Prognostic significance of tumorigenic cells with mesenchymal features in pancreatic adenocarcinoma.
BACKGROUND
Specific populations of highly tumorigenic cells are thought to exist in many human tumors, including pancreatic adenocarcinoma. However, the clinical significance of these tumor-initiating (ie, cancer stem) cells remains unclear. Aldehyde dehydrogenase (ALDH) activity can identify tumor-initiating cells and normal stem cells from several human tissues. We examined the prognostic significance and functional features of ALDH expression in pancreatic adenocarcinoma.


METHODS
ALDH expression was analyzed by immunohistochemistry in 269 primary surgical specimens of pancreatic adenocarcinoma and examined for association with clinical outcomes and in paired primary tumors and metastatic lesions from eight pancreatic cancer patients who had participated in a rapid autopsy program. The clonogenic growth potential of ALDH-positive pancreatic adenocarcinoma cells was assessed in vitro by a colony formation assay and by tumor growth in immunodeficient mice (10-14 mice per group). Mesenchymal features of ALDH-positive pancreatic tumor cells were examined by using quantitative reverse transcription-polymerase chain reaction and an in vitro cell invasion assay. Gene expression levels and the invasive potential of ADLH-positive pancreatic cancer cells relative to the bulk cell population were examined by reverse transcription-polymerase chain reaction and an in vitro invasion assays, respectively. All statistical tests were two-sided.


RESULTS
ALDH-positive tumor cells were detected in 90 of the 269 primary surgical specimens, and their presence was associated with worse survival (median survival for patients with ALDH-positive vs ALDH-negative tumors: 14 vs 18 months, hazard ratio of death = 1.28, 95% confidence interval = 1.02 to 1.68, P = .05). Six (75%) of the eight patients with matched primary and metastatic tumor samples had ALDH-negative primary tumors, and in four (67%) of these six patients, the matched metastatic lesions (located in liver and lung) contained ALDH-positive cells. ALDH-positive cells were approximately five- to 11-fold more clonogenic in vitro and in vivo compared with unsorted or ALHD-negative cells, expressed genes consistent with a mesenchymal state, and had in vitro migratory and invasive potentials that were threefold greater than those of unsorted cells.


CONCLUSIONS
ALDH expression marks pancreatic cancer cells that have stem cell and mesenchymal features. The enhanced clonogenic growth and migratory properties of ALDH-positive pancreatic cancer cells suggest that they play a key role in the development of metastatic disease that negatively affects the overall survival of patients with pancreatic adenocarcinoma.
Rasheed
Zeshaan A
ZA
The Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA.
Yang
Jie
J
Wang
Qiuju
Q
Kowalski
Jeanne
J
Freed
Irwin
I
Murter
Christopher
C
Hong
Seung-Mo
SM
Koorstra
Jan-Bart
JB
Rajeshkumar
N V
NV
He
Xiaobing
X
Goggins
Michael
M
Iacobuzio-Donahue
Christine
C
Berman
David M
DM
Laheru
Daniel
D
Jimeno
Antonio
A
Hidalgo
Manuel
M
Maitra
Anirban
A
Matsui
William
W
D000230:Adenocarcinoma / Q000201:enzymology* / Q000401:mortality / Q000473:pathology*; D000444:Aldehyde Dehydrogenase / Q000378:metabolism*; D000818:Animals; D045744:Cell Line, Tumor; D002465:Cell Movement; D005434:Flow Cytometry; D015971:Gene Expression Regulation, Enzymologic; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007150:Immunohistochemistry; D016015:Logistic Models; D008648:Mesoderm; D051379:Mice; D046228:Microarray Analysis; D015999:Multivariate Analysis; D009361:Neoplasm Invasiveness; D014411:Neoplastic Stem Cells; D010190:Pancreatic Neoplasms / Q000201:enzymology* / Q000401:mortality / Q000473:pathology*; D011237:Predictive Value of Tests; D011379:Prognosis; D016016:Proportional Hazards Models; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014183:Transplantation, Heterologous; D014410:Tumor Stem Cell Assay
D000444:Aldehyde Dehydrogenase