Examining the Role of Nup88 and LINC complex in Breast Cancer Metastasis

Abstract

In the last 20 years, it has emerged that Nup88, a cytoplasmic non FG-repeat containing nucleoporin of the nuclear pore complex (NPCs), is over-expressed in a variety of malignant tumours. Several nucleoporins have been previously associated with cancer progression, such as Nup88 binding partners, Nup214 and Nup358/RanBP2. However, Nup88’s association to tumorigenesis is more complex. Nup88 has recently been found at the inner nuclear membrane (INM) associating with lamins, suggesting Nup88 may have additional roles at the nuclear envelope (NE). Overall, the multifaceted nature of Nup88 has sparked research into the role of NPCs and Nup88 in the progression of cancer.

Throughout this project we have extended our knowledge of the contribution NE proteins play in the maintenance of nuclear architecture in a variety of breast cancer cell lines. Through western blotting, immunofluorescence, and immunohistochemical studies, significant changes were observed in the expression of the major NPC and LINC (Linker of Nucleoskeleton and Cytoskeleton) complex components, such as Nesprin-2, SUN proteins, Nup88 and lamin A/C, indicating a deregulation of the bridging complex and its associating partners in breast cancer. As a significant increase in Nup88 was detected in the triple negative breast cancer cell line MDA-MB-231, the primacy of Nup88 in influencing malignant progression via cell cycle deregulation was further examined. Our studies did not indicate a clear relationship between Nup88 overexpression, proliferation, and cancer; therefore, we focused on determining whether Nup88 played a causational or consequential role in the onset of tumorigenesis via potential association to Nesprin-2 (encoded by SYNE2). CRISPR/Cas9 lentiviral activation of SYNE2 in triple negative breast cancer cell lines reduced the levels of Nup88. These changes were accompanied by a rescue of nuclear and cellular architecture. Consequently, we hypothesize decreasing Nup88 levels in triple negative breast cancer cell lines could promote re-integration of Nesprin-2 to the NE. All together, this data suggests Nup88 plays a significant role in tumorigenesis and has the potential to become a future tumour aggressiveness biomarker.