Mitoxantrone triggers immunogenic prostate cancer cell death via p53-dependent PERK expression.

Abstract

BACKGROUND:

Mitoxantrone (MTX) is a synthetic compound used as a second line chemotherapeutic drug for prostate cancer. It has been reported to trigger immunogenic cell death (ICD) in animal model studies, but the underlying mechanism is not fully understood yet, especially not in prostate cancer cells.

METHODS:

ICD was determined by assessing the release of damage-associated molecular patterns (DAMPs) in the prostate cancer-derived cell lines LNCaP, 22RV1 and PC-3. Short hairpin RNAs (shRNAs) were used to knock down target gene expression. Phagocytosis was assessed using a dual labeling technology in dendric cells co-cultured with cancer cells. The PERK gene promoter was cloned for dual luciferase assays. Chromatin immunoprecipitation (ChIP) was used to determine p53 protein-DNA binding activity. Immunocompetent mice and murine RM-1 prostate cancer cells were used for vaccination experiments.

RESULTS:

MTX treatment induced typical characteristics of DAMP release, including increased cell surface exposure of calreticulin (CALR), and extracellular release of ATP and high mobility group box-1 (HMGB1) protein. MTX also enhanced phagocytosis by dendritic cells. Moreover, MTX treatment increased eukaryotic initiation factor 2α (eIF2α) S51 phosphorylation, which was reduced when PERK and GCN2 were silenced using shRNAs. In addition, PERK or GCN2 silencing significantly reduced MTX-induced release of DAMPs in vitro and anti-tumor immunity in vivo. MTX treatment also resulted in dendritic cell activation in mice, which was attenuated when PERK or GCN2 were silenced in cancer cells used for vaccination. Further analysis revealed that PERK and GCN2 expression was enhanced by MTX treatment, of which PERK, but not GCN2, was enhanced via a p53-dependent mechanism.

CONCLUSION:

MTX triggers ICD by activating eIF2α via PERK/GCN2 upregulation in prostate cancer cells. MTX-induced PERK expression upregulation depends on the p53 pathway, while that of GCN2 requires further investigation.

• Authors: Changlin Li, Hui Sun, Wei Wei, Qiuzi Liu, Yinglei Wang, Ying Zhang, Fuming Lian, Fangchao Liu, Chenchen Li, Kaicheng Ying, Hang Huo, Zhi Qi, Benyi Li
• Journal: Cellular oncology (Dordrecht) (Cell Oncol (Dordr)) Vol. 43 Issue 6 Pg. 1099-1116 (Dec 2020) ISSN: 2211-3436 [Electronic] Netherlands
• PMID: 32710433 (Publication Type: Journal Article)

Chemical References

• Alarmins
• Eukaryotic Initiation Factor-2
• Tumor Suppressor Protein p53
• Mitoxantrone
• EIF2AK4 protein, human
• PERK kinase
• Protein Serine-Threonine Kinases
• eIF-2 Kinase

Topics

• Alarmins (metabolism)
• Animals
• Cell Death (drug effects)
• Cell Line, Tumor
• Dendritic Cells (drug effects, metabolism)
• Eukaryotic Initiation Factor-2 (metabolism)
• Gene Expression Regulation, Neoplastic (drug effects)
• Humans
• Male
• Mice, Inbred C57BL
• Mitoxantrone (pharmacology)
• Phagocytosis (drug effects)
• Phosphorylation (drug effects)
• Prostatic Neoplasms (genetics, immunology, pathology)
• Protein Serine-Threonine Kinases (genetics, metabolism)
• Protein Stability (drug effects)
• Transcription, Genetic (drug effects)
• Tumor Suppressor Protein p53 (metabolism)
• Up-Regulation (drug effects)
• eIF-2 Kinase (genetics, metabolism)