Oral squamous cell carcinoma (OSCC) is now the forth leading cause of male cancer mortality in Taiwan. The betel quid (BQ) chewing is the main cause OSCC in Taiwan. This study was aimed to clone the CDK2-associated protein 1 (CDK2AP1) complete CDs and characterization of its expression profiles as well as protein sublocalization in oral cancers. The human CDK2AP1 gene is 1.6 Kbp in length, mapped to 12q24.31 and encodes for a 12.4 kDa polypeptide. Human CDK2AP1 protein interacts with DNA polymerase alpha/primase resulting in negative regulation of the rate of initiation of DNA replication. It has been reported that differential CDK2AP1 expression, with decreased or absent expression in microsatellite-unstable (MSI+) colorectal cancer (CRC) cell lines, suggesting that loss of CDK2AP1 protein expression is a characteristic of malignant transformation in MSI+CRC. The role of CDK2AP1 in the onset or progression of oral cancer is still unknown. In this study, we firstly extracted RNA from 45 patients¡¦ specimens. Then, we cloned CDK2AP1 CDs from stomach carcinoma cell line (Scm1) and subcloned into various protein expression vectors for further examining CDK2AP1 subcellular localization in HeLa cell. Polyclonal CDK2AP1 antibody was prepared. We have demonstrated that the CDK2AP1 protein locates in both cytoplasm and nucleus by immunofluorescence analysis. In addition, we examined the CDK2AP1 mRNA expression profiles in oral cancer specimens by quantitative RT-PCR. The results showed that the expression of CDK2AP1 mRNA in oral cancer tissues were higher than those in normal oral tissues. Furthermore, we have determined and compared the CDK2AP1 protein in both oral cancer and normal tissues by immunoblotting analysis and immunohistochemical (IHC) analysis. The results from both immunoblotting and IHC were consistent with the results from quantitative RT-PCR. CDK2AP1 protein expression was higher in oral cancer tissues than in normal oral tissues.

Oral cancer is now the fourth leading cause of male cancer mortality in Taiwan. Betel quid chewing is one of the main causes of oral cancer in Taiwan. CDK2AP1 is a growth suppressor gene that negatively regulates cyclin-dependent kinase 2 (CDK2) activities. Expression of p12CDK2AP1 protein is reduced and/or lost in oral cancers. Mutations in microsatellite-like sequence of CDK2AP1 gene in microsatellite instability colorectal cancer are associated with down-regulated CDK2AP1 transcription. This mutation was due to down-regulation of one DNA repair protein, MLH1. In order to understand whether CDK2AP1 mRNA and protein expression levels associate with betel-chewing oral cancers, we firstly analyzed 44 oral cancer specimens (normal and tumor, in pairs) by quantitative reverse transcription polymerase chain reaction and Western blotting. Immunohistochemistry was used to examine p12CDK2AP1 protein expression in another 167 buccal mucosa squamous cell carcinoma tissues. We have demonstrated that the expression levels of CDK2AP1 mRNAs were slightly higher in normal oral tissues than those in tumor tissues (P>0.05). Similarly, p12CDK2AP1 and CDK2 protein expression levels were up-regulated in oral cancer tissues than in normal tissues by Western blot analysis (P<0.05). Among Ca9-22, CAL27, SAS and in betel-chewing oral cancer cells TW2.6 and human normal skin keratinolial cells (HaCaT) that we examined, p12CDK2AP1 and CDK2 proteins were detected to be highest expressed in Ca9-22 and TW2.6 cells, respectively, when compared to HaCaT cells. Immunocytochemistry indicated p12CDK2AP1 expressed in nucleus and cytoplasm in Ca9-22, CAL27, SAS and HaCaT cells, however predominant present in nucleus in TW2.6 cells. On the other hand, immunohistochemistry demonstrated that nuclear (P=0.157) and cytoplasmic p12CDK2AP1 (P=0.350) in 167 patients with buccal mucosa squamous cell carcinoma were slightly down-regulated. Reduction of nuclear p12CDK2AP1 was not significantly correlated with any clinicopathologic characteristics or prognosis. Direct sequencing indicated that lack of microsatellite-like instability of CDK2AP1 3¡¦-UTR in four oral cancer cell lines, HaCaT and six patients with down-regulated MLH1 protein. In conclusion, we demonstrated that: (1) p12CDK2AP1 was located in both the nucleus and cytoplasm in most oral cancer cell lines and HaCaT cells but predominate present in the nucleus in betel-chewing oral cancer cells, TW2.6; (2) Reduction of nuclear p12CDK2AP1 in buccal mucosa squamous cell carcinoma tissues were identified, however, not significantly correlated with any clinicopathologic characteristics, prognosis or betel chewing; (3) In six patients with down-regulated MLH1, lack of micorsatellite-like instability in the CDK2AP1 3¡¦-UTR region has been found.

