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­PNAS Papers on AML Tumorigenesis, Pancreatic Cancer Inhibition, Adult T-Cell Leukemia/Lymphoma

Editor's Note: Some of the articles described below are not yet available at the PNAS site but are scheduled to be posted this week.

In a study scheduled to appear in PNAS this week, a University of North Carolina-Chapel Hill-led team explores stemness pathway contributions to tumorigenicity in aggressive forms of acute myeloid leukemia (AML) marked by MLL alterations or NUP98 andNSD1 gene rearrangements. Using RNA sequencing, chromatin immunoprecipitation-sequencing, and an epigenetic profiling assay called "cleavage under targets & release," the researchers saw signs that chromatin associations help the lysine demethylase Kdm5b suppresses stem cell-like features in AML — a process that is itself repressed by polycomb repressive complex 2 (PRC2) and PRC2's H3K27 methylase enzyme activity. These and other findings suggest that the "AML-suppressing role of Kdm5b is not dependent on its intrinsic demethylase activity but requires its scaffold and/or chromatin association functions," the authors report, arguing that such results may inform future therapeutic strategies.

German researchers describe synthetic lethal ties between RUNX1 transcription factor inhibition and higher-than-usual expression of the pro-apoptosis protein NOXA in pancreatic ductal adenocarcinoma (PDAC). With the help of a drug screen — together with RNA sequencing, ChIP-seq, ATAC-seq, CRISPR-based gene editing, and other approaches — the team found that PDAC growth could be curbed in mouse models of the disease and in patient-derived organoids using a compound that inhibits RUNX1. RUNX1 inhibition, in turn, appeared to boost NOXA-related apoptosis through epigenetic changes, including a shift in histone features found in the promoter of the NOXA-coding gene. "Our study unravels a function of the transcription factor RUNX1 in apoptosis regulation in PDAC," they write. "We show that pharmacological RUNX1 inhibition in PDAC is feasible and leads to NOXA-dependent apoptosis."

A team from China and Japan digs into the oncogenic role that the Hippo/Yap pathway plays in some virus-induced malignancies, particularly adult T-cell leukemia/lymphoma (ATL), an aggressive T-cell cancer linked to human T-cell leukemia virus type 1 (HTLV-1) infection. With gene expression and other analyses in peripheral blood mononuclear cells from 14 individuals with or without ATL, along with follow-up cell line and mouse xenograft model experiments, the investigators saw lower-than-usual levels of the Hippo tumor suppressor pathway and enhanced YAP transcription and NF-kappa-B-related YAP activation in the HTLV-1-infected cells, in part due to the activity of a viral protein called Tax. "[W]e have shown that HTLV-1 infection dysregulates the Hippo signaling pathway and induces the activation of YAP through two mechanisms: Tax-mediated stimulation of YAP gene transcription and TAX-mediated NF-kappa-B activation of the YAP protein," they write, adding that "HTLV-1 may take advantage of these mechanisms to allow infected cells to proliferate."

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