Major Histocompatibility Complex (MHC) Class I molecules present peptides to CD8⁺ T cells and are essential for most adaptive immune responses. The first described-spliced tapasin (“isoform 1”) plays a critical role in MHC-I antigen presentation by facilitating peptide loading onto MHC-I molecules in the endoplasmic reticulum (ER). This thesis examines the expression, localization and function of two novel, alternatively-spliced isoforms of human tapasin that lack exon 7 (“isoform 2”) or both exons 6 and 7 (“isoform 3”). Isoform 1 contains a di-lysine ER-retention motif; the two novel isoforms encode different carboxy (C) termini that lack this motif. It was hypothesized that isoforms 2 and 3 would function in MHC-I cross-presentation of exogenous antigens in non-ER compartments. Isoform 2, like isoform 1, was found to be mainly ER-localized; however, both these isoforms were also found to co-localize in smaller amounts with the trans Golgi network and endo/lysosomes by confocal microscopy. Isoform 3 lacks a transmembrane domain and was found to be secreted from cells as well as being found within the ER. All isoforms were widely expressed at the RNA level in many tissues and cell types; however, mature dendritic cells (DCs) expressed the highest levels of all three isoforms, consistent with the high cross-presenting abilities of DCs. Both isoform 1 and 2 stabilized the transporters associated with antigen processing (TAP) in murine tapasin-/- cells, but isoform 3 did not due to its missing transmembrane domain. Isoform 1 and 2 mediated very similar effects on endogenous MHC-I presentation of self and viral peptides, on surface MHC-I thermostability, and on MHC-I maturation rates. Isoform 3 was found to decrease loading of exogenous peptides onto MHC-I. None of the isoforms influenced cross-presentation of the soluble antigen ovalbumin in a mouse dendritic cell line. This thesis also examines the effect of antigen presentation machinery (APM) re-expression in MHC-I-deficient tumor cell lines, B16F10 and CMT.64, which are deficient in TAP and tapasin. Virally-driven TAP1 and Tapasin expression increased MHC-I expression in the tumor cell lines, augmented tumor cell immunogenicity, and decreased tumor growth in vivo due to increased tumor cell elimination by the immune system.

Cutaneous malignant melanoma is an aggressive form of skin cancer, characterized by strong chemoresistance and poor patient prognosis. The molecular mechanisms underlying its resistance to chemotherapy remain unclear but are speculated to involve dysregulation of apoptosis and reinforcement of survival signaling. In this work, we show that aberrant expression of two key proteins, PUMA and p-Akt, is associated with melanoma tumor progression and poor patient survival. We report that PUMA expression is reduced in melanoma tumors compared to dysplastic nevi, while p-Akt expression is elevated in melanoma tissue compared to dysplastic nevi. We propose a two-pronged therapeutic strategy of (1) boosting PUMA expression and (2) inhibiting Akt phosphorylation. We demonstrate that exogenous overexpression of PUMA, via adenoviral-mediated gene expression (ad-PUMA), forces melanoma cells to undergo rapid mitochondrial-mediated apoptosis in vitro. We also report that a small molecule Akt inhibitor, API-2, greatly inhibits melanoma cell growth in vitro. Using a SCID mouse melanoma xenograft model, we show that combination treatment of ad-PUMA and API-2 dramatically suppresses tumor growth in an additive manner, leading to over 80% growth inhibition compared to controls. We also investigate the role of NF-κB overexpression in melanoma. Our lab previously reported that expression of the p50 subunit of NF-κB, in particular, correlates with melanoma progression and poor patient survival. Here, we use cDNA microarray analysis to show that p50 overexpression upregulates IL-6 in melanoma cells. We further demonstrate that p50-mediated IL-6 expression stimulates the growth of endothelial cells in vitro and promotes angiogenesis in vivo. This work supports the hypothesis that melanoma cells exploit multiple mechanisms to sustain a survival advantage, including: 1) suppression of apoptosis (via PUMA down-regulation), 2) increased activation of survival pathways (via increased p-Akt), and 3) upregulation of pro-angiogenic factors (via p50-mediated IL-6 induction). This work suggests that the specific targeting of one or more key mediators of these processes may be an effective therapeutic strategy for treating malignant melanoma.

