Poster Presentation 14th International Biennial Conference on Metastasis Research 2012

Neural signaling promotes lymphangiogenesis and increases lymphatic metastasis. (#137)

Caroline P Le 1 , Ming G Chai 1 , Matthew A Pimentel 1 , Erica K Sloan 1
  1. Monash Institute of Pharmaceutical Sciences, Parkville, Australia

Lymphangiogenesis facilitates tumour cell escape from primary tumours to promote lymphatic metastasis. However, little is known about the physiological dynamics that regulate lymphangiogenesis. We previously showed that chronic physiological stress increases breast cancer metastasis through the peripheral sympathetic nervous system that signals via β-adrenergic receptors. This study investigated the impact of chronic stress on lymphangiogenesis to promote breast cancer progression. To determine the effect of stress-induced SNS activation on lymphatic metastases, mice were inoculated into the fourth mammary fat pad with 2 x 10^5 MDA-MB-231/HM breast cancer cells and tumour cell dissemination was tracked by bioluminescence imaging. Chronic stress increased lymph node metastasis by 14-fold (p < .001). Similarly, pharmacological activation of SNS beta-adrenergic signalling increased lymphatic metastasis by 42-fold (p < .001). To investigate if increased lymphatic metastasis was linked to increased lymphatic density in primary mammary tumours, we used immunostaining for lyve-1 lymphatic endothelial cell marker and found that chronic physiological stress increased lymph vessel density by 3-fold (p = .03). RT-PCR was used to quantify the effects of SNS activation on genes involved in lymphangiogenesis, and found that chronic stress increased VEGF-D expression in primary mammary tumours by 60% (p = .02). Blocking SNS signalling through β2-adrenergic receptors using the β2-specific antagonist ICI118551 reduced stress-induced VEGF-D expression by 55% (p < .001). β1-adrenergic receptor-specific antagonist CGP20712A did not block stress-induced VEGF-D gene expression, suggesting the effect of stress on lymphangiogenesis may be mediated through the β2-adrenergic signalling pathway. β-adrenergic agonists had no effect on VEGF-D expression in cultured tumour cells, suggesting increased VEGF-D expression observed within primary tumours of animals subjected to restraint stress may be due to SNS signalling to tumour-associated stromal cells such as macrophages or lymphatic endothelial cells. These studies suggest that SNS signaling promotes lymphatic metastasis through β2-adrenergic regulation of primary tumour lymphangiogenesis. Ongoing studies are identifying the cellular mediators of these effects and defining the impact of blocking VEGF-D activity. Findings of these studies will provide a mechanistic foundation for translation of β-blockers and other SNS antagonists into the cancer clinic.