Xiaofang Xu

Microarray-based analysis: identification of hypoxia-regulated microRNAs in retinoblastoma cells.

Hypoxia is an essential feature of retinoblastoma and contributes to poor prognosis and resistance to conventional therapy. MicroRNAs (miRNAs) are small non-coding RNAs involved in a wide variety of biological processes, including cell differentiation, proliferation, death and metabolism. However, the relationship between hypoxia and the expression of miRNAs in retinoblastoma is not well understood. In this study, we aimed to analyze the pattern of miRNA expression in a retinoblastoma cell line under hypoxic conditions and to identify the miRNAs regulated by hypoxia, as well as their possible functions. miRNA expression profiling in retinoblastoma cells (HXO-RB44) under normal and hypoxic conditions was assessed by microarray techniques. The differentially expressed miRNAs were subjected to bioinformatic analyses to predict and categorise the key miRNAs and their target genes. A quantitative real-time RT-PCR approach was used to validate their expression. A Cell Counting kit was used to evaluate the functional significance of miR-181b in RB cell proliferation. There were 46 miRNAs that changed expression more than 2-fold in response to hypoxia (34 up-regulated and 12 down-regulated). We identified a cluster of miRNAs that includes miR-181b, miR-125a-3p, miR-30c-2, miR-497 and miR-491-3p as hypoxia-regulated miRNAs (HRMs) in retinoblastoma cells, of which miR-181b was the most typically differentially expressed miRNA under hypoxic conditions. Functionally, these HRMs are involved in apoptosis, cell adhesion, cell proliferation and mRNA processing, all processes that associate closely with the hypoxia response of cancer cells. Additionally, we found that administration of miR-181b inhibitor can suppress proliferation of retinoblastoma cells. These findings provide the first evidence that miRNAs play an important role in the hypoxia response of retinoblastoma cells. MiR-181b, the most typically up-regulated miRNA may aid in future clinical intervention of retinoblastoma.

Inhibition of retinoblastoma in vitro and in vivo with conditionally replicating oncolytic adenovirus H101.

PURPOSE To determine the therapeutic effect of oncolytic adenovirus H101 on retinoblastoma in vitro and in vivo. METHODS The expression of coxsackievirus-adenovirus receptor (CAR) in human retinoblastoma cell line HXO-RB(44) was determined by RT-PCR, Western blot, immunofluorescence, and immunocytochemistry staining. Appropriate multiplicity of infection was determined using flow cytometry in retinoblastoma cells with green fluorescent protein-expressing adenovirus (AdGFP). The viability of HXO-RB(44) cells treated with H101 or AdGFP was measured using a cell counting kit-8-based procedure. Viral proliferation in vitro was measured by end point dilution titration and real-time PCR. Cell cycle and apoptotic activity of HXO-RB(44) were analyzed by flow cytometry. NOD-SCID mice bearing retinoblastoma xenografts were treated with intratumoral injection of H101, AdGFP, or PBS. Tumor volume and survival time were recorded. Immunohistochemistry for adenoviral fiber protein and Western blot for adenoviral Hexon protein of retinoblastoma xenografts were performed to evaluate H101 virus replication in vivo. RESULTS HXO-RB(44) cells expressed CAR and were sensitive to adenoviral infection. HXO-RB(44) cells treated with H101 had reduced cell viability compared with AdGFP-treated cells (P < 0.01). Abundant replication of H101 in HXO-RB(44) cells resulted in G(2)/M-phase arrest and finally tumor cell lysis, but the apoptosis pathway was not activated. Tumor-bearing mice treated with H101 had reduced tumor burdens and prolonged survival times compared with PBS and AdGFP controls (both P < 0.01). Immunohistochemical and Western blot examination revealed widespread replication of H101 within the tumor. CONCLUSIONS These results suggest that H101 effectively inhibits the growth of retinoblastoma cells in vitro and in mice and may serve as a novel therapy for retinoblastoma.

Radiation‐inducible human tumor necrosis factor‐related apoptosis‐inducing ligand (TRAIL) gene therapy: a novel treatment for radioresistant uveal melanoma

Uveal melanoma (UM) is one of the most therapy‐resistant cancers. Radiotherapy is the preferred treatment for most cases of UM. However, some UM cells, such as the SP6.5 or OM431 cell lines, are relatively radioresistant. In this study, we attempted to improve the current UM therapy using an adenovirus radio‐inducible gene therapy system. The antitumor adenovirus was constructed by inclusion of the radiation‐inducible early growth response gene 1 (EGR1) promoter and the anticancer tumor necrosis factor‐related apoptosis‐inducing ligand (TRAIL) gene. We demonstrated that the UM SP6.5 and OM431 cell lines were susceptible to the TRAIL‐induced antitumor effect. TRAIL expression was enhanced in the adenovirus containing EGR1/TRAIL (Ad‐ET) treatment group by radiotherapy, whereas Ad‐ET significantly increased cell death and apoptosis caused by radiotherapy. In mice bearing xenograft tumors, apoptotic cells were detected in pathological tumor sections. Adenovirus Ad‐ET combined with radiation therapy significantly inhibited tumor growth compared with the other treatment groups (P < 0.01). Our findings indicate that radioresponsive gene therapy has the potential to be a more effective and specific therapy for UM because the therapeutic gene can be spatially or temporally controlled by exogenous radiation.

