Polymorphisms of the CYP1B1 gene and hepatocellular carcinoma risk in a Chinese population

Wood cookstove use is associated with gastric cancer in Central America and mediated by host genetics

Biomass cookstove food preparation is linked to aero-digestive cancers, mediated by ingested and inhaled carcinogens (e.g., heterocyclic amines, and polycyclic aromatic hydrocarbons). We investigated the association between gastric adenocarcinoma, wood cookstove use, H. pylori CagA infection and risk modification by variants in genes that metabolize and affect the internal dose of carcinogens. We conducted a population-based, case-control study (814 incident cases, 1049 controls) in rural Honduras, a high-incidence region with a homogeneous diet and endemic H. pylori infection, primarily with the high-risk CagA genotype. We investigated factors including wood cookstove use, H. pylori CagA serostatus, and 15 variants from 7 metabolizing genes, and the interactions between wood stove use and the genetic variants. Male sex (OR 2.0, 1.6-2.6), age (OR 1.04, 1.03-1.05), wood cookstove use (OR 2.3, 1.6-3.3), and CagA serostatus (OR 3.5, 2.4-5.1) and two SNPs in CYP1B1 (rs1800440 and rs1056836) were independently associated with gastric cancer in multivariate analysis. In the final multivariate model, a highly significant interaction (OR 3.1, 1.2-7.8) was noted between wood cookstove use and the rs1800440 metabolizing genotype, highlighting an important gene-environment interaction. Lifetime wood cookstove use associates with gastric cancer risk in the high-incidence regions of Central America, and the association is dependent on the rs1800440 genotype in CYP1B1. H. pylori CagA infection, wood cookstove use and the rs1800440 genotype, all of which are highly prevalent, informs who is at greatest risk from biomass cookstove use.

Human CYP1B1 enzyme-mediated, AhR enhanced activation of aflatoxin B1 for its genotoxicity in human cells

Aflatoxin B1 (AFB1) is a human procarcinogen known to be activated by cytochrome P450 (CYP) 1A2 and 3A4. In a previous study AFB1 caused chromosomal rearrangement in a yeast strain genetically engineered for stably expressing human CYP1B1. Yet, further verification of the effect of AFB1 in human cells, a potential role of the aryl hydrocarbon receptor (AhR), and CYP1B1-catalyzed AFB1 metabolism remain unidentified. In this study, a human hepatocyte (L-02) line and a human lymphoblastoid (TK6) cell line were genetically engineered for the expression of human CYP1B1, producing L-02-hCYP1B1 and TK6-hCYP1B1, respectively. They were exposed to AFB1 and analyzed for the formation of micronucleus and elevation of γ-H2AX (indicating double-strand DNA breaks); the metabolites formed by CYP1B1 from AFB1 after incubation of AFB1 with human CYP1B1 isoenzyme microsomes were determined by LC-MS. The results showed significantly more potent induction of micronucleus by AFB1 in L-02-hCYP1B1 and TK6-hCYP1B1 than in the parental (L-02 and TK6) cells, and the effects were reduced by (E)- 2,3',4,5'-tetramethoxystilbene, a specific CYP1B1 inhibitor. In the AFB1- CYP1B1 microsomes incubations AFM1, a known stable metabolite of AFB1, was detected. Moreover, in L-02 and TK6 cells, AFB1 apparently increased the protein levels of AhR, ANRT and CYP1B1, and caused the nuclear translocation of AhR and ARNT, the latter effect being blocked by BAY-218 (an inhibitor of AhR). In conclusion, this study indicates that human CYP1B1 is capable of metabolically activating AFB1 through the AhR signaling pathway.

Genetic Epidemiology of Primary Congenital Glaucoma in the 22 Arab Countries: A Systematic Review

PURPOSE

Primary congenital glaucoma (PCG) is a rare glaucoma type that develops in early infantile period and contributes to an elevated pressure on ocular cavity. Variants in CYP1B1 gene are the most encountered in PCG cases. The prevalence of PCG is relatively high among Arabs, however its genetic epidemiology remains understudied. This study aims to systematically identify all reported PCG disease-causing variants in the Arab population and investigate their potential genotype-phenotype correlations.

