Association between white opaque substance under magnifying colonoscopy and lipid droplets in colorectal epithelial neoplasms

Lipid droplets provide metabolic flexibility for cancer progression

A hallmark of cancer cells is their remarkable ability to efficiently adapt to favorable and hostile environments. Due to a unique metabolic flexibility, tumor cells can grow even in the absence of extracellular nutrients or in stressful scenarios. To achieve this, cancer cells need large amounts of lipids to build membranes, synthesize lipid-derived molecules, and generate metabolic energy in the absence of other nutrients. Tumor cells potentiate strategies to obtain lipids from other cells, metabolic pathways to synthesize new lipids, and mechanisms for efficient storage, mobilization, and utilization of these lipids. Lipid droplets (LDs) are the organelles that collect and supply lipids in eukaryotes and it is increasingly recognized that the accumulation of LDs is a new hallmark of cancer cells. Furthermore, an active role of LD proteins in processes underlying tumorigenesis has been proposed. Here, by focusing on three major classes of LD-resident proteins (perilipins, lipases, and acyl-CoA synthetases), we provide an overview of the contribution of LDs to cancer progression and discuss the role of LD proteins during the proliferation, invasion, metastasis, apoptosis, and stemness of cancer cells.

Stearoyl-CoA desaturase 1 inhibition impairs triacylglycerol accumulation and lipid droplet formation in colorectal cancer cells

Increases in fatty acid (FA) biosynthesis meet the higher lipid demand by intensely proliferating cancer cells and promoting their progression. Stearoyl-CoA desaturase 1 (SCD1) is the key enzyme in FA biosynthesis, converting saturated FA (SFA) into monounsaturated FA (MUFA). Increases in the MUFA/SFA ratio and SCD1 expression have been observed in cancers of various origins and correlate with their aggressiveness. However, much is still unknown about the SCD1-dependent molecular mechanisms that promote specific changes in metabolic pathways of cancer cells. The present study investigated the involvement of SCD1 in shaping glucose and lipid metabolism in colorectal cancer (CRC) cells. Excess FAs that derive from de novo lipogenesis are stored in organelles, called lipid droplets (LDs), mainly in the form of triacylglycerol (TAG) and cholesteryl esters. LD accumulation is associated with key features of cancer development and progression. Consistent with our findings, the pharmacological inhibition of SCD1 activity affects CRC cell viability and impairs TAG accumulation and LD formation in these cells through the activation of lipolytic and lipophagic pathways. We showed that SCD1 suppression affects crucial lipogenic processes that promote lipid accumulation in CRC cells but in a sterol regulatory element-binding protein 1-independent manner. We propose that adenosine monophosphate-activated protein kinase contributes to these changes through the activation of lipolysis and inhibition of TAG synthesis. We also provide evidence of the involvement of SCD1 in the regulation of glucose uptake and utilization in CRC cells. These findings underscore the importance of SCD1 in regulating cellular processes that promote cancer development and progression.

Biogenesis and Breakdown of Lipid Droplets in Pathological Conditions

Lipid droplets (LD) have long been considered as mere fat drops; however, LD have lately been revealed to be ubiquitous, dynamic and to be present in diverse organelles in which they have a wide range of key functions. Although incompletely understood, the biogenesis of eukaryotic LD initiates with the synthesis of neutral lipids (NL) by enzymes located in the endoplasmic reticulum (ER). The accumulation of NL leads to their segregation into nanometric nuclei which then grow into lenses between the ER leaflets as they are further filled with NL. The lipid composition and interfacial tensions of both ER and the lenses modulate their shape which, together with specific ER proteins, determine the proneness of LD to bud from the ER toward the cytoplasm. The most important function of LD is the buffering of energy. But far beyond this, LD are actively integrated into physiological processes, such as lipid metabolism, control of protein homeostasis, sequestration of toxic lipid metabolic intermediates, protection from stress, and proliferation of tumours. Besides, LD may serve as platforms for pathogen replication and defense. To accomplish these functions, from biogenesis to breakdown, eukaryotic LD have developed mechanisms to travel within the cytoplasm and to establish contact with other organelles. When nutrient deprivation occurs, LD undergo breakdown (lipolysis), which begins with the LD-associated members of the perilipins family PLIN2 and PLIN3 chaperone-mediated autophagy degradation (CMA), a specific type of autophagy that selectively degrades a subset of cytosolic proteins in lysosomes. Indeed, PLINs CMA degradation is a prerequisite for further true lipolysis, which occurs via cytosolic lipases or by lysosome luminal lipases when autophagosomes engulf portions of LD and target them to lysosomes. LD play a crucial role in several pathophysiological processes. Increased accumulation of LD in non-adipose cells is commonly observed in numerous infectious diseases caused by intracellular pathogens including viral, bacterial, and parasite infections, and is gradually recognized as a prominent characteristic in a variety of cancers. This review discusses current evidence related to the modulation of LD biogenesis and breakdown caused by intracellular pathogens and cancer.

Early stage clear cell adenocarcinoma coexisting with tubular adenoma and adenoma with clear cell change in the colon

Primary clear cell adenocarcinoma (CCA) of the colorectum is rare. We report a case of a 57-year-old man with early-stage CCA with conventional tubular adenoma and tubular adenoma with clear cell change in the transverse colon, diagnosed with image-enhanced endoscopy. The tumor was then treated with endoscopic submucosal dissection. The endoscopic findings characteristic of clear cell adenoma/adenocarcinoma could not be identified. Therefore, similar diagnostic tools as for conventional colorectal adenoma/cancer were considered. The pathogenesis of the clear cell change was unknown, but it might appear with the progression of the malignancy.

Lipid droplet and its implication in cancer progression

Lipid droplets (LDs) are a kind of organelle that is commonly found in eukaryotic cells to store lipids, which encompass a hydrophobic core composed of a single layer of phospholipids and neutral lipids (mainly including triacylglycerol (TAG) and cholesterol ester (CE)) as well as a small amount of proteins. LD accumulation is gradually recognized as a prominent characteristic in a variety of cancers and attracts increasing attention on this field. In this article, we not only summarize the composition, synthesis and decomposition of LD, but also highlight its role in carcinogenesis and malignant development of cancers.

Lipid droplets: platforms with multiple functions in cancer hallmarks

Lipid droplets (also known as lipid bodies) are lipid-rich, cytoplasmic organelles that play important roles in cell signaling, lipid metabolism, membrane trafficking, and the production of inflammatory mediators. Lipid droplet biogenesis is a regulated process, and accumulation of these organelles within leukocytes, epithelial cells, hepatocytes, and other nonadipocyte cells is a frequently observed phenotype in several physiologic or pathogenic situations and is thoroughly described during inflammatory conditions. Moreover, in recent years, several studies have described an increase in intracellular lipid accumulation in different neoplastic processes, although it is not clear whether lipid droplet accumulation is directly involved in the establishment of these different types of malignancies. This review discusses current evidence related to the biogenesis, composition and functions of lipid droplets related to the hallmarks of cancer: inflammation, cell metabolism, increased proliferation, escape from cell death, and hypoxia. Moreover, the potential of lipid droplets as markers of disease and targets for novel anti-inflammatory and antineoplastic therapies will be discussed.