Functional significance of B7-H1 expressed by human uveal melanoma cells

B7-H1, a recently described B7 family member, has been reported to negatively regulate T-cell function in most cancer cells. In this study, we sought to investigate B7-H1 expression in four uveal melanoma (UM) cells (OCM1, SP6.5, OM431 and VUP) to determine the functional significance of B7-H1 expression in T-cell immune response. Using flow cytometry (FCM), we demonstrated that SP6.5 cells had high B7-H1 protein expression, while the other three UM cell lines had none. However, all four UM cell lines expressed B7-H1 mRNA, as confirmed by reverse transcription-polymerase chain reaction. In co-culture experiments using B7-H1-expressing UM cells with T-cells, FCM to determine CD69 expression in T-cells revealed that SP6.5 cell-related B7-H1 inhibited T-cell activation. This effect was eliminated by B7-H1-targeted RNA interference. An Annexin V/PI double staining assay further showed that B7-H1 expressed by SP6.5 cells did not increase the apoptosis of T-cells, though it was found in a variety of other solid tumors. In conclusion, all the UM cell lines constitutively expressed B7-H1 mRNA, while B7-H1 protein was expressed at different levels. UM-related B7-H1 expression negatively regulated T-cell immune response through the inhibition of T-cell activation, and not through the promotion of T-cell apoptosis. This provides new insight into anti-tumor immunity against B7-H1-expressing UM cells.

Hypoxia-induced miR-181b enhances angiogenesis of retinoblastoma cells by targeting PDCD10 and GATA6

Previous findings showed that miR-181b is upregulated under hypoxic conditions in retinoblastoma cells. Since hypoxia is a common feature of retinoblastoma that affects tumor progression as well as tumor therapy, in the present study, we investigated the regulatory mechanism of miR-181b under hypoxic conditions, and examined the role of miR-181b in retinoblastoma responses to hypoxia (chemoresistance and angiogenesis) and possible downstream genes. The level of hypoxia-inducible factor-1α (HIF-1α) and miR-181b was detected to examine the link between them. Tube formation and cell cytotoxicity assays were used to clarify the effects of miR-181b on hypoxic responses of retinoblastoma cells. Bioinformatics analysis was performed to predict potential targets of miR-181b and western blotting was used to verify these targets. The results showed a significantly increased expression of HIF-1α in hypoxia-treated retinoblastoma cells. Downregulation of HIF-1α using a small-interfering RNA (siRNA) knockdown technology did not decrease the expression of miR-181b. Through gain- and loss-of-function studies, miR-181b was demonstrated to significantly stimulate the ability of capillary tube formation of endothelial cells. Programmed cell death-10 (PDCD10) and GATA binding protein 6 (GATA6) were identified as the target genes of miR‑181b. To the best of our knowledge, results of the present study provide the first evidence that miR-181b was upregulated by hypoxia in retinoblastoma in an HIF-1α-independent manner. miR-181b increased tumor angiogenesis of retinoblastoma cells. Additionally, miR-181b exerts its angiogenic function, at least in part, by inhibiting PDCD10 and GATA6. Thus, it is a new potentially useful therapeutic target for retinoblastoma.

The role of Bax and Bcl-2 in gemcitabine-mediated cytotoxicity in uveal melanoma cells.

Gemcitabine (GEM), a new cytotoxic agent, was shown to be effective against uveal melanoma (UM) which is noted for its resistance to chemotherapy. In this study, we found the different sensitivities to GEM in UM cell lines and identified apoptotic cell death as the cause of GEM cytotoxicity. Both UM cell lines showed an increase in Bax protein levels and activation of cleaved Caspase 3. Additionally, SP6.5 cells showed a gradual increase in Bcl-2 expression over time, whereas VUP cells showed almost none. After interfering in the expression of Bcl-2, the sensitivity to GEM was obviously enhanced in SP6.5 cells. These results suggest that an increase in Bax plays a crucial role in apoptotic cell death induced by GEM in the absence of p53. Moreover, inhibition of Bcl-2 expression can efficiently enhance the cytotoxic effect of, and sensitivity to, GEM in UM cells.

