The role of genotypes that modify the toxicity of chemical mutagens in the risk for myeloproliferative neoplasms

Genic-intergenic polymorphisms of CYP1A genes and their clinical impact

The humancytochrome P450 1A (CYP1A) subfamily genes, CYP1A1 and CYP1A2, encoding monooxygenases are critically involved in biotransformation of key endogenous substrates (estradiol, arachidonic acid, cholesterol) and exogenous compounds (smoke constituents, carcinogens, caffeine, therapeutic drugs). This suggests their significant involvement in multiple biological pathways with a primary role of maintaining endogenous homeostasis and xenobiotic detoxification. Large interindividual variability exist in CYP1A gene expression and/or catalytic activity of the enzyme, which is primarily due to the existence of polymorphic alleles which encode them. These polymorphisms (mainly single nucleotide polymorphisms, SNPs) have been extensively studied as susceptibility factors in a spectrum of clinical phenotypes. An in-depth understanding of the effects of polymorphic CYP1A genes on the differential metabolic activity and the resulting biological pathways is needed to explain the clinical implications of CYP1A polymorphisms. The present review is intended to provide an integrated understanding of CYP1A metabolic activity with unique substrate specificity and their involvement in physiological and pathophysiological roles. The article further emphasizes on the impact of widely studied CYP1A1 and CYP1A2 SNPs and their complex interaction with non-genetic factors like smoking and caffeine intake on multiple clinical phenotypes. Finally, we attempted to discuss the alterations in metabolism/physiology concerning the polymorphic CYP1A genes, which may underlie the reported clinical associations. This knowledge may provide insights into the disease pathogenesis, risk stratification, response to therapy and potential drug targets for individuals with certain CYP1A genotypes.

Extramedullary Hematopoiesis of the Liver and Spleen

Hematopoiesis is the formation of blood cellular components and, consequently, immune cells. In a more complete definition, this process refers to the formation, growth, maturation, and specialization of blood cells, from the hematopoietic stem cell, through the hematopoietic progenitor cells, to the s pecialized blood cells. This process is tightly regulated by several elements of the bone marrow microenvironment, such as growth factors, transcription factors, and cytokines. During embryonic and fetal development, hematopoiesis takes place in different organs: the yolk sac, the aorta–gonad mesonephros region, the lymph nodes, and not lastly, the fetal liver and the spleen. In the current review, we describe extramedullary hematopoiesis of the spleen and liver, with an emphasis on myeloproliferative conditions.

Environmental Factors, Lifestyle Risk Factors, and Host Characteristics Associated With Philadelphia Negative Myeloproliferative Neoplasm: A Systematic Review

Myeloproliferative neoplasms (MPNs) are clonal hematopoietic stem cell disorders characterized by the overproduction of mature myeloid cells and are often associated with an acquired genetic mutation of Janus Kinase2V617F. Various epidemiological studies have indicated associations between environmental factors, lifestyle factors, and host characteristics with developing MPNs. This review aims to collect and summarize the existing information on these risk factors and establish their association with pathogenesis MPNs. Medline, Embase, PubMed, and grey literature were systematically searched using key terms for MPNs, and epidemiological study designs, that is, cross-sectional studies, case-control, and cohort, that investigated the risk factors for MPNs published were identified. Out of the 4621 articles identified, 20 met the selection criteria and were included in this review. Heterogeneity, study reliability, and bias were assessed. A significant association was found between smoking and the development of MPNs. This relationship has been explained by the substantial increase in several proinflammatory mediators and systematic oxidative stress causing hyperstimulation of myeloid compartments leading to the development of MPNs. Obesity was modestly linked with an increased risk of MPNs. The underlying mechanisms have been linked to changes in endocrine, metabolic, and inflammatory systems. No strong association was found between exposure to hazardous substances, that is, benzene and MPNs, but further investigation on the effects of increased levels and duration of exposure on hematopoietic stem cells will be beneficial. Unique individual and host variations have been determined as a modifier of disease pathogenesis and phenotype variations. There is a higher incidence rate of females developing MPNs, specifically ET, than males with higher PV incidence. Therefore, gender contributes to the heterogeneity in myeloproliferative neoplasm. Studies identified as part of this review are very diverse. Thus, further in-depth assessment to explore the role of these etiological factors associated with MPNs is warranted.