Dissertation under the direction of Professor Harold L. Moses Transforming Growth Factor Beta (TGF-β) is acts as both a tumor suppressor and promoter in the context of epithelial tumor progression. In epithelial cells, active TGF-β signaling promotes cell cycle arrest to slow tumor growth but also promotes EMT and cell motility to enhance tumor cell metastasis. We sought to address TGF-β signaling role in tumor progression through its effects on stromal cells and microenvironmental changes. Interestingly, as with epithelial TGF- β signaling, we found active TGF-β signaling in fibroblasts to present with the same dichotomous relationship. We found that TGF-β can promote fibroblast activation which in turn drives the expression of numerous matrix remodeling genes. The phenotypic outcome of this matrix remodeling promotes tumor cell metastasis. Alternatively, abrogation of TGF-β signaling in fibroblasts also promotes tumor cell metastasis. Albeit, this occurs through a different mechanism involving altered chemokine expression to promote chemotaxis of tumor promoting myeloid cells. Gene expression analysis of stroma from reduction mammoplasty as well as breast cancer patients suggests that TGFβR2 is lost as breast cancer progresses from normal mammary tissue to invasive ductal carcinoma. Importantly, this loss of TGFβR2 in the stroma of breast cancer patients is associated with poor patient outcome and rick of recurrence. This work shows the importance of TGF-β signaling as a central player in numerous biological process which effects tumor progression through the tumor microenvironment. As this signaling axis in the tumor microenvironment is certainly important in the progression of human breast cancer, the therapeutic targeting of the TGF-β pathway will need to consider stromal effects for efficacious use.

Depression is a serious problem affecting cancer patients. The current study examined depression screening and management behaviour at a tertiary care cancer centre. Ten oncologists and ten nurses took part in this study, and were interviewed. The interview covered clinician’s current depression screening and management practices, and the Theory of Planned Behaviour was applied to better understand screening behaviour. The Theory of Planned Behaviour was used in this study because it is useful in conceptualizing individual’s behaviour. Results indicated clinicians screened for depressed mood. Participants also reported managing depressed patients by indicating they referred patients to other clinicians. Finally, within the Theory of Planned Behaviour, subjective norms were related to past intention to screen for depression, and past intention to screen was related to past screening behaviour. In summary, this study found that depression is screened for, depression is managed appropriately in patients, and some components of the Theory of Planned Behaviour are useful in understanding screening behaviour.

Cancer is a growing health concern world-wide and is the second most common cause of death after heart diseases. Current treatment strategies such as surgery, chemotherapy and radiation provide some relief to cancer patients but the toxic side effects associated with chemotherapy and radiation often lead to further adverse health effects. Hence there is a need for drugs with better safety profile and improved efficacy. Cannabinoids are a group of compounds with several therapeutic properties and besides their appetite stimulant, anti-emetic and analgesic effects, cannabinoids can inhibit tumor growth, survival and metastasis. The mechanisms of action of cannabinoids as anticancer agents are highly complex and not completely understood. Studies from our laboratory indicate that the specificity protein (Sp) transcription factors, Sp1, Sp3 and Sp4 that belong to the Sp/KLF family of transcription factors are overexpressed in many tumors and regulate critical factors responsible for cancer cell proliferation, growth, angiogenesis and survival. Hence, we hypothesized that cannabinoids elicit their responses on cancer cells by downregulating the expression of Sp proteins and Sp-regulated gene products. Treatment of colon and prostate cancer cells with the cannabinoids WIN and cannabidiol (CBD) inhibited cancer cell proliferation, induced apoptosis and downregulated Sp proteins and Sp-dependent genes. Furthermore, we demonstrated that WIN and CBD-mediated induction of apoptosis and repression of Sp proteins were mediated by phosphatases and that the phosphatase involved in WIN- dependent downregulation of Sp proteins was protein phosphatase 2A (PP2a). In addition WIN induced expression of ZBTB-10, an Sp repressor and downregulated microRNA-27a (miR27a) and these effects were PP2a-dependent indicating that WIN transcriptionally represses Sp protein expression by activating the phosphatase, PP2a. We also investigated the effects of 1,1-bis(3'-indolyl)-1-(p-bromophenyl)methane (DIM-C-pPhBr) and the 2,2'-dimethyl analog (2,2'-diMeDIM-C-pPhBr), on survivin expression in colon and pancreatic cancer cells. Survivin is an anti-apoptotic protein associated with cancer cell survival and confers radiation-resistance in patients receiving radiotherapy. In addition radiation induces survivin, leading to radioresistance in tumors. In this study we demonstrated that DIM-C-pPhBr and 2,2'-diMeDIM-C-pPhBr inhibit cell proliferation and induce apoptosis in colon and pancreatic cancer cells and in combination with radiotherapy, these drugs suppress radioresistance by inhibiting radiation induced survivin.

