Similar to normal tissue stem cells, cancer stem cells (CSCs) are thought to be quiescent or slow-cycling and, thereby, insensitive to chemo-and radiotherapies. CD44, a cell surface component that interacts with the extracellular matrix, has been found to be highly expressed in CSCs of several solid tumors. However, the relevancy between CD44+ cells and slow-cycling cells and the underlying mechanisms for the emergence of CD44 + CSCs during tumorigenesis have not been elucidated. Here we show that a gastric gland residing at the squamo-columnar junction (SCJ) in normal mouse stomach contains CD44 + stem cell-like slow-cycling cells and that this characteristic CD44 + gland was expanded by prostaglandin E2 (PGE 2 ) and Wnt signaling in K19-Wnt1 ⁄ C2mE mouse, a genetic mouse model for gastric tumorigenesis. The analysis of three transgenic mouse lines, K19-Wnt1, K19-C2mE and K19-Wnt1 ⁄ C2mE, revealed that the expansion of CD44 + SCJ cells is triggered by PGE 2 -mediated signaling and is prominently enhanced by the addition of Wnt activation. Furthermore, each expanded CD44 + gland in gastric tumor of K19-Wnt1 ⁄ C2mE mouse contains a few BrdU label-retaining quiescent or slow-cycling cells, suggesting that the CD44 + SCJ cells in normal mouse are candidates for the cell-of-origin of gastric CSCs. These observations suggest that PGE 2 -mediated inflammatory signaling and Wnt signaling cooperatively trigger the expansion of CD44 + slow-cycling stem-like cells in SCJ, leading to development of lethal gastric tumors in mice. (Cancer Sci 2010; 101: 673-678) C D44, a major cell adhesion molecule, has been implicated in a wide variety of physiological processes and pathological processes, including lymphocyte homing, wound healing, and cell migration, as well as cancer cell growth and metastasis.(1,2) CD44 has been recently detected as a cell surface marker of cancer stem cells (CSCs) in several types of cancer.(3) Moreover, a CD44 + subpopulation of cells isolated from several gastric cancer cell lines has been reported to have stem cell-like properties, which are the capacities to self-renew and to differentiate.(4) However, the underlying mechanism by which CD44 + CSC-like subpopulations emerge in the process of tumor development is largely unknown. Cancer stem cells, also known as cancer-initiating cells, are responsible for tumor initiation and maintenance. CSCs possess the ability to drive tumor growth and are inherently resistant to chemo-and radiotherapies. Recent studies have revealed that melanoma-initiating cells (5) and leukemia-initiating cells are a slow-cycling or quiescent subpopulation.(6,7) These quiescent or slow-cycling properties are thought to be a major reason why CSCs are resistant to cancer therapies targeted at proliferating cells. It has been shown that cell adhesion molecules play an essential role in the quiescence of hematopoietic stem cells by regulating adhesion in the osteoblastic niche.(8) Therefore, we hypothesized that CD44, which is highly expressed in CSCs, is involved in the regul...

Although cancer metastasis is associated with poor prognosis, the mechanisms of this event, especially via lymphatic vessels, remain unclear. Lymphatic vessel endothelial hyaluronan receptor 1 (LYVE‐1) is expressed on lymphatic vessel endothelium and is considered to be a specific marker of lymphatic vessels, but it is unknown how LYVE‐1 is involved in the growth and metastasis of cancer cells. We produced rat monoclonal antibodies (mAb) recognizing the extracellular domain of mouse LYVE‐1, and investigated the roles of LYVE‐1 in tumor formation and metastasis. The mAb 38M and 64R were selected from hybridoma clones created by cell fusion between spleen cells of rats immunized with RH7777 rat hepatoma cells expressing green fluorescent protein (GFP)‐fused mouse LYVE‐1 proteins and mouse myeloma cells. Two mAb reacted with RH7777 and HEK293F human embryonic kidney cells expressing GFP‐fused mouse LYVE‐1 proteins in a GFP expression‐dependent manner, and each recognized a distinct epitope. On immunohistology, the 38M mAb specifically stained lymphatic vessels in several mouse tissues. In the wound healing assay, the 64R mAb inhibited cell migration of HEK293F cells expressing LYVE‐1 and mouse lymphatic endothelial cells (LEC), as well as tube formation by LEC. Furthermore, this mAb inhibited primary tumor formation and metastasis to lymph nodes in metastatic MDA‐MB‐231 xenograft models. This shows that LYVE‐1 is involved in primary tumor formation and metastasis, and it may be a promising molecular target for cancer therapy.

