Genomic profiles associated with early micrometastasis in lung cancer: relevance of 4q deletion.
OBJECTIVE
Bone marrow is a common homing organ for early disseminated tumor cells (DTC) and their presence can predict the subsequent occurrence of overt metastasis and survival in lung cancer. It is still unclear whether the shedding of DTC from the primary tumor is a random process or a selective release driven by a specific genomic pattern.


METHODS
DTCs were identified in bone marrow from lung cancer patients by an immunocytochemical cytokeratin assay. Genomic aberrations and expression profiles of the respective primary tumors were assessed by microarrays and fluorescence in situ hybridization analyses. The most significant results were validated on an independent set of primary lung tumors and brain metastases.


RESULTS
Combination of DNA copy number profiles (array comparative genomic hybridization) with gene expression profiles identified five chromosomal regions differentiating bone marrow-negative from bone marrow-positive patients (4q12-q32, 10p12-p11, 10q21-q22, 17q21, and 20q11-q13). Copy number changes of 4q12-q32 were the most prominent finding, containing the highest number of differentially expressed genes irrespective of chromosomal size (P=0.018). Fluorescence in situ hybridization analyses on further primary lung tumor samples confirmed the association between loss of 4q and bone marrow-positive status. In bone marrow-positive patients, 4q was frequently lost (37% versus 7%), whereas gains could be commonly found among bone marrow-negative patients (7% versus 17%). The same loss was also found to be common in brain metastases from both small and non-small cell lung cancer patients (39%).


CONCLUSIONS
Thus, our data indicate, for the first time, that early hematogenous dissemination of tumor cells might be driven by a specific pattern of genomic changes.
Wrage
Michaela
M
Institute of Tumor Biology and Department of General, Visceral and Thoracic Surgery, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
Ruosaari
Salla
S
Eijk
Paul P
PP
Kaifi
Jussuf T
JT
Hollmén
Jaakko
J
Yekebas
Emre F
EF
Izbicki
Jakob R
JR
Brakenhoff
Ruud H
RH
Streichert
Thomas
T
Riethdorf
Sabine
S
Glatzel
Markus
M
Ylstra
Bauke
B
Pantel
Klaus
K
Wikman
Harriet
H
D000230:Adenocarcinoma / Q000235:genetics / Q000556:secondary; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001932:Brain Neoplasms / Q000235:genetics* / Q000556:secondary; D018287:Carcinoma, Large Cell / Q000235:genetics / Q000556:secondary; D002294:Carcinoma, Squamous Cell / Q000235:genetics / Q000556:secondary; D002872:Chromosome Deletion; D002894:Chromosomes, Human, Pair 4 / Q000235:genetics*; D055028:Comparative Genomic Hybridization; D005260:Female; D018628:Gene Dosage; D020869:Gene Expression Profiling; D015894:Genome, Human; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D008175:Lung Neoplasms / Q000235:genetics* / Q000473:pathology; D008207:Lymphatic Metastasis; D008297:Male; D008875:Middle Aged; D020411:Oligonucleotide Array Sequence Analysis; D055752:Small Cell Lung Carcinoma / Q000235:genetics / Q000556:secondary