1 December 2003 Activation of Heat Shock Protein 70 Promoter with meso-Tetrahydroxyphenyl Chlorin Photodynamic Therapy Reported by Green Fluorescent Protein In Vitro and In Vivo
Soumya Mitra, Evan M. Goren, John G. Frelinger, Thomas H. Foster
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Abstract

Cellular responses to photodynamic therapy (PDT) include induction of heat shock proteins (HSP). We examined meso-tetrahydroxyphenyl chlorin (mTHPC) PDT–mediated HSP activation in EMT6 cells stably transfected with a plasmid containing the gene for green fluorescent protein (GFP) driven by an hsp70 promoter. mTHPC incubation induced concentration-dependent GFP expression. Irradiation of cells exposed to a sensitizer concentration that induced a slight increase in GFP and no loss of cell viability resulted in fluence-dependent GFP accumulation. In response to drug only and to PDT, GFP levels increased to a maximum of four- to five-fold above control levels with increasing drug or fluence and then decreased at higher doses. A trypan blue–exclusion assay confirmed that decreased GFP levels in both cases were due to a loss of cell viability. For initial evaluation in vivo, HSP70/GFP–transfected EMT6 tumors were grown in BALB/c mice and subjected to mTHPC-PDT with a fluence of 1 J/cm2. Six hours after PDT, GFP fluorescence was imaged in these tumors through the intact skin in vivo. These results indicate that sublethal doses of mTHPC-PDT stimulate GFP expression under the control of an hsp70 promoter and illustrate the potential of noninvasively monitoring reporter protein fluorescence as a measure of molecular response to PDT.

Soumya Mitra, Evan M. Goren, John G. Frelinger, and Thomas H. Foster "Activation of Heat Shock Protein 70 Promoter with meso-Tetrahydroxyphenyl Chlorin Photodynamic Therapy Reported by Green Fluorescent Protein In Vitro and In Vivo," Photochemistry and Photobiology 78(6), 615-622, (1 December 2003). https://doi.org/10.1562/0031-8655(2003)078<0615:AOHSPP>2.0.CO;2
Received: 12 May 2003; Accepted: 1 September 2003; Published: 1 December 2003
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