McKeague, M. | Search bioRxiv

bioRxiv2023

Single-nucleotide-resolution genomic maps of O6-methylguanine from the glioblastoma drug temozolomide

Temozolomide kills cancer cells by forming O6-methylguanine (O6-MeG), which leads to apoptosis due to mismatch-repair overload. However, O6-MeG repair by O6-methylguanine-DNA methyltransferase (MGMT) contributes to drug resistance. Characterizing genomic profiles of O6-MeG could elucidate how O6-MeG accumulation is influenced by repair, but there are no methods to map genomic locations of O6-MeG. Here, we developed an immunoprecipitation- and polymerase-stalling-based method, termed O6-MeG-seq, to locate O6-MeG across the whole genome at single-nucleotide resolution. We analyzed O6-MeG formation and repair with regards to sequence contexts and functional genomic regions in glioblastoma-derived cell lines and evaluated the impact of MGMT. O6-MeG signatures were highly similar to mutational signatures from patients previously treated with temozolomide. Furthermore, MGMT did not preferentially repair O6-MeG with respect to sequence context, chromatin state or gene expression level, however, may protect oncogenes from mutations. Finally, we found an MGMT-independent strand bias in O6-MeG accumulation in highly expressed genes, suggesting an additional transcription-associated contribution to its repair. These data provide high resolution insight on how O6-MeG formation and repair is impacted by genome structure and regulation. Further, O6-MeG-seq is expected to enable future studies of DNA modification signatures as diagnostic markers for addressing drug resistance and preventing secondary cancers. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=150 SRC="FIGDIR/small/571283v2_ufig1.gif" ALT="Figure 1"> View larger version (54K): org.highwire.dtl.DTLVardef@357353org.highwire.dtl.DTLVardef@12688b9org.highwire.dtl.DTLVardef@da3381org.highwire.dtl.DTLVardef@16b7e7e_HPS_FORMAT_FIGEXP M_FIG C_FIG

cancer biology↗

bioRxiv2021

Cancer Prognosis According to Parthanatos Features

For nearly 50 years, translational research studies aimed at improving chemotherapy-induced killing of cancer cells have focused on the induction of apoptosis. Here we show that a PARP-1-mediated programmed cell death mechanism "parthanatos" is associated with the successful, front-line treatment of a common cancer. Peripheral blood mononuclear cells (PBMCs) from healthy human donors (10 of 10 tested), as well as primary cancer cells from approximately 50% of acute myeloid leukemia (AML) patients (n = 18 of 39 tested, French-American-British (FAB) subtypes M4 and M5) exhibited two distinctive features of parthanatos upon treatment with a front-line drug combination of cytarabine and an anthracycline. Statistically significant improvements in survival rates were observed in the parthanatos positive versus parthanatos negative AML patient groups (HR = 0.22 - 0.38, p = 0.002 - 0.05). Near-median expression of PARP1 mRNA was associated with a 50% longer survival time (HR = 0.66, p = 0.01), and the poly [ADP-ribose] polymerase (PARP) inhibitor Olaparib exhibited antagonistic activities against ara-C and idarubicin in primary blood monocytes from healthy donors as well as primary cancer isolates from ~50% of AML patients. Together these results suggest that PARP activity is a prognostic biomarker for AML subtypes M4 and M5 and support the relevance of parthanatos in curative chemotherapy of AML. In BriefMessikommer and co-workers report that PARP-1-mediated programmed cell death is associated with successful, front-line treatment of acute myeloid leukemia (AML). HighlightsO_LIThe first-line cancer drug cytarabine (ara-C) induces parthanatos or apoptosis, depending on the specific AML cell line being treated. C_LIO_LIOCI-AML3 cells undergo parthanatos or apoptosis, depending on the specific drug being added. C_LIO_LIThe presence of two parthanatos features in primary cancer cells from AML patients (n = 18 of 39 tested) having French-American-British (FAB) subclassifications M4 or M5 is associated with four-fold improved survival (HR = 0.23, p = 0.01) following curative chemotherapy with ara-C and an anthracycline. C_LIO_LIThe poly [ADP-ribose] polymerase (PARP) inhibitor Olaparib exhibits antagonistic activities against ara-C and idarubicin in primary blood monocytes from healthy donors as well as primary cancer isolates from ~50% of AML patients. C_LIO_LINear-median expression of PARP1 mRNA is associated with a 50% increase in survival time (HR = 0.66, p = 0.01) of AML patients following chemotherapy with ara-C and idarubicin. C_LI GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=118 HEIGHT=200 SRC="FIGDIR/small/445484v1_ufig1.gif" ALT="Figure 1"> View larger version (42K): org.highwire.dtl.DTLVardef@af2a33org.highwire.dtl.DTLVardef@1fb8e1corg.highwire.dtl.DTLVardef@2eebf4org.highwire.dtl.DTLVardef@84eb8c_HPS_FORMAT_FIGEXP M_FIG C_FIG

cancer biology↗