Disruption of Cenpj, a centriole biogenesis regulator, diminishes oral cancer susceptibility through p53-dependent DNA-damage repair and apoptosis pathways

Mutations in centrosomal P4.1-associated protein (CPAP; Gene: CENPJ), a microtubule-bindingcentriolar protein, can lead to microcephaly (MCP) in humans. While CPAP dysfunction is knownto cause centrosome aberrations and genomic instability, its impact on tumor initiation andprogression is largely unknown. Our recent reports showed that CPAP regulates endocyticvesicular transport function and epidermal growth factor receptor (EGFR) homeostasis andsignaling dynamics. CPAP depletion endows human oral squamous cell carcinoma (OSCC) celllines with epithelial-mesenchymal transition (EMT) phenotype, and enhanced EGFR-dependentinvasive and tumorigenic properties in vitro and in a xenotransplant model, respectively. Here, weemployed a mouse model with hypomorphic allele of Cenpj , which shows dwarfism andmicrocephaly phenotype (MCP mice), to determine the impact of CPAP function on EGFR levelsand chemical carcinogen-induced oral tumorigenesis. Similar to human OSCC cell lines,fibroblasts, and tongue epithelium organoids from MCP mice exhibited defective vesiculartransport function and markedly increased EGFR protein levels. However, to our surprise, MCPmice exhibited diminished susceptibility to 4-Nitroquinoline 1-oxide (4NQO) -induced oraltumorigenesis as compared to their wild-type counterparts. Epithelial cell proliferation at all stagesof tumor progression and the eventual tumor burden were profoundly lower in MCP mice. Tonguefibroblasts and epithelial organoids treated with DNA damage-inducing agents were used todetermine the molecular mechanism(s) of reduced tumor susceptibility of Cenpj hypomorphicmice. These cells from MCP mice were highly susceptible to DNA damage and showed higheractivation of p53 and DNA-damage repair (DDR)- and apoptotic- pathways. For instance, gamma-H2AX and cleaved caspase-3 levels, and apoptotic death were significantly higher in cells withhypomorphic allele of Cenpj as compared to cells with WT allele. Our ongoing studies are focusedon determining how CPAP-mediated EGFR homeostasis and centriolar function impactgenotoxicity and epithelial cell transformation at different stages of oral tumorigenesis. Overall,our findings, for the first time, show a role for critical centriole biogenesis and microcephaly-associated protein in tumor initiation and progression under genotoxic stress and are expected tohelp design novel targeted therapies for OSCC.