Fig 1: Validation of the p16INK4A antibody from Santa-Cruz (sc-1661).(A) Evaluation of the specificity of the p16INK4A antibody, sc-1661, by Western blotting, using GST-tagged, full length, recombinant, human p16INK4A protein (rp16INK4A). Molecular weight markers were used to determine size of detected gel products (A; lane M). Lane 1, 100 ng of rp16INK4A; Lane 2, 10 ng rp16INK4A. A single band of the expected molecular weight (including GST-tag) is apparent. (B) Rat brain cortex (lane 1), liver (lane 2), optic nerve (lane 3) and retina (lane 4) samples probed for p16INK4A protein, using sc-1661. None of the four tissues under investigation unambiguously express p16INK4A protein. Labelling for ß-actin (house-keeping gene product) is also shown. (C) The antibody was further tested against retina (lanes 1–3) and optic nerve (lanes 4–6) samples obtained from three different rats. The presence of p16INK4A protein is not detectable in any sample. (D, E) In formalin-fixed, paraffin-embedded tissue sections of cervical adenocarcinoma, incubation with sc-1661, identifies so-called ‘block’ or ‘diffuse’ immunolabelling of ductal (D) and epithelial (E) tissue with a high signal-to-background, as compared to adjacent tissue (arrow). Scale bar = 30 µm.