Cytochrome P1B1 ( CYP1B1 ) polymorphisms and cancer risk: A meta-analysis of 52 studies

Meta-analysis identifies key genes and pathways implicated in Benzo[a]pyrene exposure response

INTRODUCTION

Benzo[a]pyrene (B[a]P) is a carcinogenic polycyclic aromatic hydrocarbon that poses significant risks to human health. B[a]P influences cellular processes via intricate interactions; however, a comprehensive understanding of B[a]P's effects on the transcriptome remains elusive. This study aimed to conduct a comprehensive analysis focused on identifying relevant genes and signaling pathways affected by B[a]P exposure and their impact on human gene expression.

METHODS

We searched the Gene Expression Omnibus database and identified four studies involving B[a]P exposure in human cells (T lymphocytes, hepatocellular carcinoma cells, and C3A cells). We utilized two approaches for differential expression analysis: the LIMMA package and linear regression. A meta-analysis was utilized to combine log fold changes (FC) and p-values from the identified studies using a random effects model. We identified significant genes at a Bonferroni-adjusted significance level of 0.05 and determined overlapping genes across datasets. Pathway enrichment analysis elucidated key cellular processes modulated by B[a]P exposure.

RESULTS

The meta-analysis revealed significant upregulation of CYP1B1 (log FC = 1.15, 95% CI: 0.51-1.79, P < 0.05, I2 = 82%) and ASB2 (log FC = 0.44, 95% CI: 0.20-0.67, P < 0.05, I2 = 40%) in response to B[a]P exposure. Pathway analyses identified 26 significantly regulated pathways, with the top including Aryl Hydrocarbon Receptor Signaling (P = 0.00214) and Xenobiotic Metabolism Signaling (P = 0.00550). Key genes CYP1A1, CYP1B1, and CDKN1A were implicated in multiple pathways, highlighting their roles in xenobiotic metabolism, oxidative stress response, and cell cycle regulation.

CONCLUSION

The results provided insights into the mechanisms of B[a]P toxicity, highlighting CYP1B1's key role in B[a]P bioactivation. The findings underscored the complexity of B[a]P's mechanisms of action and their potential implications for human health. The identified genes and pathways provided a foundation for further exploration and enhanced our understanding of the multifaceted biological activities associated with B[a]P exposure.

Attenuation of Polycyclic Aromatic Hydrocarbon (PAH)-Induced Carcinogenesis and Tumorigenesis by Omega-3 Fatty Acids in Mice In Vivo

Lung cancer is the leading cause of cancer death worldwide. Polycyclic aromatic hydrocarbons (PAHs) are metabolized by the cytochrome P450 (CYP)1A and 1B1 to DNA-reactive metabolites, which could lead to mutations in critical genes, eventually resulting in cancer. Omega-3 fatty acids, such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), are beneficial against cancers. In this investigation, we elucidated the mechanisms by which omega-3 fatty acids EPA and DHA will attenuate PAH-DNA adducts and lung carcinogenesis and tumorigenesis mediated by the PAHs BP and MC. Adult wild-type (WT) (A/J) mice, Cyp1a1-null, Cyp1a2-null, or Cyp1b1-null mice were exposed to PAHs benzo[a]pyrene (BP) or 3-methylcholanthrene (MC), and the effects of omega-3 fatty acid on PAH-mediated lung carcinogenesis and tumorigenesis were studied. The major findings were as follows: (i) omega-3 fatty acids significantly decreased PAH-DNA adducts in the lungs of each of the genotypes studied; (ii) decreases in PAH-DNA adduct levels by EPA/DHA was in part due to inhibition of CYP1B1; (iii) inhibition of soluble epoxide hydrolase (sEH) enhanced the EPA/DHA-mediated prevention of pulmonary carcinogenesis; and (iv) EPA/DHA attenuated PAH-mediated carcinogenesis in part by epigenetic mechanisms. Taken together, our results suggest that omega-3 fatty acids have the potential to be developed as cancer chemo-preventive agents in people.

