Thymoquinone regulates gene expression levels in the estrogen metabolic and interferon pathways in MCF7 breast cancer cells

New drugs are continuously being developed for the treatment of patients with estrogen receptor-positive breast cancer. Thymoquinone is one of the drugs that exhibits anticancer characteristics based on in vivo and in vitro models. This study further investigates the effects of thymoquinone on human gene expression using cDNA microarray technology. The quantification of RNA samples was carried out using an Agilent 2100 Bioanalyser to determine the RNA integrity number (RIN). The Agilent Low Input Quick Amplification Labelling kit was used to generate cRNA in two-color microarray analysis. Samples with RIN >9.0 were used in this study. The universal human reference RNA was used as the common reference. The samples were labelled with cyanine-3 (cye-3) CTP dye and the universal human reference was labelled with cyanine-5 (cye-5) CTP dye. cRNA was purified with the RNeasy Plus Mini kit and quantified using a NanoDrop 2000c spectrophotometer. The arrays were scanned data analysed using Feature Extraction and GeneSpring software. Two-step qRT-PCR was selected to determine the relative gene expression using the High Capacity RNA-to-cDNA kit. The results from Gene Ontology (GO) analysis, indicated that 8 GO terms were related to biological processes (84%) and molecular functions (16%). A total of 577 entities showed >2-fold change in expression. Of these entities, 45.2% showed an upregulation and 54.7% showed a downregulation in expression. The interpretation of single experiment analysis (SEA) revealed that the cytochrome P450, family 1, subfamily A, polypeptide 1 (CYP1A1) and UDP glucuronosyltransferase 1 family, polypeptide A8 (UGT1A8) genes in the estrogen metabolic pathway were downregulated significantly by 43- and 11-fold, respectively. The solute carrier family 7 (anionic amino acid transporter light chain, xc-system), member 11 (SLC7A11) gene in the interferon pathway, reported to be involved in the development of chemoresistance, was downregulated by 15-fold. The interferon-induced protein with tetratricopeptide repeats (IFIT)1, IFIT2, IFIT3, interferon, α-inducible protein (IFI)6 (also known as G1P3), interferon regulatory factor 9 (IRF9, ISGF3), 2′–5′-oligoadenylate synthetase 1, 40/46 kDa (OAS1) and signal transducer and activator of transcription 1 (STAT1) genes all showed changes in expression following treatment with thymoquinone. The caspase 10, apoptosis-related cysteine peptidase (CASP10) gene was activated and the protein tyrosine phosphatase, receptor type, R (PTPRR) and myocyte enhancer factor 2C (MEF2C) genes were upregulated in the classical MAPK and p38 MAPK pathways. These findings indicate that thymquinone targets specific genes in the estrogen metabolic and interferon pathways.