Made available in DSpace on 2014-06-11T19:31:10Z (GMT). No. of bitstreams: 0 Previous issue date: 2012-03-07Bitstream added on 2014-06-13T19:01:33Z : No. of bitstreams: 1 joao_cf_dr_jabo.pdf: 1122575 bytes, checksum: 9ae3af7c9b6ed043db7419a9794af8db (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / A mastectomia é o procedimento terapêutico mais frequentemente empregado para tratar tumores mamários de cadelas e o sucesso depende do estádio do tumor no momento da intervenção. Estudos em modelos animais mostram que as proteínas de choque térmico (HSP) têm a capacidade de induzir imunidade inata tumor-específica e resulta na regressão do tumor. Sendo assim, este estudo teve como objetivos avaliar a eficácia do imunomodulador DNA-HSP65+proteína-HSP65 no tratamento de cadelas com tumores mamários malignos, seu potencial imunoestimulatório e investigar o aparecimento de efeitos adversos. Fizeram parte do experimento 21 cadelas com tumores mamários malignos. Destas 13 foram tratadas com o imunoterápico e oito submetidas a mastectomia da cadeia mamaria afetada. As cadelas (n= 13) receberam até três aplicações do imunomodulador, via intratumoral, no tumor de maior volume, com intervalo médio de 15 dias. O potencial imunoestimulatório do imunomodulador foi investigado através da citometria de fluxo pela comparação do numero de células natural killer ativadas, células B e T, CD4 e CD8, monócitos, monócitos ativados, macrófagos e células dendríticas; da proliferação espontânea de células mononucleares e da produção de anticorpos anti-HSP65 pelo teste ELISA antes do tratamento e 15 dias após o termino do mesmo. Seis cadelas (46,1%) apresentaram regressão em pelo menos um dos tumores da cadeia mamária, e uma (7,7%) no tumor que recebeu a aplicação do imunoterápico. Quando se consideram todas as mamas acometidas por tumores (n= 40), nove (22,5%) apresentaram regressão tumoral, 19 (47,5%) progressão e 12 (30%) se mantiveram estáveis. Três cadelas vieram a óbito durante o experimento; uma mastectomizada e duas tratadas com o imunoterápico. O imunoterapico não... / Mastectomy is a therapeutic procedure most often used to treat breast tumors in bitches and success depends on the tumor stage at the time of intervention. Studies in animal models show that the heat shock proteins (HSP) have the ability to induce tumorspecific innate immunity and results in tumor regression. Thus, this study aimed to evaluate the efficacy of immunomodulatory DNA-HSP65 + HSP65 protein in the treatment of dogs with malignant mammary tumors, and investigate its potential immunostimulatory the appearance of adverse effects. The experiment consisted of 21 dogs with malignant mammary tumors Of these 13 were treated with immunotherapy undergo mastectomy and eight of the affected mammary chain. Female dogs (n = 13) received three applications of the immunomodulator, intratumoral, in the greater volume tumor, with a mean interval of 15 days between applications. The potential immunostimulatory was investigated by flow cytometry by comparing the number of activated natural killer cells, T and B cells, CD4 and CD8 lymphocytes, monocytes, activated monocytes, macrophages and dendritic cells, the proliferation of mononuclear cells and spontaneous production anti-HSP65 antibody by ELISA before treatment and 15 days after the end. Six dogs (46.1%) had regression at least in one tumor of the mammary chain, and one dog (7.7%) in the tumor that received intratumoral application. When you consider all breast tumors (n = 40), nine (22.5%) had tumor regression, 19 (47.5%) progression and 12 (30%) remained stable. Three dogs died during the experiment, one after mastectomy and two after immunotherapy. The immunotherapy did not cause significant systemic immune stimulation. There was an increase of anti- HSP65 after treatment and the proliferation of leukocytes, although... (Complete abstract click electronic access below)

Orientador: Mirela Tinucci Costa / Coorientador: Célio Lopes Silva / Banca: Joice Lara Maia Faria / Banca: Noeme Sousa Rocha / Banca: Hélio José Montassier / Banca: Rosemeri de Oliveira Vasconcelos / Resumo: A mastectomia é o procedimento terapêutico mais frequentemente empregado para tratar tumores mamários de cadelas e o sucesso depende do estádio do tumor no momento da intervenção. Estudos em modelos animais mostram que as proteínas de choque térmico (HSP) têm a capacidade de induzir imunidade inata tumor-específica e resulta na regressão do tumor. Sendo assim, este estudo teve como objetivos avaliar a eficácia do imunomodulador DNA-HSP65+proteína-HSP65 no tratamento de cadelas com tumores mamários malignos, seu potencial imunoestimulatório e investigar o aparecimento de efeitos adversos. Fizeram parte do experimento 21 cadelas com tumores mamários malignos. Destas 13 foram tratadas com o imunoterápico e oito submetidas a mastectomia da cadeia mamaria afetada. As cadelas (n= 13) receberam até três aplicações do imunomodulador, via intratumoral, no tumor de maior volume, com intervalo