Surfactant proteins A and D (SP-A and SP-D) belong to the collectin subfamily of C-type oligomeric lectins. They are pattern-recognition molecules (PRMs), able to recognise pathogen- or danger-associated molecular patterns (PAMPs, DAMPs) in the presence of Ca2+cations. That property enables opsonisation or agglutination of non-self or altered/abnormal self cells and contributes to their clearance. Like other collectins, SP-A and SP-D are characterised by the presence of four distinct domains: a cysteine-rich domain (at the N-terminus), a collagen-like region, an α-helical neck domain and a globular carbohydrate-recognition domain (CRD) (at the C-terminus). Pulmonary surfactant is a lipoprotein complex, preventing alveolar collapse by reducing surface tension at the air–liquid interface. SP-A and SP-D, produced by type II alveolar epithelial cells and Clara cells, are not only pattern-recognition molecules but also contribute to the surfactant structure and homeostasis. Moreover, they are expressed in a variety of extrapulmonary sites where they are involved in local immunity. The term “cancer” includes a variety of diseases: tumours start from uncontrolled growth of abnormal cells in any tissue which may further spread to other sites of the body. Many cancers are incurable, difficult to diagnose and often fatal. This short review summarises anti- and pro-tumorigenic associations of SP-A and SP-D as well as perspectives of their usefulness in cancer diagnosis and therapy.
表面活性蛋白A和D（SP-A与SP-D）属于C型寡聚凝集素中的胶原凝集素亚家族。作为模式识别分子，它们能在钙离子存在下识别病原体相关分子模式或危险相关分子模式。这一特性使其能够介导非自身或异常自身细胞的调理吞噬或凝集作用，促进其清除。与其他胶原凝集素类似，SP-A和SP-D具有四个特征性结构域：富含半胱氨酸的N端结构域、胶原样区域、α螺旋颈区以及球状碳水化合物识别结构域（位于C端）。肺表面活性物质是一种脂蛋白复合体，通过降低气液界面表面张力防止肺泡塌陷。由II型肺泡上皮细胞和克拉拉细胞产生的SP-A与SP-D不仅是模式识别分子，还参与维持表面活性物质的结构稳定与内环境平衡。此外，它们在多种肺外组织中表达并参与局部免疫应答。"癌症"涵盖多种疾病类型：肿瘤始于任何组织中异常细胞的失控性增殖，并可能进一步扩散至身体其他部位。多数癌症难以治愈、诊断困难且常致命。本综述将系统阐述SP-A和SP-D在促癌与抑癌过程中的双重作用，并探讨其在癌症诊断与治疗中的应用前景。
肿瘤(癌症)患者之家