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- Indukuri, Rajitha, et al.
(författare)
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Estrogen Receptor Beta Influences the Inflammatory p65 Cistrome in Colon Cancer Cells
- 2021
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Ingår i: Frontiers in Endocrinology. - : FRONTIERS. - 1664-2392. ; 12, s. 1-13
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Tidskriftsartikel (refereegranskat)abstract
- Inflammation is a primary component of both initiation and promotion of colorectal cancer (CRC). Cytokines secreted by macrophages, including tumor necrosis factor alpha (TNFα), activates the pro-survival transcription factor complex NFκB. The precise mechanism of NFκB in CRC is not well studied, but we recently reported the genome-wide transcriptional impact of TNFα in two CRC cell lines. Further, estrogen signaling influences inflammation in a complex manner and suppresses CRC development. CRC protective effects of estrogen have been shown to be mediated by estrogen receptor beta (ERβ, ESR2), which also impacts inflammatory signaling of the colon. However, whether ERβ impacts the chromatin interaction (cistrome) of the main NFκB subunit p65 (RELA) is not known. We used p65 chromatin immunoprecipitation followed by sequencing (ChIP-Seq) in two different CRC cell lines, HT29 and SW480, with and without expression of ERβ. We here present the p65 colon cistrome of these two CRC cell lines. We identify that RELA and AP1 motifs are predominant in both cell lines, and additionally describe both common and cell line-specific p65 binding sites and correlate these to transcriptional changes related to inflammation, migration, apoptosis and circadian rhythm. Further, we determine that ERβ opposes a major fraction of p65 chromatin binding in HT29 cells, but enhances p65 binding in SW480 cells, thereby impacting the p65 cistrome differently in the two cell lines. However, the biological functions of the regulated genes appear to have similar roles in both cell lines. To our knowledge, this is the first time the p65 CRC cistrome is compared between different cell lines and the first time an influence by ERβ on the p65 cistrome is investigated. Our work provides a mechanistic foundation for a better understanding of how estrogen influences inflammatory signaling through NFκB in CRC cells.
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| 2. |
- Indukuri, Rajitha
(författare)
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Estrogen receptor beta transcriptional regulation: A potential mechanism for colon cancer prevention
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Colorectal cancer (CRC) is the third leading cause of death from cancer in both men andwomen in the Western world. Improved screening efforts, surveillance, and treatment havereduced CRC mortality in older patients. However, the incidence is increasing in young adults,even in the absence of CRC family history. This may indicate an influence of increasingobesity, changed dietary patterns, and lifestyle factors. The progression of CRC is a multistepprocedure that takes 10-15 years, thus offering a time to implement preventative measures andearly detection. There is a critical need to develop more effective preventive therapies due tothe risks posed by current prevention therapies. The best CRC prophylactic agent should beboth safe and suitable to use for a long time (1).In preclinical studies, estrogen has been shown to protect from CRC, and substantial evidencesuggests it is through estrogen receptor beta (ERβ). Natural ERβ selective agonists have beentested in phase II clinical trials to treat menopause symptoms and proven to be safe and welltolerated with no side effects (2, 3). Thus, selective activation of ERβ with selective agonists,which do not activate estrogen receptor alpha (ERα), is a potential clinical approach inpreventing adenomatous polyps progression into CRC. However, the mechanism of thesebeneficial ERβ effects is not well understood, and there is a significant knowledge gap in thisarea.The overall aim of this thesis was to identify the mechanistic background of the intestinal ERβmediated antitumorigenic effects in the colon and further to explore ERβ as a preventativeapproach in CRC. One specific aim was to determine whether ERβ present specifically in colonepithelium is responsible for protecting from CRC, which is addressed in Paper I. Tounderstand the impact of ERβ in protecting from colitis-associated CRC (CA-CRC), we haveinduced colitis in intestinal-specific ERβ knockout mice