PRB1 (proline-rich protein BstNI subfamily 1) is a salivary protein-coding gene located on chromosome 12 that encodes basic proline-rich proteins (PRPs) involved in salivary composition and oral biology. PRB1 is one of six closely linked PRP genes with well-characterized polymorphisms affecting salivary protein variants 1. The gene product is subject to post-transcriptional regulation, with expression influenced by factors including heat shock and N-acetyl glucosamine exposure 2. At the cellular level, PRB1-encoded retinoblastoma protein (pRB1) functions as a critical tumor suppressor governing G1/S cell cycle checkpoint control. Phosphorylated pRB1 (pRB1) accumulates at the restriction point during G1/S transition and is regulated by CDK4/6-mediated phosphorylation 3. pRB1 levels are tightly controlled through ubiquitin-proteasome degradation; MYC-driven upregulation of E3 ligase KLHL42 promotes pRB1 degradation, conferring resistance to CDK4/6 inhibitor therapy in multiple cancer types 4. Disease relevance extends to cancer biology, where zinc supplementation restores decreased pRB1 expression in zinc-depleted breast cancer cells, re-activating tumor suppression pathways 5. Additionally, CDK4/6 inhibitors restoring pRB1 phosphorylation show therapeutic potential in hereditary hemorrhagic telangiectasia by blocking pathological endothelial cell proliferation 3. Clinical significance lies in leveraging pRB1 status as a biomarker for CDK4/6 inhibitor sensitivity and in therapeutic strategies targeting MYC-driven pRB1 degradation.