bims-instec 2021-10-03 papers

Biology (Basel). 2021 Aug 31. pii: 854. [Epub ahead of print]10(9):

Recent Updates on Mechanisms of Resistance to 5-Fluorouracil and Reversal Strategies in Colon Cancer Treatment.

Shamin Azwar, Heng Fong Seow, Maha Abdullah, Mohd Faisal Jabar, Norhafizah Mohtarrudin.

5-Fluorouracil (5-FU) plus leucovorin (LV) remain as the mainstay standard adjuvant chemotherapy treatment for early stage colon cancer, and the preferred first-line option for metastatic colon cancer patients in combination with oxaliplatin in FOLFOX, or irinotecan in FOLFIRI regimens. Despite treatment success to a certain extent, the incidence of chemotherapy failure attributed to chemotherapy resistance is still reported in many patients. This resistance, which can be defined by tumor tolerance against chemotherapy, either intrinsic or acquired, is primarily driven by the dysregulation of various components in distinct pathways. In recent years, it has been established that the incidence of 5-FU resistance, akin to multidrug resistance, can be attributed to the alterations in drug transport, evasion of apoptosis, changes in the cell cycle and DNA-damage repair machinery, regulation of autophagy, epithelial-to-mesenchymal transition, cancer stem cell involvement, tumor microenvironment interactions, miRNA dysregulations, epigenetic alterations, as well as redox imbalances. Certain resistance mechanisms that are 5-FU-specific have also been ascertained to include the upregulation of thymidylate synthase, dihydropyrimidine dehydrogenase, methylenetetrahydrofolate reductase, and the downregulation of thymidine phosphorylase. Indeed, the successful modulation of these mechanisms have been the game plan of numerous studies that had employed small molecule inhibitors, plant-based small molecules, and non-coding RNA regulators to effectively reverse 5-FU resistance in colon cancer cells. It is hoped that these studies would provide fundamental knowledge to further our understanding prior developing novel drugs in the near future that would synergistically work with 5-FU to potentiate its antitumor effects and improve the patient's overall survival.

Keywords: 5-FU; 5-fluorouracil; chemotherapy drug resistance; colon cancer; dihydropyrimidine dehydrogenase; methylenetetrahydrofolate reductase; overcoming chemotherapy drug resistance; thymidine phosphorylase; thymidylate synthase

DOI: https://doi.org/10.3390/biology10090854

Cell Death Dis. 2021 Oct 01. 12(10): 897

Epithelial argininosuccinate synthetase is dispensable for intestinal regeneration and tumorigenesis.

Jonathan H M van der Meer, Ruben J de Boer, Bartolomeus J Meijer, Wouter L Smit, Jacqueline L M Vermeulen, Sander Meisner, Manon van Roest, Pim J Koelink, Evelien Dekker, Theodorus B M Hakvoort, Jan Koster, Lukas J A C Hawinkels, Jarom Heijmans, Eduard A Struijs, Marja A Boermeester, Gijs R van den Brink, Vanesa Muncan.

The epithelial signaling pathways involved in damage and regeneration, and neoplastic transformation are known to be similar. We noted upregulation of argininosuccinate synthetase (ASS1) in hyperproliferative intestinal epithelium. Since ASS1 leads to de novo synthesis of arginine, an important amino acid for the growth of intestinal epithelial cells, its upregulation can contribute to epithelial proliferation necessary to be sustained during oncogenic transformation and regeneration. Here we investigated the function of ASS1 in the gut epithelium during tissue regeneration and tumorigenesis, using intestinal epithelial conditional Ass1 knockout mice and organoids, and tissue specimens from colorectal cancer patients. We demonstrate that ASS1 is strongly expressed in the regenerating and Apc-mutated intestinal epithelium. Furthermore, we observe an arrest in amino acid flux of the urea cycle, which leads to an accumulation of intracellular arginine. However, loss of epithelial Ass1 does not lead to a reduction in proliferation or increase in apoptosis in vivo, also in mice fed an arginine-free diet. Epithelial loss of Ass1 seems to be compensated by altered arginine metabolism in other cell types and the liver.

DOI: https://doi.org/10.1038/s41419-021-04173-x

Gastroenterology. 2021 Sep 24. pii: S0016-5085(21)03547-2. [Epub ahead of print]

An enhancer-driven stem cell-like program mediated by SOX9 blocks intestinal differentiation in colorectal cancer.

Xiaoyan Liang, Gina N Duronio, Yaying Yang, Pratyusha Bala, Prajna Hebbar, Sandor Spisak, Pranshu Sahgal, Harshabad Singh, Yanxi Zhang, Yingtian Xie, Paloma Cejas, Henry W Long, Adam J Bass, Nilay S Sethi.

