Role of pyruvate kinase M2 in transcriptional regulation leading to epithelial-mesenchymal transition.

Pyruvate kinase M2 (PKM2) is an alternatively spliced variant of the pyruvate kinase gene that is preferentially expressed during embryonic development and in cancer cells. PKM2 alters the final rate-limiting step of glycolysis, resulting in the cancer-specific Warburg effect (also referred to as aerobic glycolysis). Although previous reports suggest that PKM2 functions in nonmetabolic transcriptional regulation, its significance in cancer biology remains elusive. Here we report that stimulation of epithelial-mesenchymal transition (EMT) results in the nuclear translocation of PKM2 in colon cancer cells, which is pivotal in promoting EMT. Immunoprecipitation and LC-electrospray ionized TOF MS analyses revealed that EMT stimulation causes direct interaction of PKM2 in the nucleus with TGF-ß-induced factor homeobox 2 (TGIF2), a transcriptional cofactor repressor of TGF-ß signaling. The binding of PKM2 with TGIF2 recruits histone deacetylase 3 to the E-cadherin promoter sequence, with subsequent deacetylation of histone H3 and suppression of E-cadherin transcription. This previously unidentified finding of the molecular interaction of PKM2 in the nucleus sheds light on the significance of PKM2 expression in cancer cells.

Cancer stem cells of the digestive system.

Stem cells of the digestive system are ideal in many ways for research, given they are abundant, highly proliferative and have a uniform structural arrangement. This in turn has enormously aided the research of cancer stem cells of the digestive system, which is now shaping our understanding of cancer stem cells. In this review, the recent advances in the understanding of cancer stem cells of the digestive system have been summarized, including aspects such as their identification, origin, cell-cycle dormancy, relationship with epithelial-mesenchymal transition, cellular metabolism and the underlying molecular mechanisms. Newly acquired knowledge concerning cancer stem cells have led to the development of novel cancer therapeutics with provisional yet encouraging results.

The anti-tumor effect of trifluridine via induction of aberrant mitosis is unaffected by mutations modulating p53 activity.

The fluorinated thymidine analog trifluridine (FTD) is a chemotherapeutic drug commonly used to treat cancer; however, the mechanism by which FTD induces cytotoxicity is not fully understood. In addition, the effect of gain-of-function (GOF) missense mutations of the TP53 gene (encoding p53), which promote cancer progression and chemotherapeutic drug resistance, on the chemotherapeutic efficacy of FTD is unclear. Here, we revealed the mechanisms by which FTD-induced aberrant mitosis and contributed to cytotoxicity in both p53-null and p53-GOF missense mutant cells. In p53-null mutant cells, FTD-induced DNA double-stranded breaks, single-stranded DNA accumulation, and the associated DNA damage responses during the G2 phase. Nevertheless, FTD-induced DNA damage and the related responses were not sufficient to trigger strict G2/M checkpoint arrest. Thus, these features were carried over into mitosis, resulting in chromosome breaks and bridges, and subsequent cytokinesis failure. Improper mitotic exit eventually led to cell apoptosis, caused by the accumulation of extensive DNA damage and the presence of micronuclei encapsulated in the disrupted nuclear envelope. Upon FTD treatment, the behavior of the p53-GOF-missense mutant, isogenic cell lines, generated by CRISPR/Cas9 genome editing, was similar to that of p53-null mutant cells. Thus, our data suggest that FTD treatment overrode the effect on gene expression induced by p53-GOF mutants and exerted its anti-tumor activity in a manner that was independent of the p53 function.

Efficacy of Combination Chemotherapy Using a Novel Oral Chemotherapeutic Agent, FTD/TPI, with Ramucirumab Murine Version DC101 in a Mouse Syngeneic Cancer Transplantation Model.

