IAP Antagonists Selectively Eliminate Therapy-Induced Senescent Cancer Cells via TNFα-Independent Apoptosis

Area of Science:

• Oncology
• Cellular Biology
• Pharmacology

Background:

• Therapy-induced senescence (TIS) is a cancer cell response to chemotherapy, leading to growth arrest.
• TIS cells contribute to tumor aggressiveness and relapse through their secretory phenotype and stem-like properties.
• Targeting TIS cells presents a potential strategy to overcome treatment resistance.

Purpose of the Study:

• To investigate the efficacy of IAP antagonists (AZD5582 and AT406) in eliminating TIS cancer cells.
• To elucidate the mechanism of selective cytotoxicity of IAP antagonists towards senescent cells.
• To explore the potential of IAP antagonists as adjunct therapy with chemotherapy.

Main Methods:

• Treatment of HCT116 and RKO cells with chemotherapeutic agents to induce senescence.
• Administration of IAP antagonists (AZD5582, AT406) to senescent and non-senescent cancer cells.
• Assessment of apoptosis, caspase 8 activation, and TNFα dependency.
• Depletion of cIAP1 and XIAP to confirm IAP antagonist effects.
• Evaluation of TNFα's role in sensitizing cells to IAP antagonists.

Main Results:

• IAP antagonists AZD5582 and AT406 selectively eliminated TIS cancer cells via apoptosis, involving caspase 8 activation.
• The senolytic effect was largely independent of TNFα production by TIS cells.
• IAP antagonists sensitized cells to nutlin-3a-induced senescence, which lacks TNFα production.
• TNFα sensitized non-senescent cells but not senescent cells to IAP antagonist-induced apoptosis.

Conclusions:

• IAP antagonists act as effective senolytics, selectively eliminating TIS cancer cells through a TNFα-independent mechanism.
• These agents can potentiate TNFα-mediated apoptosis in adjacent proliferating cancer cells.
• IAP antagonists represent a promising therapeutic strategy when combined with TIS-inducing chemotherapy.