Leptin and adiponectin effects on an ovarian cancer cell line OV-90 which provide insights into obesity’s role in ovarian cancer

A86

Introduction:
 >Although Ovarian Cancer (OC) is of significant public health importance, research efforts to examine the impact of yet another emerging public health concern, namely obesity, on this malignancy, have been limited. Our aims in this study were to determine the effects of Leptin and Adiponectin, (two adipocytokines produced in adipose tissue) on OC cell proliferation and receptor levels, and to examine their effects on OC cell death and angiogenesis.
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 >Materials and Methods:
 >OV-90 cells, obtained from the American Type Culture Collection, were cultured in MCDB 105 /Medium 199 (1:1) with 15% FBS and 1% penicillin/streptomycin. The cells were maintained at 37ºC in 5% CO2. Proliferation assays were performed in 96-well plates (5000 cells/well) after treatment with 0-100 ng/mL Leptin or 0-5000 ng/mL Adiponectin for 24 or 48 hr in serum-free medium. Cell numbers were estimated using the Cell Counting Kit-8 Assay with absorbances read at 450 nm. Western blots were performed on Leptin- and Adiponectin-treated cell lysates, and the blots were quantified with gel digitizing software.
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 >Results:
 >OV-90 cells expressed the Leptin receptor Ob-R and its signaling form OB-Rb. The cells also expressed the Adiponectin receptors Adipo-R1 and Adipo-R2. Leptin treatment enhanced Cyclin D1 and PCNA expression and elicited significant cell growth at 50 ng/mL. Further, Leptin treatment up-regulated VEGF expression at 50 ng/mL, induced COX-2 expression above basal levels (~2-fold) and up-regulated PKC-α expression at 50 & 100 ng/mL. Leptin enhanced Bax protein expression (peaking at 50 ng/mL) but had little effect on Bcl-2. A down-regulation of JAK-2 expression with a Leptin dose higher than 5 ng/mL was observed. Adiponectin treatment had no effect on Ob-R expression, but Adipo-R1 expression was markedly up-regulated, while Adipo-R2 was only moderately enhanced at 5000 ng/mL. Adiponectin exerted significant growth inhibition at 5000 ng/mL.
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 >Conclusions:
 >OV-90 cells express the Leptin receptors, OB-R and Ob-Rb, as well as the Adiponectin receptors Adipo-R1 and Adipo-R2. A physiologically relevant concentration of Leptin (50 ng/mL), as found in obese subjects, significantly increased OV-90 cell growth, and markedly enhanced VEGF expression (~5-fold above basal). This suggests Leptin may promote angiogenesis of OV-90 cells. In addition, Leptin at 50 or 100 ng/mL increased PKC-α expression, which may lead to intracellular activation of various signaling pathways and would portend a poorer prognosis in obesity. Since JAK-2 is constitutively associated with Ob-Rb, it is not surprising that Leptin modulated its expression. Leptin had no effect on Bcl-2 but markedly enhanced Bax expression levels, suggesting OV-90 cells have a vulnerability to apoptotic activation on Leptin exposure. Treatment of OV-90 cells with 5000 ng/mL Adiponectin up-regulated both Adipo-R1 and Adipo-R2 receptor expression. At this dose, growth inhibition was observed, suggesting this may be mediated through both receptors, predominantly Adipo-R1. Overall, these findings provide evidence of potential mechanisms in obesity where a reduced serum adiponectin:leptin ratio would be expected to impact ovarian cancer development and progression.
 >The Hormel Foundation supported this work.