Involvement of CD24 in angiogenesis in a mouse model of oxygen-induced retinopathy

CD24 promoted cancer cell angiogenesis via Hsp90-mediated STAT3/VEGF signaling pathway in colorectal cancer

CD24 is involved in tumor progression of various cancers, but the effects of CD24 on tumor angiogenesis in colorectal cancer are still unknown. We aimed to investigate the underlying mechanism and role of CD24 on colorectal cancer (CRC) angiogenesis. Our data showed that the microvessal density (MVD) was related to the expression of CD24 in primary and metastasis CRC. Silencing of CD24 could dramatically decrease human umbilical vein endothelial cell (HUVEC) migration, invasion and tubule formation, but trivially affected cell proliferation. We also mechanically showed that silencing CD24 could downregulate the expression of VEGF via inhibiting the phosphorylation and translocation of STAT3. Moreover, Hsp90 was identified as the down-interaction protein of CD24 with co-immunoprecipitation assay and systematic mass spectrometry. Immunofluorescence results showed Hsp90 partly co-localized with CD24 in CRC cell membrane and there was a positive correlation between CD24 and Hsp90 expression in CRC tissues. We gradually evidenced that Hsp90 modulated the stability and degradation of CD24 in a proteasome-depended manner, and transferred the signal transmission from CD24 to STAT3. 17-AAG, a specific Hsp90, could abrogate the CD24 induce- HUVEC migration, invasion and tubule formation in vitro and in vivo. Collectively, our results suggested that CD24 induced CRC angiogenesis in Hsp90-dependent manner and activated STAT3-mediated transcription of VEGF. We provided a new insight into the regulation mechanism of tumor angiogenesis by exploring the role of CD24 in angiogenesis.

Downregulation of CD24 suppresses bone metastasis of lung cancer

Suppression of bone metastasis can improve patient quality of life. Current drugs for bone metastasis have been shown to prolong progression‐free survival but not overall survival; therefore, other potential therapeutic targets for bone metastasis should be investigated. Cell‐surface antigens, such as CD24, have been recently shown to be involved in the metastasis of various cancers. However, whether CD24 plays a role in bone metastasis of lung cancer remains unknown. To observe metastasis of lung cancer cells by imaging technology, we introduced a near‐infrared fluorescent protein, iRFP720, into a bone‐seeking subclone established from lung cancer cells, HARA‐B4 cells. The anchorage‐independent growth of these cells was then evaluated by colony formation assays. We also compared cancer cell tropism to bone tissue with HARA‐B4 cells in the presence or absence of CD24 by cell adhesion assays. To clarify the role of CD24 in bone metastasis, we intracardially injected CD24‐knockdown HARA‐B4 cells into mice and monitored metastasis through detection of iRFP720 using an in vivo imaging system. CD24‐knockdown HARA‐B4 cells in vitro showed reduced anchorage‐independent growth and cancer cell tropism to bone. Bone metastasis was diminished in mice inoculated with CD24‐knockdown HARA‐B4 cells, which was rescued by add‐back of CD24 in cells. Our findings indicate that iRFP720 is effective for in vivo imaging analysis of bone metastasis and that downregulation of CD24 suppresses bone metastasis of lung cancer cells. These findings collectively indicate that CD24 may be considered a promising new therapeutic candidate for the prevention of bone metastasis of lung cancer.

CD24 expression as a marker for predicting clinical outcome and invasive activity in uterine cervical cancer

