PCNA and neoplasm: Also, immunohistochemical analysis in tumor tissues demonstrated a significant reduction of proliferating cell nuclear antigen (PCNA) cells and microvessel density (MVD) along with a significant increase of terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL)-positive apoptotic cells (Fig. 2B, 2C) by TTAC-0001 treatment.