médio de 15 dias. O potencial imunoestimulatório do imunomodulador foi investigado através da citometria de fluxo pela comparação do numero de células natural killer ativadas, células B e T, CD4 e CD8, monócitos, monócitos ativados, macrófagos e células dendríticas; da proliferação espontânea de células mononucleares e da produção de anticorpos anti-HSP65 pelo teste ELISA antes do tratamento e 15 dias após o termino do mesmo. Seis cadelas (46,1%) apresentaram regressão em pelo menos um dos tumores da cadeia mamária, e uma (7,7%) no tumor que recebeu a aplicação do imunoterápico. Quando se consideram todas as mamas acometidas por tumores (n= 40), nove (22,5%) apresentaram regressão tumoral, 19 (47,5%) progressão e 12 (30%) se mantiveram estáveis. Três cadelas vieram a óbito durante o experimento; uma mastectomizada e duas tratadas com o imunoterápico. O imunoterapico não... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Mastectomy is a therapeutic procedure most often used to treat breast tumors in bitches and success depends on the tumor stage at the time of intervention. Studies in animal models show that the heat shock proteins (HSP) have the ability to induce tumorspecific innate immunity and results in tumor regression. Thus, this study aimed to evaluate the efficacy of immunomodulatory DNA-HSP65 + HSP65 protein in the treatment of dogs with malignant mammary tumors, and investigate its potential immunostimulatory the appearance of adverse effects. The experiment consisted of 21 dogs with malignant mammary tumors Of these 13 were treated with immunotherapy undergo mastectomy and eight of the affected mammary chain. Female dogs (n = 13) received three applications of the immunomodulator, intratumoral, in the greater volume tumor, with a mean interval of 15 days between applications. The potential immunostimulatory was investigated by flow cytometry by comparing the number of activated natural killer cells, T and B cells, CD4 and CD8 lymphocytes, monocytes, activated monocytes, macrophages and dendritic cells, the proliferation of mononuclear cells and spontaneous production anti-HSP65 antibody by ELISA before treatment and 15 days after the end. Six dogs (46.1%) had regression at least in one tumor of the mammary chain, and one dog (7.7%) in the tumor that received intratumoral application. When you consider all breast tumors (n = 40), nine (22.5%) had tumor regression, 19 (47.5%) progression and 12 (30%) remained stable. Three dogs died during the experiment, one after mastectomy and two after immunotherapy. The immunotherapy did not cause significant systemic immune stimulation. There was an increase of anti- HSP65 after treatment and the proliferation of leukocytes, although... (Complete abstract click electronic access below) / Doutor

DOCTOR OF PHILOSOPHY (2019) McMaster University, Hamilton, Ontario (Medical Sciences) TITLE: Serotonergic antagonists affect the activity of breast tumor initiating cells in human and mouse models of breast cancer. AUTHOR: William D. Gwynne, BSc SUPERVISOR: Dr. John A. Hassell NUMBER OF PAGES: XXI; 255 / Breast cancer is the most frequently diagnosed cancer and the leading cause of cancer-related death amongst women worldwide. The relatively unchanging breast cancer-associated mortality rate is in part due to the existence of rare tumor cells (breast tumor initiating cells; BTIC) that possess stem-like properties permitting them to survive therapy and initiate disease recurrence. Hence, identifying agents capable of eradicating these cells would be a favourable therapeutic strategy to improve the durability of breast cancer remissions. To achieve the latter objective our lab screened over 35,000 small molecules for their capacity to inhibit the viability of BTIC-enriched mouse tumor cells. Unexpectedly, several antagonists of the serotonin (5-hydroxytryptamine; 5-HT) transporter and select receptors were among the hit compounds identified in the screen. This thesis aims to establish a connection between serotonergic activity and BTIC. We accomplished the latter by assessing whether components of the 5-HT signaling system are expressed in mouse and human breast tumor cells and whether inhibition of their activity affects BTIC frequency using multiple orthogonal assays. Our data suggest that breast tumor cells of both mouse and human origin express the components necessary for 5-HT synthesis, activity and metabolism and that inhibition of these proteins with selective antagonists reduces the capacity of these cells to form tumorspheres. We demonstrate that highly selective antagonists of SERT and HTR5A target BTIC as established ex vivo cell transplantation assays. We also discovered that these agents synergize with chemotherapy in vivo to affect the growth of mouse breast tumor allografts and human breast tumor xenografts. To validate the molecular targets of these agents, we attempted to phenocopy their effects in functional assays by knocking out their respective genes using CRISPR-Cas9 technology. Collectively, this