Moonlighting Role of PEDF in Breast Cancer

Abstract

Background: Breast cancer is the leading cause of death among females in developed countries. Although the implementation of screening tests and the development of new therapies has increased the probability of remission, relapse rates still remain high. Numerous studies have indicated the connection between cancer initiating cells and slow cellular cycle cells, identified by their capacity to retain long labelling (LT+). Methods: We have designed a transgenic protein consisting in the C-terminal part of this protein, which acts by blocking endogenous PEDF in culture cell assays. Present work is based in doses-response in vitro assays as well as flow cytometry analysis of surface markers and cell cycle kinetic study of the tumour initiating cells.Results: In this study we show that this type of cells is present not only in cancer cell lines but also in cancer cells from patients with metastatic and advanced stage tumours. We also present new assays showing how stem cell self-renewal modulating proteins, such as PEDF, can modify the properties, expression of markers, and carcinogenicity of cancer stem cells. This protein has been involved in self-renewal in adult stem cells and has been described as anti-tumoral because of its anti-angiogenic effect. However, we show that PEDF enhances resistance in breast cancer patient cells in vitro culture by favoring a slow cellular cycle population (LT+). The PEDF signalling pathway could be a useful tool for controlling cancer stem cells self-renewal, and therefore control patient relapse. Conclusions: We demonstrate that it is possible to interfere with the self-renewal capacity of cancer stem cells, induce anoikis in vivo, and reduce resistance against Docetaxel treatment in cancer patient cells in vitro culture. We have also demonstrated that this PEDF modified protein produces a significant decrease in cancer stem cell markers. All these properties make this protein a potential application in clinical cancer therapies via co-administration with chemotherapy for relapse cancer treatment.