Effects of different forms of prostate specific antigen on prostate cancer cell invasion / by Andrew Philip Cumming

Abstract

Prostate cancer (PCa) is one of the most common cancers in males around the world. Prostate-specific antigen (PSA) is a serine protease that is secreted at high levels by prostate epithelial cells and most prostate cancer cells. It is thought that this enzyme is involved in prostate cancer cell invasion. This study aimed to test the effects of enzymatically active PSA and inactive forms of PSA on prostate cancer cell invasion. PSA is transcribed with a 17 amino acid secretory "pre" sequence and a 7 amino acid latency-conferring "pro" sequence. A deletion mutant lacking the "pro" region of the full-length preproPSA gene was used to create the prePSA gene, in the hopes that enzymatically active PSA would be formed upon cleavage of the "pre" sequence. Full length preproPSA cDNA and prePSA cDNA were each inserted into plasmids that allowed for inducible expression of the PSA genes under the control of the insect hormone derivative, ponasterone A (PonA). DU-145 subclones were created with the ability to inducibly produce preproPSA (DU-pERV3 C3 ppPSA) and prePSA (DU-pERV3 C3 prePSA). The growth properties, migratory abilities, and invasiveness of these cells were assayed. The same properties were tested with exogenous active PSA added to DU-145 cells. Exogenous PSA induced little change in growth, invasion or migration. However, there was a slight decrease in the invasion of DU-145 cells when using commercially isolated enzymatically active PSA. DU-pERV3 C3 ppPSA transfected cells showed increased invasion compared to control cells. Conversely, DUpERV3 C3 prePSA transfected cells showed decreased invasion and migration compared to control cells. This study suggests that active PSA decreases the invasiveness of DU-145 cells, whereas the inactive zymogen form increases cellular invasion.