bims-instec Biomed News
on Intestinal stem cells and chemoresistance in colon cancer and intestinal regeneration
Issue of 2022‒02‒06
eleven papers selected by
Maria-Virginia Giolito

  1. Anticancer Res. 2022 Feb;42(2): 837-844
      BACKGROUND/AIM: Chemotherapy is used for recurrent and metastatic colorectal cancer, but the response rate of 5-fluorouracil (5-FU), the standard treatment for colorectal cancer, is low. We hypothesized that thymidine phosphorylase (TYMP) expression, a rate-limiting activating enzyme of 5-FU, is regulated by methylation of the gene promoter region, and demethylation of TYMP would increase sensitivity to 5-FU.MATERIALS AND METHODS: HCT116 colon cancer cells were treated with 5-aza-2'-deoxycytidine, a demethylating agent, and changes in TYMP transcription and sensitivity to 5-FU were evaluated.
    RESULTS: TYMP expression increased over 54-fold in HCT116 transfected with TYMP. The cytotoxicity of 5-FU increased up to 5.5-fold. In comparison, in HCT116 treated with 5-aza-2'-deoxycytidine, TYMP expression increased 5.8-fold. However, the cytotoxicity of 5-FU remained unchanged.
    CONCLUSION: Demethylating agent alone did not promote the cytotoxicity of 5-FU against colorectal cancer. To further increase the sensitivity to 5-FU, combination with adjuvant therapy focusing on metabolic pathways other than the TYMP pathway appear necessary.
    Keywords:  5-fluorouracil; Colorectal cancer; inhibitor of methylation; thymidine phosphorylase
  2. Cancer Prev Res (Phila). 2022 Feb 04. pii: canprevres.0572.2021. [Epub ahead of print]
      The mechanisms underlying the regulation of a checkpoint receptor, PD-1, in tumor-infiltrating immune cells during the development of colorectal cancer (CRC) are not fully understood. Here we demonstrate that COX-2-derived PGE2, an inflammatory mediator and tumor promoter, induces PD-1 expression by enhancing NF-κB's binding to the PD-1 promoter via an EP4-PI3K-Akt signaling pathway in both CD8+ T cells and macrophages. Moreover, PGE2 suppresses CD8+ T cell proliferation and cytotoxicity against tumor cells and impairs macrophage phagocytosis of cancer cells via an EP4-PI3K-Akt-NF-κB-PD-1 signaling pathway. In contrast, inhibiting the COX-2-PGE2-EP4 pathway increases intestinal CD8+ T cell activation and proliferation and enhances intestinal macrophage phagocytosis of carcinoma cells accompanied by reduction of PD-1 expression in intestinal CD8+ T cells and macrophages in ApcMin/+ mice. PD-1 expression correlates well with COX-2 levels in human CRC specimens. Both elevated PD-1 and COX-2 are associated with poorer overall survival in colorectal cancer patients. Our results uncover a novel role of PGE2 in tumor immune evasion. They may provide the rationale for developing new therapeutic approaches to subvert this process by targeting immune checkpoint pathways using EP4 antagonists. In addition, our findings reveal a novel mechanism explaining how NSAIDs reduce colorectal cancer risk by suppressing tumor immune evasion.
  3. Nat Commun. 2022 Feb 03. 13(1): 674
      Conductin/axin2 is a scaffold protein negatively regulating the pro-proliferative Wnt/β-catenin signaling pathway. Accumulation of scaffold proteins in condensates frequently increases their activity, but whether condensation contributes to Wnt pathway inhibition by conductin remains unclear. Here, we show that the Gαi2 subunit of trimeric G-proteins induces conductin condensation by targeting a polymerization-inhibiting aggregon in its RGS domain, thereby promoting conductin-mediated β-catenin degradation. Consistently, transient Gαi2 expression inhibited, whereas knockdown activated Wnt signaling via conductin. Colorectal cancers appear to evade Gαi2-induced Wnt pathway suppression by decreased Gαi2 expression and inactivating mutations, associated with shorter patient survival. Notably, the Gαi2-activating drug guanabenz inhibited Wnt signaling via conductin, consequently reducing colorectal cancer growth in vitro and in mouse models. In summary, we demonstrate Wnt pathway inhibition via Gαi2-triggered conductin condensation, suggesting a tumor suppressor function for Gαi2 in colorectal cancer, and pointing to the FDA-approved drug guanabenz for targeted cancer therapy.
