HSP90 as an emerging barrier to immune checkpoint blockade therapy

Area of Science:

• Oncology
• Immunology
• Molecular Biology

Background:

• Immunotherapy, particularly immune checkpoint inhibitors, has improved cancer patient survival.
• Many patients do not respond to or relapse after immunotherapy, necessitating novel therapeutic strategies.
• Heat shock protein 90 (HSP90) is a molecular chaperone crucial for protein stability and function in various cellular pathways.

Purpose of the Study:

• To investigate the role of HSP90 in regulating immune checkpoint molecules in cancer.
• To determine if targeting HSP90 can enhance the efficacy of existing immunotherapies.

Main Methods:

• Drug screening and functional assays were performed to identify HSP90's role in cancer cells.
• The effect of HSP90 on the stability of nuclear transcription factor STAT1 was assessed.
• Gene expression of immune checkpoint molecules (IDO1 and PD-L1) was analyzed.
• In vivo studies utilized mouse models of pancreatic cancer to evaluate combined HSP90 inhibition and PD-1 blockade therapy.

Main Results:

• HSP90 was identified as a key regulator of STAT1 protein stability across various cancer types.
• HSP90 inhibition led to decreased expression of immune checkpoint molecules IDO1 and PD-L1.
• Targeting HSP90 significantly enhanced the efficacy of PD-1 blockade therapy in preclinical pancreatic cancer models.

Conclusions:

• HSP90 plays a critical role in maintaining the stability of proteins that drive immune evasion in cancer.
• HSP90 represents a targetable vulnerability that can overcome resistance to immune checkpoint inhibitor therapy.
• Combining HSP90 inhibitors with PD-1 blockade holds promise for improving cancer treatment outcomes.