A laser-plasma–produced soft X-ray laser at 89 eV generates DNA double-strand breaks in human cancer cells

Senescent cells display senescence-associated (SA) phenotypic programs such as proliferation arrest (SAPA) and secretory phenotype (SASP), which mediate their impact on tissue homeostasis. Curiously, senescence-inducing persistent DNA double-strand breaks (pDSBs) cause an immediate DNA damage response (DDR) and SAPA, but SASP requires days to develop, suggesting it requires additional molecular events. Here, we show that pDSBs provoke delayed recruitment of MRN/ATM and KAT5/TRRAP (NuA4/Tip60) complexes to global chromatin. This coincided with activating histone marks on up-regulated SASP genes, whereas depletion of these complexes compromised the SASP. Conversely, histone deacetylase inhibition triggered accelerated MRN/ATM/Tip60-dependent SASP without pDSBs, interlacing acetylation and non-canonical DNA damage-independent, low-level DDR activity in SASP maturation. DDR/acetylation regulation of SA programs is preserved in human cancer cells, suggesting novel targets for modifying treatment-induced SA phenotypes. We propose that delayed chromatin recruitment of acetyltransferases cooperates with non-canonical DDR signaling to ensure SASP activation only in the context of senescence, and not in response to a transient DNA damage-induced proliferation arrest.

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RepID-deficient cancer cells are sensitized to a drug targeting p97/VCP segregase

Molecular & Cellular Toxicology ◽

10.1007/s13273-021-00121-0 ◽

2021 ◽

Author(s):

Sang-Min Jang ◽

Christophe E. Redon ◽

Haiqing Fu ◽

Fred E. Indig ◽

Mirit I. Aladjem

Keyword(s):

Dna Damage ◽

Cancer Cells ◽

Cell Sorting ◽

Clonogenic Survival ◽

Double Strand Breaks ◽

Dna Double Strand Breaks ◽

Strand Breaks ◽

Ubiquitinated Proteins ◽

Damage Response ◽

Survival Assay

Abstract Background The p97/valosin-containing protein (VCP) complex is a crucial factor for the segregation of ubiquitinated proteins in the DNA damage response and repair pathway. Objective We investigated whether blocking the p97/VCP function can inhibit the proliferation of RepID-deficient cancer cells using immunofluorescence, clonogenic survival assay, fluorescence-activated cell sorting, and immunoblotting. Result p97/VCP was recruited to chromatin and colocalized with DNA double-strand breaks in RepID-deficient cancer cells that undergo spontaneous DNA damage. Inhibition of p97/VCP induced death of RepID-depleted cancer cells. This study highlights the potential of targeting p97/VCP complex as an anticancer therapeutic approach. Conclusion Our results show that RepID is required to prevent excessive DNA damage at the endogenous levels. Localization of p97/VCP to DSB sites was induced based on spontaneous DNA damage in RepID-depleted cancer cells. Anticancer drugs targeting p97/VCP may be highly potent in RepID-deficient cells. Therefore, we suggest that p97/VCP inhibitors synergize with RepID depletion to kill cancer cells.

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Human papillomavirus E7 oncoprotein targets RNF168 to hijack the host DNA damage response

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1906102116 ◽

2019 ◽

Vol 116 (39) ◽

pp. 19552-19562 ◽

Cited By ~ 7

Author(s):

Justine Sitz ◽

Sophie Anne Blanchet ◽

Steven F. Gameiro ◽

Elise Biquand ◽

Tia M. Morgan ◽

...

Keyword(s):

Cervical Cancer ◽

Dna Damage ◽

Cancer Cells ◽

Genomic Instability ◽

E3 Ligase ◽

Human Papillomaviruses ◽

Double Strand Breaks ◽

Nuclear Bodies ◽

Dna Double Strand Breaks ◽

Strand Breaks

High-risk human papillomaviruses (HR-HPVs) promote cervical cancer as well as a subset of anogenital and head and neck cancers. Due to their limited coding capacity, HPVs hijack the host cell’s DNA replication and repair machineries to replicate their own genomes. How this host–pathogen interaction contributes to genomic instability is unknown. Here, we report that HPV-infected cancer cells express high levels of RNF168, an E3 ubiquitin ligase that is critical for proper DNA repair following DNA double-strand breaks, and accumulate high numbers of 53BP1 nuclear bodies, a marker of genomic instability induced by replication stress. We describe a mechanism by which HPV E7 subverts the function of RNF168 at DNA double-strand breaks, providing a rationale for increased homology-directed recombination in E6/E7-expressing cervical cancer cells. By targeting a new regulatory domain of RNF168, E7 binds directly to the E3 ligase without affecting its enzymatic activity. As RNF168 knockdown impairs viral genome amplification in differentiated keratinocytes, we propose that E7 hijacks the E3 ligase to promote the viral replicative cycle. This study reveals a mechanism by which tumor viruses reshape the cellular response to DNA damage by manipulating RNF168-dependent ubiquitin signaling. Importantly, our findings reveal a pathway by which HPV may promote the genomic instability that drives oncogenesis.

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Focused ultrasound radiosensitizes human cancer cells by enhancement of DNA damage

Strahlentherapie und Onkologie ◽

10.1007/s00066-021-01774-5 ◽

2021 ◽

Author(s):

Xinrui Zhang ◽

Mariana Bobeica ◽

Michael Unger ◽

Anastasia Bednarz ◽

Bjoern Gerold ◽

...

Keyword(s):

Prostate Cancer ◽

Dna Damage ◽

Cancer Cells ◽

Metabolic Activity ◽

Focused Ultrasound ◽

Double Strand Breaks ◽

High Intensity Focused Ultrasound ◽

Dna Double Strand Breaks ◽

Strand Breaks

Abstract Purpose High-intensity focused ultrasound (HIFU/FUS) has expanded as a noninvasive quantifiable option for hyperthermia (HT). HT in a temperature range of 40–47 °C (thermal dose CEM43 ≥ 25) could work as a sensitizer to radiation therapy (RT). Here, we attempted to understand the tumor radiosensitization effect at the cellular level after a combination treatment of FUS+RT. Methods An in vitro FUS system was developed to induce HT at frequencies of 1.147 and 1.467 MHz. Human head and neck cancer (FaDU), glioblastoma (T98G), and prostate cancer (PC-3) cells were exposed to FUS in ultrasound-penetrable 96-well plates followed by single-dose X‑ray irradiation (10 Gy). Radiosensitizing effects of FUS were investigated by cell metabolic activity (WST‑1 assay), apoptosis (annexin V assay, sub-G1 assay), cell cycle phases (propidium iodide staining), and DNA double-strand breaks (γH2A.X assay). Results The FUS intensities of 213 (1.147 MHz) and 225 W/cm2 (1.467 MHz) induced HT for 30 min at mean temperatures of 45.20 ± 2.29 °C (CEM43 = 436 ± 88) and 45.59 ± 1.65 °C (CEM43 = 447 ± 79), respectively. FUS improves the effect of RT significantly by reducing metabolic activity in T98G cells 48 h (RT: 96.47 ± 8.29%; FUS+RT: 79.38 ± 14.93%; p = 0.012) and in PC-3 cells 72 h (54.20 ± 10.85%; 41.01 ± 11.17%; p = 0.016) after therapy, but not in FaDu cells. Mechanistically, FUS+RT leads to increased apoptosis and enhancement of DNA double-strand breaks compared to RT alone in T98G and PC-3 cells. Conclusion Our in vitro findings demonstrate that FUS has good potential to sensitize glioblastoma and prostate cancer cells to RT by mainly enhancing DNA damage.

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