P63 mediators as therapeutic targets in HNSCC

描述(申请人提供)：这项提案的目标是通过定义活体肿瘤中的p63通路，使用基因组方法来确定头颈部鳞状细胞癌(HNSCC)的新治疗靶点。P53家族成员P63在大多数原发HNSCC肿瘤中过表达，对体内上皮前体的发育是必不可少的，提示该基因在肿瘤发生中起作用。我们最近使用针对特定p63异构体的小抑制RNA(SiRNA)的数据表明，p63表达缺失可诱导过表达p63的HNSCC细胞凋亡。相反，抑制p63对正常角质形成细胞或不表达p63的肿瘤细胞的存活没有影响。到目前为止，p63的下游机制仍然没有得到很好的描述。因此，首先要确定P63抑制后的死亡是否依赖于P53或相关基因P73的完整功能，以及哪种P63亚型(S)提供了生存效应。其次，在HNSCC细胞中，将使用p63特异性siRNA之后的表达谱来确定介导p63肿瘤相关效应的下游基因。为了确定体内可能的p63靶点，从MGH/MEEI肿瘤库中显微解剖的原发肿瘤将被用于将p63水平与原发HNSCC样本中的全基因组表达谱相关联。将p63 siRNA调控的基因与p63在原发肿瘤中表达一致的基因进行比较，应该可以识别出最具生物学意义的p63靶点。第三，确认的p63靶点的潜在治疗相关性将直接在HNSCC中使用siRNA方法进行测试。总之，这些研究将确定p63通路在肿瘤发生中的相关性，并将确定潜在的新的治疗靶点，以介导p63在HNSCC中的关键生存效应。

DESCRIPTION (provided by applicant): The goal of this proposal is to use genomic approaches to identify new therapeutic targets for head and neck squamous cell carcinoma (HNSCC), by defining the p63 pathway in tumors in vivo. The p53 family member p63 is overexpressed in a majority of primary HNSCC tumors and is essential for epithelial precursor development in vivo, suggesting a role for this gene in tumorigenesis. Our recent data using small inhibitory RNA (siRNA) targeted against specific p63 isoforms demonstrates that loss of p63 expression induces apoptosis in HNSCC cells that overexpress p63. In contrast, p63 inhibition has no effect on survival of normal keratinocytes or of tumor cells that do not express p63. To date, the downstream mechanisms of p63 remain poorly characterized. Therefore it will first be determined whether death following p63 inhibition depends on intact function of p53 or the related gene p73, and which p63 isoform(s) provide the survival effect. Second, the downstream genes that mediate tumor-associated effects of p63 will be identified using expression profiling following p63-specific siRNA in HNSCC cells. To confirm putative p63 targets in vivo, microdissected primary tumors from the MGH/MEEI tumor bank will be used to correlate p63 levels with genome-wide expression profiles in primary HNSCC specimens. Comparison of genes regulated following p63 siRNA to genes expressed coincident with p63 in primary tumors should allow identification of the most biologically relevant p63 targets. Third, the potential therapeutic relevance of the confirmed p63 targets will be tested directly in HNSCC using an siRNA approach. Together these studies will define the relevance of the p63 pathway in tumorigenesis, and will identify potential new therapeutic targets that mediate the critical survival effect of p63 in HNSCC.