Frame K L, Patton K, Reed M J, Ghilchik M W, Parish D C
Unit of Metabolic Medicine, St Mary's Hospital Medical School, Imperial College of Science, Technology & Medicine, London, UK.
Br J Cancer. 1996 Sep;74(5):807-13. doi: 10.1038/bjc.1996.440.
Palpable breast cysts with an apocrine epithelial lining (type 1) are reported to be associated with a higher risk of developing breast cancer. The composition of breast cyst fluid (BCF) might include those factors involved in this increased risk. In this study peptidase activities that were active against the substrate [125I]metenkephalin-Arg-Phe were detected in BCF. The products were identified by reversed phase high-performance liquid chromatography (HPLC) as [125I]Tyr-Gly-Gly and [125I]Met-enkephalin. This proteolysis was not inhibited by PCMB, pepstatin A, leupeptin or aprotinin but was by EDTA, showing that the activity was due to metalloproteases. The production of [125I]Try-Gly-Gly was inhibited by phosphoramidon and thiorphan, whereas that of [125I]met-enkephalin was inhibited by captopril and Bothrops jararaca peptide, indicating that these activities are enkephalinase and angiotensin-converting enzyme (ACE) respectively. A fluorometric assay for ACE demonstrated that ACE levels are significantly higher in type 2 BCF than in type 1 BCF (30.8 vs 6.1 nmol hr-1 10 microliters-1, P < 0.001). As the increased risk of cancer is linked to type 1 cysts it is possible that higher levels of peptidase in type 2 BCF reflect a protective environment in the breast in which mitogenic peptide growth factors are neutralised by proteolysis.
据报道，具有顶泌汗腺上皮内衬的可触及乳腺囊肿（1型）与患乳腺癌的较高风险相关。乳腺囊肿液（BCF）的成分可能包括与这种风险增加相关的那些因素。在本研究中，在BCF中检测到了对底物[125I]甲硫脑啡肽-精氨酸-苯丙氨酸有活性的肽酶活性。通过反相高效液相色谱（HPLC）将产物鉴定为[125I]酪氨酸-甘氨酸-甘氨酸和[125I]甲硫脑啡肽。这种蛋白水解作用不受对氯汞苯甲酸、胃蛋白酶抑制剂A、亮抑酶肽或抑肽酶的抑制，但受乙二胺四乙酸（EDTA）抑制，表明该活性是由金属蛋白酶引起的。[125I]酪氨酸-甘氨酸-甘氨酸的产生受到磷酰胺和硫磷酰胺的抑制，而[125I]甲硫脑啡肽的产生受到卡托普利和矛头蝮蛇肽的抑制，表明这些活性分别是脑啡肽酶和血管紧张素转换酶（ACE）。一种用于ACE的荧光测定法表明，2型BCF中的ACE水平显著高于1型BCF（30.8对6.1纳摩尔·小时-1·10微升-1，P<0.001）。由于癌症风险增加与1型囊肿有关，因此2型BCF中较高水平的肽酶可能反映了乳腺中的一种保护环境，在这种环境中，有丝分裂原性肽生长因子通过蛋白水解作用被中和。
