Anti-cancer IAP antagonists promote bone metastasis: a cautionary tale

Area of Science:

• Oncology
• Cell Biology
• Bone Biology

Background:

• The bone microenvironment is a complex system supporting bone homeostasis.
• Tumor metastasis to bone is facilitated by alterations in this microenvironment, often involving osteoclast activity.
• Inhibitor of apoptosis (IAP) proteins are crucial in regulating cell survival, and their antagonists are emerging anti-cancer therapeutics.

Purpose of the Study:

• To review the connection between IAP antagonists, the alternative NF-κB pathway, osteoclasts, and bone metastasis.
• To highlight potential risks of IAP antagonists, including increased bone metastasis and osteoporosis.
• To emphasize the need for further investigation into these effects during drug development.

Main Methods:

• Literature review focusing on preclinical and clinical data.
• Analysis of the role of IAP antagonists in modulating NF-κB signaling pathways (classical and alternative).
• Examination of the impact of IAP antagonists on osteoclast function and bone remodeling.

Main Results:

• IAP antagonists activate the alternative NF-κB pathway, a less-studied mechanism compared to their effect on the classical pathway.
• Preclinical data suggest IAP antagonists may increase the risk of bone metastasis and promote osteoporosis.
• IAPs' role in regulating osteoclast activity and bone resorption is implicated.

Conclusions:

• IAP antagonists, while promising cancer therapies, warrant careful evaluation for their effects on bone health.
• Understanding the interplay between IAP antagonists, the alternative NF-κB pathway, and osteoclasts is critical.
• Further research and clinical monitoring are necessary to mitigate risks associated with bone metastasis and osteoporosis during IAP antagonist therapy.