thesis contributes to an understanding of how 5-HT signaling affects BTIC and identifies serotonergic antagonists as novel anticancer agents. / Dissertation / Doctor of Philosophy (PhD) / Despite improvements in screening technologies and the development of targeted therapies breast cancer remains the second leading cause of cancer-related death among Canadian women. Whereas the current standard of care is effective at treating the majority of patients diagnosed with breast cancer, there remains a substantial proportion of patients that experience relapse after undergoing therapy. Recurrence is due in part to the existence of rare, stem-like tumor cells, termed breast tumor-initiating cells (BTIC) that are insensitive to existing anticancer agents. Hence, identifying drugs capable of targeting these cells is a desirable goal. To pursue the latter, our lab screened approximately 35,000 compounds for their capacity to affect the growth of BTIC-enriched tumor cell populations. Among the hit compounds were antagonists of the serotonin transporter and serotonin receptors, including FDA-approved psychiatric medications. Here, we explore a connection between serotonin-related proteins and BTIC activity with the aim of identifying novel therapeutic agents.

<p>Microwave imaging is an efficient diagnostic modality for non-invasively visualizing dielectric contrasts of non-metallic bodies. An increasing interest of this field has been observed during the last decades. Many application areas in biomedicine have been issued, recently the breast tumor detection application using microwave imaging.</p><p>Many groups are working in the field at the moment for several reasons. Breast cancer is a major health problem globally for women, while it is the second most common cancer form for women causing 0.3 % of the yearly female death in Sweden. Medical imaging is considered as the most effective way of diagnostic breast tumors, where X-ray mammography is the dominating technique. However, this imaging modality still suffers from some limitations. Many women, mostly young ones, have radiographically dense breasts, which means that the breast tissues containing high rates of fibroglandular tissues. In this case the density is very similar to the breast tumor and the diagnosis is very difficult. In this case alternative modalities like Magnetic Resonance Imaging (MRI) with contrast enhancement and Ultrasound imaging are used, however those are not suitable for large scale screening program.Another limitation is the false-negative and false-positive rate using mammography, in general 5–15 % of the tumors are not detected and many cases have to go though a breast biopsy to verify a tumor diagnosis. At last the mammography using breast compression sometimes painful, and utilizing ionizing X-rays. The big potential in microwave imaging is the reported high contrast of complex permittivity between fibroglandular tissues and tumor tissues in breasts and that it is a non-ionizing method which probably will be rather inexpensive.</p><p>The goal with this work is to develop a microwave imaging system able to reconstruct quantitative images of a female breast. In the frame of this goal this Licentiate thesis contains a brief review of the ongoing research in the field of microwave imaging of biological tissues, with the major focus on the breast tumor application. Both imaging algorithms and experimental setups are included. A feasibility study is performed to analyze what response levels could be expected, in signal properties, in a breast tumor detection application. Also, the usability of a 3D microwave propagation simulator, (QW3D), in the setup development is investigated. This is done by using a simple antenna setup with a breast phantom with different tumor positions. From those results it is clear that strong responses are obtained by a tumor presence and the diffracted responses gives strong information about inhomogeneities inside the breast. The second part of this Licentiate thesis is done in collaboration between Mälardalen University and Supélec. Using the existing planar 2.45 GHz microwave camera and the iterative non-linear Newton Kantorovich code, developed at Département de Recherches en Electromagnétisme (DRE) at Supélec, as a starting point, a new platform for both real-time qualitative imaging and quantitative images of inhomogeneous objects are investigated. The focusing is related to breast tumor detection. For the moment the tomographic performance of the planar camera is verified in simulations through a comparison with other setups. Good calibration is observed, but still experimental work concerning phantom development etc. is needed before experimental results on breast tumor detection may be obtained.</p>

