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Tuberous sclerosis associated with MDR1 gene expression and drug-resistant epilepsy
A Lazarowski1, G Sevlever, A Taratuto
1Clinical Chemistry Laboratory, FLENI, Instituto de Investigaciones Neurológicas Raul Carrea, Buenos Aires, Argentina.
Abstract:
Intractable seizures are the most common manifestation in severe cases of tuberous sclerosis. Multidrug resistance type 1 (MDR1) gene expression is directly linked to the resistance of tumor cells to chemotherapy as the major cause of treatment failure, but it has not been reported in tuberous sclerosis cells nor has the relationship between the MDR1 gene and antiepileptic drugs been described. A 4-month-old female is described with poorly controlled seizures secondary to tuberous sclerosis. The patient was treated with antiepileptic drugs, including phenytoin, phenobarbital, and lorazepam, without improvement of symptoms. Phenytoin blood levels were invariably subtherapeutic and ranged from 0.45 to 3.55 microg/mL, despite several consecutive intravenous loading doses. Surgical treatment with total resection of the brain lesions was performed as a last resort. Immunohistochemical analysis of the resected tissues revealed high levels of P-glycoprotein 170 expression, the product of the MDR1 gene. Both MDR1 gene expression and persistently low phenytoin levels likely share a common pathway liable to induce drug-resistant epilepsy.
Insights
Drug-resistant epilepsy in tuberous sclerosis may stem from high P-glycoprotein 170 expression. This finding links the multidrug resistance type 1 (MDR1) gene to poor antiepileptic drug efficacy in patients.
Area of Science:
- Neuroscience
- Genetics
- Pharmacology
Background:
- Tuberous sclerosis complex (TSC) frequently presents with intractable seizures, posing significant treatment challenges.
- Multidrug resistance type 1 (MDR1) gene expression is a known mechanism for chemotherapy resistance in cancer cells.
- The role of MDR1 in TSC-related epilepsy and its interaction with antiepileptic drugs (AEDs) remains largely unexplored.
Observation:
- A case study of a 4-month-old female with TSC and poorly controlled seizures is presented.
- The patient received multiple AEDs (phenytoin, phenobarbital, lorazepam) without symptom improvement.
- Despite aggressive treatment, phenytoin blood levels remained consistently subtherapeutic.
Findings:
- Immunohistochemical analysis of resected brain lesions revealed elevated P-glycoprotein 170 expression.
- P-glycoprotein 170 is the protein product of the MDR1 gene.
- High MDR1 gene expression and subtherapeutic phenytoin levels were observed concurrently.
Implications:
- Elevated MDR1 expression may contribute to drug-resistant epilepsy in tuberous sclerosis.
- This suggests a potential shared pathway between MDR1 gene expression and reduced AED effectiveness.
- Further research into MDR1's role could lead to novel therapeutic strategies for refractory epilepsy in TSC.