EJ, CP, JM, CX and AT contributed to the design and completed experiments. DMSO controls are shown, with SEM represented by error bars and individual experimental repeats plotted. A representative western image of this result is also shown (assessments were performed, and values for the SR10067 differences between cell lines are shown. (Scale bars?=?250?m (inset image scale bars?=?50?m) Using multicellular spheroids of the MCF7 and MCF7-HER2 cell lines, we were able to compare the expression of hypoxia response proteins across a 3D cellular structure through immunohistochemistry. Once again, whilst the SR10067 expression of HIF-1 was comparable between cell lines, HIF-2 protein levels were significantly higher in the context of HER2 overexpression (values and Pearsons correlation to HER2 expression in the cell lines data set are shown HER2-overexpressing SR10067 breast cancer cell lines display increased sensitivity to HIF-2 inhibition Having established a role for HER2 overexpression in driving an exacerbated hypoxic response and the increased expression of HIF-2, we investigated whether HER2-positive cell lines were more sensitive to specific inhibition of HIF-2. The growth of MCF7 and MCF-HER2 cell lines was compared in response to HIF-2-specific knock-down by siRNA. Western blotting was used to confirm the HIF-2-specific effect of two siRNA treatments; a single siRNA targeting HIF-2 (siRNA #4) and a pool of four individual HIF-2 targeting siRNAs (SMARTpool siRNA). Both treatments reduced HIF-2 to less than 10% of the level seen in untreated cells, mock transfected cells or cells treated with non-targeting siRNA; no discernible effect on HIF-1 was seen (Fig.?7a). In addition, these siRNAs were also able to reduce the levels of HIF-2 induced by hypoxia to levels below the detectable limit in MCF7-HER2 cells (Fig.?7b). Transfection of MCF7 and MCF7-HER2 cell lines with these siRNAs in sulforhodamine B (SRB) growth assays performed in normoxia or hypoxia over 5?days demonstrated an increased sensitivity in the HER2-overexpressing cell line to HIF-2 knock-down (Fig.?7c). MCF7-HER2 cells showed reduced cell density after treatment with either HIF-2-specific siRNA in normoxia or hypoxia, whilst MCF7 cells were generally unaffected showing reduced cell density with just one of the NMYC siRNAs only in normoxia. MCF7-HER2 were significantly more sensitive to siRNA treatment than MCF7 cells in all treatment categories, indicating an increased dependence on HIF-2 in HER2-overexpressing cells in normoxia and hypoxia. Open in a separate window Fig. 7 HER2-overexpressing cell lines are more sensitive to HIF-2 inhibition. a Western blot showing siRNAs knock-down of HIF-2 in MCF7-HER2 in normoxia. SiRNa knock-down was performed with 25?M of four different siRNAs as well as 5C100?M of SMARTpool, combined siRNAs. Protein level was reduced to
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