<p>Figure S1 shows qPCR assessment of LPA receptors knockdown Figure S2 shows EGFR transactivation by LPA1 in various cell lines. Figure S3 shows qPCR assessment of EGFR knockdown in HT1080 cells. Figure S4 shows that Src inhibition blocks EGFR phosphorylation in hypoxic HT1080 cells.</p>
ARTICLE ABSTRACT
Hypoxia, a common feature of solid tumors, has been critically involved in cell invasion and metastasis, but the underlying mechanisms remain poorly understood. Previously, it has been observed that the lysophosphatidic acid receptor 4 (LPA4) signaling axis mediates production of the degradative subcellular structures invadopodia, which are known to be required for metastasis. Here, it is demonstrated that LPA1 (LPAR1) is a common and major receptor used for hypoxia-induced invadopodia production in various cancer cell lines. The widespread use of LPA1 was not due to increased LPA1 expression but rather relied on Src-mediated cross-talk with EGFR. LPA1-mediated phosphorylation of Y845-EGFR under hypoxia led to PI3K/Akt activation, an event that increases the ability of cells to produce invadopodia. Moreover, phospho-Y845-EGFR was upregulated in hypoxic zones of tumors and a combination of EGFR and LPA1 inhibition synergistically suppressed metastasis in vivo.Implications: This study uncovers an LPA1–EGFR signaling axis that is used for cell invasion in hypoxia and suggests a potential target to impede cancer metastasis. Mol Cancer Res; 16(10); 1601–13. ©2018 AACR.
