Eswaraka Jeetendra, Giddabasappa Anand, Han Guangzhou, Lalwani Kush, Eisele Koleen, Feng Zheng, Affolter Timothy, Christensen James, Li Gang
Global Science and Technology (WCM), Pfizer Global Research and Development, 10724 Science Center Dr, San Diego, CA 92121, USA.
BMC Cancer. 2014 Oct 2;14:742. doi: 10.1186/1471-2407-14-742.
Castration resistant prostate cancer (CRPC) is a leading cause of cancer-related deaths in men. The primary cause of mortality and morbidity in patients is bone metastases and remodeling resulting in osteoblastic and osteolytic lesions. Recently, cabozantinib, a multi-kinase inhibitor (VEGFR2 and c-MET inhibitor), was shown to have efficacy on bone lesions in patients. In this study we tested multi-kinase inhibitors: axitinib (VEGFR inhibitor) and crizotinib (c-MET inhibitor) in a combination trial in mice models.
VCaP-Luc cells were grown as subcutaneous implants in intact and castrated NOD-SCID-gamma (NSG) mice to confirm the androgen dependency. For bone metastasis model two cohorts of NSG mice (castrated and intact) received orthotopic injection of VCaP-Luc cells into the bone marrow cavity of left tibia. Mice were monitored weekly for tumor growth using bioluminescence imaging. Animals were randomized into 4 groups based on the tumor bioluminescence signal: vehicle, crizotinib alone, axitinib alone, crizotinib and axitinib in combination. Animals were imaged weekly by in vivo 2-D X-ray imaging to monitor bone remodeling. At the end of the study animals were euthanized and both tibias were extracted for ex vivo high-resolution 3-D micro-computed tomography (μCT) imaging.
Subcutaneous model showed that androgen stimulation may be helpful but not essential for the growth of VCaP-Luc cells. VCaP-Luc cells grown intra-tibially in intact animals caused extensive remodeling of bone with mixed osteoblastic (bone formation) and osteolytic (bone matrix dissolution) lesions. The osteoblastic lesions were predominant and at times extended beyond the tibial shaft into the surrounding tissue. In contrast, only osteolytic lesions were prominent throughout the study in castrated animals. Treatment with crizotinib alone reduced the osteolytic lesions in castrated animals. Axitinib alone reduced the osteoblastic lesions in the intact animals. Combination therapy with axitinib and crizotinib remarkably inhibited the tibial remodeling by VCaP-Luc cells which resulted in a significant reduction of both osteoblastic and osteolytic lesions.
Our data show that combined inhibition of c-MET and VEGFR can be beneficial for treatment of metastatic bone disease in CRPC and that the drugs act on two different stages of the disease.
去势抵抗性前列腺癌（CRPC）是男性癌症相关死亡的主要原因。患者死亡和发病的主要原因是骨转移和重塑，导致成骨和溶骨性病变。最近，卡博替尼，一种多激酶抑制剂（VEGFR2和c-MET抑制剂），已显示对患者的骨病变有效。在本研究中，我们在小鼠模型的联合试验中测试了多激酶抑制剂：阿昔替尼（VEGFR抑制剂）和克唑替尼（c-MET抑制剂）。
将VCaP-Luc细胞作为皮下植入物在完整和去势的NOD-SCID-γ（NSG）小鼠中培养，以确认雄激素依赖性。对于骨转移模型，两组NSG小鼠（去势和完整）接受将VCaP-Luc细胞原位注射到左胫骨骨髓腔中。每周使用生物发光成像监测小鼠的肿瘤生长。根据肿瘤生物发光信号将动物随机分为4组：溶剂对照组、单独使用克唑替尼组、单独使用阿昔替尼组、克唑替尼和阿昔替尼联合组。每周通过体内二维X射线成像对动物进行成像，以监测骨重塑。在研究结束时，对动物实施安乐死并取出双侧胫骨用于体外高分辨率三维微计算机断层扫描（μCT）成像。
皮下模型表明雄激素刺激可能有助于但并非VCaP-Luc细胞生长所必需。在完整动物的胫骨内生长的VCaP-Luc细胞导致广泛的骨重塑，伴有混合性成骨（骨形成）和溶骨（骨基质溶解）病变。成骨病变占主导，有时会延伸至胫骨干以外进入周围组织。相比之下，在整个研究过程中，去势动物中仅溶骨病变较为突出。单独使用克唑替尼治疗可减少去势动物中的溶骨病变。单独使用阿昔替尼可减少完整动物中的成骨病变。阿昔替尼和克唑替尼联合治疗显著抑制了VCaP-Luc细胞引起的胫骨重塑，导致成骨和溶骨病变均显著减少。
我们的数据表明，联合抑制c-MET和VEGFR可能有利于治疗CRPC中的转移性骨病，并且这些药物作用于疾病的两个不同阶段。
