Kobayashi Natália Cristina Ciufa, Noronha Samuel Marcos Ribeiro de
United Metropolitan Colleges, São Paulo, SP, Brazil.
Department of Allergy and Immunology, University of São Paulo, São Paulo, SP, Brazil.
Rev Assoc Med Bras (1992). 2015 Jan-Feb;61(1):86-93. doi: 10.1590/1806-9282.61.01.086. Epub 2015 Jan 1.
Many theories have been proposed to explain the origins of cancer. Currently, evidences show that not every tumor cell is capable of initiating a tumor. Only a small part of the cancer cells, called cancer stem cells (CSCs), can generate a tumor identical to the original one, when removed from human tumors and transplanted into immunosuppressed mice. The name given to these cells comes from the resemblance to normal stem cells, except for the fact that their ability to divide is infinite. These cells are also affected by their microenvironment. Many of the signaling pathways, such as Wnt, Notch and Hedgehog, are altered in this tumoral subpopulation, which also contributes to abnormal proliferation. Researchers have found several markers for CSCs; however, much remains to be studied, or perhaps a universal marker does not even exist, since they vary among tumor types and even from patient to patient. It was also found that cancer stem cells are resistant to radiotherapy and chemotherapy. This may explain the re-emergence of the disease, since they are not completely eliminated and minimal amounts of CSCs can repopulate a tumor. Once the diagnosis in the early stages greatly increases the chances of curing cancer, identifying CSCs in tumors is a goal for the development of more effective treatments. The objective of this article is to discuss the origin of cancer according to the theory of stem cell cancer, as well as its markers and therapies used for treatment.
人们提出了许多理论来解释癌症的起源。目前，有证据表明并非每个肿瘤细胞都能够引发肿瘤。只有一小部分癌细胞，即所谓的癌症干细胞（CSCs），当从人类肿瘤中取出并移植到免疫抑制小鼠体内时，能够产生与原始肿瘤相同的肿瘤。赋予这些细胞这个名称是因为它们与正常干细胞相似，只是它们的分裂能力是无限的。这些细胞也会受到其微环境的影响。许多信号通路，如Wnt、Notch和Hedgehog，在这个肿瘤亚群中发生改变，这也导致了异常增殖。研究人员已经发现了几种癌症干细胞的标志物；然而，仍有许多有待研究，甚至可能根本不存在通用的标志物，因为它们在不同肿瘤类型之间甚至不同患者之间都存在差异。还发现癌症干细胞对放疗和化疗具有抗性。这可能解释了疾病的复发，因为它们没有被完全消除，少量的癌症干细胞就可以使肿瘤重新生长。一旦早期诊断能大大增加治愈癌症的机会，识别肿瘤中的癌症干细胞是开发更有效治疗方法的一个目标。本文的目的是根据癌症干细胞理论讨论癌症的起源，以及其标志物和用于治疗的疗法。
