Endothelial PAS domain-containing protein 1 confers TKI-resistance by mediating EGFR and MET pathways in non-small cell lung cancer cells

MiR-519d-3p enhances the sensitivity of non-small-cell lung cancer to tyrosine kinase inhibitors

Non-small cell lung cancer (NSCLC) is the leading cause of cancer mortality worldwide. Tyrosine kinase inhibitors (TKIs) are currently the most effective chemotherapy for NSCLC. However, most cancer patients develop TKI resistance at tumor relapse stage. We firstly measured the expression change of miR-519d-3p in TKI resistance NSCLC cells. We then ectopically expressed miR-519-3p in TKI resistant cells to study its functional impact on cell proliferation, migration, invasion and cell sensitivity to gefitinib. The downstream target of miR-519-3p was identified by bioinformatics and validated in luciferase reporter assay and western blotting analysis. We also studied the reversing effect of the candidate target in NSCLC cells expressing miR-519d-3p. Lastly, we compared the miR-519d-3p level in NSCLC patients with good or poor response to gefitinib. miR-519d-3p level was downregulated in TKI resistant NSCLC cells. The restoration of miR-519d-3p in these NSCLC cells inhibited cell proliferation, invasion and migration; enhanced cell sensitivity to gefitinib. EPAS1 was identified and validated as downstream target of miR-519d-3p. Co-expressing EPAS1 antagonized the inhibitory effect of miR-519d-3p on NSCLC cells. MiR-519d-3p was downregulated in NSCLC patients with poor response to gefitinib. Targeting miR-519d-3p/EPAS1 axis may provide alternative treatment for TKI-resistant NSCLC.

EPAS1 promotes peritoneal carcinomatosis of non-small-cell lung cancer by enhancing mesothelial-mesenchymal transition

BACKGROUND

Non-small-cell lung cancer (NSCLC) is a major cause of cancer-related death globally. Endothelial PAS domain-containing protein 1 (EPAS1) is a homolog of the hypoxia-inducible factor 1α and has been reported to confer tyrosine kinase inhibitor (TKI) resistance in NSCLC, but its role in peritoneal carcinomatosis of NSCLC is unknown.

METHODS

PC14HM, a high metastatic potential subline of NSCLC cell line PC14, was derived. Stable shRNA knockdown of EPAS1 was then established in PC14HM cells and subjected to assessment regarding the effects on proliferation and viability, xenograft tumor growth, metastatic potential, mesothelial-mesenchymal transition (MMT)-related characteristics and peritoneal carcinomatosis in a mouse model.

RESULTS

EPAS1 expression was elevated in PC14HM cells. Knockdown of EPAS1 inhibited the proliferation and viability of PC14HM cells in vitro and suppressed tumorigenesis in vivo. In addition, the metastatic features and in vitro productions of MMT-inducing factors in PC14HM cells was also associated with EPAS1. More importantly, knockdown of EPAS1 drastically suppressed peritoneal carcinomatosis of PC14HM cells in vivo.

CONCLUSION

EPAS1 promotes peritoneal carcinomatosis of NSCLC through enhancement of MMT and could therefore serve as a prognostic marker or a therapeutic target in treating NSCLC, particularly in patients with peritoneal carcinomatosis.

