Insights into the cellular lipid cascade of prostate cells explored using infrared microspectroscopy

Background: Although prostate cancer (PCa) is the most diagnosed cancer in men worldwide, there is geographical variance in both incidence and morbidity, with higher levels in developed "Western Diet" countries. In particular the high levels of the omega-6 polyunsaturated fatty acid, arachidonic acid (AA), in Western diets has been shown to promote aggressive PCa in vitro. However the exact mechanism through which AA induces the aggressive phenotype has not been fully characterised. Methods: In this study Fourier transform infrared (FTIR) imaging coupled with fluorescence microscopy (FM), is used to follow AA metabolism in PCa cell lines. This is achieved using partially deuterated AA, with a distinctive C-D stretch seen at 2251 cm^-1 providing molecular specificity, coupled with Nile Red Fluorescence imaging. Results: We show that, invasive cell lines PC-3, LNCaP C4-2B and DU145 readily uptake and metabolise AA, producing prostaglandins via the COX-2 pathway. Inhibition of the COX-2 pathway with either NS938 or the omega-3 polyunsaturated fatty acid Docosahexaenoic acid (DHA), reduces the invasive stimulus of AA and blocks its uptake. Conclusion: This demonstrates that FTIR imaging can be utilised to follow metabolomics processes within a PCa model and provide an insight to the molecular pathways underlying the cancer metabolome. Additionally, these works provide key insights into the rapid uptake of AA within certain invasive cell lines of prostate cancer, suggesting that AA exposure initiates early cellular responses prior to the uptake and processing of lipids within the cells.