Regorafenib induces damage-associated molecular patterns, cancer cell death and immune modulatory effects in a murine triple negative breast cancer model

Area of Science:

• Immunology
• Oncology
• Pharmacology

Background:

• Damage-associated molecular patterns (DAMPs) like calreticulin (CRT), high-mobility group box 1 protein (HMGB1), and ATP are hallmarks of immunogenic cell death (ICD).
• These DAMPs are implicated in cancer immunotherapy, particularly in immunogenic subtypes like triple-negative breast cancer (TNBC).

Purpose of the Study:

• To investigate the effects of regorafenib, a multi-target angiokinase inhibitor, on DAMPs and cell death in TNBC.
• To evaluate regorafenib's efficacy in suppressing TNBC progression and metastasis in preclinical models.

Main Methods:

• Regorafenib was used to treat TNBC cells, and DAMPs (HMGB1, CRT, ATP) were measured.
• STAT3 signaling was manipulated to assess its role in regorafenib-induced DAMPs.
• A 4T1 syngeneic murine model was used to assess regorafenib's impact on tumor growth, metastasis, and immune cell infiltration.
• Immunohistochemistry and flow cytometry were employed to analyze tumor-infiltrating lymphocytes and dendritic cell expression.

Main Results:

• Regorafenib induced HMGB1 expression, CRT exposure, and ATP release in TNBC cells, consistent with ICD.
• STAT3 overexpression attenuated regorafenib-induced HMGB1 and CRT.
• Regorafenib suppressed 4T1 tumor growth and reduced lung metastasis in mice.
• Increased CD4+ and CD8+ T cell infiltration was observed in regorafenib-treated tumors.
• Regorafenib increased MHC II expression on dendritic cells, but combination with PD-1 blockade showed no synergistic anti-tumor effect.

Conclusions:

• Regorafenib effectively induces ICD and suppresses tumor progression and metastasis in TNBC.
• STAT3 signaling is involved in mediating regorafenib's effects on DAMPs.
• Combination therapy of regorafenib with PD-1 blockade requires careful consideration due to lack of synergistic effects in this model.