of both sexes. The loss of intestinalERβ aggravated CA-CRC in a sex-dependent manner. The incidence of tumors increased inmales, while in females, the size of the tumors was enhanced. We identified that ERβ attenuatestumor necrosis factor alpha (TNFα) induced epithelial cell damage and modulates theregulation of key nuclear factor-κB (NFκB) members. As a direct consequence, ERβ was foundto reduce inflammation and to control intestinal crypt cell proliferation.Another aim was to explore transcriptional regulation by ERβ through mapping of chromatinbinding sites and interaction with NFκB, which is studied in Paper II and IV. Commonly usedERβ antibodies have been shown to be unspecific towards ERβ; this study used a validatedERβ antibody to map genome-wide ERβ binding sites in colon cancer cells. We observed thatthe presence of ERβ also modulated the regulatory chromatin mark H3K27AC in potentialenhancers of transcriptional regulation, Wnt signaling, and cell proliferation. Further, motifanalysis indicated a novel ERβ colon-specific cross-talk with TCF, and KLF motifs supporteda interaction between β-catenin/TCF and ERβ. We found that ERβ binds and regulates severalimportant tumor suppressors and oncogenes in CRC cells, such as CST5 and LRP6, consistentwith its proposed antitumorigenic activity. We also revealed the p65 cistrome in CRC cell lines and showed that ERβ alters the p65 chromatin binding in a cell-type-dependent manner. Wefound that ERβ chromatin binding sites were enriched among circadian clock genes and alsothat ERβ modulates p65 binding to core clock genes in CRC cells, indicating potential crosstalk between ERβ and circadian clock gene regulation.The final aim was to investigate the impact of ERβ, and estrogen signaling in high-fat diet(HFD) induced inflammation in colon, explored in paper III. We fed mice with an HFD for 13weeks and treated them with estrogenic ligands for the last three weeks prior to sacrifice. Thecolon transcriptome showed predominant sex differences, and selective activation of ERβreduced macrophage infiltration and epithelial cell proliferation induced by HFD. Wedemonstrated that ERβ opposes HFD-induced dysregulation of core circadian clock genes invivo, further strengthening the role of ERβ in circadian rhythm.Taken together, these results highlight the chemopreventive potential of ERβ in CRC in bothsexes. The identified cross-talk with TNFα/NFκB pathway, Wnt signaling, regulating genesinvolved circadian clock, and tumorigenesis reflected ERβ protection/antitumor activityagainst CRC progression and development (as illustrated in Figure 1).
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| 3. |
- Indukuri, Rajitha, et al.
(författare)
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Genome-wide estrogen receptor β chromatin binding in humancolon cancer cells reveals its tumor suppressor activity
- 2021
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Ingår i: International Journal of Cancer. - : Wiley. - 0020-7136 .- 1097-0215.
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Tidskriftsartikel (refereegranskat)abstract
- Colorectal cancer (CRC) is the third leading cause of cancer death in the western world. In women, menopausal hormone therapy has been shown to reduce CRC incidence by 20%. Studies demonstrate that estrogen activating estrogen receptor beta (ERβ) protects against CRC. ERβ is a nuclear receptor that regulates gene expression through interactions with the chromatin. This molecular mechanism is, however, not well characterized in colon. Here, we present for the first time, the cistrome of ERβ in different colon cancer cell lines. We use cell lines engineered to express ERβ, optimize and validate an ERβ antibody for chromatin-immunoprecipitation (ChIP), and perform ChIP-Seq. We identify key binding motifs, including ERE, AP-1, and TCF sites, and we determine enrichment of binding to cis-regulatory chromatin sites of genes involved in tumor development, cell migration, cell adhesion, apoptosis, and Wnt signaling pathways. We compare the corresponding cistromes of colon and breast cancer and find that they are conserved for about a third of genes, including GREB1, but that ERβ tethering to TCF and KLF family motifs is characteristic for colon. We exemplify upregulation of putative CRC tumor suppressor gene CST5 where ERβ in colon cells binds to cis-regulatory regions nearby (−351 bp) the transcriptional start site. Our work provides a foundation for understanding the mechanism of action of ERβ in CRC prevention.
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