Table 1.

S100 protein family. Main tissue cell localization and function of S100 protein family.

S100 protein	Tissue and subcellular location	Function
S100A1	It is expressed in skeletal muscle fibers, cardiomyocytes and some neuronal populations (8)	Accelerates deterioration of cardiac performance and transition to heart failure (9)
S100A2	It is expressed in the lung, kidney, prostate, skin and salivary and mammary glands (10)	Tumor-suppressing function (11)
S100A3	Highly expressed in hair root cells and some astrocytomas (12).	Tumor-suppressing function and epithelial cell differentiation (11)
S100A4	It is overexpressed in breast cancer, gastric cancer and non-small cell lung cancer (NSCLC) (13)	Apoptosis, cell motility, and tumorigenesis (14)
S100A5	It is upregulated in bladder cancers and recurrent grade I meningiomas (15)	Not described
S100A6	It is overexpressed in lung, bile duct, and brain cancer, and non-small cell lung adenocarcinoma (16–19)	Cell proliferation, cytoskeletal dynamics and tumorigenesis (20, 21)
S100A7	It is overexpressed in inflammatory skin diseases. lymphocytes, monocytes and granulocytes (22)	Antimicrobial response, chemotactic activity, prevent generation of amyloidogenic peptides in Alzheimer’s disease. psoriasis, and atopic dermatitis (23–25).
S100A8	It is found in macrophages, dendritic cells, microvascular endothelial cells but not endothelial cells from larger vessels, epithelial cells (e.g., keratinocytes) and fibroblasts (26)	Regulation of inflammation. Effect on leukocyte adhesion and neutrophil adhesion (e.g., asthma) (5).
S100A9	It is found in myeloid cells: (macrophages and neutrophils) some cancer cells (e.g., breast cancer, esophageal squamous cell carcinoma) (27).	Leukocyte migration, adhesion and transmigration from blood vessels, thus it has anti-inflammatory properties. In some cancer cells it promotes growth suppression (5).
S100A10	It is found in cell types throughout the body though it is located predominantly in the lungs and kidneys (28).	It is involved in the trafficking of proteins to the plasma membrane (angiogenesis and endothelial cell function) (28) and can be expressed on the cell surface as a receptor with clinical implications in some malignancies (e.g., tumor migration, hemorrhagic phenotype of promyelocytic leukemia) (29).
S100A11	It is induced/released by chondrocytes (30)	Stimulates cell growth by enhancing the level of epidermal growth factor (EGF) family proteins, promoting hypertrophic chondrocyte differentiation (31).
S100A12	It is constitutively expressed in neutrophils and inducible in macrophages and smooth muscle cells. it is expressed in human aortic aneurysms (32).	Expression in epithelial cells is associated with growth arrest. Potentiation of atherogenesis (33).
S100A13	It is found in multiple cell types, including fibroblasts, osteoblasts and melanoma cells (20)	It may play a pivotal role in angiogenesis (34).
S100A14	It can be found in an esophageal squamous cell carcinoma cells (35).	It may function as a cancer suppressor, playing a dual role in tumor cells (enhancing or decreasing tumor cell invasiveness) (36).
S100A15	It is expressed in keratinocytes in inflamed skin (37).	Antimicrobial activity against E. coli (38).
S100A16	It is expressed in theca cells, urothelial cells, pancreatic endocrine cells, prostatic glandular cells, squamous epithelial cells, basal prostatic cells, and suprabasal keratinocytes. It is upregulated in several tumors (39).	Recently, a role in insulin sensitivity regulation has been described (40).
S100B	It is expressed in astrocytes, certain neuronal populations, Schwann cells, melanocytes, chondrocytes, adipocytes, skeletal myofibers and associated satellite cells, certain dendritic cell and lymphocyte populations and other cell types (41).	It induces neurogenesis and reduces delayed neuronal injury and might contribute significantly to neuroinflammation (42).
S100P	It can be expressed in urothelial cells, pancreas, syncytiotrophoblasts, gastric mucus-secreting cells (43)	It promotes transendothelial migration of tumor cells and, potentially, metastasis (44).
S100Z	The highest levels were found in the spleen and leukocytes, and in some tumor tissues (e.g., prostate) (45).	Tumor growth. Recently, it has been associated with pulmonary systemic sclerosis (45).