Lysophosphatidic acid signaling through LPA receptor subtype 1 induces colony scattering of gastrointestinal cancer cells.
OBJECTIVE
Lysophosphatidic acid (LPA) is a multifunctional lipid mediator involved in triggering tumor cell invasion and metastasis, as well as malignant cell growth. LPA is also known to modulate the colony scattering of epithelial cancers, which is a prerequisite for cell invasion. However, the underlying details of how this is accomplished are not clear. Here we have investigated the roles of specific LPA receptor subtypes in cell scattering.


METHODS
Gastrointestinal carcinoma cell lines were examined for cell scattering activity in response to LPA, and the expression of LPA receptor subtypes was determined by RT-PCR. The effect of down regulation of each LPA receptor in DLD1 cells was determined using a shRNA-lentivirus system. In addition, the effect of overexpression of LPA receptors on cell scattering was investigated using lentivirus expression constructs.


RESULTS
The colonies of AGS and DLD1, but not MKN74, cells were dispersed in response to LPA. RT-PCR analysis revealed that the mRNAs of LPA1, LPA2, and LPA3 were present in AGS and DLD1 cells, but only LPA2 mRNA was detected in MKN74 cells. In DLD1 cells, the scattering activity induced by LPA was partially blocked by pretreatment with PP2 and PD98059, inhibitors of src kinase and MEK, respectively. LPA1 knockdown with shRNA decreased the degree of cell scattering induced by LPA. Knockdown of LPA2 or LPA3 had no effect on LPA-induced scattering. In addition, overexpression of LPA1 in DLD1 cells slightly decreased the response time of LPA-induced cell scattering. On the contrary, MKN74 cells expressing exogenous LPA1 did not respond to LPA by scattering.


CONCLUSIONS
These results demonstrate that LPA1 mediates LPA-stimulated cell scattering of gastrointestinal carcinomas, but that activation of other intracellular pathways, besides those contributing to ERK phosphorylation, is also necessary for cell scattering in response to LPA.
Shin
Kum-Joo
KJ
Department of Biochemistry, College of Medicine and Cancer Research Institute, Seoul National University, Seoul, 110-799, Republic of Korea.
Kim
You Lim
YL
Lee
Sukmook
S
Kim
Dong-Kyu
DK
Ahn
Curie
C
Chung
Junho
J
Seong
Jae Young
JY
Hwang
Jong-Ik
JI
D015153:Blotting, Western; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005770:Gastrointestinal Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D006801:Humans; D016086:Lentivirus / Q000235:genetics; D008246:Lysophospholipids / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000494:pharmacology; D049368:Receptors, Lysophosphatidic Acid / Q000235:genetics* / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D014407:Tumor Cells, Cultured
D008246:Lysophospholipids; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D049368:Receptors, Lysophosphatidic Acid; D048049:Extracellular Signal-Regulated MAP Kinases; C032881:lysophosphatidic acid