Division of Oncology and Therapeutic Pathology, Department of Clinical Sciences, Lund University, Lund, Sweden.
UCD School of Biomolecular and Biomedical Sciences, UCD Conway Institute, University College Dublin, Belfield, Dublin, Ireland.
BMC Cancer. 2022 Feb 2;22(1):131. doi: 10.1186/s12885-021-09168-7.
The response to neoadjuvant cisplatin-based chemotherapy (NAC) in muscle-invasive bladder cancer (MIBC) is impaired in up to 50% of patients due to chemoresistance, with no predictive biomarkers in clinical use. The proto-oncogene RNA-binding motif protein 3 (RBM3) has emerged as a putative modulator of chemotherapy response in several solid tumours but has a hitherto unrecognized role in MIBC.
RBM3 protein expression level in tumour cells was assessed via immunohistochemistry in paired transurethral resection of the bladder (TURB) specimens, cystectomy specimens and lymph node metastases from a consecutive cohort of 145 patients, 65 of whom were treated with NAC. Kaplan-Meier and Cox regression analyses were applied to estimate the impact of RBM3 expression on time to recurrence (TTR), cancer-specific survival (CSS), and overall survival (OS) in strata according to NAC treatment. The effect of siRNA-mediated silencing of RBM3 on chemosensitivity was examined in RT4 and T24 human bladder carcinoma cells in vitro. Cellular functions of RBM3 were assessed using RNA-sequencing and gene ontology analysis, followed by investigation of cell cycle distribution using flow cytometry.
RBM3 protein expression was significantly higher in TURB compared to cystectomy specimens but showed consistency between primary tumours and lymph node metastases. Patients with high-tumour specific RBM3 expression treated with NAC had a significantly reduced risk of recurrence and a prolonged CSS and OS compared to NAC-untreated patients. In high-grade T24 carcinoma cells, which expressed higher RBM3 mRNA levels compared to RT4 cells, RBM3 silencing conferred a decreased sensitivity to cisplatin and gemcitabine. Transcriptomic analysis revealed potential involvement of RBM3 in facilitating cell cycle progression, in particular G/S-phase transition, and initiation of DNA replication. Furthermore, siRBM3-transfected T24 cells displayed an accumulation of cells residing in the G-phase as well as altered levels of recognised regulators of G-phase progression, including Cyclin D1/CDK4 and CDK2.
The presented data highlight the potential value of RBM3 as a predictive biomarker of chemotherapy response in MIBC, which could, if prospectively validated, improve treatment stratification of patients with this aggressive disease.
新辅助顺铂化疗（NAC）在多达 50%的肌层浸润性膀胱癌（MIBC）患者中的反应受损，这是由于化疗耐药，目前临床上没有预测生物标志物。原癌基因 RNA 结合基序蛋白 3（RBM3）已成为几种实体肿瘤中化疗反应的潜在调节剂，但在 MIBC 中尚未得到认可。
通过免疫组织化学检测 145 例连续患者的经尿道膀胱肿瘤切除术（TURB）标本、膀胱切除术标本和淋巴结转移标本中的肿瘤细胞中 RBM3 蛋白表达水平，其中 65 例接受 NAC 治疗。应用 Kaplan-Meier 和 Cox 回归分析估计 RBM3 表达对 NAC 治疗分层患者的无复发生存时间（TTR）、癌症特异性生存（CSS）和总生存（OS）的影响。在体外，使用 siRNA 介导的 RBM3 沉默来检测顺铂和吉西他滨的化疗敏感性。使用 RNA 测序和基因本体分析评估 RBM3 的细胞功能，然后使用流式细胞术研究细胞周期分布。
RBM3 蛋白在 TURB 中表达明显高于膀胱切除术标本，但在原发肿瘤和淋巴结转移中具有一致性。接受 NAC 治疗的高肿瘤特异性 RBM3 表达患者与未接受 NAC 治疗的患者相比，复发风险显著降低，CSS 和 OS 延长。与 RT4 细胞相比，高等级 T24 癌细胞中 RBM3 mRNA 水平表达更高，RBM3 沉默导致对顺铂和吉西他滨的敏感性降低。转录组分析表明 RBM3 可能参与促进细胞周期进程，特别是 G1/S 期转换和 DNA 复制的启动。此外，siRBM3 转染的 T24 细胞显示出 G 期细胞的积累以及公认的 G 期进展调节剂的水平改变，包括细胞周期蛋白 D1/CDK4 和 CDK2。
本研究数据强调了 RBM3 作为 MIBC 化疗反应预测生物标志物的潜在价值，如果前瞻性验证，可能会改善这种侵袭性疾病患者的治疗分层。
