Comparative Cell Biological Analyses of Proto-Type Galectins in Colon Cancer

Galectins are a family of endogenous sugar-binding receptors
(lectins). They influence adhesion, growth and invasion in cancer.
The clinical relevance of these prominent parameters prompts the
question, whether expression profiles of galectins may correlate
with distinct cell properties. Noteworthy in this respect,
homodimeric proto-type galectins regulate e.g. neuroblastoma cell
growth, and the expression of one of these galectins (galectin-7)
is enhanced upon p53-induced apoptosis. These facts explain the
given focus on the proto-type galectins-1, -2 and -7. As a key step
towards answering the question posed above, establishment of
genetically engineered variants of cell lines with ectopic
expression of these lectins is required. Their availability will
then allow to evaluate whether and to what extent these homologous
galectins can contribute to the malignant phenotype in colon
cancer. Therefore, galectin-specific cDNA was inserted into a
vector (pcDNA3.1), which was then stably incorporated into the
genome of cells of established colon carcinoma cell lines (HCT-15,
DLD-1). This was verified by PCR analysis on genomic DNA.
Systematic measurements on the levels of mRNA and protein
ascertained gene activity and galectin synthesis. Their presence
was identified on the cell surface as well as in cytoplasm and
nucleus by fluorescence-activated cell sorting and
immunocytochemical analysis, respectively. These results furnish
first evidence on nuclear presence of galectins-2 and -7 in colon
cancer cells. Morphological appearance and cell growth without or
with chemotherapeuticals (oxaliplatin, irinotecan, SN-38) were not
significantly influenced. Overall, the successfully generated
clones with stable ectopic lectin expression are valuable tools for
further examining the correlation between galectins and tumor
biologically relevant parameters.