VWC2 (von Willebrand factor C domain containing 2), also known as Brorin, is a secreted cysteine knot protein with emerging roles in bone metabolism, cancer regulation, and neurological function. Primary Function: VWC2 functions as an antagonist of activin signaling rather than BMP signaling as previously hypothesized 1. The protein promotes bone formation by inhibiting activin A-induced Smad2 phosphorylation in osteoblasts and is present in bone matrix at osteoblasts and osteocytes 1. Mechanism: VWC2 binds the βA subunit of activin within the TGF-β superfamily and reverses activin A's inhibitory effects on osteoblast cell growth, differentiation, and mineralization 1. In dental pulp tissues, VWC2 acts as a BMP antagonist with reduced expression associated with aberrant intrapulpal calcifications in enamel renal syndrome 2. Disease Relevance: Reduced VWC2 expression correlates with colorectal cancer progression, with DNA hypermethylation-induced downregulation mediated by SUMO1-modified DNMT1 promoting malignancy 3. Conversely, elevated plasma VWC2 levels exhibit protective effects against lung adenocarcinoma (OR=0.85) 4. Clinical Significance: VWC2 is identified as a candidate biomarker associated with cognitive outcomes in stroke patients, obesity-related language development, and metabolic syndrome-related cognitive decline, with lifestyle interventions modulating its association with cognitive function 5, 6, 7. VWC2 represents a potentially druggable therapeutic target for cancer and neurological conditions.