EPHA2 feedback activation limits the response to PDEδ inhibition in KRAS-dependent cancer cells

Authors: Yue-hong Chen1,2, Hao Lv1,3, Ning Shen1, Xiao-min Wang1,3, Shuai Tang1, Bing Xiong4, Jian Ding1,3, Mei-yu Geng1,3, Min Huang1,3
1 School of Life Science, Shanghai University, Shanghai 200444, China
2 Division of Antitumor Pharmacology, State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
3 University of Chinese Academy of Sciences, Beijing 100049, China
4 Department of Medicinal Chemistry, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
Correspondence to: Min Huang:,
DOI: 10.1038/s41401-019-0268-y
Received: 23 April 2019
Accepted: 3 June 2019
Advance online: 17 July 2019


KRAS is one of the most important proto-oncogenes. Its mutations occur in almost all tumor types, and KRAS mutant cancer is still lack of effective therapy. Prenyl-binding protein phosphodiesterase-δ (PDEδ) is required for the plasma membrane association and subsequent activation of KRAS oncogenic signaling. Recently, targeting PDEδ has provided new promise for KRAS mutant tumors. However, the therapeutic potential of PDEδ inhibition remains obscure. In this study, we explored how PDEδ inhibition was responded in KRAS mutant cancer cells, and identified KRAS mutant subset responsive to PDEδ inhibition. We first performed siRNA screen of KRAS growth dependency of a small panel of human cancer lines, and identified a subset of KRAS mutant cancer cells that were highly dependent on KRAS signaling. Among these cells, only a fraction of KRAS-dependent cells responded to PDEδ depletion, though KRAS plasma membrane association was effectively impaired. We revealed that the persistent RAF/MEK/ERK signaling seemed responsible for the lack of response to PDEδ depletion. A kinase array further identified that the feedback activation of EPH receptor A2 (EPHA2) accounted for the compensatory activation of RAF/MEK/ERK signaling in these cells. Simultaneous inhibition of EPHA2 and PDEδ led to the growth inhibition of KRAS mutant cancer cells. Together, this study gains a better understanding of PDEδ-targeted therapeutic strategy and suggests the combined inhibition of EPHA2 and PDEδ as a potential therapy for KRAS mutant cancer.
Keywords: KRAS; anticancer therapy; PDEδ; EPHA2; RAF/MEK/ERK signaling

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