Hassan Sara, Blick Tony, Wood Jack, Thompson Erik W, Williams Elizabeth D
Queensland University of Technology (QUT), Faculty of Health, School of Biomedical Sciences at Translational Research Institute (TRI), Brisbane, QLD, Australia.
Australian Prostate Cancer Research Centre, Queensland (APCRC-Q) and Queensland Bladder Cancer Initiative (QBCI), Brisbane, QLD, Australia.
Front Cell Dev Biol. 2022 Apr 13;10:858013. doi: 10.3389/fcell.2022.858013. eCollection 2022.
Castrate-resistant prostate cancer (CRPC) is the lethal form of prostate cancer. Epithelial mesenchymal plasticity (EMP) has been associated with disease progression to CRPC, and prostate cancer therapies targeting the androgen signalling axis, including androgen deprivation therapy (ADT), promote EMP. We explored effects of castration on EMP in the tumours and circulating tumour cells (CTCs) of patient-derived xenograft (PDX)-bearing castrated mice using human-specific RT-qPCR assays and immunocytochemistry. Expression of prostate epithelial cell marker KLK3 was below detection in most tumours from castrated mice (62%, 23/37 mice), consistent with its known up-regulation by androgens. Endpoint tumour size after castration varied significantly in a PDX model-specific pattern; while most tumours were castration-sensitive (BM18, LuCaP70), the majority of LuCaP105 tumours continued to grow following castration. By contrast, LuCaP96 PDX showed a mixed response to castration. CTCs were detected in 33% of LuCaP105, 43% of BM18, 47% of LuCaP70, and 54% of LuCaP96 castrated mice using mRNA measurement in plasma. When present, CTC numbers estimated using human expression ranged from 1 to 458 CTCs per ml blood, similar to our previous observations in non-castrated mice. In contrast to their non-castrated counterparts, there was no relationship between tumour size and CTC burden in castrated mice. Unsupervised hierarchical clustering of the gene expression profiles of CTCs collected from castrated and non-castrated mice revealed distinct CTC sub-groups within the pooled population that were classified as having mesenchymal, epithelial, or EMP hybrid gene expression profiles. The epithelial signature was only found in CTCs from non-castrated mice. Hybrid and mesenchymal signatures were detected in CTCs from both castrated and non-castrated mice, with an emphasis towards mesenchymal phenotypes in castrated mice. Post-castration serum PSA levels were either below detection or very low for all the CTC positive samples highlighting the potential usefulness of CTCs for disease monitoring after androgen ablation therapy. In summary, our study of castration effects on prostate cancer PDX CTCs showed that CTCs were often detected in the castrate setting, even in mice with no palpable tumours, and demonstrated the superior ability of CTCs to reveal residual disease over the conventional clinical biomarker serum PSA.
去势抵抗性前列腺癌（CRPC）是前列腺癌的致命形式。上皮-间质可塑性（EMP）与疾病进展至CRPC相关，而针对雄激素信号轴的前列腺癌治疗，包括雄激素剥夺疗法（ADT），会促进EMP。我们使用人特异性逆转录定量聚合酶链反应（RT-qPCR）检测和免疫细胞化学方法，探究了去势对携带患者来源异种移植瘤（PDX）的去势小鼠肿瘤和循环肿瘤细胞（CTC）中EMP的影响。在去势小鼠的大多数肿瘤中（62%，23/37只小鼠），前列腺上皮细胞标志物激肽释放酶3（KLK3）的表达低于检测水平，这与其已知的雄激素上调作用一致。去势后的终点肿瘤大小在PDX模型特异性模式中差异显著；虽然大多数肿瘤对去势敏感（BM18、LuCaP70），但大多数LuCaP105肿瘤在去势后继续生长。相比之下，LuCaP96 PDX对去势表现出混合反应。使用血浆mRNA测量法，在33%的LuCaP105、43%的BM18、47%的LuCaP70和54%的LuCaP96去势小鼠中检测到了CTC。当存在CTC时，使用人基因表达估计的CTC数量范围为每毫升血液1至458个CTC，这与我们之前在未去势小鼠中的观察结果相似。与未去势的对应小鼠相比，去势小鼠的肿瘤大小与CTC负荷之间没有关系。对从去势和未去势小鼠收集的CTC的基因表达谱进行无监督层次聚类分析，结果显示在合并群体中存在不同的CTC亚组，这些亚组被分类为具有间充质、上皮或EMP混合基因表达谱。上皮特征仅在未去势小鼠的CTC中发现。在去势和未去势小鼠的CTC中均检测到混合和间充质特征，且去势小鼠中更倾向于间充质表型。对于所有CTC阳性样本，去势后的血清前列腺特异性抗原（PSA）水平要么低于检测水平，要么非常低，这突出了CTC在雄激素消融治疗后疾病监测中的潜在用途。总之，我们对去势对前列腺癌PDX CTC影响的研究表明，即使在没有可触及肿瘤的小鼠中，去势情况下也经常能检测到CTC，并且证明了CTC在揭示残留疾病方面比传统临床生物标志物血清PSA具有更强的能力。