Phosphorylation of substrates by kinase proteins is one of the most prominent mechanisms by which signal transduction occurs and dysregulation of this activity is implicated as a major underlying cause of a number of diseases including cancer. Much of the current work focuses on developing inhibitors for various kinases in an effort to restore normal function in pathways where this deregulation occurs. However the vast majority of kinases remain uncharacterized and the roles they play in many of these signaling pathways are still unclear. This study examines the role of the non-receptor tyrosine kinase Fer in two malignant cells lines, MDA-MB-231 (breast cancer) and PC3 (prostate cancer). Using a lentiviral based RNA interference approach, the level of Fer was reduced to 6% in MDA-MB-231 and 10% in PC3 cells relative to WT levels. Fer knockdown correlated with enhanced migration in MDA-MB-231 cells, but impaired migration in PC3 cells, suggesting opposing roles for Fer in regulating migration in each cell type. Fer knockdown correlated with enhanced proliferation in MDA-MB-231 cells, but was slightly reduced in the PC3 cells, again suggesting opposing roles for Fer in regulating proliferation between these two cell lines. In Fer knockdown PC3 cells, N-cadherin expression was increased, while E-cadherin levels were decreased; and in a fraction of cells E-cadherin relocalized from a predominantly intracellular vesicular compartment to a plasma membrane localization. In xenografting experiments, Fer knockdown MDA-MB-231 cells showed reduced tumor growth rates compared with tumors established with WT cells, suggesting that Fer may influence tumorgenesis on a tumor cell intrinsic basis. Separate xenografting studies showed that MDA-MB-231 derived tumors grew slower in fer-knockout compared to fer-wild type nude mice. This trend failed to show any statistical significance however it may still suggest an additional tumor promoting role for Fer in the stroma. / Thesis (Master, Pathology & Molecular Medicine) -- Queen's University, 2009-09-17 22:23:35.451

No description available.

<p>The aim of the study is to compare the palliative efficacy of two saliva substitutes (Sinspeek and Xerostom) in patients during radiotherapy for cancer of the head and neck. This crossover randomised controlled clinical trial was carried out on twenty-five patients with malignant tumours of the head and neck, following four weeks of radiotherapy at tygerberg hospital. The benefit of saliva substitutes to ameliorate the effects of xerostomia is well established and proper advice and access to relevant preparations is essential.</p>

Inactivation of STK11/LKB1 is one of the most common genetic events in lung cancer, and understanding the cellular phenotypes and molecular pathways altered as a consequence will aid the development of therapeutic strategies targeting LKB1-deficient cancers. We report the comprehensive analysis of gene and protein expression patterns associated with LKB1 loss in lung adenocarcinomas, through which we identify hallmarks of altered tumor metabolism and downregulation of the PI3K/AKT pathway. Significant differences are observed between human tumors and those derived from a genetically engineered mouse model of LKB1 loss. A 16-gene signature is predictive of both mutational and non-mutational LKB1 loss in human tumors. Cell lines expressing this signature show increased sensitivity to MEK inhibition, independent of mutations in RAS and RAF family members. Restoration of LKB1 in lung cancer cell lines downregulates the gene expression pattern, attenuates FOXO3, and induces resistance to MEK inhibition. These findings identify characteristic phenotypic features of LKB1-deficient tumors and identify LKB1 loss as a novel determinant of MEK sensitivity.

No description available.