Abstract 4041: Overexpression of HMGA1 in gastric cancer cells is associated with reduced tumor cell malignant behavior and decreased YAP-TEAD signaling

Background: The High Mobility Group A1 (HMGA1) is an architectural transcription factor and facilitates the interaction between transcriptional regulatory proteins and DNA in different cancers by remodeling chromatin structure. Hippo/YAP1 pathway is an evolutionary conserved signaling consisting of up-stream kinases, transcriptional co-activators and scaffold proteins. Unphosphorylated YAP and TAZ translocate to the nucleus, bind with TEAD transcription factor family and induce expression of a wide range of genes involved in cell malignant behavior. Silencing of HMGA1 downregulated YAP activity in breast cancer however, the functional role of HMGA1 and its interaction with Hippo/YAP1 signaling in mediating gastric cancer (GC) progression and metastasis remains unknown. We hypothesize that HMGA1 is essential to promote YAP activity in gastric cancer. Methods: TCGA dataset and our own bulk RNAseq and single cell RNA sequencing (scRNAseq) will be analyzed to understand the expression pattern of HMGA1 in normal, primary tumors and metastatic tissues. HMGA1 will be overexpressed in GC cells; and YAP activity will be measured by its nuclear translocation, transcription of target genes (CTGF, CyR61, Birc5, Sox9) upon genetic modulation of HMGA1. In vitro functional assays such as proliferation, migration, colony formation and tumor sphere as well as in vivo tumorigenicity of GC cells with HMGA1 overexpression will be performed in SCID mice. Results: HMGA1 expression was significantly increased in GC tissues compared to normal in TCGA datasets. Moreover, HMGA1 transcripts showed positive correlation with YAP1 and TEAD4 mRNA level. scRNAseq data from advanced GC patients indicated HMGA1 mRNA is upregulated in primary tumor, peritoneal and liver metastasis compared to normal in stomach. Tissue microarray of more than 200 GC indicated that HMGA1 is highly expressed in tumor tissue and associated with poor survival. Increased expression of HMGA1 was detected in cancer cells as compared to normal gastric epithelial cells by Western blot. Unexpectedly, overexpression of HMGA1 in GC cell lines (AGS, GA0518 and GT-5) reduced colony formation, and tumor-sphere size and number as compared to vector control. Invasion of AGS, GA0518 and GT-5 was significantly reduced upon HMGA1 overexpression. Mechanistically, nuclear localization of YAP, TAZ and SOX9 (YAP target) was decreased while Tead1-4 did not change in GC cells upon overexpressing HMGA1 compared to vector. Furthermore, YAP-TEAD luciferase reporter activity was significantly reduced along with transcript level of YAP target genes upon HMGA1 overexpression vs. vector in GC cells. Conclusion: Although, endogenous expression of HMGA1 was increased in GC cells and tissues as compared to normal, its overexpression reduced tumor cell malignant behavior, migration and inhibited YAP-TEAD signaling. Citation Format: Dipti Athavale, Yan-ting Yann Zhang, Xiaodan Yao, Shumei Song. Overexpression of HMGA1 in gastric cancer cells is associated with reduced tumor cell malignant behavior and decreased YAP-TEAD signaling [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 4041.