Targeting Tumor Vascular CD99 Inhibits Tumor Growth.

CD99 (MIC2; single-chain type-1 glycoprotein) is a heavily O-glycosylated transmembrane protein (32 kDa) present on leukocytes and activated endothelium. Expression of CD99 on endothelium is important in lymphocyte diapedesis. CD99 is a diagnostic marker for Ewing's Sarcoma (EWS), as it is highly expressed by these tumors. It has been reported that CD99 can affect the migration, invasion and metastasis of tumor cells. Our results show that CD99 is also highly expressed in the tumor vasculature of most solid tumors. Furthermore, we found that in vitro CD99 expression in cultured endothelial cells is induced by starvation. Targeting of murine CD99 by a conjugate vaccine, which induced antibodies against CD99 in mice, resulted in inhibition of tumor growth in both a tumor model with high CD99 (Os-P0109 osteosarcoma) and low CD99 (CT26 colon carcinoma) expression. We demonstrated that vaccination against CD99 is safe, since no toxicity was observed in mice with high antibody titers against CD99 in their sera during a period of almost 11 months. Targeting of CD99 in humans is more complicated due to the fact that the human and mouse CD99 protein are not identical. We are the first to show that growth factor activated endothelial cells express a distinct human CD99 isoform. We conclude that our observations provide an opportunity for specific targeting of CD99 isoforms in human tumor vasculature.

Targeting PDGF-mediated recruitment of pericytes blocks vascular mimicry and tumor growth.

Aggressive tumor cells can adopt an endothelial cell-like phenotype and contribute to the formation of a tumor vasculature, independent of tumor angiogenesis. This adoptive mechanism is referred to as vascular mimicry and it is associated with poor survival in cancer patients. To what extent tumor cells capable of vascular mimicry phenocopy the angiogenic cascade is still poorly explored. Here, we identify pericytes as important players in vascular mimicry. We found that pericytes are recruited by vascular mimicry-positive tumor cells in order to facilitate sprouting and to provide structural support of the vascular-like networks. The pericyte recruitment is mediated through platelet-derived growth factor (PDGF)-B. Consequently, preventing PDGF-B signaling by blocking the PDGF receptors with either the small tyrosine kinase inhibitor imatinib or blocking antibodies inhibits vascular mimicry and tumor growth. Collectively, the current study identifies an important role for pericytes in the formation of vascular-like structures by tumor cells. Moreover, the mechanism that controls the pericyte recruitment provides therapeutic opportunities for patients with aggressive vascular mimicry-positive cancer types. © 2018 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

New Approach to Rare Pediatric Multicystic Mesenteric Lymphangioma; Would It Guide the Development of Targeted Therapy?

In children, lymphangiomas are extremely rare pathologic entities that are characterized by unusual locations. The mesenteric localization is extremely rare in children, and the clinical signs usually mimic an acute abdominal syndrome. For most of the cases, their diagnosis is established by the radiologist, and the main therapeutic option is represented by surgery for lesion removal. We hereby describe the case of a 4 year old girl admitted to the pediatric emergency department for continuous abdominal pain, more intense in the orthostatic position, associated with abdominal distension, nausea, and vomiting. These symptoms raised the clinical suspicion of acute abdominal syndrome. The patient had no previous clinically significant events. Radiologic examination suggested a mesenteric multicystic lymphangioma certified by surgical and histopathological evaluation. No specific targeted therapy is currently available; moreover, no specific criteria for recurrences have been stated. A new approach of infantile lymphangiomas following surgery, regarding the use of specific lymphatic markers panel including D2-40, Prox-1, VEGFR-3, PDGFs, and Ki67 may improve the characterization of such lesions regarding their prognosis, recurrence rate and targeted therapy implementation especially for those with a more aggressive or recurrent behavior.

Consensus guidelines for the use and interpretation of angiogenesis assays.

The formation of new blood vessels, or angiogenesis, is a complex process that plays important roles in growth and development, tissue and organ regeneration, as well as numerous pathological conditions. Angiogenesis undergoes multiple discrete steps that can be individually evaluated and quantified by a large number of bioassays. These independent assessments hold advantages but also have limitations. This article describes in vivo, ex vivo, and in vitro bioassays that are available for the evaluation of angiogenesis and highlights critical aspects that are relevant for their execution and proper interpretation. As such, this collaborative work is the first edition of consensus guidelines on angiogenesis bioassays to serve for current and future reference.

