Obesity may be contributing to chemotherapy resistance and increasing relapse rates among children with leukemia. Obesity is associated with anncreased incidence of many types of cancer drugs. Given the increasing prevalence of obesity worldwide, these findings could have important implications for cancer treatment and may help to explain the increased leukemia relapse rate in obese patients.
Steven D. Mittelman, MD, PhD, from the University of Southern California, says that the fat cells themselves may impair the immune system’s ability to block cancer growth or might predispose cells to become cancerous.
Dr. Mittelman and colleagues developed a mouse model of obesity and leukemia, cultured fat and leukemia cells together, and treated the leukemia cells with traditional chemotherapy used in children—vincristine, nilotinib, daunorubicin, and dexamethasone. Obese mice with leukemia had higher relapse rates than lean mice after treatment with vincristine. Chemotherapy worked less effectively in culture when fat cells were nearby. When relapse occurred, the researchers observed that leukemia was “hiding out” in the fat tissue during chemotherapy.
“These four drugs attack leukemia cells by different routes, so when we saw fat cells blocking them, we realized there could be an important mechanism promoting their ability to live and divide,” Dr. Mittelman said. “We were surprised to find leukemia cells in the fat tissue.”
The study suggested that obesity is associated with a poor prognosis in multiple cancers. In another study, adipose tissue seemed to function as a “safe haven” for leukemia cells during therapy. More research is needed to learn how fat cells are a part of the tumor microenvironment and how they block potentially lifesaving treatments.
Sources: Cancer Res online; Science Codex, September 22, 2009