Abstract 1598: Involvement of atypical PKCs in liver cancer

Abstract The liver is an essential organ in the human body, it carries out important biological functions including detoxification, nutrient metabolism, protein synthesis, production of bile and other biochemical reactions necessary for growth. Liver cancer is a disease in which cancer cells form in the tissues of the liver. The death rate for liver cancer was 6.6 per 100, 000 men and women per year. HepaRG is an immortalized hepatic cell line that retains many characteristics of primary human hepatocytes while HEPG2 and PLC5/PRF/5 are liver cancer cell lines isolated from liver cancer donors. Atypical Protein Kinase C (aPKC) is a type of protein kinase that does not require Ca2+ or diacylglycerol for their activation, aPKC consists of two isoforms: PKCiota (PKC-ι) and PKCzeta (PKC-ζ). We have previously reported the dose dependent response of HEPG2 and PLC5/PRF/5 cell line to treatment with 5-amino-1-(1R, 2S, 3S, 4R)-2, 3-dihydroxy-4-methylcyclopentyl)-1H-imidazole-4-carboxamide (ICA-1S). However, there is no clear understanding of which intracellular chemicals are involved in liver cancer progression and what the involvement of aPKCs is in liver cancer. In this study, we investigated the status and function of aPKC in proliferating and confluent liver cells, our objective was to determine if the expression of PKC-ι and PKC-ζ are altered in liver cancer cells compared to normal liver cells. HepaRG, HEPG2, and PLC5/PRF/5 cells were seeded in 100mm plates and maintained with fresh media. Samples from each cell line were collected in lyses buffer at 50% and approximately 100% confluence. The protein concentration of the prepared samples was quantified with Bradford, Laemmli buffer was added, samples were heated, and Western blot analyses were carried out with equal amounts of protein. Samples were probed for PKC-ι, PKC-ζ, and Caspase3. There was a 32% downregulation of PKC-ι in the HepaRG cell line and a 37% and 9% upregulation were observed in HEPG2 and PLC5/PRF/5 respectively for the expression of PKC-ι as the liver cancer cells gain confluency (N = 3). The results for the expression of PKC-ζ showed a 26% downregulation in HepaRG but a notable 61% upregulation in HEPG2 and a slight 12% upregulation in PLC5/PRF/5 at 100% confluence (N = 3). The unchanged caspase 3 expression confirms that the difference in the expression level of the aPKC is not due to apoptosis. Results demonstrated a relationship between cell confluence and aPKCs protein levels depicting that PKC-ι along with PKC-ζ, play a different role in proliferation of the normal liver cells compared to liver cancer cells. Our ongoing investigation on the effect of aPKCs through the knockdown of PKC-ι resulted in about 30% reduction of HEPG2 proliferation Citation Format: Abigail Oluwafisayo Olatunji, Mahfuza Marzan, Nuzhat Nowshin Oishee, Mildred Acevedo-Duncan. Involvement of atypical PKCs in liver cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 1598.