Phosphorylation of FADD is critical for sensitivity to anticancer drug-induced apoptosis

Area of Science:

• Cell Biology
• Molecular Oncology
• Cancer Therapeutics

Background:

• FAS-associated death domain (FADD) protein phosphorylation at Ser194 occurs during the G2/M cell cycle phase.
• Anticancer drugs can induce apoptosis in prostate cancer cells, a process potentially modulated by FADD activity.

Purpose of the Study:

• To investigate the role of FADD phosphorylation at Ser194 in paclitaxel-induced apoptosis in LNCaP and DU145 prostate cancer cell lines.
• To elucidate the involvement of the MEK kinase 1 (MEKK1)/mitogen-activated protein kinase kinase (MKK) 7/c-jun NH2-terminal kinase (JNK) pathway in FADD phosphorylation and drug-induced apoptosis.

Main Methods:

• Cell cycle arrest at G2/M was induced using paclitaxel in LNCaP and DU145 cells.
• FADD phosphorylation at Ser194 was assessed following drug treatment.
• Inhibition of JNK activation was achieved using SP600125 or dominant-negative mutants of MEKK1 and MKK7.
• MEKK1 expression levels and FADD mutant (Ser194-->Ala) effects were evaluated.

Main Results:

• Paclitaxel treatment led to G2/M arrest and FADD phosphorylation at Ser194.
• Inhibition of MEKK1/MKK7/JNK pathway components reduced FADD phosphorylation.
• Paclitaxel pretreatment upregulated MEKK1, enhancing JNK activation and apoptosis induced by other drugs.
• Overexpression of a non-phosphorylatable FADD mutant (Ser194-->Ala) abolished MEKK1 upregulation and synergistic effects on apoptosis.

Conclusions:

• FADD phosphorylation at Ser194 is essential for amplifying chemotherapy-induced apoptosis in prostate cancer.
• Phosphorylated FADD influences pathways both upstream and downstream of MEKK1/MKK7/JNK signaling.
• FADD Ser194 phosphorylation is closely linked to chemosensitivity in prostate cancer cells.