Background/Objectives: Rosmarinic acid (RA) is a naturally occurring polyphenolic compound with promising anticancer activity; however, its potential to enhance the therapeutic efficacy of doxorubicin (DOX) against triple-negative breast cancer (TNBC) has not been comprehensively characterised. This study investigated the pharmacological interaction and associated cellular responses of RA combined with DOX in MDA-MB-231 breast cancer cells, while including HaCaT human keratinocytes as a non-malignant, non-mammary reference model for comparative cytotoxicity assessment. Methods: Cell viability was assessed using the MTT assay, and pharmacological interactions were evaluated using Chou–Talalay combination index (CI) and dose reduction index (DRI) analyses. Intracellular oxidative activity was evaluated using DCFH-DA fluorescence analyses together with N-acetyl-L-cysteine (NAC) modulation experiments. Apoptosis, cell-cycle distribution, mitochondrial membrane potential (JC-1), Caspase-9 immunocytochemistry, nuclear morphology (NucBlue staining), apoptosis- and proliferation-related gene expression (RT-qPCR; BAX, BCL2, CASP3, CASP9, TP53, CDKN1A, MKI67, and PCNA), and bioinformatic pathway analyses were performed to characterise cellular and molecular responses associated with the combined treatment. Results: After 48 h, RA exhibited IC50 values of 188.4 ± 4.2 µM in MDA-MB-231 cells and 146.6 ± 6.8 µM in HaCaT cells, while DOX showed IC50 values of 1.2 ± 0.08 µM and 2.6 ± 0.15 µM, respectively. The Chou–Talalay analysis demonstrated synergistic interactions in MDA-MB-231 cells, with CI values of 0.86, 0.72, and 0.64 at the effect levels of IC25, IC50, and IC75, respectively; the model-derived DOX DRI value at Fa = 0.50 was 1.8. Combination treatment markedly increased intracellular DCFH-DA fluorescence, whereas NAC pretreatment attenuated this signal and partially restored cell viability, supporting a contributory role of intracellular oxidative stress in treatment-associated cytotoxicity. Increased intracellular oxidative activity coincided with mitochondrial membrane depolarisation, increased apoptotic cell death, accumulation of cells in the sub-G1 phase, enhanced Caspase-9 immunoreactivity, and pronounced apoptotic nuclear alterations. RT-qPCR analysis demonstrated significant upregulation of BAX, CASP3, CASP9, and TP53, together with downregulation of BCL2, MKI67, and PCNA, resulting in a marked reduction in the BCL2/BAX mRNA expression ratio. A modest but non-significant increase in CDKN1A expression was also observed. Bioinformatic analyses further identified predicted associations with mitochondrial apoptosis and p53-associated signalling pathways. Conclusions: The RA + DOX combination showed synergistic cytotoxic activity in MDA-MB-231 cells, accompanied by increased intracellular oxidative activity, mitochondrial membrane depolarisation, apoptosis, cell-cycle perturbation, and changes in proliferation-related gene expression. These findings indicate associated cellular responses but do not establish a ROS-dependent mitochondrial apoptotic mechanism. The findings provide an exploratory in vitro basis for further investigation of the RA + DOX combination in additional TNBC models, non-malignant mammary epithelial cells, and appropriate in vivo systems.
