Wednesday, April 30, 2008

Cancer precursors: red meats and grilling induces carcinogens

This year, as Americans get ready to fire up millions of backyard grills, there's a new scientific wrinkle: according to an exhaustive analysis of international research on diet and cancer, it's time to start looking for an alternative to the hot dog.

Experts at the American Institute for Cancer Research (AICR) are marking the onset of barbecue season by issuing their yearly advice on ways to lower potential cancer risks associated with grilling. This year, new information has come to light on the precise nature of those risks, and AICR's advice reflects this development with a shift in emphasis.

According to AICR, what you grill is the most important issue. US consumption of hot dogs and hamburgers soars during barbecue season, and a recently published landmark AICR report on diet and cancer prevention concluded that diets high in red meat (beef, pork and lamb) and especially processed meats (such as hot dogs) are now a convincing cause of colorectal cancer.

Compared to such clear and compelling risks, the risks associated with the grilling process itself should be of secondary concern. It is clear that grilling animal products (both red and white meat) causes potent carcinogens called heterocyclic amines (HCAs) and polycyclic aromatic hydrocarbons (PAHs) to arise within food.

These substances have been shown in laboratory experiments to trigger the cancer process. The AICR report concluded that there is limited, but suggestive evidence, that these substances factor in human cancer, providing one more reason to limit consumption of red and processed meat, however it is cooked.

Tuesday, April 29, 2008

Magnets in cancer treatments - a new oncology tool or a bad idea?

Biopsy results can be ambiguous: sometimes they can be negative simply because there are too few malignant cells in the sample to be detected - not because all trace of disease has gone. Researchers from the University of New Mexico and the company Senior Scientific, both in Albuquerque, have devised a solution that harnesses the power of magnetic attraction.

The idea is to use magnetic iron oxide nanoparticles encased in a biocompatible material. These in turn can be coated with antibodies that bind to chemicals found only in cancerous cells. When injected into the body, thousands of the particles stick to cancer cells, turning them into miniature magnets. The cells can then be drawn towards magnets encased in the tip of a biopsy needle (Source: Physics in Medicine and Biology, vol 52, p 4009).

A mathematical model of the system confirmed that significant numbers of cancer cells, laden with nanoparticles, could be attracted to a needle within two or three minutes. In the lab, the researchers showed that a magnetised needle could attract leukemia cells surrounded by nanoparticles and suspended in blood or other synthetic materials designed to mimic bodily fluids. Nanoparticles have been used before to destroy diseased cells, but this was the first time they actually retrieved cells.

More recently, researchers have been wondering if cancer treatments be enhanced by something as simple as a magnet. A promising way to tackle some diseases is to deliver cells with modified genes to diseased tissue. Getting enough of the modified cells to the affected area can be tricky.

Claire Lewis and colleagues from the University of Sheffield inserted magnetic nanoparticles, as well as cancer-fighting genes, into monocytes, the white blood cells commonly used in gene therapy, and injected them into mice with tumours. A magnet placed above the tumour caused the cancer-fighting monocytes to congregate there (Source: Gene Therapy, DOI: 10.1038/gt.2008.57).

Monday, April 28, 2008

Oncology vaccine shows promise in prostate cancer

In the past 30 and 40 years, we've learned much about the components of the immune system and the way the components integrate to cause an anti-tumor effect, but very little of this research has translated into real clinical benefit for patients.

However, at the recent AACR meeting in San Diego, early data suggested a promising synergy when allogeneic granulocyte monocyte colony-stimulating factor (GM-CSF) secreting prostate cancer cell lines (GVAX) and escalating doses of the anti-cytotoxic T-lymphocyte antigen CTLA-4 antibody ipilimumab were combined to treat patients with metastatic hormone-refractory prostate cancer.

Researchers have found a promising synergy of two therapies to treat metastatic prostate cancer that is resistant to hormone therapy. In a phase I study, they evaluated a combination of GVAX immunotherapy with ipilimumab lowered prostate-specific antigen (PSA) levels in some patients. In this trial, the vaccine was administered with escalating doses of anti-CTLA-4 (cytotoxic T-lymphocyte antigen 4) antibody ipilimumab. Researchers believe that the combination of these two immunotherapies may increase immunity to prostate cancer.

Twelve patients were enrolled in this study. All were given the same doses of GVAX (a 500 million cell first dose followed by bi-weekly 300 million-cell doses for 24 weeks), and, in groups of three, different quantities of ipilimumab administered every four weeks (.3mg, 1mg, 3mg, or 5 mg).

Anti-tumor activity was observed in five of the six patients who received the two highest doses of ipilimumab, including PSA-level declines of greater than 50 percent; these PSA declines were maintained in four of these patients for at least six months, and up to 16 months. Among patients with PSA-level declines, complete resolution of multiple lesions on bone scans in two patients was noted, resolution of cancer spread to abdominal lymph nodes in one patient, and improvement in bone pain in one patient.