The impact of CYP2D6*4 and GSTP1 Ile105Val polymorphisms on the susceptibility to develop BCR-ABL1 negative myeloproliferative neoplasms

Inter-individual variations in the genes encoding xenobiotic-metabolizing enzymes have been reported to alter susceptibility to various diseases involving hematological disorders. The purpose of this case-control study was to investigate the relationship between CYP2D6*4 and GSTP1 Ile105Val polymorphisms and the risk of developing BCR-ABL1 negative myeloproliferative neoplasms (MPN). PCR-RFLP was used for genotyping single nucleotide polymorphisms (SNP) in CYP2D6 and GSTP1 in 139 patients with MPN and 126 controls. There was a significantly increased risk for developing BCR-ABL1 negative MPN for the group bearing the CYP2D6*4 variant allele (X²: 4.487; OR 1.738; 95% CI 1.040-2.904; p = 0.034). The platelet count was higher in CYP2D6*4 allele carriers (p = 0.047). There was no association between the GSTP1 Ile105Val polymorphism and the risk of developing MPNs. MPN patients bearing the GSTP1 Ile105Val variant allele had a higher prevalence of bleeding complications (X²: 7.510; OR 4.635; 95% CI 1.466-14.650; p = 0.006). Our study provides new data that the CYP2D6*4 polymorphism may be associated with an increased risk to develop MPNs while the GSTP1 Ile105Val polymorphism does not show such an association. To our knowledge, the current study is the first to investigate the relationship between CYP2D6*4 and GSTP1 Ile105Val polymorphisms and the risk of developing MPNs in the Turkish population. Further studies with more patients and controls are needed to support our data.

Modifiable Lifestyle and Medical Risk Factors Associated With Myeloproliferative Neoplasms

Despite the identification of acquired genetic mutations associated with Myeloproliferative Neoplasms (MPNs) there is a paucity of information relating to modifiable risk factors that may lead to these mutations. The MOSAICC Study was an exploratory case-control study of polycythemia vera (PV), essential thrombocythemia (ET), and Myelofibrosis (MF). MPN patients and population controls (identified by General Practitioners) and non-blood relative/friend controls were recruited from 2 large UK centers. Participants completed a telephone-based questionnaire analyzed by unconditional logistic regression analysis adjusting for potential confounders. Risk factors for MPNs identified included increasing childhood household density [odds ratio (OR) 2.55, 95% confidence interval (CI) 1.16–5.62], low childhood socioeconomic status (OR 2.30, 95%CI 1.02–5.18) and high pack years smoking (OR 2.19, 95%CI 1.03–4.66) and current smoking restricted to JAK2 positive PV cases (OR 3.73, 95%CI 1.06–13.15). Obesity was linked with ET (OR 2.59, 95%CI 1.02–6.58) confirming results in previous cohort studies. Receipt of multiple CT scans was associated with a strongly increased risk of MPN although with wide confidence intervals (OR 5.38, 95%CI 1.67–17.3). Alcohol intake was inversely associated with risk of PV (OR 0.41, 95%CI 0.19–0.92) and ET (OR 0.48, 95%CI 0.24–0.98). The associations with childhood household density, high pack years smoking and alcohol were also seen in multivariate analysis. This is the largest case control study in MPNs to date and confirms the previously reported associations with obesity and cigarette smoking from cohort studies in addition to novel associations. In particular, the role of smoking and JAK2 mutation cases merits further evaluation.

Gene Polymorphism of Xenobiotic Biotransformation Enzymes in Patients with Classical Ph-Negative Myeloproliferative Neoplasms

The correlation of gene polymorphisms rs4025935 (large deletion), rs1695 (313A>G), rs71748309 (large deletion), and rs1800566 (609C>T) of GSTM1, GSTT1, and NQO1 genes encoding glutathione-S-transferases (GST) M1, P1, and T1 and NADPH-quinone oxidoreductase with the risk of development of classical Ph-negative myeloproliferative neoplasms (polycythemia vera, essential thrombocythemia, and primary myelofibrosis) was studied in the Caucasian ethnicity population of Vyatka region of the Russian Federation. It was found that NQO1*609T allele, NQO1*609T genotypes, and homozygous carriage of a deletion (null) allele of GSTT1 gene are associated with the risk of development of myeloproliferative neoplasms (OR=1.29, 95%CI=1.02-1.64, p=0.04; OR=1.39, 95%CI=1.04-1.85, p=0.03; and OR=1.48, 95%CI=1.03-2.12, p=0.03, respectively). However, no influence of GSTM1 and GSTP1 gene polymorphisms on the risk of development of myeloproliferative disorders was registered.