Effects of ursodeoxycholic acid on the gut microbiome and colorectal adenoma development

It has been previously reported that ursodeoxycholic acid (UDCA), a therapeutic bile acid, reduced risk for advanced colorectal adenoma in men but not women. Interactions between the gut microbiome and fecal bile acid composition as a factor in colorectal cancer neoplasia have been postulated but evidence is limited to small cohorts and animal studies. Using banked stool samples collected as part of a phase III randomized clinical trial of UDCA for the prevention of colorectal adenomatous polyps, we compared change in the microbiome composition after a 3-year intervention in a subset of participants randomized to oral UDCA at 8-10 mg/kg of body weight per day (n = 198) or placebo (n = 203). Study participants randomized to UDCA experienced compositional changes in their microbiome that were statistically more similar to other individuals in the UDCA arm than to those in the placebo arm. This reflected a UDCA-associated shift in microbial community composition (P 0.05). These UDCA-associated shifts in microbial community distance metrics from baseline to end-of-study were not associated with risk of any or advanced adenoma (all P > 0.05) in men or women. Separate analyses of microbial networks revealed an overrepresentation of Faecalibacterium prausnitzii in the post-UDCA arm and an inverse relationship between F prausnitzii and Ruminococcus gnavus. In men who received UDCA, the overrepresentation of F prausnitzii and underrepresentation of R gnavus were more prominent in those with no adenoma recurrence at follow-up compared to men with recurrence. This relationship was not observed in women. Daily UDCA use modestly influences the relative abundance of microbial species in stool and affects the microbial network composition with suggestive evidence for sex-specific effects of UDCA on stool microbial community composition as a modifier of colorectal adenoma risk.Partnership for Native American Cancer Prevention [NIH/NCI U54CA143924, U54CA143925]; NSF [1565100]; Biostatistics and Tissue Acquisition and Cellular/Molecular Analysis Shared Resources - NCI [P30CA023074]; [R01 CA151708]Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

The Chemical-Induced Genotoxicity of Depleted Uranium

Uranium has been mined for many years and used for fuel for nuclear reactors and materials for atomic weapons, ammunition, and armor. While the radioactivity associated with uranium mining has been linked to the development of lung and kidney cancers, and leukemia, little is known about the direct chemical genotoxicity of uranium. The overall hypothesis of the current research is that uranium can produce DNA damage by chemical genotoxicity mechanisms. Three specific aims were tested. In Aim 1, specific DNA lesions caused by direct interaction of uranium and DNA were investigated. Chinese Hamster Ovary cells (CHO) with mutations in various DNA repair pathways were exposed to 0 – 300 μM of soluble depleted uranium (DU) as uranyl acetate (UA) for 0 – 48 hr. Results indicate that UA readily enters CHO cells, with the highest concentration localizing in the nucleus. Clonogenics assay shows that UA is cytotoxic in each cell line with the greatest cytotoxicity in the base excision repair deficient EM9 cells and the nuclear excision repair deficient UV5 cells compared to the non-homologous end joining deficient V3.3 cells and the parental AA8 cells after 48 hr. This indicates that UA is forming DNA adducts that may be producing single strand breaks through hydrolysis rather than double strand breaks in CHO cells. Fast Micromethod® results indicate an increased amount of single strand breaks in the EM9 cells after 48 hr UA exposure compared to the V3.3 and AA8 cells. In Aim 2, the role of oxidative stress in producing DNA lesions was determined. Cellular oxidative stress has been implicated in the genotoxicity of many heavy metals as a mechanism of induced DNA damage. To investigate this possible mechanism, human bronchial epithelial cells (16HBE14o⁻) were exposed to 30 ppb (0.13 μM U) UA for 2 – 24 hr. UA did not significantly induce oxidative stress compared to untreated cells at 3 – 4 hr time points. These results suggest that cellular oxidative stress is not a major pathway of DU genotoxicity at low concentrations. In Aim 3, DNA damage response to uranium-induced DNA damage was investigated. It has been widely reported that metals can be genotoxic by inhibiting DNA repair. Cultured cells were co-exposed to 0.13 μM UA in the presence of 0 – 25 μM of etoposide for 0 – 48 hr. Results indicate that UA inhibited double strand break repair. Coexposures of etoposide and UA synergistically induced cytotoxicity compared to individual treatments and untreated cells. Co-exposed UA and etoposide treated 16HBE14o⁻ cells exhibited a decrease in phosphorylation of DNA repair proteins compared to etoposide treatments. Untreated and UA-treated 16HBE14o⁻ cells did not induce phosphorylation of DNA repair proteins. These results suggest that DU inhibits double strand break DNA repair at low concentrations in the presence of a known DNA double-strand damaging agent, etoposide. The inhibition of DNA repair by DU at environmentally relevant concentrations suggests a novel means by which uranium may exert its genotoxic effects. Results found at low dose exposures are not consistent with alterations seen with radioactivity, suggesting that the effects of uranium at low doses are due to its chemical genotoxic effects. Understanding how uranium reacts with DNA is important to better understand how this suspected carcinogen induces cancer and to help to elucidate mechanisms that produce cancers in people exposed to uranium

