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D. B. Burr, S. A. Molina, D. Low, M. R. Katz, J. Ragsdale, R. Allbaugh, A. Rankin, D. J. Takemoto; Treatment With Connexin 46 siRNA Suppresses Growth of Xenograft Human Y79 Retinoblastoma Tumors in vivo. Invest. Ophthalmol. Vis. Sci. 2010;51(13):1575.
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Retinoblastoma, like many solid tumors, has an early hypoxic survival stage allowing tumor cells to have a growth advantage over normal tissue. We have found that when compared to the lens, a normally hypoxic tissue, tumors with a hypoxic component express a specific gap junction protein, connexin 46 (Cx46). Cx46 expression has been shown in human Y79 retinoblastoma cells. The present study was carried out to determine if treatment with Cx46 siRNA, a drug that can repress synthesis of the Cx46 protein, would initiate Y79 cell death and prevent xenograft retinoblastoma tumor formation in vivo.
Mixed sex nude mice (nu/nu) received 1x107 human Y79 retinoblastoma cells in 0.5 ml of a 1:1 mixture of matrigel basement membrane matrix and Iscove’s culture medium supplemented with 20% FBS, subcutaneously. Once a solid tumor mass was palpable, treatment with Cx46 (30ug) or a negative non-silencing control siRNA was initiated. Intratumor injections were given every 2 days for a total of 10 treatments. Prior to each treatment, the tumor volume (TV) was calculated for each mouse from the recorded caliper measurements, longest (L) and shortest (W). Final TV and weights were assessed on the excised tumors. Western blot analysis was performed to evaluate expression of Cx46 in the tumors treated with Cx46 siRNA or negative control siRNA.
Cx46 siRNA treated Y79 tumors had a reduced TV when compared to the tumors of mice receiving the negative control siRNA, 19 mm3 and 350 mm3, respectively. A 7-fold knockdown of Cx46 expression was shown in the tumors of Cx46 siRNA treated mice compared to the tumors of negative control siRNA mice on western blot analysis.
Knockdown of Cx46 with siRNA had an antitumor effect on human Y79 retinoblastoma tumors in the nude mouse model. The results suggest Cx46 siRNA may potentially be a useful antitumor drug in the future treatment of retinoblastoma.
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