activity were higher in both human and mouse TEC than in NEC. Human NEC:human microvascular endothelial cells (HMVEC) were treated with tumor-conditioned medium (tumor CM). The ALDHhigh population increased along with upregulation of stem-related genes such as multidrug resistance 1, CD90, ALP, and Oct-4. Tumor CM also induced sphere-forming ability in HMVEC. Platelet-derived growth factor (PDGF)-A in tumor CM was shown to induce ALDH expression in HMVEC. Finally, ALDHhigh TEC were resistant to fluorouracil (5-FU) in vitro and in vivo. ALDHhigh TEC showed a higher grade of aneuploidy compared with that in ALDHlow TEC. These results suggested that tumor-secreting factor increases ALDHhigh TEC populations that are resistant to 5-FU. Therefore, ALDHhigh TEC in tumor blood vessels might be an important target to overcome or prevent drug resistance.

Inhibition of multidrug transporter in tumor endothelial cells enhances antiangiogenic effects of low-dose metronomic paclitaxel.

Tumor angiogenesis plays an important role in tumor progression and metastasis. Tumor endothelial cells (TECs) are a therapeutic target of antiangiogenic chemotherapy that was recently developed and is currently being investigated in the clinic with promising results. Low-dose chemotherapy, which is the long-term administration of relatively low doses of chemotherapeutic agents, has been proposed for targeting tumor angiogenesis in various types of cancers. Although the efficacy of low-dose chemotherapy has been confirmed in several clinical models, some studies show insufficient therapeutic effect for malignant cancers. As a possible mechanism of the treatment failure, it has been considered that tumor cells may acquire resistance to this therapy. However, drug resistance by TECs may also be due to another mechanism for resistance of tumor cells to low-dose chemotherapy. We reported elsewhere that TECs were resistant to the anticancer drug paclitaxel, which is a mitotic inhibitor, concomitant with P-glycoprotein up-regulation. Verapamil, a P-glycoprotein inhibitor, abrogated TEC resistance in vitro. Herein, we demonstrated that verapamil coadministration enhanced the effects of low-dose paclitaxel concomitant with inhibiting tumor angiogenesis in a preclinical in vivo mouse melanoma xenograft model. Furthermore, verapamil coadministration reduced lung metastasis. These results suggest that inhibiting P-glycoprotein in TECs may be a novel strategy for low-dose chemotherapy targeting TECs.

Tumor endothelial cells express high pentraxin 3 levels.

It has been described that tumor progression has many similarities to inflammation and wound healing in terms of the signaling processes involved. Among biological responses, angiogenesis, which is necessary for tumor progression and metastasis, is a common hallmark; therefore, tumor blood vessels have been considered as important therapeutic targets in anticancer therapy. We focused on pentraxin 3 (PTX3), which is a marker of cancer-related inflammation, but we found no reports on its expression and function in tumor blood vessels. Here we showed that PTX3 is expressed in mouse and human tumor blood vessels based on immunohistochemical analysis. We found that PTX3 is upregulated in primary mouse and human tumor endothelial cells compared to normal endothelial cells. We also showed that PTX3 plays an important role in the proliferation of the tumor endothelial cells. These results suggest that PTX3 is an important target for antiangiogenic therapy.

Anti-BP180-type mucous membrane pemphigoid: report of two cases.

We describe two patients with anti-BP180-type mucous membrane pemphigoid (MMP), who were correctly diagnosed and treated in early stages through the cooperation of dentists and dermatologists. Patient 1 was a 74-year-old woman who visited our dental department due to blisters over the oral mucosa and eruptions on the skin. She had also experienced bleeding of the gingiva and palate mucosa. Biopsy specimens from the oral mucosa revealed detachment of epithelial basement membrane and subepithelial lamina propria with slight chronic inflammation. Direct immunofluorescence (DIF) revealed linear IgG and IgA deposits along the basement membrane zone (BMZ). Indirect immunofluorescence (IIF) using 1 M-NaCl split normal human skin showed binding of IgG and IgA on the epidermal side. On immunoblot analysis, IgG and IgA autoantibodies reacted with the C-terminal protein of BP180. These findings indicated a diagnosis of anti-BP180-type MMP. Patient 2 was a 59-year-old woman who was referred to our dental department with a history of blisters and large erosions on the gingiva. Biopsy specimens from the oral mucosa revealed partial junctional separation at the level of the basement membrane. DIF showed linear depositions of IgG and C3 along the BMZ. IIF, using 1 M-NaCl split normal human skin, revealed circulating anti-BMZ-IgG antibodies bound to the epidermal side. These findings indicated a diagnosis of anti-BP180-type MMP. Both patients were treated successfully with systemic or topical steroids and oral health care. In conclusion, appropriate clinical examination and cooperation among medical specialists are important for the early diagnosis and treatment of patients with recurrent and chronic stomatitis and for their good prognosis.

