Prostate cancer cell proliferation is influenced by leptin.
BACKGROUND
Obesity is considered a risk for many cancers. Serum leptin levels are often elevated in obese people. Leptin acts as a mitogenic agent in many tissues; therefore, it may act to promote cancer cell growth. We previously demonstrated that leptin acts as a growth factor for prostate cancer cells in vitro. The purpose of this study was to characterize leptin receptor isoform mRNA expression in leptin-treated DU145 and PC-3 prostate cancer cell lines. Expression levels of SOCS-3, a known leptin-inducible suppressor of leptin signaling, and known mitogenic signaling pathways of PI3K and ERK were also analyzed


METHODS
DU145 and PC-3 cells were treated with 0, 4, 40, or 80 ng/ml leptin for 0, 0.5, 1, 2, 4, 24, or 48 h. Multiplex RT-PCR was performed to determine mRNA levels of the short (huOB-Ra) or the long (huOB-Rb) OB-R isoforms or SOCS-3. p-Akt and p-ERK were determined by Western blot. Cell viability and apoptosis were determined by MTT and nucleosomal fragmentation assay


RESULTS
DU145 and PC-3 expressed huOB-Ra, huOB-Rb, and SOCS-3 mRNA. huOB-Ra mRNA levels increased in PC-3 at 48 h (P < 0.01); however, no significant changes were observed in DU145. huOB-Rb mRNA levels decreased at 48 h in DU145; however, a twofold increase at 48 h (P < 0.01) was observed with PC-3 and was dose-dependent (P < 0.05). Leptin increased SOCS-3 mRNA in DU145 at 24 and 48 h (P < 0.05) and in PC-3 at 1 h (2-fold) and 48 h (fivefold; P < 0.01). Leptin up-regulated p-Akt in a time- and dose-dependent manner in the DU145 prostate cancer cells via a suppression of apoptosis. Leptin up-regulated p-ERK in a time-dependent manner in PC-3 cells


CONCLUSIONS
In prostate cancer cells, the mitogenic effects of leptin are not a consequence of altered receptor isoform mRNA expression. No defect in SOCS-3 signaling was observed, and proliferation appears to be working through the PI3K and MAPK leptin receptor-activated pathways, depending on cell type. Leptin stimulation may be selective for either pathway to suppress apoptosis, thereby enhancing prostate cancer growth.
Somasundar
Ponnandai
P
Louis A. Johnson VA Medical Center, Clarksburg, and Department of Surgery, West Virginia University, Morgantown, USA.
Frankenberry
Krista A
KA
Skinner
Heath
H
Vedula
Giridhar
G
McFadden
David W
DW
Riggs
Dale
D
Jackson
Barbara
B
Vangilder
Reyna
R
Hileman
Stanley M
SM
Vona-Davis
Linda C
LC
D017209:Apoptosis / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D045744:Cell Line, Tumor; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule; D004789:Enzyme Activation; D006801:Humans; D020738:Leptin / Q000008:administration & dosage / Q000494:pharmacology*; D008297:Male; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D011471:Prostatic Neoplasms / Q000378:metabolism / Q000473:pathology*; D020033:Protein Isoforms / Q000235:genetics; D012333:RNA, Messenger / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000235:genetics; D054411:Receptors, Leptin; D012097:Repressor Proteins / Q000235:genetics; D000071223:Suppressor of Cytokine Signaling 3 Protein; D050826:Suppressor of Cytokine Signaling Proteins; D014157:Transcription Factors / Q000235:genetics
D020738:Leptin; D020928:Mitogen-Activated Protein Kinases; D019869:Phosphatidylinositol 3-Kinases; D020033:Protein Isoforms; D012333:RNA, Messenger; D011956:Receptors, Cell Surface; D054411:Receptors, Leptin; D012097:Repressor Proteins; D000071223:Suppressor of Cytokine Signaling 3 Protein; D050826:Suppressor of Cytokine Signaling Proteins; D014157:Transcription Factors; C515448:LEPR protein, human; C106644:SOCS3 protein, human