Dietary starch that escapes digestion in the small intestine may be quantitatively more important than dietary fibre as substrate for fermentation. The products of fermentation have important implications in the pathogenesis of colorectal cancer and other diseases of the large bowel which are uncommon in Africans, but have a high prevalence in Western populations. Maize porridge is a staple of most Blacks in South Africa. Stale maize porridge (high resistant starch - HRS) seems to induce greater fermentation in the large bowel than fresh maize porridge (low resistant starch - LRS). In the present study, healthy colostomy subjects fed stale maize porridge had significantly more production of SCFA (short chain fatty acids) (mean SCFA - HRS = 182,6; mean SCFA - LRS = 116,1; p<0,05) in their colostomy effluent together with a significant drop in stool pH (mean pH - HRS = 5,91; mean pH - LRS = 6,70; p<0.G01). The SCFA butyrate tmean - HRS = 35,1; mean - LRS - LRS = 17,6; p<0,05) and acetate (mean - HRS = 93,9; mean - LRS = 65,8; p <0,05) were significantly elevated on the stale maize porridge diet when compared with consumption of fresh maize porridge. SCFA, propionate (mean - HRS = 43,1; mean - LRS = 24,8; p=G,Q5), also increased with stale maize porridge, but was not statistically significant. A high resistant starch diet and its resultant increase in fermentation products may be partly responsible in protecting the Black population against colorectal cancers and other large bowel diseases.

No description available.

In this thesis Prognoslic factors of early recurrence of colorectal liver metastases after surgical therapy the autor characterizes the epidemidemiology, diagnostics and treatment of colorectal liver metastases (CLM) in relation to biological activity of tumour and the possibilities of determination. Contemporary the author introduces to problematics of tumour markers, which determine CLM and to clinical prognostic factors of CLM.

京都大学 / 新制・課程博士 / 博士(医学) / 甲第24196号 / 医博第4890号 / 新制||医||1060(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 伊藤 貴浩, 教授 妹尾 浩, 教授 永井 純正 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

京都大学 / 新制・課程博士 / 博士(医学) / 甲第24883号 / 医博第5017号 / 新制||医||1068(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 中島 貴子, 教授 石見 拓, 教授 中山 健夫 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

LINE-1 retrotransposons, also known as "jumping genes", are repetitive sequences capable of copying, pasting, and reinserting themselves into the genome. These events were documented at high frequency in various types of cancers, including colorectal cancer (CRC). Furthermore, the expression of proteins encoded by these elements, such as L1ORF1p, has been linked to cancer aggressiveness, stemness, and lower patient survival rates. Colorectal cancer stem cells (CCSC), constitute a small subset of cells endowed with pluripotency and self-renewal abilities. They play roles in tumorigenesis, cancer aggressiveness, drug resistance, cancer recurrence, and metastasis. Conventional chemotherapeutics primarily target bulk tumor cells and tend to spare cancer stem cell populations. Consequently, targeting CCSC is expected to significantly increase complete remission and survival rates in CRC patients. Here, I have characterized specific aspects of a novel repurposed drug that effectively targets CCSC, reactivates the expression of transposable elements and, consequently, triggers an innate immune response. Further, I tested an in silico drug screening approach to identify compounds with high predicted affinity for the RNA binding domains of L1ORF1p, a key protein for the LINE1 retrotransposition event to occur, from a virtual drug library. Two lead compounds, both FDA-approved drugs, were identified and evaluated for their capacity to block L1ORF1p nuclear translocation, a needed step to complete the LINE1 lifecycle, as well as their capacity to decrease LINE-1 retrotransposition levels. In addition, I established a protocol for the isolation, culture, propagation, and cryopreservation of patient-derived normal colonic organoids. This protocol is crucial to the establishment of a colonic organoid biobank, representing a powerful resource to assess cancer-selective toxicity of putative CCSC-targeting compounds. Together, this thesis emphasizes the importance of transposable elements in CRC and contributes to the establishment of a gold standard ex vivo disease-modeling system for the discovery of new therapeutic agents.

No description available.