BACKGROUND AND AIMS: Genomic alterations that encourage stem cell activity and hinder proper maturation are central to the development of colorectal cancer (CRC). Key molecular mediators that promote these malignant properties require further elucidation to galvanize translational advances. We therefore aimed to characterize a key factor that blocks intestinal differentiation, define its transcriptional and epigenetic program, and provide preclinical evidence for therapeutic targeting in CRC.
METHODS: Intestinal tissue from transgenic mice and patients were analyzed by histopathology and immunostaining. Human CRC cells and neoplastic murine organoids were genetically manipulated for functional studies. Gene expression profiling was obtained through RNA sequencing. Histone modifications and transcription factor binding was determined by ChIP sequencing.
RESULTS: We demonstrate that SRY-box transcription factor 9 (SOX9) promotes CRC by activating a stem cell-like program that hinders intestinal differentiation. Intestinal adenomas and colorectal adenocarcinomas from mouse models and patients demonstrate ectopic and elevated expression of SOX9. Functional experiments indicate a requirement for SOX9 in human CRC cell lines and engineered neoplastic organoids. Disrupting SOX9 activity impairs primary CRC tumor growth by inducing intestinal differentiation. By binding to genome wide enhancers, SOX9 directly activates genes associated with Paneth and stem cell activity, including PROM1. SOX9 upregulates PROM1 via a WNT-responsive intronic enhancer. A pentaspan transmembrane protein, PROM1 utilizes its first intracellular domain to support stem cell signaling, at least in part through SOX9, reinforcing a PROM1-SOX9 positive feedback loop.
CONCLUSIONS: These studies establish SOX9 as a central regulator of an enhancer-driven stem cell-like program and carry important implications for developing therapeutics directed at overcoming differentiation defects in CRC.

Keywords: PROM1; SOX9; colorectal cancer; differentiation block

DOI: https://doi.org/10.1053/j.gastro.2021.09.044

Oncol Lett. 2021 Nov;22(5): 782

NDRG4 sensitizes CRC cells to 5-FU by upregulating DDIT3 expression.

Ruikai Li, Chenxiang He, Liangliang Shen, Shuai Wang, Yao Shen, Fan Feng, Jian Zhang, Jianyong Zheng.

The incidence of colorectal cancer (CRC) has remained high in recent years, and 5-fluorouracil (5-FU) is a vital chemotherapeutic agent for its treatment. Our previous study reported that N-myc downstream-regulated gene 4 (NDRG4) plays a tumor-suppressive role in CRC, but the mechanisms associated with NDRG4 and 5-FU chemosensitivity remain unclear. The results of the present study demonstrate that NDRG4 sensitized CRC cells to 5-FU by upregulating DNA damage inducible transcript 3 (DDIT3). NDRG4 inhibited the proliferation of CRC cells and the activation of PI3K/AKT and ERK signaling. Furthermore, NDRG4 promoted CRC cell apoptosis induced by 5-FU. Mechanistic analyses revealed that NDRG4 upregulated DDIT3 expression, and that the proapoptotic effect of NDRG4 under 5-FU treatment conditions was dependent on DDIT3. These findings support the biological value of the association between NDRG4, DDIT3 and 5-FU chemosensitivity in CRC, and may advance the clinical treatment of CRC in the future.

Keywords: 5-FU; CRC; DDIT3; NDRG4; apoptosis; chemosensitivity

DOI: https://doi.org/10.3892/ol.2021.13043

Oncogene. 2021 Sep 29.

Epigenetic induction of lipocalin 2 expression drives acquired resistance to 5-fluorouracil in colorectal cancer through integrin β3/SRC pathway.

Wenyi Zhang, Rulu Pan, Mei Lu, Qian Zhang, Ziqi Lin, Yuan Qin, Zhanyu Wang, Siqing Gong, Huan Lin, Shuyi Chong, Liting Lu, Wanqin Liao, Xincheng Lu.

The therapeutic efficacy of 5-fluorouracil (5-FU) is often reduced by the development of drug resistance. We observed significant upregulation of lipocalin 2 (LCN2) expression in a newly established 5-FU-resistant colorectal cancer (CRC) cell line. In this study, we demonstrated that 5-FU-treated CRC cells developed resistance through LCN2 upregulation caused by LCN2 promoter demethylation and that feedback between LCN2 and NF-κB further amplified LCN2 expression. High LCN2 expression was associated with poor prognosis in CRC patients. LCN2 attenuated the cytotoxicity of 5-FU by activating the SRC/AKT/ERK-mediated antiapoptotic program. Mechanistically, the LCN2-integrin β3 interaction enhanced integrin β3 stability, thus recruiting SRC to the cytomembrane for autoactivation, leading to downstream AKT/ERK cascade activation. Targeting LCN2 or SRC compromised the growth of CRC cells with LCN2-induced 5-FU resistance. Our findings demonstrate a novel mechanism of acquired resistance to 5-FU, suggesting that LCN2 can be used as a biomarker and/or therapeutic target for advanced CRC.

DOI: https://doi.org/10.1038/s41388-021-02029-4

Cell Stem Cell. 2021 Sep 22. pii: S1934-5909(21)00380-5. [Epub ahead of print]

SATB2 preserves colon stem cell identity and mediates ileum-colon conversion via enhancer remodeling.

Adult stem cells maintain regenerative tissue structure and function by producing tissue-specific progeny, but the factors that preserve their tissue identities are not well understood. The small and large intestines differ markedly in cell composition and function, reflecting their distinct stem cell populations. Here we show that SATB2, a colon-restricted chromatin factor, singularly preserves LGR5+ adult colonic stem cell and epithelial identity in mice and humans. Satb2 loss in adult mice leads to stable conversion of colonic stem cells into small intestine ileal-like stem cells and replacement of the colonic mucosa with one that resembles the ileum. Conversely, SATB2 confers colonic properties on the mouse ileum. Human colonic organoids also adopt ileal characteristics upon SATB2 loss. SATB2 regulates colonic identity in part by modulating enhancer binding of the intestinal transcription factors CDX2 and HNF4A. Our study uncovers a conserved core regulator of colonic stem cells able to mediate cross-tissue plasticity in mature intestines.

Keywords: SATB2, intestine regeneration, colonic mucosa, stem cell conversion, enhancer remodelingintestine

DOI: https://doi.org/10.1016/j.stem.2021.09.004