CYP2B6 downregulation by cell-penetrating dominant-negative activating transcription factor 5 peptide in glioblastoma cells

Pharmacogenomics has emerged as a vital field within precision medicine and forensics, focusing on how an individual's genome affects their response to drugs. This field is essential in enhancing treatment efficacy and minimizing side effects, particularly for cancer patients with gliomas, who often face narrow therapeutic windows for anticancer agents and have a limited Food and Drug Administration-approved treatment option. Among the cytochrome P450 enzyme superfamily, CYP2B6 metabolizes drugs such as cyclophosphamide, efavirenz, methadone, and ecstasy. Genetic variation in P450 genes influences individual's drug-metabolizing capacity, making it crucial to understand CYP2B6 and its regulation to ensure the effectiveness and safety of drug therapies and determine the cause of death in drug-related cases. Previous studies have shown that activating transcription factor 5 (ATF5), a basic leucine zipper transcription factor, transactivates CYP2B6 in liver cells. Additionally, a cell-penetrating dominant-negative ATF5 (CP-DN-ATF5) peptide was developed and successfully interfered with the ATF5-mediated stabilization of antiapoptotic proteins. Our study aimed to establish the ATF5-mediated regulation of CYP2B6 in glioblastoma cells and to determine whether CP-DN-ATF5 could also promote the downregulation of CYP2B6. We used the Tat cell-penetrating peptide from HIV-1 transactivator of transcription (TAT) form, which was N-terminally fused with DN-ATF5 (TAT-CP-DN-ATF5), for our investigation. We found that ATF5 regulates CYP2B6, and the TAT-CP-DN-ATF5 peptide effectively downregulates CYP2B6 protein levels in certain glioblastoma cell lines, LN229 and GBM5. These findings suggest the potential for targeting CYP2B6 with TAT-CP-DN-ATF5 to slow drug metabolism, allowing for personalized dosing and coadministration strategies to improve treatment efficiency and reduce side effects. SIGNIFICANCE STATEMENT: The study found that the transcription factor activating transcription factor 5 regulates CYP2B6 expression in glioblastoma cell lines. Introducing a transactivator of transcription-fused cell-penetrating dominant-negative activating transcription factor 5 peptide downregulates CYP2B6 protein expression, suggesting its potential for personalized dosing strategies by targeting CYP2B6.