Chia-Jung Busch

HNSCC cell lines positive for HPV and p16 possess higher cellular radiosensitivity due to an impaired DSB repair capacity

BACKGROUND AND PURPOSE When treated by radiotherapy, patients with squamous cell carcinomas of the head and neck (HNSCC) positive for HPV and p16(INK4a) possess a clearly favorable prognosis as compared to those with HPV-negative HNSCC. The aim of this work was to study whether the better outcomes might be caused by an enhanced cellular radiosensitivity. MATERIALS AND METHODS The radiation response of five HPV/p16(INK4a)-positive and five HPV-negative cell lines was characterized with regard to cellular radiosensitivity by colony formation assay. Furthermore G1- and G2-arrest, apoptosis and residual DNA double-strand breaks (DSB) were analyzed by the colcemid-based G1-efflux assay, propidium iodide staining, the detection of PARP cleavage, the fluorescence-based detection of caspase activity and the immunofluorescence staining of γH2AX and 53BP1 foci. RESULTS On average, the cellular radiosensitivity of the HNSCC cell lines positive for HPV and p16(INK4a) was higher as compared to the sensitivity of a panel of five HPV-negative HNSCC cell lines (SF3=0.2827 vs. 0.4455). The higher sensitivity does not result from increased apoptosis or the execution of a permanent G1-arrest, but is rather associated with both, elevated levels of residual DSBs and extensive G2-arrest. CONCLUSIONS Increased cellular radiosensitivity due to compromised DNA repair capacity is likely to contribute to the improved outcome of patients with HPV/p16(INK4a)-positive tumors when treated by radiotherapy.

New treatment strategies for HPV-positive head and neck cancer

Epidemiological studies show an increasing incidence of human papilloma virus-associated oropharyngeal cancer. HPV-positive head and neck squamous cell carcinoma (HNSCC) is recognized as a special subgroup of HNSCC. Because HPV-positive patients are often younger and have an outstanding prognosis, long-term toxicities of therapy have become an important issue. Current clinical trials focus on a reduction of treatment-related toxicity and the development of HPV-specific therapies. New treatment strategies include a dose reduction of radiotherapy, the use of cetuximab instead of cisplatin for chemoradiation and transoral robotic surgery (TORS). Increasing comprehension of the molecular background of HPV-associated HNSCC has also lead to more specific treatment attempts including immunotherapeutic strategies. Whereas recently published data shed light on immune mechanisms resulting in a tolerogenic niche for HPV and HPV-associated HNSCC, other studies focus on specific vaccination of HPV-positive HNSCC. This study will summarize current therapy approaches and illustrate ongoing clinical trials in the field of HPV-positive HNSCC.

Functional outcomes, feasibility, and safety of resection of transoral robotic surgery: Single-institution series of 35 consecutive cases of transoral robotic surgery for oropharyngeal squamous cell carcinoma

This is a single‐institution prospective study in a tertiary care center to evaluate feasibility, completeness of resection, and functional outcomes for oropharyngeal squamous cell carcinoma (SCC) treated primarily with transoral robotic‐assisted resection.

HPV-positive HNSCC cell lines but not primary human fibroblasts are radiosensitized by the inhibition of Chk1

