Expression of a truncated form of the c-kit tyrosine kinase receptor and activation of Src kinase in human prostatic cancer
Expression of a truncated form of the c-kit tyrosine kinase receptor and activation of Src kinase in human prostatic cancer
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DOI：
10.1016/s0002-9440(10)63212-9
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发表时间：
2004-04-01
影响因子：
6
通讯作者：
Sette, C
中科院分区：
文献类型：
--
作者：
Paronetto, MP;Farini, D;Sette, C
c-Kit酪氨酸激酶受体的截断形式，最初在小鼠单倍体生殖细胞中发现，在各种来源的人类癌细胞系中异常表达。这种替代转录物起源于人类c-kit基因的第15内含子。我们之前已经证明，携带精子的小鼠截断c-Kit （tr-Kit）在转染细胞和小鼠卵母细胞中都是src家族酪氨酸激酶的强激活剂。在本工作中，我们报道了人tr-Kit mRNA和蛋白在LNCaP前列腺癌细胞中表达。我们在人类c-kit基因的第15和第16内含子中发现了两个与小鼠c-kit基因的第16内含子中精子特异性tr-Kit启动子序列同源的区域。我们还发现LNCaP细胞中的核因子与小鼠tr-Kit启动子的离散序列结合。此外，对23例原发性前列腺癌的Western blot分析表明，tr-Kit在28%的较不晚期肿瘤（Gleason分级4至6）和66%的较晚期肿瘤（Gleason分级7至9）中表达，而在良性前列腺增生中不表达。对从LNCaP细胞和肿瘤组织中扩增的c-Kit的cDNA进行测序，证实在前列腺癌细胞中存在人类c-Kit第15内含子的转录物。我们还发现，与tr-Kit阴性的PC3细胞或前列腺肿瘤相比，表达tr-Kit的LNCaP细胞和前列腺肿瘤具有更高水平的磷酸化/活化Src，并且在PC3细胞中转染tr-Kit可导致Src活性急剧增加。有趣的是，我们发现Sam68（一种在有丝分裂中被Src磷酸化的rna结合蛋白）仅在表达tr-Kit的前列腺肿瘤中被磷酸化。事实上，在分析的表达tr-Kit的所有3个7至9级肿瘤中，都观察到Src的激活和Sam68的磷酸化。我们的数据首次描述了原发肿瘤中存在截断的c-Kit蛋白，并显示了tr-Kit表达与Src途径在疾病晚期的激活之间的相关性。因此，这些结果可能为阐明前列腺细胞肿瘤转化的新途径铺平道路。
A truncated form of the c-Kit tyrosine kinase receptor, originally identified in mouse haploid germ cells, is aberrantly expressed in human cancer cell lines of various origin. This alternative transcript originates in the 15th intron of the human c-kit gene. We have previously demonstrated that sperm-carried mouse truncated c-Kit (tr-Kit) is a strong activator of the Src-family tyrosine kinases both in transfected cells and in mouse oocytes. In the present work, we report that human tr-Kit mRNA and protein are expressed in LNCaP prostatic cancer cells. We have identified two regions in the 15th and 16th introns of the human c-kit gene that show homology with sequences in the spermatid-specific tr-Kit promoter within the 16th intron of mouse c-kit. We also show that nuclear factors present in LNCaP cells bind to discrete sequences of the mouse tr-Kit promoter. Moreover, Western blot analysis of 23 primary prostate cancers indicated that tr-Kit was expressed in similar to28% of the tumors at less advanced stages (Gleason grade 4 to 6) and in 66% of those at more advanced stages (Gleason grade 7 to 9), whereas it was not expressed in benign prostatic hypertrophies. Sequencing of the cDNA for the truncated c-Kit, amplified from both LNCaP cells and neoplastic tissues, confirmed the existence in prostate cancer cells of a transcript arising from the 15th intron of human c-kit. We also show that tr-Kit-expressing LNCaP cells and prostatic tumors have higher levels of phosphorylated/activated Src than tr-Kit-negative PC3 cells or prostatic tumors, and that transfection of tr-Kit in PC3 cells caused a dramatic increase in Src activity. interestingly, we found that Sam68, a RNA-binding protein phosphorylated by Src in mitosis, is phosphorylated only in prostate tumors expressing tr-Kit. Indeed, both activation of Src and phosphorylation of Sam68 were observed in all of the three grade 7 to 9 tumors analyzed that expressed tr-Kit. Our data describe for the first time the existence of a truncated c-Kit protein in primary tumors and show a correlation between tr-Kit expression and activation of the Src pathway in the advanced stages of the disease. Thus, these results might pave the way for the elucidation of a novel pathway in neoplastic transformation of prostate cells.