HCC-derived EGFR mutants are functioning, EGF-dependent, and erlotinib-resistant

Area of Science:

• Oncology
• Molecular Biology
• Genetics

Background:

• Epidermal growth factor receptor (EGFR) is a therapeutic target in hepatocellular carcinoma (HCC).
• EGFR activation contributes to sorafenib resistance in HCC.
• Previous studies identified 13 missense mutations in EGFR exons 19-23 from HCC tissues, but their functions remain unknown.

Purpose of the Study:

• To determine the kinase activity of seven HCC-derived EGFR mutants (K757E, N808S, R831C, V897A, P937L, T940A, and M947T).
• To assess the sensitivity of these mutants to erlotinib, a first-generation EGFR-tyrosine kinase inhibitor (TKI).

Main Methods:

• Constructed NIH-3T3 cell lines stably expressing wild-type EGFR, known erlotinib-sensitive (L858R) and resistant (T790M) mutants, and the seven HCC-derived mutants.
• Assessed EGFR phosphorylation, EGF-dependency, and kinase activity.
• Evaluated erlotinib-induced apoptosis and autophagy by measuring caspase-3, PARP cleavage, and LC3-II levels.

Main Results:

• The seven HCC-derived EGFR mutants are functional, EGF-dependent, and exhibit some constitutive kinase activity.
• Erlotinib induced varying degrees of apoptosis and autophagy in cells with different EGFR mutations.
• The seven HCC-derived mutants demonstrated resistance to erlotinib, with only partial inhibition of EGFR, AKT, and ERK phosphorylation, and partial apoptosis/autophagy.

Conclusions:

• The seven studied HCC-derived EGFR mutants are functional, EGF-dependent, and resistant to erlotinib.
• The degree of EGFR phosphorylation inhibition by erlotinib correlates with the extent of apoptosis and autophagy observed.
• These findings suggest further investigation into the sensitivity of these mutants to third-generation EGFR-TKIs like osimertinib is warranted.