Lysophosphatidate signaling stabilizes Nrf2 and increases the expression of genes involved in drug resistance and oxidative stress responses: implications for cancer treatment.
The present work elucidates novel mechanisms for lysophosphatidate (LPA)-induced chemoresistance using human breast, lung, liver, and thyroid cancer cells. LPA (0.5-10 μM) increased Nrf2 transcription factor stability and nuclear localization by ≤5-fold. This involved lysophosphatidate type 1 (LPA1) receptors as identified with 1 μM wls-31 (LPA1/2 receptor agonist) and blocking this effect with 20 μM Ki16425 (LPA1-3 antagonist, Ki = 0.34 μM). Knockdown of LPA1 by 50% to 60% with siRNA decreased Nrf2 stability and expressing LPA1, but not LPA2/3, in human HepG2 cells increased Nrf2 stabilization. LPA-induced Nrf2 expression increased transcription of multidrug-resistant transporters and antioxidant genes by 2- to 4-fold through the antioxidant response element. This protected cells from doxorubicin-induced death. This pathway was verified in vivo by orthotopic injection of 20,000 mouse 4T1 breast cancer cells into syngeneic mice. Blocking LPA production with 10 mg/kg per d ONO-8430506 (competitive autotaxin inhibitor, IC90 = 100 nM) decreased expression of Nrf2, multidrug-resistant transporters, and antioxidant genes in breast tumors by ≤90%. Combining 4 mg/kg doxorubicin every third day with ONO-8430506 synergistically decreased tumor growth and metastasis to lungs and liver by >70%, whereas doxorubicin alone had no significant effect. This study provides the first evidence that LPA increases antioxidant gene and multidrug-resistant transporter expression. Blocking this aspect of LPA signaling provides a novel strategy for improving chemotherapy.
*Signal Transduction Research Group, Department of Biochemistry, University of Alberta, Edmonton, Alberta, Canada; and Department of Surgery, University of Alberta, WC Mackenzie Health Science Centre, Edmonton, Alberta, Canada.
Ganesh
G
Venkatraman
*Signal Transduction Research Group, Department of Biochemistry, University of Alberta, Edmonton, Alberta, Canada; and Department of Surgery, University of Alberta, WC Mackenzie Health Science Centre, Edmonton, Alberta, Canada.
Matthew G K
MG
Benesch
*Signal Transduction Research Group, Department of Biochemistry, University of Alberta, Edmonton, Alberta, Canada; and Department of Surgery, University of Alberta, WC Mackenzie Health Science Centre, Edmonton, Alberta, Canada.
Xiaoyun
X
Tang
*Signal Transduction Research Group, Department of Biochemistry, University of Alberta, Edmonton, Alberta, Canada; and Department of Surgery, University of Alberta, WC Mackenzie Health Science Centre, Edmonton, Alberta, Canada.
Jay
J
Dewald
*Signal Transduction Research Group, Department of Biochemistry, University of Alberta, Edmonton, Alberta, Canada; and Department of Surgery, University of Alberta, WC Mackenzie Health Science Centre, Edmonton, Alberta, Canada.
Todd P W
TP
McMullen
*Signal Transduction Research Group, Department of Biochemistry, University of Alberta, Edmonton, Alberta, Canada; and Department of Surgery, University of Alberta, WC Mackenzie Health Science Centre, Edmonton, Alberta, Canada david.brindley@ualberta.ca.
David N
DN
Brindley
D000818:Animals; D000903:Antibiotics, Antineoplastic / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects; D015415:Biomarkers / Q000378:metabolism*; D015153:Blotting, Western; D001943:Breast Neoplasms / Q000188:drug therapy / Q000235:genetics / Q000473:pathology*; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D004195:Disease Models, Animal; D004317:Doxorubicin / Q000494:pharmacology*; D019008:Drug Resistance, Neoplasm / Q000235:genetics*; D005260:Female; D006801:Humans; D007124:Immunoenzyme Techniques; D008246:Lysophospholipids / Q000378:metabolism*; D051379:Mice; D051267:NF-E2-Related Factor 2 / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D018384:Oxidative Stress / Q000187:drug effects / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D049368:Receptors, Lysophosphatidic Acid / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects
D000903:Antibiotics, Antineoplastic; D015415:Biomarkers; D008246:Lysophospholipids; D051267:NF-E2-Related Factor 2; C495635:NFE2L2 protein, human; D012333:RNA, Messenger; D049368:Receptors, Lysophosphatidic Acid; D004317:Doxorubicin
autotaxin; autotaxin inhibitors; breast cancer; chemoresistance; doxorubicin