Trifluridine/tipiracil (FTD/TPI) (a.k.a. TAS-102) is a combination drug for metastatic colorectal cancer (CRC) and severely pretreated metastatic gastric/gastroesophageal junction (GEJ) cancers, comprising FTD, a thymidine-based antineoplastic nucleoside analog, and TPI, which enhances FTD bioavailability. Herein, in KRAS mutant murine colorectal cancer CT26 syngeneic models, we investigate whether combination therapy with DC101 (a surrogate ramucirumab antibody, rat antimouse vascular endothelial growth factor receptor (VEGFR)-2 monoclonal antibody (mAb)) improves FTD/TPI efficacy. Tumor growth inhibition (TGI) on day 15 was 38.0% and 30.6% upon DC101 monotherapy and FTD/TPI monotherapy respectively, and 60.3% upon combination therapy. Tumor volume was significantly lower (p < 0.001) upon combination treatment than upon FTD/TPI or DC101 monotherapy, indicating the additive effects of FTD/TPI and DC101. DNA-incorporated FTD levels on Day 8 were significantly higher in combination therapy with FTD/TPI (for 5 consecutive days) and DC101 (on alternate days for 7days) than in FTD/TPI monotherapy. Furthermore, vascular endothelial cell-specific marker CD31 was downregulated in DC101-treated tumors on day 8. These results indicate that combination therapy with FTD/TPI and DC101 is a promising treatment alternative regardless of KRAS mutations.

Potential synergistic effects of novel hematopoietic prostaglandin D synthase inhibitor TAS-205 and different types of anti-allergic medicine on nasal obstruction in a Guinea pig model of experimental allergic rhinitis.

Nasal obstruction is one of the most bothersome symptoms of allergic rhinitis (AR) affecting sleep-related quality of life in AR patients. Although several treatments were tested to control nasal obstruction, some patients with moderate to severe AR do not respond to current treatments, including the combined administration of different types of anti-allergic medicine. Thus, new options for AR treatment are needed. This study aimed to evaluate the effects of combined treatment with a novel inhibitor of hematopoietic prostaglandin D synthase (HPGDS), TAS-205, and different types of anti-allergic medicine on nasal obstruction in AR. Firstly, we demonstrated that TAS-205 selectively inhibited prostaglandin D2 (PGD2) synthesis in an enzymatic assay in a cell-based assay and in vivo models of AR. Moreover, treatment with TAS-205 alone suppressed eosinophil infiltration into the nasal cavity and late phase nasal obstruction. The combined administration of TAS-205 with montelukast, a cysteinyl leukotriene receptor 1 antagonist, showed significant additive inhibitory effects on eosinophil infiltration and late phase nasal obstruction compared to treatment with each agent alone. In contrast, concomitant treatment with TAS-205 and fexofenadine, a histamine H1 blocker, showed inhibitory effects on late phase and early phase nasal obstruction, although the magnitude of the inhibitory effects upon combined administration was comparable to that of each single treatment. These results suggest that combined treatment with an HPGDS inhibitor and different types of anti-allergic medicine may be a promising strategy to control nasal obstruction in AR patients.

Theoretical analyses and experimental validation of the effects caused by the fluorinated substituent modification of DNA.

Halogen-modified nucleic acid molecules, such as trifluorothymidine (FTD) and 5-fluorouracil, are widely used in medical science and clinical site. These compounds have a very similar nucleobase structure. It is reported that both of these compounds could be incorporated into DNA. The incorporation of FTD produces highly anti-tumor effect. However, it is not known whether to occur a significant effect by the incorporation of 5-fluorouracil. Nobody knows why such a difference will occur. To understand the reason why there is large differences between trifluorothymidine and 5-fluorouracil, we have performed the molecular dynamics simulations and molecular orbital calculations. Although the active interaction energy between Halogen-modified nucleic acids or and complementary adenine was increased, in only FTD incorporated DNA, more strongly dispersion force interactions with an adjacent base were detected in many thermodynamic DNA conformations. As the results, the conformational changes occur even if it is in internal body temperature. Then the break of hydrogen bonding between FTD and complementary adenine base occur more frequently. The double helix structural destabilization of DNA with FTD is resulted from autoagglutination caused by the bonding via halogen orbitals such as halogen bonding and the general van der Waals interactions such as CH-[Formula: see text], lone pair (LP)-[Formula: see text], and [Formula: see text]-[Formula: see text] interactions. Therefore, it is strongly speculated that such structural changes caused by trifluoromethyl group is important for the anti-tumor effect of FTD alone.

CD44/CD133-Positive Colorectal Cancer Stem Cells are Sensitive to Trifluridine Exposure.