Metal exposure and breast cancer among Northern Mexican women: assessment of genetic susceptibility

This study aims to assess breast cancer (BC) association with metals and whether polymorphisms in CYP1A1, CYP1B1, GSTM1 and GSTT1 act as confounders or as modifiers of those relationships. We performed a secondary analysis of 499 histologically confirmed BC cases and the same number of age-matched population controls. We measured urinary concentrations of 18 metals with mass spectrometry. We determined the genetic variants of interest by allelic discrimination and multiplex PCR. After adjusting for covariates, we found BC negatively associated with arsenic, barium, cobalt, copper, magnesium, molybdenum and vanadium concentrations and positively with those of caesium, manganese, tin and thallium. Most associations remained after stratifying by the genetic variants. We identified that polymorphisms in CYP1B1, CYP1A1 and GSTM1 genes interacted with some metals on BC: interaction p-values CYP1B1 G119T × antimony= 0.036, CYP1B1 G119T × cobalt <0.001, CYP1B1 G119T × tin= 0.032, CYP1A1 A4889G × aluminium= 0.018, CYP1A1 A4889G × arsenic= 0.031, CYP1A1 A4889G × nickel= 0.036, CYP1A1 A4889G × vanadium= 0.031 and GSTM1 deletion × barium= 0.035. Exposure to various individual metals, along with genetic characteristics may contribute to BC development. Further studies are warranted to confirm our results.

CYP1B1: A Novel Molecular Biomarker Predicts Molecular Subtype, Tumor Microenvironment, and Immune Response in 33 Cancers

BACKGROUND

Cytochrome P450 Family 1 Subfamily B Member 1 (CYP1B1) is a critical metabolic enzyme of melatonin. Although melatonin has been identified to exhibit tumor suppressing activity, the role and mechanism of the clinical and immunological characteristics of CYP1B1 in cancer remain unclear.

METHODS

In this study, RNA expression and clinical data were obtained from The Cancer Genome Atlas (TCGA) across 33 solid tumors. The expression, survival, immune subtype, molecular subtype, tumor mutation burden (TMB), microsatellite instability (MSI), biological pathways, and function in vitro and vivo were evaluated. The predictive value of CYP1B1 in immune cohorts was further explored.

RESULTS

We found the dysregulated expression of CYP1B1 was associated with the clinical stage and tumor grade. Immunological correlation analysis showed CYP1B1 was positively correlated with the infiltration of lymphocyte, immunomodulator, chemokine, receptor, and cancer-associated fibroblasts (CAFs) in most cancer. Meanwhile, CYP1B1 was involved in immune subtype and molecular subtype, and was connected with TMB, MSI, neoantigen, the activation of multiple melatonergic and immune-related pathways, and therapeutic resistance.

CONCLUSIONS

Together, this study comprehensively revealed the role and mechanism of CYP1B1 and explored the significant association between CYP1B1 expression and immune activity. These findings provide a promising predictor and molecular target for clinical immune treatment.

ZNF276 promotes the malignant phenotype of breast carcinoma by activating the CYP1B1-mediated Wnt/β-catenin pathway

Zinc finger proteins (ZNFs) have been demonstrated to participate extensively in breast cancer progression by functioning as transcription factors, but there are still a variety of ZNFs whose biological mechanisms remain unknown. Here, we show that zinc finger protein 276 (ZNF276) is highly expressed in breast cancer tissues and cell lines. Higher level of ZNF276 correlated with poor prognosis. Gain-of and loss-of function suggested that ZNF276 is essential for the proliferation, migration and invasion of breast cancer cells in vitro and metastasis in vivo. RNA-sequencing and CUT&Tag assay revealed that ZNF276 controlled a variety of growth and metastasis-related genes expression. ZNF276 transcriptionally promoted the expression of CYP1B1 by directly binds to the promoter region of the CYP1B1 through its C₂H₂ domain. ZNF276 facilitated the translocation of β-catenin from cytoplasm to nucleus through CYP1B1, leading to the upregulation of cyclin D1 and c-Myc, and the activation of the Wnt/β-catenin pathway. Knockdown of CYP1B1 significantly blocked the ZNF276-mediated effects on cell proliferation, migration and invasion. Lastly, ZNF276 interacted with MAGEB2 which enhanced the binding of ZNF276 at the CYP1B1 promoter, promoted CYP1B1 expression and Wnt signaling activation. Collectively, these findings highlight the oncogenic role of ZNF276 on breast cancer cell proliferation and metastasis. Targeting ZNF276/MAGEB2 axis may serve as a potential therapeutic strategy for breast cancer patients.

