"So what have the cancer cells been doing during those five years? Now we have a partial answer---they've been sitting in this place whose job it is to keep things from proliferating and growing," Taichman said.
"Our work also provides an explanation as to why current chemotherapies often fail in that once cancer cells enter the niche, most likely they stop proliferating," said Yusuke Shiozawa, lead author of the study. "The problem is that most of the drugs we use to try to treat cancer only work on cells that are proliferating."
Metastases are the most common malignant tumors involving the skeleton, and nearly 70 percent of patients with breast and prostate cancer have bone involvements. Roughly 15 percent to 30 percent of patients with lung, colon, stomach, bladder, uterus, rectum, thyroid or kidney cancer have bone lesions.
Researchers aren't quite sure how the cancer cells out-compete the stem cells in the niche. However, they do know the stem cells were displaced because when cancer cells were in the niche scientists also found evidence of immature blood stem cells in the blood stream, instead of in the marrow where they were supposed to be, Taichman said.
"Eventually the entire blood system is going to collapse," he said. "For example, the patient ultimately becomes anemic, gets infections, and has bleeding problems. We really don't know why people with prostate cancer die. They end up dying from different kinds of complications in part because the marrow is taken over by cancer."
The next step is to find out how the tumor cell gets into the niche and becomes dormant, and exactly what they do to the stem cells when they are there. Researchers also want to know if other types of cancer cells, such as breast cancer, also go to the niche.
The study, "Prostate Cancer Metastases Target the Hematopoietic Stem Cell Niche to E
|Contact: Laura Bailey|
University of Michigan