title: Bidirectional crosstalk between leptin and insulin-like growth factor-I signaling promotes invasion and migration of breast cancer cells via transactivation of epidermal growth factor receptor.
abstract: Obesity is an independent risk factor for breast cancer, and obese breast cancer patients exhibit a higher risk for larger tumor burden and increased metastasis. Obesity, as associated with metabolic syndrome, results in an increase in circulating insulin-like growth factor (IGF), which acts as a mitogen. In addition, higher plasma level of adipocytokine leptin is associated with obesity. In the present study, we show that cotreatment with leptin and IGF-I significantly increases proliferation as well as invasion and migration of breast cancer cells. We found a novel bidirectional crosstalk between leptin and IGF-I signaling; IGF-I induced phosphorylation of leptin receptor (Ob-Rb) and leptin induced phosphorylation of IGF-I receptor (IGF-IR), whereas cotreatment induced synergistic phosphorylation and association of Ob-Rb and IGF-IR along with activation of downstream effectors, Akt and extracellular signal-regulated kinase. Leptin increased phosphorylation of IGF signaling molecules insulin-receptor substrate (IRS)-1 and IRS-2. Interestingly, we found that leptin and IGF-I cotreatment synergistically transactivated epidermal growth factor receptor (EGFR), depending on the proteolytic release of EGFR ligands, as the broad-spectrum matrix metalloproteinase inhibitor GM6001 could inhibit this effect. Using clinically relevant EGFR inhibitors, erlotinib and lapatinib, we found that inhibition of EGFR activation effectively inhibited leptin- and IGF-I-induced invasion and migration of breast cancer cells. Taken together, these data suggest a novel bidirectional crosstalk between leptin and IGF-I signaling that transactivates EGFR and promotes the metastatic properties as well as invasion and migration of breast cancer cells. Our findings indicate the possibility of using EGFR inhibitors erlotinib and lapatinib to counter the procancerous effects of leptin and IGF-I in breast cancers.
authors.affiliation: Department of Medicine, Winship Cancer Institute, Emory University School of Medicine, Atlanta, Georgia 30322, USA. nk.saxen@emory.edu
authors.forename: Neeraj K
authors.initials: NK
authors.lastname: Saxena
authors.forename: LaTonia
authors.initials: L
authors.lastname: Taliaferro-Smith
authors.forename: Brandi B
authors.initials: BB
authors.lastname: Knight
authors.forename: Didier
authors.initials: D
authors.lastname: Merlin
authors.forename: Frank A
authors.initials: FA
authors.lastname: Anania
authors.forename: Ruth M
authors.initials: RM
authors.lastname: O'Regan
authors.forename: Dipali
authors.initials: D
authors.lastname: Sharma
mesh_terms: D001943:Breast Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology*; D048708:Cell Growth Processes / Q000187:drug effects; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000187:drug effects / Q000502:physiology*; D004357:Drug Synergism; D066246:ErbB Receptors / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D000069347:Erlotinib Hydrochloride; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000494:pharmacology*; D000077341:Lapatinib; D020738:Leptin / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000494:pharmacology*; D009361:Neoplasm Invasiveness; D011799:Quinazolines / Q000494:pharmacology; D020239:Receptor Cross-Talk; D017526:Receptor, IGF Type 1 / Q000378:metabolism; D054411:Receptors, Leptin / Q000378:metabolism; D015398:Signal Transduction; D015533:Transcriptional Activation
chemical_list: C515448:LEPR protein, human; D020738:Leptin; D011799:Quinazolines; D054411:Receptors, Leptin; D000077341:Lapatinib; D007334:Insulin-Like Growth Factor I; D000069347:Erlotinib Hydrochloride; D066246:ErbB Receptors; D017526:Receptor, IGF Type 1