Cancer therapy: Defining stemness

Hans Clevers in Nature:

StemI have always felt uncomfortable about the concepts and definitions that we use in the stem-cell field. Some of the arguments seem circular; observation and assumption are not well separated. I once asked a colleague for their best definition of a stem cell. The answer: a cell that can self-renew. What, then, is self-renewal? The immediate reply: what stem cells do. Fuzziness in stem-cell concepts and definitions has significant consequences. It affects how we design, conduct and interpret experiments, how we communicate our discoveries and, ultimately, how we design therapies aimed at supporting the regenerative capacity of healthy stem cells or eradicating those that fuel the growth of tumours. Despite these concerns, as an experimentalist I could never put my finger on where exactly scientific common sense is failing.

Enter Lucie Laplane and her book Cancer Stem Cells. Trained as a science philosopher, Laplane also spent time at the bench in two stem-cell labs. Her book is the culmination of a six-year effort to describe and structure the philosophical underpinnings of stem-cell science. In addition to absorbing essentially all the relevant experimental literature — historical and scientific — she interviewed some of the leading international stem-cell researchers and clinicians. She discussed her emerging insights with fellow philosophers and science historians. Starting from an interest in cancer stem cells (CSCs), the book, despite its title, builds a much broader framework for understanding the biology of stem cells of all types. Central to CSC theory is the observation that not all tumour cells are equal. The bulk of a tumour consists of short-lived proliferative cells and differentiated cells. But some tumour cells seem to be the malignant equivalents of tissue stem cells. Much as normal stem cells maintain healthy organs by producing new tissue cells, CSCs drive the persistence of malignant tumours by producing new cancer cells.

More here.