Putting the heat on tumors: boost therapies with just a few degrees

Amp up that cancer treatment by adding a little heat.

Local hyperthermia – the heating of tumors to approximately 106-109 degrees Fahrenheit – can boost the efficacy of radiation therapy and chemotherapy.

This technique was popular in the 1970s and 80s, but because clinicians were never sure how exactly it helped inhibit tumors, the treatment became outshined by competing approaches.

Turns out, heating a tumor blocks a key DNA repair pathway that otherwise hampers radiation and chemo. With that repair system taken out, cancer cells can’t fix their DNA when damaged by those treatments.

Roland Kanaar of Erasmus Medical Center and colleagues screened mouse embryonic stem cells with defects in various DNA repair pathways and tested them for the effects of heat.

They found that high temperatures degrade an essential player in DNA repair called the BRCA2 protein. Ordinarily, BRCA2 fixes breaks in the DNA of cancer cells.

Currently, there are new trial drugs that inhibit another protein involved in DNA repair, an enzyme called PARP-1. These are used to treat rare cancers caused by mutated BRCA2 genes, such as some hereditary breast and ovarian cancers.

If hyperthermia can be used to inhibit DNA repair in a range of tumors, PARP inhibitors – which are well-tolerated with fewer side effects than traditional chemotherapy, says Kanaar – may be more widely applicable in oncology.

"We [wouldn't] need to depend on rare genetic mutations to treat a tumor with PARP inhibitors," Kanaar says. "So a drug developed for a small group of tumors with a specific genetic mutation, might now be useful for a larger group of tumors," he adds.

It just takes the right combination of drugs and heat. But, as Kanaar cautions, "heat will do a lot of things to cells."

The study was published in the Proceedings of the National Academy of Sciences yesterday.

Image by cohdra via morgueFile

This post was originally published on Smartplanet.com