Cep55 overexpression promotes genomic instability and tumorigenesis in mice

High expression of centrosomal protein CEP55 has been correlated with clinico-pathological parameters across multiple human cancers. Despite significant in vitro studies and association of aberrantly overexpressed CEP55 with worse prognosis, its causal role in vivo tumorigenesis remains elusive. Here, using a ubiquitously overexpressing transgenic mouse model, we show that Cep55 overexpression causes spontaneous tumorigenesis and accelerates Trp53+/- induced tumours in vivo. At the cellular level, using mouse embryonic fibroblasts (MEFs), we demonstrate that Cep55 overexpression induces proliferation advantage by modulating multiple cellular signalling networks including the PI3K/AKT pathway. Notably, the Cep55 overexpressing MEFs demonstrate high level of mitotic chromosomal instability (CIN) due to stabilized microtubules. Interestingly, Cep55 overexpressing MEFs have a compromised Chk1-dependent S-phase checkpoint, causing increased replication speed and DNA damage, resulting in a prolonged aberrant mitotic division. Importantly, this phenotype was rescued by pharmacological inhibition of Pi3k/Akt or expression of mutant Chk1 (S280A), that is insensitive to regulation by active AKT, in Cep55 overexpressing cell. Collectively, our data demonstrates causative effects of deregulated Cep55 on genome stability and tumorigenesis which have potential implications for tumour initiation and therapy.