HPV, Tumor Metabolism and Radiosensitivity in Head and Neck Cancer

描述（由申请人提供）：本研究的长期目标是获得可用于改善头颈部鳞状细胞癌（HNSCC）患者预后的科学知识。HNSCC是世界上10种最常见的癌症之一，位于口咽部位的HNSCC的发病率正在增加。这一趋势归因于与乳头状瘤病毒（HPV）相关的HNSCC， HPV已被认为是一种不同于主要由吸烟相关/化学诱导的HPV阴性HNSCC的生物实体。有充分证据表明，与hpv阴性患者相比，hpv阳性口咽癌患者的局部区域复发率显著降低，总体生存率显著提高，特别是接受放射治疗的患者。在这项R21应用中，我们假设hpv阳性HNSCC患者的生存优势是由于hpv相关癌症和吸烟相关癌症之间肿瘤代谢途径的差异调节所介导的放射敏感性增加。这个假设是基于其他人的研究以及我们的初步数据。先前的一项研究表明，将显性阴性p53突变体转染到口腔角化细胞，模拟吸烟相关的癌症，导致缺氧信号通路（HIF1）上调，从而增加糖代谢，而将HPV16-E6引入这些细胞，导致HIF-1下调。重要的是，最近的研究表明，hif1药物糖代谢与放射抵抗之间存在关联。与此一致的是，我们的初步数据显示hpv阴性HNSCC细胞表达较高水平的己糖激酶，这是糖酵解的限制性酶，而hpv阳性HNSCC细胞表达低水平的己糖激酶和高水平的细胞色素c氧化酶，这是线粒体呼吸途径的关键酶。综上所述，我们的工作假设是hpv阳性的HNSCC细胞依赖于线粒体呼吸，糖代谢降低，而吸烟相关/化学诱导的HNSCC细胞严重依赖糖酵解途径。为了解决这一假设并开发基于生物标志物的辐射增敏剂，我们提出了以下具体目标：(1)在选定的口咽癌细胞系中研究HPV状态与肿瘤代谢的关系，并阐明HPV16癌蛋白在体外肿瘤代谢中的作用；(2)在体外和体内动物模型中评价药理调控代谢途径对HNSCC细胞辐射敏感性的影响；(3)检测临床口咽癌样本中肿瘤代谢途径基因表达水平与HPV状态和总生存期的关系；(4)探讨糖尿病HNSCC患者的总生存率是否低于非糖尿病HNSCC患者，特别是与放疗有关。这项探索性R21应用的完成将有助于我们了解hpv相关放射敏感性的分子基础，并为进一步的患者分层和生物标志物驱动的设计提供重要信息

DESCRIPTION (provided by applicant): The long-term goal of this research is to gain scientific knowledge that can be used to improve outcome in patients with head and neck squamous cell carcinoma (HNSCC). HNSCC is one of the 10 most common cancers worldwide, and the incidence of HNSCC located in the oropharyngeal sites is increasing. This trend has been attributed to HNSCC associated with papillomavirus (HPV), which has been recognized to be a distinct biological entity from the HPV-negative counterpart that is primarily smoking associated/chemically induced HNSCC. It is well documented that HPV-positive oropharyngeal cancer patients experience significantly lower locoregional recurrence and significantly higher overall survival in comparison with HPV-negative patients, especially among those who received radiation therapy. In this R21 application, we hypothesize that the survival advantage in patients with HPV-positive HNSCC results from increased radiosensitivity mediated through differential regulation of tumor metabolic pathways between HPV-associated and smoking-associated cancers. This hypothesis is based on studies from others as well as our preliminary data. A previous study showed that transfection of the dominant-negative p53 mutant into oral keratinocytes, mimicking smoking-associated cancer, results in upregulation of hypoxia signaling (HIF1) pathway, which in turn could increase glucose metabolism, whereas introduction of HPV16-E6 into those cells leads to downregulation of HIF-1. Importantly, recent studies suggested an association between HIF1-medicated glucose metabolism and radioresistance. Consistently, our preliminary data showed that HPV-negative HNSCC cells express higher levels of hexokinase, the rate-limiting enzyme in glycolysis, whereas HPV-positive HNSCC cells express low levels of hexokinase and high levels of cytochrome c oxidase, a key enzyme in the mitochondrial respiratory pathway. Taken together, our working hypothesis is that HPV-positive HNSCC cells rely on mitochondrial respiration with decreased glucose metabolism, whereas smoking-associated/chemically-induced HNSCC cells heavily rely on glycolytic pathways. To address this hypothesis and to develop a biomarker-based radiation sensitizer, we propose the following specific aims: (1) To investigate the relationship between the HPV status and tumor metabolism in selected oropharyngeal cancer cell lines and to elucidate the role of HPV16 oncoproteins in tumor metabolism in vitro; (2) To evaluate the effect of pharmacological manipulation of metabolic pathways on radiation sensitivity of HNSCC cells in vitro and in vivo animal model; (3) To examine expression levels tumor metabolic pathway genes in clinical oropharyngeal cancer samples in relation to HPV status and overall survival; and (4) To explore if overall survival is worse in diabetic HNSCC patients than in non-diabetic HNSCC patients, especially in relation to radiation therapy. Completion of this exploratory R21 application will help us understand molecular basis for HPV-associated radiosensitivity and provide important information for further patient stratification and the design of biomarker-driven therapy.