Obese women’s stem cells make cancer grow faster

HERE is yet another reason to stay at a healthy weight.

Stem cells from the fat of women with obesity boost the growth of breast tumors more than cells from slim women.

Stem cells are undifferentiated biological cells, that can differentiate into specialized cells and can divide (through mitosis) to produce more stem cells. They are found in multicellular organisms. In mammals, there are two broad types of stem cells: embryonic stem cells, which are isolated from the inner cell mass of blastocysts, and adult stem cells, which are found in various tissues.

In adult organisms, stem cells and progenitor cells act as a repair system for the body, replenishing adult tissues. In a developing embryo, stem cells can differentiate into all the specialized cells—ectoderm, endoderm and mesoderm (see induced pluripotent stem cells)—but also maintain the normal turnover of regenerative organs, such as blood, skin, or intestinal tissues.

There are three accessible sources of autologous adult stem cells in humans:

• Bone marrow, which requires extraction by harvesting, that is, drilling into bone (typically the femur or iliac crest),
• Adipose tissue (lipid cells), which requires extraction by liposuction, and
• Blood, which requires extraction through apheresis, wherein blood is drawn from the donor (similar to a blood donation), passed through a machine that extracts the stem cells and returns other portions of the blood to the donor.

Stem cells can also be taken from umbilical cord blood just after birth. Of all stem cell types, autologous harvesting involves the least risk. By definition, autologous cells are obtained from one’s own body, just as one may bank his or her own blood for elective surgical procedures.

Highly plastic adult stem cells are routinely used in medical therapies, for example in bone marrow transplantation. Stem cells can now be artificially grown and transformed (differentiated) into specialized cell types with characteristics consistent with cells of various tissues such as muscles or nerves through cell culture. Embryonic cell lines and autologous embryonic stem cells generated through therapeutic cloning have also been proposed as promising candidates for future therapies. Research into stem cells grew out of findings by Ernest A. McCulloch and James E. Till at the University of Toronto in the 1960s.

To probe the link between obesity and breast cancer, Bruce Bunnell at Tulane University in New Orleans enlisted the help of 24 women having liposuction, half of whom were obese.

Mice were injected with a mix of breast cancer cells and stem cells from the women’s fat. After 36 days, the mice had developed tumours. Those associated with stem cells from obese women were 1.78 cubic centimetres in volume, more than twice the size of those associated with the stem cells from the slim women (Breast Cancer Research, doi.org/pt3).

Bunnell thinks excess fat causes inflammation, making stem cells release growth factors that help the tumour expand.

This article appeared in print under the headline “Cancer fattens fast with ‘fat’ stem cells”.

For similar stories, visit the In Brief , Cancer and Stem Cells .