p16 Represses DNA Damage Repair via a Novel Ubiquitin-Dependent Signaling Cascade

Molkentine, David P.; Molkentine, Jessica M.; Bridges, Kathleen A.; Valdecanas, David R.; Dhawan, Annika; Bahri, Reshub; Hefner, Andrew J.; Kumar, Manish; Yang, Liangpeng; Abdelhakiem, Mohamed; Pifer, Phillip M.; Sandulache, Vlad C.; Sheth, Aakash; Beadle, Beth M.; Mason, Kathryn A.; Pickering, Curtis R.; Meyn, Raymond E.; Skinner, Heath D.

doi:10.1158/0008-5472.can-21-2101

Cited by 19 publications

(14 citation statements)

References 55 publications

(71 reference statements)

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“…This was mechanistically explained by a decreased expression of the Rad51 loading factors BRCA2 or Cyclin D1, with the latter being a consequence of the high p16 levels in these cells (8)(9)(10). p16 was further reported to cause a decrease in TRIP12 expression and subsequently an increase in the ubiquitin ligase RNF168, which was also described to result in defective DSB repair, presumably by interfering with HR (11,12). Intriguingly, the E7 oncoprotein from high-risk HPV-types was recently shown to bind RNF168 and impede its function at DSBs, leading to enhanced repair by HR (13).…”

Section: Introductionmentioning

confidence: 99%

A Lack of Effectiveness in the ATM-Orchestrated DNA Damage Response Contributes to the DNA Repair Defect of HPV-Positive Head and Neck Cancer Cells

et al. 2022

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Patients with human papillomavirus-positive squamous cell carcinoma of the head and neck (HPV+ HNSCC) have a favorable prognosis compared to those with HPV-negative (HPV−) ones. We have shown previously that HPV+ HNSCC cell lines are characterized by enhanced radiation sensitivity and impaired DNA double-strand break (DSB) repair. Since then, various publications have suggested a defect in homologous recombination (HR) and dysregulated expression of DSB repair proteins as underlying mechanisms, but conclusions were often based on very few cell lines. When comparing the expression levels of suggested proteins and other key repair factors in 6 HPV+ vs. 5 HPV− HNSCC strains, we could not confirm most of the published differences. Furthermore, HPV+ HNSCC strains did not demonstrate enhanced sensitivity towards PARP inhibition, questioning a general HR defect. Interestingly, our expression screen revealed minimal levels of the central DNA damage response kinase ATM in the two most radiosensitive HPV+ strains. We therefore tested whether insufficient ATM activity may contribute to the enhanced cellular radiosensitivity. Irrespective of their ATM expression level, radiosensitive HPV+ HNSCC cells displayed DSB repair kinetics similar to ATM-deficient cells. Upon ATM inhibition, HPV+ cell lines showed only a marginal increase in residual radiation-induced γH2AX foci and induction of G2 cell cycle arrest as compared to HPV− ones. In line with these observations, ATM inhibition sensitized HPV+ HNSCC strains less towards radiation than HPV− strains, resulting in similar levels of sensitivity. Unexpectedly, assessment of the phosphorylation kinetics of the ATM targets KAP-1 and Chk2 as well as ATM autophosphorylation after radiation did not indicate directly compromised ATM activity in HPV-positive cells. Furthermore, ATM inhibition delayed radiation induced DNA end resection in both HPV+ and HPV− cells to a similar extent, further suggesting comparable functionality. In conclusion, DNA repair kinetics and a reduced effectiveness of ATM inhibition clearly point to an impaired ATM-orchestrated DNA damage response in HPV+ HNSCC cells, but since ATM itself is apparently functional, the molecular mechanisms need to be further explored.

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Section: Introductionmentioning

confidence: 99%

A Lack of Effectiveness in the ATM-Orchestrated DNA Damage Response Contributes to the DNA Repair Defect of HPV-Positive Head and Neck Cancer Cells

et al. 2022

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“…Furthermore, inhibitors of electron transport chain complexes, TCA cycle enzymes, and glutamine metabolism in clinical trials for various treatment-refractory cancers (47) may have value for a subset of HPV+ OPSCCs of similar metabolic phenotype. Although aggressively targeting oxidative metabolism in the clinic remains hampered by toxicity, the severely impaired DNA damage repair phenotype in HPV+ OPSCCs (3) may widen the therapeutic window by allowing responses at lower drug doses than those needed for other cancers.…”

Section: Discussionmentioning

confidence: 99%

“…The seven treatment-naïve HPV+ OPSCC PDXs used in this study were established and passaged as described by us in the subcutaneous flank of NSG mice (22). The PDXs were harvested for RNAseq in triplicate upon reaching 1cm 3 . Volumes were calculated as width 2 x length/2.…”