Cancer stem cells (CSCs) are involved in metastatic colorectal cancer recurrence, but no effective therapy targeting these cells is currently available. Because trifluridine (FTD)/tipiracil therapy is used for refractory colorectal cancer, we sought to determine whether FTD is effective against CSC-like cells. CD44+CD133+ high-expressing and other populations of human DLD-1 colon cancer cells were separately isolated through fluorescence-activated cell sorting. The sphere-forming activity of each population and the anti-sphere-forming effects of FTD and fluorouracil (5-FU) on CD44+CD133+ cells were then measured. CD44+CD133+ DLD-1 cells formed substantially more spheres than other cells. Moreover, treating CD44+CD133+ DLD-1 cells with subtoxic concentrations of FTD (1 µM) inhibited sphere formation, and this was superior to the effect of subtoxic concentrations (1 µM) of 5-FU. The associated inhibition rates for FTD and 5-FU were 58.2% and 26.1%, respectively. Further, CD44+CD133+ DLD-1 cells expressed higher levels of thymidine kinase 1, which is responsible for FTD phosphorylation, than DLD-1 cells, and FTD was incorporated into the DNA of CD44+CD133+ DLD-1 cells. Thus, our data show that FTD treatment is effective against CSC-like cells and might be applied as CSC-targeting chemotherapy for tumor subtypes with high CD44 and CD133 expression.

MicroRNA profiles involved in trifluridine resistance.

Trifluridine (FTD) is a key component of the novel oral antitumor drug trifluridine/tipiracil, which is approved for the treatment of patients with metastatic colorectal cancer refractory to standard chemotherapies. A microRNA analysis of three colorectal cell lines was conducted to investigate causes of FTD resistance. Drug resistant sublines of DLD-1, HCT-116, and RKO cells were developed by continuous administration of increasing doses of FTD for 5 months. The let-7d-5p gene, which maps to chromosome 9q22.32, was downregulated in the FTD-resistant DLD-1 sublines. DLD-1 cells became more resistant to FTD when let-7d-5p was knocked down and more sensitive when let-7d-5p was overexpressed. The FTD-resistant sublines were not cross-resistant to 5-fluorouracil (5-FU); 5-FU sensitivity was affected only slightly when let-7d-5p as overexpressed or knocked down. These data indicate that let-7d-5p increases sensitivity of FTD but not 5-FU and that let-7d-5p is a potential clinical marker of treatment sensitivity.

The importance of mitochondrial folate enzymes in human colorectal cancer.

Folate plays a pivotal role in the one-carbon metabolism needed for methylation reactions, nucleotide synthesis, and DNA repair. Although folate metabolism was recently shown to be associated with carcinogenesis in some solid tumors, the importance of folate metabolism in colorectal cancer remains unclear. In the present investigation we found that expression of three mitochondrial folate metabolic enzymes, serine hydroxymethyl transferase (SHMT2), methylenetetrahydrofolate dehydrogenase (MTHFD2) and aldehyde dehydrogenase 1 family member L2 (ALDH1L2), were upregulated in human colorectal tumor tissues compared to normal tissues. Colorectal cancer tissue samples were obtained from 117 consecutive patients. We evaluated the expression of the enzymes with immunohistochemical analysis and determined their relevance to clinicopathological characteristics and prognosis. Rates of recurrence-free survival (RFS) and overall survival (OS) in patients with high expression of SHMT2, MTHFD2 and ALDH1L2 tended to be lower than in patients with low expression of SHMT2, MTHFD2 and ALDH1L2 (P=0.446 and P=0.337, P=0.099 and P=0.064, P=0.178 and P=0.257, respectively). Notably, the combined high expression of SHMT2, MTHFD2 and ALDH1L2 (triple high) was more highly associated with poor prognosis than the individual expression levels (RFS; P=0.004 and OS; P=0.037). A multivariate analysis showed that triple high expression was independently associated with RFS (P=0.017). These findings suggested that mitochondrial folate metabolic enzymes could provide a potential therapeutic strategy for treating colorectal cancer.

Folic Acid-Metabolizing Enzymes Regulate the Antitumor Effect of 5-Fluoro-2'-Deoxyuridine in Colorectal Cancer Cell Lines.

