Thesis (Ph.D.)--University of Alabama at Birmingham, 2009. / Title from PDF title page (viewed on Feb. 10, 2010). Includes bibliographical references.

published_or_final_version / Surgery / Master / Master of Philosophy

published_or_final_version / Surgery / Master / Master of Philosophy

Esophageal squamous cell carcinoma (ESCC) is the predominant type of esophageal cancer in Asia. Cisplatin is commonly used as an agent for treating ESCC patients undergoing chemotherapy. However establishment of resistance over the course of treatment diminishes the clinical usefulness and is one reason explaining poor prognosis of ESCC patients. In order to gain insights into the mechanism of cisplatin resistance in ESCC, HPLC/nESI-MS/MS proteomic profiling was employed to examine the global protein alterations of cisplatin-resistant ESCC cell line HKESC2/CDDP comparing with its parental cisplatin-sensitive cell line HKESC2. Stable over-expression and knocked-down cell lines were established for pathway analysis and functional studies. Seventeen proteins were identified with more than 2-fold difference in expression levels. These proteins are involved in endoplasmic reticulum stress response, metabolic processes, DNA replication and repair, nucleotide binding and cell cycle control, while some of them are components of cytoskeletal proteins. Among them, 14-3-3σ was one of the most significantly upregulated proteins found in HKESC2/CDDP cells and its differential expression levels were validated using western blotting and real-time quantitative polymerase chain reaction. Pathway analysis revealed that ectopic overexpression of 14-3-3σ caused a general upregulation in DNA repairing genes. Furthermore, functional validation showed that elevated 14-3-3σ expression contributed considerably to the observed cisplatin resistance in HKESC2/CDDP cells. While knocking down 14-3-3σ expression reversed the above situations in SLMT1 cells. I conclude that up-regulation in 14-3-3σ, together with DNA repairing genes, contributes to the establishment of cisplatin resistance in HKESC2/CDDP cells. Knocking down 14-3-3σ expression sensitized ESCC cells to cisplatin treatment, and hence, opens a therapeutic opportunity for ESCC cisplatin resistance. / published_or_final_version / Surgery / Doctoral / Doctor of Philosophy

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Squamous cell carcinoma of the oesophagus (OSCC) is a common malignancy that occurs with high frequency in certain parts of the world, including South Africa. The aetiology of OSCC has remained unclear although many studies suggest that it is caused by a combination of variable risk factors. Recent reports implicate a variety of genetic factors in the carcinogenesis of OSCC but their involvement is yet to be defined. / Thesis (M.Med)-University of KwaZulu-Natal, Durban, 2010.

The Tumour-Node-Metastasis (TNM) classification system of tumour stage does not always reflect the actual tumour mass present at diagnosis. Recent reports propose that volumetric analysis may allow improved stratification of disease recurrence and survival in head and neck squamous cell cancer (SCC). This study aims to assess the prognostic value of tumour volume on the outcome of patients with oral cavity and oropharyngeal SCC. / A retrospective review of 73 patients was completed. Tumours were outlined semi-automatically in digitized computed tomography scans, and volumes computed based on surface triangulations of three-dimensional reconstructions with novel software developed at McGill. / Results illustrate significant interstage variability within the current TNM model. Moreover, in oral cavity and oropharyngeal SCC, tumour volume as well as T-stage are significant and independent predictors of disease free survival and overall survival.

