Tumorigenic Epithelial Stem Cells and Their Normal Counterparts
ABC transporters are highly conserved and represent a major protective mechanism for barrier tissues as well as adult tissue stem cells. Emerging data support the existence of a cancer stem cell that shares features of tissue stem cells, including the ability to self-renew and undergo dysregulated differentiation. Here we show that a rare population of cells coexpressing MDR transporters and stem cell markers is a common feature across therapy-naive epithelial cancers as well as normal epithelial tissue. MDR+ and MDR− candidate tumor stem and progenitor populations were all capable of generating highly anaplastic transplantable human tumors in NOD/SCID. The finding that rare cells bearing stem cell markers and having intrinsic MDR expression and activity are already present within the tumorigenic compartment before treatment with cytotoxic agents is of critical importance to cancer therapy. Just as damaged normal epithelial tissues regenerate after chemotherapy by virtue of highly protected resting tissue stem cells, the existence of malignant counterparts in therapy-naive epithelial cancers suggests a common mechanism by which normal and tumor stem cells protect themselves against toxic injury.
KeywordsCancer Stem Cell Stem Cell Marker Normal Lung Tissue Multiple Drug Resistance Epithelial Stem Cell
Supported by Grants BC032981 and BC044784 from the Department of Defense, the Hillman Foundation, and The Glimmer of Hope Foundation. Vera S. Donnenberg is the recipient of a Department of Defense Era of Hope Scholar Award.
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