The central role of 5,10-methylenetetrahydrofolate reductase (MTHFR) and methylenetetrahydrofolate dehydrogenase (MTHFD1) in folate metabolism renders polymorphisms in genes encoding these enzymes potential modulators of therapeutic response to antifolate chemotherapeutics. The analysis of 201 children treated with methotrexate for childhood acute lymphoblastic leukemia (ALL) showed that patients with either the MTHFR T677A1298 haplotype or MTHFD1 A1958 variant had a lower probability of event-free survival (EFS) in univariate analysis (hazard ratio (HR) ¼ 2.2, 95% confidence interval (CI), 1.0-4.7 and 2.8, 95% CI, 1.1-7.3, respectively). Multivariate analysis supported only the role of the MTHFR variant (HR ¼ 2.2, 95% CI, 0.9-5.6). However, the association of both genes with ALL outcome appears to be more obvious in the presence of another event-predisposing variant belonging to the same path of drug action. The combined effect of a thymidylate synthase (TS) triple repeat associated with increased TS levels, with either the MTHFR T677A1298 haplotype or MTHFD1 A1958 allele, resulted in a highly significant reduction of EFS (multivariate HR ¼ 9.0, 95% CI, 1.9-42.8 and 8.9, 95% CI, 1.8-44.6, respectively). These results reveal the role of gene-gene interactions within a folate pathway, and how they can correlate with relapse probabilities in ALL patients.

During tumorigenesis, cancer-related genes can be silenced by aberrant DNA methylation and by changes in chromatin structure. It has been reported that 5-aza-2'-deoxycytidine, a potent inhibitor of DNA methylation, in combination with histone deacetylase inhibitors, can produce a synergistic reactivation of these genes. The aim of our study was to investigate the in vitro antineoplastic activity of 5-aza-2'-deoxycytidine in combination with depsipeptide, a potent histone deacetylase inhibitor, against MDA-MB-231 and MDA-MB-435 human breast carcinoma cell lines. We observed that the combination of 5-aza-2'-deoxycytidine and depsipeptide produced a synergistic antineoplastic effect against these tumor cells as compared to either agent administered alone. We also investigated the effect of this drug combination on the activation of maspin and gelsolin expression. These 2 genes whose function is to suppress tumor metastasis have been reported to be silenced by epigenetic events in breast cancer. Using semi-quantitative RT-PCR, we observed that 5-aza-2'-deoxycytidine in combination with depsipeptide produced a greater reactivation of both maspin and gelsolin as compared to each agent alone. The synergistic interaction between 5-aza-2'-deoxycytidine and depsipeptide on breast carcinoma cell lines provides a rationale to investigate this interesting drug combination in future clinical trials on patients with advanced breast cancer.

No abstract

The results suggest that NOS3 genotyping might identify individuals that are susceptible to intellectual impairment following ALL treatment.

Thymidylate synthase (TS) is an essential enzyme in proliferating cells and an important target for several chemotherapeutics. Several TS gene polymorphisms correlate with variable TS expression: a double (2R) and triple (3R) 28-bp repeat element, a G to C substitution of the 3R allele and a 6 bp variation in 3 0 UTR. We have previously shown that childhood acute lymphoblastic leukemia (ALL) patients who are homozygous for the 3R allele had reduced event-free survival (EFS) probabilities. Here, we analyzed all three polymorphisms in an extended group of ALL patients (n ¼ 259). The effect of the 3R homozygosity on ALL outcome was confirmed (P ¼ 0.006), whereas 6 bp polymorphism did not influence EFS when analyzed separately. No significant difference among 3R3R genotype subgroups, as defined by a G to C substitution, was observed. The haplotype analysis revealed the higher frequency of the 3RC/6 bp þ haplotype (P ¼ 0.04) and the protective role of the 2R/6b pÀ (P ¼ 0.04). Consequently, homozygosity for the 6 bpÀ allele appeared to reduce an event-predisposing effect of 3R variant. Although of importance for translation into the clinical practice, these findings need confirmation in larger studies.

Genes that suppress tumorigenesis can be silenced by epigenetic events, such as aberrant DNA methylation and modification of chromatin structure. Inhibitors of DNA methylase and histone deacetylase (HDAC) can potentially reverse these events. The aim of this study was to determine the in vitro antineoplastic activity of 5-aza-2'-deoxycytidine (5-AZA-CdR), a potent inhibitor of DNA methylase, in combination with depsipeptide (depsi), an inhibitor of HDAC, on human breast carcinoma cells. We observed a synergistic antineoplastic interaction between 5-AZA-CdR and depsi in their capacity to inhibit colony formation of Hs578T and MCF-7 breast carcinoma cells. In order to understand the molecular mechanism of this interaction, we investigated the effect of these drugs on the activation of the 14-3-3sigma, E-cadherin and tissue inhibitor of metalloproteinase 3 (TIMP3) cancer-related genes, which were reported to be silenced by aberrant methylation in many breast tumor cell lines. 14-3-3sigma was reported to produce G cell cycle arrest following DNA damage. E-cadherin and TIMP3 function as suppressors of tumor metastasis. Semi-quantitative RT-PCR was used to determine the effect of the co-administration of 5-AZA-CdR and depsi on four breast carcinoma cell lines for the reactivation of these genes. We observed a synergistic activation of E-cadherin by the combination in Hs578T, MDA-MB-231 and MDA-MB-435 tumor cells. For 14-3-3sigma, we demonstrated an additive to synergistic activation by the combination for Hs578T and MDA-MB-435 tumor cells, respectively. In the MCF-7 tumor cells, the drug combination produced a synergistic activation of TIMP3. The association between the synergistic antineoplastic activity and the synergistic activation of the target genes in this study suggests that the mechanism of anticancer activity of 5-AZA-CdR, in combination with depsi, is probably related to their enhanced activation of different types of tumor suppressor genes that have been silenced by epigenetic events.(2)

No abstract

A reduction in survival probability in children with ALL was associated with homozygosity for G allele of the NR3C1BclI RFLP polymorphism, particularly in certain patient subgroups. Further analysis is required to replicate this finding and to understand the mechanism underlying the observed association.