Submitted to: American Association of Cancer Research
Publication Type: Abstract only
Publication Acceptance Date: 1/17/2011
Publication Date: 4/3/2011
Citation: Welch, D.R., Beck, B.H., Feeley, K.P., Diers, A.R., Vaidya, K., Nash, K., Bodenstine, T., Thomas, J. 2011. The KISS1 metastasis suppressor appears to reverse the ‘Warburg Effect’ [abstract]. American Association of Cancer Research. p.965. Interpretive Summary:
Technical Abstract: In 1924, Otto Warburg described the preference of cancer cells for glycolytic metabolism, even under normoxic conditions and that these metabolic changes directly correlate with malignant potential of several cancers. Although its purpose remains unclear, the “Warburg Effect” is thought to confer proliferative and survival advantages by increasing uptake of nutrients into biomass. The KISS1 metastasis suppressor protein is secreted and proteolytically cleaved into so-called kisspeptins (KP) that block the colonization of metastatic C8161.9 human melanoma cells at secondary sites. We asked whether secreted KISS1 mediates its inhibitory effects on metastatic growth through regulation of the "Warburg Effect." Comparing multiple bioenergetic and metabolic aspects of glucose metabolism in C8161.9 +/- KISS1 showed that all KISS1-secreting clones had significantly (P<0.05) reduced invasion (60%) and reduced lactate production (100 mg/dL vs. 128 mg/dL). Irrespective of cell density, KISS1-expressing cells had a significantly higher extracellular pH (pHe=7.2) compared to cells transfected with empty vector or cells transfected with KISS1 harboring a deleted signal sequence (deltaSS; pHe=6.7). Utilizing a Seahorse (c) bioanalyzer, reduced extracellular acidification by KISS1 cells was verified concomitant with increased O2 consumption. Interestingly, mitochondrial reserve capacity, an indicator thought to reflect a cell’s ability to cope with oxidative stresses, was also elevated in KISS1-expressing cells. Using mitochondrial-selective fluorescent probes, C8161.9KISS1 melanoma and MDA-MB-435KISS1 breast carcinoma cells have approximately 30% more mitochondria compared to empty vector or KISS1 deltaSS-expressing cells. Increased mitochondrial number in KISS1-expressing cells was correlated with higher levels of PGC-1a, a major mitochondrial biogenesis regulatory molecule, which was confirmed using siRNA to KISS1. Expression of KISS1 also protected C8161.9 cells from dichloroacetate-induced cell death. Unexpectedly, addition of KP10 to C8161.9 cells did not alter pHe, raising questions regarding the mechanism by which KISS1/KP alter PGC-1a in the absence of KISS1 receptor expression in the tumor cells. Nonetheless, these data appear to directly connect changes in mitochondrial number, metabolic pathway regulation and the metastatic process. Future studies will determine whether the increase in mitochondrial number is directly responsible for the change in glycolytic metabolism and whether these changes are necessary for KISS1's effects on metastatic growth.