Galectin-3: a novel antiapoptotic molecule with a functional BH1 (NWGR) domain of Bcl-2 family

Area of Science:

• Molecular Biology
• Cancer Research
• Cell Biology

Background:

• Galectin-3 is a beta-galactoside-binding protein implicated in tumor progression and metastasis.
• The role of galectin-3 in chemoresistance, particularly to platinum-based drugs like cisplatin, requires further elucidation.

Purpose of the Study:

• To investigate the effect of galectin-3 expression on cisplatin-induced apoptosis in human breast carcinoma cells.
• To determine the specific molecular mechanisms by which galectin-3 influences apoptosis and chemoresistance.

Main Methods:

• Utilized human breast carcinoma BT549 cells with varying galectin-3 expression levels.
• Assessed poly(ADP-ribose) polymerase (PARP) degradation and apoptosis following cisplatin treatment.
• Analyzed the expression of Bcl-2 family proteins (Bcl-2, Bcl-X(L), Bax).
• Investigated the role of the NWGR motif in galectin-3's antiapoptotic function through amino acid substitution.

Main Results:

• Galectin-3 expression inhibited cisplatin-induced PARP degradation and apoptosis in BT549 cells.
• This inhibition occurred without significant changes in Bcl-2, Bcl-X(L), or Bax protein levels.
• A specific substitution (glycine to alanine) within the conserved NWGR motif of galectin-3 abrogated its antiapoptotic activity.
• Evidence suggests galectin-3 mediates apoptosis resistance via a cysteine protease pathway.

Conclusions:

• Galectin-3 confers resistance to cisplatin-induced apoptosis in breast cancer cells.
• The NWGR motif within galectin-3 plays a critical role in its antiapoptotic function, acting independently of the Bcl-2 family.
• These findings highlight galectin-3 as a potential therapeutic target for overcoming chemoresistance in breast cancer.