RGD-FasL Induces Apoptosis of Pituitary Adenoma Cells

Abstract

This study was to investigate the cytotoxic effects on pituitary adenoma cell lines GH3/MMQ/AtT20 induced by RGD-FasL and the underlying mechanism. Fas/DcR3 mRNAs were detected by RT-PCR and their surface expressions were measured by flow cytometry. Cytotoxicity exerted by RGD-FasL on tumor cells was measured with MTT assay and the induced apoptosis was determined by agarose gel electrophoresis. The cell cycle and apoptosis was assessed by flow cytometry with PI staining. The expressions of caspase8/9/3, Bcl-2, RANKL and JNK2 were detected by Western blotting. Approximately 13.7% of GH3 cells, 25.5% of MMQ cells, 22.2% of AtT20 cells express Fas, while 23.9% of GH3 cells, 24.1% of MMQ cells, 4.6% of AtT20 cells express DcR3. The cytotoxic effects of FasL/RGD-FasL on tumor cells were all taken in a dose-dependent manner. Cell lines MMQ/AtT20 showed the same sensitivity to RGD-FasL as to FasL, while cell line GH3 was less sensitive to RGD-FasL. The cell cycle analysis indicated that RGD-FasL could inhibit cells in G0/G1 phase and G2/M phase. In MMQ and AtT20 cells treated with RGD-FasL, the AI was not significantly different from that treated with FasL, while in GH3 cells treated with RGD-FasL, the AI was lower than that treated with FasL. The expressions of caspase-8/9/3, RANKL and JNK2 were increased while that of Bcl-2 was decreased after treatment with RGD-FasL, suggesting that RGD-FasL induces apoptosis through caspase activation. We concluded that RGD-FasL could possibly be considered as a novel therapeutical candidate for the treatment of pituitary adenomas.

Glossary

FasL

Fas ligand

DcR

decoy receptor

RGD

tripeptide sequence Arg-Gly-Asp

RGD-FasL

fusion protein of RGD and Fas ligand

TNF

tumor necrosis factor

RT-PCR

reverse transcription PCR

mAb

monoclonal antibody

DISC

death-inducing signaling complex

OD

optical density

AI

apoptosis index

ANOVA

analysis of variance

JNK

c-Jun N-terminal kinase

FITC

fluorescein isothiocyanate

PAGE

polyacrylamide gel electrophoresis

CRD

cysteine-rich domains