EBF1 Deficiency Drives Prostate Cancer Progression by Interfering with the Transcriptional Regulation of ITPR1

Early B-cell factor 1 (EBF1), originally identified as a critical transcription factor modulating the development and differentiation of B lymphocytes, has recently attracted significant interest owing to its diverse functional characteristics and regulatory mechanisms in solid tumors. Although current evidence suggests a potential connection between EBF1 and oncogenic developments, its exact role in the progression of prostate cancer (PCa) is unclear. This study sought to investigate its biological roles and regulatory mechanisms in human PCa.

Bioinformatic analyses were performed utilizing Tumor Immune Estimation Resource (TIMER) 2.0, Gene Expression Profiling Interactive Analysis (GEPIA), and Gene Expression Omnibus (GEO) databases, along with quantitative polymerase chain reaction (qPCR) assays and immunostaining on clinically available PCa and normal prostate tissues, to investigate the expression profile and clinical significance of EBF1. The manipulation of EBF1 expression through lentivirus was conducted to explore the impact of both knockdown and overexpression of EBF1 on the malignant behaviors of PCa cells in vitro, as well as in a xenograft mouse model. Ultimately, various molecular biomedical techniques were employed to clarify the possible transcriptional regulation of inositol 1,4,5-trisphosphate receptor type 1 (ITPR1) by EBF1.

Bioinformatic analyses revealed that reduced EBF1 expression exhibited a robust prognostic association with PCa progression. From a functional standpoint, knockdown of EBF1 promoted cell proliferation (n = 3, *p < 0.05, ***p < 0.001 for LNCaP-48 h and LNCaP-72 h; *p < 0.05, ****p < 0.0001 for 22RV1-48 h and 22RV1-72 h respectively), colony formation (n = 3, ***p < 0.001 for LNCaP and **p < 0.01 for 22RV1), migration (n = 3, ***p < 0.001 for LNCaP and ***p < 0.001 for 22RV1) and invasion (n = 5, ****p < 0.0001 for LNCaP and ****p < 0.0001 for 22RV1) capabilities in LNCaP and 22RV1 cells, while ectopic overexpression of EBF1 in PC-3 cells significantly inhibited tumor growth (n = 5, *p < 0.05 at d 36 after cell inoculation) and invasiveness (n = 5, **p < 0.01 for E-cadherin and Vimentin H-scores, respectively) in vivo. Mechanistically, EBF1 depletion was associated with a reduced expression of ITPR1, a key player in intracellular calcium release and a fundamental tumor suppressor in multiple cancers. Furthermore, using chromatin immunoprecipitation (ChIP), electrophoretic mobility shift (EMSA) and luciferase reporter assays, we demonstrated that EBF1 could directly bind to the distal region of the ITPR1 promoter (n = 3, **p < 0.01 for ChIP-qPCR), thereafter facilitating its transcriptional expression (n = 3, ****p < 0.0001 for reporter assays). Importantly, overexpression of exogenous ITPR1 effectively ameliorated EBF1 deficiency-induced tumorigenicity in both LNCaP and 22RV1 cells.

These findings together indicate a new function of EBF1 loss in enhancing PCa progression, highlight ITPR1 as a key downstream effector in facilitating the tumor-suppressing function of EBF1, and provide significant insights into improving our understanding of the transcriptional regulation of malignant behaviors in PCa cells.