Strzemecki Damian, Guzowska Magdalena, Grieb Paweł
Department of Experimental Pharmacology, Mossakowski Medical Research Centre, Polish Academy of Sciences, 5 Pawińskiego Str., Warsaw, 02-106 Poland.
Cell Mol Biol Lett. 2017 May 18;22:9. doi: 10.1186/s11658-017-0039-z. eCollection 2017.
The gene that encodes tumor protein p53, , is mutated or silenced in most human cancers and is recognized as one of the most important cancer drivers. Homozygotic 53 knockout mice, which develop lethal cancers early in their lives, are already used in cancer prevention studies, and now 53 knockout rats have also been generated. This study assessed feasibility of using homozygous knockout rats to evaluate the possible outcome of cancer chemoprevention.
A small colony of 53 knockout rats with a Wistar strain genetic background was initiated and maintained in the animal house at our institution. heterozygotic females were bred with homozygous knockout males to obtain a surplus of knockout homozygotes. To evaluate the reproducibility of their lifespan, 4 groups of homozygous knockout male rats born during consecutive quarters of the year were kept behind a sanitary barrier in a controlled environment until they reached a moribund state. Their individual lifespan data were used to construct quarterly survival curves.
The four consecutive quarterly survival curves were highly reproducible. They were combined into a single "master" curve for use as a reference in intervention studies. The average lifespan of untreated male homozygous knockout rats was normally distributed, with a median of 133 days. Sample size vs. effect calculations revealed that confirming a 20% and 30% increase in the lifespan would respectively require a sample size of 18 and 9 animals (when assessed using the -test with a power of 80% and alpha set at 0.05). As an example, the homozygous knockout rat model was used to test the chemopreventive properties of carnosine, a dipeptide with suspected anticancer properties possibly involving modulation of the mTOR pathway. The result was negative.
Further evaluation of the homozygous knockout male rat colony is required before it can be confirmed as a viable tool for assessing new methods of cancer prevention or treatment.
编码肿瘤蛋白p53的基因在大多数人类癌症中发生突变或沉默，被认为是最重要的癌症驱动因素之一。纯合p53基因敲除小鼠在生命早期就会发生致命癌症，已被用于癌症预防研究，现在也已培育出p53基因敲除大鼠。本研究评估了使用纯合p53基因敲除大鼠评估癌症化学预防可能结果的可行性。
在我们机构的动物房建立并维持了一小群具有Wistar品系遗传背景的p53基因敲除大鼠。将p53杂合雌性大鼠与p53纯合基因敲除雄性大鼠交配，以获得多余的基因敲除纯合子。为了评估其寿命的可重复性，将在一年中连续四个季度出生的4组p53纯合基因敲除雄性大鼠置于可控环境中的卫生屏障后，直至其处于濒死状态。它们的个体寿命数据用于构建季度生存曲线。
四条连续的季度生存曲线具有高度可重复性。它们被合并成一条单一的“主”曲线，用作干预研究的参考。未经治疗的雄性p53纯合基因敲除大鼠的平均寿命呈正态分布，中位数为133天。样本量与效应计算表明，要确认寿命分别增加20%和30%，分别需要18只和9只动物的样本量（使用功效为80%且α设定为0.05的t检验进行评估时）。例如，p53纯合基因敲除大鼠模型用于测试肌肽的化学预防特性，肌肽是一种二肽，具有可能涉及调节mTOR途径的疑似抗癌特性。结果为阴性。
在确认p53纯合基因敲除雄性大鼠群体可作为评估癌症预防或治疗新方法的可行工具之前，需要对其进行进一步评估。
