Sasaki Y, Takahashi T, Miyazaki H, Matsumoto A, Kato T, Nakamura K, Iho S, Okuno Y, Nakao K
Department of Medicine and Clinical Science, Kyoto University Graduate School of Medicine, Kyoto, Japan.
Blood. 1999 Sep 15;94(6):1952-60.
Thrombocytosis is occasionally seen in patients with carcinomas and has been assumed to be attributable to interleukin-6 or granulocyte-macrophage colony-stimulating factor produced by carcinoma cells. In this study, we clarified whether thrombopoietin (TPO) is involved in carcinoma-associated thrombocytosis. Expression of TPO mRNA was observed in the majority of 27 carcinoma cell lines as determined by reverse transcriptase-polymerase chain reaction (RT-PCR). There were 6 PCR products differing in size; sequence analysis showed the full-length TPO mRNA (TPO-1), 12- and 116-bp deleted variants (TPO-2 and TPO-3, respectively), and 3 novel isoforms (197- and 128-bp deleted forms and a 60-bp insert form of TPO-3; named TPO-4, TPO-5, and TPO-6, respectively). Of 27 lines, 24 expressed TPO-1 mRNA with various other isoforms. Culture supernatants of COS-1 cells transfected with TPO-5 or TPO-6 cDNA did not promote the proliferation of TPO-responsive cells, whereas Western blot analysis on the cell lysates demonstrated TPO-5 but not TPO-6 protein, suggesting poor extracellular secretion (TPO-5) or poor protein synthesis (TPO-6). TPO protein was detected in 10-fold concentrated culture supernatants of cells of these carcinoma lines, with a median concentration of 0.38 fmol/mL as evaluated by enzyme-linked immunosorbent assay. High blood TPO levels were observed with a median value of 3.46 fmol/mL (range, 0.34 to 8.67 fmol/mL) in patients with advanced carcinomas associated with thrombocytosis. These results indicate that thrombocytosis in patients with carcinomas might be caused, at least in part, by TPO produced by carcinoma cells.
血小板增多症偶尔可见于癌症患者，一般认为这是由癌细胞产生的白细胞介素-6或粒细胞巨噬细胞集落刺激因子所致。在本研究中，我们阐明了血小板生成素（TPO）是否与癌症相关的血小板增多症有关。通过逆转录聚合酶链反应（RT-PCR）测定，在27种癌细胞系中的大多数都观察到了TPO mRNA的表达。有6种大小不同的PCR产物；序列分析显示有全长TPO mRNA（TPO-1）、缺失12和116个碱基对的变体（分别为TPO-2和TPO-3），以及3种新的异构体（TPO-3缺失197和128个碱基对的形式以及一种插入60个碱基对的形式；分别命名为TPO-4、TPO-5和TPO-6）。在27个细胞系中，24个表达TPO-1 mRNA以及各种其他异构体。用TPO-5或TPO-6 cDNA转染的COS-1细胞的培养上清液并不能促进TPO反应性细胞的增殖，而对细胞裂解物进行的蛋白质印迹分析显示有TPO-5蛋白但没有TPO-6蛋白，这表明细胞外分泌不良（TPO-5）或蛋白质合成不良（TPO-6）。通过酶联免疫吸附测定法评估，在这些癌细胞系细胞的10倍浓缩培养上清液中检测到了TPO蛋白，中位浓度为0.38 fmol/mL。在伴有血小板增多症的晚期癌症患者中观察到高血TPO水平，中位值为3.46 fmol/mL（范围为0.34至8.67 fmol/mL）。这些结果表明，癌症患者的血小板增多症可能至少部分是由癌细胞产生的TPO所致。