Metformin is the most common type 2 diabetes therapy, and may also reduce colorectal cancer growth. Currently, two mechanisms driving reduced cancer growth are considered: 1) Regulation of glucose and insulin levels, which may support cancer growth, and 2) Direct entry into cancer cells to activate the AMP-activated kinase (AMPK) protein, and inhibit cell growth pathways. The gut microbiome is the community of commensal microorganisms in the gastrointestinal tract. It is also affected by metformin, and may elevate production of short-chain fatty acids (SCFAs). Therefore, this thesis aimed to clarify how metformin may inhibit colorectal cancer growth and if the microbiome is involved. The hyperglycemic-responsive, murine-derived MC38 colon cancer cell line was used to test these effects. This model was confirmed to experience growth stimulation caused by high-fat diet (HFD) feeding in mice. Daily i.p. injections of metformin (100mg/kg) had no measurable effect on glucose and insulin sensitivity, or MC38 tumor growth. Oral metformin (250mg/kg) improved glucose tolerance and inhibited MC38 tumor growth in HFD-fed mice. To see if the gut microbiome is required for this effect, the antibiotic ampicillin was used to limit the gut microbiome. The addition of ampicillin blunted metformin’s glucose sensitization and tumor inhibition effects. A fecal microbiome transfer model was then used to isolate the role of the microbiome. Conventional mice fed HFD and gavaged with feces from metformin-treated donors experienced no glucose or insulin tolerance improvements. However, tumor growth was decreased by 30%, and serum SCFAs concentrations were elevated. The SCFA butyrate inhibited in vitro MC38 colony growth, but did not activate AMPK. These data suggest that metformin alters the gut microbiome, and fecal transfer from metformin-treated animals can uncouple MC38 tumor growth inhibition from the glucose homeostasis effects of metformin. These novel findings support a new mechanism for metformin to prevent cancer growth and development. / Thesis / Doctor of Philosophy (PhD) / Metformin is the most commonly used type 2 diabetes therapy, and may also reduce colorectal cancer growth. Anti-cancer effects may be caused by: 1) decreased glucose and insulin levels, which support cancer growth; or 2) entry into cancer cells to directly decrease cell growth. The gut microbiome, microorganisms that live symbiotically in the gastrointestinal tract, is also affected by metformin. This thesis aimed to clarify how metformin can inhibit cancer, and if the microbiome is involved. Mice treated with metformin had improved glucose metabolism and decreased colorectal tumor growth; when an antibiotic was introduced, this effect was lost. A fecal microbiome transfer model was used to determine if the microbiome is driving this effect. Mice receiving feces from metformin treated mice also experienced tumor growth inhibition. This suggests that the gut microbiome is involved in the anti-cancer effects of metformin, and is a new potential mechanism of action.

