HBP1 (HMG-box transcription factor 1) is a transcriptional repressor that functions as a potent cell cycle inhibitor through direct DNA binding to the sequence 5'-TTCATTCATTCA-3' 1. HBP1 regulates cell cycle progression by activating or repressing cell cycle genes including CDKN2A, CDKN1A, and CCND1, while antagonizing oncogenic transcription factors like TCF4, LEF1, and MYC in the Wnt/β-catenin pathway 1. The protein interacts with retinoblastoma protein (RB) to enhance histone H1.0 promoter activity, linking cell cycle control to chr7 remodeling during cell differentiation 2. Beyond cell cycle control, HBP1 exhibits tissue-specific functions. In endometrial stromal cells, HBP1 directly activates IGFBP1 expression and enhances progesterone receptor transcriptional activity, promoting decidualization essential for embryo implantation 3. In the pancreas, HBP1 upregulation protects against acute pancreatitis-induced inflammatory injury by maintaining acinar homeostasis 4. HBP1 demonstrates tumor suppressor characteristics, with reduced expression in several cancer types 1. However, in pancreatic cancer with concurrent KRAS mutations, HBP1 paradoxically facilitates progression of pancreatic intraepithelial neoplasia (PanIN) lesions 4. Multiple mechanisms suppress HBP1 in cancer cells, including microRNA regulation (miR-155, miR-17-92, miR-29a) and PI3K/AKT pathway-mediated inhibition of both transcription and direct phosphorylation 1.