Knockdown of Phosphoprotein Enriched in Astrocytes, 15kDa (PEA-15) Enhances Cell Cycle Progression in 5637 Bladder Cancer Cells

The DNA Damage Response (DDR) pathway regulates the cellular processes of apoptosis, cell cycle arrest, and DNA repair. If it is perturbed, DNA mutations can cause cells to turn malignant. Phosphoprotein Enriched in Astrocytes, 15 kDa (PEA-15) possibly modulates the DDR pathway by sequestering ERK to the cytoplasm and preventing CDC25 from activating CDK1/2. Since PEA-15 is amplified in bladder cancer (BC) cells, we investigated how knockdown of PEA- 15 in BC cell line 5637 affects the cell cycle and migration. 5637 wild-type (shNT) and PEA-15 knockdown (shNT) BC cell lines were used. Protein expressions for CDK1, CDK2, P-27, and PEA-15 between 0 and 24-hours were compared using western blots. An XTT assay measured the proliferation rate 24 and 48 hours after epidermal growth factor (EGF) treatment. A wound-healing assay measured the migration rate 18 hours after EGF treatment. There was no significant difference in CDK1 and P-27 protein expression between the wild-type and knockdown cell lines. However, CDK2 expression increased over time in the wild- type cell lines and decreased in the knockdown cell lines. Furthermore, PEA-15 knockdown increases cell proliferation rate and migration rate for BC cells treated with EGF. Together, the data establish that PEA-15 has a possible functional interaction with CDK2 at the G1 and S cell cycle checkpoints. Knockdown of PEA-15 increased cell cycle progression, proliferation, and migration in BC cell line 5637. Therefore, the presence of PEA-15 would indicate better prognosis for BC patients. This information can be used as a future prognostic tool or for development of new therapies