Abstract Radioresistance is a challenge in the treatment of esophageal squamous cell carcinoma (ESCC). MicroRNAs (miRNAs) are known to play an important role in the functional modification of cancer cells and resent studies have reported the miRNA-mediated radiotherapy resistance. However, further research would be necessary to reveal the regulation mechanisms and the treatment strategies using miRNA have yet to be established in ESCC. We compared the miRNA expression profile in ESCC parental (TE-4) and acquired radioresistance (TE-4R) cell line using miRNA microarray and qRT-PCR. Our data showed that miR-338-5p, one of the target miRNA biomarkers, was significantly downregulated in TE-4R. Ectopic overexpression of the miR-338-5p induced apoptosis and sensitivity to radiation treatment by interfering the survivin, which is known to play an inhibitor of apoptosis. Over expression of survivin using plasmid vector reversed miR-338-5p induced apoptosis. From tumor xenograft experiments, we found that therapeutic delivery of the miR-338-5p mimics via direct injection to tumor mass increased sensitivity to radiation therapy. In conclusion, these findings suggested that miR-338-5p is a potential radiosensitizer and may be one of the therapeutic biomarkers for radioresistant in ESCC. Citation Format: Misun Park, Hyeon-joon Yoon, Moon Chul Kang, Jun Ah Lee, Junhye Kwon, Haewon Lee. MicroRNA-338-5p regulates radioresistance by directly targeting survivin in esophageal squamous cell carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5858. doi:10.1158/1538-7445.AM2017-5858
LXXLL/leucine zipper-containing alternative reading frame (ARF)-binding protein (LZAP) was recently shown to function as a tumor suppressor through inhibition of the NF-κB signaling pathway. LZAP is also known as a negative regulator of cell invasion, and its expression was demonstrated to be reduced in several tumor tissues. However, the molecular mechanism of the negative effect of LZAP on cell invasion is unclear. In this study, we identify NLBP as a novel LZAP-binding protein using tandem affinity purification. We demonstrate the negative effects of NLBP on cell invasion and the NF-κB signaling pathway. NLBP expression was not detected in hepatocellular carcinoma cells with strong invasive activity, whereas its expression was detected in a hepatocellular carcinoma cell line with no invasive activity. We also demonstrate that these two proteins mutually affect the stability of each other by inhibiting ubiquitination of the other protein. Based on these results, we suggest that NLBP may act as a novel tumor suppressor by inhibiting cell invasion, blocking NF-κB signaling, and increasing stability of the LZAP protein. LXXLL/leucine zipper-containing alternative reading frame (ARF)-binding protein (LZAP) was recently shown to function as a tumor suppressor through inhibition of the NF-κB signaling pathway. LZAP is also known as a negative regulator of cell invasion, and its expression was demonstrated to be reduced in several tumor tissues. However, the molecular mechanism of the negative effect of LZAP on cell invasion is unclear. In this study, we identify NLBP as a novel LZAP-binding protein using tandem affinity purification. We demonstrate the negative effects of NLBP on cell invasion and the NF-κB signaling pathway. NLBP expression was not detected in hepatocellular carcinoma cells with strong invasive activity, whereas its expression was detected in a hepatocellular carcinoma cell line with no invasive activity. We also demonstrate that these two proteins mutually affect the stability of each other by inhibiting ubiquitination of the other protein. Based on these results, we suggest that NLBP may act as a novel tumor suppressor by inhibiting cell invasion, blocking NF-κB signaling, and increasing stability of the LZAP protein.
