Relationship between CYP3A activity and breast cancer susceptibility in Chinese Han women

A radiomics model development via the associations with genomics features in predicting axillary lymph node metastasis of breast cancer: a study based on a public database and single-centre verification

AIM

To evaluate the predictive performance of the radiomics model in predicting axillary lymph node (ALN) metastasis through the associations between radiomics features and genomic features in patients with breast cancer.

MATERIALS AND METHODS

Patients with breast cancer were enrolled retrospectively from a public database (111 patients as training group) and one hospital (15 patients as external validation group). The genomics features from transcriptome data and radiomics features from dynamic contrast-enhanced magnetic resonance imaging (MRI) were collected. Firstly, overlapping genes were identified using the Kyoto Encyclopedia of Genes and Genomes and differentially expressed gene analysis, while radiomics features were reduced using a data-driven method. Then, the associations between overlapping genes and retained radiomics features were assessed to obtain key pairs of radiomics-genomics features. Furthermore, the least absolute shrinkage and selection operator (LASSO) algorithm was used to detect the key-pairs features. Finally, radiomics and genomics models were constructed to predict ALN metastasis.

RESULTS

After using the hybrid data- and gene-driven selection method, key pairs of features were detected, which consisted of six radiomic features associated with four genomic features. The radiomics model exhibited comparable performance to the genomics model in predicting ALN metastasis (radiomic model: area under the curve [AUC] = 0.71, sensitivity = 77%, specificity = 56%; genomic model: AUC = 0.72, sensitivity = 85%, specificity = 74%). The four genomic features were enriched in six pathways and related to metabolism and human diseases.

CONCLUSION

The radiomics model established using the gene-driven hybrid selection method could predict ALN metastasis in breast cancer, which showed comparable performance to the genomics model.

Genetic Influence on Chemotherapy-Induced Nausea and Vomiting: A Narrative Review

Chemotherapy-induced nausea and vomiting (CINV) is a phenomenon common to patients being treated for a solid or hematologic malignancy. This adverse effect to cancer treatment persists in about half of all patients receiving highly emetogenic treatment, despite prophylaxis with serotonin (5-hydroxytryptamine-3 [5-HT3]) antagonists, steroids, and additional agents. Two broad categories increase risk for CINV: the emetogenic potential of chemotherapeutic drugs and patient-specific risk factors, such as younger age, female gender, low or no alcohol intake, and history of motion sickness or pregnancy-induced nausea. Despite these predictors for CINV, guidelines for prophylaxis continue to be based solely on the emetogenicity of agents administered. New strategies for CINV are unlikely until additional data emerge.
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Disruptive environmental chemicals and cellular mechanisms that confer resistance to cell death

Cell death is a process of dying within biological cells that are ceasing to function. This process is essential in regulating organism development, tissue homeostasis, and to eliminate cells in the body that are irreparably damaged. In general, dysfunction in normal cellular death is tightly linked to cancer progression. Specifically, the up-regulation of pro-survival factors, including oncogenic factors and antiapoptotic signaling pathways, and the down-regulation of pro-apoptotic factors, including tumor suppressive factors, confers resistance to cell death in tumor cells, which supports the emergence of a fully immortalized cellular phenotype. This review considers the potential relevance of ubiquitous environmental chemical exposures that have been shown to disrupt key pathways and mechanisms associated with this sort of dysfunction. Specifically, bisphenol A, chlorothalonil, dibutyl phthalate, dichlorvos, lindane, linuron, methoxychlor and oxyfluorfen are discussed as prototypical chemical disruptors; as their effects relate to resistance to cell death, as constituents within environmental mixtures and as potential contributors to environmental carcinogenesis.

A computational approach predicting CYP450 metabolism and estrogenic activity of an endocrine disrupting compound (PCB-30)

Endocrine disrupting chemicals influence growth and development through interactions with the hormone system, often through binding to hormone receptors such as the estrogen receptor. Computational methods can predict endocrine disrupting chemical activity of unmodified compounds, but approaches predicting activity following metabolism are lacking. The present study uses a well-known environmental contaminant, PCB-30 (2,4,6-trichlorobiphenyl), as a prototype endocrine disrupting chemical and integrates predictive (computational) and experimental methods to determine its metabolic transformation by cytochrome P450 3A4 (CYP3A4) and cytochrome P450 2D6 (CYP2D6) into estrogenic byproducts. Computational predictions suggest that hydroxylation of PCB-30 occurs at the 3- or 4-phenol positions and leads to metabolites that bind more strongly than the parent molecule to the human estrogen receptor alpha (hER-α). Gas chromatography-mass spectrometry experiments confirmed that the primary metabolite for CYP3A4 and CYP2D6 is 4-hydroxy-PCB-30, and the secondary metabolite is 3-hydroxy-PCB-30. Cell-based bioassays (bioluminescent yeast expressing hER-α) confirmed that hydroxylated metabolites are more estrogenic than PCB-30. These experimental results support the applied model's ability to predict the metabolic and estrogenic fate of PCB-30, which could be used to identify other endocrine disrupting chemicals involved in similar pathways.

