It also helps the dermis function by providing support

It also helps the
dermis function by providing support to the blood vessels, lymphatic vessels,
nerves, and gland caps that pass through it to reach the dermis. Subcutaneous
fat acts as a shock absorber and heat insulator protecting underlying tissues
from cold and mechanical trauma.


Cutaneous squamous cell carcinomas
(SCCs) are the second most common and potentially
deadly human cancers. A
significant lifetime ultraviolet radiation exposure is the principal
determinant of squamous cell carcinoma (SCC) and the disease appears most
frequently in the areas more exposed by natural or artificial sunlight, head
and neck among others, such as the edges of the ears, lips, face and scalp.

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Ultraviolet radiation produces mutations in DNA, usually the formation of
thymidine dimers in the p53 tumor-suppressor gene. Failure to repair these
mutations may result in tumor formation. The solar exposure that a person
receives throughout his life becomes a cumulative damage that can lead to SCCs;
the older, the higher the incidence. Chronic skin ulceration and an
immunosuppressed state are also predisposing factors for this malignant
disease. These facts seem to be related by favoring the spread of atypical
keratinocytes through the epidermis and its subsequent dermal invasion.


These solid tumors are complex structures composed of
multiple cell types in unique microenvironments. Actively proliferating cancer
cells in SCCs reside in the basal layer of the tumor propagating cancer cells
(TPCs), which is located along the tumor stroma interface. In Squamous cell
Carcinoma, cells tumor propagating cells are located in the basal layer, in
contact with the stroma. In adult skin, stem cells are located in two different
compartments, one in the inter-follicullar epidermis (Epi) and the second one
in the bulge from the hair follicle (Hair follicle stem cells; HFSC), which are
the most prominent cell population in skin epithelium. TPCs can self-renew to sustain their own identity and differentiate into post-mitotic progeny without tumor propagating
potential. Differential
gene expression
analyses uncovered
a transcriptional signature,
which distinguishes
TPCs from normal, adult skin epithelial
stem and progenitor cells.


Here is where we identify the Oxidative Stress
Response as one of the most significantly up-regulated Gene Ontology categories
in TPCs. This stress response is triggered by reactive oxygen species (ROS).

ROS species are normal byproducts generated through metabolic reactions
essential for eukaryotic organisms. They are associated to aerobic organisms
and related to cellular processes such as metabolism, proliferation,
differentiation and immune system regulation. These components come from redox reactions generated
principally in the mitochondria electronic chain, using oxygen as the principal
pathway for ATP production in the process known as oxidative
phosphorylation.  Nevertheless, they can
also be generated in other cell organelles like peroxisomes, apoplasts and
chloroplasts. These oxygen species are composed specially by hydrogen peroxide
(H2O2) and free radical’s superoxide
anion (O2).