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.
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-RasGAP(317-326) peptide which has the potential to specifically sensitize tumor cells to cytostatic agents.


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-RasGAP(317-326) administration. mTHPC was added to the cultures at a concentration of 0.04microg/ml and 0.10microg/ml, respectively, 24h before laser light illumination at 652nm (3J/cm(2), 40mW/cm(2)). TAT-RasGAP(317-326) was added to the cultures immediately after light delivery at a concentration of 20microM. 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 0.04microg/ml mTHPC resulted in a significantly higher apoptosis rate in the presence of TAT-RasGAP(317-326) than without in H-meso-1 cells (p<0.05) but not in fibroblasts. In contrast, 1.0microg/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-RasGAP(317-326) 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.


CONCLUSIONS
TAT-RasGAP(317-326) 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.
Pittet
Olivier
O
Division of Thoracic Surgery, University of Lausanne, Centre Hospitalier Universitaire Vaudois, 1011 Lausanne, Switzerland.
Petermann
David
D
Michod
David
D
Krueger
Thorsten
T
Cheng
Cai
C
Ris
Hans-Beat
HB
Widmann
Christian
C
D017209:Apoptosis / Q000187:drug effects*; D002470:Cell Survival; D005347:Fibroblasts / Q000187:drug effects; D020690:GTPase-Activating Proteins / Q000138:chemical synthesis / Q000627:therapeutic use*; D006801:Humans; D008652:Mesoporphyrins / Q000627:therapeutic use*; D008654:Mesothelioma / Q000188:drug therapy* / Q000473:pathology; D010446:Peptide Fragments / Q000138:chemical synthesis / Q000627:therapeutic use*; D010455:Peptides / Q000627:therapeutic use; D010778:Photochemotherapy; D017319:Photosensitizing Agents / Q000627:therapeutic use*; D014407:Tumor Cells, Cultured
D020690:GTPase-Activating Proteins; D008652:Mesoporphyrins; D010446:Peptide Fragments; D010455:Peptides; D017319:Photosensitizing Agents; C525242:TAT-RasGAP(317-326); C072269:temoporfin