BackgroundCD44 is a major cellular receptor for hyaluronic acids. The stem structure of CD44 encoded by ten normal exons can be enlarged by ten variant exons (v1-v10) by alternative splicing. We have succeeded in preparing MV5 fully human IgM and its class-switched GV5 IgG monoclonal antibody (mAb) recognizing the extracellular domain of a CD44R1 isoform that contains the inserted region coded by variant (v8, v9 and v10) exons and is expressed on the surface of various human epithelial cancer cells.Methods and Principal FindingsWe demonstrated the growth inhibition of human cancer xenografts by a GV5 IgG mAb reshaped from an MV5 IgM. The epitope recognized by MV5 and GV5 was identified to a v8-coding region by the analysis of mAb binding to various recombinant CD44 proteins by enzyme-linked immunosorbent assay. GV5 showed preferential reactivity against various malignant human cells versus normal human cells assessed by flow cytometry and immunohistological analysis. When ME180 human uterine cervix carcinoma cells were subcutaneously inoculated to athymic mice with GV5, significant inhibition of tumor formation was observed. Furthermore, intraperitoneal injections of GV5markedly inhibited the growth of visible established tumors from HSC-3 human larynx carcinoma cells that had been subcutaneously transplanted one week before the first treatment with GV5. From in vitro experiments, antibody-dependent cellular cytotoxicity and internalization of CD44R1 seemed to be possible mechanisms for in vivo anti-tumor activity by GV5.ConclusionsCD44R1 is an excellent molecular target for mAb therapy of cancer, possibly superior to molecules targeted by existing therapeutic mAb, such as Trastuzumab and Cetuximab recognizing human epidermal growth factor receptor family.

We examined expression of Heat Shock Protein 27 (HSP27) molecules, in 10 cases of typical solid/ multicystic ameloblastoma, by means of immunohistochemistry. In general, HSP27 and pHSP27 positive staining products were frequently detected in the cytoplasms of the neoplastic cells. The expression pattern and/or strength are slightly different according to the cytological features of ameloblastomas. The immunohistochemical staining results suggest that the expression of HSP27 and pHSP27 is considered to be involved in neoplastic transformation of odontogenic epithelial cells.

Electrochemotherapy (ECT) is currently receiving much attention as a method that can enhance the delivery of antitumour drugs into tumour cells by electroporation. In this study, we examined the effect of cisplatin on metastatic lesions of hamster oral fibrosarcoma by administering it in association with low-voltage electrical pulses. Oral fibrosarcoma was transplanted submucosally into the cheek pouches of 80 hamsters. After transplantation, when the diameter of the metastatic lesion in the left submandibular lymph node had reached 100 mm 3 , the hamsters were divided into four groups: D+E+ group (cisplatin treatment followed by electroporation; D+E-group (cisplatin treatment); D-E+ group (electroporation without cisplatin treatment); and D-E-group (no treatment). The antitumour effect of cisplatin was marked in the D+E+ group and the metastatic lesion disappeared in some of the animals. These results showed that when ECT consisting of cisplatin plus low-voltage electroporation was applied to metastatic tumour lesions, the antitumour effect of the drug on the lesions was enhanced. Therefore, ECT would seem to be a highly-safe new method that may be of use in the treatment of metastatic tumours.