Genetics · MU Sofia

47. Genetic mechanisms of tumorigenesis: general cellular and molecular characteristics of the cancer cell; leading ("driver") mutations. Proto-oncogenes: normal function and mechanisms of transformation into oncogenes…

Explains tumorigenesis as a multistep genetic process and lists the hallmarks that distinguish cancer cells, including growth signalling, apoptosis evasion and the Warburg effect. Separates driver from passenger mutations, then sets out proto-oncogenes and their conversion into oncogenes through point mutation, amplification, translocation and insertion, with a table of normal functions. Covers tumour suppressor genes with the two-hit hypothesis, TP53, RB1 and BRCA1/BRCA2, and closes with DNA repair defects, epigenetic change, telomerase, oncogenic viruses and a multistep model.

Inside: 8 sections · 7 labelled pictures · 2 tables · 15 flashcards · 5 min

Topic 47 of 65 in the MU Sofia syllabus for Genetics (Medicine, Year 3). The free AceMed note covers it in 8 sections, about 652 words (5 min of reading), with 15 flashcards.

In this note

  1. Genetic mechanisms of tumorigenesis: general cellular and molecular characteristics of the cancer cell; leading ("driver") mutations. Proto-oncogenes: normal function and mechanisms of transformation into oncogenes…
  2. TUMORIGENESIS
  3. II. GENERAL CELLULAR AND MOLECULAR CHARACTERISTICS OF THE CANCER CELL
  4. III. DRIVER AND PASSENGER MUTATIONS
  5. IV. PROTO-ONCOGENES AND ONCOGENES
  6. V. TUMOR SUPPRESSOR GENES
  7. VI. OTHER GENETIC MECHANISMS OF TUMORIGENESIS
  8. VII. MULTISTEP MODEL OF CANCER DEVELOPMENT

TUMORIGENESIS

Tumorigenesis is a multistep genetic process in which normal cells acquire progressive genetic and epigenetic alterations, leading to uncontrolled proliferation, survival advantage, invasion, and metastasis.

Cancer is fundamentally a genetic disease of somatic cells, caused by accumulation of mutations that affect genes regulating:

  • cell cycle,
  • apoptosis,
  • DNA repair,
  • cell differentiation,
  • cell–cell interaction.

II. GENERAL CELLULAR AND MOLECULAR CHARACTERISTICS OF THE CANCER CELL

Cancer cells show a characteristic set of biological properties, often referred to as the hallmarks of cancer.

Key Cellular Characteristics

Cancer cells differ from normal cells by:

  • autonomous growth signaling,
  • resistance to growth inhibition,
  • evasion of apoptosis,
  • unlimited replicative potential,
  • genomic instability,
  • ability to invade and metastasize.

Molecular Characteristics

  1. 1. Persistent activation of growth-promoting pathways.
  2. 2. Inactivation of growth-inhibitory mechanisms.
  3. 3. Defects in DNA repair → accumulation of mutations.
  4. 4. Altered metabolism (aerobic glycolysis – Warburg effect).
  5. 5. Ability to induce angiogenesis.
  6. 6. Immune evasion.

III. DRIVER AND PASSENGER MUTATIONS

  • Driver mutations are genetic alterations that directly contribute to tumor initiation and progression by providing a selective growth advantage.
  • Passenger mutations are biologically neutral mutations that accumulate during cell division but do not contribute to cancer development.

Characteristics of Driver Mutations

  1. 1. Affect genes controlling proliferation, apoptosis, or genome integrity.
  2. 2. Are positively selected during tumor evolution.
  3. 3. Usually involve oncogenes or tumor suppressor genes.
  4. 4. A limited number of driver mutations is sufficient to initiate cancer.

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