Reactive oxygen species and p21Waf1/Cip1 are both essential for p53-mediated senescence of head and neck cancer cells

Treatment of head and neck squamous cell carcinoma, HNSCC, often requires multimodal therapy, including radiation therapy. The efficacy of radiotherapy in controlling locoregional recurrence, the most frequent cause of death from HNSCC, is critically important for patient survival. One potential biomarker to determine radioresistance is TP53 whose alterations are predictive of poor radiation response. DNA-damaging reactive oxygen species (ROS) are a by-product of ionizing radiation that lead to the activation of p53, transcription of p21(cip1/waf1) and, in the case of wild-type TP53 HNSCC cells, cause senescence. The expression of p21 and production of ROS have been associated with the induction of cellular senescence, but the intricate relationship between p21 and ROS and how they work together to induce senescence remains elusive. For the first time, we show that persistent exposure to low levels of the ROS, hydrogen peroxide, leads to the long-term expression of p21 in HNSCC cells with a partially functional TP53, resulting in senescence. We conclude that the level of ROS is crucial in initiating p53's transcription of p21 leading to senescence. It is p21's ability to sustain elevated levels of ROS, in turn, that allows for a long-term oxidative stress, and ensures an active p53-p21-ROS signaling loop. Our data offer a rationale to consider the use of either ROS inducing agents or therapies that increase p21 expression in combination with radiation as approaches in cancer therapy and emphasizes the importance of considering TP53 status when selecting a patient's treatment options.

Long-term outcomes with concurrent carboplatin, paclitaxel and radiation therapy for locally advanced, inoperable head and neck cancer

BACKGROUND

Our goal was to evaluate long-term efficacy outcomes of patients with squamous cell carcinoma of the head and neck (SCCHN) treated with carboplatin, paclitaxel (Taxol) and radiotherapy.

PATIENTS AND METHODS

We conducted a phase II trial in inoperable patients with locally advanced SCCHN. Carboplatin 100 mg/m(2) and paclitaxel 40 mg/m(2) were administered i.v. once a week during external beam radiation therapy (180 cGy per fraction) for 6-7 weeks. Interstitial brachytherapy was used as a boost in selected patients with primary malignancies of the oral cavity and the oropharynx.

RESULTS

Fifty-five patients were enrolled. Fifty-two patients (95%) had stage IV and 51 (93%) had technically unresectable disease; 62% had an oropharyngeal primary site. Twenty-one patients underwent brachytherapy boost. Grade 3 or 4 mucositis occurred in 30% of patients. One death occurred during treatment that was related to complications of gastrostomy tube placement. Forty of 50 assessable patients (80%) had an objective response, with a complete response rate of 52%. With a median follow-up of 69 months for surviving patients, the 5-year progression-free survival was 36% and the 5-year overall survival was 35%. Two of the 18 long-term survivors of >50 months were gastrostomy tube feeding dependent. Patients undergoing brachytherapy boost (n = 21) had similar outcomes compared with the rest of the patients. In multivariate analysis, baseline hemoglobin levels and N stage were predictive of survival.

CONCLUSION

Treatment with concurrent carboplatin, paclitaxel and radiation is safe and offers curative potential for poor prognosis patients with locally advanced SCCHN.

Long-term outcomes with concurrent carboplatin, paclitaxel, and radiation therapy in locally advanced, inoperable head and neck cancer

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Background: Our goal was to evaluate long-term outcomes of patients with squamous cell carcinoma of the head and neck (SCCHN) treated with carboplatin, paclitaxel, and radiotherapy. Methods: We conducted a phase II trial in inoperable patients with locally advanced SCCHN. Carboplatin 100 mg/m2 and paclitaxel 40 mg/m2 were administered intravenously once a week during external beam radiotherapy (once daily, 180 cGy/fraction) for 6–7 weeks. Interstitial brachytherapy was used as a boost in selected patients with primary malignancies of the oral cavity and the oropharynx. Results: 55 patients were enrolled. 52 patients (95%) had stage IV and 51 (93%) had technically unresectable disease; 62% had an oropharyngeal primary site. 21 patients underwent brachytherapy boost. Grade 3 or 4 mucositis occurred in 30% of patients. One death occurred during treatment; it was related to complications of gastrostomy tube (G-tube) placement. Forty of 50 evaluable patients (80%) had an objective response, with a complete response rate of 52%. With a median follow-up of 69 months years for surviving patients, the 5-year progression-free survival (PFS) was 36% and the 5-year overall survival (OS) was 35%. Two of the 18 long-term survivors of >50 months were G-tube feeding dependent. Patients undergoing brachytherapy boost (n=21) had similar outcomes compared with the rest of the patients. In multivariate analysis, baseline hemoglobin levels and N stage were predictive of survival. Conclusion: Treatment with concurrent carboplatin, paclitaxel and radiation is safe and offers curative potential for poor prognosis patients with locally advanced SCCHN.

No significant financial relationships to disclose.