Retinoblastoma protein 94 kDa (RB94) (RB94)

Retinoblastoma protein 94 kDa (RB94) is a truncated version of the full-length 110 kDa retinoblastoma protein (pRb), characterized by the deletion of the first 112 amino acids at the N-terminus (Xu et al., 1994). This structural modification renders RB94 significantly more potent than the wild-type protein in suppressing tumor growth and inducing apoptosis across a wide range of human cancer cell lines (Zhang et al., 2000). Biologically, RB94 functions as a tumor suppressor by binding and sequestering E2F transcription factors, which prevents the transition of cells from the G1 to the S phase of the cell cycle (Gopalan et al., 2002). Unlike the full-length protein, RB94 is less susceptible to inactivation by cyclin-dependent kinase (CDK) phosphorylation, allowing it to maintain a constitutively active state in many cancer environments. In therapeutic contexts, RB94 is primarily utilized in gene therapy approaches, such as adenoviral-mediated delivery (Ad-RB94) or liposomal complexes (SGT-94), where it has demonstrated selective cytotoxicity toward malignant cells while sparing normal cells (Zhang et al., 2003). Clinical investigations have focused on its application in treating refractory solid tumors, particularly bladder and lung cancers, where it serves as both a replacement for lost RB function and a pro-apoptotic stimulus (ClinicalTrials.gov, NCT00004062). The molecule is a critical tool for restoring cell cycle control in tumors where the RB pathway is dysregulated or the RB1 gene is mutated.

Other names

p94RBN-terminal truncated retinoblastoma proteinRB94 gene productTruncated pRb

RB94 acts as a constitutively active tumor suppressor by lacking the N-terminal regulatory domain (amino acids 1-112) of the full-length retinoblastoma protein (p110), which allows it to bypass certain phosphorylation-mediated inactivation mechanisms (Zhang et al., 2000). It binds and sequesters E2F transcription factors with high affinity, thereby preventing the expression of genes required for the S-phase of the cell cycle and triggering rapid apoptosis specifically in malignant cells (Gopalan et al., 2002).