1
$\begingroup$

Since most of the chemotherapy drugs kill cancer cells by damaging their DNAs by means of free radicals. So antioxidants, which will detoxify free radicals, should theoretically decrease the efficacy of the chemotherapy.

However clinical trials are proving the opposite. Saying, antioxidants does not decrease chemotherapy efficacy but also make chemotherapy more effective, thus increase the survival rate. http://www.ncbi.nlm.nih.gov/pubmed/17283738

The question is, why antioxidants do not interfere with chemo, while they are supposed to do ?

$\endgroup$
  • $\begingroup$ That reference doesn't look very authentic. Four authors all named Simone (a family enterprise?), from the "Simone Protective Cancer Institute", which appears to be just a website (www.drsimone.com). This Dr Simone (self-appointed as "cancer's worst enemy") says he is endorsed by Ronald Reagan and claims broad expertise ranging from "the truth" about cancer to "how to save yourself from a terrorist attack", and peddles various anti-cancer diets (?) as well as health insurance plans. Stay away ... $\endgroup$ – Roland Jan 24 '16 at 10:45
1
$\begingroup$

Since it's a very broad argument I'll try to summarize in a few sentences.

First of all the sentence:

Since most of the chemotherapy drugs kill cancer cells by damaging their DNAs by means of free radicals. So antioxidants, which will detoxify free radicals, should theoretically decrease the efficacy of the chemotherapy.

is a bit inaccurate as of today. The chemotherapy today uses the "classical" chemotherapy drugs which IN PART use the mechanism of free radical but there are a lot of mechanism such as microtubule damage and so on which do not depend on free radical toxicity. Today there are also a lot of biological drugs and inhibitors of tyrosine kinase inhibitor which use a completely different pathway.

You cite a paper from 2007, a bit dated, I cannot access full text because it's an abstract. It seems it's not performed in a systematic manner (it's a not a systematic review or meta-analysis) and is published in a journal of alternative medicine. Maybe there are more recent paper but unfortunately at the moment I cannot have the time to check.

Finally you are comparing the effects of a chemotherapy drug administered usually in high dosage to the use of antioxidant which I cannot recall are sold as drugs used regularly, so it's a potential interesting biological question but practically it's a bit difficult to compare the oxidative effect of a cancer drug with the effect of an antioxidant one in real patients since I don't think there are randomized controlled clinical trials comparing chemotherapy to antioxidant alone.

$\endgroup$
0
$\begingroup$

There are many ways to damage the DNA of a rapidly proliferating population of cells; oxidative damage is one example—albeit a very broad example not especially specific to cancer cells, the cells we would like to eliminate.

Many non-targeted chemotherapeutic drugs exploit other mechanisms of depriving cancers cells of a high-fidelity genome, therefore reducing their competitive fitness or outright killing them due to a lack of functioning copies of essential genes. For an overview of such classes of drugs, see the Wikipedia page on Chemotherapy.

Alkylating agents covalently modify the DNA (along with protein and RNA) of affected cells, causing misreading errors to accumulate as DNA is replicated. Alkylated DNA bases cause misincorporation of nucleotides on the newly synthesized strand that sometimes escape proofreading, causing mutations to be passed on to all daughter cells. Also, if such survailance systems are working in cancer cells, alkylated DNA can cause cell cycle arrest or even programmed cell death.

Antimetabolites disrupt necessary cellular metabolic functions. One common mechanism is to interfere with any chemical reactions catalyzed by the folate family of vitamins/enzymatic cofactors. Folate is necessary for synthesis of some new nucleotides, which are necessary for replicating the genome. A lack of these nucleotides can cause low-fidelity DNA replication (introducing deleterious mutations into the genomes the cells) and cell cycle arrest, blocking division and proliferation.

Anti-microtubule agents interfere with the dynamic behavior of microtubules, a subcellular structure responsible for properly sorting the chromosomes during cell division; microtubules also contribute to cell shape and tissue-invasive locomotion. Preventing microtubules from functioning normally can lead to chromosomal missegregation during cell division, depriving some daughter cells of whole chromosomes (gene loss) and leading to genome instability, which can cause cells to loose fitness or loose genes necessary for life.

These are some examples of chemotherapeutics that do not rely on broadly oxidative mechanisms for their cell-killing action. The point of chemotherapy is to be more toxic to malignant cells than to the rest of the body's cells. Since malignant cells often divide more often than normal body cells in adults, many chemotherapeutic agents are employed with the idea in mind of being more toxic to rapidly-diving cells and less toxic to slowly diving cells.

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.