Abstract 1744: Role of lipid bodies on cell cycle progression.
Authors: de Souza Cruz André Luiz , Bozza Patricia Torres , de Biaso Viola João Paulo 
Published: August 2014

Abstract
Background: Lipid bodies (also known as lipid droplets) are organelles involved in lipid turnover, membrane traffic and intracellular signaling. Lipogenesis has been associated with poor prognosis in several neoplasic diseases, suggesting a role for these organelles in cancer development. We have previously reported that lipid bodies are centrally involved in prostaglandin E2 synthesis and cell proliferation in colon cancer cells, and may have implications to colon adenocarcinoma pathogenesis (Cancer Res. 68:1732, 2008). Based on this data, we investigated the role of lipid bodies in the regulation of cell cycle progression.
Materials and Methods: NIH3T3 cells were synchronized through combination of confluence and serum starvation, and progression through cell cycle was assayed before or after 12, 24, 36 or 48 hours of serum supplementation by propidium iodide staining, by western blot analysis of cell cycle proteins, and by qtPCR to assess cyclins mRNA expression. Lipid bodies regulation were assayed in the times indicated, analyzing sub cellular localization through immunofluorescence microscopy using Bodipy® staining, and quantification through flux citometry and immunofluorescence microscopy, using respectively Bodipy® or Oil Red O staining. NIH3T3 were synchronized with thymidine to assess regulation of lipid bodies through S cell cycle phase, and the transformed cell lineage NIH3T3-H-rasV12 were also maintained in confluence and serum starvation for lipid bodies’ analysis.
Results: Cell cycle analysis revealed that upon serum supplementation NIH3T3 cells reached S phase after 24 hours, following to G2/M phase after 36-48 hours. In accordance to this data, maximum hyperphosphorylation of pRb and a peak expression of cyclin A protein were observed at 24 hours of serum supplementation, along with histone H3 phosphorylation after 48 hours. Also, mRNA expression analysis of cyclins D2, E2, A2, and B2 confirmed that synchronized NIH3T3 progressed uniformly through cell cycle after serum supplementation. Using this model, we observed that cells arrested on G1 phase showed a lower number and perinuclear localization of lipid bodies, whereas an increased number of lipid bodies with a homogeneous distribution through the cytoplasm were observed during S phase. These data were confirmed with thymidine synchronization. Moreover, NIH3T3 cells showed increased number and dispersed localization of lipid bodies upon transformation with H-rasV12 oncoprotein.
Conclusions: Taken together, these results suggest that lipid bodies are highly regulated during cell cycle, and also that this regulation is altered in transformed cells. Also, these data provide evidence for a coordinate mechanism that regulates cell cycle progression and lipid body biogenesis, which might be deregulated during cancer development.
Financial Support: CNPq, FAPERJ, CAPES, INCA/FIOCRUZ and INCT-Cancer
Citation Format: André Luiz de Souza Cruz, Patricia Torres Bozza, João Paulo de Biaso Viola. Role of lipid bodies on cell cycle progression. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1744. doi:10.1158/1538-7445.AM2013-1744