Canonical fatty acid metabolism describes specific enzyme-substrate interactions that result in products with well-defined chain lengths, degree(s), and positions of unsaturation. Deep profiling of lipids across a range of prostate cancer cell lines reveals a variety of fatty acids with unusual site(s) of unsaturation that are not described by canonical pathways. The structure and abundance of these unusual lipids correlate with changes in desaturase expression and are strong indicators of cellular phenotype. Gene silencing and stable isotope tracing demonstrate that direct Δ6 and Δ8 desaturation of 14:0 (myristic), 16:0 (palmitic), and 18:0 (stearic) acids by FADS2 generate new families of unsaturated fatty acids (including n-8, n-10, and n-12) that have rarely-if ever-been reported in human-derived cells. Isomer-resolved lipidomics reveals the selective incorporation of these unusual fatty acids into complex structural lipids and identifies their presence in cancer tissues, indicating functional roles in membrane structure and signaling.

Metabolic reprogramming and energetic rewiring are hallmarks of cancer that fuel disease progression and facilitate therapy evasion. The remodelling of oxidative phosphorylation and enhanced lipogenesis have previously been characterised as key metabolic features of prostate cancer (PCa). Recently, succinate-dependent mitochondrial reprogramming was identified in high-grade prostate tumours, as well as upregulation of the enzymes associated with branched-chain amino acid (BCAA) catabolism. In this study, we hypothesised that the degradation of the BCAAs, particularly valine, may play a critical role in anapleurotic refuelling of the mitochondrial succinate pool, as well as the maintenance of intracellular lipid metabolism. Through the suppression of BCAA availability, we report significantly reduced lipid content, strongly indicating that BCAAs are important lipogenic fuels in PCa. This work also uncovered a novel compensatory mechanism, whereby fatty acid uptake is increased in response to extracellular valine deprivation. Inhibition of valine degradation via suppression of 3-hydroxyisobutyryl-CoA hydrolase (HIBCH) resulted in a selective reduction of malignant prostate cell proliferation, decreased intracellular succinate and impaired cellular respiration. In combination with a comprehensive multi-omic investigation that incorporates next-generation sequencing, metabolomics, and high-content quantitative single-cell imaging, our work highlights a novel therapeutic target for selective inhibition of metabolic reprogramming in PCa.

Metabolic reprogramming is a hallmark of cancer and fundamental for disease progression. The remodelling of oxidative phosphorylation and enhanced lipogenesis are key characteristics of prostate cancer (PCa). Recently, succinate-dependent mitochondrial reprogramming was identified in high-grade prostate tumours with upregulation of enzymes associated with branched-chain amino acid (BCAA) catabolism. We hypothesised that the degradation of BCAAs, particularly valine may play a critical role in anapleurotic refuelling of the mitochondrial succinate pool. Through suppression of valine availability, we report strongly reduced lipid content despite compensatory upregulation of fatty acid uptake, indicating valine is an important lipogenic fuel in PCa. Inhibition of the enzyme 3-hydroxyisobutyryl-CoA hydrolase (HIBCH) also resulted in selective inhibition of cellular proliferation of malignant but not benign prostate cells and impaired succinate production. In combination with a comprehensive multi-omic investigation of patient and cell line data, our work highlights a therapeutic target for selective inhibition of metabolic reprogramming in PCa.

Background: The cytotoxic agent eribulin has been shown to promote EMT reversion, reduce treatment resistance, and potentially enhance responses to a range of therapeutic agents. Methods: We examined the effects of eribulin in patient-derived breast cancer tissues and a phenotypically heterogeneous breast cancer cell line to assess EMT and chemotherapy response. Results: Nanostring-based analysis of EMT-associated gene expression in breast cancers from patients receiving standard-of-care TAC neoadjuvant chemotherapy compared to a cohort receiving neoadjuvant eribulin (NeoEribulin trial) showed markedly reduced expression of EMT markers in cancers treated with eribulin versus TAC. Through single-cell immunofluorescent imaging and analysis, we identified that HCC38 triple-negative breast cancer (TNBC) cells exhibited a shift towards an epithelial-like state marked by E-cadherin upregulation following acute eribulin exposure, but not with other chemotherapeutic agents. Investigation of primary breast cancer cultures derived from pre-neoadjuvant biopsies also revealed that HER2-enriched primary breast cancer cells displayed heightened chemosensitisation to doxorubicin (Adriamycin), which was not recapitulated in TNBC cultures. Conclusions: Our data highlight the presence of contextual parameters which govern the degree of EMT regulation by eribulin.