Abstracts (poster) - Wissenschaft Online

Harriet Wikman, Michaela Kraemling, Dirk Kemming, Klaus Pantel
Identification of Target Genes in Micrometastatic Lung Cancer
by Methylation Arrays
We have recently identified specific molecular patterns associated with the presence of
disseminated tumor cells (DTCs) in the bone marrow (BM) in patients with primary early
stage lung cancer. We performed a combined expression and copy number (CGH)
profiling of primary lung tumors, and detected five chromosomal regions differentiating
BM-negative from BM-positive patients. Heterozygotic loss of chromosome 4q12-q32 in
BM-positive patients was the most prominent finding. The same loss was also found to
be common in brain metastases from lung cancer patients. The 4q region spanned over
107.1 Mbp and contained 73 differentially expressed genes. In order to narrow down the
potential target gene in this region, a methylation array-screening was performed. 3
lung cancer cell lines showing loss of 4q were treated with 5-aza-2' deoxycytidine, a
demethylating agent. By comparing the mRNA expression of treated and non-treated cell
line one can identify genes silenced through methylation. As a control for cellular stress
a normal bronchial epithelial cell line was used. Treatments were done in triplicate and
RNA was pooled before the competitive hybridization on Agilent 4x44K arrays. All
together 620 genes were found 2-fold up-regulated in at least two of the cancer cell lines
but not in the control cell line. Of these genes 12 are located to the 4q12-q32. 5 genes
were excluded as no expression could be detected in normal lung tissue or no differential
expression could be found between normal and tumor tissue. We are currently mapping
the methylation sites of the 7 remaining potential target genes and will perform MSI-PCR
on primary lung tumors in order to verify the findings and map down the possible target
gene on 4q responsible for the early micrometastatic spread of lung cancer.
contact:
Dr Harriet Wikman
University Medical Center Hamburg-Eppendorf
Intst. Tumor Biology
h.wikman@uke.uni-hamburg.de
Martinistrasse 52
20246 Hamburg (Germany)