HAPLN1 Affects Cell Viability and Promotes the Pro-Inflammatory Phenotype of Fibroblast-Like Synoviocytes

HAPLN1 maintains aggregation and the binding activity of extracellular matrix (ECM) molecules (such as hyaluronic acid and proteoglycan) to stabilize the macromolecular structure of the ECM. An increase in HAPLN1 expression is observed in a few types of musculoskeletal diseases including rheumatoid arthritis (RA); however, its functions are obscure. This study examined the role of HAPLN1 in determining the viability, proliferation, mobility, and pro-inflammatory phenotype of RA- fibroblast-like synoviocytes (RA-FLSs) by using small interfering RNA (siHAPLN1), over-expression vector (HAPLN1^OE), and a recombinant HAPLN1 (rHAPLN1) protein. HAPLN1 was found to promote proliferation but inhibit RA-FLS migration. Metformin, an AMPK activator, was previously found by us to be able to inhibit FLS activation but promote HAPLN1 secretion. In this study, we confirmed the up-regulation of HAPLN1 in RA patients, and found the positive relationship between HAPLN1 expression and the AMPK level. Treatment with either si-HAPLN1 or HAPLN1^OE down-regulated the expression of AMPK-ɑ gene, although up-regulation of the level of p-AMPK-ɑ was observed in RA-FLSs. si-HAPLN1 down-regulated the expression of proinflammatory factors like TNF-ɑ, MMPs, and IL-6, while HAPLN1^OE up-regulated their levels. qPCR assay indicated that the levels of TGF-β, ACAN, fibronectin, collagen II, and Ki-67 were down-regulated upon si-HAPLN1 treatment, while HAPLN1^OE treatment led to up-regulation of ACAN and Ki-67 and down-regulation of cyclin-D1. Proteomics of si-HAPLN1, rHAPLN1, and mRNA-Seq analysis of rHAPLN1 confirmed the functions of HAPLN1 in the activation of inflammation, proliferation, cell adhesion, and strengthening of ECM functions. Our results for the first time demonstrate the function of HAPLN1 in promoting the proliferation and pro-inflammatory phenotype of RA-FLSs, thereby contributing to RA pathogenesis. Future in-depth studies are required for better understanding the role of HAPLN1 in RA.

CYP1B1 converts procarcinogens into genotoxins in Saccharomyces cerevisiae

CYP1B1 activates many chemical carcinogens into potent genotoxins, and allelic variants are risk factors in lung, breast, and prostate cancer. However, few eukaryotic genetic instability endpoints have been directly measured for CYP1B1-activated metabolites. In this study, we expressed human CYP1B1 in yeast strains that measure DNA damage-associated toxicity and frequencies of chromosomal translocations. DNA damage-associated toxicity was measured in a rad4 rad51 strain, defective in both DNA excision and recombinational repair. Frequencies of chromosomal translocations were measured in diploid yeast strains containing two his3 fragments. These strains were exposed to benzo[a]pyrene-7,8-dihydrodiol (BaP-DHD), aflatoxin B₁ (AFB₁), and the heterocyclic aromatic amines, 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) and 2-amino-3-methylimidazo[4,5-f]quinoline (IQ). We observed that AFB₁, BaP-DHD, IQ, and MeIQx conferred toxicity in the DNA repair mutant expressing CYP1B1. Translocation frequencies increased eight-fold and three-fold after exposure to 50 μM AFB₁ and 33 μM BaP-DHD respectively. A DNA damage response was observed after AFB₁ exposure, as measured by the induction of the small subunit of ribonucleotide reductase, Rnr3. While CYP1B1-mediated activation of BaP-DHD and heterocyclic aromatic amines was expected, activation of AFB₁ to become a potent recombinagen was not expected. These studies demonstrate that chromosomal rearrangement is a useful genotoxic endpoint for CYP1B1-mediated carcinogen activation.

Cytochrome P450 1B1 Overexpression in Cervical Cancers: Cross-sectional Study

Background

Current standard treatments for patients with recurrent cervical cancer are not very effective and are associated with severe toxicity. Recently, the rational approach for the discovery of new therapies for cervical cancer is based on the alterations in the molecular biology of cancer cells. One of the emerging molecular changes in cancer cells is the aberrant expression of cytochrome P450 1B1 (CYP1B1). This unique enzyme has been reported to be selectively overexpressed in several cancers.

