Suppose you are studying tumor heterogeneity in a certain type of melanoma. You have used fluorescence-activated cell sorting (FACS) to specifically isolate those melanoma tumor cells that either do (first category) or do not (second category) express a specific marker present in normal stem cells in the tissue of origin (i.e. the melanocyte stem cells). You implant the same number of cells from each of these categories into severely immunodeficient mice and compare the tumor-formation efficiencies after several weeks, which turn out to be significantly higher for the first category. You then analyze the new tumors using FACS, and find out that the majority of the cells in the tumors that originated from the first category of cells harbor the stem-cell marker, whereas the majority of the cells in the tumors that originated from the second cell category lack the marker, just like their respective founder cells. Do these observations support the existence of cancer stem cells? Write down Yes or No as your answer.

Question

Quizplus · Accepted Answer

Cancer stem cells are expected to constitute a minority of the tumor cell population. Even though the transplantation is more efficient with the subpopulation of cells that expresses the stem-cell marker, this might simply reflect the heterogeneity in the original tumor, with these cells harboring a higher ability to found new tumors.

Suppose You Are Studying Tumor Heterogeneity in a Certain Type