Cancer Research Program, McGill University Health Centre-Research Institute, 1001 Decarie Boulevard, Montreal, Quebec, H4A 3J1, Canada.
Department of Experimental Surgery, Faculty of Medicine, McGill University, 845 Rue Sherbrooke O, Montreal, Quebec, H3A 0G4, Canada.
J Exp Clin Cancer Res. 2017 Aug 30;36(1):113. doi: 10.1186/s13046-017-0587-0.
Horizontal transfer of malignant traits from the primary tumor to distant organs, through blood circulating factors, has recently become a thoroughly studied metastatic pathway to explain cancer dissemination. Recently, we reported that oncosuppressor gene-mutated human cells undergo malignant transformation when exposed to cancer patients' sera. We also observed that oncosuppressor mutated cells would show an increased uptake of cancer-derived exosomes and we suggested that oncosuppressor genes might protect the integrity of the cell genome by blocking integration of cancer-derived exosomes. In the present study, we tested the hypothesis that cancer patients' sera-derived exosomes might be responsible for the malignant transformation of target cells and that oncosuppressor mutation would promote their increased uptake. We also sought to unveil the mechanisms behind the hypothesized phenomena.
We used human BRCA1 knockout (BRCA1-KO) fibroblasts as target cells. Cells were treated in vitro with cancer patients' sera or cancer patients' sera-derived exosomes. Treated cells were injected into NOD-SCID mice. Immunohistochemical analyses were performed to determine the differentiation state of the xenotransplants. Mass spectrometry analyses of proteins from cancer exosomes and the BRCA1-KO fibroblasts' membrane were performed to investigate possible de novo expression of molecules involved in vesicles uptake. Blocking of the identified molecules in vitro was performed and in vivo experiments were conducted to confirm the role of these molecules in the malignant transformation carried out by cancer-derived exosomes.
Cells treated with exosomes isolated from cancer patients' sera underwent malignant transformation and formed tumors when transplanted into immunodeficient mice. Histological analyses showed that the tumors were carcinomas that differentiated into the same lineage of the primary tumors of blood donors. Oncosuppressor mutation promoted the de novo expression, on the plasma membrane of target cells, of receptors, responsible for the increased uptake of cancer-derived exosomes. The selective blocking of these receptors inhibited the horizontal transfer of malignant traits.
These findings strengthen the hypothesis that oncogenic factors transferred via circulating cancer exosomes, induce malignant transformation of target cells even at distance. Oncosuppressor genes might protect the integrity of the cell genome by inhibiting the uptake of cancer-derived exosomes.
恶性特征从原发肿瘤通过血液循环因子转移到远处器官，最近已成为一种被深入研究的转移途径，用以解释癌症的扩散。最近，我们报道称，暴露于癌症患者血清中的抑癌基因突变更易发生恶性转化的人类细胞。我们还观察到，抑癌基因突变更易发生的细胞会增加对源自癌症的外泌体的摄取，我们推测抑癌基因可能通过阻断源自癌症的外泌体的整合来保护细胞基因组的完整性。在本研究中，我们检验了以下假说，即癌症患者血清衍生的外泌体可能导致靶细胞的恶性转化，而抑癌基因突变会促进其摄取增加。我们还试图揭示假设现象背后的机制。
我们使用人 BRCA1 敲除（BRCA1-KO）成纤维细胞作为靶细胞。将细胞在体外用癌症患者的血清或癌症患者的血清衍生的外泌体处理。处理后的细胞被注射到 NOD-SCID 小鼠中。进行免疫组织化学分析以确定异种移植物的分化状态。对源自癌症外泌体和 BRCA1-KO 成纤维细胞膜的蛋白质进行质谱分析，以研究参与囊泡摄取的新表达的分子。在体外进行鉴定的分子的阻断，并进行体内实验以确认这些分子在源自癌症的外泌体所进行的恶性转化中的作用。
用源自癌症患者血清的外泌体处理的细胞在移植到免疫缺陷小鼠后发生恶性转化并形成肿瘤。组织学分析表明，肿瘤是分化为供体血液肿瘤相同谱系的癌。抑癌基因突变促进了靶细胞的质膜上，负责增加摄取源自癌症的外泌体的受体的新表达。这些受体的选择性阻断抑制了恶性特征的横向转移。
这些发现加强了这样的假说，即通过循环的癌症外泌体传递的致癌因子，即使在远处也会诱导靶细胞的恶性转化。抑癌基因可能通过抑制源自癌症的外泌体的摄取来保护细胞基因组的完整性。
