Effect of the TAT-RasGAP(317-326) peptide on apoptosis of human malignant mesothelioma cells and fibroblasts exposed to meso-tetra-hydroxyphenyl-chlorin and light

Journal of Occupational & Environmental Medicine. 2007 Jul 27;88(1):29-35. Epub 2007 May 1. [Link]

Olivier Pitteta, David Petermanna, David Michodb, Thorsten Kruegera, Cai Chenga, Hans-Beat Risa, and Christian Widmannb

aDivision of Thoracic Surgery, University of Lausanne, Centre Hospitalier Universitaire Vaudois, 1011 Lausanne, Switzerland
bDepartment of Physiology and Cellular Biology and Morphology, University of Lausanne, Switzerland

Received 12 January 2007; revised 27 March 2007; accepted 24 April 2007. Available online 1 May 2007.


Background: 5,10,15,20-Tetrakis(m-hydroxyphenyl)chlorin (mTHPC)-mediated photodynamic therapy (PDT) has shown insufficient tumor selectivity for the treatment of pleural mesothelioma. Tumor selectivity of mTHPC-PDT may be enhanced in the presence of the TAT-RasGAP317–326 peptide which has the potential to specifically sensitize tumor cells to cytostatic agents.

Materials and methods: H-meso-1 and human fibroblast cell cultures, respectively, were exposed to two different mTHPC doses followed by light delivery with and without TAT-RasGAP317–326 administration. mTHPC was added to the cultures at a concentration of 0.04 μg/ml and 0.10 μg/ml, respectively, 24 h before laser light illumination at 652 nm (3 J/cm2, 40 mW/cm2). TAT-RasGAP317–326 was added to the cultures immediately after light delivery at a concentration of 20 μM. The apoptosis rate was determined by scoring the cells displaying pycnotic nuclei. Cell viability was measured by using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay.

Results: Light delivery associated with 0.04 μg/ml mTHPC resulted in a significantly higher apoptosis rate in the presence of TAT-RasGAP317–326 than without in H-meso-1 cells (p < 0.05) but not in fibroblasts. In contrast, 1.0 μg/ml mTHPC and light resulted in a significantly higher apoptosis rate in both H-meso-1 cells and fibroblasts as compared to controls (p < 0.05) but the addition of TAT-RasGAP317–326 did not lead to a further significant increase of the apoptosis rate of both H-meso-1 cells and fibroblasts as compared to mTHPC and light delivery alone.

Conclusion: TAT-RasGAP317–326 selectively enhanced the effect of mTHPC and light delivery on H-meso-1 cells but not on fibroblasts. However, this effect was mTHPC dose-dependent and occurred only at a low sensitizer dose.

Keywords: Photodynamic therapy; mTHPC; Mesothelioma; Apoptosis; H-Meso-1 cell cultures; TAT-RasGAP317–326