Abstract 4329: Lipid droplets and associated proteins in hepatocellular carcinoma tumour cells

Introduction: Fatty acids are a major source of energy but can be toxic. Cells avoid cytotoxicity by esterifying fatty acids into neutral lipids and packaging them into lipid droplets (LDs). The perilipins (PLINs) are a family of the 5 most abundant LD-associated proteins coating and regulating the LDs¹. Numerous studies have shown links between deregulated lipid metabolism and a wide variety of diseases, including diabetes, obesity, and cancer². Hepatocellular carcinoma (HCC) arising from a background of fatty liver disease accounts for 15%-50% of HCC cases in the United States³. As it has been proposed that an imbalance of lipid composition may disrupt cellular functions and lead to the onset of cancer⁴, and as it was found that deregulated cancer pathways such as the mTOR pathway lead to increased lipogenesis⁵, it is crucial to consider the impact of the expression levels of specific PLINs in the development and progression of HCC.

We hypothesize that understanding the PLIN expression and lipid profile of the tumor and the target organ will allow us to further understand the role of lipid metabolism in HCC. To address this we are manipulating PLIN expression levels in an in vitro system, and using human samples obtained through the Liver Disease Biobank (Dr. Metrakos: IRB approved protocol) to evaluate PLIN function ex vivo.

Preliminary Results:

Knock-down of PLINs - Lentiviral constructs containing shRNA sequences for RNA-interference of PLINs 2, 3, and 5 (which were found to be most highly expressed in HCC⁶) were generated. Knock-Down (KD) lines of PLINs 2 and 3 were successfully created in HepG2. The PLIN 5 KD line has proved difficult to identify due to antibody specificity.

Understanding the role of PLINs - Assessment of cell proliferation in PLIN 2 and 3 KD lines has shown a decrease in growth compared to the Scrambled shRNA control, with no significant difference in proliferation between PLIN 2 and 3 KD lines. When challenged with Oleic Acid, proliferation is further reduced compared to the control line, and PLIN 3 KD cell growth is comparably less than that of PLIN 2 KD cells.

Next steps: Having identified a correlation between PLIN 2 and 3 expression levels and cancer cell proliferation, we are now using the Fluorescent Activated Cell Sorting system to further characterize these cell lines. We are also analyzing human blood and tissue (cancerous and normal) to broaden our understanding of the impact of the PLINs in cancer development and progression. These studies may allow for potential targeting of PLINs in cancer therapy, and as biomarkers for liver disease.

References: (1)Brasaemle, L.(2007) J Lipid Res.48(12):2547-59 (2)Baffy, G. et al.(2012) J. of Hepat.56:1384-91 (3)Sanyal, A. et al.(2010) Curr. Med. Research & Opinion.26(9):2183-2191 (4)Fernandis, A. et al.(2009) J of Chromat.877(26):2830-35 (5)Chakrabarti, P. et al.(2010) Diabetes.59(4):775-781 (6)Straub, B. et al.(2010) Modern. Pathol.23:480-92

Citation Format: Evette Yassa, Hussam Alamri, Tommy Alain, Anthoula Lazaris, Peter Ghali, Nahum Sonenberg, Peter Metrakos. Lipid droplets and associated proteins in hepatocellular carcinoma tumour cells. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4329. doi:10.1158/1538-7445.AM2014-4329