良性前列腺增生的前列腺液中低相对分子质量前列腺特异抗原及乳铁蛋白的表达

Identification of low-molecular weight prostate-specific antigen(PSA) and lactoferrin in the prostatic secretion of benign prostatic hyperplasia

目的：检测良性前列腺增生患者和正常男性的前列腺液中低相对分子质量前列腺特异抗原（1W-PSA）及乳铁蛋白的表达水平。方法：采用蛋白双向电泳的方法，对20例良性前列腺增生患者和20例正常男性前列腺液的蛋白表达进行检测，并通过质谱分析方法确定蛋白点的性质。随后采用Western blotting的方法来验证蛋白的表达水平。结果：在良性前列腺增生患者的前列腺液中发现了相对分子质量为10×10^3、等电点（pI）为8．5～9．3的蛋白点A和相对分子质量为35×10^3、pI为7～7．5的蛋白点B。进行质谱分析后确定、蛋白点A为1w-PSA，蛋白点B为乳铁蛋白（lactoferrin）。Western blotting检测进一步确定良性前列腺增生患者的前列腺液中有1w-PSA表达，而前列腺癌组织中和正常男性的前列腺液中未见1w-PSA的表达。另外，Western blotting检测还发现，良性前列腺增生患者前列腺液的乳铁蛋白表达水平高于正常男性，而前列腺癌组织中无乳铁蛋白的表达。结论：良性前列腺增生患者的前列腺液中有1w-PSA表达，而正常男性的前列腺液中未见1w-PSA表达，1w-PSA可能与良性前列腺增生的病理变化存在一定关联，或许可以作为良性前列腺增生的蛋白标志物。另外，良性前列腺增生患者前列腺液的乳铁蛋白表达水平增高，正常男性前列腺液的乳铁蛋白表达水平较低，而前列腺癌的乳铁蛋白表达缺失。

Objective： To investigate the expression of low-molecular-weight PSA （ 1w-PSA ） and lactoferrin in the expressed prostatic secretion （EPS） from both benign prostatic hyperplasia （BPH） and normal prostate. Methods： Forty human EPS samples obtained from 20 BPH patients and 20 normal males were subjected to two-dimensional gel electrophoresis （2-DE）. Mass spectrometry was performed to confirm the nature of the secreted proteins in EPS. Results： One uniquely expressed protein in BPH was detected and mass spectrometry determined its nature as 1w-PSA （ molecular weight 10×10^3 , pI 8.5 - 9.3 ）. More importantly, Western blotting analysis also revealed that lw-PSA detected in BPH-EPS, but was undetectable in BPH-free EPS. In addition, up-regulation of Lactoferrin （ molecular weight 35 ×10^3 , pI 7 - 7.5） in BPH-EPS, as compared with BPH-free EPS, was also observed. More interestingly, lactoferrin was absent in prostate cancer tissues. Conclusion： Our results indicate lw-PSA may be produced specifically by BPH epithelium and it has a potential to be used as a specific biological marker for the diagnosis of BPH. In addition, benign prostatic epithelium can produce more lactoferrin while prostate cancer tissues go without its lactoferrin secretion.