Objective

The aim of this study was to examine CYP1B1 expression in cervical cancers and to assess the enzyme’s relationship with several clinicopathological features.

Methods

Immunohistochemistry was performed to examine CYP1B1 expression in 100 patient samples with cervical cancer and 10 patient samples with normal healthy cervical tissues.

Results

CYP1B1 was expressed in the majority of the cervical cancer samples (91/100, 91.0%) but not in normal healthy cervical samples. The difference in the expression of CYP1B1 between healthy and tumorous cervical tissues was significant (P=.01). Moreover, the frequency of CYP1B1 expression was found to be significantly higher in patients with advanced grades of the disease (P=.03) and in patients having metastasis to the lymph nodes (P=.01). Surprisingly, there was a significantly higher expression of CYP1B1 in patients with a high prevalence of human papilloma virus 16/18 (P=.04).

Conclusions

The differential profile of CYP1B1 expression between cervical cancer tissues and normal cervical tissues suggests that CYP1B1 may be used as a target for future therapeutic exploitations.

Sequence Polymorphism in Xenobiotic Metabolising Genes in Iraqi Colorectal Cancer Patients

OBJECTIVES

Colorectal cancer (CRC) is the third most prevalent malignant neoplasm. Genetic variations in the xenobiotic metabolising cytochrome enzymes. Family 1 Subfamily A Member 1 (CYP1A1) and Family 1 Subfamily B Member 1 (CYP1B1) might play a role in cancer pathogenesis and prognosis. The aim of this work is to determine the frequency of Single Nucleotide Polymorphisms (SNPs) in CYP1A1 (rs1048943, Ile462VaI and rs4646903/MSP1) and CYP1B1 (rs1056836, Leu432Val) genes in patients with CRC cancer. It was also an attempt to identify the association between SNPs and CRC and its stage and grade at diagnosis.

METHODS

This case-control study was conducted in Kirkuk/Iraq, 200 patients with CRC and 200 cancer free control subjects were enrolled. Genomic DNA was extracted from venous blood samples and screened for SNPs using Restriction Fragment Length  Polymorphism (RFLP) and confirmed by the direct DNA sequencing.

RESULTS

The reference genotype of CYP1A1 gene rs1048943 is AA. Both the AG and GG variants were  significantly more frequent in the cancer group and associated with increased risks of CRC and its later stages (stages III and IV)  and poor  differentiation (p <0.01). The reference genotype of CYP1A1 rs4646903 is TT. The variant genotypes, TC and CC, had no significant association with increased odds of cancer (P>0.05) or with tumour stage or its grade (p>0.05). The GG genotype of CYP1B1 rs1056836 was the reference genotype. The CG and CC variants were not associated with increased risks of CRC (P>0.05) or its stage or grade except the CG genotype which was associated with poor differentiation (OR= 3.4, 95 % CI= 1.8 -6.5, p <0.001).

CONCLUSION

CYP1A1 gene rs1048943 SNPs can represent a potential future marker for   CRC risk prediction and prognosis. Further evaluation in large scale studies will provide greater understanding of the effects of other genes SNPs on CRC  risk and prognosis.
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CYP1B1 as a therapeutic target in cardio-oncology

