Notoriously resistant malignant melanoma is one of the most increasing forms of cancer worldwide; there is thus a precarious need for new treatment options. The Wee1 kinase is a major regulator of the G2/M checkpoint, and halts the cell cycle by adding a negative phosphorylation on CDK1 (Tyr15). Additionally, Wee1 has a function in safeguarding the genome integrity during DNA synthesis. To assess the role of Wee1 in development and progression of malignant melanoma we examined its expression in a panel of paraffin-embedded patient derived tissue of benign nevi and primary- and metastatic melanomas, as well as in agarose-embedded cultured melanocytes. We found that Wee1 expression increased in the direction of malignancy, and showed a strong, positive correlation with known biomarkers involved in cell cycle regulation: Cyclin A (p<0.0001), Ki67 (p<0.0001), Cyclin D3 (p = 0.001), p21Cip1/WAF1 (p = 0.003), p53 (p = 0.025). Furthermore, high Wee1 expression was associated with thicker primary tumors (p = 0.001), ulceration (p = 0.005) and poor disease-free survival (p = 0.008). Transfections using siWee1 in metastatic melanoma cell lines; WM239WTp53, WM45.1MUTp53 and LOXWTp53, further support our hypothesis of a tumor promoting role of Wee1 in melanomas. Whereas no effect was observed in LOX cells, transfection with siWee1 led to accumulation of cells in G1/S and S phase of the cell cycle in WM239 and WM45.1 cells, respectively. Both latter cell lines displayed DNA damage and induction of apoptosis, in the absence of Wee1, indicating that the effect of silencing Wee1 may not be solely dependent of the p53 status of the cells. Together these results reveal the importance of Wee1 as a prognostic biomarker in melanomas, and indicate a potential role for targeted therapy, alone or in combination with other agents.

TNXB was previously identified as a gene that is more highly expressed in malignant mesothelioma compared to ovarian/peritoneal serous carcinoma based on gene expression array analysis. The objective of the present study was to validate this finding at the mRNA and protein level. Effusions (n=91; 71 ovarian carcinomas, 10 breast carcinomas, 10 malignant mesotheliomas) were assayed for TNXB mRNA expression using quantitative PCR. Tenascin-X protein expression was studied in 183 effusions (137 carcinomas of different origin, 37 mesotheliomas, 9 reactive effusions) and 178 solid lesions (122 ovarian/ peritoneal carcinomas, 56 mesotheliomas) using immunohistochemistry. Quantitative PCR analysis showed significantly higher TNXB mRNA level in mesotheliomas compared to ovarian and breast carcinomas (p<0.001). By immunohistochemistry, tenascin-X protein expression was significantly higher in malignant mesothelioma compared to metastatic carcinoma in effusions (34/37 vs. 31/137 positive cases; sensitivity = 92%, specificity = 77%; p<0.001). Reactive mesothelial cells had focal or no tenascin-X expression. Tenascin-X protein was detected 41/56 mesothelioma biopsy specimens, and was uniformly absent from all 122 ovarian carcinomas (sensitivity = 73%, specificity = 100%; p<0.001). Our data suggest that tenascin-X may be a new diagnostic marker of malignant mesothelioma in the differential diagnosis of cancers involving the serosal cavities, particularly in the differential diagnosis between this tumor and ovarian/peritoneal serous carcinoma.

BackgroundThe molecular mechanisms underlying melanoma tumor development and progression are still not completely understood. One of the new candidates that emerged from a recent gene expression profiling study is fatty acid-binding protein 7 (FABP7), involved in lipid metabolism, gene regulation, cell growth and differentiation.MethodsWe studied the functional role of FABP7 in human melanoma cell lines and using immunohistochemistry analyzed its expression pattern and clinical role in 11 nevi, 149 primary melanomas and 68 metastases.ResultsFABP7 mRNA and protein level is down-regulated following treatment of melanoma cell lines with a PKC activator (PMA) or MEK1 inhibitor (PD98059). Down-regulation of FABP7 using siRNA decreased cell proliferation and invasion but did not affect apoptosis. In clinical specimens, FABP7 was expressed in 91% of nevi, 71% of primary melanomas and 70% of metastases, with a cytoplasmic and/or nuclear localization. FABP7 expression was associated with tumor thickness in superficial spreading melanoma (P = 0.021). In addition, we observed a trend for an association between FABP7 expression and Ki-67 score (P = 0.070) and shorter relapse-free survival (P = 0.069) in this group of patients.ConclusionOur data suggest that FABP7 can be regulated by PKC and the MAPK/ERK1/2 pathway through independent mechanisms in melanoma cell lines. Furthermore, FABP7 is involved in cell proliferation and invasion in vitro, and may be associated with tumor progression in melanoma.

No abstract

No abstract