The chemical-induced genotoxicity of depleted uranium

Uranium has been mined for many years and used for fuel for nuclear reactors and materials for atomic weapons, ammunition, and armor. While the radioactivity associated with uranium mining has been linked to the development of lung and kidney cancers, and leukemia, little is known about the direct chemical genotoxicity of uranium. The overall hypothesis of the current research is that uranium can produce DNA damage by chemical genotoxicity mechanisms. Three specific aims were tested. In Aim 1, specific DNA lesions caused by direct interaction of uranium and DNA were investigated. Chinese Hamster Ovary cells (CHO) with mutations in various DNA repair pathways were exposed to 0 – 300 μM of soluble depleted uranium (DU) as uranyl acetate (UA) for 0 – 48 hr. Results indicate that UA readily enters CHO cells, with the highest concentration localizing in the nucleus. Clonogenics assay shows that UA is cytotoxic in each cell line with the greatest cytotoxicity in the base excision repair deficient EM9 cells and the nuclear excision repair deficient UV5 cells compared to the non-homologous end joining deficient V3.3 cells and the parental AA8 cells after 48 hr. This indicates that UA is forming DNA adducts that may be producing single strand breaks through hydrolysis rather than double strand breaks in CHO cells. Fast Micromethod® results indicate an increased amount of single strand breaks in the EM9 cells after 48 hr UA exposure compared to the V3.3 and AA8 cells. In Aim 2, the role of oxidative stress in producing DNA lesions was determined. Cellular oxidative stress has been implicated in the genotoxicity of many heavy metals as a mechanism of induced DNA damage. To investigate this possible mechanism, human bronchial epithelial cells (16HBE14o-) were exposed to 30 ppb (0.13 μM U) UA for 2 – 24 hr. UA did not significantly induce oxidative stress compared to untreated cells at 3 – 4 hr time points. These results suggest that cellular oxidative stress is not a major pathway of DU genotoxicity at low concentrations. In Aim 3, DNA damage response to uranium-induced DNA damage was investigated. It has been widely reported that metals can be genotoxic by inhibiting DNA repair. Cultured cells were co-exposed to 0.13 μM UA in the presence of 0 – 25 μM of etoposide for 0 – 48 hr. Results indicate that UA inhibited double strand break repair. Co-exposures of etoposide and UA synergistically induced cytotoxicity compared to individual treatments and untreated cells. Co-exposed UA and etoposide treated 16HBE14o- cells exhibited a decrease in phosphorylation of DNA repair proteins compared to etoposide treatments. Untreated and UA-treated 16HBE14o - cells did not induce phosphorylation of DNA repair proteins. These results suggest that DU inhibits double strand break DNA repair at low concentrations in the presence of a known DNA double-strand damaging agent, etoposide. The inhibition of DNA repair by DU at environmentally relevant concentrations suggests a novel means by which uranium may exert its genotoxic effects. Results found at low dose exposures are not consistent with alterations seen with radioactivity, suggesting that the effects of uranium at low doses are due to its chemical genotoxic effects. Understanding how uranium reacts with DNA is important to better understand how this suspected carcinogen induces cancer and to help to elucidate mechanisms that produce cancers in people exposed to uranium

Building capacity for collaborative research between basic scientists and underrepresented communities in cancer research