PURPOSE Despite the comparably high cure rates observed for HPV-positive HNSCC, there is still a great need for specific tumor radiosensitization due to the often severe side effects resulting from intense radiochemotherapy. We recently demonstrated that HPV-positive HNSCC cell lines are characterized by a defect in DNA double-strand break repair associated with a pronounced G2-arrest. Here we tested whether abrogation of this radiation-induced G2-arrest by the inhibition of Chk1 results in specific radiosensitization of HPV-positive HNSCC cells. MATERIALS AND METHODS Experiments were performed with five HPV and p16-positive (93-VU-147T, UM-SCC-47, UT-SCC-45, UD-SCC-2, UPCI-SCC-154) and two HPV and p16-negative HNSCC cell lines, as well as two normal human fibroblast strains. Chk1 was inhibited by the selective inhibitor PF-00477736. Cell cycle distribution was determined by flow cytometry, Chk1-activity via Western blot and cell survival by colony formation assay. RESULTS With the exception of UPCI-SCC-154, the inhibition of Chk1 was found to abolish the pronounced radiation-induced G2-arrest in all HPV-positive cells utilized. All tumor cell lines that demonstrated the abrogation of G2-arrest also demonstrated radiosensitization. Notably, in G1-arrest-proficient normal human fibroblasts no radiosensitization was induced. CONCLUSION Abrogation of the G2 checkpoint through the inhibition of Chk1 may be used to selectively increase the cellular radiosensitivity of HPV-positive HNSCC without affecting the surrounding normal tissue.

The current role of systemic chemotherapy in the primary treatment of head and neck cancer

The treatment of patients with locoregionally advanced squamous cell carcinoma of the head and neck (HNSCC) is still evolving into the perfect combination of the different multidisciplinary approaches. Induction chemotherapy (ICT) prior to planned definitive local therapy is widely used in this patient population for over 30 years but it is still unclear how to incorporate ICT into multimodality treatment the best. It appears to have a role in selected clinical situations especially for those patients with high risk for distant metastasis. However, since ICT protocols in different studies varies a lot, a comparative and consistent statement of benefits is difficult. We show the recent developments including randomized trials comparing radiochemotherapy (RCT) and ICT followed by definitive RCT here. This review summarizes how ICT has developed over the years, provides critical remarks of recent developments, and discusses how clinical trials including ICT should be conducted in the future.

Liquid biopsy monitoring uncovers acquired RAS-mediated resistance to cetuximab in a substantial proportion of patients with head and neck squamous cell carcinoma

Resistance to epidermal growth factor receptor (EGFR)-targeted therapy is insufficiently understood in head and neck squamous cell carcinoma (HNSCC), entailing the lack of predictive biomarkers. Here, we studied resistance-mediating EGFR ectodomain and activating RAS mutations by next-generation sequencing (NGS) of cell lines and tumor tissue of cetuximab-naïve patients (46 cases, 12 cell lines), as well as liquid biopsies taken during and after cetuximab/platinum/5-fluorouracil treatment (20 cases). Tumors of cetuximab-naïve patients were unmutated, except for HRAS mutations in 4.3% of patients. Liquid biopsies revealed acquired KRAS, NRAS or HRAS mutations in more than one third of patients after cetuximab exposure. 46% of patients with on-treatment disease progression showed acquired RAS mutations, while no RAS mutations were found in the non-progressive subset of patients, indicating that acquisition of RAS mutant clones correlated significantly with clinical resistance (Chi square p=0.032). The emergence of mutations preceded clinical progression in half of the patients, with a maximum time from mutation detection to clinical progression of 16 weeks. RAS mutations account for acquired resistance to EGFR-targeting in a substantial proportion of HNSCC patients, even though these tumors are rarely mutated at baseline. Liquid biopsies may be used for mutational monitoring to guide treatment decisions.

The inhibition of PARP but not EGFR results in the radiosensitization of HPV/p16-positive HNSCC cell lines

