Abstract

Fanconi Anemia (FA) patients are at increased risk of myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML). Impaired cell cycle regulation may have a role in this predisposition. Over-expression of p53, Ki-67 and survivin proteins has been reported in association with MDS. We analyzed bone marrow samples from 138 individuals: 31 FA, 17 acquired aplastic anemia (AA), 40 sporadic low-grade MDS (MDS-1: 35 refractory cytopenia with multilineage dysplasia [RCMD], 5 RCMD with ring sideroblasts [RCMD-RS]), 11 high-grade MDS (MDS-2: refractory anemia with excess blasts [RAEB]), 12 AML, and 27 normal. To identify cell cycle regulation abnormalities that predict risk of MDS or AML in FA patients, we analyzed bone marrow morphology, cellularity, and immunohistochemical expression of cell cycle regulation proteins: p53 (cycle arrest and apoptosis), Ki-67 (cell proliferation), caspase-3 (apoptosis), and survivin (anti-apoptosis). Protein expression was classified as over-expressed if it was detected in a percentage of cells exceeding the highest values observed in normal marrow. Between group comparisons were made using the Fisher exact test. More FA marrows were hypocellular versus sporadic MDS-1, MDS-2 and AML (p <0.0001 in all). p53 was over-expressed at similar rates in FA, MDS-1, MDS-2 and AML patients (12/25 vs. 22/35, 4/11 and 8/12; p = 0.3, 0.7 and 0.3, respectively); p53 was not over-expressed in AA (0/13, p = 0.003). Ki-67 was also over-expressed at similar rates in FA, MDS-2 and AML patients (9/18 vs. 3/11 and 7/12, p = 0.3 and 0.7), in whom over-expression was higher than in AA or MDS-1 (0/12 and 4/35). Survivin expression was more common in FA than in MDS-1, MDS-2, AML or AA (12/16 vs. 2/32, 0/10, 2/12 or 1/13; p <0.01 for all comparisons). In contrast, the caspase-3 over-expression was higher in MDS-2 than in FA (4/11 vs. 0/18, p = 0.014). 7/31 FA patients had RCMD marrow changes; however, there was no correlation between morphologic features of myelodysplasia and the over-expression of cell cycle markers in these patients. p53 over-expression was frequent in FA, MDS-1, MDS-2, and AML; this distinguishes these disorders from AA. Previous studies found no p53 gene mutations in FA; thus, p53 over-expression observed here may represent upregulation of p53, or diminished p53 protein catabolism. Ki-67 over-expression may be a marker for higher grade MDS. The prevalence of over-expression of survivin was unique to FA, distinguishing it clearly from any of the acquired disorders (AA, MDS or AML), and may be a marker for any inherited bone marrow failure syndrome. Our cell cycle marker results suggest that patients in general in whom there is over-expression of Ki-67 and/or p53 may be at higher risk of evolution to MDS/AML; a longitudinal study is needed to address this prediction.

Disclosure: No relevant conflicts of interest to declare.

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