{"type": "root", "children": [{"type": "p", "children": [{"type": "t", "text": "\n Cellular retinoic acid‐binding protein II (CRABP2) is a high‐affinity intracellular chaperone for all‐trans retinoic acid (RA) that plays a critical role in mediating RA signaling. When RA binds to CRABP2 in the cytoplasm, the protein undergoes a ligand‐induced conformational change that exposes a nuclear localization signal, thereby promoting its rapid translocation into the nucleus. Once inside the nucleus, CRABP2 “channels” RA directly to its cognate retinoic acid receptor (RAR), potentiating RAR‐mediated transcriptional activation and downstream gene expression events that regulate cell differentiation, growth arrest, and apoptosis (see"}, {"type": "fg", "children": [{"type": "fg_f", "ref": "1"}]}, {"type": "t", "text": "and."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "2"}]}, {"type": "t", "text": ""}]}, {"type": "t", "text": "\n \n "}, {"type": "p", "children": [{"type": "t", "text": "\n In several cancer models—including head and neck squamous cell carcinoma, pancreatic ductal adenocarcinoma and breast cancer—CRABP2 has emerged as a key mediator of sensitivity to RA. In these contexts, epigenetic inactivation or cytoplasmic sequestration of CRABP2 is associated with reduced RAR activation, resistance to RA‐induced growth inhibition, and poor clinical outcomes. Re‐expression or proper nuclear localization of CRABP2 restores RA responsiveness and leads to growth‐inhibitory and differentiative effects (see"}, {"type": "fg", "children": [{"type": "fg_f", "ref": "3"}]}, {"type": "t", "text": ", and."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "5"}]}, {"type": "t", "text": ""}]}, {"type": "t", "text": "\n \n "}, {"type": "p", "children": [{"type": "t", "text": "\n Moreover, CRABP2 function is integrated into broader hormonal and cellular differentiation programs. For example, its expression in estrogen receptor–positive breast cancer cells is modulated by estrogen and RAR signaling, establishing a link between estrogen receptor status and RA sensitivity. In preadipocytes, down‐regulation of CRABP2 is an essential step that diminishes RA signaling to allow adipocyte differentiation to proceed, illustrating its regulatory importance in diverse differentiation pathways"}, {"type": "fg", "children": [{"type": "fg_f", "ref": "6"}]}, {"type": "t", "text": "and."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "7"}]}, {"type": "t", "text": " Furthermore, in studies of triple‐negative breast cancer, a nuclear localization of CRABP2 correlates with RA responsiveness, whereas alternative RA‐binding proteins that retain RA in the cytoplasm (such as FABP5) drive pathways linked to cell survival and invasion."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "8"}]}, {"type": "t", "text": ""}]}, {"type": "t", "text": "\n \n "}, {"type": "p", "children": [{"type": "t", "text": "\n Together, these findings underscore the central role of CRABP2 as a determinant of RA bioavailability and signaling specificity. By directing RA to RAR in the nucleus, CRABP2 influences gene expression programs that control cell cycle progression, differentiation, and tumor suppression. Its function, regulated at multiple levels including ligand binding, posttranslational modifications, and epigenetic control, establishes CRABP2 as a promising biomarker and potential therapeutic target in cancers and other diseases where RA signaling is dysregulated.\n "}]}, {"type": "rg", "children": [{"type": "r", "ref": 1, "children": [{"type": "t", "text": "Anuradha S Budhu, Noa Noy "}, {"type": "b", "children": [{"type": "t", "text": "Direct channeling of retinoic acid between cellular retinoic acid-binding protein II and retinoic acid receptor sensitizes mammary carcinoma cells to retinoic acid-induced growth arrest."}]}, {"type": "t", "text": " "}, {"type": "i", "children": [{"type": "t", "text": "Mol Cell Biol (2002)"}]}, {"type": "t", "text": " DOI: "}, {"type": "a", "children": [{"type": "t", "text": "10.1128/MCB.22.8.2632-2641.2002"}], "href": "https://doi.org/10.1128/MCB.22.8.2632-2641.2002"}, {"type": "t", "text": " PMID: "}, {"type": "a", "children": [{"type": "t", "text": "11909957"}], "href": "https://pubmed.ncbi.nlm.nih.gov/11909957"}]}, {"type": "r", "ref": 2, "children": [{"type": "t", "text": "Richard J Sessler, Noa Noy "}, {"type": "b", "children": [{"type": "t", "text": "A ligand-activated nuclear localization signal in cellular retinoic acid binding protein-II."}]}, {"type": "t", "text": " "}, {"type": "i", "children": [{"type": "t", "text": "Mol Cell (2005)"}]}, {"type": "t", "text": " DOI: "}, {"type": "a", "children": [{"type": "t", "text": "10.1016/j.molcel.2005.03.026"}], "href": "https://doi.org/10.1016/j.molcel.2005.03.026"}, {"type": "t", "text": " PMID: "}, {"type": "a", "children": [{"type": "t", "text": "15866176"}], "href": "https://pubmed.ncbi.nlm.nih.gov/15866176"}]}, {"type": "r", "ref": 3, "children": [{"type": "t", "text": "Marilia F Calmon, Rodrigo V Rodrigues, Carla M Kaneto, et al. "}, {"type": "b", "children": [{"type": "t", "text": "Epigenetic silencing of CRABP2 and MX1 in head and neck tumors."}]}, {"type": "t", "text": " "}, {"type": "i", "children": [{"type": "t", "text": "Neoplasia (2009)"}]}, {"type": "t", "text": " DOI: "}, {"type": "a", "children": [{"type": "t", "text": "10.1593/neo.91110"}], "href": "https://doi.org/10.1593/neo.91110"}, {"type": "t", "text": " PMID: "}, {"type": "a", "children": [{"type": "t", "text": "20019841"}], "href": "https://pubmed.ncbi.nlm.nih.gov/20019841"}]}, {"type": "r", "ref": 4, "children": [{"type": "t", "text": "Sonal Gupta, Dipankar Pramanik, Radha Mukherjee, et al. 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