EPAS1 targeting by miR-152-3p in Paclitaxel-resistant Breast Cancer

Background: Paclitaxel plays a pivotal role in the chemotherapy of breast cancer, but resistance to this drug is an important obstacle in the treatment. It is reported that microRNA-152-3p (miR-152-3p) is involved in tamoxifen resistance in breast cancer, but whether it is involved in paclitaxel resistance in breast cancer remains unknown. Materials and methods: We examined the expression of miR-152-3p in breast cancer tissues and cells by qRT-PCR. After transfecting paclitaxel-resistant MCF-7/TAX cells with miR-152-3p mimics, we analyzed the function of miR-152-3p in these cells by MTT assay and flow cytometry. We screened the target gene, endothelial PAS domain-containing protein 1 (EPAS1), using bioinformatics analysis and verified it with the dual luciferase reporter gene experiment. The relationship between EPAS1 and miR-152-3p and their roles in paclitaxel resistance of breast cancer were further investigated using RNA interference and transfection techniques. Results: The expression of miR-152-3p in normal breast tissues and cells was markedly higher than that in breast cancer. Overexpression of miR-152-3p decreased the survival rate and increased the apoptosis rate and sensitivity of MCF-7/TAX cells to paclitaxel. We confirmed that EPAS1 is the target of miR-152-3p and is negatively regulated by this miRNA. Moreover, transfection with EPAS1 siRNA enhanced the susceptibility and apoptosis rate of MCF-7/TAX cells to paclitaxel. Co-transfection of miR-152-3p mimics and EPAS1 increased paclitaxel sensitivity and apoptosis induced by the drug. Conclusion: miR-152-3p inhibits the survival of MCF-7/TAX cells and promotes their apoptosis by targeting the expression of EPAS1, thereby, enhancing the sensitivity of these breast cancer cells to paclitaxel.

Constitutive or Induced HIF-2 Addiction is Involved in Resistance to Anti-EGFR Treatment and Radiation Therapy in HNSCC

BACKGROUND

management of head and neck squamous cell carcinomas (HNSCC) include anti-Epidermal Growth Factor Receptor (EGFR) antibodies and radiotherapy, but resistance emerges in most patients. RAS mutations lead to primary resistance to EGFR blockade in metastatic colorectal cancer but are infrequent in HNSCC, suggesting that other mechanisms are implicated. Since hypoxia and Hypoxia Inducible Factor-1 (HIF-1) have been associated with treatment failure and tumor progression, we hypothesized that EGFR/mammalian Target Of Rapamycin (mTOR)/HIF-1 axis inhibition could radiosensitize HNSCC.

METHODS

We treated the radiosensitive Cal27 used as control, and radioresistant SQ20B and UD-SCC1 cells, in vivo and in vitro, with rapamycin and cetuximab before irradiation and evaluated tumor progression and clonogenic survival.

RESULTS

Rapamycin and cetuximab inhibited the mTOR/HIF-1α axis, and sensitized the SQ20B cell line to EGFR-inhibition. However, concomitant delivery of radiation to SQ20B xenografts increased tumor relapse frequency, despite effective HIF-1 inhibition. Treatment failure was associated with the induction of HIF-2α expression by cetuximab and radiotherapy. Strikingly, SQ20B and UD-SCC1 cells clonogenic survival dropped <30% after HIF-2α silencing, suggesting a HIF-2-dependent mechanism of oncogenic addiction.

CONCLUSIONS

altogether, our data suggest that resistance to EGFR inhibition combined with radiotherapy in HNSCC may depend on tumor HIF-2 expression and underline the urgent need to develop novel HIF-2 targeted treatments.

Hypoxia-inducible factor-1 signaling pathway influences the sensitivity of HCC827 cells to gefitinib

