Post-transcriptional regulation of cancer by a metabolic pathway: modulation of HuR by the mevalonate pathway

Background: Mevalonate (MVA) pathway, the metabolic pathway essential for producing cholesterol, is inhibited by statins to manage hypercholesterolemia and reduce the risk of cardiovascular diseases. Increasing evidence has shown that dysregulation of this pathway also contributes to cancer development and progression. Its role in cancer has been well established through its production of isoprenoid intermediates enabling the prenylation and activation of small GTPases that drive tumor cell proliferation, migration, and metastasis. While the direct prenylation-dependent effect of the MVA pathway have been well characterized, there is growing evidence that it can also indirectly affect other oncogenic regulators. In this study, we aim to determine whether the MVA pathway is involved in regulating HuR, an RNA-binding protein that plays a central role in stabilizing numerous oncogenic transcripts. Demonstrating an MVA-dependent influence on HuR would establish a promising regulatory mechanism can modulate multiple oncogenic pathways simultaneously. Also, as HuR is consistently upregulated across diverse cancer types, defining how the MVA pathway affects HuR in a few cancer types will lay the foundation for generalizing these findings to other malignancies. Methods & Results: Cell viability was assessed by MTT assay to determine the IC₅₀ of simvastatin in MDA-MB-231 breast cancer cells. Cells were subsequently treated with simvastatin at concentrations below, at, and above the IC₅₀ for 24 and 48 hours. HuR protein expression was then measured by Western blot. We observed a clear dose-dependent reduction in cell viability, along with a pronounced suppression of HuR expression at extremely low simvastatin concentrations (nanomolar doses) compared with vehicle control at the 24-hour timepoint. To determine whether the effect of simvastatin on HuR is specifically mediated through inhibition of the mevalonate pathway, rescue experiments are being performed in which mevalonate and isoprenoid intermediates are added following simvastatin treatment. To evaluate downstream consequences of HuR suppression, Western blot analysis is being performed for Cyclin B1 and BCL2, two HuR-regulated targets involved in cell-cycle progression and apoptosis. Transcript levels of HuR, Cyclin B1, and BCL2 are being quantified by qPCR to validate the observed protein-level changes. Also, as HuR overexpression is frequently accompanied by its cytoplasmic accumulation, immunofluorescence staining is being performed to assess HuR distribution and quantify the nuclear/cytoplasmic ratio in treated cells. Conclusions: Our findings demonstrate that mevalonate-pathway inhibition reduces HuR expression in breast cancer cells, supporting a mechanistic connection between metabolic signaling and post-transcriptional control of oncogenic pathways. This abstract was revised with AI assistance.