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Poster Display session 1

4156 - Triple blockade of EGFR, MEK and PD-L1 as effective antitumor treatment in PD-L1 overexpressing, MEK inhibitor resistant colon cancer cells.


28 Sep 2019


Poster Display session 1


Basic Science

Tumour Site


Nunzia Matrone


Annals of Oncology (2019) 30 (suppl_5): v1-v24. 10.1093/annonc/mdz238


N. Matrone1, S. Napolitano1, V. Belli1, G. Barra1, E.F. Giunta1, V. De Falco1, M. Terminiello1, P.P. Vitiello1, D. Ciardiello1, M. Turano2, M. Furia2, A.S. Muddassir3, S. Kopetz3, E. Martinelli1, F. Ciardiello1, T. Troiani1

Author affiliations

  • 1 Dipartimento Di Medicina Di Precisione, Università degli Studi della Campania Luigi Vanvitelli, 80131 - Napoli/IT
  • 2 Department Of Biology, University of Naples Federico II, 80126 - Naples/IT
  • 3 Gi Medical Oncology, MD Anderson - Private Practice - Kopetz, Houston/US


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Abstract 4156


Molecular mechanisms driving acquired resistance to anti-EGFR therapies in metastatic Colorectal Cancer (mCRC) are complex but generally involve the activation of the downstream RAS-RAF-MEK-MAPK pathway.


In order to understand the mechanism underlying MEK inhibitor (MEKi) resistance, we generated three different MEKi resistant models, two all RAS WT (SW48-MR and LIM1215-MR) and one mutated in RAS (HCT116-MR).


These models showed features related to the gene signature of Colorectal Cancer CMS4 with upregulation of immune pathway as confirmed by Microarray and Western blot analysis. In particular, moving forward the MEKi phenotype we assisted to the loss of epithelial features and acquisition of mesenchymal markers and morphology. Moreover, this change in the morphology is accompanied by up-regulation of PD-L1 expression and activation of EGFR and its downstream pathway, independently of cell line status mutation. To extend these in vitro findings, we performed an in vivo study using MC38 and CT26 MEKi resistant syngeneic models that we have previously generated. Combined treatment of MEKi, EGFR inhibitor (EGFRi) and PD-L1inhibitor (PD-L1i) resulted in a marked inhibition of tumor growth in both MC38–MR and CT26-MR xenograft model.


These results suggest a strategy to potentially overcome immunotherapy resistance in CMS4-like tumors and to improve the efficacy of MEK inhibition by co-treatment with other agents providing an additional therapeutic strategy via modulation of host immune responses.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

The authors.


Has not received any funding.


All authors have declared no conflicts of interest.

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