The majority of patients with non-small cell lung cancer (NSCLC) with activating epidermal growth factor receptor (EGFR) mutations inevitably progress in stage despite an initial substantial and rapid response to EGFR-tyrosine kinase inhibitors (EGFR-TKIs). Previous research indicates that hypoxia may be associated with resistance to EGFR-TKIs in EGFR mutation-positive NSCLC. Therefore, the present study regulated the activity of hypoxia-inducible factor-1 (HIF-1) signaling pathway to observe if it is able to alter the sensitivity of lung cancer cells to gefitinib. The present study selected 3-(5'-hydroxymethyl-2'-furyl)-1-benzylindazole (YC-1) and dimethyloxalylglycine (DMOG) as a HIF-1 signaling pathway inhibitor and activator, respectively, on HCC827 cells. Cells were incubated with different treatments for different durations: A blank control, DMOG, gefitinib, or DMOG and gefitinib combined, for 36 and 48 h; and then a blank control, YC-1, gefitinib, or YC-1 and gefitinib combined, for 16 and 28 h. A western blot analysis assay was performed to evaluate the protein expression levels of HIF-1α and phosphorylated hepatocyte growth factor receptor (p-MET), an MTT assay was used to determine cell proliferation, a colony formation assay was used to investigate the colony-forming ability and a wound healing assay was used to test the cell migration ability. Additionally, Pearson's correlation analysis was used to evaluate the correlation between p-Met and HIF-1α expression levels. Finally, it was identified that gefitinib and DMOG combined notably improve the growth and cell migration ability of HCC827 cells, compared with gefitinib alone. When gefitinib and YC-1 were combined, the inhibiting effect on the growth and cell migration ability of HCC827 cells was substantially enhanced, compared with the control cells. Pearson's correlation analysis revealed that the p-Met expression level had a strong positive correlation with HIF-1α expression levels. Thus, it was concluded that the HIF-1 signaling pathway influences the sensitivity of HCC827 cells to gefitinib. The positive correlation between p-Met and HIF-1α expression levels may be the underlying mechanism of the HIF-1 signaling pathway influencing the sensitivity of HCC827 cells to gefitinib.

Multi-Omics Analysis Reveals a HIF Network and Hub Gene EPAS1 Associated with Lung Adenocarcinoma

Recent technological advancements have permitted high-throughput measurement of the human genome, epigenome, metabolome, transcriptome, and proteome at the population level. We hypothesized that subsets of genes identified from omic studies might have closely related biological functions and thus might interact directly at the network level. Therefore, we conducted an integrative analysis of multi-omic datasets of non-small cell lung cancer (NSCLC) to search for association patterns beyond the genome and transcriptome. A large, complex, and robust gene network containing well-known lung cancer-related genes, including EGFR and TERT, was identified from combined gene lists for lung adenocarcinoma. Members of the hypoxia-inducible factor (HIF) gene family were at the center of this network. Subsequent sequencing of network hub genes within a subset of samples from the Transdisciplinary Research in Cancer of the Lung-International Lung Cancer Consortium (TRICL-ILCCO) consortium revealed a SNP (rs12614710) in EPAS1 associated with NSCLC that reached genome-wide significance (OR = 1.50; 95% CI: 1.31-1.72; p = 7.75 × 10^-9). Using imputed data, we found that this SNP remained significant in the entire TRICL-ILCCO consortium (p = .03). Additional functional studies are warranted to better understand interrelationships among genetic polymorphisms, DNA methylation status, and EPAS1 expression.

Tumor-initiating cells of breast and prostate origin show alterations in the expression of genes related to iron metabolism

The importance of iron in the growth and progression of tumors has been widely documented. In this report, we show that tumor-initiating cells (TICs), represented by spheres derived from the MCF7 cell line, exhibit higher intracellular labile iron pool, mitochondrial iron accumulation and are more susceptible to iron chelation. TICs also show activation of the IRP/IRE system, leading to higher iron uptake and decrease in iron storage, suggesting that level of properly assembled cytosolic iron-sulfur clusters (FeS) is reduced. This finding is confirmed by lower enzymatic activity of aconitase and FeS cluster biogenesis enzymes, as well as lower levels of reduced glutathione, implying reduced FeS clusters synthesis/utilization in TICs. Importantly, we have identified specific gene signature related to iron metabolism consisting of genes regulating iron uptake, mitochondrial FeS cluster biogenesis and hypoxic response (ABCB10, ACO1, CYBRD1, EPAS1, GLRX5, HEPH, HFE, IREB2, QSOX1 and TFRC). Principal component analysis based on this signature is able to distinguish TICs from cancer cells in vitro and also Leukemia-initiating cells (LICs) from non-LICs in the mouse model of acute promyelocytic leukemia (APL). Majority of the described changes were also recapitulated in an alternative model represented by MCF7 cells resistant to tamoxifen (TAMR) that exhibit features of TICs. Our findings point to the critical importance of redox balance and iron metabolism-related genes and proteins in the context of cancer and TICs that could be potentially used for cancer diagnostics or therapy.