Microwave imaging is an efficient diagnostic modality for non-invasively visualizing dielectric contrasts of non-metallic bodies. An increasing interest of this field has been observed during the last decades. Many application areas in biomedicine have been issued, recently the breast tumor detection application using microwave imaging. Many groups are working in the field at the moment for several reasons. Breast cancer is a major health problem globally for women, while it is the second most common cancer form for women causing 0.3 % of the yearly female death in Sweden. Medical imaging is considered as the most effective way of diagnostic breast tumors, where X-ray mammography is the dominating technique. However, this imaging modality still suffers from some limitations. Many women, mostly young ones, have radiographically dense breasts, which means that the breast tissues containing high rates of fibroglandular tissues. In this case the density is very similar to the breast tumor and the diagnosis is very difficult. In this case alternative modalities like Magnetic Resonance Imaging (MRI) with contrast enhancement and Ultrasound imaging are used, however those are not suitable for large scale screening program.Another limitation is the false-negative and false-positive rate using mammography, in general 5–15 % of the tumors are not detected and many cases have to go though a breast biopsy to verify a tumor diagnosis. At last the mammography using breast compression sometimes painful, and utilizing ionizing X-rays. The big potential in microwave imaging is the reported high contrast of complex permittivity between fibroglandular tissues and tumor tissues in breasts and that it is a non-ionizing method which probably will be rather inexpensive. The goal with this work is to develop a microwave imaging system able to reconstruct quantitative images of a female breast. In the frame of this goal this Licentiate thesis contains a brief review of the ongoing research in the field of microwave imaging of biological tissues, with the major focus on the breast tumor application. Both imaging algorithms and experimental setups are included. A feasibility study is performed to analyze what response levels could be expected, in signal properties, in a breast tumor detection application. Also, the usability of a 3D microwave propagation simulator, (QW3D), in the setup development is investigated. This is done by using a simple antenna setup with a breast phantom with different tumor positions. From those results it is clear that strong responses are obtained by a tumor presence and the diffracted responses gives strong information about inhomogeneities inside the breast. The second part of this Licentiate thesis is done in collaboration between Mälardalen University and Supélec. Using the existing planar 2.45 GHz microwave camera and the iterative non-linear Newton Kantorovich code, developed at Département de Recherches en Electromagnétisme (DRE) at Supélec, as a starting point, a new platform for both real-time qualitative imaging and quantitative images of inhomogeneous objects are investigated. The focusing is related to breast tumor detection. For the moment the tomographic performance of the planar camera is verified in simulations through a comparison with other setups. Good calibration is observed, but still experimental work concerning phantom development etc. is needed before experimental results on breast tumor detection may be obtained.

Breast cancer is the most common cancer in female population worldwide. In addition to mutations, the breast tumor microenvironment especially the tumor cell - stroma interactions through extracellular matrix components and multiple growth factors have been shown to promote tumor progression. Among those, increases in both TGF-β (transforming growth factor beta) activities and periostin expression were associated with tumor cell survival, proliferation and metastasis. TGF-β role in breast cancer progression including its ability to promote periostin expression has been extensively studied. In contrast, the role of periostin in cancer progression remains to be fully understood. Thus, the present study aimed to determine whether TGF-β and periostin have effect on each other’s expressions in breast tumor and stroma cells using in vitro cell models. Through Western blot analyses and ELISAs, the periostin and TGF-β expressions of both stroma and tumor cells were analyzed following TGF-β and periostin treatments, respectively. The results indicate that TGF-β treatments led to significant increase in periostin expression in fibroblasts (p&lt;0.05). In addition, periostin was differentially expressed by human breast cancer cells following TGF-β1 treatment. The TGF-β activities involved activation of pSMAD2 in both L929 fibroblasts and MCF10A mammary cells. Taken together, all experimental data indicate that within the breast tumor TGF-β and periostin likely participate in a regulation loop. Whether this putative regulation loop is critical to metastasis remains to be determined. Should periostin play a critical role in breast cancer progression, it could become a specific target in the preventive and/or therapeutic development of breast cancer patients.