Knockout of mouse Cyp3a gene enhances synthesis of cholesterol and bile acid in the liver

Here, we studied the effects of cytochrome P450 (CYP)3A deficiency on the mRNA expression of genes encoding regulators of hepatic cholesterol levels using Cyp3a-knockout (Cyp3a(-/-)) mice. The mRNA expression levels of genes encoding enzymes involved in cholesterol biosynthesis in the livers of Cyp3a(-/-) mice were higher than those of wild-type (WT) mice. Nuclear levels of sterol regulatory element-binding protein-2 (SREBP-2), which enhances cholesterol biosynthesis, were also higher in the livers of Cyp3a(-/-) mice. Binding of SREBP-2 to the Hmgcs1 gene promoter was more abundant in the livers of Cyp3a(-/-) mice. These results suggest that deficiency of CYP3A enzymes enhances transcription of genes encoding enzymes involved in cholesterol biosynthesis via activation of SREBP-2. On the other hand, hepatic cholesterol levels in Cyp3a(-/-) mice were 20% lower than those in WT mice. The mRNA expression levels of genes encoding enzymes involved in bile acid synthesis, plasma levels of 7α-hydroxy-4-cholesten-3-one and hepatic levels of total bile acid were significantly higher in Cyp3a(-/-) mice than in WT mice. These findings suggest that reduction of hepatic total cholesterol in Cyp3a(-/-) mice would be the consequence of enhanced bile acid synthesis. Therefore, CYP3A enzymes appear to play roles in the synthesis of cholesterol and bile acid in vivo.

Prediction of CYP3A4 enzyme activity using haplotype tag SNPs in African Americans

The CYP3A locus encodes hepatic enzymes that metabolize many clinically used drugs. However, there is marked interindividual variability in enzyme expression and clearance of drugs metabolized by these enzymes. We utilized comparative genomics and computational prediction of transcriptional factor binding sites to evaluate regions within CYP3A that were most likely to contribute to this variation. We then used a haplotype tagging single-nucleotide polymorphisms (htSNPs) approach to evaluate the entire locus with the fewest number of maximally informative SNPs. We investigated the association between these htSNPs and in vivo CYP3A enzyme activity using a single-point IV midazolam clearance assay. We found associations between the midazolam phenotype and age, diagnosis of hypertension and one htSNP (141689) located upstream of CYP3A4. 141689 lies near the xenobiotic responsive enhancer module (XREM) regulatory region of CYP3A4. Cell-based studies show increased transcriptional activation with the minor allele at 141689, in agreement with the in vivo association study findings. This study marks the first systematic evaluation of coding and noncoding variation that may contribute to CYP3A phenotypic variability.

Pregnane X Receptor-Dependent Induction of the CYP3A4 Gene by o,p′-1,1,1,-Trichloro-2,2-Bis (p-Chlorophenyl)ethane

CYP3A4, the predominant cytochrome P450 (P450) expressed in human liver and intestine, contributes to the metabolism of approximately half the drugs in clinical use today. CYP3A4 catalyzes the 6beta-hydroxylation of a number of steroid hormones and is involved in the bioactivation of environmental procarcinogens. The expression of CYP3A4 is affected by several stimuli, including environmental factors such as insecticides and pesticides. The o,p'-1,1,1,-trichloro-2,2-bis (p-chlorophenyl)ethane (DDT) isomer of DDT comprises approximately 20% of technical grade DDT, which is an organochloride pesticide. We have recently shown that o,p'-DDT exposure increases CYP3A4 mRNA levels in HepG2 cells. To determine the mechanism by which o,p'-DDT induces CYP3A4 expression, transactivation and electrophoretic mobility shift assays were carried out, revealing that o,p'-DDT activates the CYP3A4 gene promoter through the pregnane X receptor (PXR). CYP3A4 gene promoter activation resulted in both an increase in CYP3A4 mRNA levels and an increase in the total CYP3A4 activity in HepG2 cells. We also observed induction of CYP3A4 and mouse Cyp3a11 mRNA in the intestine of CYP3A4-transgenic mice after exposure to 1 mg/kg o,p'-DDT. At higher doses, a decrease of CYP3A4 inducibility was observed together with an increase in levels of interleukin 6 mRNA, a proinflammatory cytokine that strongly represses CYP3A4 transcription. The present study indicates that regulation of other genes under PXR control may be altered by o,p'-DDT exposure.

CAR and PXR: xenosensors of endocrine disrupters?

The pregnane X-receptor (PXR) and the constitutive androstane receptor (CAR) are orphan nuclear receptors activated by a variety of ligands. Currently it remains uncertain whether these receptors have a high-affinity ligand or instead function as more generalized steroid/xenobiotic sensors. Both receptors are important regulators of several steroid and xenobiotic detoxification enzymes and transporters (phases I-III) in the liver and intestine and thus are important regulators of adaptation to chemical stress. The detoxification proteins induced are responsible for the metabolism, deactivation and transport of bile acids, thyroid and steroid hormones, numerous environmental chemicals, and several drugs. PXR and CAR received their names because of steroid ligands that activate and inhibit their transcriptional activity, respectively. Interestingly, some steroids and steroid mimics activate one or both receptors, including several endocrine disrupting chemicals. Environmental estrogens, such as the pesticides methoxychlor, endosulfan, dieldrin, DDT, and the plasticizer nonylphenol activate either PXR or both PXR and CAR. Because PXR and CAR are activated by numerous steroids and endocrine disrupters, it appears that these receptors protect the integrity of the endocrine system. They recognize an increase in steroid-like chemicals and, in turn, induce detoxification. Furthermore, PXR and CAR induce enzymes, such as the CYP2B and CYP3A family members, responsible for the metabolism of steroid and thyroid hormones and this may alter their normal physiological function. This review summarizes the available data on the activity of endocrine disrupters and endocrine active chemicals on PXR and CAR, examines the role of PXR and CAR in protection from these chemicals, and evaluates potential adverse physiological consequences of PXR and CAR activation.