Project description:Methionine, a sulfur-containing essential amino acid, is a key component of dietary proteins important for protein synthesis, sulfur metabolism, antioxidant defense, and signaling. However, the role of methionine in cancer progression remains inconclusive. On one hand, dietary methionine restriction is known to repress cancer growth and improve cancer therapy in xenografted tumors. On the other hand, methionine is also critical for T cell activation and differentiation, making it a potential tumor suppression nutrient by enhancing T cell-mediated anti-tumor immunity. Here we investigated the interaction between dietary methionine, immune cells, and cancer cells by allografting CT26.WT mouse colon carcinoma cells into immunocompetent Balb/c mice or immunodeficient NSG mice, then analyzed how dietary methionine contents affect their growth. Our results show that dietary methionine restriction suppresses tumor growth in immunodeficient NSG mice but promotes tumor progression in immunocompetentt Balb/c mice.
Project description:Colorectal cancer is a leading cause of cancer-related deaths. Mutations in the innate immune receptor AIM2 are frequently identified in patients with colorectal cancer, but how AIM2 modulates colonic tumorigenesis is unknown. Here, we found that Aim2-deficient mice were hypersusceptible to colonic tumor development. Production of inflammasome-associated cytokines and other inflammatory mediators were largely intact in Aim2-deficient mice, however, intestinal stem cells were prone to uncontrolled proliferation. Aberrant Wnt signaling expanded a population of tumor-initiating stem cells in the absence of AIM2. Susceptibility of Aim2-deficient mice to colorectal tumorigenesis was enhanced by a dysbiotic gut microbiota, which was reduced by reciprocal exchange of gut microbiota with wild-type healthy mice. These findings uncover a synergy between a specific host genetic factor and gut microbiota in determining the susceptibility to colorectal cancer. Therapeutic modulation of AIM2 expression and microbiota has the potential to prevent colorectal cancer. We used microarrays to compare the transcriptome Aim2 deficent mice to wild type mice in colon tumor and colitis samples. Here were 12 mice in total, 3 for each genotype and tissue combination.
Project description:Dietary methionine restriction is associated with a reduction in tumor growth in preclinical studies and an increase in lifespan in animal models. The mechanism by which methionine restriction inhibits tumor growth while sparing normal cells is incompletely understood, except for the observation that normal cells can utilize methionine or homocysteine interchangeably (methionine independence) while most cancer cells are strictly dependent on methionine availability. Here, we compared a typical methionine dependent and a rare methionine independent melanoma cell line. We show that replacing methionine, a methyl donor, with homocysteine generally induced hypomethylation in gene promoters. This decrease was similar in methionine dependent versus methionine independent cells. There was only a low level of pathway enrichment, suggesting that the hypomethylation is generic rather than gene specific. Whole proteome and transcriptome were also analyzed. This analysis revealed that contrarily to the effect on methylation, the replacement of methionine with homocysteine had a much greater effect on the transcriptome and proteome of methionine dependent cells than methionine independent cells. Interestingly, the methionine adenosyltransferase 2A (MAT2A), responsible for the synthesis of s-adenosylmethionine from methionine, was equally strongly upregulated in both cell lines. This suggests that the absence of methionine is equally detected but trigger different outcomesin methionine dependent versus independent cells. Our analysis reveals the importance of cell cycle control, DNA damage repair, translation, nutrient sensing, oxidative stress and tight junctions in the cellular response to methionine stress in melanoma.
Project description:Dietary methionine restriction is associated with a reduction in tumor growth in preclinical studies and an increase in lifespan in animal models. The mechanism by which methionine restriction inhibits tumor growth while sparing normal cells is incompletely understood, except for the observation that normal cells can utilize methionine or homocysteine interchangeably (methionine independence) while most cancer cells are strictly dependent on methionine availability. Here, we compared a typical methionine dependent and a rare methionine independent melanoma cell line. We show that replacing methionine, a methyl donor, with homocysteine generally induced hypomethylation in gene promoters. This decrease was similar in methionine dependent versus methionine independent cells. There was only a low level of pathway enrichment, suggesting that the hypomethylation is generic rather than gene specific. Whole proteome and transcriptome were also analyzed. This analysis revealed that contrarily to the effect on methylation, the replacement of methionine with homocysteine had a much greater effect on the transcriptome and proteome of methionine dependent cells than methionine independent cells. Interestingly, the methionine adenosyltransferase 2A (MAT2A), responsible for the synthesis of s-adenosylmethionine from methionine, was equally strongly upregulated in both cell lines. This suggests that the absence of methionine is equally detected but trigger different outcomesin methionine dependent versus independent cells. Our analysis reveals the importance of cell cycle control, DNA damage repair, translation, nutrient sensing, oxidative stress and tight junctions in the cellular response to methionine stress in melanoma.
