Assessment of a Novel MCF-7 Based Bioassay:Sensitivity to Pharmaceuticals and Environmental Pollutants

Conventional bioassays are designed on the basis of one stress activated transcription factor working in isolation, which is a limitation since in reality there are often several factors leading to a response. The novel MCF-7 based bioassay differs from conventional cell based bioassays by the use of the Cyp2a5 promoter construct that contains multiple response elements. This allows the bioassay to be responsive to more than one form of stress, hence, determination whether a substance should be considered toxic or not is wider than the conventional bioassays. The aim of the project was to assess the sensitivity of the MCF-7 based bioassay to pharmaceuticals and common environmental pollutants with the focus on oxidtive stress. The used chemicals were cadmium chloride ( CdCl2) and doxorubicin (DOX). From the cell viability assay a suitable concentration range was decided for the chemical treatment performed after the transfection of Cyp2a5 recombinant construct. The EC50 of the CdCl2 and DOX in comparison with the EC50 of the reference compound tBHQ for the oxidative stress responsive pathway shows that the bioassay is far less sensitive to CdCl2 and more sensitive to DOX compared to tBHQ. On the other hand, the EC50 of CdCl2 is far below lethal concentrations, which indicate that the bioassay can detect concentrations that will give a biologial response. The MCF-7 based bioassay confirmed that CdCl2 and DOX induce the Nrf2 dependent pathway, which is responsive to oxidative stress. The results indicate the potential of the MCF-7 based bioassay as an effective tool for toxicity screening of polycyclic aromatic and oxidative stress inducing agents.