Section: Growth and Rna Sequencing Of Pdxsmentioning

confidence: 99%

“…HPV+ OPSCCs are typically sensitive to the combination of radiation plus cisplatin, which is often curative for this disease (2). Impaired DNA repair mechanisms help make HPV+ OPSCCs sensitive as a group to these therapies (3), which kill tumors by increasing reactive oxygen species (ROS) generation beyond cellular antioxidant capacity, leading to uncontrolled damage to DNA, protein, and lipids (4). High cure rates for these patients have sustained interest in de-escalating cisplatin and radiation therapy, whose toxic sequelae leave lifelong disabilities in survivors (5).…”

Section: Introductionmentioning

confidence: 99%

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Human papilloma virus E6 regulates therapy responses in oropharyngeal cancer by repressing the PGC-1α/ERRα axis

Sannigrahi

Rajagopalan

Lai

et al. 2022

Preprint

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Therapy with radiation plus cisplatin kills human papilloma virus-related (HPV+) oropharyngeal squamous cell carcinomas (OPSCCs) by increasing reactive oxygen species beyond cellular antioxidant capacity. To explore why some patients fail these standard treatments, we evaluated whether the variation in HPV oncoprotein levels among HPV+ OPSCCs impacts mitochondrial metabolism, a source of antioxidant capacity. In cell line and patient-derived xenograft models, levels of HPV full-length E6 (fl-E6) inversely correlated with oxidative phosphorylation, antioxidant capacity, and therapy resistance, and fl-E6 was the only HPV oncoprotein to display such correlation. Ectopically expressing fl-E6 in models with low levels reduced mitochondrial mass, depleted antioxidant capacity, and sensitized to therapy. In this setting, fl-E6 repressed the PGC-1α/ERRα pathway for mitochondrial biogenesis by reducing p53-dependent PGC-1α transcription. Concordant observations were made in three clinical cohorts, where expression of mitochondrial components was higher in tumors of patients with reduced survival. These tumors contained the lowest fl-E6 levels, highest p53 target gene expression, and an activated PGC-1α/ERRα pathway. Our findings demonstrate that E6 can potentiate treatment responses by depleting mitochondrial antioxidant capacity and provide evidence for low E6 negatively impacting patient survival. E6 interaction with the PGC-1α/ERRα axis has implications for predicting and targeting treatment resistance in OPSCC.

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“…The MTT assay was performed similar to previous publication with the following modifications (43). Depending on cell line, 1,000-4,000 cells per well in 100 μL of media were plated into 96-well plates.…”

Section: Methodsmentioning

confidence: 99%

FAK drives resistance to therapy in HPV-negative head and neck cancer in a p53-dependent manner

Pifer

Yang

Kumar

et al. 2022

Preprint

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Radiation and platinum-based chemotherapy form the backbone of therapy in HPV-negative head and neck squamous cell carcinoma (HNSCC). We have correlated focal adhesion kinase (FAK/PTK2) expression with radioresistance and worse outcome in these patients. However, the importance of FAK in driving radioresistance and its effects on chemoresistance in these patients remain unclear. We performed an in vivo shRNA screen using targetable libraries to address these questions and identified FAK as an excellent target for both radio- and chemosensitization. Because TP53 is mutated in over 80% of HPV-negative HNSCC, we hypothesized that mutant TP53 may facilitate FAK-mediated therapy resistance. FAK inhibitor increased sensitivity to radiation, increased DNA damage and repressed homologous recombination and non-homologous end joining repair in mutant, but not wild-type, TP53 HPV-negative HNSCC cell lines. Mutant TP53 cisplatin-resistant cell line had increased FAK phosphorylation compared to wild-type, and FAK inhibition partially reversed cisplatin resistance. To validate these findings, we utilized a HNSCC cohort to show that FAK copy number and gene expression were associated with worse disease-free survival in mutant TP53, but not wild-type TP53, HPV-negative HNSCC tumors. Thus, FAK may represent a targetable therapeutic sensitizer linked to a known genomic marker of resistance.

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p16 Represses DNA Damage Repair via a Novel Ubiquitin-Dependent Signaling Cascade

Cited by 19 publications

References 55 publications

A Lack of Effectiveness in the ATM-Orchestrated DNA Damage Response Contributes to the DNA Repair Defect of HPV-Positive Head and Neck Cancer Cells

A Lack of Effectiveness in the ATM-Orchestrated DNA Damage Response Contributes to the DNA Repair Defect of HPV-Positive Head and Neck Cancer Cells

Human papilloma virus E6 regulates therapy responses in oropharyngeal cancer by repressing the PGC-1α/ERRα axis

FAK drives resistance to therapy in HPV-negative head and neck cancer in a p53-dependent manner

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