It's no secret that being overweight increases the chances of negative outcomes for cancer patients and now researchers from the University of Colorado Cancer Center may have uncovered a possible explanation for this. They found that leukemia stem cells can thrive in a patient's fatty tissue, which the cells can transform into a supportive hideout that makes them more resistant to chemotherapy treatments.

When examining a mouse model of leukemia, rather than the expected mix of regular cancer cells and cancer stem cells, the researchers noticed the fatty tissue had a disproportionately high ratio of cancer stem cells and they were able to adapt to this environment by manufacturing energy through fatty acid oxidation. More than this, the cancer stem cells actively tailor the fatty tissue environment to suit their needs by signaling the fatty tissue to undergo a process called lipolysis in which fatty acids are released.

When the researchers finally tried to fight these cancerous cells with chemotherapy, they found the stem cells in the fatty tissue that were using fatty acids as their energy source were more resistant to the treatment compared to cancer stem cells located outside the fatty tissue. The team also found similar characteristics in samples of human leukemia, finding cancer stem cells powering themselves with fatty acids that were more resistant to chemotherapy.

"It's been increasingly appreciated that cancer can originate in stem cells and that failing to kill cancer stem cells can lead to relapse," says Craig Jordan, an investigator at the University of Colorado Cancer Center who co-authored the study. "Researchers have also come to appreciate the importance of surrounding tissues – the 'niche' or tumor microenvironment – in supporting cancer stem cells. In leukemia, the obvious niche is the bone marrow, but little attention has been paid to other sites in the body. This study is one of the first to evaluate adipose tissue, fat, as a possible tumor-supporting niche."

Further study is still needed to determine if having more fatty issue provides more energy to the cancer stem cells or if it simply provides a large space for the cells to hide from chemotherapy treatments.

The team's study was published in the journal Cell Stem Cell.