Autocrine expression of EGFR ligands in 2D- and 3D-cell culture models (FaDu) and their interaction after treatment with Cetuximab

Introduction Response rates to epidermal growth factor receptor (EGFR) inhibition with Cetuximab are difficult to predict and remain insufficiently understood. An underlying reason might be the interaction of the autocrine expression of EGFR ligands and Cetuximab. In this study we evaluated the autocrine expression of EGF, TGFα, Epiregulin (EREG) and Amphiregulin (AREG) in tumor cell lines in dependency of Cetuximab.

Methods Concentrations of EGF, TGFα, AREG and EREG were measured by ELISA in FaDu cell line supernatants both in 2D- and 3D- cell culture models (replicates: n = 21 and n = 20).

Results On day 7 (2D) and day 13 (3D), respectively, EGF could not be detected within the cell line supernatants (<1pg/ml). Autocrine expression of TGFα, EREG und AREG were 17,65 and 16,45pg/ml, 557,15 and 678,49 pg/ml as well as 29,28 and 8,23 pg/ml in 2D- ad 3D-cell culture models, respectively. Treatment with Cetuximab revealed increasing endogeous expression of the ligands, with the highest rate for TGFα compared to EREG and AREG (2D: +207 %; 3D: +231 %). The concentration of EREG increased by 11 % (2D) and 6 % (3D) as well as AREG by 46 % (2D) and 35 % (3D), respectively.

Conclusion FaDu-cells secrete, other than expected, autocrine ligands as respone to EGFR inhibition. Higher rates of secretion of TGFα compared to EREG and AREG might be dependend on different affinities to the EGFR receptor: TGFα is regarded as high-affinity ligand to EGFR. In literature, an autocrine loop was decribed for TGFα whose up-regulation sustains the EGFR signaling pathway. This might cause low response rates to anti-EGFR therapy.

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Publication History

Article published online:
10 June 2020