Department of Biomedical Engineering, Virginia Commonwealth University, 410 West Main St., Richmond, VA 23284, USA.
Department of Biomedical Engineering, Virginia Commonwealth University, 410 West Main St., Richmond, VA 23284, USA.
Int J Biochem Cell Biol. 2023 Dec;165:106478. doi: 10.1016/j.biocel.2023.106478. Epub 2023 Oct 21.
Remodeling of the extracellular matrix (ECM) is a key hallmark of cancer progression. A critical component of ECM remodeling is the assembly of the glycoprotein fibronectin (FN) into insoluble fibrils, which provide a scaffold for invading vascular endothelial cells and escaping cancer cells, as well as a framework for collagen deposition and oncogenic cytokine tethering. FN fibril assembly is induced by Transforming Growth Factor-β1 (TGF-β1), which was originally identified for its role in malignant transformation. Addition of exogenous TGF-β1 drives FN fibril assembly while also upregulating endogenous TGF-β1 expression and autocrine signaling. In the current study, we sought to determine if autocrine TGF-β1 signaling plays a role in FN fibril formation in either MCF10A mammary epithelial cells, which behave similarly to healthy epithelia, or malignant MDA- MB-231 breast cancer cells. Our results show two interesting findings: first, malignant MDA-MB- 231 cells assemble less FN into fibrils, despite expressing and secreting more soluble FN; second, autocrine TGF-β1 signaling is required for FN fibril formation in MCF10A epithelial cells, even in the presence of exogenous, active TGF-β1. This suggests that autocrine TGF-β1 is signaling through distinct pathways from active exogenous TGF-β1. We hypothesized that this signaling was mediated by interactions between the TGF-β1 latency associated peptide (LAP) and α integrins; indeed, incubating MCF10As with soluble LAP, even in the absence of the active TGF-β1 ligand, partially recovered FN fibril assembly. Taken together, these data suggests that autocrine TGF-β1 plays a critical role in FN fibril assembly, and this interaction is mediated by LAP-integrin signaling.
细胞外基质（ECM）的重塑是癌症进展的一个关键标志。ECM 重塑的一个关键组成部分是糖蛋白纤连蛋白（FN）组装成不溶性原纤维，为侵袭性血管内皮细胞和癌细胞逃逸提供支架，以及胶原蛋白沉积和致癌细胞因子固定的框架。FN 原纤维组装由转化生长因子-β1（TGF-β1）诱导，TGF-β1 最初因其在恶性转化中的作用而被鉴定。添加外源性 TGF-β1 可驱动 FN 原纤维组装，同时上调内源性 TGF-β1 表达和自分泌信号。在本研究中，我们试图确定自分泌 TGF-β1 信号是否在 MCF10A 乳腺上皮细胞（其行为类似于健康上皮细胞）或恶性 MDA-MB-231 乳腺癌细胞中 FN 原纤维形成中发挥作用。我们的结果显示了两个有趣的发现：首先，尽管恶性 MDA-MB-231 细胞表达和分泌更多可溶性 FN，但它们组装成的 FN 原纤维较少；其次，自分泌 TGF-β1 信号对于 MCF10A 上皮细胞中的 FN 原纤维形成是必需的，即使存在外源性、活性 TGF-β1 也是如此。这表明自分泌 TGF-β1 通过与活性外源性 TGF-β1 不同的途径发出信号。我们假设这种信号是通过 TGF-β1 潜伏相关肽（LAP）和α整联蛋白之间的相互作用介导的；事实上，即使在没有活性 TGF-β1 配体的情况下，用可溶性 LAP 孵育 MCF10A，也部分恢复了 FN 原纤维组装。总之，这些数据表明自分泌 TGF-β1 在 FN 原纤维组装中起关键作用，这种相互作用是由 LAP-整联蛋白信号介导的。
