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Updated: Jan 28, 2026
A Sensitive Method to Quantify Senescent Cancer Cells
Published on: August 2, 2013
IAP Antagonists Selectively Eliminate Therapy-Induced Senescent Cancer Cells via TNFα-Independent Apoptosis
Hiroaki Ochiiwa1,2, Takeshi Wakasa1,2, Yuki Kataoka1,2
1Department of Molecular Cancer Biology, Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka, Japan.
Abstract:
Therapy-induced senescence (TIS) is a state in which cancer cells enter growth arrest following chemotherapy. TIS cancer cells influence the tumor microenvironment through their senescence-associated secretory phenotype and independently acquire stem-like properties, both of which contribute to increased aggressiveness and tumor relapse. Here, we show that AZD5582 and AT406, potent antagonists of cellular inhibitor of apoptosis proteins 1 and 2 (cIAP1 and cIAP2) and X-linked inhibitor of apoptosis protein (XIAP), selectively eliminated HCT116 and RKO cells that had undergone senescence following treatment with a chemotherapeutic agent such as trifluridine, camptothecin, or doxorubicin. This elimination occurred via apoptosis associated with caspase 8 activation. These TIS cancer cells produced and secreted tumor necrosis factor α (TNFα); however, the selective cytotoxicity of IAP antagonists toward TIS cells was unexpectedly largely TNFα-independent. Consistently, the same IAP antagonists sensitized cancer cells treated with nutlin-3a, which induces senescence without TNFα production. Depletion of both cIAP1 and XIAP recapitulated the selective cytotoxicity against both TIS and nutlin-3a-induced senescent cancer cells. At physiological concentrations, TNFα sensitized non-senescent, proliferating cancer cells, but not TIS and nutlin-3a-induced senescent cancer cells, to apoptosis in the presence of IAP antagonists. Collectively, these findings suggest that IAP antagonists could serve as effective concomitant agents to TIS-inducing chemotherapy that promotes TNFα secretion within tumors, functioning not only as TNFα-independent senolytics but also as potentiators of TNFα-mediated apoptosis in adjacent non-senescent, proliferating cancer cells.
Insights
Potent inhibitors of inhibitor of apoptosis proteins (IAPs) selectively kill chemotherapy-induced senescent cancer cells via apoptosis. These IAP antagonists offer a novel senolytic strategy, independent of TNFα, to combat tumor relapse.
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.
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