No abstract

SummaryLysine (Lys) is the first limiting essential amino acid in rice, a stable food for half of the world population. Efforts, including genetic engineering, have not achieved a desirable level of Lys in rice. Here, we genetically engineered rice to increase Lys levels by expressing bacterial lysine feedback-insensitive aspartate kinase (AK) and dihydrodipicolinate synthase (DHPS) to enhance Lys biosynthesis; through RNA interference of rice lysine ketoglutaric acid reductase/saccharopine dehydropine dehydrogenase (LKR/SDH) to down-regulate its catabolism; and by combined expression of AK and DHPS and interference of LKR/SDH to achieve both metabolic effects. In these transgenic plants, free Lys levels increased up to~12-fold in leaves and~60-fold in seeds, substantially greater than the 2.5-fold increase in transgenic rice seeds reported by the only previous related study. To better understand the metabolic regulation of Lys accumulation in rice, metabolomic methods were employed to analyse the changes in metabolites of the Lys biosynthesis and catabolism pathways in leaves and seeds at different stages. Free Lys accumulation was mainly regulated by its biosynthesis in leaves and to a greater extent by catabolism in seeds. The transgenic plants did not show observable changes in plant growth and seed germination nor large changes in levels of asparagine (Asn) and glutamine (Gln) in leaves, which are the major amino acids transported into seeds. Although Lys was highly accumulated in leaves of certain transgenic lines, a corresponding higher Lys accumulation was not observed in seeds, suggesting that free Lys transport from leaves into seeds did not occur.

531 Background: Our in-house meta-analysis of fecal shotgun metagenomic sequences from colorectal cancer (CRC) and control subjects from four cohorts of various ethnicities identified a higher abundance of Parvimonas micra in CRC. We aimed to investigate the effect of P. micra in colon tumor formation and development. Methods: We collected 309 fecal samples and 259 colon biopsies from patients with CRC, advanced adenoma and healthy subjects. P. micra strain was isolated from the feces of a CRC patient. APC min/+ mice and germ-free (GF) mice were orally gavaged with P. micra, or Esherichia coli. Colon epithelial cell line NCM460 and cancer cell lines HT-29 and Caco-2 were exposed to P. micra or E. coli conditional medium. Results: P. micra was significantly enriched both in the feces (n = 207, p < 0.01) and tissue biopsies (n = 99, p < 0.01) of CRC patients compared with controls (n = 102 for fecal samples, n = 160 for tissues biopsies). APCmin/+ mice gavaged with P. micra exibited significantly higher tumor burden ( p < 0.01) and tumor load ( p < 0.01), compared to mice gavaged with either E. coli or non-bacterial control. Consistently, cell proliferation was significantly higher in the colon tissues of P. micra gavaged GF mice relative to control mice evidenced by increased Ki-67 positive cells ( p < 0.05) and PCNA protein expression ( p < 0.01) at weeks 20 and 32. In line with this, colon cell lines NCM460, HT-29 and Caco-2 exposed to P. micra conditional medium significantly increased proliferation than control group (all p < 0.05). Flow cytometry analyses showed that Th2 and Th17 cells were markedly increased, while Th1 were reduced in the lamina propria of the colon tissues of P. micra gavaged mice compared to control mice (all p < 0.01) . Consistently, P. micra colonization in GF mice was associated with increased expression of pro-inflammatory cytokines, including TNF-α, IL-6 and IL-12 (all p < 0.01). Conclusions: The abundance of P. micra was significantly increased in the feces and tissue biopsies of CRC patients. P. micra promotes intestinal carcinogenesis in APC min/+ mice and increase cell proliferation in GF mice. The tumor promoting effect of P. micra is associated with altered immune responses and enhanced inflammation in the gut.

Oncogene-induced hyper-proliferation in cancer cells is accompanied by the onset of different stresses, including DNA-replication stress, metabolic stress and oxidative stress. Excessive accumulation of reactive oxygen species (ROS) plays a pivotal and contradictory role in tumor progression. ROS dictates a multitude of cell signaling pathways to facilitate the malignant transformation of tumor cells. In the meantime, oxidative burden in tumor cells mandates reinforcing antioxidant capacity to mitigate detrimental damages. The addiction to oxidative stress and increased iron demands in cancer cells also impinges on the sensitivity of ferroptosis. Targeting redox homeostasis and ferroptosis to overcome drug resistance in cancer treatment has become an attractive research topic. However, the roles of oncogenic signaling in redox regulation and ferroptosis have not been comprehensively discussed. In this review, we summarize current knowledge regarding the interplay between redox regulation and ferroptosis in the context of cancer biology. We emphasize the implication of oncogenic signaling in redox homeostasis and ferroptosis regulation. We also provide an overview of strategies targeting oxidative stress and ferroptosis in cancer treatment.

BackgroundInsulin-like growth factor binding protein-3 (IGFBP-3) is a multifunctional molecule which is closely related to cell growth, apoptosis, angiogenesis, metabolism and senescence. It combines with insulin-like growth factor-I (IGF-I) to form a complex (IGF-I/IGFBP-3) that can treat growth hormone insensitivity syndrome (GHIS) and reduce insulin requirement in patients with diabetes. IGFBP-3 alone has been shown to have anti-proliferation effect on numerous cancer cells.Methodology/Principal FindingsWe reported here an expression method to produce functional recombinant human IGFBP-3 (rhIGFBP-3) in transgenic rice grains. Protein sorting sequences, signal peptide and endoplasmic reticulum retention tetrapeptide (KDEL) were included in constructs for enhancing rhIGFBP-3 expression. Western blot analysis showed that only the constructs with signal peptide were successfully expressed in transgenic rice grains. Both rhIGFBP-3 proteins, with or without KDEL sorting sequence inhibited the growth of MCF-7 human breast cancer cells (65.76 ± 1.72% vs 45.00 ± 0.86%, p < 0.05; 50.84 ± 1.97% vs 45.00 ± 0.86%, p < 0.01 respectively) and HT-29 colon cancer cells (65.14 ±3.84% vs 18.01 ± 13.81%, p < 0.05 and 54.7 ± 9.44% vs 18.01 ± 13.81%, p < 0.05 respectively) when compared with wild type rice.Conclusion/SignificanceThese findings demonstrated the feasibility of producing biological active rhIGFBP-3 in rice using a transgenic approach, which will definitely encourage more research on the therapeutic use of hIGFBP-3 in future.