Dog–human similarities run deep

Dogs have developed alongside humans and have shared our everyday environment for thousands of years. Recent comparisons of the complete human and dog genome sequences have shown that we share a good deal of our genetic makeup, as well.

A new study finds that dogs' genetic similarity to humans extends to the way certain cancers are characterized in our cells (Chromosome Res. 16, 145–154; 2008). Human leukemia and lymphoma are associated with specific cytogenetic abnormalities. Matthew Breen of North Carolina State University (Raleigh) and Jaime F. Modiano of the University of Colorado at Denver investigated three types of cancer that are morphologically similar in humans and dogs (chronic myelogenous leukemia, sporadic Burkitt lymphoma and chronic lymphocytic leukemia). When they compared the regions of the human genome in which the abnormalities occur with homologous regions in the dog genome, they found virtually identical genetic aberrations.

These findings reinforce the proposition that dogs may be a valuable animal model for cancer research. Additionally, it is known that selective breeding has unintentionally preserved genes that increase dogs' susceptibility to certain cancers. Investigating the genetic abnormalities associated with breed-specific canine cancers may help identify genome regions that are not currently associated with tumorigenesis in humans.

Killing two parasites with one drug

Toxoplasmosis may be the most common parasitic infection worldwide, affecting more than two billion people. Existing treatments have serious side effects, can cause hypersensitivity in some patients and are ineffective during some of the parasite's life stages. There is no preventative vaccine. New treatments for toxoplasmosis are desperately needed.

Now it seems that need may be met by a drug that was initially developed to treat malaria. JPC-2056 is slated to begin clinical testing for malaria treatment later this year. Rima McLeod, of University of Chicago (IL), and her colleagues report that JPC-2056 was effective against Toxoplasma gondii (which causes toxoplasmosis) in mice. Mice infected with T. gondii that received JPC-2056 were active and seemed healthy after 4 days, whereas infected control mice seemed ill. Treated mice also had significantly lower numbers of intraperitoneal parasites (PLoS Negl. Trop. Dis. 2, e190; 2008).

Toxicology studies in mice and macaques showed no adverse histopathological effects, suggesting that JPC-2056 is safe to use. In addition, JPC-2056 was effective against all malaria parasites, including those with mutations that conferred resistance to other antimalaria drugs, suggesting that the malaria and toxoplasmosis parasites may not easily develop resistance to the drug.

Another reason to eat your broccoli

Surveys have found that consumption of fruits and vegetables, particularly cruciferous vegetables (such as kale, cabbage and broccoli), is associated with a reduced risk of bladder cancer. Now, a study led by Yuesheng Zhang (Roswell Park Cancer Institute, Buffalo, NY) provides evidence that broccoli substantially reduces bladder cancer in rats (Cancer Res. 68, 1593–1600; 2008).

The researchers induced bladder cancer in rats by adding the carcinogenic substance N-butyl-N-(4-hydroxybutyl)nitrosamine to their drinking water for 8 weeks. During this period they fed rats a diet that included freeze-dried broccoli sprout extract. The team found that broccoli extract effectively inhibited tumor size and progression, and that tumor incidence in rats that received a high dose of the extract was 60% lower than in rats that received the carcinogen and were fed a normal diet.

Cruciferous vegetables may be effective against cancer because they contain isothiocyanates, chemical compounds known to inhibit tumor development. The researchers noted that rats that consumed broccoli had higher concentrations of certain enzymes that can protect cells against carcinogens.

Though higher doses of broccoli extract gave rats more protection, the researchers believe that lower doses—comparable to what humans might normally consume—would still be beneficial.