  4. Nat Protoc. 2022 Feb 02.
      Intestinal organoids are fundamental in vitro tools that have enabled new research opportunities in intestinal stem cell research. Organoids can also be transplanted in vivo, which enables them to probe stem cell potential and be used for disease modeling and as a preclinical tool in regenerative medicine. Here we describe in detail how to orthotopically transplant epithelial organoids into the colon of recipient mice. In this assay, epithelial injury is initiated at the distal part of colon by the administration of dextran sulfate sodium, and organoids are infused into the luminal space via the anus. The infused organoids subsequently attach to the injured region and rebuild a donor-derived epithelium. The steps for cell infusion can be completed in 10 min. The assay has been applied successfully to organoids derived from both wild-type and genetically altered epithelial cells from adult colonic and small intestinal epithelium, as well as fetal small intestine. This is a versatile protocol, providing the technical basis for transplantation following alternative colonic injury models. It has been used previously for functional assays to probe cellular potential, and formed the basis for the first in-human clinical trial using colonic organoid transplantation therapy for intractable cases of ulcerative colitis.
  5. Proc Natl Acad Sci U S A. 2022 Feb 08. pii: e2111711119. [Epub ahead of print]119(6):
      Stem cells constantly divide and differentiate to maintain adult tissue homeostasis, and uncontrolled stem cell proliferation leads to severe diseases such as cancer. How stem cell proliferation is precisely controlled remains poorly understood. Here, from an RNA interference (RNAi) screen in adult Drosophila intestinal stem cells (ISCs), we identify a factor, Yun, required for proliferation of normal and transformed ISCs. Yun is mainly expressed in progenitors; our genetic and biochemical evidence suggest that it acts as a scaffold to stabilize the Prohibitin (PHB) complex previously implicated in various cellular and developmental processes and diseases. We demonstrate that the Yun/PHB complex is regulated by and acts downstream of EGFR/MAPK signaling. Importantly, the Yun/PHB complex interacts with and positively affects the levels of the transcription factor E2F1 to regulate ISC proliferation. In addition, we find that the role of the PHB complex in cell proliferation is evolutionarily conserved. Thus, our study uncovers a Yun/PHB-E2F1 regulatory axis in stem cell proliferation.
    Keywords:  Drosophila; E2F1; Prohibitin; Yun; intestinal stem cell
  6. Transl Cancer Res. 2020 Sep;9(9): 5614-5625
      Background: The expression of ubiquitin-conjugating enzyme E2 M (UBE2M) is elevated in colorectal carcinoma (CRC). However, the underlying mechanisms and effects of UBE2M on the prognosis and drug resistance in CRC have not been investigated.Methods: CRC specimens and adjacent normal tissues were collected from 74 patients. The expression of UBE2M was measured by quantitative real-time polymerase chain reaction (PCR) and immunohistochemistry. Multivariable cox regression analysis was used to analyze the risk factors for overall survival in clinical CRC patients. Human colorectal cancer cell lines HCT116 and SW480 were transfected with specific UBE2M small interfering ribonucleic acid (siRNA) or plasmid to either suppress or increase the expression of UBE2M for in vitro experiments. Also, chemotherapy-resistant HCT116 and SW480 cells were established by being treated with increasingly higher concentrations of fluorouracil (5-FU) or oxaliplatin. XAV-939 was used as a wingless/integrated-beta-catenin (Wnt/β-catenin) signaling inhibitor.
    Results: According to quantitative real-time PCR and immunohistochemistry, the expression of UBE2M was elevated in CRC tissues compared to normal tissues. Based on cox regression analysis, the overexpression of UBE2M was a risk factor for overall survival of CRC patients. The expression of UBE2M was notably high in 5-FU- and oxaliplatin-resistant cells in in vitro experiments. Also, cells transfected with specific UBE2M siRNA or plasmid induced lower resistance to 5-FU and higher resistance to oxaliplatin. Finally, the expression of β-catenin was correlated with the expression of UBE2M in transfected cells and treatment with XAV939 decreased the degree of drug resistance in chemotherapy-resistant HCT116 cells.
    Conclusions: Overexpression of UBE2M in CRC specimens contributes to a decreased overall survival of patients and mediates 5-FU and oxaliplatin resistance in CRC cells via the Wnt/β-catenin signaling pathway.
    Keywords:  Ubiquitin-conjugating enzyme E2 M (UBE2M); Wnt/β-catenin signaling; chemotherapy resistance; colorectal cancer; prognosis
  7. Ther Adv Med Oncol. 2022 ;14 17588359211070643
      Background: We investigated the mutational landscape of circulating tumor DNA (ctDNA) in predicting tumor response to first-line treatment in patients with metastatic colorectal cancer (mCRC).Methods: We included 41 patients with initially unresectable mCRC, treated with 5-fluorouracil/leucovorin/oxaliplatin (FOLFOX)/5-fluorouracil/leucovorin/irinotecan (FOLFIRI) with/without bevacizumab (Bev)/cetuximab (Cet). Blood samples were prospectively collected at two timepoints: at baseline and after four cycles of first-line treatment. Mutational status of 1086 genes were studied in ctDNA by targeted next-generation sequencing (NGS). Molecular mutational burden (MMB) was defined as mean mutation frequency among obtained mutations for each gene. To evaluate the association between molecular characteristics of cfDNA and therapeutic response better, we divided these patients into MMB-high and MMB-low group according to the median value of MMB (0.3).
