LDH-A influences hypoxia-inducible factor 1α (HIF1 α) and is critical for growth of HT29 colon carcinoma cells in vivo

Serum lactate dehydrogenase (LDH) is a well-known clinical surrogate parameter. A high activity of LDH is associated with a poor prognosis in different tumor types. Here we demonstrate by a gene silencing approach that LDH-A is critical for in vivo but not in vitro growth of HT29 colon carcinoma cells. We provide evidence that the suppression of the LDH-A gene leads to an increased level of hypoxia inducible factor 1 alpha (HIF1 alpha) but in consequence not to an increase of HIF1 regulated proteins such as carbonic anhydrase IX (CAIX), vascular endothelial growth factor (VEGF), prolyl-hydroxylase 2 (PHD2), and factor-inhibiting HIF (FIH) in cell cultures and tumor lysates. This effect is independent of LDH activity in vivo. We conclude that LDH-A has an influence on the activity of HIF1 alpha and thus on the adaptation of cells to a hypoxic tumor microenvironment in HT29 colon cells. We suggest the use of LDH-M as a potential therapeutic target for anticancer treatment.