bleomycin
Meaning of bleomycin: A chemotherapy drug from soil bacteria that cuts DNA using iron and oxygen, and that spares the bone marrow while scarring the lungs.
Definition of bleomycin
Bleomycin is a chemotherapy drug originally isolated from the soil bacterium Streptomyces verticillus. It binds to DNA and, working with iron and oxygen, generates reactive molecules that cut both strands, killing dividing cells. It is used against Hodgkin lymphoma, testicular germ cell tumors and some squamous cell cancers, and it is also injected into the chest cavity to seal off repeated fluid collections.
How does it kill cells?
The molecule has two working ends. One end grips DNA and slots between its bases. The other end holds an iron atom. With oxygen present, that iron generates free radicals, highly reactive fragments that attack the sugar backbone of the DNA strand right beside them. Both strands can be cut at once, and a double-strand break is the hardest kind of damage for a cell to repair. A cell that cannot mend it dies when it next tries to divide.
Why does it affect the lungs and skin most?
| Feature | Bleomycin | Most chemotherapy |
|---|---|---|
| Bone marrow suppression | Minimal | Common and dose-limiting |
| Main dose-limiting harm | Lung scarring | Low blood counts |
| Hair loss | Variable | Frequent |
An enzyme called bleomycin hydrolase breaks the drug down, and lung and skin tissue carry very little of it. The drug therefore lingers longest exactly where it is least wanted. In the lung it drives inflammation and then fibrosis, a stiffening scar that reduces the ability to transfer oxygen and does not reverse. Risk rises with the total amount given, with age, with kidney impairment and with radiation to the chest. High concentrations of inspired oxygen are also recognized as a hazard afterward, since oxygen is part of the mechanism of injury.
Where does it fit among cancer drugs?
It is classed as an antineoplastic antibiotic, a group of compounds found in bacteria that proved more useful against tumors than against infection. Bleomycin has almost no place as an ordinary antibiotic. Its value in combination regimens comes from the fact that it does not add to marrow suppression, so it can be given alongside drugs that do without compounding the drop in blood counts.
Used in a sentence
The regimen included bleomycin, with lung function monitored throughout treatment.
Good to know
Bleomycin causes little bone marrow suppression, and its dose-limiting harm is lung fibrosis, a risk that rises with cumulative dose, age, kidney impairment and chest radiation.