Effect of inhibition of the lysophosphatidic acid receptor 1 on metastasis and metastatic dormancy in breast cancer.
BACKGROUND
Previous studies identified the human nonmetastatic gene 23 (NME1, hereafter Nm23-H1) as the first metastasis suppressor gene. An inverse relationship between Nm23-H1 and expression of lysophosphatidic acid receptor 1 gene (LPAR1, also known as EDG2 or hereafter LPA1) has also been reported. However, the effects of LPA1 inhibition on primary tumor size, metastasis, and metastatic dormancy have not been investigated.


METHODS
The LPA1 inhibitor Debio-0719 or LPA1 short hairpinned RNA (shRNA) was used. Primary tumor size and metastasis were investigated using the 4T1 spontaneous metastasis mouse model and the MDA-MB-231T experimental metastasis mouse model (n = 13 mice per group). Proliferation and p38 intracellular signaling in tumors and cell lines were determined by immunohistochemistry and western blot to investigate the effects of LPA1 inhibition on metastatic dormancy. An analysis of variance-based two-tailed t test was used to determine a statistically significant difference between treatment groups.


RESULTS
In the 4T1 spontaneous metastasis mouse model, Debio-0719 inhibited the metastasis of 4T1 cells to the liver (mean = 25.2 liver metastases per histologic section for vehicle-treated mice vs 6.8 for Debio-0719-treated mice, 73.0% reduction, P < .001) and lungs (mean = 6.37 lesions per histologic section for vehicle-treated mice vs 0.73 for Debio-0719-treated mice, 88.5% reduction, P < .001), with no effect on primary tumor size. Similar results were observed using the MDA-MB-231T experimental pulmonary metastasis mouse model. LPA1 shRNA also inhibited metastasis but did not affect primary tumor size. In 4T1 metastases, but not primary tumors, expression of the proliferative markers Ki67 and pErk was reduced by Debio-0719, and phosphorylation of the p38 stress kinase was increased, indicative of metastatic dormancy.


CONCLUSIONS
The data identify Debio-0719 as a drug candidate with metastasis suppressor activity, inducing dormancy at secondary tumor sites.
The Women's Cancers Section, Laboratory of Molecular Pharmacology, Center for Cancer Research, National Institutes of Health, Bethesda, MD 20892, USA.
Jean-Claude A
JC
Marshall
Joshua W
JW
Collins
Joji
J
Nakayama
Christine E
CE
Horak
David J
DJ
Liewehr
Seth M
SM
Steinberg
Mary
M
Albaugh
Fernando
F
Vidal-Vanaclocha
Diane
D
Palmieri
Maryse
M
Barbier
Maximilien
M
Murone
Patricia S
PS
Steeg
D000704:Analysis of Variance; D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D015153:Blotting, Western; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D005260:Female; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D007150:Immunohistochemistry; D007555:Isoxazoles / Q000494:pharmacology*; D019394:Ki-67 Antigen / Q000187:drug effects / Q000378:metabolism; D008113:Liver Neoplasms / Q000378:metabolism / Q000517:prevention & control* / Q000556:secondary; D008175:Lung Neoplasms / Q000378:metabolism / Q000517:prevention & control* / Q000556:secondary; D020935:MAP Kinase Signaling System / Q000187:drug effects; D008325:Mammary Neoplasms, Experimental / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology*; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D054778:NM23 Nucleoside Diphosphate Kinases / Q000187:drug effects / Q000378:metabolism; D011422:Propionates / Q000494:pharmacology*; D034741:RNA, Small Interfering / Q000494:pharmacology; D011897:Random Allocation; D049368:Receptors, Lysophosphatidic Acid / Q000037:antagonists & inhibitors* / Q000235:genetics; D019892:eIF-2 Kinase / Q000187:drug effects / Q000378:metabolism
D000970:Antineoplastic Agents; D007555:Isoxazoles; D019394:Ki-67 Antigen; D054778:NM23 Nucleoside Diphosphate Kinases; D011422:Propionates; D034741:RNA, Small Interfering; D049368:Receptors, Lysophosphatidic Acid; D019892:eIF-2 Kinase; C477898:3-(4-(4-((1-(2-chlorophenyl)ethoxy)carbonyl amino)-3-methyl-5-isoxazolyl) benzylsulfanyl) propanoic acid