Hypoxia-inducible factor-1 modulates upregulation of mutT homolog-1 in colorectal cancer

Hypoxia-Targeted Immunotherapy with PD-1 Blockade in Head and Neck Cancer

Intratumoral hypoxia is associated with tumor progression, aggressiveness, and therapeutic resistance in several cancers. Hypoxia causes cancer cells to experience replication stress, thereby activating DNA damage and repair pathways. MutT homologue-1 (MTH1, also known as NUDT1), a member of the Nudix family, maintains the genomic integrity and viability of tumor cells in the hypoxic tumor microenvironment. Although hypoxia is associated with poor prognosis and can cause therapeutic resistance by regulating the microenvironment, it has not been considered a treatable target in cancer. This study aimed to investigate whether hypoxia-induced MTH1 is a useful target for immunotherapy and whether hypoxic conditions influence the antitumor activity of immune cells. Our results showed that MTH1 expression was elevated under hypoxic conditions in head and neck cancer cell lines. Furthermore, we identified a novel MTH1-targeting epitope peptide that can activate peptide-specific CD4+ helper T cells with cytotoxic activity. The proliferation and cytotoxic activity of T cells were maintained under hypoxic conditions, and PD-1 blockade further augmented the cytotoxicity. These results indicate that MTH1-targeted immunotherapy combined with checkpoint blockade can be an effective strategy for the treatment of hypoxic tumors.

Specific 8-oxo-dGTPase activity of MTH1 (NUDT1) protein as a quantitative marker and prognostic factor in human colorectal cancer

The MTH1 (NUDT1) gene, because it is frequently upregulated in many types of human cancers, has been considered a general marker of carcinogenesis for over two decades. The MTH1 protein hydrolyzes the oxidized mutagenic DNA precursor, 8-oxo-7,8-dihydro-2'-deoxyguanosine 5'-triphosphate (8-oxo-dGTP), to the corresponding 5'-monophosphate and inorganic pyrophosphate. This prevents its incorporation into DNA by DNA polymerases and protects cells from the accumulation of 8-oxo-dGTP-induced point mutations. Elevated MTH1 mRNA and protein in many types of human cancer indicate a worse prognosis. However, the enzymatic activity of MTH1 has remained largely uninvestigated in this context. Therefore, we have set out to determine the specific 8-oxo-dGTPase activity of MTH1 in 57 pairs of human colorectal cancers (CRC) and adjacent cancer-free tissues (CFCF). The goal was to ascertain the potential for measuring this enzymatic activity as a way to differentiate cancerous from non-cancerous specimens of the intestine, as well as defining its capabilities as a prognostic value for disease-free survival. We found that 79% of CRC tumors exhibited a higher MTH1 activity than did CFCF, with a significant 1.6-fold increase in overall median value (p < 1E-6). The 8-oxo-dGTPase in both tissues was proportional to the corresponding levels of MTH1 protein, as assayed by Western blotting. Activity higher than the ROC-optimized threshold (AUC = 0.71) indicated cancerous tissue, with a 54% sensitivity and an 83% specificity. Postoperative fate followed for up to 100 months showed that higher 8-oxo-dGTPase, in either the CFCF or the CRC tumor, clearly lowered the probability of a relapse-free survival, although borderline statistical significance (p < 0.05) was crossed only for the CFCF.

MutT Homolog1 has multifaceted role in glioma and is under the apparent orchestration by Hypoxia Inducible factor1 alpha

AIMS

The study focused on the expression and role of a recent potential cancer therapeutic target protein, MutT Homolog1 (MTH1). MTH1 gets activated in an increased reactive oxygen species (ROS) environment and removes the oxidized nucleotides from the cell. The study aimed to check the role of MTH1 in DNA damage and apoptosis, migration and angiogenesis and also to examine its regulation in glioma.

MAIN METHODS

The experiments were carried out in human glioma tissue samples and brain tissues of epilepsy patients (non-tumor control). We used two human glioblastomas cell lines, U87MG and U251MG cells. In order to study the role of MTH1 in glioma and to analyze the relation of MTH1 with Hif1α, we have used MTH1 siRNA and Hif1α siRNA respectively.

KEY FINDINGS

We found an increased expression of MTH1 in glioma tissues compared to the non-tumor brain tissues. Correlation analysis revealed that those samples showing reduced expression of MTH1 also had high levels of DNA damage and apoptotic markers, while diminished expression of angiogenesis regulators and levels of migration. MTH1 knockdown in vitro by siRNA in tumor cell lines corroborates the above observation. This justifies the emergence of MTH1 inhibitors as potential first-in-class drugs. Mechanistically, our observations suggest that Hif1α may modulate MTH1 expression.

SIGNIFICANCE

We found elevated MTH1 expression in glioma irrespective of their grades, while its inhibition affects multiple tumor progression pathways, and that targeting Hif1α could simulate the same.