METHODS

We searched four different databases (PubMed, ScienceDirect, Google Scholar, and Scopus) from the time of inception until July 2020. Broad search terms were used to capture all possible information about the genetic epidemiology of PCG among Arabs.

RESULTS

We identified a total of 77 disease-causing variants in 361 patients and 88 families; of these, 33 were unique to Arabs. Sixty-nine variants were identified in the CYP1B1 gene, five variants were in the MYOC gene and single variants were reported in NTF4, FOXC1, and WDR36 genes. The most common reported variant was the c.182 G > A in the CYP1B1 gene. All identified variants were from ten Arab Countries (Saudi Arabia, Kuwait, Oman, Egypt, Morocco, Lebanon, Tunisia, Iraq, Algeria, and Mauritania). We identified 44 shared variants with other ethnicities demonstrated a distinctive genotype-phenotype correlation. Consanguinity was observed in the majority of Arab PCG patients, ranging from 45% to 100%.

CONCLUSION

PCG causing variants were identified in 10 Arab countries, which were mostly detected in the CYB1P1 gene. Arab patients with PCG seem to have distinctive genotype-phenotype correlations.

The Activation of Procarcinogens by CYP1A1/1B1 and Related Chemo-Preventive Agents: A Review

CYP1A1 and CYP1B1 are extrahepatic P450 family members involved in the metabolism of procarcinogens, such as PAHs, heterocyclic amines and halogen-containing organic compounds. CYP1A1/1B1 also participate in the metabolism of endogenous 17-β-estradiol, producing estradiol hydroquinones, which are the intermediates of carcinogenic semiquinones and quinones. CYP1A1 and CYP1B1 proteins share approximately half amino acid sequence identity but differ in crystal structures. As a result, CYP1A1 and CYP1B1 have different substrate specificity to chemical procarcinogens. This review will introduce the general molecular biology knowledge of CYP1A1/1B1 and the metabolic processes of procarcinogens regulated by these two enzymes. Over the last four decades, a variety of natural products and synthetic compounds which interact with CYP1A1/1B1 have been identified as effective chemo-preventive agents against chemical carcinogenesis. These compounds are mainly classified as indirect or direct CYP1A1/1B1 inhibitors based on their distinct mechanisms. Indirect CYP1A1/1B1 inhibitors generally impede the transcription and translation of CYP1A1/1B1 genes or interfere with the translocation of aryl hydrocarbon receptor (AHR) from the cytosolic domain to the nucleus. On the other hand, direct inhibitors inhibit the catalytic activities of CYP1A1/1B1. Based on the structural features, the indirect inhibitors can be categorized into the following groups: flavonoids, alkaloids and synthetic aromatics, whereas the direct inhibitors can be categorized into flavonoids, coumarins, stilbenes, sulfur containing isothiocyanates and synthetic aromatics. This review will summarize the in vitro and in vivo activities of these chemo-preventive agents, their working mechanisms, and related SARs. This will provide a better understanding of the molecular mechanism of CYP1 mediated carcinogenesis and will also give great implications for the discovery of novel chemo-preventive agents in the near future.

Epigenetic Regulation of Differentially Expressed Drug-Metabolizing Enzymes in Cancer

Drug metabolism is a biotransformation process of drugs, catalyzed by drug-metabolizing enzymes (DMEs), including phase I DMEs and phase II DMEs. The aberrant expression of DMEs occurs in the different stages of cancer. It can contribute to the development of cancer and lead to individual variations in drug response by affecting the metabolic process of carcinogen and anticancer drugs. Apart from genetic polymorphisms, which we know the most about, current evidence indicates that epigenetic regulation is also central to the expression of DMEs. This review summarizes differentially expressed DMEs in cancer and related epigenetic changes, including DNA methylation, histone modification, and noncoding RNAs. Exploring the epigenetic regulation of differentially expressed DMEs can provide a basis for implementing individualized and rationalized medication. Meanwhile, it can promote the development of new biomarkers and targets for the diagnosis, treatment, and prognosis of cancer. SIGNIFICANCE STATEMENT: This review summarizes the aberrant expression of DMEs in cancer and the related epigenetic regulation of differentially expressed DMEs. Exploring the epigenetic regulatory mechanism of DMEs in cancer can help us to understand the role of DMEs in cancer progression and chemoresistance. Also, it provides a basis for developing new biomarkers and targets for the diagnosis, treatment, and prognosis of cancer.