Purpose: Basic science research is critical for understanding biological mechanisms essential to advances in cancer prevention, diagnoses and treatment. However, most of this research is conducted outside of the purview of community observation or input, leaving these research processes mysterious and subsequent findings disconnected from the communities they intend to benefit. This paper discusses strategies to build capacity for collaborations between basic scientists and Hispanic community members at the University of Arizona Cancer Center (UACC). Methods: Through partnership of the Cancer Biology Program and Office of Community Outreach and Engagement both at UACC, the Research Outreach for Southern Arizona (ROSA) program was developed as a way to forward the following strategies to build capacity for collaboration: forming a community working group, launching a community and student ambassador program, hosting scientific cafés and developing a community-based survey. Results: The strategies underpinning the ROSA program have been integral in bridging dialogue between basic scientists and the community and fostering bidirectional learning opportunities. Each of the strategies presented have documented successes and based on the lessons learned, they have evolved into productive and integral parts of UACC’s overall strategy of bridging scientific research and communities. Conclusion: While the strategies discussed are evolving, they help foster dialogue and exchange between basic scientists and community members that demystifies basic science research and facilitates culturally tailored approaches to address health disparities of vulnerable communities. These strategies also have the potential to shift cancer research into a paradigm that is more collaborative and transformative.12 month embargo; first published 03 June 2023This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Uranyl acetate induced DNA single strand breaks and AP sites in Chinese hamster ovary cells

The aim of this study is to characterize the genotoxicity of depleted uranium (DU) in Chinese Hamster Ovary cells (CHO) with mutations in various DNA repair pathways. CHO cells were exposed to 0-300 mu M of soluble DU as uranyl acetate (UA) for 0-48 h. Intracellular UA concentrations were measured via inductively coupled mass spectrometry (ICP-MS) and visualized by transmission electron microscopy (TEM). Cytotoxicity was assessed in vitro by clonogenic survival assay. DNA damage response was assessed via Fast Micromethod (R) to determine UA-induced DNA single strand breaks. Results indicate that UA is entering the CHO cells, with the highest concentration localizing in the nucleus. Clonogenic assays show that UA is cytotoxic in each cell line with the greatest cytotoxicity in the base excision repair deficient EM9 cells and the nuclear excision repair deficient UV5 cells compared to the non-homologous end joining deficient V3.3 cells and the parental AA8 cells after 48 h. This indicates that UA is producing single strand breaks and forming UA DNA adducts rather than double strand breaks in CHO cells. Fast Micromethod (R) results indicate an increased amount of single strand breaks in the EM9 cells after 48 h UA exposure compared to the V3.3 and AA8 cells. These results indicate that DU induces DNA damage via strand breaks and uranium-DNA adducts in treated cells. These results suggest that: (1) DU is genotoxic in CHO cells, and (2) DU is inducing single strand breaks rather than double strand breaks in vitro.National Institutes of Health [CA096281, CA096320, ES019703, F31ES014971]; Partnership for Native American Cancer Prevention [U54CA143924]; Southwest Environmental Health Sciences Centers [P30ES006694]; Alfred P. Sloan Foundation; More Graduate Education at Mountain States Alliance12 month embargo; published online: 24 April 2018This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Lack of evidence that ursodeoxycholic acids effects on the gut microbiome influence colorectal adenoma risk

Objective We previously reported that Ursodeoxycholic acid (UDCA), a therapeutic bile acid, reduces risk for advanced colorectal adenoma in men but not women. Interactions between the gut microbiome and fecal bile acid composition as a factor in colon cancer neoplasia have been postulated but evidence is limited to small cohorts and animal studies. Design Using banked stool samples collected as part of a phase III randomized clinical trial of UDCA for the prevention of colorectal neoplasia, we compared change in the microbiome composition after 3 years intervention in a subset of participants randomized to 8–10 mg/kg of body weight UDCA (n=198) to placebo (n=203). UDCA effects on the microbiome, sex and adenoma outcome were investigated. Results Study participants randomized to UDCA experienced compositional changes in their microbiome that were statistically more similar to other individuals in the UDCA arm than to those in the placebo arm. This change reflected an UDCA-associated shift in microbial community distance metrics (P 0.05). These UDCA-associated shifts in microbial community distance metrics from baseline to end-of-study were not associated with risk of any or advanced adenoma (all P> 0.05) in men or women. Conclusion Despite a large sampling of randomized clinical trial participants, daily UDCA use only modestly influenced the relative abundance of microbial species in stool with no evidence for effects of UDCA on stool microbial community composition as a modifier of colorectal adenoma risk