Atypically low spontaneous sister chromatid exchange formation in uveal melanoma

Abstract

Uveal melanoma (UM) is the most common primary intraocular cancer of adults and is characterized by several well-established chromosomal changes. More recently, a specific mutation of guanine nucleotide binding protein Gq alpha subunit (GNAQ) has also been identified in a proportion of UM. Although some of these alterations have been suggested to be early changes, the genetic alterations responsible for the development of UM have yet to be clearly determined. Cancers are characterized by increased genetic instability, and analysis of established cancer cell lines and blood from cancer patients has universally been associated with an increased level of sister chromatid exchange (SCE). We have observed that the spontaneous frequency of SCE in primary cultures of UM and UM-derived cell lines is decreased below normal baseline levels, a phenomenon unique to UM when compared with multiple other cancers. This finding was specific to the tumor and not found in lymphocytes from the patients. Although we cannot exclude the possibility that low SCE (LSCE) is peculiar to the uveal melanocytes lineage, as it was consistently observed in all UM studied, regardless of other genetic defects, we propose that this phenomenon contributes to the molecular pathogenesis of UM.

Reduced FANCD2 influences spontaneous SCE and RAD51 foci formation in uveal melanoma and Fanconi anaemia

“…16 Here we demonstrate that complementation of UM cells with FANCD2 increases SCE. In addition, deficiency in FANCD2 also reduced spontaneous SCE in other human cell lines including the FA patient-derived cell line PD20.…”

“…SCEs in FANCD2-complemented SOM196b were not significantly different to the level seen in cutaneous melanoma and other control cells (data not shown). 16 This suggests that FANCD2 expression is influencing previously reported SCE formation in UM.…”

“…Previously, we reported that both primary and established UM cell lines have reduced SCE compared with a panel of normal and cancer cell types, 16 suggesting that endogenous DNA damage is handled differently in UM. Here SCE (Figure 3d) increased when SOM196b was complemented with FANCD2 (Student's t -test P <0.001 and P <0.01 for 196bD2 compared with SOM196b and 196b-pMMP, respectively).…”

Altered Expression of the Poly(ADP-Ribosyl)ation Enzymes in Uveal Melanoma and Regulation ofPARGGene Expression by the Transcription Factor ERM

“…48 Interestingly, PARG 110 À/À mice have greatly increased numbers of hepatocellular carcinomas following treatment with diethylnitrosamine (DEN). Because it already was reported that spontaneous sister chromatid exchange (SCE) in UM cell lineages are very low, 49 it would be unlikely that it is a cause of increased tumorigenicity in T97 and T115 cells deficient in the expression of PARG 110 . More analyses are needed to sort out this possibility.…”

Effects of prolonged exposure to low dose metformin in thyroid cancer cell lines

“…To investigate this, the H2AX assay ( H2A.X protein gamma-H2A.X) was used to measure DNA Double Strand Breaks (DNA-DSBs), as phosphorylation of H2A.X is an effective measure of DSBs 35, and was performed as previously reported 36. For each cell line, cells were seeded (2x 10 4 cells per slide) into 6 well plates and after 24 hours, the wells corresponding to each cell line were divided in groups and subject to different combinations of treatments:…”