Nuclear Mechanics and Nuclear Mechanotransduction in Cancer Cell Migration and Invasion.

Nuclear mechanics and mechanotransduction are involved in the migration and invasion process, such as those in which the cells need to deform themselves to pass through constrictions. Specifically, properties like nuclear softness, viscoelasticity, plasticity (like nuclear pore complexes) and deformability are critical in cancer and its malignant progression. The nucleus represents a physical barrier for the migration and invasion in dense 3D extracellular matrix (ECM) scaffolds. Therefore, the deformability of the nucleus seems to determine the migration limit in circumstances where the enzymatic remodeling of the surroundings is impaired. There are still significant knowledge gaps regarding effects of nuclear deformation during cancer dissemination. It seems that nuclear deformation can alter gene transcription, induce alternative splicing processes, impact nuclear envelope rupture, nuclear pore complex dilatation, damage the DNA, and increase the genomic instability. These mechanically induced alterations can in turn impact the migratory behavior of the cancer cells. The stiffness of the nucleus relies on the condensation of chromatin, and the nuclear lamina, which consists of a network of intermediate filaments underneath the nuclear envelope. All of this is discussed in the review and it is argued that nuclear deformability is universally found in various cancer types. Another focus is placed on the nuclear envelope proteins like emerin, and the SUN-KASH complex and how they contribute to the Linker of Nucleoskeleton and Cytoskeleton (LINC) complex, which consequently couples the nucleus and the cytoskeleton. It is argued that this connection is crucial for force transmission, which governs nuclear stiffness dynamically, depending on the force applied. In this review, recent findings are described that couple ECM-induced nuclear mechanosensing and mechanotransduction with the migration and invasion of cancer cells. Moreover, it is suspected that changes in the mechanosensory characteristics of the cell nucleus could play a pivotal part in the malignancy of cancer cells and the heterogeneity of tumors. Finally, it is discussed what impact the individual elements of the nucleus offer to mechanically alter cellular migration and invasion in cancer and its malignant progression.