Background/Objectives:HER2, a critical diagnostic marker and therapeutic target in breast cancer, is a membrane receptor that forms diverse signaling complexes, the constituents of which have not been fully characterized in actual breast cancer tissues.Methods:In this study, we applied the Rapid Immunoprecipitation Mass Spectrometry of Endogenous Proteins (RIME) method, originally developed to explore transcription factor complexes, to identify the complexes formed by HER2 in HER2-positive breast cancer specimens.Results:Through our approach, we successfully identified multiple complex components, including MARCKS, a novel HER2-interacting partner, which we verified using both proximal ligation assay in cultured cells and immunohistochemistry in tissue sections. TCGA analysis further revealed that high MARCKS expression significantly correlates with ER negativity, as confirmed by multivariate analysis, suggesting its potential role as a prognostic indicator in aggressive breast cancer subtypes.Conclusions:These results demonstrate the capability of RIME to elucidate interactomes of membrane proteins such as HER2 in clinical tissue specimens. Furthermore, this study highlights its broader applicability beyond nuclear proteins, underscoring its potential for discovering novel prognostic and diagnostic clinical markers in diverse cancer types.
背景/目的：HER2作为乳腺癌的关键诊断标志物和治疗靶点，是一种膜受体，可形成多种信号复合物，但其在真实乳腺癌组织中的组成成分尚未完全明确。 方法：本研究采用最初为探索转录因子复合物而开发的快速内源性蛋白免疫沉淀质谱技术，对HER2阳性乳腺癌样本中HER2形成的复合物进行鉴定。 结果：通过该方法，我们成功鉴定出多种复合物组分，包括新型HER2相互作用蛋白MARCKS，并通过培养细胞的邻近连接实验和组织切片的免疫组化验证了其相互作用。TCGA分析进一步显示，高MARCKS表达与ER阴性显著相关，经多变量分析证实，提示其可能作为侵袭性乳腺癌亚型的预后指标。 结论：这些结果证明了RIME技术在阐明临床组织样本中膜蛋白（如HER2）相互作用组方面的能力。此外，本研究还凸显了该技术超越核蛋白应用的更广泛适用性，强调了其在多种癌症类型中发现新型预后和诊断临床标志物的潜力。
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