Protective autophagy elicited by RAF→MEK→ERK inhibition suggests a treatment strategy for RAS-driven cancers

Area of Science:

• Oncology
• Molecular Biology
• Cancer Research

Background:

• Pancreatic ductal adenocarcinoma (PDA) is a lethal cancer driven by KRAS.
• The RAF→MEK→ERK pathway is crucial in PDA, but its inhibition alone lacks clinical benefit.
• KRAS pathway inhibition paradoxically induces autophagy, a cellular recycling process that aids cancer cell survival.

Purpose of the Study:

• To investigate the role of autophagy in PDA resistance to KRAS pathway inhibition.
• To evaluate the efficacy of combined MEK and autophagy inhibition in PDA.
• To explore this combination therapy in other RAS-driven cancers.

Main Methods:

• Inhibition of MEK1/2 to activate the LKB1→AMPK→ULK1 autophagy axis.
• In vitro and in vivo studies using PDA cell lines and patient-derived xenografts.
• Combination therapy with trametinib (MEK inhibitor) and chloroquine/hydroxychloroquine (autophagy inhibitors).

Main Results:

• MEK inhibition activates autophagy, conferring resistance to PDA cells.
• Combined MEK and autophagy inhibition demonstrated synergistic anti-proliferative effects in vitro.
• Combination therapy led to regression of patient-derived PDA tumors in mice.
• Similar responses were observed in NRAS-mutated melanoma and BRAF-mutated colorectal cancer models.
• A PDA patient showed a partial disease response to trametinib plus hydroxychloroquine.

Conclusions:

• Autophagy is a key resistance mechanism to MEK inhibition in PDA.
• Combination of MEK and autophagy inhibitors offers a promising therapeutic strategy for PDA.
• This combination therapy may be effective against various RAS-driven cancers.