Bladder cancer is a common malignancy affecting the genitourinary system. Although a large number of studies have been carried out on these areas for a long time, little is know about the molecular events which may involve in tumorigenesis. Until now, no profound immunohistological or molecular markers have been identified to define clinically relevant subsets of bladder cancer. The purpose of this thesis is to identify a novel bladder cancer carcinogenesis related genes. Chapter 1 attempts to illustrate the background, molecular markers, chromosomal abnormalities and genetic instability related to bladder cancer. In Chapter 2, various bioinformatics methodologies were used to annotate and identify candidate genes. Twenty-one genes were identified 1.5-fold up- or down-regulated in mRNA expression from RT4, TSGH8301 and J82, three different stages of bladder cancer cell lines by microarray chips (Dr. Liu, personal communications). Another eight candidate tumor suppressor genes were preliminarily identified from suppression subtractive hybridization (SSH) cDNA library of RT4 cell line based on an isoflavones-treated minus non-treated and further subjected to quantitative RT-PCR analyses to confirm the mRNA expression level in different stages of bladder cancer cell lines. Chapter 3 studies on the ANXA10 gene with special emphasis on its cloning, protein expression, subcellular localization and the preparation of polyclonal antibody. The result suggests that ANXA10 is a cytoplasmic protein in N18 cells. Chapter 4 analyzes the CDK2AP1 gene in mRNA and protein level at different bladder cancer cell lines and various specimens. In our preliminary observations, there are lost of CDK2AP1 expressions at invasive TCCs specimens when compared to noninvasive TCCs specimens. The mechanism of the tumor-associated loss of the CDK2AP1 expression is currently not clear. In Chapter 5, bladder cancer cell lines TSGH8301, UB37, TCCSUP and J82 in SCID mice xenograft model were established for further in vivo studies.

Cyclin Dependent Kinase-2 Associated Protein-1 (CDK2AP1) plays an important role in cell cycle regulation, by inhibiting CDK2 and by targeting it for proteolysis. It is also known to bind the DNA polymerase alpha-primase complex and regulate the initiation step of DNA synthesis. Its overexpression has been shown to inhibit growth, reduce invasion and increase apoptosis in a number of cancer cell lines. In studies in which mouse embryonic stem cells (mESCs) with targeted deletion of the Cdk2ap1 gene were used, Cdk2ap1 was shown to be required for epigenetic silencing of Oct4 during differentiation. The goal of this thesis was to examine the role of CDK2AP1 in somatic cells (primary human dermal fibroblasts (HDFs)) and human embryonic stem cells (hESCs) and specifically assess its impact on proliferation, self-renewal and differentiation. In the first part of this study, using a short-hairpin RNA (shRNA) approach, we investigated the effect of CDK2AP1 downregulation in HDFs. Outcomes indicated: (a) reduced proliferation, (b) premature senescence, (c) cell cycle alterations, (d) DNA damage, and (e) an increase in p53, p21, and the p53-responsive apoptotic genes BAX and PUMA. Simultaneous downregulation of p53 and CDK2AP1 in HDFs confirmed that observed phenotype was p53 dependent. In the second part of this study, using a shRNA approach, we investigated the role of CDK2AP1 on hESC fate associated with self-renewal and differentiation. We found that CDK2AP1 knockdown in hESCs resulted in: (a) reduced self-renewal (b) enhanced differentiation (c) cell cycle alterations and (d) increase in p53 expression. Results indicate that the knockdown of CDK2AP1 in hESCs enhances differentiation and favors it over a self-renewal fate. Thus, this study has successfully identified novel functions for CDK2AP1, as its knockdown has a significant impact on self-renewal, differentiation and senescence. Results obtained from this study could contribute to development of directed differentiation strategies for generating uniform populations of differentiated phenotypes from hESCs for clinical applications.