Regulation of the PML tumor suppressor in drug-induced senescence of human normal and cancer cells by JAK/STAT-mediated signaling

Abstract

the promyelocytic leukemia protein (pML) tumor suppressor is upregulated in several forms of cellular senescence, however the mechanism of its induction is elusive. Here we show that genotoxic drugs that induce senescence, such as 5-bromo-2'deoxyuridine (BrdU), thymidine (tMD), distamycin A (DMA), aphidicolin (ApH), etoposide (et) and camptothecin (Cpt) all evoke expansion of pML nuclear compartment and its association with persistent DNA lesions in several human cancer cell lines and normal diploid fibroblasts. this phenomenon was accompanied by elevation of pML transcripts after treatment with BrdU, tMD, DMA and Cpt. Chemical inhibition of all JAK kinases and RNAi-mediated knock-down of JAK1 suppressed pML expression, implicating JAK/StAt-mediated signaling in regulation of the pML gene. As pML protein stability remained unchanged after drug treatment, decreased protein turnover was unlikely to explain the senescence-associated increased abundance of pML. Furthermore, binding activity of Interferon Stimulated Response element (ISRe) within the pML gene promoter, and suppression of reporter gene activity after deletion of ISRe from the pML promoter region suggested that drug-induced pML transcription is controlled via transcription factors interacting with this element. Collectively, our data show that upregulation of the pML tumor suppressor in cellular senescence triggered by diverse drugs including clinically used anti-cancer chemotherapeutics relies on stimulation of pML transcription by JAK/StAt-mediated signaling, possibly evoked by the autocrine/paracrine activities of senescenceassociated cytokines.

Interleukin 6 Signaling Regulates Promyelocytic Leukemia Protein Gene Expression in Human Normal and Cancer Cells

“…Expression of PML is stimulated by interferons of type I and II (9 -12), which are produced during cellular responses to viral infection (for review, see Ref. 56) and some genotoxic insults (32,33). Response of PML to both types of interferons is mediated via transcription factors STAT1 and STAT2 (27), and it is suppressed by inhibitors of histone deacetylases (47).…”

“…Activity of IL6-JAK/STAT Signaling Is Cell Type-dependent and Correlates with PML Expression-As reported previously, PML transcription is regulated by interferon-stimulated JAK/ STAT signaling (27,33). Therefore, we next compared the basal activity of JAK/STAT1/3/5 signaling in U2OS, HeLa, and BJ cells.…”

“…Manner-In our previous work we showed that PML gene transcription is regulated in an autocrine manner via cytokine-activated JAK/STAT signaling pathways in human normal and cancer cell lines exposed to various genotoxic compounds (33). To provide further insight into PML gene regulation, we asked whether autocrine/paracrine signaling determines PML levels also in naïve cells grown under unperturbed conditions in vitro.…”

“…Activated JAK/STAT signaling accompanying lasting DNA damage response during drug-induced premature senescence contributes to multiplication of nuclear PML compartment through modulation of PML transcript level (33). Notably, PML NBs were found to quickly reassemble after DNA damage and to co-associate with persistent DNA lesions (33)(34)(35), implicating PML NBs in metabolism of damaged DNA (36). Importantly, persistent DNA damage response activity and development of cellular senescence is a feature characteristic for early stages of human tumorigenesis (37)(38)(39)(40)(41).…”

“…29 -31), which can also include type I and type II interferons (32). Activated JAK/STAT signaling accompanying lasting DNA damage response during drug-induced premature senescence contributes to multiplication of nuclear PML compartment through modulation of PML transcript level (33). Notably, PML NBs were found to quickly reassemble after DNA damage and to co-associate with persistent DNA lesions (33)(34)(35), implicating PML NBs in metabolism of damaged DNA (36).…”