BMAT PREP - CANCER

- Carcinogens (agents which can cause cancer):

• e.g.: smoke, radiation;
• cause mutations in genes which control cell division (oncogenes);
• divide uncontrollably → small mass of cells (tumour);

- Tumour cells do not respond to signals from nerves and hormons:

• continue to grow;
• no programmed cell death occurs (apoptosis);
• benign → does not spread from origin (not cancerous);
• malignant → cancerous
• spread, invade and destroy other tissues;
• cells can break off from primary malignant tumour;
• spread via lympathic system;
• cause secondary tumours (metastasis) → hard to find + remove

- Cancers may take years to develop with few/no symptoms (→ but some symptoms are: haemoptysis (coughing up blood), pneumonia).

• usually advanced when discovered

- Tendency to develop cancers seems to be inherited.

- Tumours cells in some cancers have abnormal chromosomes.

- Positive correlation between mutations and carcinogens.

- Oncogenes (genes that turn cells into cancers):

• → found when proto-oncogenes (normal versions of genes) mutate + become over-active.

- RAS Oncogenes:

• G-proteins are found on plasma membranes + enable cells to respond to growth factors;
• activated by enzymes within cell (GTPase);
• mutation of RAS gene → GTPase deficient proteins;
• mutated G-proteins remain active for longer → causing tumours;

- Myc Oncogenes:

• myc gene produces a protein needed for normal cell division;
• common mutation switches myc proto-oncogene from chromosome 8 to 14;
• there, acts as oncogene/abnormal cell division/tumour;
• when both myc and RAS oncogenes present together → malignant cells result;

- Tumour suppressor genes:

• reduce normal activity by inhibiting cell division;
• initiate cell death (apoptosis) if the cell's DNA is damaged (due to mutations);
• mutations of this gene → loss of function ⇒ reults in tumours