The effect of epithelial-mesenchymal transition (EMT) on the response of prostate cell lines to cancer drugs.

Abstract

Prostate cancer is the most prevalent cancer diagnosed amongst males in the western world. Evidence suggests that tumours secrete inflammatory signals to induce a metastatic process of the cancer through a mechanism called Epithelial-Mesenchymal transition (EMT). EMT is a natural process that is observed during fetal development, wound healing and other important cellular processes in the body. During this process epithelial cells suppress their epithelial abilities to gain more mesenchymal abilities. Transforming growth factor beta (TGFβ) activates the EMT pathway which sets of a domino effect of various signals, activation of transcription factors and proteins. One important effect of the transcription factors activated during EMT is suppression of E-Cad (CDH1) and activation of N-Cad (CDH2). The progression of EMT can therefore be monitored via the changes in cadherin expression which has commonly been referred to as the Cadherin switch. Melphalan (MP) is a well-known anticancer drug with DNA damaging potential. However, MP’s biggest disadvantages is that it insufficiently penetrates the cell membrane sufficiently because of its lipophobic properties. Melphalan flufenamide, or Melflufen (MF), is a drug that was developed in order to enhance the specificity of Melphalan. The main difference between the two drugs lies in a conjugated peptide group that is attached to MF, rendering it more lipophilic and allowing it to diffuse easily through the cell membrane. Inside the cytoplasm MF is converted to MP by the removal of the peptide group by peptidase such as aminopeptidase N (CD13). A connection between drug resistance and progression of cancer cells during EMT has previously been established. In this context, TGFβ has been shown to inhibit apoptosis and a similar link has been established with respect to some of the transcription factors influencing EMT.The aim of this study was to evaluate the effect of the cancer drugs Melphalan, Melflufen, and the experimental drug DRUG2 on prostate cancer cells in vitro and investigate the interfering action of EMT forced by TGFβ treatment.Dosage response was performed on cell lines PZHPV7, CAHPV10, DU145, 22RV1, RWPE1 and PWR1E. EMT markers were mapped in these cell lines using Flow Cytometry. Of these cell lines, CAHPV10 cancer cell line showed the most prominent response to TGFβ treatment with a significant increase in N-Cadherin expression. In addition, there was a major increase in the expression of aminopeptidase (CD13) in the same cell line compared to the others.In conclusion, drug sensitivity does not change post TGFβ treatment for five days in the cell lines; PZHPV7, CAHPV10, DU145 and RWPE1. Some of the cell lines in this study already display some mesenchymal properties prior TGFβ treatment which could explain why they didn’t respond to TGFβ.