In colorectal cancer chemotherapy, the current standard of care includes combination therapy with 5-fluorouracil (5-FU) and leucovorin (LV). However, the factors that determine the LV-mediated enhancement of 5-FU antitumor activity are not fully understood. Therefore, we investigated the roles of thymidine synthase (TYMS), folate receptor 1 (FOLR1), dihydrofolate reductase (DHFR), phosphoribosylglycinamide formyltransferase (GART), methylenetetrahydrofolate dehydrogenase (MTHFD1), and methylenetetrahydrofolate reductase (MTHFR) in LV-mediated enhancement of 5-fluoro-2'-deoxyuridine (FdUrd) cytotoxicity in vitro as a model of 5-FU antitumor activity. These genes were downregulated in DLD-1 and HCT116 human colorectal cancer cells by using small-interfering RNA. Reduced expression of TYMS mRNA significantly increased FdUrd cytotoxicity by 100- and 8.3-fold in DLD-1 and HCT116 cells, respectively. In contrast, reducing the expression of FOLR1, DHFR, GART, MTHFD1, and MTHFR decreased FdUrd cytotoxicity by 2.13- to 12.91-fold in DLD-1 cells and by 3.52- to 10.36-fold in HCT116 cells. These results demonstrate that folate metabolism is important for the efficacy of FdUrd. Overall, the results indicate that it is important to clarify the relationship between folate metabolism-related molecules and 5-FU treatment in order to improve predictions of the effectiveness of 5-FU and LV combination therapy.

Oncometabolite D-2-Hydroxyglurate Directly Induces Epithelial-Mesenchymal Transition and is Associated with Distant Metastasis in Colorectal Cancer.

Deranged metabolism is a hallmark of cancer, playing a significant role in driving the disease process. One such example is the induction of carcinogenesis by the oncometabolite D-2 hydroxyglutarate (D-2HG), which is produced by the mutated enzyme isocitrate dehydrogenase (IDH) occurring in subsets of leukaemias and brain tumours. The oncogenic property of D-2HG appears to stem from its ability to interfere with the activities of α-ketoglutarate-dependent dioxygenases, including the Jumonji family histone demethylases. Here, we find in colorectal cancer cells that even in the absence of IDH mutation, the levels of D-2HG and its enantiomer L-2HG were elevated through glutamine anaplerosis. D-2HG, but not L-2HG, increased the trimethylation of histone H3 lysine 4 of the promoter region of ZEB1, a master regulator of epithelial-mesenchymal transition (EMT), and increased the expression of the ZEB1 gene to directly induce EMT in colorectal cancer cells. EMT promotes the ability of cancer cells to invade the local tissue and enter into the bloodstream, leading to distant organ metastasis. D-2HG levels were elevated in colorectal cancer specimens, particularly in those associated with distant metastasis, supporting the observations in vitro and implicating the contribution of D-2HG in metastasis, the major cause of death in this disease.

Mathematical analysis predicts imbalanced IDH1/2 expression associates with 2-HG-inactivating ß-oxygenation pathway in colorectal cancer.

Bioinformatics and computational modeling offer innovative approaches to investigate cancer metabolism and predict the secondary and tertiary cellular responses. Dysregulation of metabolism has also been implicated in the pathophysiology of cancer. A significant proportion of patients with glioblastoma and hematological malignancies harbor the mutated forms of the oxidative phosphorylation (OxPhos) enzymes, isocitrate dehydrogenase (IDH) 1 or 2. The mutated forms of IDH1 and IDH2 produce an oncogenic metabolite, D-2-hydroxyglutarate (D2HG). A recent study of breast cancer patients showed that D2HG can also be produced in the absence of mutated IDH, through an alternative route involving over-activated MYC signaling. We developed a novel methodology to computationally analyze gene expression in colorectal cancer (CRC), and identified novel sets of genes that are associated with patient survival. The study of OxPhos-related genes revealed that an imbalance between the expression of IDH1 and IDH2, defined as overexpression of one isoform in relation to the other, was associated with worse prognosis in CRC patients. This effect was further accentuated by reduced expression of the ß-oxygenation enzyme, 3-D-hydroxyacyl-CoA dehydratase (HCDH) 4, which has been reported to contribute to metabolism of intracellular D2HG. The present computational analysis revealed a novel and potential mechanism of CRC development, through over-production of D2HG when there is an imbalance between IDH1 and IDH2 expression, resulting in decreased clearance of D2HG when the ß-oxidization pathway is diminished. Additional validation analysis with another gene expression dataset resulted in IDH1/2 imbalanced expression with a shorter DFS compared with balanced expression. Altogether, these findings provide a strong rationale for studying this mechanism further in order to discover novel therapeutic targets for the treatment of CRC.