DNMT3A mutations mediate the epigenetic reactivation of the leukemogenic factor MEIS1 in acute myeloid leukemia.

This corrects the article DOI: 10.1038/onc.2015.359.

DNMT3A mutations mediate the epigenetic reactivation of the leukemogenic factor MEIS1 in acute myeloid leukemia.

Close to half of de novo acute myeloid leukemia (AML) cases do not exhibit any cytogenetic aberrations. In this regard, distortion of the DNA methylation setting and the presence of mutations in epigenetic modifier genes can also be molecular drivers of the disease. In recent years, somatic missense mutations of the DNA methyltransferase 3A (DNMT3A) have been reported in ~20% of AML patients; however, no obvious critical downstream gene has been identified that could explain the role of DNMT3A in the natural history of AML. Herein, using whole-genome bisulfite sequencing and DNA methylation microarrays, we have identified a key gene undergoing promoter hypomethylation-associated transcriptional reactivation in DNMT3 mutant patients, the leukemogenic HOX cofactor MEIS1. Our results indicate that, in the absence of mixed lineage leukemia fusions, an alternative pathway for engaging an oncogenic MEIS1-dependent transcriptional program can be mediated by DNMT3A mutations.

Gene amplification-associated overexpression of the RNA editing enzyme ADAR1 enhances human lung tumorigenesis.

The introduction of new therapies against particular genetic mutations in non-small-cell lung cancer is a promising avenue for improving patient survival, but the target population is small. There is a need to discover new potential actionable genetic lesions, to which end, non-conventional cancer pathways, such as RNA editing, are worth exploring. Herein we show that the adenosine-to-inosine editing enzyme ADAR1 undergoes gene amplification in non-small cancer cell lines and primary tumors in association with higher levels of the corresponding mRNA and protein. From a growth and invasion standpoint, the depletion of ADAR1 expression in amplified cells reduces their tumorigenic potential in cell culture and mouse models, whereas its overexpression has the opposite effects. From a functional perspective, ADAR1 overexpression enhances the editing frequencies of target transcripts such as NEIL1 and miR-381. In the clinical setting, patients with early-stage lung cancer, but harboring ADAR1 gene amplification, have poor outcomes. Overall, our results indicate a role for ADAR1 as a lung cancer oncogene undergoing gene amplification-associated activation that affects downstream RNA editing patterns and patient prognosis.

UGT1A and TYMS genetic variants predict toxicity and response of colorectal cancer patients treated with first-line irinotecan and fluorouracil combination therapy.

BACKGROUND: The impact of thymidylate synthase (TYMS) and UDP-glucoronosyltransferase 1A (UGT1A) germline polymorphisms on the outcome of colorectal cancer (CRC) patients treated with irinotecan plus 5-fluorouracil (irinotecan/5FU) is still controversial. Our objective was to define a genetic-based algorithm to select patients to be treated with irinotecan/5FU. METHODS: Genotyping of TYMS (5'TRP and 3'UTR), UGT1A1(*)28, UGT1A9(*)22 and UGT1A7(*)3 was performed in 149 metastatic CRC patients treated with irinotecan/5FU as first-line chemotherapy enrolled in a randomised phase 3 study. Their association with response, toxicity and survival was investigated by univariate and multivariate statistical analysis. RESULTS: TYMS 3TRP/3TRP genotype was the only independent predictor of tumour response (OR=5.87, 95% confidence interval (CI)=1.68-20.45; P=0.005). UGT1A1(*)28/(*)28 was predictive for haematologic toxicity (OR=6.27, 95% CI=1.09-36.12; P=0.04), specifically for neutropenia alone (OR=6.40, 95% CI=1.11-37.03; P=0.038) or together with diarrhoea (OR=18.87, 95% CI=2.14-166.67; P=0.008). UGT1A9(*)1/(*)1 was associated with non-haematologic toxicity (OR=2.70, 95% CI=1.07-6.82; P=0.035). Haplotype VII (all non-favourable alleles) was associated with non-haematologic toxicity (OR=2.11, 95% CI=1.12-3.98; P=0.02). CONCLUSION: TYMS and UGT1A polymorphisms influence on tumour response and toxicities derived from irinotecan/5FU treatment in CRC patients. A genetic-based algorithm to optimise treatment individualisation is proposed.

Expression analysis of genes involved in oxaliplatin response and development of oxaliplatin-resistant HT29 colon cancer cells.

The interrelationship between platinum resistance and clinical response is not well established. The purpose of this study is to evaluate the expression of 14 genes involved in platinum resistance in a colon cancer cell line (HT29) and its oxaliplatin (OXA)-resistant sublines. Resistant cells exhibited lower expression of many of these genes suggesting that several pathways may be implicated in OXA resistance. Particularly, OXA resistance is accompanied by defects in drug uptake (downregulation of the hCTR1 transporter) and enhanced DNA repair (upregulation of the XPD gene). Our data also confirmed that copper transporters and chaperones are involved in OXA resistance in colorectal cancer cells as evidenced by the overexpression of ATP7A and CCS in response to OXA exposure. Moreover, increased CCS expression suggests a role for SOD1 in OXA detoxification. Whereas exposure to OXA in HT29 induced significant changes in expression of many of the genes analyzed, only ATP7A, XPD and SRPK1 gene expression was increased in OXA-treated HTOXAR3 resistant cells. To our knowledge, this is the first report of implicating SRPK1 in OXA resistance. This study provides the basis for further evaluation of these putative markers of OXA response and resistance in colorectal cancer patients who are candidates for treatment with OXA.