John C. Morris and colleagues from the University of Cincinnati Cancer Institute have succeeded in isolating lung cancer stem cells and growing them in the laboratory. These findings should provide scientists with a new model system for testing therapeutic strategies that target cancer stem cells.
According to Morris, “Increasing evidence supports the idea that cancerous tumors have a population of stem cells, also called cancer-initiating cells that continually regenerate and fuel cancer growth. These cancer stem cells may also have the highest potential to spread to other organs.”
We normally think of cancer as a disease in which almost all the cells of a tumor have capacity to propagate the tumor. Treating cancer with drugs that attack dividing cells in general is very different that treating a small subset of cells in the cancer that propagate the tumor. Also, new therapies focus on the interaction between the immune system and the cancer. If the only target that the immune needs to recognize is the cancer stem cells, then the therapeutic strategy changes substantially.
Morris and his colleagues used a technique called the “tumor-sphere” assay. This assay evaluates floating non-adherent cell aggregates that form in cultures of cancer cells, when grown under conditions that do not promote cell adhesion. Such clumps of cells are a surrogate for tumors, since they appear to mirror the cellular architecture and composition and behavior of in tumors. Additionally, these clumps are enriched for cancer stem cells.
Morris said: “Studying these unique cells could greatly improve our understanding of lung cancer’s origins and lead to the novel therapeutics targeting these cells and help to more effectively eradicate this disease.” Morris continued: “Immunotherapy is the future of cancer treatment. We are hopeful that this new method will accelerate our investigation of immunotherapies to specifically target cancer stem cells.”
Morris’ group is interested in how cancer stem cells escape the body’s immune system in order to develop more effective therapies that target stem cells.
“One of the hypotheses behind why cancer therapies fail is that the drug only kills cells deemed to be ‘bad’ (because of certain molecular characteristics), but leaves behind stem cells to repopulate the tumor,” said Morris. “Stem cells are not frequently dividing, so they are much less sensitive to existing chemotherapies used to eliminate cells deemed abnormal.”