CXCL12-CXCR7 axis is important for tumor endothelial cell angiogenic property.

We reported that tumor endothelial cells (TECs) differ from normal endothelial cells (NECs) in many aspects, such as gene expression profiles. Although CXCR7 is reportedly highly expressed in blood vessels of several tumors, its function in TECs is still unknown. To investigate this role, we isolated TECs from mouse tumor A375SM xenografts, and compared them with NECs from normal mouse dermis. After confirming CXCR7 upregulation in TECs, we analyzed its function using CXCR7 siRNA and CXCR7 inhibitor; CCX771. CXCR7 siRNA and CCX771 inhibited migration, tube formation and resistance to serum starvation in TECs but not in NECs. ERK1/2 phosphorylation was inhibited by CXCR7 knockdown in TECs. These results suggest that CXCR7 promotes angiogenesis in TECs via ERK1/2 phosphorylation. Using ELISA, we also detected CXCL12, a ligand of CXCR7, in conditioned medium from TECs, but not from NECs. CXCL12 neutralizing antibody significantly inhibited TEC random motility. VEGF stimulation upregulated CXCR7 expression in NECs, implying that VEGF mediates CXCR7 expression in endothelial cells. A CXCR7 inhibitor, CCX771 also inhibited tumor growth, lung metastasis and tumor angiogenesis in vivo. Taken together, the CXCL12-CXCR7 autocrine loop affects TEC proangiogenic properties, and could be the basis for an antiangiogenic therapy that specifically targets tumor blood vessels rather than normal vessels.

Suprabasin as a novel tumor endothelial cell marker.

Recent studies have reported that stromal cells contribute to tumor progression. We previously demonstrated that tumor endothelial cells (TEC) characteristics were different from those of normal endothelial cells (NEC). Furthermore, we performed gene profile analysis in TEC and NEC, revealing that suprabasin (SBSN) was upregulated in TEC compared with NEC. However, its role in TEC is still unknown. Here we showed that SBSN expression was higher in isolated human and mouse TEC than in NEC. SBSN knockdown inhibited the migration and tube formation ability of TEC. We also showed that the AKT pathway was a downstream factor of SBSN. These findings suggest that SBSN is involved in the angiogenic potential of TEC and may be a novel TEC marker.

RANKL synthesized by both stromal cells and cancer cells plays a crucial role in osteoclastic bone resorption induced by oral cancer.

The molecular mechanisms underlying bone destruction by invading oral cancer are not well understood. Using IHC, we demonstrated that receptor activator of nuclear factor-κB ligand (RANKL)-positive fibroblasts and cancer cells were located at sites of bone invasion in human oral cancers. HSC3 and HO-1-N-1, human oral cancer cell lines, expressed RANKL and stimulated Rankl expression in the UAMS-32 murine osteoblastic cell line. We discriminated the roles of RANKL synthesized by stromal cells and cancer cells in cancer-associated bone resorption by using species-specific RANKL antibodies against murine RANKL and human RANKL, respectively. Osteoclastogenesis induced by the conditioned medium of HSC3 and HO-1-N-1 cells in a co-culture of murine bone marrow cells and UAMS-32 cells was inhibited by the addition of antibodies against either mouse or human RANKL. HSC3-induced bone destruction was greatly inhibited by the administration of anti-mouse RANKL antibody in a xenograft model. HO-1-N-1-induced bone destruction was inhibited by the administration of either anti-mouse or anti-human RANKL antibody. Bone destruction induced by the transplantation of human RANKL-overexpressing cells (HSC3-R2) was greatly inhibited by the injection of anti-human RANKL antibody. The present study revealed that RANKL produced by both stromal and cancer cells is involved in oral cancer-induced osteoclastic bone resorption. These results provide important information for understanding the cellular and molecular basis of cancer-associated bone destruction and the mechanism of action underlying RANKL antibody (denosumab) therapy.

Advantage of FMISO-PET over FDG-PET for predicting histological response to preoperative chemotherapy in patients with oral squamous cell carcinoma.

