Fluvastatin Plus Dipyridamole Suppresses Canine Hemangiosarcoma Growth in Patient‐Derived Xenograft Models Through Lactate Dehydrogenase‐Associated Cholesterol/Lipid Metabolism

ABSTRACT

Tumour cells commonly exhibit aerobic glycolysis and produce lactate despite oxygen availability. Lactate dehydrogenase (LDH) catalyses pyruvate‐lactate interconversion and regulates intracellular lactate levels. Endothelial cells also depend on glycolysis for ATP production, which prompted us to investigate LDH in canine hemangiosarcoma (HSA), a malignant endothelial tumour. We inhibited LDH with (R)‐GNE‐140 or sodium oxamate in two canine HSA cell lines (HU‐HSA‐2 and HU‐HSA‐3) and generated HU‐HSA‐3 clones with knockout of LDHA or LDHB to evaluate the effects of LDH perturbation. (R)‐GNE‐140 and sodium oxamate suppressed proliferation and reduced global histone lactylation levels in both cell lines. mRNA‐sequencing (mRNA‐seq) of (R)‐GNE‐140‐treated HU‐HSA‐2 cells identified cholesterol/lipid metabolism‐related gene sets among the top negatively enriched pathways. Representative cholesterol/lipid metabolism genes such as SREBF2 , SQLE and LDLR responded differently depending on cell lines and inhibitors. (R)‐GNE‐140 decreased these genes in HU‐HSA‐2 but not HU‐HSA‐3, whereas sodium oxamate decreased them in HU‐HSA‐3 with limited effects in HU‐HSA‐2. In HU‐HSA‐3, LDHA and LDHB knockout clones decreased SREBP2 expression and reduced the number of lipid droplets. Fluvastatin, a cholesterol metabolism inhibitor, inhibited HSA cell growth in vitro but did not significantly suppress tumour growth in two HSA patient‐derived xenograft (PDX) models. In contrast, combined fluvastatin and dipyridamole treatment inhibited proliferation in vitro and tumour growth in PDX models. Collectively, these results suggest a context‐dependent association between LDH and cholesterol/lipid metabolism in canine HSA cell lines and provide a rationale for further evaluation of combined cholesterol pathway inhibition.