Stem cells from fat target cancer

Researchers in Slovakia have been able to derive mesenchymal stem cells from human adipose, or fat, tissue and engineer them into “suicide genes” that seek out and destroy tumours like tiny homing missiles. This gene therapy approach is a novel way to attack small tumour metastases that evade current detection techniques and treatments, the researchers conclude in the July 1 issue of Cancer Research, a journal of the American Association for Cancer Research.

“These fat-derived stem cells could be exploited for personalized cell-based therapeutics,” said the study’s lead investigator, Cestmir Altaner, Ph.D., D.Sc., an associate professor in the Cancer Research Institute of the Slovak Academy of Sciences in Bratislava. “Nearly everyone has some fat tissue they can spare, and this tissue could be a source of cells for cancer treatment that can be adapted into specific vehicles for drug transport.”

Mesenchymal stem cells help repair damaged tissue and organs by renewing injured cells. They are also found in the mass of normal cells that mix with cancer cells to make up a solid tumour. Researchers believe mesenchymal stem cells “see” a tumour as a damaged organ and migrate to it, and so might be utilized as a “vehicle” for treatment that can find both primary tumours and small metastases. These stem cells also have some plasticity, which means they can be converted by the micro environment of a given tissue into specialized cells, Altaner says.

After extracting the stem cells from human fat tissue the researchers worked to find a less toxic way to treat colon cancer than the standard-of-care chemotherapy agent, 5-fluorouracil (5-FU), which can produce toxic side effects in normal cells. They expanded the number of mesenchymal stem cells in the laboratory and then used a retrovirus vector to insert the gene cytosine deaminase into the cell. This gene can convert a less toxic drug, 5-fluorocytosine (5-FC), to 5-FU inside the stem cells, and the chemotherapy can then seep out into the tumour, producing a lethal bystander effect.

In nude mice – animals with an inhibited immune system – engrafted with human colon cancer, the researchers first injected the engineered mesenchymal stem cells, then 5-FC. They found tumour growth was inhibited by up to 68.5 percent in the animals, and none of the mice exhibited any signs of toxic side effects.

However, none of the animals remained tumour-free. “The procedure was quite effective even though we applied the stem cells just once. Obviously, repeated treatment will increase the efficacy, as would using this strategy in combination with other treatments,” Altaner said.

Normal mesenchymal cells can be isolated from various sources, including bone marrow, but the yield is not nearly as great as what the researchers derived from fat tissue. Removal of fat tissue during surgery to remove a tumour would be simple, says Altaner. Liposuction could also be used to isolate mesenchymal stem cells can also be gathered and isolated through liposuction, and the cells frozen in liquid nitrogen for future therapeutic use. Both processes would be easier than taking bone marrow from a patient, Altaner said.

The study was funded by grants from the Slovak Academy of Sciences and the League Against Cancer, and support from the Slovakian national cancer genomics program.

The mission of the American Association for Cancer Research is to prevent and cure cancer. Founded in 1907, AACR is the world's oldest and largest professional organization dedicated to advancing cancer research. The membership includes nearly 26,000 basic, translational, and clinical researchers; health care professionals; and cancer survivors and advocates in the United States and more than 70 other countries.

AACR marshals the full spectrum of expertise from the cancer community to accelerate progress in the prevention, diagnosis and treatment of cancer through high-quality scientific and educational programs. It funds innovative, meritorious research grants. The AACR Annual Meeting attracts more than 17,000 participants who share the latest discoveries and developments in the field. Special Conferences throughout the year present novel data across a wide variety of topics in cancer research, treatment, and patient care.

AACR publishes five major peer-reviewed journals: Cancer Research; Clinical Cancer Research; Molecular Cancer Therapeutics; Molecular Cancer Research; and Cancer Epidemiology, Biomarkers & Prevention. Its most recent publication, CR, is a magazine for cancer survivors, patient advocates, their families, physicians, and scientists. It provides a forum for sharing essential, evidence-based information and perspectives on progress in cancer research, survivorship, and advocacy. – (EurekAlert)

July 2007