Project description:Since both endogenous synthesis in tumor cells and bacterial sulfur reduction activities are sources of H2S in colon cancer microenvironment, in addition to using CBS -/+ mice, we also investigated the roles of reducing H2S through adopting a sulfur amino acid restriction diet (SARD) (0.15% methionine and 0% cystine) on immunotherapy (anti-PD-L1) of colon cancer. Tumor bulk sequencing was performed in cecum orthotopic CT26 tumors collected from IgG and anti-PD-L1 treated mice both receiving normal diet and SARD.
Project description:Microbiota dysbiosis and mucosa-associated bacteria are involved in colorectal cancer progression. We hypothesized that a time-specific interaction between dysbiotic pathobionts and host responses promote tumor growth. This study aimed to elucidate the dysfunctional host-microbe interplay in colon tumorigenesis by using a time-series metagenomics approach. A transient surge in fecal microbial richness was linked to a unique transcriptome profile in the mouse colon during carcinoma transformation. Monitoring gut microbiome may help identifying the window-of-opportunity to induce tumor regression using bacteria-targeted precision medicine.
Project description:Microbiota dysbiosis and mucosa-associated bacteria are involved in colorectal cancer progression. We hypothesized that a time-specific interaction between dysbiotic pathobionts and host responses promote tumor growth. This study aimed to elucidate the dysfunctional host-microbe interplay in colon tumorigenesis by using a time-series metagenomics approach. A transient surge in fecal microbial richness was linked to a unique transcriptome profile in the mouse colon during carcinoma transformation. Monitoring gut microbiome may help identifying the window-of-opportunity to induce tumor regression using bacteria-targeted precision medicine.
Project description:The gut microbiota influences both local and systemic inflammation. Inflammation contributes to development, progression and treatment of cancer, but it remains unclear whether commensal bacteria affect inflammation in the sterile tumor microenvironment. Here we show that disruption of the microbiota impairs the response of subcutaneous tumors to CpG-oligonucleotide immunotherapy and platinum chemotherapy. In antibiotic-treated or germ-free mice, tumor-infiltrating myeloid-derived cells responded poorly to therapy, resulting in lower cytokine production and tumor necrosis after CpG-oligonucleotide treatment, and deficient production of reactive oxygen species and cytotoxicity following chemotherapy. Thus, optimal responses to cancer therapy require an intact commensal microbiota that mediates its effects by modulating myeloid-derived cell functions in the tumor microenvironment. These findings underscore the importance of the microbiota in the outcome of disease treatment. Oxaliplatin treatment induces expression of pro-inflammatory genes, which are inhibited by antibiotic pretreatment. Our goal was to ascertain the effect of antibiotic on the tumor gene expression profile prior to treatment and early on after the treatment with chemotherapy (oxaliplatin). The time points were selected t
Project description:In the past, animal experiments with rats, by depleting various amino acids in the diet, have shown that a deficiency of methionine inhibits tumor growth at the individual level and that methionine is important in the development and progression of cancer. This methionine is one of the essential amino acids and is the initiation codon that initiates protein translation from mRNA. Methionine is known to be converted to SAM, which is required for nucleic acid synthesis in cancer. Tumors are underdeveloped in an environment deficient in methionine, which is known as the "Hoffman effect". In fact, past reports have shown that in the absence of methionine, tumor growth is suppressed, and methionine has recently been shown to be essential in cancer stem cells or "tumor initiating cells". In addition, the focus on methionine in cancer is said to influence tumor-cell metabolism, histone patterns, and T cell immunity in the cancer microenvironment. In cancer immunity, not only methionine but also its upstream pathways are said to be involved. Tryptophan/niacin, which is located upstream of the methionine cycle, is metabolized to form nicotinamide, and MNAM is formed from the SAM and nicotinamide via nicotinamide N-methyltransferase (NNMT). NNMT and MNAM have been reported to participate in the mechanism of inhibition of the apoptosis signal-regulated kinase 1-p38 MAPK pathway, resulting in increased colon cancer cell resistance to 5-FU. NNMTs promote nicotinamide adenine dinucleotide depletion and epigenetic reprogramming, which have been implicated in the development of metabolic plasticity, circumvention of the major tumor suppressive process of cellular senescence, acquisition of stem cell properties, and resistance to therapy and poor clinical outcomes. Also, MNAM synthesized in this methionine cycle is said to suppress T cells and promote cancer. Hence, we implanted the colon cancer cell line HT-29 cultured in normal medium with all nutrients into NOD SCID mice and kept them for 2 weeks on a diet without the aforementioned methionine/tryptophan/niacin. Afterwards, tumors were removed and RNA-sequencing was performed, and a marked increase in the expression of RN7SL1, a non-coding RNA, was observed.