Russo J, Tay L K, Russo I H
Breast Cancer Res Treat. 1982;2(1):5-73. doi: 10.1007/BF01805718.
It has been demonstrated that in humans certain factors such as early menarche, late pregnancy, and nulliparity are associated with a higher risk of developing breast cancer, while early pregnancy acts as a protective factor. Induction of mammary cancer in rats by administration of the chemical carcinogen 7,12-dimethylbenz(a)anthracene reveals that the same factors influencing human breast cancer risk also affect the susceptibility of the rat mammary gland to the chemical carcinogen. Nulliparous rats and rats undergoing pregnancy interruption are more susceptible to developing carcinomas. This fact has been attributed to the incomplete differentiation of the gland at the time of carcinogen administration. Parous rats are resistant to the carcinogenic effect of DMBA, which is explained by the complete development of the gland attained during pregnancy and lactation. This development is manifested by the differentiation of terminal end buds into secretory units, which have a smaller proliferative compartment; the epithelial cells of these secretory units have a longer cell cycle, less avidity for binding DMBA, and possess a more efficient DNA excision repair capacity.
已经证明，在人类中，某些因素如初潮早、怀孕晚和未生育与患乳腺癌的风险较高相关，而早孕则是一种保护因素。通过给予化学致癌物7,12-二甲基苯并(a)蒽在大鼠中诱发乳腺癌表明，影响人类乳腺癌风险的相同因素也会影响大鼠乳腺对化学致癌物的易感性。未生育的大鼠和经历妊娠中断的大鼠更容易发生癌变。这一事实归因于在给予致癌物时腺体的不完全分化。经产大鼠对DMBA的致癌作用具有抗性，这可以通过妊娠和哺乳期腺体的完全发育来解释。这种发育表现为终末芽分化为分泌单位，这些分泌单位具有较小的增殖区室；这些分泌单位的上皮细胞具有较长的细胞周期，对结合DMBA的亲和力较低，并且具有更有效的DNA切除修复能力。
