Potential role of CCND1 in neoadjuvant therapy efficacy in esophageal squamous cell carcinoma and its relation to extracellular matrix.

e16136 Background: Radical surgical resection is a component in the treatment strategy for locally advanced esophageal squamous cell carcinoma (ESCC). Immune checkpoint inhibitors (ICIs) have shown substantial efficacy in neoadjuvant therapy, improving tumor downstaging, tumor reduction, pathological remission, and facilitating R0 resection. However, a subset of patients demonstrates suboptimal responses to this treatment, highlighting the need for novel predictive biomarkers and therapeutic targets. Cyclin D1 (CCND1), a positive regulator of cell cycle progression, is overexpressed in various cancers, contributing to tumor progression. However, the role of CCND1 in tumor regression following chemoimmunotherapy in ESCC remains unclear. Methods: A retrospective analysis was performed on locally advanced ESCC patients treated at the Fourth Hospital of Hebei Medical University between January 2022 and January 2024. All patients underwent surgery after receiving neoadjuvant chemotherapy combined with immunotherapy. Biopsy specimens at diagnosis and paraffin-embedded tissue samples from post-surgery were collected. The samples were classified by tumor regression grade (TRG) according to CAP/NCCN criteria: TRG 0 (complete response), TRG 1 (moderate response), TRG 2 (mild response), and TRG 3 (poor response). Transcriptome sequencing and spatial transcriptomics (n = 3/group) were performed to identify key targets and pathways associated with tumor regression. Immunohistochemistry (n = 10/group) and cellular experiments were conducted for validation. Results: Transcriptome sequencing revealed that differentially expressed genes (DEGs) between the groups, such as TRG0 vs. TRG1, TRG1 vs. TRG2, and TRG2 vs. TRG3, were significantly enriched in the "ECM-receptor interaction" pathway. Spatial transcriptomics further confirmed that DEGs in residual tumor regions compared to regressed tumor regions, as well as the regions between good and poor tumor regression, were similarly enriched in the "Extracellular matrix (ECM)-receptor interaction" pathway. Integrative analysis showed a significant upregulation of CCND1 expression with worsening tumor regression. Immunohistochemistry on biopsy specimens at diagnosis revealed a significant correlation between elevated CCND1 expression and poor tumor regression. In vitro experiments using KYSE-30 cells demonstrated that CCND1 knockdown led to a significant reduction in COL1A1, COL1A2, and COL3A1 expression, which encode collagen proteins crucial to ECM. Conclusions: Elevated CCND1 expression is correlated with poor tumor regression after neoadjuvant therapy in locally advanced ESCC. CCND1 may play a pivotal role by modulating the "ECM-receptor interaction" pathway and may serve as a promising biomarker for predicting treatment response and a potential therapeutic target.