An increased rate of lipid synthesis in cancerous tissues has long been recognised as an important aspect of the rewired metabolism of transformed cells. However, the contribution of lipids to cellular transformation, tumour development and tumour progression, as well as their potential role in facilitating the spread of cancerous cells to secondary sites, are not yet fully understood. In this article, we review the recent findings that support the importance of lipid synthesis and metabolism in tumorigenesis. Specifically, we explore the role of aberrant lipid biosynthesis in cancer cell migration and invasion, and in the induction of tumour angiogenesis. These processes are crucial for the dissemination of tumour cells and formation of metastases, which constitute the main cause of cancer mortality.

In this study we used an unbiased functional approach to identify metabolic enzymes required for the survival of prostate cancer cells. Expression of glycolytic and lipogenic enzymes is induced in response to androgens in prostate cancer (12). Prostate cancers also show a high rate of de novo lipogenesis, and inhibition of this process decreases the viability of prostate cancer cells (13,14). The prostate epithelium secretes large amounts of citrate into the seminal fluid, which is achieved by inhibition of aconitase, resulting in a truncated tricarboxylic acid cycle. Interestingly, during transformation, aconitase is reactivated, and prostate cancer cells oxidize citrate to generate energy (15). Because many cancer cells exhibit attenuated mitochondrial oxidative metabolism (16), prostate cancer may represent a unique metabolic situation.The characterization of several metabolic features of nonmalignant and prostate cancer cell lines presented here shows that the latter are glucose dependent when cultured both in full medium (FM) or in lipid-depleted medium (LDM) and sensitive to lipid synthesis inhibition when cultured in LDM. Using these cells in a siRNA screen targeting basic glucose metabolism, lipogenesis, and amino acid biosynthesis genes, in both full medium (FM) and in LDM, we were able to identify several genes selectively required for the survival of the prostate cancer cell lines. Among these was 6-phosphofructo-2-kinase/ fructose-2,6-biphosphatase 4 (PFKFB4), an isoform of the glycolytic enzyme phosphofructokinase 2 (PFK2). A detailed analysis of the role of this gene in prostate cancer cell survival revealed that PFKFB4 is required to maintain redox balance and to support tumor growth in vivo, highlighting the importance of the metabolic regulation of bioenergetics and antioxidant production in cancer cells. RESULTS Metabolic Characterization of Prostate Cell LinesTo identify metabolic weaknesses of prostate cancer cells, we first characterized the metabolic requirements of 2 Alterations in metabolic activity contribute to the proliferation and survival of cancer cells. We investigated the effect of siRNA-mediated gene silencing of 222 metabolic enzymes, transporters, and regulators on the survival of 3 metastatic prostate cancer cell lines and a nonmalignant prostate epithelial cell line. This approach revealed significant complexity in the metabolic requirements of prostate cancer cells and identified several genes selectively required for their survival. Among these genes was 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase 4 (PFKFB4), an isoform of phosphofructokinase 2 (PFK2). We show that PFKFB4 is required to balance glycolytic activity and antioxidant production to maintain cellular redox balance in prostate cancer cells. Depletion of PFKFB4 inhibited tumor growth in a xenograft model, indicating that it is required under physiologic nutrient levels. PFKFB4 mRNA expression was also found to be greater in metastatic prostate cancer compared with primary tumors. Taken together, these resul...

BRAF inhibitors can extend progression-free and overall survival in melanoma patients whose tumors harbor mutations in BRAF. However, the majority of patients eventually develop resistance to these drugs. Here we show that BRAF mutant melanoma cells that have developed acquired resistance to BRAF inhibitors display increased oxidative metabolism and increased dependency on mitochondria for survival. Intriguingly, the increased oxidative metabolism is associated with a switch from glucose to glutamine metabolism and an increased dependence on glutamine over glucose for proliferation. We show that the resistant cells are more sensitive to mitochondrial poisons and to inhibitors of glutaminolysis, suggesting that targeting specific metabolic pathways may offer exciting therapeutic opportunities to treat resistant tumors, or to delay emergence of resistance in the first-line setting.