BackgroundThe Odontogenic Ameloblast-associated Protein (ODAM) is expressed in a wide range of normal epithelial, and neoplastic tissues, and we have posited that ODAM serves as a novel prognostic biomarker for breast cancer and melanoma. Transfection of ODAM into breast cancer cells yields suppression of cellular growth, motility, and in vivo tumorigenicity. Herein we have extended these studies to the effects of ODAM on cultured melanoma cell lines.MethodsThe A375 and C8161 melanoma cell lines were stably transfected with ODAM and assayed for properties associated with tumorigenicity including cell growth, motility, and extracellular matrix adhesion. In addition, ODAM–transfected cells were assayed for signal transduction via AKT which promotes cell proliferation and survival in many neoplasms.ResultsODAM expression in A375 and C8161 cells strongly inhibited cell growth and motility in vitro, increased cell adhesion to extracellular matrix, and yielded significant cytoskeletal/morphologic rearrangement. Furthermore, AKT activity was downregulated by ODAM expression while an increase was noted in expression of the PTEN (phosphatase and tensin homolog on chromosome 10) tumor suppressor gene, an antagonist of AKT activation. Increased PTEN in ODAM-expressing cells was associated with increases in PTEN mRNA levels and de novo protein synthesis. Silencing of PTEN expression yielded recovery of AKT activity in ODAM-expressing melanoma cells. Similar PTEN elevation and inhibition of AKT by ODAM was observed in MDA-MB-231 breast cancer cells while ODAM expression had no effect in PTEN-deficient BT-549 breast cancer cells.ConclusionsThe apparent anti-neoplastic effects of ODAM in cultured melanoma and breast cancer cells are associated with increased PTEN expression, and suppression of AKT activity. This association should serve to clarify the clinical import of ODAM expression and any role it may serve as an indicator of tumor behavior.

Objectives Morbidity and mortality occurring in patients with multiple myeloma, AL amyloidosis, and light chain deposition disease can result from the pathologic deposition of monoclonal Ig light chains (LCs) in kidneys and other organs. To reduce synthesis of such components, therapy for these disorders typically has involved anti-plasma cell agents; however, this approach is not always effective and can have adverse consequences. We have investigated another means to achieve this objective; namely, RNA interference (RNAi). Materials and Methods SP2/O mouse myeloma cells were stably transfected with a construct encoding a λ6 LC (Wil) under control of the CMV promoter, while λ2-producing myeloma cell line RPMI 8226 was purchased from the ATCC. Both were treated with small interfering RNA (siRNA) directed specifically to the V, J, or C portions of the molecules and then analyzed by ELISA, flow cytometry and real time PCR. Results Transfected cells were found to constitutively express detectable quantities of mRNA and protein Wil and, after exposure to siRNAs, an ~40% reduction in mRNA and LC production was evidenced at 48 hours. An even greater effect was seen with the 8226 cells. Conclusion Our results have shown that RNAi can markedly reduce LC synthesis and provide the basis for testing the therapeutic potential of this strategy using in vivo experimental models of multiple myeloma.

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Initial studies of the Odontogenic Ameloblast-Associated Protein (ODAM) revealed that it is highly expressed in mature ameloblasts and is present in the rodent enamel organ and junctional epithelium. Further analysis showed that ODAM is expressed in several epithelial malignancies including gastric, colon, breast, lung and melanoma. A correlation was observed between ODAM expression/localization and breast cancer stage/clinical patient outcome, indicating that ODAM may serve as a novel prognostic biomarker in this type of cancer. When transfected with rODAM and injected into mice intravenously, the MDA-MB-231 breast cancer cell line showed marked inhibition of neoplastic and metastatic properties. This suggests that ODAM has a potentially significant regulatory role in tumorigenesis and metastasis of breast cancer with important clinical implications. To investigate the role of ODAM in melanoma, archived slides prepared from primary melanoma tissue specimens were obtained and stained with anti-ODAM antibodies and results were compared with retrospective clinical data. In patients that were found to have positive sentinel lymph nodes, ODAM localized to the nucleus in 76% of the cases. This suggests that nuclear-localization of ODAM in the primary tumor is a negative prognostic factor, which could assist in determining management of this devastating cancer. Melanoma is frequently diagnosed at late stages, often metastatic to regional lymph nodes or distant sites. The inhibition of neoplastic and metastatic properties shown in ODAM-expressing breast malignancies encouraged further investigation into the effect of ODAM expression in the tumorigenesis of melanoma. The human metastatic melanoma cell line C8161 does not express ODAM and was stably transfected with rODAM. In two consecutive growth assays, the ODAM-expressing C8161-clones showed significant growth inhibition compared to parent C8161 cells. In wound-healing assays of cell migration, exogenous rODAM was added at increasingly higher concentrations to wells of C8161 cells at 100% confluency immediately before scratch-wounding the monolayer. After twenty-four hours, C8161 parent cells had near-complete coverage of the scratch defect. In the wells with added exogenous rODAM, cells showed a decreased ability to migrate and cover the scratch, with more inhibition of migration as the concentration of rODAM increased from 3 to 12 µg/mL. These findings demonstrate that ODAM alters the behavior of the C8161 human melanoma cell line with respect to growth and cell migration. Further studies to assess tumorigenesis in vivo are under way, concerning the potential effect that ODAM may have on invasion, gene expression and metastatic characteristics of this cell line. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4302. doi:1538-7445.AM2012-4302