Dual Blockade of IGF1R and MEK synergistically inhibits pediatric cancers

与LASP合作，我们在小鼠ras突变横纹肌肉瘤异种移植模型中进行了曲美替尼和甘尼单抗的体内研究。我们发现，与单独使用任何一种药物相比，曲美替尼和甘尼单抗联合使用提供了生存优势，也与标准护理化疗药物长春新碱相比。我们还发现，这种组合在肿瘤内提供了预期的药效学效应，即与对照组相比，使用曲美替尼和甘尼单抗联合治疗的肿瘤中ERK磷酸化和IGF1R表达降低。我们还发现，人类ras突变横纹肌肉瘤细胞系SMS-CTR对曲美替尼和甘尼单抗联合治疗有特殊反应。为了确定为什么SMS-CTR对这种组合反应如此之好，我们发现在ras突变的横纹肌肉瘤细胞系中，SMS-CTR具有最高的IGF1R表达。我们的目标是确定共同靶向RAS-RAF-MEK-ERK途径和IGF1R-IRS1/2- pi3k - akt - mtor途径的机制，这些途径将在不具有高IGF1R表达的细胞系中有效，包括针对IGF1R配体、IGF1/2和IRS1/2抑制剂的特异性单克隆抗体。这项工作目前正在进行中。重要的是，我们还在几种ras突变RMS的PDX模型中测试了曲美替尼和甘尼单抗的联合治疗。我们在NRAS和HRAS驱动的细胞系异种移植物和PDX模型中显示了这种组合的有效性。对该组合具有相对内在抗性的模型是PI3激酶通路基因发生改变的模型，要么是PIK3CA突变，要么是PTEN表达缺失。重要的是，在SMS-CTR细胞中敲低PTEN的表达赋予了对曲美替尼的抗性。这项研究发表在《临床癌症研究》杂志上。我们正在与CTEP和儿童肿瘤组讨论在儿科患者中启动曲美替尼和甘尼单抗的I/II期临床试验。我们还与ImmunityBio就研究者发起的单机构试验进行了讨论。不幸的是，ganitumab不再用于新的临床试验。我们也一直在与BI就xentuzumab（一种针对IGF1/2的单克隆抗体）进行讨论，但由于xentuzumab在成人恶性肿瘤中缺乏临床疗效，这些讨论也停滞了。为了促进这种组合的临床转化，我们正在评估曲美替尼/甘尼单抗在其他疾病组织学中的疗效。我们已经证明了曲美替尼/甘尼单抗在两种RAS突变的神经母细胞瘤细胞系异种移植物中的疗效，并且正在继续评估由非RAS本身的MAPK通路改变驱动的神经母细胞瘤模型中的联合治疗，以及由NF1或BRAF改变驱动的MPNST。在曲美替尼和甘尼单抗联合的动物研究过程中，我们创建了一个对曲美替尼耐药的SMS-CTR细胞系。我们目前正在确定该细胞系对曲美替尼的耐药机制。全外显子组测序和全转录组测序均未发现新的SNV或融合产生抗性。然而。基因表达和磷酸化蛋白质组学分析显示，这些细胞在对MEK抑制产生抗性的过程中调节Hippo和NF κ B途径。我们目前的工作旨在验证这些结果，并将结果扩展到其他抗MEK抑制剂的RMS细胞系。

In collaboration with LASP, we conducted an in vivo study of trametinib and ganitumab in mouse xenograft models of Ras-mutated rhabdomyosarcoma. We have found that the combination of trametinib and ganitumab provided a survival advantage compared to either agent alone, and also compared to a standard of care chemotherapeutic, vincristine. We also identified that this combination provided the expected pharmacodynamic effects within the tumors, i.e. ERK phosphorylation and IGF1R expression were decreased in tumors that were treated with the combination of trametinib and ganitumab as compared to controls. We also identified that the human Ras-mutated rhabdomyosarcoma cell line, SMS-CTR, is an exceptional responder to the combination of trametinib and ganitumab. To identify why SMS-CTR responds so well to this combination, we showed that of the Ras-mutated rhabdomyosarcoma cell lines, SMS-CTR has the highest expression of IGF1R. We aimed to identify mechanisms of co-targeting the RAS-RAF-MEK-ERK pathways and the IGF1R-IRS1/2-PI3K-AKT-mTOR pathways that would be effective in cell lines that do not have high IGF1R expression, including monoclonal antibodies specific for the ligand of IGF1R, IGF1/2, and an inhibitor of IRS1/2. This work is currently ongoing. Importantly, we have also tested the combination of trametinib and ganitumab in several PDX models of RAS-mutated RMS. We show the efficacy of the combination in cell line xenograft and PDX models driven by both NRAS and HRAS. The models with relative intrinsic resistance to the combination are models that also have an alteration in genes of the PI3 kinase pathway, either PIK3CA mutation or loss of expression of PTEN. Importantly, knockdown of PTEN expression in SMS-CTR cells confers resistance to trametinib. This work was published in Clinical Cancer Research. We were in discussions with CTEP and the Children's oncology group regarding the initiation of a phase I/II clinical trial of trametinib and ganitumab in pediatric patients. We were also in discussions with ImmunityBio regarding an investigator-initiated single institution trial. Unfortunately, ganitumab is no longer available for new clinical trials. We had also been in discussions with BI regarding xentuzumab, a monoclonal antibody specific for IGF1/2 but these talks also stalled due to the lack of clinical efficacy of xentuzumab in adult malignancies. To facilitate the clinical translation of this combination, we are evaluating the efficacy of trametinib/ganitumab in other disease histologies. We have shown the efficacy of trametinib/ganitumab in two cell line xenografts of RAS-mutated neuroblastoma, and are continuing to evaluate the combination in neuroblastoma models driven by alterations in the MAPK pathway that are not RAS itself, as well as in MPNST, driven by alterations in NF1 or BRAF. In the course of the animal study of the trametinib and ganitumab combination, we created an SMS-CTR cell line that is resistant to trametinib. We are currently in the process of identifying the mechanism of resistance to trametinib in this cell line. Whole exome sequencing and whole transcriptome sequencing did not reveal a new SNV or fusion responsible for the resistance. However. gene expression and phosphoproteomic analysis have revealed that these cells modulate the Hippo and NF kappa B pathways in developing resistance to MEK inhibition. Our current work is aimed at validating these results and extending the results to other MEK inhibitor resistant RMS cell lines.