Cancer Biology: Hallmarks, Genetics, and Signaling Pathways

Vocabulary practice flashcards covering fundamental concepts of cancer biology, including genetic mutations, proto-oncogenes, tumor suppressors, signaling pathways, and the multistep progression of tumors.

Cancer

A disease that results from a breakdown of the regulatory mechanisms that govern normal cell behavior, characterized as an unregulated, multistep process involving the accumulation of multiple cellular abnormalities.

Proto-oncogene

A normal gene involved in cell proliferation (with approximately $70$ identified in human DNA, such as RTKs, RAS, RAF, ERK, and Myc) that is capable of transforming the cell into a cancerous state when mutated.

Oncogene

A mutated gene that has gained function and possesses the potential to cause cancer by promoting uncontrolled cell growth.

Tumor Suppressor Gene

An anti-growth gene that functions to prevent cell proliferation and/or promote programmed cell death (apoptosis); examples include $p53$, $Rb$, and $APC$.

Germline Mutation

An alteration in DNA occurring within a reproductive cell (egg or sperm) that constitutes a hereditary mutation and can be transmitted to offspring.

Somatic Mutation

An alteration in DNA that arises after conception in non-germline cells and is not passed on to offspring.

Neoplasm

An abnormal mass of tissue resulting from the abnormal proliferation of cells, which may be classified as either benign or malignant.

Metastasis

The ability of abnormal cells to penetrate and infiltrate normal tissues, spreading from their primary site of origin to distant parts of the body.

Apoptosis

Programmed cell death that eliminates cells when cellular damage is beyond repair or when cell survival threatens organismal homeostasis.

Growth Factors (GFs)

Proteins that bind to specific cell surface receptors to stimulate intracellular signaling pathways and promote cell growth and proliferation.

Autocrine Stimulation

A signaling mechanism in which cancer cells produce and respond to their own growth factors, essential for driving clonal expansion and the fixation of oncogenic mutations.

Clonal Expansion

The selective proliferation of a mutated cell clone that has gained a growth advantage over neighboring cells during tumor promotion.

Oncogenic Ras

A mutated form of the Ras GTPase that remains permanently bound to $GTP$ in an active 'ON' state without growth factor stimulation, driving constitutive Raf activation and continuous cell division.

p53

A sequence-specific transcription factor and master guardian of the genome that coordinates cell cycle arrest at the $G_1$ checkpoint, activates DNA repair, or triggers apoptosis; mutated in approximately $50\%$ of common cancers.

Rb

A tumor suppressor gene product that controls cell division by modulating the transcriptional activity of factors required for cell cycle progression.

APC

A critical tumor suppressor gene whose normal protein product controls how frequently a cell divides.

Hypoxia

A state of low oxygen supply in cellular tissue that acts as a physiological stress signal capable of inducing $p53$ activity.

Senescence

A permanent non-growing, metabolically active state entered by cells following $p53$-mediated cell cycle arrest.

Silent Mutation

A point mutation in DNA where a nucleotide substitution does not alter the specified amino acid in the resulting protein sequence.

Missense Mutation

A point mutation in DNA where a single nucleotide alteration changes a codon to encode a different amino acid.

Nonsense Mutation

A point mutation in DNA that replaces an amino-acid-specifying codon with a premature stop codon, terminating protein translation prematurely.

Frameshift Mutation

A genetic mutation caused by an insertion (e.g., $+1$) or deletion (e.g., $-1$) of nucleotides in numbers not divisible by three, completely altering downstream codon reading frames.

Translocation

A large-scale chromosomal abnormality characterized by the breakage and reciprocal or non-reciprocal exchange of chromosome segments between non-homologous chromosomes.

Initiation

The first step of cancer development characterized by genetic mutations in key genes, including gain-of-function conversions of proto-oncogenes, loss-of-function in tumor suppressors, and impaired DNA repair systems.

Promotion

The stage of tumorigenesis during which initiated cells acquire a growth advantage and undergo selective clonal expansion, often sustained by autocrine stimulation.

Progression

The advanced stage of multistep carcinogenesis involving the acquisition of additional genetic alterations, such as loss of $p53$ (evasion of apoptosis), telomerase activation (immortality), and sustained angiogenesis.

Malignant Transformation

The phase in which transformed neoplastic cells acquire the capability to invade surrounding native tissues, evade immune surveillance, and establish distant metastases.