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dc.contributor.authorMunir, Rimsha-
dc.description.abstractMalignant cells display multiple alterations in their lipid metabolism pathways. These modifications are known to support cancer cell progression, survival, and maintenance. Most of the previous works have studied lipid metabolism in cancer cells using a conventional two-dimensional (2D) cell culture system. However, there is a growing consensus among cancer biologists that 2D cell culture system is not accurate representative of in vivo tumour environment. Research reports in past few decades have suggested that multicellular tumour spheroids generated by various 3D cell culture systems are more stringent and better representative models of in vivo tumour growth. However, the evidence on significance of applying 3D spheroids models in studying cellular metabolism is lacking. The main aim of the presented thesis was to study the influence of metabolic stress on lipid metabolism and lipid profile of cancer cells in both cell culture systems (3D & 2D). In the initial phases of the presented work cell proliferations rates were compared between 2D and 3D cell cultures. It was observed that cancer cell proliferation rates were differentially influenced by cell culture model systems for instance; HCT-116 (colorectal cancer cell line) cells display decreased proliferates rates under 3D system and HepG2 (hepatocellular carcinoma cell line) cells display increased proliferation rates under 3D system. Next, the effects of serum-deprivation on cell proliferation rates were studied. It was observed that serum-deprivation significantly affected the proliferation of HCT-116 and HepG2 cells both in cell culture systems. However, HCT-116 cells display increased sensitivity to serum-deficiency. This data indicated that the proliferation capacity of the given cell lines was associated with the ability to deal with metabolic stress under 2D or 3D systems. HCT-116 coped better with metabolic stress in 2D system while HepG2 in 3D system. Summary X In the experiments focused on the lipid metabolism of cancer cells first the lipid-load was compared between cells cultivated under both cell culture systems (2D & 3D). It was observed that HCT-116-cells cultivated as 3D spheroids accumulated slightly elevated levels of triglycerides (TGs) in comparison to the monolayer (2D) culture. Next the effects of serum and oxygen scarcity on cellular lipid-load were examined. In 2D cultures low-serum environment induces significant increase in cellular triglyceride levels in both HepG2 and HCT-116 cells. On the other hand, hypoxia induced almost no effect in TG accumulation in both cell lines. Spheroidal cultures of HCT-116 cells showed significantly increased TG levels both in low serum and hypoxic conditions as compared to normal culture conditions. Hence, in 3D cell culture system the TG-accumulation was induced also in hypoxic conditions –the effect that was not observed in 2D cell cultures. This effect is of particular importance because previous research reports have indicated that severe-hypoxia in combination with nutrient-deprivation may induce TG accumulation while mild-hypoxia may not have this effect. It can be suggested that 3D cell culture system aggravates the hypoxic stress and induces TG-accumulation in HCT 116 cells. For more nuanced analyses the effect of serum and O2 deprivation on lipidomic profiles of cancer cells were also examined. It was observed that the composition of triglycerides (TGs), diacylglycerols (DGs), cholesterol esters (CE), phosphatidylcholines (PC) and phosphatidylethanolamines (PEs) remained unchanged in SW480 (primary colon cancer cell line) cells under low serum or hypoxic culture conditions. The SW620 (metastatic cancer cell line) cells displayed marked increase in proportion of phosphatidylethanolamines (PEs) harboring one SFA (1 SFA) to in low serum culture condition. The composition of other lipid sub-classes was not affected by low serum and hypoxia in SW620 cells. The metabolic gene expression profiles were also examined to study the molecular underpinning of the aforementioned alterations in lipid profiles of Summary XI cancer cells. As a first line of investigation, the lipid metabolism associated genes that are shown to be differentially regulated in malignant cells cultivated under metabolic stress were identified. To achieve that extensive literature survey was performed and, for the first time, the fragmented information that was scattered through a wide range of research works was gathered. Next, the expression of selected markers from major lipid metabolism pathway was determined that included (a) Fatty acid synthase (FASN, enzyme of the fatty acid synthesis pathway), (b) 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR, enzyme of the mevlonate pathway), (c) Lipoprotein lipase (LPL, a lipolytic enzyme that catalyzes the extracellular lipolysis of TG-rich lipoproteins) and (d) Monoacyl glycerol lipase (MGLL, enzyme that hydrolyzes intracellularly stored triglyceride). The only significant change was increase in the expression of LPL under serum deprived conditions. The expression pattern of the selected metabolic markers was also compared in 2D versus 3D cultures. It was observed that expression of FASN and HMGCR was increased, whereas expression of LPL and MGLL were decreased under 3D cell culture system. The findings of presented work provide better understanding for the intricate interplay between tumour microenvironment and lipid profiles in cancer cells.en_US
dc.description.sponsorshipHigher Education Commission Pakistanen_US
dc.publisherUniversity of the Punjab , Lahoreen_US
dc.subjectBiological & Medical Sciencesen_US
dc.subjectMicrobiology and Molecular Geneticsen_US
dc.title2D Versus 3D Cells Culture: Studying the Metabolic Pathways in Cancer Cellsen_US
Appears in Collections:PhD Thesis of All Public / Private Sector Universities / DAIs.

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