Mutation frequencies of SF3B1 (9·7%), NOTCH1 (8·6%), BIRC3 (1·1%), ATM (16·9%) or TP53 (8·1%), and frequencies of cytogenetic abnormalities including trisomy 12 (18·6%), del(17p) (10·4%), del(13q) (43·7%) and IGH translocation (10·1%) were comparable to those reported from Western countries, except del(11q) (6·9%) which was lower in our patients.
Recently, we used this technology to demonstrate that heterozygous mutations of the ATM gene, which is responsible for a hyper-radiosensitive genetic disorder, ataxia-telangiectasia, increased the number of chromosomal aberrations after IR.
To explore the impact of ATM on carcinogenic chromosomal aberrations, we monitored chromosomal breakage at a breakpoint cluster region hotspot within the MLL gene that has been associated with therapy-related leukemia.
Two recurrent cytogenetic aberrations, namely del(17p), affecting TP53, and del(11q), affecting ATM, are associated with resistance against genotoxic chemotherapy (del17p) and poor outcome (del11q and del17p).
Prognostic factors such as chromosome abnormalities (trisomy 12, 11q deletions and 17p deletions), β2 microglobulin, thymidine kinase, CD38 and ZAP-70 expression, IGHV mutation status, and mutations in genes such as NOTCH1, MYD88, SF3B1, and ATM are also predictors of prognosis.
The abrogation of ATR signaling potentiated the cell death response and enhanced chromosomal aberrations after PhIP treatment, while ATM and DNA-PK inhibition had only marginal effects.
A robust response to ODN+IL-15 was positively linked to presence of chromosomal anomalies (trisomy-12 or ataxia telangiectasia mutated anomaly + del13q14) and negatively linked to a very high proportion of CD38(+) cells within the blood-derived B-CLL population.
However, like FXS alleles, FRDA alleles show significantly elevated levels of chromosome abnormalities in the presence of an ATM inhibitor, consistent with the formation of a fragile site.
The authors present here new data on the production of chromosomal aberrations in noncycling low passage human ATM+/+ or ATM+/- cells following irradiations with protons (50 MeV or 1 GeV), 1 GeV(-1) n iron ions and gamma rays, where doses were delivered at a high dose rate of 700 mGy(-1) min, or a lower dose rate of 5 mGy min(-1).
Previously we had shown that the increased chromosome aberrations in ATM and NBS defective lines was due to a significantly larger quadratic dose-response term compared to normal fibroblasts for both simple and complex exchanges.
Every 12 months, a fraction of the irradiated cell population was stimulated to divide by culturing at a low density, and we found that these cells showed increased frequencies of phosphorylated ATM foci, decreased colony-forming ability, and increased frequency of chromosomal aberrations.
We subsequently show that the cellular radiosensitization seen when ATM kinase activity is inhibited for one hour following exposure to gamma-rays, accounts for over 70% of the total cellular radiosensitization seen when ATM kinase activity is inhibited for 17 h. Finally, we show that inhibition of ATM kinase activity for one hour following exposure to irradiation doubles the number of chromosome aberrations occurring in late-S- and G(2)-, but not M-phase, cells.
We found no consistent cytotoxicity or abrogation of ATM kinase activity after IR in seven heterozygous V2424G LCLs, compared to wild-type LCLs, but did find an increase in the number of chromosomal aberrations.
The results obtained with DNA-PK-deficient M059J cells and with DNA-PK-proficient M059K cells treated with wortmannin, an inhibitor of DNA-PK and ATM, suggest that the elimination of DNA-PK-dependent non-homologous end-joining can recruit a slow, error-prone repair process, which is DNA-PK independent and favours the increased formation of chromosome aberrations.
Both ATM and BRCA1 mutations were associated with sensitivity to ionizing radiation, deficient repair of potentially lethal damage and markedly increased chromosomal aberrations.
We conclude that the radioprotective function of the Tel1 protein includes suppression of apoptosis and suppression of chromosome aberrations, and that both cellular end-points can be uncoupled from ionizing radiation-induced cell cycle checkpoints.
We report a case of T-PLL with t(6;11)(q21;q23) as the sole chromosomal abnormality and suggest that the cytogenetically identified translocation also implicates the ATM gene.
The ATM gene deficient in ataxia-telangiectasia, a recessive multisystem disease associated with a high risk of lymphomas and leukemias, was found previously to be inactivated in a rare sporadic malignancy, T-cell prolymphocytic leukemia (T-PLL), which is often associated with cytogenetic aberrations of chromosome 14.
Overexpression of ATM cDNA in A-T cells enhanced the survival of these cells in response to radiation exposure, decreased radiation-induced chromosome aberrations, reduced radio-resistant DNA synthesis, and partially corrected defective cell cycle checkpoints and induction of stress-activated protein kinase.