Dynamic Recruitment of Licensing Factor Cdt1 to Sites of DNA Damage

For genomic integrity to be maintained, the cell cycle and DNA damage responses must be linked. Cdt1, a G1-specific cell-cycle factor, is targeted for proteolysis by the Cul4-Ddb1Cdt2 ubiquitin ligase following DNA damage. Using a laser nanosurgery microscope to generate spatially restricted DNA damage within the living cell nucleus, we show that Cdt1 is recruited onto damaged sites in G1 phase cells, within seconds of DNA damage induction. PCNA, Cdt2, Cul4, DDB1 and p21Cip1 also accumulate rapidly to damaged sites. Cdt1 recruitment is PCNA-dependent, whereas PCNA and Cdt2 recruitment are independent of Cdt1. Fitting of fluorescence recovery after photobleaching profiles to an analytic reaction-diffusion model shows that Cdt1 and p21Cip1 exhibit highly dynamic binding at the site of damage, whereas PCNA appears immobile. Cdt2 exhibits both a rapidly exchanging and an apparently immobile subpopulation. Our data suggest that PCNA provides an immobile binding interface for dynamic Cdt1 interactions at the site of damage, which leads to rapid Cdt1 recruitment to damaged DNA, preceding Cdt1 degradation

The S phase checkpoint promotes the Smc5/6 complex dependent SUMOylation of Pol2, the catalytic subunit of DNA polymerase ε

Replication fork stalling and accumulation of single-stranded DNA trigger the S phase checkpoint, a signalling cascade that, in budding yeast, leads to the activation of the Rad53 kinase. Rad53 is essential in maintaining cell viability, but its targets of regulation are still partially unknown. Here we show that Rad53 drives the hyper-SUMOylation of Pol2, the catalytic subunit of DNA polymerase ε, principally following replication forks stalling induced by nucleotide depletion. Pol2 is the main target of SUMOylation within the replisome and its modification requires the SUMO-ligase Mms21, a subunit of the Smc5/6 complex. Moreover, the Smc5/6 complex co-purifies with Pol ε, independently of other replisome components. Finally, we map Pol2 SUMOylation to a single site within the N-terminal catalytic domain and identify a SUMO-interacting motif at the C-terminus of Pol2. These data suggest that the S phase checkpoint regulate Pol ε during replication stress through Pol2 SUMOylation and SUMO-binding abilit

Checkpoint Inhibitors in Head and Neck Cancer: Rationale, Clinical Activity, and Potential Biomarkers

The discovery and antibody targeting of immune regulatory molecules such as programmed cell death protein 1 (PD-1) and cytotoxic T lymphocyte antigen 4 (CTLA-4) pathways have led to clinically meaningful anti-cancer results. Rapid advances are being made in a variety of tumor types resulting in regulatory approvals in melanoma, non small cell lung cancer, and renal cell cancer. Numerous ongoing studies are expected to establish the worth of PD-1 pathway inhibitors in other tumor types as well as in combinations with approved agents. Head and neck squamous cell carcinoma (HNSCC) represents a complex group of malignancies characterized by profound immunosuppression and is an excellent candidate for investigation in this exciting field. However, given the fact that a subset of patients will likely benefit, it is critical to focus on biomarker development for appropriate patient selection and facilitation of trial design. As immunotherapy is settling in cancer treatment, immune checkpoint inhibitors are emerging as one of the most promising agents. © 2016, Springer Science+Business Media New York

De-escalating strategies in hpv-associated head and neck squamous cell carcinoma

HPV-related head and neck squamous cell carcinoma (HNSCC) has emerged as a diverse clinical and biological disease entity, mainly in young patients with oropharyngeal tumors who are nonsmokers and nondrinkers. Indeed, during the past few years, the pendulum has shifted towards a new epidemiological reality, the “HPV pandemic”, where the majority of oropharyngeal squamous cell carcinomas (OPSCCs) are attributed to HPV. The oncogenic potential of the virus is associated to its capacity of integrating oncogenes E6 and E7 into the host cell, leading to the inactivation of several tumor suppressor genes, such as Rb. HPV status can affect prognosis in OPSCC, but its role as a predictive biomarker remains to be elucidated. Given the favorable prognosis associated with HPV-positive disease, the concept of de-escalation treatment strategies has been developed with the primary intent being the reduction of treatment-related long-term toxicities. In this review, we aim to depict current data regarding treatment de-escalation in HPV-associated OPSCC and discuss ongoing clinical trials. © 2021 by the authors. Licensee MDPI, Basel, Switzerland

Special issue about head and neck cancers: HPV positive cancers

The oropharynx has become the leading primary site for Human Papilloma Virus (HPV)-associated head and neck cancer. HPV positive oropharyngeal squamous cell carcinoma (HPV+ OSCC) has emerged as an epidemic not easily recognized by many physicians, resulting in delays in diagnosis and management. HPV+ OSCC traditionally refers to younger, healthier patients with high economic status and high-risk sexual behavior and is related to improved prognosis. De-intensification strategies are being evaluated in ongoing clinical trials and if validated, might help spare severe morbidity associated with current cisplatin-based chemoradiotherapy, which is the standard of care for all patients with locally advanced head and neck cancer. On the other hand, whether HPV status represents an important prognostic factor for non-oropharyngeal sites remains to be elucidated. © 2020 by the authors. Licensee MDPI, Basel, Switzerland

A drug safety evaluation of atezolizumab in locally advanced or metastatic urothelial carcinoma

Introduction: Immune checkpoint inhibitors (ICIs) have rapidly changed the treatment landscape, demonstrating dramatic clinical efficacy in various cancers. Areas covered: In urothelial cancer (UC), several ICIs have been approved in platinum refractory disease and also as first-line therapy in patients that fulfill the criteria for cisplatin ineligibility. Atezolizumab is a monoclonal antibody that targets the immune checkpoint Programmed Cell Death Ligand-1 (PD-L1) and has been currently approved for advanced UC, non-small cell lung cancer, small cell lung cancer, and triple-negative breast cancer. Herein, we provide a summary of the mechanism of action, safety, and clinical efficacy of atezolizumab in UC. Expert opinion: Atezolizumab is a drug with a favorable toxicity profile and will obtain more indications in the future in UC and other cancers. Treating physicians should be aware of treatment-related and immune-related adverse events associated with the drug. © 2020, © 2020 Informa UK Limited, trading as Taylor & Francis Group

The promise of immunotherapy in head and neck squamous cell carcinoma: Combinatorial immunotherapy approaches

The immune system plays a fundamental role in preventing cancer development by recognising and eliminating tumour cells. The recent success in the field of immunotherapy has confirmed the potential to exploit the immune response as a cancer treatment. Head and neck squamous cell carcinoma (HNSCC) is a malignancy characterized by dismal prognosis and high mortality rate; low survival outcomes in combination with significant toxicity of current treatment strategies highlight the necessity for novel therapeutic modalities. HNSCC is a favourable disease for immunotherapy, as immune escape plays a key role in tumour initiation and progression. T-cell checkpoint inhibitors targeting programmed cell death protein-1 have emerged as novel immunotherapy agents showing remarkable efficacy in HNSCC. However, only a minority of patients derive benefit for single-agent immunotherapies. In this regard, combinatorial immunotherapy approaches represent an alternative strategy that might increase the number of patients who respond to immunotherapy. Focusing on HNSCC, this review will summarise novel combinations of immune checkpoint blockade with other immunotherapy treatment modalities. © European Society for Medical Oncology (unless otherwise stated in the text of the article) 2017. All rights reserved