Combating Cetuximab Resistance in Colorectal Cancer

表皮生长因子受体(Egfr)是一种致癌受体酪氨酸激酶，是一种主要的治疗方法。 几种癌症的靶标。两种EGFR单抗用于治疗EGFR- 结直肠癌(CRC)阳性，包括西妥昔单抗(CTX)和Panitumab，其具有相同的 作用机制。不幸的是，对单抗的原始和获得性耐药非常常见： 只有10%-20%的患者有反应，通常持续3-12个月。当前抗击艾滋病的方法 抗性是将mAb与靶向补偿或改变下游信号的制剂(S)结合 分子(ErbB2、cMET、KRAS、BRAF和PIK3CA)，但这种方法的临床疗效尚不确定。 重要的是，我们发现hPEPDG278D，一个人肽酶D的重组酶失活突变体， 强烈抑制所有耐CTX的CRC细胞株的增殖，并沉默EGFR、ErbB2和 它们在这些细胞中的下游信号分子。我们的结果表明，EGFR和ErbB2是关键 抗CTX的CRC细胞的治疗靶点。我们最近显示：a)hPEPDG278D专门与 EGFR和ErbB2的胞外区，扰乱它们的信号单位，并通过 内吞作用，是一种新型的EGFR和ErbB2双重抑制剂；b)选择性地抑制癌细胞 在体外和体内过表达EGFR和/或ErbB2；c)在小鼠研究中没有显示出毒性。这个 我们建议的目标是进一步评估hPEPDG278D克服CTX耐药性的作用并证实 新的概念，即EGFR和ErbB2仍然是CTX耐药CRC细胞的关键治疗靶点。我们 假设hPEPDG278D通过抑制ErbB2和CTX不敏感来克服CTX耐药性 EGFR，并提出三个目标来检验这一假设。目的1是确定该药的治疗效果 HPEPDG278D体内抗CTX耐药的结直肠癌，使用原位肿瘤模型和患者- 衍生异种移植模型。致癌的ErbB3和ErbB4(其他EGFR成员)以及cMET也是 与结直肠癌对环磷酰胺耐药有关。目的2是研究hPEPDG278D是否间接抑制 ErbB3、ErbB4和cMET通过使用两个细胞系破坏它们与EGFR或ErbB2的异二聚化 除了靶向ErbB2外，hPEPDG278D还靶向CTX敏感和 -不敏感的EGFR。目的3是确定hPEPDG278D靶向CTX不敏感的机制 (突变或野生型)EGFR在相关的结直肠癌细胞系中的表达。总之，这是一个被广泛接受的概念 该领域认为，结直肠癌对CTX和其他EGFR抑制剂的耐药性主要是由于其他信号转导的激活 蛋白质(ErbB2、cMET、KRAS、BRAF或PI3K)。我们希望表明抵制的主要原因是 CTX是EGFR对CTX的不敏感以及ErbB2的过度表达；这一范式的影响- 转变对EGFR阳性癌症的翻译研究的概念应该是重要的。研究结果： 该项目还可能为hPEPDG278D治疗结直肠癌和其他癌症的临床评估奠定坚实的基础。

Epidermal growth factor receptor (EGFR), an oncogenic receptor tyrosine kinase, is a major therapeutic target in several types of cancers. Two EGFR monoclonal antibodies (mAbs) are used to treat EGFR- positive colorectal cancer (CRC), including cetuximab (CTX) and panitumumab, which have the same mechanism of action. Unfortunately, primary and acquired resistance to the mAbs is very common: response in only 10-20% patients and lasts typically for 3-12 months. Current approach to combating the resistance is to combine the mAb with agent(s) that targets compensatory or altered downstream signaling molecules (ErbB2, cMET, KRAS, BRAF and PIK3CA), but clinical efficacy of such approach is uncertain. Importantly, we found that hPEPDG278D, a recombinant enzymatically inactive mutant of human peptidase D, strongly inhibits the proliferation of all tested CTX-resistant CRC cell lines, and silences EGFR, ErbB2 and their downstream signaling molecules in these cells. Our results suggest that EGFR and ErbB2 are pivotal therapeutic targets in CTX-resistant CRC cells. We recently showed: a) hPEPDG278D specifically binds to the extracellular domain of EGFR and ErbB2, disrupts their signaling units and directs them for degradation via endocytosis, and therefore is a novel dual inhibitor of EGFR and ErbB2; b) it selectively inhibits cancer cells overexpressing EGFR and/or ErbB2 in vitro and in vivo; c) it does not show toxicities in mouse studies. The goal of our proposal is to further evaluate hPEPDG278D for overcoming CTX resistance and to substantiate the novel concept that EGFR and ErbB2 remain critical therapeutic targets in CTX-resistant CRC cells. We hypothesize that hPEPDG278D overcomes CTX resistance by suppressing both ErbB2 and CTX-insensitive EGFR, and propose three Aims to test the hypothesis. Aim 1 is to determine the therapeutic efficacy of hPEPDG278D against CTX-resistant CRC tumors in vivo, using both orthotoptic tumor models and patient- derived xenograft models. Oncogenic ErbB3 and ErbB4 (other EGFR members) as well as cMET are also implicated in CTX resistance in CRC. Aim 2 is to investigate whether hPEPDG278D indirectly suppresses ErbB3, ErbB4 and cMET by disrupting their heterodimerization with EGFR or ErbB2, using both cell lines and treated tumors from Aim 1. Besides targeting ErbB2, hPEPDG278D also targets both CTX-sensitive and -insensitive EGFR. Aim 3 is to determine the mechanisms by which hPEPDG278D targets CTX-insensitive (mutated or wild type) EGFR in relevant CRC cell lines. In summary, it is a widely accepted concept in the field that CRC resistance to CTX and other EGFR inhibitors results largely from activation of other signaling proteins (ErbB2, cMET, KRAS, BRAF or PI3K). We expect to show that the main reason for resistance to CTX is the insensitivity of EGFR to CTX along with ErbB2 overexpression; the impact of this paradigm- shifting concept on translational studies on EGFR-positive cancers should be significant. Findings from the project may also lay a solid foundation for clinical evaluation of hPEPDG278D against CRC and other cancers.