DNTT and neoplasm: Instead, the increased growth of PHD3-silenced G55 tumours could be attributed to a combination of decreased tumour cell apoptosis as assessed with TdT-mediated dUTP nick end labeling (TUNEL) staining (Fig. 2h,i) and increased cell proliferation as determined by the proliferation marker phospho-histone H3 (Fig. 2j,k).