Nuclear envelope protein LBR protects the genome from chromosomal instability and tumorigenesis.

Lamin B Receptor (LBR) is an inner nuclear membrane protein that assembles the nuclear envelope post mitosis. Here we show that LBR depletion induces mitotic defects accompanied by recurrent chromosomal losses. In addition, LBR knockdown results in nuclear aberrations such as nuclear blebs and micronuclei, with chromosomes showing a higher frequency of losses, being enriched within the micronucleus. Furthermore, doxycycline-induced conditional depletion of LBR significantly increased tumor volumes that form within the subcutaneous xenografts of mice. Of note, the tumor-derived primary cells recapitulated chromosomal losses and gains, revealing a novel role for LBR as a tumor suppressor. Co-immunoprecipitation (Co-IP) of LBR uncovered an association of LBR with telomere-associated factors. Interestingly, qPCR array-based gene expression profiling showed a significant upregulation of TRF1 upon LBR depletion. Remarkably, TRF1 knockdown in the background of LBR depletion maintains chromosomal stability, unraveling a novel mechanism involving LBR and TRF in the maintenance of chromosomal stability in colorectal cancer cells.