PURPOSE: Hypoxia, a prognostic factor in many types of cancer, can be detected by (18)F-fluoromisonidazole (FMISO) positron emission tomography (PET). It is unclear whether hypoxia reflects the response to chemotherapy in patients with oral squamous cell carcinoma (OSCC). The correlations of FMISO-PET and FDG-PET with histological response to preoperative chemotherapy were therefore assessed in patients with OSCC. METHODS: This study enrolled 22 patients with OSCC undergoing preoperative chemotherapy. The T-stages were T2 in 6 patients, T3 in 3, and T4a in 13, and the N-stages were N0 in 14 patients, N1 in 3, and N2 in 5. Each patient was evaluated by both FMISO-PET and FDG-PET before surgery, and the maximum standardized uptake value (SUVmax) of FDG- and FMISO-PET and tumor-muscle ratio (TMR) of FMISO-PET were measured. The threshold for the hypoxic volume based on TMR was set at 1.25. The histological response to preoperative chemotherapy was evaluated using operative materials. RESULTS: FMISO-PET and FDG-PET detected uptake by primary OSCCs in 15 (68%) and 21 (95%) patients, respectively, and median SUVmaxs of FMISO- and FDG-PET in the primary site were 2.0 (range, 1.3-3.5) and 16.0 (range, 1.0-32.2), respectively. The median of FMISO TMR was 1.5 (range, 0.99-2.96). There were five cases whose FMISO TMR was less than 1.25. Histological evaluation showed good response to preoperative chemotherapy in 7 patients (32%) and poor response in 15 (68%). Good response was significantly more prevalent in patients with negative than positive FMISO uptake (P < 0.001) and without the hypoxic area evaluated by FMISO-PET TMR (P = 0.04), whereas FDG uptake was not significantly correlated with response to chemotherapy response. Multivariate logistic regression analysis showed that FMISO uptake was an independent significant predictor of response to preoperative chemotherapy (P = 0.03, odds ratio = 0.06, 95% confidence interval = 0.004-0.759). CONCLUSIONS: An advantage of FMISO-PET over FDG-PET for predicting histological response to preoperative chemotherapy in patients with OSCC was observed.

Tumor endothelial cells acquire drug resistance by MDR1 up-regulation via VEGF signaling in tumor microenvironment.

Tumor endothelial cells (TECs) are therapeutic targets in anti-angiogenic therapy. Contrary to the traditional assumption, TECs can be genetically abnormal and might also acquire drug resistance. In this study, mouse TECs and normal ECs were isolated to investigate the drug resistance of TECs and the mechanism by which it is acquired. TECs were more resistant to paclitaxel with the up-regulation of multidrug resistance (MDR) 1 mRNA, which encodes the P-glycoprotein, compared with normal ECs. Normal human microvascular ECs were cultured in tumor-conditioned medium (CM) and became more resistant to paclitaxel through MDR1 mRNA up-regulation and nuclear translocation of Y-box-binding protein 1, which is an MDR1 transcription factor. Vascular endothelial growth factor (VEGF) receptor 2 (VEGFR2) and Akt were activated in human microvascular ECs by tumor CM. We observed that tumor CM contained a significantly high level of VEGF. A VEGFR kinase inhibitor, Ki8751, and a phosphatidylinositol 3-kinase-Akt inhibitor, LY294002, blocked tumor CM-induced MDR1 up-regulation. MDR1 up-regulation, via the VEGF-VEGFR pathway in the tumor microenvironment, is one of the mechanisms of drug resistance acquired by TECs. We observed that VEGF secreted from tumors up-regulated MDR1 through the activation of VEGFR2 and Akt. This process is a novel mechanism of the acquisition of drug resistance by TECs in the tumor microenvironment.

Heterogeneity of tumor endothelial cells: comparison between tumor endothelial cells isolated from high- and low-metastatic tumors.

An important concept in tumor angiogenesis is that tumor endothelial cells (TECs) are genetically normal and homogeneous. However, we previously reported that TECs differ from normal ECs. Whether the characteristics of TECs derived from different tumors differ remains unknown. To elucidate this, in this study, we isolated two types of TECs from high-metastatic (HM) and low-metastatic (LM) tumors and compared their characteristics. HM tumor-derived TECs (HM-TECs) showed higher proliferative activity and invasive activity than LM tumor-derived TECs (LM-TECs). Moreover, the mRNA expression levels of pro-angiogenic genes, such as vascular endothelial growth factor (VEGF) receptors 1 and 2, VEGF, and hypoxia-inducible factor-1α, were higher in HM-TECs than in LM-TECs. The tumor blood vessels themselves and the surrounding area in HM tumors were exposed to hypoxia. Furthermore, HM-TECs showed higher mRNA expression levels of the stemness-related gene stem cell antigen and the mesenchymal marker CD90 compared with LM-TECs. HM-TECs were spheroid, with a smoother surface and higher circularity in the stem cell spheroid assay. HM-TECs differentiated into osteogenic cells, expressing activated alkaline phosphatase in an osteogenic medium at a higher rate than either LM-TECs or normal ECs. Furthermore, HM-TECs contained more aneuploid cells than LM-TECs. These results indicate that TECs from HM tumors have a more pro-angiogenic phenotype than those from LM tumors.

