U of G Chemist Hopes to Decode Cancer-Causing Mould

[Guest guest]

At times I just sit here shaking my head when I read articles such

as this concerning ochratoxins A. and cancer. This is nothing new,

but maybe they have been concentrating more on Aflatoxins. It wasn't

long ago I spoke to an oncologist at a local hospital and asked him

if he saw elevated levels of aflatoxins in his patients. He didn't

seem to be aware of these toxins and didn't believe there was a test

for it, there is. Then I asked him if he saw elevated levels of

ochratoxins and he got wide eyed and excited like he knew more about

these toxins. He said yes, but couldn't give me a reason why. I

asked do you realize where these toxins come from and please don't

tell me from eating moldy cheese and bread. No answer. So I

explained that they can come from several forms of aspergillus and

penicillium and that you can be by exposed to these toxins not only

by ingestion but through inhalation. After that comment he realized

where I was going and clammed up.

I was also told the same day by a technician that just lost his dad

to kidney cancer, due to aspergillus fumigatus.His next statement do

you realize we lose over 300 patients a year to this. And he also

thought there was only one kind of aspergillus. So I gave him a

little education.

KC

U of G Chemist Hopes to Decode Cancer-Causing Mould

Web posted on October 22, 2006

http://www.thefountainpen.com/cgi-bin/showstory?id=5482

(University of Guelph)A University of Guelph chemist is helping to

determine how a dangerous mould that forms on wheat and oats causes

kidney cancer, which could have an impact on the allowable levels of

the substance in Canadian food sources.

Prof. Manderville is studying a type of mycotoxin – a

naturally occurring toxin produced from fungi that often attach to

grain crops – called ochratoxin A, to see why it causes cancer in

animals.

A recent study by Health Canada found that the toxin is present in

50 per cent of Canadian breakfast cereals and many grain products.

" Mycotoxins should be a big, hot item in Canada because ochratoxin A

thrives in northern wet climates and is the most potent kidney

carcinogen that's ever been tested by the National Toxicology

Program in the United States, " said Manderville.

The problem is, this mould is naturally occurring in grain products

and is difficult to prevent, said Manderville. " You can't see it

with the naked eye. The mycotoxins can be detected only because our

analytical techniques are so good today. They've probably always

been in our cereal; we just couldn't detect them until recently. "

When wheat is processed into cereal or bread, a lot of the

mycotoxins are eliminated, but not enough to meet international

standards. They resist high temperatures, so cooking also doesn't

destroy them. " Canada produces great wheat, but if we're not being

stringent enough with our allowable levels of mycotoxins, the

implications could be huge, " said Manderville.

Scientists currently don't know how ochratoxin A causes cancer, but

he suspects it acts as a genotoxin (something that damages DNA) and,

after it's metabolized, attaches to DNA, initiating a mutation that

causes cancer.

Manderville and his research group are the first scientists in the

world to assess the nature of DNA damage caused by this toxin. They

have found that once ochratoxin A is oxidized, it tends to target

the G-base of DNA to form an ochratoxin A DNA adduct. They are now

chemically reproducing the adduct to incorporate into DNA using a

DNA synthesizer in Manderville's lab in U of G's new science

complex. He will structurally characterize the modified DNA and, in

turn, study repair of the lesion and mutagenicity.

" We're looking at how this modification alters DNA structure, such

as stability of the duplex, and we're going to determine if it's

mutagenic, " he said. His team is determining if affected DNA gets

repaired naturally and, if not, the kinds of mutations that

ochratoxin A causes. " Once we know the answers to those questions,

that will provide the key for finding out how this molecule causes

cancer. "

Currently, the allowable levels of ochratoxin A in food for humans

is governed by its toxic properties in pigs. " If we establish that

ochratoxin A is a genotoxin, the allowable levels of ochratoxin A in

food will be decreased, " said Manderville. " This will be problematic

for the food industry because it's a natural product and they don't

know how to get rid of it. "

He notes that European scientists are working on procedures to

prevent the mould from growing on their crops, and European health

officials have set stringent regulations on the limits of the toxins

in foods.