Made available in DSpace on 2014-06-11T19:23:43Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-02-14Bitstream added on 2014-06-13T18:51:12Z : No. of bitstreams: 1 ramos_cs_me_jabo.pdf: 210766 bytes, checksum: 2e27c3b1ba3e3555dc8986648fe65446 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Tumor de mama é a neoplasia mais freqüente em cadelas, entretanto, há controvérsias sobre os fatores que influenciam o seu desenvolvimento. Em estudos epidemiológicos destaca-se que os fatores ambientais são responsáveis por, pelo menos, 80% da incidência do câncer de mama em humanos. Com o objetivo de estabelecer fatores ambientais que possam contribuir para o desenvolvimento das neoplasias mamárias em cadelas, foram avaliadas as cadelas que se atendidas no Hospital Veterinário Governador Laudo Natel com tumores mamários, durante o período de julho 2008 a julho de 2010. Estas foram submetidas à mastectomia e exame histopatológico. Informações sobre os fatores epidemiológicos, aos quais, os animais se submeteram foram obtidas mediante questionários aplicados aos proprietários e estas foram associadas com o tipo histológico e grau de malignidade da neoplasia. Constatou-se que, estatisticamente, através do Teste Exato de Fisher a 5%, a idade, o porte, o uso de anticoncepcionais, o número de partos, a ocorrência de pseudogestação, a inalação passiva da fumaça de cigarro, o histórico de doenças anteriores, o tipo de alimentação, a conformação corporal e o nível de contato com os proprietários, influenciam no grau de agressividade da neoplasia. De forma contrária, castração anterior, localização das massas e presença de ulceração não demonstram interferência / Mammary gland tumor is one of the most common neoplasia in females dogs, however, there is controversy about the factors influencing its development. The cancer research is very important, since they are biological models for early diagnosis, more accurate prognoses and more efficient therapeutic procedures. Epidemiological studies show that environmental factors are responsible for at least 80% of the incidence of breast cancer in humans. Aiming to determinate environmental factors which may contribute to the development of mammary gland tumors, female dogs were evaluated. These females presented the “Governor Laudo Natel” Veterinary Hospital with pre-existing mammary gland tumors, during the period July 2008 to July 2010. They were submitted to mastectomy and to histopathologic exams. Information about epidemiological factors was obtained by questionnaires to the owners, and these were correlated with histologic type and grade of malignancy of the tumor. It was found that, statistically, by Fisher's exact test at 5%, age, size, contraceptive use, number of deliveries, the occurrence of pseudopregnancy, the passive inhalation of cigarette smoke, history of early diseases, the type of food, body shape and level of contact with the owners, influence the degree of aggressiveness of the tumor histological type. In contravention, previous castration, location of the masses and the presence of ulceration did not show interference

Orientador: Antonio Carlos Alessi / Banca: Sabryna Gouveia Calazans / Banca: Rosemeri de Oliveira Vasconcelos / Resumo: Tumor de mama é a neoplasia mais freqüente em cadelas, entretanto, há controvérsias sobre os fatores que influenciam o seu desenvolvimento. Em estudos epidemiológicos destaca-se que os fatores ambientais são responsáveis por, pelo menos, 80% da incidência do câncer de mama em humanos. Com o objetivo de estabelecer fatores ambientais que possam contribuir para o desenvolvimento das neoplasias mamárias em cadelas, foram avaliadas as cadelas que se atendidas no Hospital Veterinário Governador Laudo Natel com tumores mamários, durante o período de julho 2008 a julho de 2010. Estas foram submetidas à mastectomia e exame histopatológico. Informações sobre os fatores epidemiológicos, aos quais, os animais se submeteram foram obtidas mediante questionários aplicados aos proprietários e estas foram associadas com o tipo histológico e grau de malignidade da neoplasia. Constatou-se que, estatisticamente, através do Teste Exato de Fisher a 5%, a idade, o porte, o uso de anticoncepcionais, o número de partos, a ocorrência de pseudogestação, a inalação passiva da fumaça de cigarro, o histórico de doenças anteriores, o tipo de alimentação, a conformação corporal e o nível de contato com os proprietários, influenciam no grau de agressividade da neoplasia. De forma contrária, castração anterior, localização das massas e presença de ulceração não demonstram interferência / Abstract: Mammary gland tumor is one of the most common neoplasia in females dogs, however, there is controversy about the factors influencing its development. The cancer research is very important, since they are biological models for early diagnosis, more accurate prognoses and more efficient therapeutic procedures. Epidemiological studies show that environmental factors are responsible for at least 80% of the incidence of breast cancer in humans. Aiming to determinate environmental factors which may contribute to the development of mammary gland tumors, female dogs were evaluated. These females presented the "Governor Laudo Natel" Veterinary Hospital with pre-existing mammary gland tumors, during the period July 2008 to July 2010. They were submitted to mastectomy and to histopathologic exams. Information about epidemiological factors was obtained by questionnaires to the owners, and these were correlated with histologic type and grade of malignancy of the tumor. It was found that, statistically, by Fisher's exact test at 5%, age, size, contraceptive use, number of deliveries, the occurrence of pseudopregnancy, the passive inhalation of cigarette smoke, history of early diseases, the type of food, body shape and level of contact with the owners, influence the degree of aggressiveness of the tumor histological type. In contravention, previous castration, location of the masses and the presence of ulceration did not show interference / Mestre

