The PTEN tumour suppressor plays critical roles in inhibiting cell proliferation, adhesion and migration through downregulation of the PI3K-AKT pathway. SIPL1 is a novel PTEN‑negative regulator (PTEN-NR) that contributes to PTEN inactivation during tumorigenesis. However, whether SIPL1 plays a role in inhibiting PTEN function in the process of cell adhesion and migration remains unclear. The aim of this study was to investigate this possibility using CHO-K1 cells, and western blotting, qPCR analyses and microscopy. Results showed that the overexpression of SIPL1 in CHO-K1 cells decreased the amount of PTEN protein. The downregulation was not caused by an obvious reduction in PTEN mRNA levels or ubiquitin-dependent protein degradation. Nonetheless, the reduction was functional, as SIPL1 overexpression increased the activation of AKT under serum‑starved conditions, promoting CHO-K1 cell proliferation in an AKT‑dependent manner. Furthermore, SIPL1 increased the migration and attachment of CHO-K1 cells. Taken together, the evidence suggested that SIPL1 promotes AKT activation by decreasing the amount of PTEN protein in CHO-K1 cells, thereby promoting cell proliferation and migration.