Ocular Complications of Human Immunodeficiency Virus Infection in Eastern China

PURPOSE To investigate ocular complications in patients with HIV/AIDS in eastern China during the time of highly active antiretroviral therapy (HAART). DESIGN Prospective study. METHODS This study was carried out from August 1, 2009 to July 31, 2010. Recruited HIV/AIDS patients underwent a series of surveys and ophthalmologic and laboratory examinations (including CD4 level) at enrollment. RESULTS In this study, all 787 HIV/AIDS patients (1574 eyes) had a history of HAART. Of these patients, 28.72% (95% CI = 0.26-0.32) had a history of systemic disease and 26.30% (95% CI = 0.23-0.29) had ocular complications. Of these ocular complications, cytomegalovirus retinitis (CMVR) had the highest prevalence (10.6%, 83/787) and ocular microangiopathy had the second-highest prevalence (9.4%, 74/787). Among the patients with CMVR, 16.9% (14/83) suffered from immune recovery uveitis (IRU). Furthermore, 3.4% (27/787) of the recruited AIDS patients had neuro-ophthalmologic disorders. The mean logMAR visual acuity of the group with ocular complications was 0.47 ± 0.64, which was significantly different from the asymptomatic group (0.17 ± 0.39, P < .001). The median CD4 T-cell count of the group with ocular complications is 43 cells/μL, which was significantly different from the asymptomatic group (116.5 cells/μL, P < .001). CONCLUSIONS The study shows a high rate of treatable ocular complications among patients with HIV/AIDS in eastern China. HIV/AIDS treatment programs in China must be prepared to identify ocular complications and refer patients to the correct treatment facilities.

Let-7b overexpression leads to increased radiosensitivity of uveal melanoma cells.

Uveal melanoma (UM) is an intraocular malignant tumor in adults that is characterized by rapid progression and recurrence. Irradiation has become the primary therapy for UM patients who are not candidates for surgery. However, after large-dose fraction irradiation treatment, some patients undergo subsequent enucleation because of radiotherapy-related complications. This situation has raised concerns on how to optimize the effectiveness of radiation treatment. Recent investigations of microRNAs are changing our understanding of UM tumor biology and are helping to identify novel targets for radiotherapy. The radioresistant UM cell lines OM431 and OCM1 were selected and exposed to irradiation, and let-7b was found to be downregulated after exposure. We then confirmed that let-7b mimics could inhibit UM growth both in vitro and in vivo. More specifically, transfection with let-7b mimics markedly resensitized OCM1 and OM431 cells to irradiation by reducing the population of S-phase cells. Cyclin D1 plays a vital role in cell cycle arrest, which is induced by let-7b overexpression. Cyclin D1 is also a target of let-7b and its expression is suppressed by upregulation of let-7b. Collectively, our results indicate that let-7b overexpression can in turn downregulate cyclin D1 expression and enhance the radiosensitivity of UM through cell cycle arrest. Let-7b could serve as a marker for radiosensitivity and could enhance the therapeutic benefit of UM cell irradiation.

Combined Treatment with an Oncolytic Adenovirus and Antitumor Activity of Vincristine against Retinoblastoma Cells

Treatment trends of retinoblastoma (RB) have gradually evolved from eye enucleation and external radiation to local treatment. Combined treatment with an oncolytic virus and chemotherapy is currently a new method in RB treatment. To investigate the therapeutic effect of oncolytic adenovirus SG600 in combination with vincristine (VCR) on retinoblastoma in vitro, the cell viability, cell cycle effects and apoptotic activity of HXO-RB44 cells treated with SG600, VCR or SG600 plus VCR were measured using a cell counting kit-8-based procedure and flow cytometry. Western blot analysis for Akt, p-Akt, p-p53 and p-Rb protein was performed to investigate the underlying mechanisms of combined therapy. The combination therapy exerted a synergistic antitumor effect via a type of G2/M and S phase arrest rather than the induction of apoptosis. The combination of VCR and SG600 further reduced Akt phosphorylation compared with cells treated with VCR alone, suggesting that SG600 could overcome chemoresistance, perhaps by down-regulating Akt in RB cells. An increase in the expression of p-p53 and decrease in p-Rb expression in HXO-RB44 after co-treatment might be associated with cell cycle block. Western blot examination revealed that VCR might enhance SG600 replication. These results suggest that viro-chemo combination therapy is a feasible and potentially promising approach for the treatment of retinoblastoma.

Investigation of vasculogenic mimicry in sebaceous carcinoma of the eyelid.

Purpose:  Vasculogenic mimicry (VM) is a newly proposed pattern of tumour angiogenesis that has been identified in some malignancies and is associated with poor prognosis. The purpose of this study was to investigate whether sebaceous carcinomas of the eyelid exhibit VM and to determine whether these fluid‐conducting patterns are associated with clinicopathologic features, the number of microvessels and the levels of endothelial growth factor (VEGF) and matrix metalloprotease‐2 (MMP‐2) in tumours.