eng Science and Education Publishing American Journal of Medicine Studies 2333-889X 2026 # The authors contribute equally to the experiment and manuscript writing-10-08 11 1 8 15 10.12691/ajms-11-1-2 AJMS20261112 article Viacheslav S 1 Jorge S. 1 Perez C. 2 Prajapati J. 2 Diaz A.J. 2 Wang T. 2 3 Department of Clinical Science Department of Biology, California State University Dominguez Hills, Carson, CA, USA Temozolomide (TMZ) is an alkylating agent central to glioblastoma therapy. Its activity is classically attributed to DNA methylation. Still, the reactive methyl-diazonium ion it generates is an electrophile with the potential to modify multiple cellular nucleophiles, and growing evidence points to a protein-level dimension of TMZ's action¡ªincluding changes in histone methylation and in the activity of repair-associated enzymes. Because this protein-level activity appears cell-type-specific, treating resistance as a purely DNA-level event may overlook a mechanistic layer relevant to why tumor types differ in their sensitivity to the drug. In this course-based undergraduate research experience (CURE) in Clinical Chemistry, we evaluated the cytotoxic response of three cancer cell lines ¡ª MCF-7 (estrogen receptor-positive breast cancer), MDA-MB-231 (triple-negative breast cancer), and U87 (glioblastoma) to TMZ. Cells were treated for 48 hours across a 50¨C200 µM concentration range, and the MTS assay quantified viability. The Wilcoxon signed-rank test was used to assess significance relative to untreated controls, and four-parameter logistic (4PL) regression was used to model dose-response and estimate IC?? values. Both breast cancer lines were sensitive to TMZ, with IC?? values of 59.0 µM (MCF-7) and 46.4 µM (MDA-MB-231), whereas U87 glioblastoma cells were markedly less responsive (nominal IC?? 213.7 µM). Because only half of the U87 dataset reached statistical significance, its IC?? is considered preliminary. The greater resistance of glioblastoma is consistent with MGMT-mediated repair of O6-methylguanine, but is best interpreted alongside a protein-level dimension of TMZ's action observed in our prior work: in glioma cells, increasing TMZ concentrations were associated with a decrease in histone methylation and a concentration-dependent, bimodal change in the activity of the histone demethylase LSD1 (KDM1A) ¡ª largely preserved at 100 µM or below and reduced at higher concentrations ¡ª an enzyme itself linked to DNA repair. Considered together, these DNA- and protein-level effects offer a fuller account of TMZ sensitivity than DNA damage alone. Beyond these biological findings, the project gave undergraduates hands-on training in experimental design, statistical analysis, and scientific communication, illustrating the value of embedding authentic research within the undergraduate curriculum. https://pubs.sciepub.com/ajms/11/1/2/ajms-11-1-2.pdf CUREs temozolomide cytotoxicity breast cancer and glioma