BACKGROUND AND PURPOSE HPV-negative and HPV-positive HNSCC comprise distinct tumor entities with different biological characteristics. Specific regimens for the comparably well curable HPV-positive entity that reduce side effects without compromising outcome have yet to be established. Therefore, we tested here whether the inhibition of EGFR or PARP may be used to specifically enhance the radiosensitivity of HPV-positive HNSCC cells. MATERIALS AND METHODS Experiments were performed with five HPV/p16-positive HNSCC cell lines. Inhibitors used were cetuximab, olaparib and PF-00477736. The respective inhibition of EGFR, PARP and Chk1 was evaluated by Western blot, immunofluorescence analysis and assessment of cell cycle distribution. Cell survival was assessed by colony formation assay. RESULTS Inhibition of EGFR by cetuximab failed to radiosensitize any of the HPV-positive HNSCC cell lines tested. In contrast, PARP-inhibition resulted in a substantial radiosensitization of all strains, with the sensitization being further enhanced by the additional inhibition of Chk1. CONCLUSIONS PARP-inhibition effectively radiosensitizes HPV-positive HNSCC cells and may therefore represent a viable alternative to chemotherapy possibly even allowing for a reduction in radiation dose. For the latter, PARP-inhibition may be combined with the inhibition of Chk1. In contrast, the inhibition of EGFR cannot be expected to radiosensitize HPV-positive HNSCC through the modulation of cellular radiosensitivity.

Current studies of immunotherapy in head and neck cancer

Recently, enormous progress in cancer therapy has been achieved by the use of immune checkpoint inhibitors. Activating the bodys own immune system has added a novel and powerful therapeutic option for the treatment of melanoma and lung cancer. Furthermore, the potential use of immunotherapy is being extensively explored also in other malignancies.

Initial learning curve of single-incision transaxillary robotic hemi- and total thyroidectomy--A single team experience from Europe.

INTRODUCTION The primary advantage of robotic thyroidectomy is to avoid a neck scar. On the other hand, this sophisticated technique implies some potential risks otherwise not associated with conventional thyroidectomy, increased costs, and prolonged operating times. With all these factors being an important issue, we analysed the data of our initial European series in order to understand the nature of the learning curve for this technique. METHODS Ten patients underwent transaxillary robotic thyroidectomy for benign disease, performed consistently by the same surgeon with the same team, within a timeframe of 12 months. There were four total thyroidectomies and six hemithyroidectomies. Operating times broken down into creating the working space, docking the robot, and console work (including wound closure), were prospectively recorded and evaluated. RESULTS By the end of the initial learning curve comprising ten patients, the total operating time for a robotic hemithyroidectomy and for a total thyroidectomy has decreased by 49% to 190 min, and by 31% to 229 min, respectively. Intraoperative complications were successfully managed without conversion to open access surgery. CONCLUSION The learning curve for transaxillary robotic thyroidectomy is rather steep; reasonable progress in terms of operating times can be achieved within the first ten cases. Consistency in the team and careful patient selection are paramount factors for success.

G2-checkpoint targeting and radiosensitization of HPV/p16-positive HNSCC cells through the inhibition of Chk1 and Wee1

BACKGROUND AND PURPOSE HPV-positive HNSCC cells are characterized by radiosensitivity, inefficient DNA double-strand break repair and a profound and prolonged arrest in G2. Here we explored the effect of clinically relevant inhibitors of Chk1 and Wee1 to inhibit the radiation-induced G2-arrest in order to achieve further radiosensitization. MATERIAL AND METHODS Assessment of Chk1 activity by Western blot; assessment of cell cycle distribution by propidium iodide staining and flow cytometry; assessment of cell survival by colony formation assay. HPV+ HNSCC cell lines: UD-SCC-2, UM-SCC-47 and UPCI-SCC-154; Chk1 inhibitors: LY2603618, MK8776; Wee1 inhibitor: AZD1775. RESULTS Specific Chk1 inhibitors efficiently abrogated the radiation-induced G2-arrest and caused radiosensitization. Wee-inhibition by AZD1775 resulted in the activation of Chk1. This feedback mechanism is likely to counteract some of the effects of Wee1 inhibition but could be antagonized through the combined inhibition of both kinases. Combined inhibition was effective using profoundly reduced concentrations of both inhibitors and resulted in more efficient radiosensitization of the HPV-positive cell lines compared to p53 proficient normal human fibroblasts. CONCLUSIONS Specific Chk1 inhibitors as well as the combined inhibition of Chk1 and Wee1 radiosensitize HPV-positive HNSCC cells.