Search

Objectives: Fibroblast growth factor receptor 3 ( FGFR3) is a proto-oncogene that is often dysregulated together with multiple myeloma SET-domain (MMSET) by the immunoglobulin heavy chain (IGH) gene in t(4;14)pos multiple myeloma (MM) cells, and which is usually not expressed in MM cells without this translocation. Whether FGFR3 may play a role in MM cells without t(4;14) and the IGH-MMSET fusion protein is unclear and is the focus of this report. Methods: FGFR3 expression was explored in cell lines with and without t(4;14) by fluorescence in situ hybridization (FISH), RT-PCR and Western Blot. FGFR3 inhibitors SU5402 and PD173074 were used to explore the role of FGFR3 in these cells. Results: We discovered an amplification of the FGFR3 locus in INA-6, a human MM cell line. We also demonstrated expression of FGFR3 mRNA and protein in the cells, probably caused by the extra copy of the gene. INA-6 cells did not have t(4;14) and neither was there any involvement of the other IG loci in translocations with the FGFR3 gene. The FGFR3 inhibitors decreased the proliferation of INA-6. Conclusion: The decreased viability and proliferation in INA-6, following inhibition with FGFR3 inhibitors, indicates that FGFR3 may play a role also in cells without t(4;14) – and hence without high expression of MMSET, the ubiquitous oncoprotein in MM cells with t(4;14). This gives further credibility to the notion that FGFR3 expression is not just an epiphenomenon in t(4;14) MM, but an important part of the malignant phenotype. [ABSTRACT FROM AUTHOR]

Multiple myeloma is a hematological cancer that is considered incurable despite advances in treatment strategy during the last decade. Therapies targeting single pathways are unlikely to succeed due to the heterogeneous nature of the malignancy. Proliferating cell nuclear antigen (PCNA) is a multifunctional protein essential for DNA replication and repair that is often overexpressed in cancer cells. Many proteins involved in the cellular stress response interact with PCNA through the five amino acid sequence AlkB homologue 2 PCNA-interacting motif (APIM). Thus inhibiting PCNA’s protein interactions may be a good strategy to target multiple pathways simultaneously. We initially found that overexpression of peptides containing the APIM sequence increases the sensitivity of cancer cells to contemporary therapeutics. Here we have designed a cell-penetrating APIM-containing peptide, ATX-101, that targets PCNA and show that it has anti-myeloma activity. We found that ATX-101 induced apoptosis in multiple myeloma cell lines and primary cancer cells, while bone marrow stromal cells and primary healthy lymphocytes were much less sensitive. ATX-101-induced apoptosis was caspase-dependent and cell cycle phase-independent. ATX-101 also increased multiple myeloma cells’ sensitivity against melphalan, a DNA damaging agent commonly used for treatment of multiple myeloma. In a xenograft mouse model, ATX-101 was well tolerated and increased the anti-tumor activity of melphalan. Therefore, targeting PCNA by ATX-101 may be a novel strategy in multiple myeloma treatment. [ABSTRACT FROM AUTHOR]

Objectives: Hepatocyte growth factor (HGF) is a constituent of the myeloma microenvironment and is elevated in sera from myeloma patients compared to healthy individuals. Increased levels of serum HGF predict a poor prognosis. It has previously been shown by us and others HGF can act as a growth factor to myeloma cells in vitro although these effects have been moderate. We therefore wanted to investigate if HGF could influence the effects of interleukin (IL)-6. Methods: Myeloma cell lines and primary samples were tested for the combined effects of IL-6 and HGF in inducing DNA synthesis and migration. Expression levels of c-Met protein were analysed by Western blotting and flow cytometry. Signaling pathways were examined by Western blotting using phosphospecific antibodies and a Ras-GTP pull down assay. Results: HGF potentiated IL-6-induced growth in human myeloma cell lines and in purified primary myeloma cells. There was also cooperation between HGF and IL-6 in induction of migration. There seemed to be two explanations for this synergy. IL-6-treatment increased the expression of c-Met making cells HGF responsive, and IL-6 was dependent on c-Met signaling in activating both Ras and p44/42 MAPK by a mechanism involving the tyrosine phosphatase Shp2. Conclusions: The results indicate that besides from being a myeloma growth factor alone, HGF can also potentiate the effects of IL-6 in myeloma proliferation and migration. Thus, c-Met signaling could be a target for therapy of multiple myeloma. [ABSTRACT FROM AUTHOR]