p63(alpha) belongs to the p53-family of proteins and has full-length (TA) as well as truncated ((delta)N) p63(alpha) isoforms. Previous studies have shown that TA and (delta)Np63(alpha) play multiple roles in cancer and development. In cancer, (delta)Np63(alpha)-mediated transcriptional repression promotes oncogenesis while transactivation by TAp63(alpha) is critical during development. Despite their importance, little is known regarding how TA or (delta)Np63(alpha) is regulated and factors influencing the function of p63(alpha) have yet to be identified. Here, I identify Special AT-rich Binding Protein 2 (SATB2) as a protein that forms a complex with and modulates the function of p63(alpha). SATB2 is detected in multiple head and neck squamous cell carcinoma (HNSCC) cell lines that also show overexpression of (delta)Np63(alpha). Histological analysis on tumor specimens revealed that SATB2 is predominantly expressed in advanced-stage HNSCC cancers. SATB2 increases DNA-binding capabilities of (delta)Np63(alpha), augmenting (delta)Np63(alpha) repression of apoptotic gene expression. Knockdown of SATB2 in HNSCC cells sensitizes cancer cells towards chemotherapy- and radiation-induced apoptosis. These results indicate that SATB2 functions as a co-factor and promotes the transrepression function of (delta)Np63(alpha) in HNSCC. In addition to examining the role of SATB2 in HNSCC, I also investigated the effect of SATB2 on the ability of TAp63(alpha) to induce gene expression. In particular, perp has been shown to be a critical downstream target of p63 during development. ChIP analysis revealed that while SATB2 increases TAp63(alpha)-binding to apoptotic gene promoters, SATB2 decreases TAp63(alpha) localization on the perp promoter and inhibits p63(alpha)-mediated perp induction. SATB2 more readily interacts with human disease-associated p63(alpha) mutations that are found in the SAM domain, further inhibiting transcriptional properties of these mutants. Together, my results suggest that SATB2 is an important modulator of p63(alpha) in cancer and development.

p63(alpha) belongs to the p53-family of proteins and has full-length (TA) as well as truncated ((delta)N) p63(alpha) isoforms. Previous studies have shown that TA and (delta)Np63(alpha) play multiple roles in cancer and development. In cancer, (delta)Np63(alpha)-mediated transcriptional repression promotes oncogenesis while transactivation by TAp63(alpha) is critical during development. Despite their importance, little is known regarding how TA or (delta)Np63(alpha) is regulated and factors influencing the function of p63(alpha) have yet to be identified. Here, I identify Special AT-rich Binding Protein 2 (SATB2) as a protein that forms a complex with and modulates the function of p63(alpha). SATB2 is detected in multiple head and neck squamous cell carcinoma (HNSCC) cell lines that also show overexpression of (delta)Np63(alpha). Histological analysis on tumor specimens revealed that SATB2 is predominantly expressed in advanced-stage HNSCC cancers. SATB2 increases DNA-binding capabilities of (delta)Np63(alpha), augmenting (delta)Np63(alpha) repression of apoptotic gene expression. Knockdown of SATB2 in HNSCC cells sensitizes cancer cells towards chemotherapy- and radiation-induced apoptosis. These results indicate that SATB2 functions as a co-factor and promotes the transrepression function of (delta)Np63(alpha) in HNSCC. In addition to examining the role of SATB2 in HNSCC, I also investigated the effect of SATB2 on the ability of TAp63(alpha) to induce gene expression. In particular, perp has been shown to be a critical downstream target of p63 during development. ChIP analysis revealed that while SATB2 increases TAp63(alpha)-binding to apoptotic gene promoters, SATB2 decreases TAp63(alpha) localization on the perp promoter and inhibits p63(alpha)-mediated perp induction. SATB2 more readily interacts with human disease-associated p63(alpha) mutations that are found in the SAM domain, further inhibiting transcriptional properties of these mutants. Together, my results suggest that SATB2 is an important modulator of p63(alpha) in cancer and development.

The ErbB family of receptors are key regulators of growth, differentiation, migration and survival of epithelial cells. CI-1033 is an irreversible pan-ErbB tyrosine kinase inhibitor that has the ability to inhibit EGFR function but has shown limited therapeutic efficacy. Lovastatin targets the activity of HMG-CoA reductase, the rate-limiting step in the mevalonate pathway. In this study, the ability of lovastatin to potentiate the cytotoxic effects of CI-1033 was evaluated. The combination of lovastatin and CI-1033 exhibited some cooperative cytotoxic activity in a squamous cell carcinoma–derived cell line. This combination resulted in enhanced cell death by induction of a potent apoptotic response. Furthermore, this drug combination inhibited EGF-induced EGFR autophosphorylation and activation of the downstream signaling effectors, ERK and AKT. These findings suggest that combining lovastatin and tyrosine kinase inhibitors may represent a novel combinational therapeutic approach in squamous cell carcinoma of the head and neck.