Cancer and Genetic Mechanisms in Biology

Cancer as Acquired Genetic Diseases

• Cancers arise from dysregulation of genes.
• Oncogenes and tumor suppressor genes play crucial roles in cancer development.
• Mutations can cause cancers.

DNA Translation into Protein

• Genes encode proteins.
• Transcription converts DNA to pre-mRNA.
• Pre-mRNA undergoes splicing (removal of introns).
• mRNA leaves the nucleus and undergoes translation into a protein.
• Steps like chromatin remodeling, RNA processing, transport, and localization, along with protein translation control, and protein activity/degradation are essential to this process.

Chromatin and DNA Packaging

• DNA wraps around histone proteins to form chromatin.
• Modifications (like acetylation, phosphorylation, and methylation) of histone tails regulate DNA packaging, influencing transcription accessibility.
• These modifications affect how tightly the DNA is packaged, impacting transcription factor access.

Example: RB1 Gene

• RB1 is a tumor suppressor gene, crucial for cell cycle regulation.
• RB1 gene mutations, often affecting splicing, can lead to retinoblastoma.
• RB1 controls the transition from G1 to S phase of the cell cycle.

Example: INK4 Tumor Suppressors

• INK4 is a family of cyclin-dependent kinase inhibitors.
• INK4 regulates cell cycle progression by inhibiting CDK4/6 and cyclin D activity.
• INK4 mutations/deletions remove its tumor suppressor effects.

Example: ARF Gene

• ARF (ADP ribosylation factor) is a tumor suppressor.
• ARF inhibits MDM2 activity, which normally targets p53 for degradation.
• ARF deletion can remove the tumor suppressor effect of p53.

Example: MDM2 Amplification

• MDM2 is a negative regulator of the p53 protein, a key anti-cancer protein.
• MDM2 amplification (increased copies) is linked to numerous cancers like lung and colon cancer.
• MDM2 mutations can make MDM2 overactive, reducing p53 levels.

Example: TP53 Gene

• TP53 (p53) is the most common mutated gene in cancers.
• It's a critical transcription factor involved in regulating cell proliferation and apoptosis (programmed cell death).
• Over 29,000 distinct TP53 mutations have been identified, with many concentrated in "hotspots."
• Loss-of-function mutations are common.

Example: Philadelphia Chromosome

• Characteristic of chronic myeloid leukemia (CML).
• Involves a reciprocal translocation between chromosomes 9 and 22.
• The BCR-ABL1 fusion gene creates a constitutively active tyrosine kinase, contributing to malignancy.

Example: RAS Mutations

• RAS mutations lead to constitutively active RAS proteins, driving cancer development.
• A significant portion of cancers (about 20%) involves RAS mutations.
• Most RAS mutations impact codons 12, 13, and 61.

Explore the relationship between cancer and genetic changes through this quiz on acquired genetic diseases. Understand the roles of oncogenes, tumor suppressor genes, and the processes of DNA translation and chromatin packaging. Test your knowledge on key concepts such as the RB1 gene and its implications in cancer development.