CD24, a small heavily glycosylated mucin-like glycosylphosphatidylinositol-anchored cell surface protein, plays an important role in the carcinogenesis of various human malignancies. However, its function in cervical cancer remains unclear. The aim of the present study was to evaluate the expression of CD24 clinicopathologically and to analyze its functional behavior biologically in cervical cancer. A total of 117 uterine cervical cancer tumors were immunohistochemically analyzed using a CD24 monoclonal antibody on paraffin blocks. We also examined whether CD24 enhanced the invasive activity or the Akt, ERK, NF-κB and MMP activity in a uterine cervical cancer cell line (CaSki) by a western blot analysis. The patients with enhanced CD24 expression had a higher rate of advanced clinical stage (50 vs. 16.5%, p<0.01), lymph node metastasis (34.6 vs. 14.3%) and lymphovascular involvement (65.4 vs. 20.4%, p=0.01), and a poor overall and disease-free survival (5-year survival rate: 62 vs. 86%, p=0.03). CD24 overexpression in CaSki cells resulted in activation of Cell Signaling proteins, including Akt, ERK, NF-κB and MMP-9. An invasion assay showed that CD24 overexpression in CaSki cells led to increased invasion ability. The CD24 overexpression also increased mRNA expression of Slug but not Snail. Moreover, the CD24 overexpression also decreased expression of E-cadherin and increased N-cadherin protein levels. Increased expression of CD24 may be associated with tumor progression and prognosis in patients with uterine cervical cancer. CD24 expression may therefore be used not only as a prognostic marker in uterine cervical cancer, but also as a target for the development of new therapeutic approaches.

Blood Vessel Maturation by Disintegrin in Oxygen-Induced Retinopathy

PURPOSE

Although Arg-Gly-Asp (RGD) motif-containing disintegrins are associated with integrin inhibition and the activation of various biological processes, little is known about the role of RGD motif-containing disintegrin in vascular development and remodeling. We therefore investigated the role of RGD-containing disintegrin in vascular remodeling in oxygen-induced retinopathy (OIR) mouse model.

MATERIALS AND METHODS

EGT022, an RGD-containing disintegrin originated from human a disintegrin and metalloproteinase 15 (ADAM15), was used to investigate the role of the disintegrin in vascular development in OIR mouse model. To analyze the functional effects of EGT022 on retinal vascular development, the immunohistochemistry on mouse retinas after fluorescein isothiocyanate (FITC) perfusion was conducted and the vessel integrity was examined using modified Mile's permeability assay.

RESULTS

EGT022 was able to reduce overall retinopathy scores by 75%, indicating its efficacy in retinal microvessel maturation stimulation. Pericyte coverage was greatly stimulated by EGT022 treatment in OIR mouse model. EGT022 was also effective to significantly improve blood vessel integrity.

CONCLUSIONS

RGD-containing disintegrin EGT022 stimulated vascular maturation in OIR mouse model. Experimental results suggest that EGT022 is useful for treatments to improve ischemia in nonproliferative diabetic retinopathy (NPDR), the early stage of diabetic retinopathy.

Increased expression of CD24 is associated with tumor progression and prognosis in patients suffering osteosarcoma

OBJECTIVE

As a small heavily glycosylated mucin-like glycosyl-phosphatidylinositol-anchored cell surface protein, CD24 plays an important role in carcinogenesis of various human malignancies. However, its involvement in osteosarcoma is still unclear. The aim of this study was to investigate the expression pattern and the clinical significance of CD24 in human osteosarcoma.

METHODS

CD24 mRNA and protein expression levels were, respectively, detected by RT-PCR and Western blot assays using 30 pairs of osteosarcoma and noncancerous bone tissues. Then, immunohistochemistry was performed to analyze the association of CD24 expression in 166 osteosarcoma tissues with clinicopathological factors or survival of patients.

RESULTS

CD24 expression at mRNA and protein levels were both significantly higher in osteosarcoma tissues than those in corresponding noncancerous bone tissues (both P < 0.001). In addition, CD24 protein was positively expressed in 129 of 166 (77.7 %) osteosarcoma specimens with a cytoplasmic and membraneous staining, and also increased in the osteosarcoma specimens with advanced clinical stage (P = 0.01) and positive distant metastasis (P = 0.005). The univariate and multivariate analyses showed that osteosarcoma patients with high CD24 expression had poorer overall and disease-free survival, and high CD24 expression was an independent prognostic factor for both overall and disease-free survival.

CONCLUSION

The aforementioned findings offer convincing evidence for the first time that the increased expression of CD24 is correlated with tumor aggressiveness and tumor metastasis of osteosarcoma, and this molecule is an independent prognostic marker for osteosarcoma patients.