The F-prostaglandin receptor is a novel marker for tumor endothelial cells in renal cell carcinoma.

Tumor angiogenesis is necessary for tumor progression and metastasis; therefore, tumor blood vessels are potential therapeutic targets in anticancer therapy. We previously reported that tumor endothelial cells (TECs) exhibit different phenotypes compared with normal endothelial cells (NECs), and microarray analyses of mouse TECs and NECs have shown that several genes are upregulated in TECs compared with NECs. Among these genes, the expression levels of prostaglandin F receptor (PTGFR) mRNA, which encodes the prostaglandin F receptor (FP), were higher in TECs than in NECs. It has been reported that FP and its ligand, prostaglandin F(2α) , are involved in tumor angiogenesis. However, there have been no reports of the expression of PTGFR in the tumor vessels of renal cell carcinoma (RCC). Thus, we isolated human TECs (hTECs) from RCCs. The expression levels of PTGFR mRNA were also upregulated in hTECs. In addition, immunostaining showed that the PTGFR was expressed in human tumor blood vessels in vivo. These findings suggested that PTGFR is a novel TEC marker and that it may be a novel target for antiangiogenic therapy for RCC.

Bovine Lactoferrin Suppresses Tumor Angiogenesis through NF-κB Pathway Inhibition by Binding to TRAF6.

Tumor angiogenesis is essential for tumor progression. The inhibition of tumor angiogenesis is a promising therapy for tumors. Bovine lactoferrin (bLF) has been reported as an anti-tumor agent. However, bLF effects on tumor angiogenesis are not well demonstrated. This study evaluated the inhibitory effects of bLF on tumor angiogenesis in vivo and in vitro. Herein, tumor endothelial cells (TECs) and normal endothelial cells (NECs) were used. Proliferation, migration, tube formation assays, RT-PCR, flow cytometry, Western blotting, siRNA experiments and immunoprecipitation were conducted to clarify the mechanisms of bLF-induced effects. CD-31 immunoexpression was examined in tumor tissues of oral squamous cell carcinoma mouse models with or without Liposomal bLF (LbLF)-administration. We confirmed that bLF inhibited proliferation/migration/tube formation and increased apoptosis in TECs but not NECs. TNF receptor-associated factor 6 (TRAF6), p-p65, hypoxia inducible factor-α (HIF-1α) and vascular endothelial growth factor (VEGF) were highly expressed in TECs. In TECs, bLF markedly downregulated VEGF-A, VEGF receptor (VEGFR) and HIF-1α via the inhibition of p-p65 through binding with TRAF6. Since NECs slightly expressed p-p65, bLF-TRAF-6 binding could not induce detectable changes. Moreover, orally administrated LbLF decreased CD31-positive microvascular density only in TECs. Hence, bLF specifically suppressed tumor angiogenesis through p-p65 inhibition by binding to TRAF6 and suppressing HIF-1α activation followed by VEGF/VEGFR down-regulation. Collectively, bLF can be an anti-angiogenic agent for tumors.

Cyclooxygenase-2 inhibition causes antiangiogenic effects on tumor endothelial and vascular progenitor cells.

