Liver stem cells and hepatocellular carcinoma.
Although the existence of cancer stem cells (CSCs) was first proposed over 40 years ago, only in the past decade have these cells been identified in hematological malignancies, and more recently in solid tumors that include liver, breast, prostate, brain, and colon. Constant proliferation of stem cells is a vital component in liver tissues. In these renewing tissues, mutations will most likely result in expansion of the altered stem cells, perpetuating and increasing the chances of additional mutations and tumor progression. However, many details about hepatocellular cancer stem cells that are important for early detection remain poorly understood, including the precise cell(s) of origin, molecular genetics, and the mechanisms responsible for the highly aggressive clinical picture of hepatocellular carcinoma (HCC). Exploration of the difference between CSCs from normal stem cells is crucial not only for the understanding of tumor biology but also for the development of specific therapies that effectively target these cells in patients. These ideas have drawn attention to control of stem cell proliferation by the transforming growth factor beta (TGF-beta), Notch, Wnt, and Hedgehog pathways. Recent evidence also suggests a key role for the TGF-beta signaling pathway in both hepatocellular cancer suppression and endoderm formation, suggesting a dual role for this pathway in tumor suppression as well as progression of differentiation from a stem or progenitor stage. This review provides a rationale for detecting and analyzing tumor stem cells as one of the most effective ways to treat cancers such as HCC.
Mishra
Lopa
L
Laboratory of Cancer Genetics, Digestive Diseases, and Developmental Molecular Biology, Department of Surgery, Lombardi Comprehensive Cancer Center, Georgetown University, Washington, DC 20007, USA. lm229@georgetown.edu
Banker
Tanuj
T
Murray
Joseph
J
Byers
Stephen
S
Thenappan
Arun
A
He
Aiwu Ruth
AR
Shetty
Kirti
K
Johnson
Lynt
L
Reddy
E P
EP
D015415:Biomarkers / Q000032:analysis; D006528:Carcinoma, Hepatocellular / Q000473:pathology / Q000628:therapy*; D019070:Cell Lineage; D053595:Embryonic Stem Cells / Q000166:cytology; D053823:Hedgehog Proteins / Q000502:physiology; D006801:Humans; D008099:Liver / Q000166:cytology / Q000254:growth & development; D008115:Liver Regeneration / Q000502:physiology; D016031:Liver Transplantation; D019520:Living Donors; D008297:Male; D014411:Neoplastic Stem Cells / Q000473:pathology* / Q000502:physiology; D011379:Prognosis; D051880:Receptors, Notch / Q000502:physiology; D015398:Signal Transduction / Q000502:physiology; D016212:Transforming Growth Factor beta / Q000502:physiology; D051153:Wnt Proteins / Q000502:physiology; D051176:beta Catenin / Q000502:physiology
D015415:Biomarkers; D053823:Hedgehog Proteins; D051880:Receptors, Notch; D016212:Transforming Growth Factor beta; D051153:Wnt Proteins; D051176:beta Catenin