CCN3/
nephroblastoma overexpressed belongs to the CCN family of genes that encode secreted
proteins associated with the extracellular matrix (ECM) and exert regulatory effects at the cellular level. Overexpression of CCN3 was shown in metastatic
melanoma cells compared with cells of the primary
tumor from the same patient. Analysis of short-term cultures from 50 primary and metastatic
melanomas revealed a heterogeneous expression pattern of both the 46-kDa full-length cytoplasmic/secreted
protein and the 32-kDa nuclear-truncated form. The different
protein expression patterns were not associated with gene alterations or polymorphisms. Like the metastatic cells expressing high levels of the 46-kDa CCN3, cells transfected to overexpress CCN3 showed increased adhesion to ECM
proteins, whereas inhibition of CCN3 expression by
small interfering RNA decreased adhesion to
laminin and
vitronectin. CCN3 overexpression induced increased expression of
laminin and
vitronectin integrin receptors alpha 7 beta 1 and alpha v beta 5 by increasing their
mRNA production. Moreover, CCN3 secreted by
melanoma cells acted as an adhesion matrix
protein for
melanoma cells themselves. Analysis of
CCN3 protein expression with respect to
melanoma progression detected the
protein in all visceral
metastases tested and in most nodal
metastases from relapsing patients but in only a few nodal
metastases from nonrelapsing patients and cutaneous
metastases. Consistently,
xenotransplantation in immunodeficient mice showed a higher metastatic potential of
melanoma cells overexpressing CCN3. Together, these data indicate a role for CCN3 in
melanoma cell interaction with the ECM by regulating
integrin expression, resulting in altered cell adhesion and leading
melanoma progression to aggressive disease.