Hypoxia increases membrane metallo-endopeptidase expression in a novel lung cancer ex vivo model - role of tumor stroma cells.
BACKGROUND
Hypoxia-induced genes are potential targets in cancer therapy. Responses to hypoxia have been extensively studied in vitro, however, they may differ in vivo due to the specific tumor microenvironment. In this study gene expression profiles were obtained from fresh human lung cancer tissue fragments cultured ex vivo under different oxygen concentrations in order to study responses to hypoxia in a model that mimics human lung cancer in vivo.


METHODS
Non-small cell lung cancer (NSCLC) fragments from altogether 70 patients were maintained ex vivo in normoxia or hypoxia in short-term culture. Viability, apoptosis rates and tissue hypoxia were assessed. Gene expression profiles were studied using Affymetrix GeneChip 1.0 ST microarrays.


RESULTS
Apoptosis rates were comparable in normoxia and hypoxia despite different oxygenation levels, suggesting adaptation of tumor cells to hypoxia. Gene expression profiles in hypoxic compared to normoxic fragments largely overlapped with published hypoxia-signatures. While most of these genes were up-regulated by hypoxia also in NSCLC cell lines, membrane metallo-endopeptidase (MME, neprilysin, CD10) expression was not increased in hypoxia in NSCLC cell lines, but in carcinoma-associated fibroblasts isolated from non-small cell lung cancers. High MME expression was significantly associated with poor overall survival in 342 NSCLC patients in a meta-analysis of published microarray datasets.


CONCLUSIONS
The novel ex vivo model allowed for the first time to analyze hypoxia-regulated gene expression in preserved human lung cancer tissue. Gene expression profiles in human hypoxic lung cancer tissue overlapped with hypoxia-signatures from cancer cell lines, however, the elastase MME was identified as a novel hypoxia-induced gene in lung cancer. Due to the lack of hypoxia effects on MME expression in NSCLC cell lines in contrast to carcinoma-associated fibroblasts, a direct up-regulation of stroma fibroblast MME expression under hypoxia might contribute to enhanced aggressiveness of hypoxic cancers.
Katharina
K
Leithner
Christoph
C
Wohlkoenig
Elvira
E
Stacher
Jörg
J
Lindenmann
Nicole A
NA
Hofmann
Birgit
B
Gallé
Christian
C
Guelly
Franz
F
Quehenberger
Philipp
P
Stiegler
Freyja-Maria
FM
Smolle-Jüttner
Sjaak
S
Philipsen
Helmut H
HH
Popper
Andelko
A
Hrzenjak
Andrea
A
Olschewski
Division of Pulmonology, Department of Internal Medicine, Medical University of Graz, Auenbruggerplatz 20, A-8036 Graz, Austria. horst.olschewski@medunigraz.at.
Horst
H
Olschewski
D017209:Apoptosis; D014408:Biomarkers, Tumor / Q000235:genetics / Q000378:metabolism*; D002289:Carcinoma, Non-Small-Cell Lung / Q000201:enzymology* / Q000235:genetics / Q000401:mortality / Q000473:pathology; D015687:Cell Hypoxia; D045744:Cell Line, Tumor; D002470:Cell Survival; D005347:Fibroblasts / Q000201:enzymology* / Q000473:pathology; D020869:Gene Expression Profiling / Q000379:methods; D015971:Gene Expression Regulation, Enzymologic; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008175:Lung Neoplasms / Q000201:enzymology* / Q000235:genetics / Q000401:mortality / Q000473:pathology; D015260:Neprilysin / Q000235:genetics / Q000378:metabolism*; D020411:Oligonucleotide Array Sequence Analysis; D017154:Stromal Cells / Q000201:enzymology* / Q000473:pathology; D046509:Tissue Culture Techniques; D015854:Up-Regulation
D014408:Biomarkers, Tumor; D015260:Neprilysin