Figure 3. Expression of Sept9_ i2 is downregulated in breast tumors.

Mammary gland tissues and breast tumors belonging to different sub-types were immunolabeled, as indicated, with a pan Sept9 antibody or antibodies specific for Sept9_i1 or for Sept9_i2, validated for immunohistochemistry (see Supplementary Fig. S2). Inserts correspond to zoomed boxed areas; (a) endothelial cell labeling, (b) epithelial and carcinoma cell labeling. Nuclei were stained blue. While both normal tissue and tumors are positive with pan-Sept9 antibodies, isoform-specific antibodies reveal differential expression. Sept9_i1 is increased in a subpopulation of tumors. An example of a positive and a negative tumor is presented in an Her2+ and LumB tumors, respectively. Sept9_i2 antibody shows strong cytosolic labeling in normal tissue only. Sept9_i2 nuclear staining observed in tumors was not specific (see Supplementary Fig. S2). N: normal; Her2+: ErbB2 overexpressing; LumB: luminal B. White horizontal bars represent 100 μm and 60 μm in images and zoom inserts, respectively.