Pharmacokinetic Estimation Models-based Approach to Predict Clinical Implications for CYP Induction by Calcitriol in Human Cryopreserved Hepatocytes and HepaRG Cells

Dissection of an impact of VDR and RXRA on the genomic activity of 1,25(OH)2D3 in A431 squamous cell carcinoma

BACKGROUND

Human skin is the natural source, place of metabolism, and target for vitamin D3. The classical active form of vitamin D3, 1,25(OH)2D3, expresses pluripotent properties and is intensively studied in cancer prevention and therapy. To define the specific role of vitamin D3 receptor (VDR) and its co-receptor retinoid X receptor alpha (RXRA) in genomic regulation, VDR or RXRA genes were silenced in the squamous cell carcinoma cell line A431 and treated with 1,25(OH)2D3 at long incubation time points 24 h/72 h. Extending the incubation time of A431 WT (wild-type) cells with 1,25(OH)2D3 resulted in a two-fold increase in DEGs (differentially expressed genes) and a change in the amount of downregulated from 37% to 53%. VDR knockout led to a complete loss of 1,25(OH)2D3-induced genome-wide gene regulation at 24 h time point, but after 72 h, 20 DEGs were found, of which 75% were downregulated, and most of them belonged to the gene ontology group "immune response". This may indicate the existence of an alternative, secondary response to 1,25(OH)2D3. In contrast, treatment of A431 ΔRXRA cells with 1,25(OH)2D3 for 24 h only partially affected DEGs, suggesting RXRA-independent regulation. Interestingly, overexpression of classic 1,25(OH)2D3 targets, like CYP24A1 (family 24 of subfamily A of cytochrome P450 member 1) or CAMP (cathelicidin antimicrobial peptide) was found to be RXRA-independent. Also, immunofluorescence staining of A431 WT cells revealed partial VDR/RXRA colocalization after 24 h and 72 h 1,25(OH)2D3 treatment. Comparison of transcriptome changes induced by 1,25(OH)2D3 in normal keratinocytes vs. cancer cells showed high cell type specific expression pattern with only a few genes commonly regulated by 1,25(OH)2D3. Activation of the genomic pathway at least partially reversed the expression of cancer-related genes, forming a basis for anti-cancer activates of 1,25(OH)2D3. In summary, VDR or RXRA independent genomic activities of 1,25(OH)2D3 suggest the involvement of alternative factors, opening new challenges in this field.

Involvement of CYP3A4 and MDR1 in altered metabolism and transport of indinavir in 1,25(OH)2D3-treated Caco-2 cells

Altered drug concentrations may induce unexpected toxicity or treatment failure; thus, understanding the factors that alter the pharmacokinetic profiles of drugs is crucial for optimal disease treatment. Vitamin D receptor (VDR), a nuclear receptor, regulates the expression of cytochrome P450 3A4 (CYP3A4) and multidrug resistance protein 1 (MDR1), which are crucial determinants of drug pharmacokinetics. In this study, we investigated the effects of 1α,25-dihydroxyvitamin D₃ [1,25(OH)₂D₃], a VDR ligand, on the metabolism, transport, and pharmacokinetics of indinavir, a dual substrate of CYP3A4 and MDR1. 1,25(OH)₂D₃ treatment for three days upregulated the expression levels of CYP3A4 and MDR1 in Caco-2 cells and consequently led to an increase in the level of a metabolite formed via CYP3A4 (indinavir M6) and the efflux ratio of indinavir in transport study. The increase in the metabolic reaction was also confirmed through a metabolism assay performed using the lysate of 1,25(OH)₂D₃-treated Caco-2 cells. In the Ussing chamber study conducted with the rat intestine, 1,25(OH)₂D₃ treatment did not alter the transport of indinavir into the basolateral side but increased indinavir M6 formation. Similarly, plasma levels of the metabolite increased in 1,25(OH)₂D₃-treated rats; however, systemic exposure to indinavir led to insignificant alterations. Considering the overlapping substrate specificities for CYP3A4 and MDR1 and their significant roles in drug pharmacokinetics, VDR may play an important role in drug interactions of CYP3A4 and MDR1 substrates for accessing more effective and safe disease treatments.

Comparative pharmacokinetic study of bicalutamide administration alone and in combination with vitamin D in rats

Bicalutamide (BCL) has been approved for treatment of advanced prostate cancer (Pca), and vitamin D is inevitably used in combination with BCL in Pca patients for skeletal or anti-tumor strategies. Therefore, it is necessary to study the effect of vitamin D application on the pharmacokinetics of BCL.

We developed and validated a specific, sensitive and rapid UHPLC–MS/MS method to investigate the pharmacokinetic behaviours of BCL in rat plasma with and without the combined use of vitamin D. Plasma samples were extracted by protein precipitation with ether/dichloromethane (2:1 v/v), and the analytes were separated by a Kinetex Biphenyl 100A column (2.1 × 100 mm, 2.6 μm) with a mobile phase composed of 0.5 mM ammonium acetate (PH 6.5) in water (A) and acetonitrile (B) in a ratio of A:B = 35:65 (v/v). Analysis of the ions was run in the multiple reactions monitoring (MRM) mode. The linear range of BCL was 5–2000 ng mL−1. The intra- and inter-day precision were less than 14%, and the accuracy was in the range of 94.4–107.1%. The mean extraction recoveries, matrix effects and stabilities were acceptable for this method. The validated method was successfully applied to evaluate the pharmacokinetic behaviours of BCL in rat plasma. The results demonstrated that the pharmacokinetic property of BCL is significantly affected by combined use of vitamin D, which might help provide useful evidence for the clinical therapy and further pharmacokinetic study.

TNBC: Potential Targeting of Multiple Receptors for a Therapeutic Breakthrough, Nanomedicine, and Immunotherapy

Triple-negative breast cancer (TNBC) is a heterogeneous, recurring cancer associated with a high rate of metastasis, poor prognosis, and lack of therapeutic targets. Although target-based therapeutic options are approved for other cancers, only limited therapeutic options are available for TNBC. Cell signaling and receptor-specific targets are reportedly effective in patients with TNBC under specific clinical conditions. However, most of these cancers are unresponsive, and there is a requirement for more effective treatment modalities. Further, there is a lack of effective biomarkers that can distinguish TNBC from other BC subtypes. ER, PR, and HER2 help identify TNBC and are widely used to identify patients who are most likely to respond to diverse therapeutic strategies. In this review, we discuss the possible treatment options for TNBC based on its inherent subtype receptors and pathways, such as p53 signaling, AKT signaling, cell cycle regulation, DNA damage, and programmed cell death, which play essential roles at multiple stages of TNBC development. We focus on poly-ADP ribose polymerase 1, androgen receptor, vascular endothelial growth factor receptor, and epidermal growth factor receptor as well as the application of nanomedicine and immunotherapy in TNBC and discuss their potential applications in drug development for TNBC.