Dinamika tvorbe in razgradnje lipidnih kapljic pri metaboličnem stresu v rakavih celicah

Hruševar, Petra (author), Petan, Toni (mentor), Novinec, Marko (co-mentor)

Lipidne kapljice (LK) so nedavno odkriti dinamični in neodvisni organeli, prisotni v večini celic. Dolgo so veljale zgolj za inertna mesta skladiščenja lipidov v celici, vendar so študije dokazale, da gre za pomembne regulatorje presnove lipidov, ki med drugim nadzorujejo privzem maščobnih kislin iz okolja, njihovo razporeditev znotraj celice, shranjevanje in uporabo za različne namene v celici. Delujejo tudi kot pomembni regulatorji celičnega odziva na stres, sodelujejo pri vzdrževanju energetske in redoks homeostaze, integritete membran in organelov in pri zaščiti pred lipotoksičnostjo. Sposobnost rakavih celic, da preživijo stresne pogoje, kot sta pomanjkanje kisika in hranil, je ključna za rast tumorjev in obenem šibka točka, ki jo želimo uporabiti v terapevtske namene. Raziskave so pokazale, da je ena izmed ključnih lastnosti, ki rakavim celicam omogoči preživetje kljub celičnem stresu, sinteza LK [4]. Vzroki in mehanizmi tvorbe ter razgradnje LK ob različnih pogojih rasti rakavih celic še niso povsem pojasnjeni. Namen magistrskega dela je bil preučiti vpliv sprememb v dinamiki LK na celično rast in proliferacijo celic raka dojke MDA-MB-231. Predpostavili smo, da bomo na dinamiko LK in na rast celic vplivali bodisi z inhibicijo delovanja encimov diacilglicerol aciltransferaz (DGAT) 1 in 2, ki katalizirata sintezo trigliceridov in ki je predpogoj za tvorbo LK, bodisi s prekomernim izražanjem adipozne triglicerid lipaze (ATGL), ki je ključna za lipolizo trigliceridov in razgradnjo LK. Pokazali smo, da hkratna inhibicija encimov DGAT1 in DGAT2 bistveno zmanjša število LK v celicah raka dojke. Prav tako smo ugotovili, da inhibicija encima DGAT1, ne pa tudi DGAT2, upočasni proliferacijo celic raka dojke in zmanjša njihovo sposobnost tvorbe neodvisnih kolonij. Ugotovili smo tudi, da prekomerno izražanje lipaze ATGL nima bistvenega vpliva na vsebnost nevtralnih lipidov v celicah raka dojke, ima pa stimulativen učinek na njihovo sposobnost proliferacije. Naši rezultati torej kažejo, da sta tvorba in razgradnja trigliceridov pomembna za rast in delitev celic raka dojke. Ciljanje metabolizma lipidnih kapljic preko vpliva na encime DGAT in ATGL je torej zanimivo za nadaljnje študije v smeri odkrivanja novih terapevtskih pristopov pri raku.

• Language: Slovenian
• Keywords: lipidne kapljice, lipoliza, rak dojke, stradanje, metabolični stres, diacilglicerol aciltransferaza, adipozna triglicerid lipaza, proliferacija
• Work type: Master's thesis/paper
• Typology: 2.09 - Master's Thesis
• Organization: FKKT - Faculty of Chemistry and Chemical Technology
• Year: 2021
• PID: 20.500.12556/RUL-132248
• COBISS.SI-ID: 88529667
• Publication date in RUL: 19.10.2021

Secondary language

• Language: English
• Title: Dynamics of lipid droplet biogenesis and breakdown in cancer cells under metabolic stress

Abstract

Lipid droplets (LDs) are recently recognized dynamic organelles present in most eukaryotic cells. For a long time, they were considered to be inert lipid storage sites, but studies have shown that they are important regulators of lipid metabolism, which control the uptake of fatty acids from the environment, their distribution, storage and use for various purposes within the cell. Moreover, they act as important modulators of the cellular response to stress, being involved in maintaining energy and redox homeostasis, membrane and organelle integrity, and in the cellular protection against lipototoxicity. The ability of cancer cells to survive stressful conditions, such as the lack of oxygen and nutrients, is crucial for tumor growth and a vulnerability that may be exploited for therapeutic purposes. One of the key characteristics that enable cancer cell survival during stress is the biogenesis of LDs, but the causes and mechanisms of LD formation and breakdown under different growth conditions have not yet been fully elucidated. The major goal of this work was to examine the impact of changes in LD dynamics on the growth and proliferation of MDA-MB-231 breast cancer cells. We hypothesized that LD turnover and cell growth would be affected either by inhibition of diacylglycerol acyltransferases (DGATs) 1 and 2 that catalyze triglyceride synthesis, which is a prerequisite for LD formation, or by overexpression of adipose triglyceride lipase (ATGL), which is crucial for triglyceride lipolysis and LD degradation. We found that the inhibition of DGAT1 and DGAT2 enzymes significantly reduced the number of LDs in breast cancer cells. We also found that inhibition of DGAT1, but not DGAT2, slows the proliferation of breast cancer cells and reduces their ability to form independent colonies. On the other hand, our data show that ectopic overexpression of ATGL does not have a significant effect on neutral lipid content in breast cancer cells, but stimulates their proliferation. Our results therefore suggest that triglyceride synthesis and lipolysis are important for the growth and division of breast cancer cells. Targeting the major LD metabolism enzymes DGAT and ATGL is therefore of interest for further studies towards the discovery of new therapeutic approaches in cancer.

• Keywords: lipid droplets, lipolysis, breast cancer, starvation, metabolic stress, diacylglycerol acyltransferase, adipose triglyceride lipase, proliferation