Lysophosphatidic acid induces both EGFR-dependent and EGFR-independent effects on DNA synthesis and migration in pancreatic and colorectal carcinoma cells

Abstract

Lysophosphatidic acid (LPA) is a small glycerophospholipid ubiquitously present in tissues and plasma. It acts through receptors belonging to the G-protein-coupled receptor (GPCR) family, is involved in several biological processes, and is strongly implicated in different cancers. In this paper, we have investigated the effects of LPA on DNA synthesis and migration in a panel of pancreatic and colon cancer cells, with particular focus on the involvement of the epidermal growth factor (EGF) receptor (EGFR) in LPA-induced signaling. LPA stimulated DNA synthesis and/or migration in all the cell lines included in this study. In five of the six cell lines, LPA induced phosphorylation of the EGFR, and the effects on EGFR and Akt, and in some of the cells also ERK, were sensitive to the EGFR tyrosine kinase inhibitor gefitinib, strongly suggesting LPA-induced EGFR transactivation in these cells. In contrast, in one of the pancreatic carcinoma cell lines (Panc-1), we found no evidence of transactivation of the EGFR. In the pancreatic carcinoma cell lines where transactivation took place (BxPC3, AsPC1, HPAFII), gefitinib reduced LPA-induced DNA synthesis and/or migration. However, we also found evidence of transactivation in the two colon carcinoma cell lines (HT29, HCT116) although gefitinib did not inhibit LPA-induced DNA synthesis or migration in these cells. Taken together, the data indicate that in many gastrointestinal carcinoma cells, LPA uses EGFR transactivation as a mechanism when exerting such effects as stimulation of cell proliferation and migration, but EGFR-independent pathways may be involved instead of, or in concerted action with, the EGFR transactivation.

p38 differentially regulates ERK, p21, and mitogenic signalling in two pancreatic carcinoma cell lines

“…The graphs show densitometric quantification of p38 phosphorylation based on three independent experiments ± SEM. The signal strength of p38 was used as a loading control and the amount of p-p38 was normalized to total p38 Thoresen et al 2003;Murphy and Blenis 2006;Aasrum et al 2016).We previously found that in hepatocytes, p38 inhibition increased HGF-stimulated ERK phosphorylation, particularly the sustained response measured 24 h after exposure to HGF, and that this increase was involved in the enhancement of HGF-induced DNA synthesis (Aasrum et al 2016). We here show that in AsPC-1 cells, p38 inhibition did not significantly affect the early phase (20 min) of ERK phosphorylation (Fig.…”

Transactivation of Epidermal Growth Factor Receptor by G Protein-Coupled Receptors: Recent Progress, Challenges and Future Research

“…There are also significant publications that support the role of EGFR transactivation in various diseases including lung cancer [ 46 , 49 , 62 , 63 , 64 ], breast cancer [ 51 , 65 , 66 ], oral cancer [ 67 ], gastrointestinal carcinoma [ 68 , 69 ], Osteoblasts [ 70 ], ovarian cancer [ 52 , 71 , 72 ], hepatocarcinoma [ 73 ], head and neck cancer [ 74 ], glioblastoma [ 75 ], heart disease [ 55 , 59 ], and renal fibrosis [ 76 ].…”

Endogenous lysophosphatidic acid (LPA1) receptor agonists demonstrate ligand bias between calcium and ERK signalling pathways in human lung fibroblasts

“…To confirm that the ERK phosphorylation is occurring independent of G q/11 activation, and that the PTx‐treated calcium responses are solely due to G q/11 activation, it would be interesting to repeat these experiments in the presence of selective G q inhibition or down‐regulation of specific G proteins using siRNA treatment. Although we cannot rule out a role for LPA 1 receptor‐mediated EGF transactivation leading to ERK phosphorylation, this has been shown to be dependent upon G i/o ‐derived βγ subunits in fibroblasts, and therefore, this would still indicate ligand bias at the level of the G protein (Daub et al, ; Tveteraas et al, ).…”

“…Fibroblast chemotaxis to LPA has also been shown to occur via the PTx‐sensitive G i/o proteins (Tager et al, ), whereas the G 12/13 ‐RhoA pathway is responsible for actin cytoskeleton rearrangements in fibroblasts (Sakai et al, ). In addition, the LPA receptor can transactivate EGF receptors, leading to ERK phosphorylation via G i/o ‐derived βγ sub units (Daub et al, ; Tveteraas et al, ). In this study, we have investigated a number of different naturally occurring analogues of LPA, in terms of their activation of endogenous LPA 1 receptors in primary HLF.…”