Role of LPAR3, PKC and EGFR in LPA-induced cell migration in oral squamous carcinoma cells

Abstract

BackgroundOral squamous cell carcinoma is an aggressive neoplasm with serious morbidity and mortality, which typically spreads through local invasive growth. Lysophosphatidic acid (LPA) is involved in a number of biological processes, and may have a role in cancer cell migration and invasiveness. LPA is present in most tissues and can activate cells through six different LPA receptors (LPAR1-6). Although LPA is predominantly promigratory, some of the receptors may have antimigratory effects in certain cells. The signalling mechanisms of LPA are not fully understood, and in oral carcinoma cells the specific receptors and pathways involved in LPA-stimulated migration are unknown.MethodsThe oral carcinoma cell lines E10, SCC-9, and D2 were investigated. Cell migration was studied in a scratch wound assay, and invasion was demonstrated in organotypic three dimensional co-cultures. Protein and mRNA expression of LPA receptors was studied with Western blotting and qRT-PCR. Activation of signalling proteins was examined with Western blotting and isoelectric focusing, and signalling mechanisms were further explored using pharmacological agents and siRNA directed at specific receptors and pathways.ResultsLPA stimulated cell migration in the two oral carcinoma cell lines E10 and SCC-9, but was slightly inhibitory in D2. The receptor expression profile and the effects of specific pharmacological antagonist and agonists indicated that LPA-stimulated cell migration was mediated through LPAR3 in E10 and SCC-9. Furthermore, in both these cell lines, the stimulation by LPA was dependent on PKC activity. However, while LPA induced transactivation of EGFR and the stimulated migration was blocked by EGFR inhibitors in E10 cells, LPA did not induce EGFR transactivation in SCC-9 cells. In D2 cells, LPA induced EGFR transactivation, but this was associated with slowing of a very high inherent migration rate in these cells.ConclusionThe results demonstrate LPA-stimulated migration in oral carcinoma cells through LPAR3, mediated further by PKC, which acts either in concert with or independently of EGFR transactivation.

Role of autotaxin in cancer stem cells

“…The classic LPA receptors were involved in tumor angiogenesis, migration, invasion, and metastasis [44-47]. The mechanisms include stimulation of vascular endothelial growth factor production [44,48,49] and activation of several signaling pathways, such as the RAS/RAF1/MEK/ERK pathway [50,51], RHOA/RHO associated kinase pathway [52], PI3K/AKT pathway [53], WNT/β-Catenin pathway [54], p38/MAPK pathway [46], PKCα/CARMA pathway [47], and EGFR signaling pathway [55]. Overexpression of LPA1 receptor in MDA-MB-231 cells enhances tumor growth and promotes bone metastasis [56].…”

The critical role and potential target of the autotaxin/lysophosphatidate axis in pancreatic cancer

“…ATX/LPA axis hyperactivation not only predisposes to tumorigenesis but also contributes to other critical aspects of cancer biology including angiogenesis, migration, invasion, and metastasis. 4 Emerging evidences demonstrated that ATX/ LPA promotes cells motogenic activity in diverse types of tumors including ovarian, 74 breast, 56 hepatocellular, 54 melanoma, 75 gastric, 76 bladder, 77 oral squamous, 78 and pancreatic 79 cancer cell lines. Through generating transgenic mice that expressed wild-type human ATX or LPAR driven by MMTV-LTR, the aberrant expression of ATX or LPAR in mammary glands was sufficient to induce the initiation and progression of breast cancer.…”

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

“…In general, it appears that agonists like LPA or other GPCR agonists such as neurotensin and PGE 2 [36,37,39,47] induce signaling via mechanisms that are either EGFR-dependent, EGFR-independent, or both EGFR-dependent and EGFR-independent. We have data suggesting that protein kinase C may play an important role in EGFR-independent signals [39,47], but this was not studied in the present work.…”

“…LPA (10 μM, a dose based on preliminary experiments with HCT116 cells and previous studies with E10 cells, showing an effect plateau around this concentration [39]) elicited biological responses in terms of increase in either DNA synthesis or migration, or both, in all these cells. Figure 1a shows the effect of LPA on DNA synthesis.…”

“…It has been speculated that GPCRs generally mediate EGFR transactivation in transformed and not in normal cells, but this difference is not absolute. We have observed that LPA induces EGFR transactivation in E10 but not in SCC-9 oral carcinoma cells [39].…”