Mechanoresponsive patterns of KLF2, 4, 5, and 6 expression differ among subclones from a single mammary tumor

Abstract

A number of Krüppel-like transcription factor (KLF) family members display mechanoresponsive behaviors, and function as mechanosensitive transcription factors. There are many normal and pathological conditions where their roles in mechanotransduction and mechanoadaptation are not well understood, however. In this study, two basic questions regarding KLF mechanoresponsiveness were addressed: 1) are KLF 2, 4, 5, and 6 expressed at different levels among subclones of tumor cells adapted to specific microenvironmental conditions; and 2) is the expression of these KLFs responsive to rapid changes in the physical environment? To address these questions, the heterogeneous and differentially metastatic murine mammary tumor subclones 4T1, 4T07, and 67NR were subjected to physical changes in their culture conditions, and KLF responses assessed. The results show that the expression of different KLFs exhibit distinct responses to reductions in cell tension, as well as cell detachment from 2D and 3D environments. KLF2 and 4 expression is rapidly and temporarily induced upon release of cells from a stiff 2D substrate into liquid suspension culture in all three subclones, and similar responses are observed in two of the subclones upon the release of tension in 3D collagen gel cultures. By contrast, expression patterns of KLF5 and 6 were generally less affected by physical changes in most, but not all, of the cell lines examined. These results support the concept that KLFs differentially participate in transducing physical differences among intratumoral neighborhoods into distinct responses among heterogeneous subclones, thereby contributing to tumor cell behavioral complexity.