Cardiovascular complications have been frequently reported in cancer patients and survivors, mainly because of various cardiotoxic cancer treatments. Despite the known cardiovascular toxic effects of these treatments, they are still clinically used because of their effectiveness as anti-cancer agents. In this review, we discuss the growing body of evidence suggesting that inhibition of the cytochrome P450 1B1 enzyme (CYP1B1) can be a promising therapeutic strategy that has the potential to prevent cancer treatment-induced cardiovascular complications without reducing their anti-cancer effects. CYP1B1 is an extrahepatic enzyme that is expressed in cardiovascular tissues and overexpressed in different types of cancers. A growing body of evidence is demonstrating a detrimental role of CYP1B1 in both cardiovascular diseases and cancer, via perturbed metabolism of endogenous compounds, production of carcinogenic metabolites, DNA adduct formation, and generation of reactive oxygen species (ROS). Several chemotherapeutic agents have been shown to induce CYP1B1 in cardiovascular and cancer cells, possibly via activating the Aryl hydrocarbon Receptor (AhR), ROS generation, and inflammatory cytokines. Induction of CYP1B1 is detrimental in many ways. First, it can induce or exacerbate cancer treatment-induced cardiovascular complications. Second, it may lead to significant chemo/radio-resistance, undermining both the safety and effectiveness of cancer treatments. Therefore, numerous preclinical studies demonstrate that inhibition of CYP1B1 protects against chemotherapy-induced cardiotoxicity and prevents chemo- and radio-resistance. Most of these studies have utilized phytochemicals to inhibit CYP1B1. Since phytochemicals have multiple targets, future studies are needed to discern the specific contribution of CYP1B1 to the cardioprotective and chemo/radio-sensitizing effects of these phytochemicals.

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.

CYP enzymes, expressed within live human suspension cells, are superior to widely-used microsomal enzymes in identifying potent CYP1A1/CYP1B1 inhibitors: Identification of quinazolinones as CYP1A1/CYP1B1 inhibitors that efficiently reverse B[a]P toxicity and cisplatin resistance

Microsomal cytochrome P450 (CYP) enzymes, isolated from recombinant bacterial/insect/yeast cells, are extensively used for drug metabolism studies. However, they may not always portray how a developmental drug would behave in human cells with intact intracellular transport mechanisms. This study emphasizes the usefulness of human HEK293 kidney cells, grown in 'suspension' for expression of CYPs, in finding potent CYP1A1/CYP1B1 inhibitors, as possible anticancer agents. With live cell-based assays, quinazolinones 9i/9b were found to be selective CYP1A1/CYP1B1 inhibitors with IC₅₀ values of 30/21 nM, and > 150-fold selectivity over CYP2/3 enzymes, whereas they were far less active using commercially-available CYP1A1/CYP1B1 microsomal enzymes (IC₅₀, >10/1.3-1.7 μM). Compound 9i prevented CYP1A1-mediated benzo[a]pyrene-toxicity in normal fibroblasts whereas 9b completely reversed cisplatin resistance in PC-3/prostate, COR-L23/lung, MIAPaCa-2/pancreatic and LS174T/colon cancer cells, underlining the human-cell-assays' potential. Our results indicate that the most potent CYP1A1/CYP1B1 inhibitors would not have been identified if one had relied merely on microsomal enzymes.

Cancer chemoprevention revisited: Cytochrome P450 family 1B1 as a target in the tumor and the microenvironment

Cancer chemoprevention is the use of synthetic, natural or biological agents to prevent or delay the development or progression of malignancies. Intriguingly, many phytochemicals with anti-inflammatory and anti-angiogenic effects, recently proposed as chemoprevention strategies, are inhibitors of Cytochrome P450 family 1B1 (CYP1B1), an enzyme overexpressed in a wide variety of tumors and associated with angiogenesis. In turn, pro-inflammatory cytokines were reported to boost CYP1B1 expression, suggesting a key role of CYP1B1 in a positive loop of inflammatory angiogenesis. Other well-known pro-tumorigenic activities of CYP1B1 rely on metabolic bioactivation of xenobiotics and steroid hormones into their carcinogenic derivatives. In contrast to initial in vitro observations, in vivo studies demonstrated a protecting role against cancer for the other CYP1 family members (CYP1A1 and CYP1A2), suggesting that the specificity of CYP1 family inhibitors should be carefully taken into account for developing potential chemoprevention strategies. Recent studies also proposed a role of CYP1B1 in multiple cell types found within the tumor microenvironment, including fibroblasts, endothelial and immune cells. Overall, our review of the current literature suggests a positive loop between inflammatory cytokines and CYP1B1, which in turn may play a key role in cancer angiogenesis, acting on both cancer cells and the tumor microenvironment. Strategies aiming at specific CYP1B1 inhibition in multiple cell types may translate into clinical chemoprevention and angioprevention approaches.

