Anti-tumor antibiotics Flashcards
What are the anti-tumour antibiotics produced from streptomyces bacteria ?
Belyomycin, anthracyclines, Dactinomycin or actinomycin D the later two are cell cycle non-specific.
What happens in G1 phase of the cell cycle ( interphase) ?
cell grows and performs its function.
What happens in G1 check point ?
Screening for potential DNA damage and protein synthesis abnormalities. The cell will either progress to S phase or go to G0 phase where DNA repair or progression to apoptosis will happen.
What is the action of DNA helicase in S phase ?
It unwindes the DNA strands create replication fork.
What is the action of topoisomerase enzyme ?
In the S phase it helps to loosen up the DNA helix during the unwinding process mediated by the DNA helicase.
What is the action of RNA primase and DNA polymarase ?
they together create the new RNA template by adding base pairs to the unwound DNA strand.
What are the events in G2 phase and G2 check point ?
In G2 phase the cell grows again before entering mitosis and the G2 chekpoint does the final screening before mitosis for DNA damage.
Why are cytotoxic medications toxic to cancer cells and rapidly dividing normal cells?
These cells divide more rapidly and therefore they are more sensitive to DNA damage and errors in checkpoint functions. This makes them susceptible to cytotoxic drug mediated destruction.
What is the structure and action of Belomycin ?
It is a G2 phase of the cell cycle specific medication with an iron binding and DNA binding sites. In the presence of O2 it acts as an oxidase and generate ROS which oxidise DNA bases causing breaks in DNA strands.
What are the cancers treated using Belomycin ?
Hodgkin’s lymphoma, tetsticular cancer, and squamous cell carcinoma of the skin.
What is the mechanism of Belomycin toxicity ?
The enzyme hydrolase is essential for the inactivation of bleomycin. The lungs and skin lacks it. Therefore, Bleomycin causes pulmonary toxicity in the form of pneuomitis and fibrosis as well as skin rashes, exfoliation and hyper-pigmentation. It can also cause stomatitis and mucocytis in the mouth.
What is the unique feature of Bleomycin ?
Minimal myelosupression.
What is the action of Dactinomycin or actinomycin D ?
It is a peptide that intercalates into the DNA molecule. Which prevents the binding of RNA and DNA polymarase to the DNA leading to RNA and DNA synthesis inhibition. It also cause breaks in DNA strands through ROS generation in a cell cycle non-specific manner.
What is the indication for Dactinomycin ?
It is used to treat Wilm’s tumour, rhabdomyosarcoma and Ewing’s sarcoma. The main side effects are significant mylosupression and alopecia.
What are the drugs in the anthracyclin category ?
Doxorubcin, Daunorubicin, Idarubicin and Epirubicin.
