Mammary serine protease inhibitor (maspin) is a tumor suppressor protein downregulated during carcinogenesis and cancer progression; cytoplasmic-only maspin expression is an independent, unfavorable prognostic indicator in patients with lung squamous cell carcinoma (LUSC). We hypothesized that the cytoplasmic-only localization of maspin has tumor-promoting functions in LUSC. The subcellular localization of maspin and the invasive capability of LUSC cell lines were investigated using RNA sequencing (RNA-seq), Western blotting, and siRNA transfection. Maspin mRNA and protein expression were suppressed in LK-2 and RERF-LC-AI cells. Cell invasion significantly increased in response to siRNA-mediated maspin knockdown in KNS-62 cells expressing both nuclear and cytoplasmic maspin. In LK-2 cells, both nuclear and cytoplasmic maspin were re-expressed, and cell invasion and migration were significantly decreased. In contrast, re-expressed maspin in RERF-LC-AI cells was detected only in the cytoplasm (cytMaspin), and cell invasion and migration were significantly promoted. RNA-seq and downstream analyses revealed that increased cytMaspin expression downregulated the genes associated with cell adhesion and activated PYK2 and SRC, which play important roles in cancer progression. Our study demonstrates a novel biological function of cytMaspin in enhancing the invasive capabilities of LUSC cells. Understanding cytoplasm-to-nuclear maspin translocation dysregulation may develop novel therapeutic approaches to improve the prognosis of patients with LUSC.
乳腺丝氨酸蛋白酶抑制剂（maspin）是一种在癌变和癌症进展过程中表达下调的肿瘤抑制蛋白；仅胞质表达的maspin是肺鳞状细胞癌（LUSC）患者独立的不良预后指标。我们假设maspin的仅胞质定位在LUSC中具有促肿瘤功能。通过RNA测序（RNA-seq）、Western印迹和siRNA转染技术，研究了maspin的亚细胞定位与LUSC细胞系的侵袭能力。在LK-2和RERF-LC-AI细胞中，maspin的mRNA和蛋白表达均受到抑制。在同时表达核质maspin的KNS-62细胞中，siRNA介导的maspin敲低显著增强了细胞侵袭能力。在LK-2细胞中，核质maspin均被重新表达，细胞侵袭和迁移能力显著降低。相反，在RERF-LC-AI细胞中重新表达的maspin仅定位于胞质（cytMaspin），并显著促进了细胞侵袭和迁移。RNA-seq及下游分析显示，cytMaspin表达增加会下调与细胞黏附相关的基因，并激活在癌症进展中起重要作用的PYK2和SRC。本研究揭示了cytMaspin在增强LUSC细胞侵袭能力方面的新生物学功能。理解maspin从胞质向核转位的失调机制，可能为改善LUSC患者预后开发新的治疗策略。
肿瘤(癌症)患者之家