Fusobacterium are Gram-negative anaerobic bacteria that colonize a variety of eukaryotes including cattle and humans. In humans, Fusobacterium coordinates the central architecture of the oral biofilm by expressing an abundance of outer membrane adhesins that mediate bridging between early and late colonizing bacteria. While Fusobacterium are mostly considered commensal microorganisms, they can also become an opportunistic pathogen that spreads throughout the human body and promote the development of oral and extra-oral infections and diseases including colorectal cancer. Importantly for this work, many Fusobacterium species and strains are recalcitrant to genetic manipulation, the majority of which has led to hindrance in the study of their biology, molecular mechanisms, and pathogenesis. The genetic intractability of Fusobacterium is an obstacle for the development of future treatments for diseases associated with these anaerobic bacteria. Therefore, the creation of tools to enhance genome editing in target species is crucial to understand the molecular mechanisms driving Fusobacterium infections. This dissertation exploits innate and adaptive defense systems present in Fusobacterium for their use as molecular tools for genome editing. Accordingly, we first investigated restriction-modification systems with a focus on the role of DNA methyltransferases and endonucleases in host defense and genetic recalcitrance in several strains of Fusobacterium through bioinformatic and biochemical approaches. Altogether, over 15 DNA methyltransferases were characterized. Most notably, we identified and characterized two type II DNA methyltransferases that are capable of methylating plasmid DNA by treating with purified enzymes in-vitro and coexpression approaches in Escherichia coli strains, enabling an statiscally improved transformation efficiency via electroporation in F. nucleatum. Also contained in this dissertation is the first detailed description of CRISPR-Cas adaptive immunity systems present in Fusobacterium strains. Most of the discovered CRISPR-Cas systems in Fusobacterium belong to Class 1 systems. Nonetheless we identified Type II-A and Type VI-C Class 2 systems. The discovery of Cas9 and Cas13c effectors respectively from these systems will be crucial in the development of a new generation of genome-editing tools in Fusobacterium. The studies included in this dissertation provide the framework for overcoming Fusobacterium genetic recalcitrance by the implementation of host mimicking techniques. By utilizing restriction-modification system enzymes and the adaptive immunity CRISPR-Cas systems, we will gain a better understanding of how Fusobacterium modulates infections and diseases, and ultimately explore the potential of novel therapeutic treatments. / Doctor of Philosophy / The oral cavity has one of the most diverse and largest microbial populations, where microorganisms are capable of colonizing hard surfaces of the teeth and the soft tissues of the oral mucosa. A fundamental member of the oral microbiome is Fusobacterium, a Gram-negative bacterium which coordinates the oral biofilm formation by interacting with other microorganisms. In recent studies, Fusobacterium has been associated with oral and extra-oral infections and diseases including periodontitis, preterm birth, Lemiere syndrome, inflammatory bowel disease and colorectal cancer. Importantly, many Fusobacterium species and strains are challenging to study due to their inability to uptake exogenous DNA and lack of genetic tools, which has hindered the study of their biology, molecular mechanisms and pathogenesis. The challenges in the genetic manipulation of Fusobacterium present a significant obstacle for the development of future treatments for diseases associated with these bacteria. Therefore, the creation of tools to expand bacterial transformation of exogenous DNA and genome editing to more than just one Fusobacterium species is crucial to understand how Fusobacterium is causing these infections. This dissertation explores the presence and utilization of defense systems, which defend bacteria from phage attack, as an alternative to improve Fusobacterium genetics. Accordingly, we first studied a set of over 15 enzymes that recognize a specific DNA pattern and add a methyl group (DNA methyltransferases) to specific nucleotides in several strains of Fusobacterium. We discovered that two of these enzymes improve Fusobacterium's ability of importing and genomically incorporating exogenous DNA after an electric discharge permeabilizes the bacterial membrane. Furthermore, for the first time we have described the composition of CRISPR-Cas bacterial defense systems, that detect invading DNA from viruses and provide protection to Fusobacterium strains. These systems have previously been successfully used as genetic tools to achieve genome editing. Thus, their further characterization is warranted to create novel molecular tools in Fusobacterium. Altogether, these discoveries will lead to a better comprehension of Fusobacterium biology in infections and diseases, while exploring novel therapeutic strategies.

Purpose: Given that CRC Screening disparities in people experiencing homelessness has been heavily understudied, the purpose of this study is to assess how existing knowledge and access to resources about CRC screenings affect the ability to obtain CRC screenings in people experiencing homelessness in Central Florida. Methods: In March 2023, a team of researchers surveyed subjects who do not have stable housing in two Central Florida locations: a local shelter and a resource center serving the predominantly unsheltered. The survey assessed current understanding of CRC screenings and available/lacking resources necessary for completing CRC screening in this population. There was a total sample size of 75 participants, with 36 participants from the shelter and 39 from the service center location. Our inclusion criteria included those who are undomiciled, age 45 and over who speak Spanish or English. Results: The results indicate that there is a statistical difference between those who are screened and not screened when assessing provider counseling (p<0.001), awareness of how to get screened (p<0.001) and access to the same medical provider every visit (p=0.0389). In regard to receipt of CRC screening, there were no statistically significant results when assessing demographics and other resource-related factors. Conclusion: Because data was collected in locations that provided resources, this study may not be representative of all undomiciled individuals in Florida, especially in rural areas. Our results imply a need for provider counseling, patient education and access to a primary care provider. More research needs to be conducted from the physician perspective to understand the context of existing barriers to CRC screening.