Tumor angiogenesis is necessary for solid tumor progression and metastasis. Cyclooxygenase (COX)-2 is known to play an important role in cancer growth and invasion, and it activates the signaling pathways controlling cell proliferation, migration, apoptosis, and angiogenesis. COX-2 is reported to be expressed in many cancer cells. Several studies have reported successful treatment of cancer cells with COX-2 inhibitors (COX-2is). However, the effect of COX-2 inhibition on the tumor endothelium remains to be elucidated. Our study shows that COX-2 is expressed in the vasculature of surgically resected human tumors. To investigate the effects of COX-2 inhibition on the tumor endothelium in vitro, we isolated tumor endothelial cells (TECs) from human melanoma and oral carcinoma xenografts in mice, in which we confirmed that tumor growth was suppressed by inhibiting angiogenesis with the COX-2is NS398. COX-2 mRNA was upregulated in TECs compared to normal endothelial cells (NECs). Cell migration and proliferation were suppressed by NS398 in TECs but not in NECs. The effects of NS398 in vivo were consistent with the in vitro results. The number of CD133+ /vascular endothelial growth factor receptor-2+ cells in circulation was significantly suppressed by COX-2 inhibition. In addition, the number of progenitor marker-positive cells decreased in the tumor blood vessels after COX-2i treatment, which suggests that the homing of progenitor cells into the tumor was also blocked. We conclude that NS398 specifically targets both TECs and vascular progenitor cells without affecting NECs.

Prostacyclin receptor in tumor endothelial cells promotes angiogenesis in an autocrine manner.

Molecules highly expressed in tumor endothelial cells (TEC) are important for specific targeting of these cells. Previously, using DNA microarray analysis, we found that the prostacyclin receptor (IP receptor) gene was upregulated in TEC compared with normal endothelial cells (NEC). Although prostacyclin is implicated in re-endothelialization and angiogenesis, its role remains largely unknown in TEC. Moreover, the effect of the IP receptor on TEC has not been reported. In the present study we investigated the function of the IP receptor in TEC. The TEC were isolated from two types of human tumor xenografts in nude mice, while NEC were isolated from normal counterparts. Prostacyclin secretion levels in TEC were significantly higher than those in NEC, as shown using ELISA. Real-time RT-PCR showed that the IP receptor was upregulated in TEC compared with NEC. Furthermore, migration and tube formation of TEC were suppressed by the IP receptor antagonist RO1138452. Immunohistostaining showed that the IP receptor was specifically expressed in blood vessels of renal cell carcinoma specimens, but not in glomerular vessels of normal renal tissue. These findings suggest that the IP receptor is a TEC-specific marker and might be a useful therapeutic target.

RANKL expression specifically observed in vivo promotes epithelial mesenchymal transition and tumor progression.

Recent findings have focused attention on the molecular consequences of the microenvironment in tumor progression, but events occurring in cancer cells themselves in response to their ambient conditions remain obscure. Here, we identify receptor activator of nuclear factor κB ligand (RANKL) as a microenvironment-specific factor essential for tumorigenesis in vivo, using head and neck squamous cell carcinoma (HNSCC) as a model. In human HNSCC tissues, RANKL is abundantly expressed, and its expression level correlates with the histological grade of differentiation. RANKL levels are significantly higher in poorly differentiated SCCs than in well or moderately differentiated SCCs. In contrast, all HNSCC cell lines tested displayed extremely low RANKL expression; however, RANKL is efficiently up-regulated when these cell lines are inoculated in the head and neck region of mice. RANKL expression is restored in a microenvironment-specific manner, and cannot be observed when the cells are inoculated in the hindlimbs. Forced expression of RANKL compensates for tumor growth in the hindlimb milieu, promotes epithelial mesenchymal transition, and induces tumor angiogenesis, in a manner independent of vascular endothelial growth factor (VEGF). These results implicate RANKL expression causatively in tumor growth and progression in HNSCC in vivo. RANKL may provide a novel functional marker for biological malignancy and a therapeutic target based on the specific nature of the microenvironment.

CXCR7: a novel tumor endothelial marker in renal cell carcinoma.

Tumor angiogenesis is necessary for progression and metastasis of solid tumor. Tumor blood vessels are morphologically different from their normal counterparts. In this study, we isolated tumor endothelial cells (TECs) and revealed their abnormalities. We have compared the gene expression profiles of TECs and normal endothelial cells (NECs) by microarray analysis and found that several genes were upregulated in TECs. Expression of the chemokine receptor CXCR7 mRNA was higher in TECs than in NECs. However, information regarding the expression of CXCR7 in the tumor vessels of renal cell carcinoma is limited. CXCR7 and its ligand CXCL12 have been implicated in tumor cell survival. In this study, the expression of CXCR7 in the tumor vessels of renal cell carcinoma (RCC) was investigated. Real-time PCR revealed higher expression level of CXCR7 in cultured TECs than in cultured NECs. Furthermore, similar to mouse TECs, immunostaining revealed strong expression of CXCR7 in vivo in human tumor vessels. These findings suggest that CXCR7 is a novel TEC marker and a target for antiangiogenic therapy for RCC.