To gain new insights into the functional interaction between DC and neoplastic cells, we have analyzed the effects of
melanoma and
colorectal cancer lines on the chemotaxis and the phenotype of monocyte-derived DC in vitro. Both types of
tumor cells displayed effective chemoattractive capacity towards immature, but not mature DC. Furthermore,
conditioned medium of discrete
melanoma lines induced upregulation of CD80, CD86, MHC class I, and
MHC class II molecules on immature DC. However, de novo expression of
E-cadherin and strong upregulation of CD15 could also be detected in the absence of CD83 expression.
Melanoma-conditioned DC exhibited an increased adhesion capacity to a
melanoma cell line in vitro and did not migrate in response to
SLC chemokine.
Tumor-infiltrating CD15(+) cells displaying DC morphology could also be detected by immunohistochemistry in the original
tumor specimens from which discrete
melanoma cell lines under investigation were derived.
Colorectal cancer cell lines, although able to chemoattract immature DC, were apparently unable to modulate their phenotype. Altogether our results suggest that
tumor cells can attract immature DC in vitro and, eventually, modulate their phenotype. As a result, DC mobility could be severely impaired.