Uveal Melanoma (UM) is the most common malignant intra-ocular tumor in adults. Despite the high accuracy of clinical diagnosis and advances in local treatment, more than 50% of UM patients develop metastasis within ten years of initial diagnosis. NM23 is a human metastasis suppressor gene. Reduced Nm23-H1 expression is correlated with high metastatic potential in a variety of different cancers including melanoma. C-Met is a receptor tyrosine kinase (RTK) that has been known to stimulate the invasive growth and increase the metastatic potential of cancer cells. Expression of c-Met is correlated with high mortality rate in UM patients. Treatment with CQX-2 inhibitors showed promise as an adjuvant therapy in adenocarcinoma of the colon. A previous report from our laboratory showed that topical treatment with Nepafenac (a CQX-2 inhibitor) delayed the progression of the primary tumor and the formation of metastasis in the experimental rabbit model of UM. / The purpose of this thesis is to investigate the expression levels ofNm23-H1 in UM cell lines with different metastatic potentials, in paraffin embedded tissues from primary tumors of UM patients, and in an experimental rabbit model. In addition, the aim of this thesis is to determine whether treating human uveal melanoma cell lines with Nepafenac would increase the expression levels of Nm23-H1 and decrease the expression levels of c-Met in vitro (UM cell lines) and in vivo (experimental rabbit model). / To achieve our goal, we used several types of assays in our UM cell lines and paraffin embedded tissues from patient samples and experimental rabbit model, including quantitative immunostaining, quantitative Real-time PCR, and small interference RNA (siRNA). / The Real-time PCR results of five human uveal melanoma cell lines showed that expression of Nm23-HI is higher in cell lines with low metastatic potential compared to those with high metastatic potential. The invasive ability of the uveal melanoma cell lines increased after silencing Nm23-H1 expression with siRNA. The increased immunostaining intensity of Nm23-H1 in patient samples is associated with better survival rate. Moreover, treatment with Nepafenac resulted in increase of Nm23-H1 levels and decrease of c-Met levels in both the UM cell lines and the experimental rabbit model. / In conclusion, Nm23-H1 is a potent prognostic marker to predict the survival rate of UM patients and it has the potential to identify high-risk patients. To the best of our knowledge, this is the first study to show that treatment with COX-2 inhibitor causes an upregulation of Nm23-H1 and downregulation of c-Met in UM. Therefore, treatment with COX-2 inhibitors may be a useful strategy as an adjuvant therapy for UM patients.

Colorectal tumors with mutations on Wnt family members show an overexpression of several Notch target genes, suggesting a link between Wnt and Notch signaling pathways. In this work, we have demonstrated that there is a direct relation between Wnt and Notch pathways that it is responsible for the maintenance of the intestinal proliferative compartment and crucial for intestinal tumorigenesis. We have identified two different mechanisms through β-catenin interacts with Notch to activate transcription: 1) β-catenin activates Notch through the transcriptional activation of Notch ligand Jagged1. Jagged1 expression leads the binding to the Notch receptor, promoting its cleavage and activation. This mechanism occurs in human colorectal tumors, with nuclear β-catenin, overexpressed Jagged1 and activated Notch. 2) β-catenin and Notch bind simultaneously to a specific group of gene promoters. We observed that this group of genes is overexpressed in tumours with mutations in Wnt signaling. Moreover, β-catenin and Notch physically interact in the nucleus of colorectal tumour cell lines. We have characterized a group of genes that are double target genes for β-catenin and Notch; in other words, these genes require the activation of both Wnt and Notch signaling pathways. These genes are expressed in the intestinal undifferentiated compartment. The loss of any of these signalling pathways reduced stem cell marker expression, reinforcing the importance of the interaction between both signalling pathways. The study of conditional knockouts mice for Jagged1 indicated that Jagged1 is not required for maintaining the intestinal homeostasis. However, Jagged1 is crucial during the tumorigenic process. Our data opens a new possibility for colorectal treatment, using inhibitors of Notch ligand Jagged1, avoiding side effects in the intestinal normal tissue.

Diss. (sammanfattning) Stockholm : Karol. inst., 2005. / Härtill 5 uppsatser.

Diss. (sammanfattning) Stockholm : Karolinska institutet, 2002. / Härtill 5 uppsatser.

Diss. (sammanfattning) Stockholm : Karol. inst., 2004. / Härtill 4 uppsatser.

Diss. (sammanfattning) Stockholm : Karol. inst., 2004. / Härtill 4 uppsatser.

Diss. (sammanfattning) Stockholm : Karol. inst., 2003. / Härtill 5 uppsatser.

Diss. (sammanfattning) Stockholm : Karol. inst., 2003. / Härtill 6 uppsatser.

Diss. (sammanfattning) Stockholm : Karol. inst., 2005. / Härtill 4 uppsatser.

Diss. (sammanfattning) Stockholm : Karol. inst., 2005. / Härtill 6 uppsatser.