Abstract
Purpose :
Monosomy-3 in the uveal melanoma (UM) cells is associated with the development of fatal metastases particularly in the liver, whereas the gain of chromosome 6p is correlated with a good prognosis. The coexistence of monosomy-3 and 6p gain is a very rare event in the UM cells, the mechanisms of which remain unknown. Interestingly, the spatial organization of chromosomes can be influenced by the nucleoli, which can form a physical barrier in the nucleus, and the nucleolar size tends to increase under hyperglycemia. We therefore analyzed the outcomes of hyperglycemia on the nucleolar organization and chromosome segregation.
Methods :
Cultures of UM cells from the primary tumors of two patients, Tenon fibroblasts from a control patient, and the UM cell lines 92.1 and OMM2.5 were maintained under normoglycemic conditions (with 5.5 mM Glucose). Cells were then incubated in normo- or hyperglycemic medium (25 mM glucose) for 1 day, followed by the exposure to the reversible mitotic inhibitor Nocodazole for 18-24 hours and recovery in fresh medium. Co-detection of proteins with the centromeres of chromosome-3 and -6 was performed by fluorescent Immuno-FISH.
Results :
In the UM cells during interphase, hyperglycemia induced the upregulation of the nucleolar protein Ki67 and the dislocation of a copy of chromosome-3 towards the nuclear center. During prometaphase, the angle between the centromeres of chromosome-3 was reduced under hyperglycemia. During the later mitotic phases, hyperglycemia promoted the missegregation of chromosome-3 and generation of monosomy-3. In contrast, the Tenon fibroblasts featured the reverse pattern, with chromosome-6 being more prone to missegregation under hyperglycemia. Some fibroblasts also exhibited the coexistence of monosomy-3 and chromosome-6 gain in the same daughter cell both under normo- and hyperglycemia.
Conclusions :
Our findings provide the first insight into the crucial influence of hyperglycemia on the chromosome territories in a cell-type dependent manner, which favours the generation of the fatal monosomy-3 over the benign chromosome-6 gain in the UM cells. Prevention of hyperglycemia and excessive glucose release from the liver due to insulin resistance may therefore be a simple and feasible therapeutic approach to maintain the dormancy of the UM cells or their hepatic micrometastases by impeding the generation of monosomy-3.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.