Popovtzer et al. reported that cetuximab targeted with AuNPs for head and neck cancer enhanced the effects of radiotherapy and significantly affected tumor growth, and the mechanism of radiation enhancement was associated with increased apoptosis (TUNEL assay), inhibition of angiogenesis (based on CD34 levels), and decreased repair mechanisms (proliferating cell nuclear antigen staining). Here, PCNA is linked to neoplasm.