Potential role of CYP1B1 in the development and treatment of metabolic diseases

Cytochrome P450 1B1 (CYP1B1), a member of CYP superfamily, is expressed in liver and extrahepatic tissues carries out the metabolism of numerous xenobiotics, including metabolic activation of polycyclic aromatic hydrocarbons. Surprisingly, CYP1B1 was also shown to be important in regulating endogenous metabolic pathways, including the metabolism of steroid hormones, fatty acids, melatonin, and vitamins. CYP1B1 and nuclear receptors including peroxisome proliferator-activated receptors (PPARs), estrogen receptor (ER), and retinoic acid receptors (RAR) contribute to the maintenance of the homeostasis of these endogenous compounds. Many natural flavonoids and synthetic stilbenes show inhibitory activity toward CYP1B1 expression and function, notably isorhamnetin and 2,4,3',5'-tetramethoxystilbene. Accumulating evidence indicates that modulation of CYP1B1 can decrease adipogenesis and tumorigenesis, and prevent obesity, hypertension, atherosclerosis, and cancer. Therefore, it may be feasible to consider CYP1B1 as a therapeutic target for the treatment of metabolic diseases.

Development of an In Vitro Model to Screen CYP1B1-Targeted Anticancer Prodrugs

Cytochrome P450 1B1 (CYP1B1) is an anticancer therapeutic target due to its overexpression in a number of steroid hormone-related cancers. One anticancer drug discovery strategy is to develop prodrugs specifically activated by CYP1B1 in malignant tissues to cytotoxic metabolites. Here, we aimed to develop an in vitro screening model for CYP1B1-targeted anticancer prodrugs using the KLE human endometrial carcinoma cell line. KLE cells demonstrated superior stability of CYP1B1 expression relative to transiently transfected cells and did not express any appreciable amount of cognate CYP1A1 or CYP1A2, which would have compromised the specificity of the screening assay. The effect of two CYP1B1-targeted probe prodrugs on KLE cells was evaluated in the absence and presence of a CYP1B1 inhibitor to chemically "knock out" CYP1B1 activity (CYP1B1 inhibited). Both probe prodrugs were more toxic to KLE cells than to CYP1B1-inhibited KLE cells and significantly induced G0/G1 arrest and decreased the S phase in KLE cells. They also exhibited pro-apoptotic effects in KLE cells, which were attenuated in CYP1B1-inhibited KLE cells. In summary, a KLE cell-based model has been characterized to be suitable for identifying CYP1B1-targeted anticancer prodrugs and should be further developed and employed for screening chemical libraries.

Association of androgen metabolism gene polymorphisms with prostate cancer risk and androgen concentrations: Results from the Prostate Cancer Prevention Trial

BACKGROUND

Prostate cancer is highly influenced by androgens and genes. The authors investigated whether genetic polymorphisms along the androgen biosynthesis and metabolism pathways are associated with androgen concentrations or with the risk of prostate cancer or high-grade disease from finasteride treatment.

METHODS

A nested case-control study from the Prostate Cancer Prevention Trial using data from men who had biopsy-proven prostate cancer (cases) and a group of biopsy-negative, frequency-matched controls was conducted to investigate the association of 51 single nucleotide polymorphisms (SNPs) in 12 genes of the androgen pathway with overall (total), low-grade, and high-grade prostate cancer incidence and serum hormone concentrations.

RESULTS

There were significant associations of genetic polymorphisms in steroid 5α-reductase 1 (SRD5A1) (reference SNPs: rs3736316, rs3822430, rs1560149, rs248797, and rs472402) and SRD5A2 (rs2300700) with the risk of high-grade prostate cancer in the placebo arm of the Prostate Cancer Prevention Trial; 2 SNPs were significantly associated with an increased risk (SRD5A1 rs472402 [odds ratio, 1.70; 95% confidence interval, 1.05-2.75; Ptrend = .03] and SRD5A2 rs2300700 [odds ratio, 1.94; 95% confidence interval, 1.19-3.18; Ptrend = .01]). Eleven SNPs in SRD5A1, SRD5A2, cytochrome P450 family 1, subfamily B, polypeptide 1 (CYP1B1), and CYP3A4 were associated with modifying the mean concentrations of serum androgen and sex hormone-binding globulin; and 2 SNPs (SRD5A1 rs824811 and CYP1B1 rs10012; Ptrend < .05) consistently and significantly altered all androgen concentrations. Several SNPs (SRD5A1 rs3822430, SRD5A2 rs2300700, CYP3A43 rs800672, and CYP19 rs700519; Ptrend < .05) were significantly associated with both circulating hormone levels and prostate cancer risk.

