Combined targeting of Raf and Mek synergistically inhibits tumorigenesis in triple negative breast cancer model...

Area of Science:

• Oncology
• Molecular Biology
• Pharmacology

Background:

• Aberrant Ras-MAPK signaling, driven by receptor tyrosine kinases (RTKs) like EGFR and HER2, is characteristic of triple-negative breast cancer (TNBC).
• This aberrant signaling provides a strong rationale for targeting the Ras-MAPK pathway in TNBC treatment strategies.

Purpose of the Study:

• To investigate the effects of co-targeting components of the EGFR/HER2-Ras-Raf-Mek-Erk pathway in human TNBC cell lines and *in vivo* models.
• To assess the *in vitro* and *in vivo* efficacy of combined inhibition of Raf and Mek signaling in TNBC.

Main Methods:

• Utilized human TNBC cell lines (MDA-MB-231, MDA-MB-468) to evaluate *in vitro* signaling inhibition, cytotoxicity, and drug synergy.
• Assessed *in vivo* effects on tumor growth and metastasis using orthotopic mouse xenograft models.
• Compared the efficacy of dual EGFR/HER2 inhibitor lapatinib, EGFR inhibitor erlotinib, Raf inhibitor sorafenib, and Mek inhibitor U0126, as well as their combinations.

Main Results:

• Lapatinib showed greater cytotoxic and MAPK signaling inhibition than erlotinib, indicating contributions from both EGFR and HER2.
• Sorafenib and U0126 more effectively suppressed MAPK signaling than lapatinib, with sorafenib demonstrating higher cytotoxicity.
• U0126 exhibited additive and synergistic effects when combined with lapatinib and sorafenib, respectively, highlighting in-series pathway synergy.
• Combined Raf and Mek inhibition with sorafenib and selumitinib significantly reduced primary tumor growth and pulmonary metastasis in mouse xenografts.

Conclusions:

• Co-targeting Raf and Mek demonstrates synergistic efficacy in TNBC models.
• The combination of Raf and Mek inhibitors represents a promising therapeutic strategy for aggressive breast cancer types like TNBC.