The high rate of relapse often seen in breast cancer patients has been suggested to be the result of a small subset of chemotherapy-resistant cancer stem cells (CSCs), believed to be responsible for initiating tumor formation. These CSCs possess the capability to self-renew and give rise to a hierarchy of cells which makes up the bulk of a tumor. Neurotransmitters have been suggested to influence CSC self-renewal and proliferation capabilities, and antagonists of neurotransmission pathways have been implicated as possible treatment methods for chemo-resistant tumors. Using nicotinic acetylcholine receptor (nAChR) antagonists in sphere-forming assays, we have identified a very promising candidate compound: MG624. We found this compound to have a high selectivity for sphere-forming cells over non-sphere-forming cells in vitro, in a dose-dependent relationship, across a panel of cell lines as well as in patient-derived xenograft cells. This was validated in two ex vivo assays, where tumor formation was significantly delayed in mice injected with MG624-treated HCC1954 cells at both the IC50 and IC90 of the compound, indicating that MG624 does indeed target functional BTICs. MG624 was also found to synergize with both taxotere and doxorubicin chemotherapies in vitro, and shrink tumors in NOD/SCID mice when combined with taxotere in vivo. MG624 in combination with taxotere was found to induce apoptosis, and prevent cells from entering into the M-phase of the cell cycle. Interestingly, MG624 was found to eliminate intratumoral fibroblasts in combination with taxotere, despite taxotere being found to recruit fibroblasts to the tumor site when used on its own. Most importantly, the combination of MG624 and taxotere was found to significantly delay tumor progression/relapse in mice, indicating that MG624 may be an excellent candidate compound to one day be combined with chemotherapy to provide durable remission to breast cancer patients. / Thesis / Master of Science (MSc)

Breast cancer therapy resistance and disease recurrence are driven by an infrequent population of stem-like tumor cells, termed breast cancer stem cells or tumor-initiating cells (BTIC). Whereas drugs that target BTIC could be combined with conventional therapies to provide durable remissions, identifying such agents has been difficult. To achieve the latter, our lab screened more than 35,000 compounds for their capacity to reduce the activity of BTIC-enriched mouse mammary tumorspheres, wherein we identified numerous antagonists of multiple serotonin receptors (HTRs). The serotonergic antagonist that prevented sphere formation with the highest potency is a highly selective antagonist of HTR5A, SB-699551. We subsequently demonstrated that this agent affects BTIC activity in breast tumor cell lines representative of all clinical and molecular subtypes of breast cancer. Whereas the primary target of SB-699551 is known, the downstream signaling pathways responsible for its anti-BTIC effect remains enigmatic. The goal of this thesis work was to elucidate the signaling pathways downstream of HTR5A in human breast tumor cell lines. We used a phospho-proteomic approach to establish that treatment of human SB-699551 affects the phosphorylation of proteins involved in the Gi-coupled and the PI3K/AKT/mTOR signaling axes. Moreover, we demonstrated that selective antagonists of PI3K, AKT, and mTOR phenocopied the effect of SB-699551 in tumorsphere forming assays. Taken together, our data suggests that SB-699551 elicits its effect through the PI3K/AKT/mTOR signaling pathways downstream of HTR5A. / Thesis / Master of Health Sciences (MSc) / Accumulating data suggests that the progression of breast cancer is driven by a rare population of breast tumor-initiating cells (BTIC). BTIC lie dormant during conventional therapy and initiate recurrence after such therapies are withdrawn. Hence, there is an urgent need to develop drugs that target BTIC that can be combined with the current standard of care to improve the durability of remission. With the latter objective in mind, our lab previously determined that antagonists of serotonin signaling target BTIC. One of the agents that we identified in our screen inhibits the activity of serotonin receptor 5A (HTR5A). The exact signaling mechanism whereby inhibition of HTR5A leads to a loss in BTIC activity was enigmatic. Hence, this thesis aims to elucidate the signaling pathways downstream of HTR5A in breast cancer. Knowledge of the latter will help identify a plausible mechanism in addition to identifying biomarkers of therapy efficacy.