Glossary

B

Basal cell carcinoma: Cancer that begins in the lower part of the epidermis (the outer layer of the skin), usually found on areas of the body exposed to the sun. It is the most common form of skin cancer. Basal cell carcinomas rarely metastasize (spread) to other parts of the body, but if the carcinoma does advance, treatment can become difficult.

Cell differentiation: The process during which young, immature (unspecialized) cells take on individual characteristics and reach their mature (specialized) form and function.
Chronic myelogenous leukemia (CML): A slowly progressing disease in which too many white blood cells (not lymphocytes) are made in the bone marrow. Also called chronic granulocytic leukemia, chronic myeloid leukemia, and CML.
Cilia: Minute hair-like structures that extend from a cell surface and beat rhythmically to move the cell or to move fluid or mucus over the surface.

Epithelial cell: A type of cell that lines the internal and external surfaces of the body.

Fibroblast: A connective tissue cell that makes and secretes collagen proteins.

Glioma-associated oncogene (Gli): Transcription factor that mediates transcriptional responses to Hedgehog signaling. In mammals, there are 3 Gli homologs: Gli1 and Gli2 are pathway activators, whereas Gli3 is mainly cleaved and functions as a transcriptional repressor.
Gorlin syndrome: A genetic condition that causes unusual facial features and disorders of the skin, bones, nervous system, eyes, and endocrine glands. People with this syndrome have a higher risk of basal cell carcinoma. Also called basal cell nevus syndrome and nevoid basal cell carcinoma syndrome.

Hedgehog (Hh): Ligand of the Hedgehog signaling pathway. There are 3 Hedgehog proteins in mammals: Sonic Hedgehog (Shh), Indian Hedgehog (Ihh) and Desert Hedgehog (Dhh), all of which initiate signaling by binding their receptor, Patched.

Ligand: A molecule that binds to another molecule, used especially to refer to a small molecule that binds specifically to a larger molecule.

Medulloblastoma: A malignant brain tumor that begins in the lower part of the brain and that can spread to the spine or to other parts of the body.
Morphogenesis: The evolution and development of form, as the development of the shape of a particular organ or part of the body.

Pancreatic ductal adenocarcinoma (PDAC): The most common pancreatic neoplasm, accounting for >85% of pancreatic tumor cases.
Pancreatic intraepithelial neoplasm (PanIN): The most common and most often studied of 3 PDAC precursor lesions, PanIN is found in the smaller-caliber pancreatic ducts.
Paracrine signaling: A mode of signaling in which one cell (the sending cell) produces the signal (eg, Hh ligand), but a different cell (the receiving cell) binds to and responds to it.
Patched (PTCH): The Hedgehog receptor is a 12-transmembrane protein found at the cell surface or in primary cilia that binds to Hedgehog to initiate ligand-dependent signaling. In the absence of ligand, it keeps the pathway off by inhibiting Smoothened. Because PTCH is upregulated by Hedgehog signaling, it also serves to attenuate signaling by negative feedback.

Smoothened (SMO): A 7-transmembrane GPCR-like protein that transmits the Hedgehog signal upon stimulation, leading to activation of the Gli transcription factors. It is also the target of several Hedgehog pathway inhibitor drugs.
Stromal cell: A type of cell that makes up certain types of connective tissue (supporting tissue that surrounds other tissues and organs).
Suppressor of fused (SUFU): A negative regulator of the Hedgehog pathway, SUFU binds to all 3 Gli proteins to inhibit their entry into the nucleus and acts as a transcriptional co-repressor. SUFU deletion causes increased Hedgehog signaling activity.

Transcription: The process by which a cell makes an RNA copy of a DNA sequence.
Tumor microenvironment: The normal cells, molecules, and blood vessels that surround and feed a tumor cell. A tumor can change its microenvironment, and the microenvironment can affect how a tumor grows and spreads.
Tumorigenesis: The production of tumors.