Receptor-associated protein 80 (RAP80) is a component of the BRCA1-A complex that recruits BRCA1 to DNA damage sites in the DNA damage-induced ubiquitin signaling pathway. RAP80-depleted cells showed defective G(2)-M phase checkpoint control. In this study, we show that RAP80 protein levels fluctuate during the cell cycle. Its expression level peaked in the G(2) phase and declined during mitosis and progression into the G(1) phase. Also, RAP80 is polyubiquitinated and degraded by the anaphase-promoting complex (APC/C)(Cdc20) or (APC/C)(Cdh1). Consistent with this, knockdown of Cdc20 or Cdh1 expression by transfecting with small interfering RNAs blocked RAP80 degradation during mitosis or the G(1) phase, respectively. A conserved destruction box (D box) in RAP80 affected its stability and ubiquitination, which was dependent on APC/cyclosome(Cdc20) (C(Cdc20)) or APC/cyclosome(Cdh1) (C(Cdh1)). In addition, overexpression of RAP80 destruction box1 deletion mutant attenuated mitotic progression. Thus, APC/C(Cdc20) or APC/C(Cdh1) complexes regulate RAP80 stability during mitosis to the G(1) phase, and these events are critical for a novel function of RAP80 in mitotic progression.
Radiotherapy is a leading treatment for various types of cancer. However, exposure to high-dose ionizing radiation causes acute gastrointestinal injury and gastrointestinal syndrome. This has significant implications for human health, and therefore, radioprotection is a major area of research. Radiation induces the loss of intestinal stem cells; hence, the protection of stem cells expressing LGR5 (a marker of intestinal epithelial stem cells) is a key strategy for the prevention of radiation-induced injury. In this study, we identified valproic acid (VPA) as a potent radioprotector using an intestinal organoid culture system. VPA treatment increased the number of LGR5+ stem cells and organoid regeneration after irradiation. N-[N-(3,5-difluorophenacetyl)-l-alanyl]-S-phenylglycine t-butyl ester (DAPT, an inhibitor of NOTCH signaling) blocked the radioprotective effects of VPA, indicating that NOTCH signaling is a likely mechanism underlying the observed effects of VPA. In addition, VPA acted as a radiosensitizer via the inhibition of histone deacetylase (HDAC) in a colorectal cancer organoid. These results demonstrate that VPA exerts strong protective effects on LGR5+ stem cells via NOTCH signaling and that the inhibition of NOTCH signaling reduces these protective effects, providing a basis for the improved management of radiation injury.
The epidermal growth factor receptor (EGFR) is one of the most comprehensively studied molecular targets in head and neck squamous cell carcinoma (HNSCC). However, inherent and acquired resistance are serious problems and are responsible for limited clinical efficacy and tumor recurrence. In this study, we evaluated the feasibility of immuno-positron emission tomography (PET) imaging and radioimmunotherapy (RIT) with 64Cu-/177Lu-PCTA-cetuximab in cetuximab-resistant SNU-1066 HNSCC xenografted model. The cellular uptake of 64Cu/177Lu-3,6,9,15-tetraazabicyclo[9.3.1]-pentadeca-1(15),11,13-triene-3,6,9,-triacetic acid (PCTA)-cetuximab showed good correlation with western blot and flow cytometry analysis in EGFR expression level of various HNSCC cells. 177Lu-PCTA-cetuximab selectively killed cetuximab-resistant SNU-1066 cells in vitro. 64Cu-/177Lu-PCTA-cetuximab specifically accumulated in SNU-1066 tumor and those uptakes were peaked at 48 h and 7 day, respectively in biodistribution, PET and single-photon emission computed tomography/computed tomography (SPECT/CT) imaging. RIT with single dose of 177Lu-PCTA-cetuximab exhibited significant tumor regression and markedly reduced 2-[18F]fluoro-2-deoxy-D-glucose (18F-FDG) uptake, compared to other groups. Proliferation index were dramatically decreased and apoptotic index increased in RIT group. These results suggest that a diagnostic and therapeutic convergence radiopharmaceutical, 64Cu-/177Lu-PCTA-cetuximab has the potential of target selection using immuno-PET imaging and targeted therapy by RIT in EGFR expressing cetuximab-resistant HNSCC tumors.