Coşkun Orhaner, M. Tuncer, İ. Özdemir· Biomedicines· 0 citations
Rosmarinic acid (RA), a naturally occurring polyphenolic compound, has attracted increasing attention because of its potential anticancer activity and capacity to modulate oxidative stress-associated signaling pathways. In the present study, the cytotoxic, apoptotic, and antiproliferative effects of RA, alone or in combination with gemcitabine (Gem), were investigated in OVCAR3 ovarian cancer cells and HaCaT keratinocytes using integrated two-dimensional and three-dimensional (3D) experimental models. Cell viability assays demonstrated dose- and time-dependent growth inhibition following RA and Gem treatment, while combination index (CI) analysis revealed synergistic cytotoxic activity in OVCAR3 cells. Flow cytometric analyses showed that combined treatment markedly increased apoptotic cell populations and altered cell cycle progression through enhanced S-phase and G2/M accumulation. Intracellular reactive oxygen species (ROS) levels were significantly elevated following combination treatment, and N-acetyl-L-cysteine (NAC) pretreatment partially attenuated both ROS accumulation and cytotoxicity, indicating a functional contribution of oxidative stress to the observed antitumor response. RT-qPCR analyses demonstrated increased expression of proapoptotic genes (BAX, CASP3, and CASP9) together with suppression of BCL2, MKI67, and CDK4 expression, while immunocytochemical analyses supported enhanced caspase-3 activation at the protein level. In 3D OVCAR3 tumor spheroids, the RA + Gem combination significantly reduced spheroid viability, disrupted spheroid architecture, and increased dead-cell accumulation compared with single-agent treatments. Collectively, these findings suggest that RA may enhance the anticancer activity of Gem in ovarian cancer cells through mechanisms associated with oxidative stress, apoptosis, and proliferation-related signaling pathways under both monolayer and 3D culture conditions.
Coşkun Orhaner, M. Tuncer, İ. Özdemir· International Journal of Mol...· 0 citations
Background: Drug resistance and treatment-associated toxicity remain major limitations of conventional chemotherapy for triple-negative breast cancer (TNBC). Thymoquinone (TQ), a bioactive phytochemical derived from Nigella sativa, has demonstrated anticancer properties and may enhance the therapeutic efficacy of docetaxel (DTX) through complementary molecular mechanisms. Objective: To investigate whether TQ potentiates the antitumor activity of DTX in MDA-MB-231 TNBC cells by affecting apoptosis, oxidative stress, wound closure, and PI3K/AKT pathway-related gene expression. Methods: MDA-MB-231 TNBC cells and HaCaT keratinocytes were treated with TQ, DTX, or their combination. Cell viability was determined using the MTT assay, and drug interactions were evaluated by the Chou–Talalay combination index (CI) method. Apoptosis, intracellular reactive oxygen species (ROS) production, ROS rescue experiments using N-acetyl-L-cysteine (NAC), caspase-9 expression, wound closure, and gene-expression changes were assessed using Annexin V/PI flow cytometry, DCFH-DA-based flow cytometric and fluorescence analyses, immunocytochemistry, wound-healing assay, and quantitative real-time PCR (qRT-PCR), respectively. Bioinformatic analyses were performed to identify signaling pathways associated with the observed molecular alterations. Results: The TQ + DTX combination demonstrated synergistic cytotoxicity and significantly increased apoptotic cell death compared with either monotherapy. Combination treatment markedly enhanced intracellular ROS accumulation, whereas NAC pretreatment significantly attenuated ROS generation and partially reversed the cytotoxic and pro-apoptotic effects, suggesting the involvement of ROS in the observed antitumor effects. Caspase-9 immunoreactivity was markedly increased following combination treatment, suggesting the involvement of the intrinsic apoptotic pathway. Furthermore, the combination significantly suppressed wound closure and downregulated BCL2, PIK3CA, and AKT1 while upregulating BAX, CASP9, and PTEN. Bioinformatic analyses identified apoptosis, p53, PI3K/AKT, mTOR, and MAPK signaling as the principal pathways potentially associated with the observed gene expression changes. Conclusions: TQ potentiates the antitumor activity of DTX, with the involvement of oxidative stress, apoptotic signaling, suppression of wound closure, and regulation of PI3K/AKT pathway-related gene expression in TNBC cells. These findings provide evidence supporting further preclinical investigation of the TQ + DTX combination as a promising therapeutic strategy for triple-negative breast cancer.
Aylin Orhaner, M. Tuncer, İ. Özdemir· Pharmaceuticals· 0 citations
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