CYP1B1 G199T Polymorphism Affects Prognosis of NSCLC Patients with the Potential to Be an Indicator and Target for Precise Drug Intervention

CYP1B1 gene single nucleotide polymorphisms G119T, C432G, and A453G were tested among 164 NSCLC patients treated by Video-Assisted Thoracoscopic Surgery. After a follow-up period of 5 years, it was found that CYP1B1 G119T mutant genotypes were related to a higher risk of tumor recurrence and death after surgical resection. However, C432G and A453G genotypes had no influence on long-term prognosis of the study cohort. Thus, G199T alleles are supposed to be an auxiliary predictor for prognosis of NSCLC patients and a potential target for precise drug intervention, as well as a candidate for further anticancer drug research.

Relationships between cell cycle pathway gene polymorphisms and risk of hepatocellular carcinoma

AIM: To investigate the associiations between the polymorphisms of cell cycle pathway genes and the risk of hepatocellular carcinoma (HCC).

METHODS: We enrolled 1127 cases newly diagnosed with HCC from the Tumor Hospital of Guangxi Medical University and 1200 non-tumor patients from the First Affiliated Hospital of Guangxi Medical University. General demographic characteristics, behavioral information, and hematological indices were collected by unified questionnaires. Genomic DNA was isolated from peripheral venous blood using Phenol-Chloroform. The genotyping was performed using the Sequenom MassARRAY iPLEX genotyping method. The association between genetic polymorphisms and risk of HCC was shown by P-value and the odd ratio (OR) with 95% confidence interval (CI) using the unconditional logistic regression after adjusting for age, sex, nationality, smoking, drinking, family history of HCC, and hepatitis B virus (HBV) infection. Moreover, stratified analysis was conducted on the basis of the status of HBV infection, smoking, and alcohol drinking.

RESULTS: The HCC risk was lower in patients with the MCM4 rs2305952 CC (OR = 0.22, 95%CI: 0.08-0.63, P = 0.01) and with the CHEK1 rs515255 TC, TT, TC/TT (OR = 0.73, 95%CI: 0.56-0.96, P = 0.02; OR = 0.67, 95%CI: 0.46-0.97, P = 0.04; OR = 0.72, 95%CI: 0.56-0.92, P = 0.01, respectively). Conversely, the HCC risk was higher in patients with the KAT2B rs17006625 GG (OR = 1.64, 95%CI: 1.01-2.64, P = 0.04). In addition, the risk was markedly lower for those who were carriers of MCM4 rs2305952 CC and were also HBsAg-positive and non-drinking and non-smoking (P < 0.05, respectively) and for those who were carriers of CHEK1 rs515255 TC, TT, TC/TT and were also HBsAg-negative and non-drinking (P < 0.05, respectively). Moreover, the risk was higher for those who were carriers of KAT2B rs17006625 GG and were also HBsAg-negative (P < 0.05).

CONCLUSION: Of 12 cell cycle pathway genes, MCM4, CHEK1 and KAT2B polymorphisms may be associated with the risk of HCC.

Whole-exome sequencing reveals potential molecular predictors of relapse after discontinuation of the targeted therapy in chronic myeloid leukemia patients

Chronic myeloid leukemia (CML) is a myeloproliferative disease well treated by tyrosine kinase inhibitors (TKIs). The aim was to identify genes with a predictive value for relapse-free survival after TKI cessation in CML patients. We performed whole-exome sequencing of DNA from six CML patients in long-lasting deep molecular remission. Patients were divided into two groups with relapse (n = 3) and without relapse (n = 3) after TKI discontinuation. We found variants in genes CYP1B1, ALPK2, and IRF1 in group of patients with relapse and one variant in gene PARP9 in group of patients without relapse. We verified prognostic value of the found markers in a small group of patients with TKI discontinuation and demonstrated their high sensitivity (77%), specificity (86%), positive (85%), and negative (79%) predictive values. Thus we revealed genetic variants, which are potential markers of outcome prediction in CML patients after TKI discontinuation.