The malignant progression of pancreatic ductal adenocarcinoma (PDAC) is accompanied by a profound desmoplasia, which forces proliferating tumor cells to metabolically adapt to this new microenvironment. We established the PDAC metabolic signature to highlight the main activated tumor metabolic pathways. Comparative transcriptomic analysis identified lipid-related metabolic pathways as being the most highly enriched in PDAC, compared with a normal pancreas. Our study revealed that lipoprotein metabolic processes, in particular cholesterol uptake, are drastically activated in the tumor. This process results in an increase in the amount of cholesterol and an overexpression of the low-density lipoprotein receptor (LDLR) in pancreatic tumor cells. These findings identify LDLR as a novel metabolic target to limit PDAC progression. Here, we demonstrate that shRNA silencing of LDLR, in pancreatic tumor cells, profoundly reduces uptake of cholesterol and alters its distribution, decreases tumor cell proliferation, and limits activation of ERK1/2 survival pathway. Moreover, blocking cholesterol uptake sensitizes cells to chemotherapeutic drugs and potentiates the effect of chemotherapy on PDAC regression. Clinically, high PDAC Ldlr expression is not restricted to a specific tumor stage but is correlated to a higher risk of disease recurrence. This study provides a precise overview of lipid metabolic pathways that are disturbed in PDAC. We also highlight the high dependence of pancreatic cancer cells upon cholesterol uptake, and identify LDLR as a promising metabolic target for combined therapy, to limit PDAC progression and disease patient relapse.is one of the deadliest cancers, rated as the fourth leading cause of cancerrelated death in the United States and Europe, with a 5-y survival rate of about 4% and a median survival of less than 6 mo (1). In the absence of early warning signs, only 15% of patients with localized PDAC can be cured by surgical resection. For the remaining patients diagnosed with late-stage pancreatic cancer with metastatic disease, the current chemotherapy with gemcitabine (GEM) is mainly palliative and remains the standard treatment despite limited benefits (5.6-mo survival) (2). Recent advances in treatment, such as combined regimens using fluorouracil, leucovorin, irinotecan, and oxaliplatin, or Nab-paclitaxel plus GEM, conferred a survival advantage compared with GEM alone (2).The low response rate to chemotherapy is a result, in part, to the presence of a dense stroma, characterized by fibrillar networks around tumoral cells that compress vasculature and limit oxygen, nutrient, and drug delivery to the cells. A fundamental feature of tumoral cells is that they undergo metabolic reprogramming in response to these environmental constraints. Advances in tumor metabolism research reveal that PDAC cells primarily rely on glucose and glutamine catabolism to fulfill bioenergetic need and provide macromolecules required for growth and proliferation (3-5). However, metabolic reprogramming is a complex...

Breast cancer stem cells (bCSCs) have been implicated in tumor progression and therapeutic resistance; however, the molecular mechanisms that define this state are unclear. We have performed two microRNA (miRNA) gain- and loss-of-function screens to identify miRNAs that regulate the choice between bCSC self-renewal and differentiation. We find that micro-RNA (miR)-600 silencing results in bCSC expansion, while its overexpression reduces bCSC self-renewal, leading to decreased in vivo tumorigenicity. miR-600 targets stearoyl desaturase 1 (SCD1), an enzyme required to produce active, lipid-modified WNT proteins. In the absence of miR-600, WNT signaling is active and promotes self-renewal, whereas overexpression of miR-600 inhibits the production of active WNT and promotes bCSC differentiation. In a series of 120 breast tumors, we found that a low level of miR-600 is correlated with active WNT signaling and a poor prognosis. These findings highlight a miR-600-centered signaling network that governs bCSC-fate decisions and influences tumor progression.