Intestinal Epithelial Cells-Derived Hypoxia-Inducible Factor-1α Is Essential for the Homeostasis of Intestinal Intraepithelial Lymphocytes

Hif-1α is a master regulator which involved in the transcriptional regulation of anti-inflammatory or cellular responding to hypoxia. Previous work shows that the absence of Hif-1α results in the destruction of intestinal epithelial cell (IEC) and abnormalities of intestinal barrier function. However, we know very little about other functions of Hif-1α on intestinal intraepithelial lymphocyte (IEL). Therefore, we generated a transgenic mouse (Hif1-α^ΔIEC mice), which was knocked out Hif1-α specifically in IECs, to study the effect of Hif1-α on IEL. IELs were isolated from the small intestine and colon of mice, respectively, and examined by flow cytometry and quantitative real-time PCR. All the cytokines expression was detected by quantitative real-time PCR. The NSAID enteropathy was induced by gavaged with 5 mg/kg indomethacin and the experimental colitis was induced by administration of 2.5% DSS. We found that the number of IELs is increased in Hif1-α ^ΔIEC mice. It is showed that knockout of Hif1-α in IECs led to significant changes in IEL phenotype, including a marked decline in the CD8αα⁺ and TCRγδ⁺ population. The reduction of CD8αα⁺ IELs is accompanied by increased apoptosis, decreased proliferation and weakened migration in Hif1-α^ΔIEC mice. Moreover, absence of intestinal epithelial Hif1-α markedly changed the population of IELs in NSAID-induced small intestinal injury and increased susceptibility to dextran sulfate sodium-induced colitis. In summary, our results first time demonstrate that IEC-derived Hif1-α is essential for maintaining IELs homeostasis and intestinal microbiota.

Differential anti-tumour effects of MTH1 inhibitors in patient-derived 3D colorectal cancer cultures

Reactive oxygen species (ROS) function as second messengers in signal transduction, but high ROS levels can also cause cell death. MTH1 dephosphorylates oxidized nucleotides, thereby preventing their incorporation into DNA and protecting tumour cells from oxidative DNA damage. Inhibitors of MTH1 (TH588 and (S)-crizotinib) were shown to reduce cancer cell viability. However, the MTH1-dependency of the anti-cancer effects of these drugs has recently been questioned. Here, we have assessed anti-tumour effects of TH588 and (S)-crizotinib in patient-derived 3D colorectal cancer cultures. Hypoxia and reoxygenation – conditions that increase intracellular ROS levels – increased sensitivity to (S)-crizotinib, but not to TH588. (S)-crizotinib reduced tyrosine phosphorylation of c-MET and ErbB3 whereas TH588 induced a mitotic cell cycle arrest, which was not affected by adding ROS-modulating compounds. Furthermore, we show that both compounds induced DNA damage that could not be prevented by adding the ROS inhibitor N-acetyl-L-cysteine. Moreover, adding ROS-modulating compounds did not alter the reduction in viability in response to TH588 and (S)-crizotinib. We conclude that TH588 and (S)-crizotinib have very clear and distinct anti-tumour effects in 3D colorectal cancer cultures, but that these effects most likely occur through distinct and ROS-independent mechanisms.

The ADP-ribose reactive NUDIX hydrolase isoforms can modulate HIF-1α in cancer cells

The human nucleoside-diphosphate linked moiety-X (NUDIX) hydrolases that utilize ADP-ribose and NADH/NAD⁺ are overexpressed in cancer cells, but their roles in hypoxia inducible factor-1α (HIF-1α) regulation have not yet been revealed. Here, we showed that these NUDIX hydrolases negatively regulated HIF-1α accumulation by modulating the Ca²⁺ dependent AMP-activated protein kinase (AMPK) signaling pathway. In specific, knockdown of NUDT9 resulted in accumulation of free ADP-ribose that triggered Ca²⁺ influx mediated by transient receptor potential cation channel subfamily M member 2 and subsequent activation of Ca²⁺/calmodulin-dependent protein kinase kinase β (CaMKKβ). In addition, AMPK activation by CaMKKβ was shown to enhance HIF-1α accumulation. Our findings provide insights into the action of NUDIX hydrolases as an additional, discrete modulator of HIF-1α accumulation.

An insertion/deletion polymorphism within the promoter of EGLN2 is associated with susceptibility to colorectal cancer

OBJECTIVE

To investigate the association between susceptibility to colorectal cancer (CRC) and a 4-bp insertion/deletion polymorphism (rs10680577) in the proximal promoter of the EGLN2 gene.

METHOD

The first step in genotyping EGLN2 was PCR, then the PCR products were separated using 7% nondenaturing polyacrylamide gel electrophoresis and visualized by silver staining according to the final product band location and quantity to determine the genotype of the sample. The final count was done by two different pathologists.

RESULT

In the codominant model, compared with the ins/ins genotype, subjects with the heterozygous ins/del or homozygous del/del genotype had a significantly increased risk of CRC (adjusted OR = 1.45, p<0.0001 and OR = 2.44, p = 0.0001, respectively). Each additional copy of the 4-bp deletion allele conferred a significantly increased risk of CRC (OR = 1.47, 95% CI 1.28-1.66, p<0.0001). In the stratification analysis, we further proved that the association was more prominent in TNM stage III and IV cancer compared with stage I and II (adjusted OR = 1.43, 95% CI 1.07-1.93, p for heterogeneity = 0.02).

CONCLUSIONS

Our study provided initial evidence that the insertion/deletion polymorphism rs10680577 may play a functional role in the development of CRC in the Chinese population.

Knockdown of hypoxia inducible factor-2α inhibits cell invasion via the downregulation of MMP-2 expression in breast cancer cells

Hypoxia inducible factors (HIFs) are important regulatory molecules of the intracellular oxygen-signaling pathway. The role of HIF-1α has been confirmed in breast carcinoma; however, little is understood concerning the function of HIF-2α. The present study treated human breast adenocarcinoma MCF-7 cells with the HIF activator cobalt chloride, and transfected HIF-2α small interfering RNAs (siRNAs) into MCF-7 cells to suppress HIF-2α expression. The siRNAs significantly reduced the levels of HIF-2α and matrix metalloproteinase (MMP)-2 in the treated MCF-7 cells. An invasion assay demonstrated that the siRNAs targeting HIF-2α inhibited the invasion potency of the cells. The present study concludes that loss of HIF-2α may be associated with a decreased risk for the progression of human breast cancer, due to the downregulation of the expression of MMP-2.