    Results: Among the 41 enrolled patients, alterations of six genes (TRIM24, SPEN, RNF43, PRKAR1A, KRAS, and KDM5 C) were found at baseline. Baseline MMB of six genes was significantly lower in partial response (PR)/stable disease (SD) patients than progression disease (PD) patients (p = 0.0012). Further analysis demonstrated that genomic profiling of ctDNA from pretreatment blood samples was significantly different between PR/SD (non-PD) group and PD group. By comparing the baseline levels of KRAS MMB in the two subgroups, we found that PD cases were all MMB-high, whereas non-PD cases were mainly in MMB-low subgroup. Furthermore, patients with low-KRAS MMB had superior response rate, significantly longer progression-free survival (PFS) and longer overall survival (OS) than high-KRAS MMB group.
    Conclusions: This prospective and serial genomic profiling study revealed the utility of ctDNA in predicting clinical outcomes in mCRC patients under first-line treatment. Levels of KRAS MMB might aid in monitoring therapeutic efficacy in mCRC patients at pretreatment/after four cycles of first-line treatment.
    Keywords:  KRAS; circulating tumor DNA; metastatic colorectal cancer; molecular mutational burden; prognosis
  8. Front Oncol. 2021 ;11 801319
      Colorectal cancer (CRC) is the third prevalent cancer worldwide, the morbidity and mortality of which have been increasing in recent years. As molecular targeting agents, anti-epidermal growth factor receptor (EGFR) monoclonal antibodies (McAbs) have significantly increased the progression-free survival (PFS) and overall survival (OS) of metastatic CRC (mCRC) patients. Nevertheless, most patients are eventually resistant to anti-EGFR McAbs. With the intensive study of the mechanism of anti-EGFR drug resistance, a variety of biomarkers and pathways have been found to participate in CRC resistance to anti-EGFR therapy. More and more studies have implicated non-coding RNAs (ncRNAs) primarily including microRNAs (miRNAs), long non-coding RNAs (lncRNAs), and circular RNAs (circRNAs), are widely involved in tumorigenesis and tumor progression. They function as essential regulators controlling the expression and function of oncogenes. Increasing data have shown ncRNAs affect the resistance of molecular targeted drugs in CRC including anti-EGFR McAbs. In this paper, we have reviewed the advance in mechanisms of ncRNAs in regulating anti-EGFR McAbs therapy resistance in CRC. It provides insight into exploring ncRNAs as new molecular targets and prognostic markers for CRC.
    Keywords:  CRC; EGFR; circRNA; drug resistance; lncRNA; miRNA
  9. Cancer Discov. 2022 Feb 04.
      Single cells demonstrate additional driver alterations along with initial EGFR mutations to drive resistance.
  10. Transl Cancer Res. 2020 Sep;9(9): 5595-5602
      Background: Upregulated ribosome synthesis is associated with an increased risk of cancer onset. However, the role of biogenesis of ribosomes BRX1 (BRIX1), which is involved in the synthesis of ribosomal 60S subunits, in the progression and prognosis of colorectal cancer (CRC) is not clear.Methods: Sixty CRC patients requiring surgical treatment were enrolled in the present prospective study. Patient characteristics were collected at admission. The CRC tissue samples and adjacent normal tissue samples from patients were collected for further quantitative reverse transcription-polymerase chain reaction and Western blot. All enrolled patients were followed up for 12 months, and overall patient survival during follow-up was recorded.
    Results: The level of BRIX1 mRNA in CRC tissues was higher compared with that in adjacent normal tissues (1.0±0.5 vs. 5.5±1.7, P<0.01). Similarly, the level of the BRIX1 protein in CRC tissues was significantly higher than that in adjacent normal tissues (1.0±0.6 vs. 6.4±2.1, P<0.01). On further analysis, we found that the levels of BRIX1 mRNA and protein were positively correlated with tumor stage. Patients at stages III-IV had a higher expression of BRIX1 mRNA and protein than at stages I-II. The Kaplan-Meier survival curve indicated that patients with higher level of the BRIX1 protein had a lower overall survival rate. The Cox proportional hazards model was used to identify tumor stage III or IV, poor differentiation, and elevated expression of the BRIX1 protein as risk factors for the overall survival of CRC patients.
    Conclusions: BRIX1 expression is positively correlated with CRC tumor stage; it also acts as a risk factor for the overall survival of CRC patients.
    Keywords:  BRIX1 expression is positively correlated with CRC tumor stage; it also acts as a risk factor for the overall survival of CRC patients