CONCLUSIONS

Germline genetic variations of androgen-related pathway genes are associated with serum androgen concentrations and the risk of prostate cancer. Further studies to examine the functional consequence of novel causal variants are warranted. Cancer 2016;122:2332-2340. © 2016 American Cancer Society.

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.

Hormone-related pathways and risk of breast cancer subtypes in African American women

We sought to investigate genetic variation in hormone pathways in relation to risk of overall and subtype-specific breast cancer in women of African ancestry (AA). Genotyping and imputation yielded data on 143,934 SNPs in 308 hormone-related genes for 3663 breast cancer cases (1098 ER-, 1983 ER+, 582 ER unknown) and 4687 controls from the African American Breast Cancer Epidemiology and Risk (AMBER) Consortium. AMBER includes data from four large studies of AA women: the Carolina Breast Cancer Study, the Women's Circle of Health Study, the Black Women's Health Study, and the Multiethnic Cohort Study. Pathway- and gene-based analyses were conducted, and single-SNP tests were run for the top genes. There were no strong associations at the pathway level. The most significantly associated genes were GHRH, CALM2, CETP, and AKR1C1 for overall breast cancer (gene-based nominal p ≤ 0.01); NR0B1, IGF2R, CALM2, CYP1B1, and GRB2 for ER+ breast cancer (p ≤ 0.02); and PGR, MAPK3, MAP3K1, and LHCGR for ER- disease (p ≤ 0.02). Single-SNP tests for SNPs with pairwise linkage disequilibrium r (2) < 0.8 in the top genes identified 12 common SNPs (in CALM2, CETP, NR0B1, IGF2R, CYP1B1, PGR, MAPK3, and MAP3K1) associated with overall or subtype-specific breast cancer after gene-level correction for multiple testing. Rs11571215 in PGR (progesterone receptor) was the SNP most strongly associated with ER- disease. We identified eight genes in hormone pathways that contain common variants associated with breast cancer in AA women after gene-level correction for multiple testing.

Polycyclic aromatic hydrocarbons and cytochrome P450 in HIV pathogenesis

High prevalence of cigarette smoking in HIV patients is associated with increased HIV pathogenesis and disease progression. While the effect of smoking on the occurrence of lung cancer has been studied extensively, the association between smoking and HIV pathogenesis is poorly studied. We have recently shown the possible role of cytochrome P450 (CYP) in smoking/nicotine-mediated viral replication. In this review, we focus on the potential role of CYP pathway in polycyclic aromatic hydrocarbons (PAH), important constituents of cigarette smoke, mediated HIV pathogenesis. More specifically, we will discuss the role of CYP1A1 and CYP1B1, which are the major PAH-activating CYP enzymes. Our results have shown that treatment with cigarette smoke condensate (CSC) increases viral replication in HIV-infected macrophages. CSC contains PAH, which are known to be activated by CYP1A1 and CYP1B1 into procarcinogens/toxic metabolites. The expression of these CYPs is regulated by aryl hydrocarbon receptors (AHR), the cellular target of PAH, and an important player in various diseases including cancer. We propose that PAH/AHR-mediated CYP pathway is a novel target to develop new interventions for HIV positive smokers.

Cytochrome P450 in Cancer Susceptibility and Treatment

Cytochrome 450 (CYP450) designates a group of enzymes abundant in smooth endoplasmic reticulum of hepatocytes and epithelial cells of small intestines. The main function of CYP450 is oxidative catalysis of various endogenous and exogenous substances. CYP450 are implicated in phase I metabolism of 80% of drugs currently in use, including anticancer drugs. They are also involved in synthesis of various hormones and influence hormone-related cancers. CYP450 genes are highly polymorphic and their variants play an important role in cancer risk and treatment. Association studies and meta-analyses have been performed to decipher the role of CYP450 polymorphisms in cancer susceptibility. Cancer treatment involves multimodal therapies and evaluation of CYP450 polymorphisms is necessary for pharmacogenetic assessment of anticancer therapy outcomes. In addition, CYP450 inhibitors are being evaluated for improved pharmacokinetics and oral formulation of several anticancer drugs.