Cancer Cells Expressing Oncogenic Rat Sarcoma Show Drug-Addiction Toward Epidermal Growth Factor Receptor Antibodies Mediated by Sustained MAPK Signaling.

Joseph Tintelnot,Malte Kriegs,Mascha Binder,Marie Trentmann,Friederike Braig,Lisa Von Wenserski,Carsten Bokemeyer,Alexander Stein,Kristoffer Riecken,Anna Oberle,Sina Metz,Boris Fehse,Christoph Schultheiß

doi:10.3389/fonc.2019.01559

Abstract

Epidermal growth factor receptor (EGFR) antibodies may have detrimental effects in patients with metastatic colorectal cancer expressing oncogenic Rat sarcoma (RAS). Since a significant number of patients acquire RAS-mediated resistance during EGFR-directed treatment, understanding the molecular mechanism underlying these antibody-mediated tumor-promoting effects is of relevance to design more resistance-preventive treatment approaches. To test this, we set up a Ba/F3 cellular model system transformed to EGFR/RAS dependency to be able to study proliferation, RAS activity as well as MAPK signaling upon inhibition of wild-type RAS isoforms by therapeutic EGFR antibodies. Here, we show that the EGFR antibodies cetuximab and panitumumab induce paradoxical stimulation and enhance proliferation in cells expressing oncogenic RAS (KRAS G12V). These experiments clearly showed that the stimulatory effect is a direct result of the antibody-EGFR interaction leading to prolonged mitogen-activated protein-Kinase (MAPK) signaling. The effect was also induced by antibody-chemotherapy combinations but always depended on simultaneous low-level ligand-dependent EGFR pathway activation. Moreover, we observed significant growth retardation of RAS mutant cells after antibody withdrawal compatible with a drug-addiction phenotype. Our data suggests that EGFR antibodies paradoxically sustain MAPK signaling downstream of oncogenic RAS thereby driving proliferation of RAS mutant tumors or tumor subclones. The observed drug-addiction encourages fixed-duration or liquid-biopsy-guided drug holiday concepts to preventively clear RAS mutant subclones selected under EGFR-directed therapeutic pressure.

Highlights

Monoclonal antibodies which inhibit signaling downstream the epidermal growth factor receptor (EGFR) have become one of the mainstays of targeted therapy in metastatic colorectal cancer [1]
HEGFR wt / human KRAS (hKRAS) wt and human EGFR (hEGFR) wt / hKRAS G12V transduced Ba/F3 cells showed modest and highly increased proliferation without human EGF (hEGF) addition, suggesting growth factor independence conferred by Rat sarcoma (RAS) wild-type overexpression or the oncogenic RAS mutation (Figure 1B)
In patients with primary oncogenic RAS mutations, treatment with Epidermal growth factor receptor (EGFR)-inhibiting antibodies seems to worsen the prognosis compared to chemotherapy alone [14, 19, 20]

Summary

Introduction

Monoclonal antibodies which inhibit signaling downstream the epidermal growth factor receptor (EGFR) have become one of the mainstays of targeted therapy in metastatic colorectal cancer (mCRC) [1] Both the chimeric EGFR antibody cetuximab and the fully human antibody panitumumab have been approved as single agents or in combination with chemotherapy [2,3,4,5,6,7,8,9]. A number of clinical trials have demonstrated inferior outcomes of EGFR-antibody treated patients with RAS mutations compared to treatment with the chemotherapy backbone alone This effect was found for cetuximab and panitumumab in the context of an oxaliplatinum-containing chemotherapy regimen [14, 19], and for panitumumab in combination with irinotecan [20]. A liquid biopsy trial showed that RAS mutant subclones selected on EGFR-directed therapeutic pressure decrease in size once the selecting antibody was withdrawn, suggesting a fitness disadvantage, or some sort of dependency of those clones on the drug [22]

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Results

Conclusion