Liu-Smith Feng, Jia Jinjing, Zheng Yan
Department of Epidemiology, University of California, Irvine, CA, USA.
University of California, Irvine, CA, 92697, USA.
Adv Exp Med Biol. 2017;996:27-40. doi: 10.1007/978-3-319-56017-5_3.
There are three major types of skin cancer: melanoma, basal cell carcinoma (BCC) and squamous cell carcinoma (SCC). BCC and SCC are often referred to as non-melanoma skin cancer (NMSC). NMSCs are relatively non-lethal and curable by surgery, hence are not reportable in most cancer registries all over the world. Melanoma is the deadliest skin cancer. Its incidence rate (case number) is about 1/10th of that for NMSC, yet its death toll is ~8 fold higher than NMSC.Melanomas arise from melanocytes which are normally located on the basement membrane with dendrites extending into the epidermal keratinocytes. A major known function of melanocytes is to produce pigments which are enclosed by lipid membrane (termed melanosomes) and distribute them into keratinocytes, thus give different shade of skin colors. BCCs arise from basal cells, which are a layer of cells located at the deepest part of epidermis. Basal cells are recently considered to be skin stem cells as they are constantly proliferating and generating keratinocytes which are continuously pushed to the surface and eventually become a dead layer of stratum corneum. Squamous cells are the keratinocytes which resembles fish scale shape, ie, those initiated from basal cells and differentiated into squamous cells. Both basal cells and squamous cells belong to keratinocytes, therefore sometimes BCC and SCC are termed keratinocyte cancer.These three types of cancer share many characteristics, yet they are very different from etiology to progression. One shared characteristic of skin cancer is that, according to the current views, they all are caused by solar or artificial ultraviolet radiation (UVR). UVA and UVB from solar UVR are the major UV bands reaching the earth surface. Both UV types cause DNA damage and immune suppression which play crucial roles in skin carcinogenesis. UVB can be directly absorbed by DNA molecules and thus causes UV-signature DNA damages; UVA, on the other hand, may function through inducing cellular ROS which then causes oxidative DNA damages [1-4]. This chapter will discuss the molecular signaling differences of UVR in melanoma and NMSC.
黑色素瘤、基底细胞癌（BCC）和鳞状细胞癌（SCC）。BCC和SCC通常被称为非黑色素瘤皮肤癌（NMSC）。NMSC相对不致命，可通过手术治愈，因此在世界上大多数癌症登记处都无需报告。黑色素瘤是最致命的皮肤癌。其发病率（病例数）约为NMSC的1/10，但死亡人数比NMSC高约8倍。黑色素瘤起源于黑素细胞，黑素细胞通常位于基底膜上，其树突延伸至表皮角质形成细胞。黑素细胞的一个主要已知功能是产生色素，这些色素被脂质膜（称为黑素小体）包裹，并将其分布到角质形成细胞中，从而赋予皮肤不同的颜色深浅。BCC起源于基底细胞，基底细胞是位于表皮最深处的一层细胞。基底细胞最近被认为是皮肤干细胞，因为它们不断增殖并产生角质形成细胞，这些角质形成细胞不断被推向表面，最终成为角质层的死细胞层。鳞状细胞是类似鱼鳞形状的角质形成细胞，即那些从基底细胞开始并分化为鳞状细胞的细胞。基底细胞和鳞状细胞都属于角质形成细胞，因此有时BCC和SCC被称为角质形成细胞癌。这三种癌症有许多共同特征，但从病因到进展都有很大不同。皮肤癌的一个共同特征是，根据目前的观点，它们都是由太阳或人工紫外线辐射（UVR）引起的。来自太阳UVR的UVA和UVB是到达地球表面的主要紫外线波段。这两种紫外线都会导致DNA损伤和免疫抑制，这在皮肤致癌过程中起着关键作用。UVB可以直接被DNA分子吸收，从而导致具有紫外线特征的DNA损伤；另一方面，UVA可能通过诱导细胞ROS起作用，然后导致氧化性DNA损伤[1-4]。本章将讨论UVR在黑色素瘤和NMSC中的分子信号差异。
