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Repurposing loratadine to induce ferroptosis and overcome multidrug resistance: preclinical evidence in KB-V-1 cells
Nicholas Cook1, Xin Li1, Nathan J Bowen1
1Center for Cancer Research and Therapeutic Development and Department of Biological Sciences, Clark Atlanta University, Atlanta, GA, United States.
Background:
MDR1/P-glycoprotein-mediated multidrug resistance (MDR) limits chemotherapy efficacy across many cancers. Ferroptosis, an iron-dependent regulated cell death driven by lipid peroxidation, offers a potential strategy to bypass MDR. We investigated whether loratadine, an FDA-approved antihistamine, induces ferroptosis and overcomes chemoresistance in MDR1-overexpressing KB-V-1 cells.
Methods:
Cytotoxicity was evaluated using the CCK-8 assay in multidrug-resistant KB-V-1 cells and chemosensitive KB-3-1 cells. Ferroptosis was verified using specific inhibitors, including ferrostatin-1, liproxstatin-1, and deferoxamine, and compared with the pan-caspase inhibitor Z-VAD-FMK to exclude apoptosis. Hallmarks of ferroptosis (cystine uptake, intracellular glutathione levels, labile iron pool, and lipid peroxidation) were quantitatively assessed. Transcriptomic alterations were analyzed by RNA sequencing (RNA-seq) and further validated by quantitative real-time PCR (qRT-PCR) and Western blot analyses. In vivo antitumor efficacy was examined in a KB-V-1 xenograft model following treatment with loratadine (20 mg/kg, intraperitoneal), paclitaxel, or their combination.
Results:
Loratadine selectively inhibited KB-V-1 viability (IC50 = 2.0 µM) while sparing KB-3-1 cells (IC50 =48.45 µM). Cell death was effectively rescued by ferroptosis inhibitors, confirming ferroptosis as the primary mechanism. Loratadine suppressed cystine uptake, depleted glutathione, elevated labile iron, and promoted lipid peroxidation comparably to erastin. RNA-seq identified 1,861 differentially expressed genes enriched in the PERK-eIF2α-ATF4 stress axis; upregulation of ATF4, CHAC1, DDIT4, and DDIT3 was confirmed by qRT-PCR and/or Western blot analyses. Loratadine also reduced MDR1/P-glycoprotein expression. In vivo, loratadine suppressed tumor growth and enhanced paclitaxel efficacy without systemic toxicity.
Conclusion:
Loratadine induces ferroptosis in MDR1-overexpressing cells via cystine uptake inhibition, glutathione depletion, and PERK-eIF2α-ATF4 activation, while concurrently downregulating MDR1/P-glycoprotein. These findings support loratadine as a clinically actionable repurposing candidate for ferroptosis-based, resistance-directed cancer therapy.
Insights
Loratadine, an antihistamine, effectively induces ferroptosis in multidrug-resistant cancer cells by inhibiting cystine uptake and activating stress pathways. This repurposing strategy overcomes chemoresistance and enhances chemotherapy efficacy with minimal toxicity.
Area of Science:
- Cancer Biology
- Drug Discovery and Development
- Cell Death Mechanisms
Background:
- Multidrug resistance (MDR) mediated by MDR1/P-glycoprotein significantly limits the effectiveness of chemotherapy in various cancers.
- Ferroptosis, a form of regulated cell death driven by lipid peroxidation, presents a promising avenue to circumvent MDR.
- This study explores the potential of loratadine, an FDA-approved antihistamine, to induce ferroptosis and overcome chemoresistance in MDR1-overexpressing cancer cells.
Purpose of the Study:
- To investigate whether loratadine can induce ferroptosis in multidrug-resistant cancer cells.
- To determine if loratadine can overcome chemoresistance mediated by MDR1/P-glycoprotein.
- To elucidate the underlying molecular mechanisms of loratadine-induced ferroptosis and its therapeutic potential in vivo.
Main Methods:
- Cytotoxicity was assessed using the CCK-8 assay in multidrug-resistant (KB-V-1) and chemosensitive (KB-3-1) cell lines.
- Ferroptosis was confirmed using specific inhibitors (ferrostatin-1, liproxstatin-1, deferoxamine) and differentiated from apoptosis using Z-VAD-FMK.
- Key ferroptosis hallmarks, transcriptomic changes (RNA-seq, qRT-PCR, Western blot), and in vivo antitumor efficacy in a xenograft model were evaluated.
Main Results:
- Loratadine selectively killed MDR1-overexpressing KB-V-1 cells (IC50 = 2.0 µM) while sparing chemosensitive KB-3-1 cells (IC50 = 48.45 µM).
- Ferroptosis inhibitors rescued cell viability, confirming ferroptosis as the mechanism; loratadine suppressed cystine uptake, depleted glutathione, and increased lipid peroxidation.
- RNA-seq revealed activation of the PERK-eIF2α-ATF4 stress axis, and loratadine reduced MDR1/P-glycoprotein expression, enhancing paclitaxel efficacy in vivo without systemic toxicity.
Conclusions:
- Loratadine induces ferroptosis in MDR1-overexpressing cells by inhibiting cystine uptake, depleting glutathione, and activating the PERK-eIF2α-ATF4 pathway.
- Loratadine concurrently downregulates MDR1/P-glycoprotein, suggesting a dual mechanism for overcoming multidrug resistance.
- Loratadine is a promising candidate for repurposing as a ferroptosis-inducing agent in resistance-directed cancer therapy.
