Abstract 3172: Significance of PELP1 signaling in liver cancer progression
Authors: Pratap Uday , Nassar Khaled Mohamed , Yang Xue , Baker Adriana , Gopalam Rahul , Arnold William C. , Adeniran Timilehin , Fernandez Marian Helena Hernandez , Sareddy Gangadhara R. , Viswanadhapalli Suryavathi , Sun Luzhe , Vadlamudi Ratna K. 
Published: March 2024

Abstract
Background: Hepatocellular carcinoma (HCC) is the fastest-rising cause of cancer-related mortality in the United States. Furthermore, advanced HCC has a very poor prognosis, with a median survival time of only about ten months. Effective new targeted therapies are urgently needed for the treatment of HCC. Proline, glutamic acid-, and leucine-rich protein 1 (PELP1) is a protooncogene. PELP1 signaling has been implicated in the development of several cancers, however, its role in the progression of HCC remains unclear. The goal of this project is to investigate the significance and therapeutic potential of targeting PELP1 in HCC.
Methods: In this investigation, we have used six HCC cell lines (HUH7, HEP3B, SNU398, SNU475, SNU423, and SNU449). Using immunohistochemistry (IHC), the expression of PELP1 in HCC tissue microarrays was examined. PELP1shRNA lentiviral particles were used to create PELP1 knockdown (KD) cells. Using well-established in vitro tests for cell proliferation, colony formation, and apoptosis, the effects of PELP1 KD or PELP1 inhibitor (SMIP34) were investigated. RNA-seq, RT-qPCR, Western blotting, IHC, reporter gene assays, and signaling pathway analysis were used in mechanistic investigations. Preclinical evaluations were conducted using mice xenograft models.
Results: TNM plot analysis showed that HCC samples had increased PELP1 expression relative to normal tissue. Immunohistochemistry analysis of tissue microarray confirmed that HCC specimens overexpressed PELP1 in comparison to normal specimens. PELP1 knockdown with shRNA dramatically decreased HCC cell invasion, clonogenicity, and proliferation. Similarly, PELP1 inhibitor SMIP34 treatment significantly reduced cell viability, invasiveness, colony forming capacity, and induced apoptosis of HCC cells. RNA-seq analyses using PELP1 KD cells confirmed that PELP1 modulates the ribosome and the eukaryotic translation elongation pathways. Mechanistic studies confirmed that SMIP34 treatment contributed to the disruption of the Rix complex, which is crucial for ribosomal biogenesis. Puromycin labelling studies confirmed that PELP1 KD or SMIP34 treatment contributes to the reduction of ribosomal biogenesis and new protein synthesis. Furthermore, PELP1 KD or treatment with SMIP34 dramatically slowed the progression of HCC tumors in xenograft models. IHC analysis revealed reduced levels of the proliferation marker Ki67 in PELP1 KD/SMIP34 treated HCC xenograft tumors compared to controls.
Conclusions: Overall, the results of our study point to PELP1 as a potential therapeutic target for HCC intervention.
Citation Format: Uday Pratap, Khaled Mohamed Nassar, Xue Yang, Adriana Baker, Rahul Gopalam, William C. Arnold, Timilehin Adeniran, Marian Helena Hernandez Fernandez, Gangadhara R. Sareddy, Suryavathi Viswanadhapalli, Luzhe Sun, Ratna K. Vadlamudi. Significance of PELP1 signaling in liver cancer progression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3172.