I’ve been studying for Step 1 (boards at the end of the 2nd year of med school) and ran across tumor suppressor genes (TSGs). These are genes that serve important functions in preventing cancer. When you lose function or expression of both alleles (the 2 copies of a gene) of a tumor suppressor gene in a cell, cancer risk increase.
Think of it as what happens to a yard in front on an abandoned house: The weeds start to grow out of control.
A specific gene , Rb (Retinoblastoma), is responsible for inhibiting a transcription factor called E2F. This is a fancy way of saying that Rb blocks the function of another protein, one that allows the cell to grow. When Rb works properly, a cell stops growing. When Rb doesn’t, the cell keeps growing regardless of any stop signs from the environment or internal conditions. This loss of Rb function causes cancers such as osteosarcoma and retinoblastoma.
This same mechanism, inhibition of E2F, is shared by a few infectious diseases that make people very sick. These diseases include Corynebacteria diptheria (Diptheria), Vibrio cholerae (Cholera), Pseudomonas aeruginosa (Common cause of hospital-acquired infections), and Bordatella pertussis (Whooping cough).
This is pretty interesting. Why? These bacteria could potentially be used as vectors for anti-cancer therapy. Could we use modified, non-virulent strains of these bacteria to target cancer cells with insufficient Rb signaling?