The multifaceted role of podoplanin expression in hepatocellular carcinoma.

The role of podoplanin in hepatocellular carcinoma (HCC) is not clear yet. The aim of our study was to evaluate the expression of podoplanin in HCC and to determine its role in hepatocarcinogenesis. We performed immunohistochemistry with monoclonal D2-40 antibody, on paraffin-embedded tissue sections of 72 patients diagnosed with HCC. Lymphatic vessels density (LVD) was increased in patients who had vascular invasion at the time of diagnosis (P=0.018) and in those with associated cirrhosis (P=0.006). Tumor cells showing podoplanin expression were correlated with histological grade (P=0.040). Podoplanin-expressing cancer associated fibroblasts (CAFs) were correlated with both LVD (P=0.019) and tumor cells (P=0.015). Our results sustain the dual role of podoplanin in HCC by its involvement in both HCC tumorigenesis, lymphatic neovascularization and tumor invasion invasiveness. A possible crosstalk between epithelial and stromal tumor cells in HCC tumor microenvironment may be mediated by podoplanin, but this hypothesis needs further studies to elucidate this interrelation.

Anti-angiogenic and anti-cancer evaluation of betulin nanoemulsion in chicken chorioallantoic membrane and skin carcinoma in Balb/c mice.

Betulin (Bet), the main component of birch tree bark, has been recently reported to exert anticancer activity in several cell lines; however the underlying mechanisms are only partially elucidated. The aims of the present work were to assess the in vivo effects of betulin administered as nanoemulsion (NE) in two experimental models: (i) the chicken embryo chorioallantoic membrane (CAM) assay for the study of anti-angiogenic effects and (ii) the two-stage model of skin carcinoma induced in mice for the study of anti-tumor and anti-inflammatory effects, respectively. On the CAM of the chicken betulin in nanoemulsion (BetNE) shows a good penetrability at extra-embryonic tissue level, affecting both the chorioallantoic membrane as well as the yolk sac by reducing the capillary density. In the animal model, the potential impact of local application of betulin on the respiratory function of isolated liver mitochondria was further assessed. Topical application of betulin nanoemulsion for 12 weeks together with DMBA (7,12-dimethylbenz[a]anthracene) and TPA (12-O-tetradecanoylphorbol 13-acetate), as tumor initiator and promoter, enhanced the active respiration of isolated liver mitochondria. Betulin also inhibit skin tumor apparition and promotion, proved by histological results and VEGF (vascular endothelial growth factor) expression correlated to non-invasive measurements. Betulin is active in nanoemulsion formulation as a potential inhibitory on the angiogenic process in CAM assay. BetNE can develop a potent anti-inflammatory and anti-carcinogenic activity with a low toxicity at skin level. It can also influence the penetration of carcinogens and reduce damage in main organs (e.g., liver).

Characterization of endoglin and Ki-67 expression in endothelial cells from benign and malignant lesions of the uterine cervix.

Activation of endothelial cells is often associated with the cellular proliferation in vitro. CD105 is a more specific marker of activated endothelial cells from tumor vessels and Ki-67 is used to assess the proliferation status of both tumor and endothelial cells. The aim of the present study was to evaluate the status of endothelial cells using CD105 and Ki-67 immunohistochemistry in benign and malignant lesions of the uterine cervix. Double stain for CD105/Ki-67 in benign and malignant lesions of the uterine cervix showed that these two markers had divergent expression on endothelial cells from associated tumor blood vessels dependent on lesion type and proliferation status of tumor cells. Absence of CD105/Ki-67 coexpression in endothelial cells was correlated with histopathology of the uterine cervix lesions and tumor proliferative status. The present findings suggest that CD105 expression is an early event, specific for premalignant lesions of the uterine cervix, while endothelial proliferation assessed on Ki-67 combined with the lack of CD105 expression is often associated with invasive cervical carcinoma.