Refolding Mutant p53: A Strategy for Cancer Prevention in Li-Fraumeni Syndrome

项目摘要--项目1 Li-Fraumeni综合征(LFS)，一种发生在生殖系突变杂合子携带者中的遗传性疾病 在TP53中，与许多不同起源组织的早发性癌症有关。因为TP53已经被 经过如此广泛的研究，存在着在肿瘤形成之前对LFS进行早期干预的独特机会 个人。 无论是生殖系还是体细胞，大多数与癌症相关的TP53突变都是错义突变， 干扰P53‘S结合脱氧核糖核酸的能力。虽然其中一些突变映射到与DNA直接接触的残基， 许多人并不这样认为。相反，这些突变降低了P53‘S的热力学稳定性，从而使数量不足的 (突变体)P53正确折叠：这会导致功能丧失(LOF)。这些突变中的许多也赋予了 致癌功能获得(GOF)活性。在Li-Fraumeni人中，有证据表明，最早的 癌前病变出现的阶段，以及这些病变进展为癌症的阶段，源于突变 P53‘S GOF活性。 Karanicolas实验室正在进行的工作集中在开发结合和稳定折叠的药物 突变型P53的构象，以直接纠正LOF和GOF活性背后的错义缺陷。 这些“再折叠药物”旨在结合蛋白质表面的一个区域，该区域与所有的p53‘S’是分开的 最常见的突变，因此，无论特定突变如何，都可以应用相同的药物。我们有 在不同的癌细胞系中测试了这些药物，这些癌细胞在TP53中存在许多不同的突变。通过这些 研究证实，这些重折叠药物包括：1)恢复突变型p53的LOF，2)恢复突变型 P53‘S GOF活性。 我们提议的项目有三个目标。首先，我们将定义突变集 这是LFS个人的特点，可以通过这类新的特工来解决。第二，我们将优化我们的 目前最好的制剂，以提高其在动物研究中的预期安全性和有效性。第三，我们将测试它的安全性 在LFS个体中常见的TP53突变杂合子在小鼠身上产生的药剂，以及疗效 在p53介导的鳞癌小鼠模型中，该模型提供了从 从癌症前期到癌症。这些研究的成功完成将成为重要的概念证明 P53复性试剂有望成为预防和早期阻断癌症的新药 LFS个人。

PROJECT SUMMARY - PROJECT 1 Li-Fraumeni syndrome (LFS), an inherited disorder arising in heterozygous carriers of germline mutations in TP53, is associated with early-onset cancers in many different tissues of origin. Because TP53 has been studied so extensively, a unique opportunity exists to intervene early – prior to tumor formation – in LFS individuals. Whether germline or somatic, most cancer-associated TP53 mutations are missense mutations that disrupt p53’s ability to bind DNA. While some of these mutations map to residues in direct contact with DNA, many do not. Rather, these mutations reduce p53’s thermodynamic stability, so that an insufficient amount of (mutant) p53 is correctly folded: this leads to loss of function (LOF). Many of these mutations also confer oncogenic gain of function (GOF) activities. Among Li-Fraumeni individuals, evidence suggests that the earliest stages in the emergence of precancerous lesions, and progression of these lesions to cancer, derive from mutant p53’s GOF activities. Ongoing work in the Karanicolas lab focuses on developing drugs that bind and stabilize the folded conformation of mutant p53, to directly correct the missense defects that underlie the LOF and GOF activities. These “refolder drugs” are designed to bind a region on the protein surface that is separate from all of p53’s most common mutations, so that the same drug can be applied irrespective of the specific mutation. We have tested these drugs in diverse cancer cell lines harboring many different mutations in TP53. Through these studies, we have confirmed that these refolder drugs both: 1) restore LOF from mutant p53, and 2) revert mutant p53’s GOF activities. The objectives of our proposed project are three-fold. First, we will define the set of mutations characteristic of LFS individuals that can be addressed by this new class of agents. Second, we will optimize our current “best” agent to enhance its expected safety and efficacy in animal studies. Third, we will test the safety of the resulting agents’ in mice heterozygous for a TP53 mutation seen frequently in LFS individuals, and efficacy in a mouse model of p53-mediated squamous carcinoma that provides clear milestones of the progression from precancer to cancer. Successful completion of these studies will serve as important proof-of-concept that these p53 refolding agents hold the potential to become new drugs for prevention and early interception of cancer in LFS individuals.