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Canine oral melanoma is a highly malignant cancer with a poor prognosis. Statins, commonly used drugs for treating dyslipidemia, exhibit pleiotropic anticancer effects and marked anti‐proliferative effects against melanoma cells. The anticancer effects among statins vary; in human cancers, lipophilic statins have shown stronger anticancer effects compared with hydrophilic statins. However, data on the differences in the effects of various statins on canine cancer cells are lacking, hence the optimal statins for treating canine melanoma remain unknown. Therefore, this study aimed to clarify the most effective statin by comparing the anticancer effects of hydrophilic rosuvastatin and lipophilic atorvastatin, simvastatin, fluvastatin and pitavastatin on three canine oral melanoma cell lines. Time‐dependent measurement of cell confluence showed that lipophilic statins had a stronger anti‐proliferative effect on all cell lines than hydrophilic rosuvastatin. Quantification of lactate dehydrogenase release, an indicator of cytotoxicity, showed that lipophilic statins more effectively induced cell death than hydrophilic rosuvastatin. Lipophilic statins affected both inhibition of cell proliferation and induction of cell death. The anticancer effects of statins on canine oral melanoma cells differed in the following ascending order of IC50 values: pitavastatin < fluvastatin = simvastatin < atorvastatin < rosuvastatin. The required concentration of pitavastatin was approximately 1/20th that of rosuvastatin. Among the statins used in this study, pitavastatin had the highest anticancer effect. Our results suggest lipophilic pitavastatin as the optimal statin for treating canine oral melanoma. [ABSTRACT FROM AUTHOR]

Metastatic melanoma has a very poor prognosis. Statins, 3-hydroxy-3-methyl-glutaryl-coenzyme A reductase (HMGCR) inhibitors, are cholesterol-lowering agents with a potential for cancer treatment. The inhibition of HMGCR by statins, however, induces feedback, which paradoxically upregulates HMGCR expression via sterol regulatory element-binding protein-2 (SREBP2). Dipyridamole, an antiplatelet agent, is known to inhibit SREBP2 upregulation. We aimed to demonstrate the efficacy of statin–dipyridamole combination treatment in both human and spontaneously occurring canine melanoma cell lines. The half maximal inhibitory concentration (IC50) of atorvastatin showed a 68–92% reduction when combined with dipyridamole, compared with that of atorvastatin alone. In some melanoma cell lines, cell proliferation was suppressed to almost zero by the combination treatment (≥3 μM atorvastatin). Finally, the BRAF inhibitor, vemurafenib, further potentiated the effects of the combined statin–dipyridamole treatment in BRAF V600E mutation-bearing human melanoma cell lines. In conclusion, the inexpensive and frequently prescribed statin–dipyridamole combination therapy may lead to new developments in the treatment of melanoma and may potentiate the effects of vemurafenib for the targeted therapy of BRAF V600E-mutation bearing melanoma patients. The concordance between the data from canine and human melanoma cell lines reinforces this possibility. [ABSTRACT FROM AUTHOR]

Normalization is a crucial step in gene expression analysis to avoid misinterpretation. Reverse transcription-quantitative polymerase chain reaction was used to measure the expression of 10 candidate housekeeping genes in non-differentiated (ND) and differentiated (DI) 3T3-L1 cells on days 5 and 10. We used geNorm, NormFinder, BestKeeper, RefFinder, and the ∆Ct method to evaluate expression stability. The findings revealed that (1) the expression levels of the reference genes changed over time, even in non-differentiating cells, and (2) peptidylprolyl isomerase A (Ppia) and TATA box-binding protein (Tbp) were stable reference genes for 10 days in both undifferentiated and differentiated 3T3-L1 cells. Notably, the expression of known reference genes in non-differentiating cells was altered throughout the experiment. [ABSTRACT FROM AUTHOR]

The epithelial‐to‐mesenchymal transition (EMT) is fundamental in cancer progression and contributes to the acquisition of malignant properties. The statin class of cholesterol‐lowering drugs exhibits pleiotropic anticancer effects in vitro and in vivo, and many epidemiologic studies have reported a correlation between statin use and reduced cancer mortality. We have shown previously that sensitivity to the anti‐proliferative effect of statins varies among human cancer cells and statins are more effective against mesenchymal‐like cells than epithelial‐like ones in human cancers. There have only been few reports on the application of statins to cancer therapy in veterinary medicine, and differences in statin sensitivity among canine cancer cells have not been examined. In this study, we aimed to clarify the correlation between sensitivity to atorvastatin and epithelial/mesenchymal states in 11 canine cancer cell lines derived from mammary gland, squamous cell carcinoma, lung, and melanoma. Sensitivity to atorvastatin varied among canine cancer cells, with IC50 values ranging from 5.92 to 71.5 μM at 48 h, which were higher than the plasma concentrations clinically achieved with statin therapy. Atorvastatin preferentially attenuated the proliferation of mesenchymal‐like cells. In particular, highly statin‐sensitive cells were characterized by aberrant expression of the ZEB family of EMT‐inducing transcription factors. However, ZEB2 silencing in highly sensitive cells did not induce resistance to atorvastatin. Taken together, these results suggest that high expression of ZEB is a characteristic of highly statin‐sensitive cells and could be a molecular marker for predicting whether cancers are sensitive to statins, though ZEB itself does not confer statin sensitivity. [ABSTRACT FROM AUTHOR]

Statins are cholesterol-lowering drugs often used for the treatment of dyslipidemia. Statins also exert anti-cancer effects by inhibiting hydroxymethylglutaryl-CoA reductase (HMGCR), a rate-limiting enzyme in cholesterol synthesis. We previously reported that the susceptibility to statin treatment differs among cancer cells and that functional E-cadherin expression on the plasma membrane could be a biomarker of statin sensitivity in cancer cells. However, the detailed qualitative and molecular differences between statin-sensitive and statin-resistant cancer cells remain unclear. Here, we explored novel parameters related to statin sensitivity by comparing gene expression profiles and metabolite contents between statin-sensitive and statin-resistant lung cancer cell lines. We found that the expression of most cholesterol synthesis genes was lower in the statin-sensitive cancer cell line, HOP-92, than in the statin-resistant cancer cell line, NCI-H322M. Moreover, HOP-92 cells originally exhibited lower levels of CoA and HMG-CoA. Additionally, atorvastatin decreased the mRNA expression of PANK2, a rate-limiting enzyme in CoA synthesis. Atorvastatin also reduced the mRNA levels of the cholesterol esterification enzyme SOAT1, which was consistent with a decrease in the ratio of cholesterol ester to total cholesterol in HOP-92 cells. Our data suggest that the cholesterol synthetic flow and CoA content may be limited in statin-sensitive cancer cells. We also suggest that CoA synthesis and cholesterol storage may fluctuate with atorvastatin treatment in statin-sensitive cancer cells.