Williams Simon A, Merchant Rosemina F, Garrett-Mayer Elizabeth, Isaacs John T, Buckley J Thomas, Denmeade Samuel R
Department of Oncology, The Johns Hopkins University School of Medicine, Baltimore, MD 21231, USA.
J Natl Cancer Inst. 2007 Mar 7;99(5):376-85. doi: 10.1093/jnci/djk065.
Most men will develop prostatic abnormalities, such as benign prostatic hyperplasia (BPH) or prostate cancer, as they age. Prostate-specific antigen (PSA) is a serine protease that is secreted at high levels by the normal and diseased prostate. Therapies that are activated by PSA may prove effective in treating prostatic malignancies.
We modified proaerolysin (PA), the inactive precursor of a bacterial cytolytic pore-forming protein, to produce a PSA-activated protoxin (PRX302). The viability of the prostate adenocarcinoma cell lines LNCaP, PC-3, CWR22H, and DU145 and the bladder cancer cell line TSU after treatment with PA or PRX302 in the presence or absence of purified PSA was assayed. Mice carrying xenograft tumors derived from LNCaP, CWR22H, or TSU cells were treated with intratumoral injection of PA or PRX302, and tumor size was monitored. To test the safety of PRX302, we administered it into the PSA-secreting prostate glands of cynomolgus monkeys. All statistical tests were two-sided.
Native PA was highly toxic in vitro but had no tumor-specific effects in vitro or in vivo. Picomolar concentrations of PRX302 led to PSA-dependent decreases in cell viability in vitro (PRX302 versus PRX302 + PSA: DU145 cells, mean viability = 78.7% versus mean = 1.6%, difference = 77.1%, 95% confidence interval [CI] = 70.6% to 86.1%; P<.001; TSU cells, mean = 100.2% versus mean = 1.4%, difference = 98.8%, 95% CI = 96.4% to 104.0%; P<.001). Single intratumoral injections of PRX302 produced substantial and often complete regression of PSA-secreting human prostate cancer xenografts (5 microg dose, complete regression in 6 of 26 mice bearing LNCap or CWR22H xenografts [23%]; 10 microg dose, complete regression in 10 of 26 mice [38.5%]) but not PSA-null bladder cancer xenografts. The prostates of cynomolgus monkeys injected with a single dose of PRX302 displayed extensive but organ-confined damage, with no toxicity to neighboring organs or general morbidity.
Our observations demonstrate the potential safe and effective intraprostatic application of this engineered protoxin.
大多数男性随着年龄增长会出现前列腺异常,如良性前列腺增生(BPH)或前列腺癌。前列腺特异性抗原(PSA)是一种丝氨酸蛋白酶,正常和患病的前列腺都会大量分泌。由PSA激活的疗法可能在治疗前列腺恶性肿瘤方面被证明是有效的。
我们对细菌溶细胞成孔蛋白的无活性前体原气单胞菌溶素(PA)进行了改造,以产生一种PSA激活的原毒素(PRX302)。在有或没有纯化PSA的情况下,用PA或PRX302处理后,测定前列腺腺癌细胞系LNCaP、PC-3、CWR22H和DU145以及膀胱癌细胞系TSU的活力。对携带源自LNCaP、CWR22H或TSU细胞的异种移植肿瘤的小鼠进行瘤内注射PA或PRX302,并监测肿瘤大小。为了测试PRX302的安全性,我们将其注射到食蟹猴分泌PSA的前列腺中。所有统计检验均为双侧检验。
天然PA在体外具有高毒性,但在体外或体内均无肿瘤特异性作用。皮摩尔浓度的PRX302导致体外细胞活力呈PSA依赖性下降(PRX302与PRX302 + PSA相比:DU145细胞,平均活力 = 78.7% 对平均 = 1.6%,差异 = 77.1%,95% 置信区间 [CI] = 70.6% 至 86.1%;P <.001;TSU细胞,平均 = 100.2% 对平均 = 1.4%,差异 = 98.8%,95% CI = 96.4% 至 104.0%;P <.001)。单次瘤内注射PRX302可使分泌PSA的人前列腺癌异种移植瘤显著且常常完全消退(5微克剂量,26只携带LNCap或CWR22H异种移植瘤的小鼠中有6只完全消退 [23%];10微克剂量,26只小鼠中有10只完全消退 [38.5%]),但对不分泌PSA的膀胱癌细胞异种移植瘤无效。单次注射PRX302的食蟹猴前列腺显示出广泛但局限于器官的损伤,对邻近器官无毒性,也无全身发病率。
我们的观察结果表明这种工程化原毒素在前列腺内的应用具有潜在的安全性和有效性。