Overexpression of CCN3 was detected in metastatic melanoma cells as compared to cells of the primary tumor from the same patient. Analysis of CCN3 in short-term cultures from 50 melanoma lesions revealed a heterogeneous expression of the 46 kDa full-length protein and the 32 kDa truncated form. In fact, some melanomas were negative for CCN3 expression, while others expressed both isoforms at the cellular level and secreted in the culture medium. Other melanomas displayed only the full-length or only the short isoform with or without protein secretion. The different protein expression patterns were not associated with alternative transcripts, gene alterations or polymorphisms. Cell fractions and immunofluorescence analysis demonstrated that the 46 kDa protein has a prevalent cytoplasmic localization, while the 32 kDa form has a nuclear localization and lacked the N-terminal domain. Similarly to metastatic cells expressing high levels of CCN3, cells transfected to overexpress CCN3, despite a reduction in cell proliferation, showed increased adhesion to extracellular matrix (ECM) proteins, particularly laminin and vitronectin, while inhibition of CCN3 expression by siRNA decreased adhesion. CCN3 overexpression increased expression of laminin and vitronectin integrin (ITG) receptors α7β1 and αvβ5 by increasing their mRNA production. Moreover, CCN3 secreted by melanoma cells acted as an adhesion matrix protein for melanoma cells themselves. Immunohistochemistry performed on melanoma specimens from which the cell lines were derived confirmed that the different levels of expression occurring in vivo are maintained in cultured cells. 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 only in a few nodal metastases from non-relapsing patients and cutaneous metastases. Consistently, xenotransplantation in immunodeficient mice showed a higher metastatic potential of melanoma cells overexpressing CCN3. CCN3-transfected cells showed a higher resistance to apoptosis induced by treatment with cytotoxic drugs. Taken together, these data indicate a role for CCN3 in melanoma cell interaction with the ECM by regulating ITG expression, resulting in altered cell adhesion and increased chemoresistance, leading melanoma progression to aggressive disease.
|Title of host publication||CCN Proteins in Health and Disease: An Overview of the Fifth International Workshop on the CCN Family of Genes|
|Number of pages||7|
|Publication status||Published - 2010|
- Cell adhesion
- Integrin α7β1 and αvβ5
ASJC Scopus subject areas