Gene expression profile in murine 3T3 fibroblasts photosensitised by a tetracationic porphyrin

The interest regarding the study of cell death in the context of photodynamic therapy (PDT) is very deep. Phenomena of apoptosis, autophagia and necrosis in PDT-treated cells have been widely observed, the specific results can depend on the treatment parameters and cell line used. In order to identify key genes expressed in response to photosensitisation after short term exposure to porphyrins and visible light, a study on the transcriptome of murine 3T3 fibroblast cell cultures was carried out through the microarray approach. Toward this aim we studied the effect induced by a tetracationic meso-substituted porphyrin ( C12) in this cell line, employing different time incubations and photosensitiser concentrations. The subcellular localisation of the photosensitiser was investigated on cells which had been incubated with 0.1 µM C12 for 1 h before and after 1 min of irradiation with white light at a fluence rate of 10 mW/cm2. Under these conditions a limited cell mortality occurs (about 5%), hence these samples are suitable for studing initial gene expression. The analysis of microarray data allowed the identification of 531 differentially expressed genes in treated cells with respect to controls, 67 of which resulted overexpressed. Among these, some genes are involved in cell proliferation and differentiation, such as Wnt11 (7.5 fold change) whose expression in mouse is activated during artery morphogenesis and endoderm development processes. Interestingly, one of the overexpressed genes was found to be the Tumour suppressor candidate 1 (Tusc1), 3-fold more expressed in photosensitised fibroblasts. In order to confirm and validate these data, and to study the time-course accumulation of mRNAs and the dose-dependent effect of porphyrin C12, a detailed characterization of the expression profiles in murine fibroblasts subjected to photosensitisation will be carried out by quantitative real-time PCR (qRT-PCR).