Endothelial cell proliferation and migration is essential to angiogenesis. Typically, proliferation and chemotaxis of endothelial cells is driven by growth factors such as vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF). VEGF activates phospholipases (PLCs) - specifically PLCgamma1 - that are important for tubulogenesis, differentiation and DNA synthesis. However, we show here that VEGF, specifically through VEGFR2, induces phosphorylation of two serine residues on PLCbeta3, and this was confirmed in an ex vivo embryoid body model. Knockdown of PLCbeta3 in HUVEC cells affects IP3 production, actin reorganization, migration and proliferation; whereas migration is inhibited, proliferation is enhanced. Our data suggest that enhanced proliferation is precipitated by an accelerated cell cycle, and decreased migration by an inability to activate CDC42. Given that PLCbeta3 is typically known as an effector of heterotrimeric G-proteins, our data demonstrate a unique crosstalk between the G-protein and receptor tyrosine kinase (RTK) axes and reveal a novel molecular mechanism of VEGF signaling and, thus, angiogenesis.
c-Myc is a cellular onco-protein and a transcriptional activator important for cell growth, cell division, and tumorigenesis. Despite all that is known of its function, the mechanism of how c-Myc contributes to tumorigenesis is unclear. To gain insight into the mechanism through which c-Myc protein exerts its oncogenic activity, we performed large-scale, tandem repeat affinity purification and identified the F box only protein 8 (FBX8), an F-box- and Sec7 domain-containing protein, as a novel Myc-binding protein. The c-Myc/FBX8 interaction was mediated by the c-Myc box II (MBII) region. We also confirmed that Myc protein overexpression in 293T cells affected FBX8 cellular translocation and led to recovery from FBX8-mediated inhibition of ADP-ribosylation factor 6 (ARF6) function during cell invasion. Together, these results suggest that FBX8 is a novel c-Myc binding protein and that c-Myc induces cell invasive activity through the inhibition of FBX8 effects on ARF6 function during cell invasion.
Bcl-w a pro-survival member of the Bcl-2 protein family, is expressed in a variety of cancer types, including gastric and colorectal adenocarcinomas, as well as glioblastoma multiforme (GBM), the most common and lethal brain tumor type. Previously, we demonstrated that Bcl-w is upregulated in gastric cancer cells, particularly those displaying infiltrative morphology. These reports propose that Bcl-w is strongly associated with aggressive characteristic, such as invasive or mesenchymal phenotype of GBM. However, there is no information from studies of the role of Bcl-w in GBM. In the current study, we showed that Bcl-w is upregulated in human glioblastoma multiforme (WHO grade IV) tissues, compared with normal and glioma (WHO grade III) tissues. Bcl-w promotes the mesenchymal traits of glioblastoma cells by inducing vimentin expression via activation of transcription factors, β-catenin, Twist1 and Snail in glioblastoma U251 cells. Moreover, Bcl-w induces invasiveness by promoting MMP-2 and FAK activation via the PI3K-p-Akt-p-GSK3β-β-catenin pathway. We further confirmed that Bcl-w has the capacity to induce invasiveness in several human cancer cell lines. In particular, Bcl-w-stimulated β-catenin is translocated into the nucleus as a transcription factor and promotes the expression of target genes, such as mesenchymal markers or MMPs, thereby increasing mesenchymal traits and invasiveness. Our findings collectively indicate that Bcl-w functions as a positive regulator of invasiveness by inducing mesenchymal changes and that trigger their aggressiveness of glioblastoma cells.
Esophageal squamous cell carcinoma (ESCC), the most common subtype of esophageal cancer in East Asian countries, is still associated with a poor prognosis because of the high frequency of lymph node metastasis and invasion. In our previous study, we identified a novel methylation gene, cysteine dioxygenase 1 (CDO1) that is involved in the conversion of cysteine to cysteine sulfinate, and plays a key role in taurine biosynthesis. Decreased expression of CDO1 was observed in ESCC cell lines and tumors derived from patient tissues, and CDO1 silencing could be reversed by treatment with 5-aza-2′-deoxycytidine in six ESCC cell lines. Forced expression of CDO1 in three different ESCC cell lines, TE-4, TE-6, and TE-14, significantly decreased tumor cell growth, cell migration, invasion, and the ability of colony formation. Although CDO1 expression was not found to significantly correlate with survival in ESCC patients, our results suggest that methylation-regulated CDO1 may represent a functional tumor suppressor and a potentially valuable diagnostic biomarker for ESCC.
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