Signal peptide peptidase promotes tumor progression via facilitating FKBP8 degradation

Signal peptide peptidase (SPP) is an endoplasmic reticulum (ER)-resident aspartyl protease mediating intramembrane cleavage of type II transmembrane proteins. Increasing evidence has supported the role of SPP in ER-associated protein degradation. In the present study, we show that SPP expression is highly induced in human lung and breast cancers and correlated with disease outcome. Stable depletion of SPP expression in lung and breast cancer cell lines significantly reduced cell growth and migration/invasion abilities. Quantitative analysis of the proteomic changes of microsomal proteins in lung cancer cells by the stable isotope labeling with amino acids in cell culture (SILAC) approach revealed that the level of FKBP8, an endogenous inhibitor of mTOR, was significantly increased following SPP depletion. Co-immunoprecipitation assay and confocal immunofluorescence demonstrated that SPP interacted and colocalized with FKBP8 in ER, supporting that FKBP8 is a protein substrate of SPP. Cycloheximide chase and proteasome inhibition experiments revealed that SPP-mediated proteolysis facilitated FKBP8 protein degradation in cytosol. Further experiment demonstrated that the levels of phosphorylation in mTOR and its downstream effectors, S6K and 4E-BP1, were significantly lower in SPP-depleted cells. The reduced mTOR signaling and decreases of growth and migration/invasion abilities induced by SPP depletion in cancer cells could be reversed by FKBP8 downregulation. The implication of FKBP8 in SPP-mediated tumorigenicity was also observed in the xenograft model. Together, these findings disclose that SPP promotes tumor progression, at least in part, via facilitating the degradation of FKBP8 to enhance mTOR signaling.

Small Molecule Neuropilin-1 Antagonists Combine Antiangiogenic and Antitumor Activity with Immune Modulation through Reduction of Transforming Growth Factor Beta (TGFβ) Production in Regulatory T-Cells

We report the design, synthesis, and biological evaluation of some potent small-molecule neuropilin-1 (NRP1) antagonists. NRP1 is implicated in the immune response to tumors, particularly in Treg cell fragility, required for PD1 checkpoint blockade. The design of these compounds was based on a previously identified compound EG00229. The design of these molecules was informed and supported by X-ray crystal structures. Compound 1 (EG01377) was identified as having properties suitable for further investigation. Compound 1 was then tested in several in vitro assays and was shown to have antiangiogenic, antimigratory, and antitumor effects. Remarkably, 1 was shown to be selective for NRP1 over the closely related protein NRP2. In purified Nrp1⁺, FoxP3⁺, and CD25⁺ populations of Tregs from mice, 1 was able to block a glioma-conditioned medium-induced increase in TGFβ production. This comprehensive characterization of a small-molecule NRP1 antagonist provides the basis for future in vivo studies.

Identification of danthron as an isoform-specific inhibitor of HEME OXYGENASE-1/cytochrome P450 reductase interaction with anti-tumor activity

Background

Heme oxygenase (HO) catalyzes NADPH-dependent degradation of heme to liberate iron, carbon monoxide and biliverdin. The interaction between HO and cytochrome P450 reductase (CPR), an electron donor, is essential for HO activity. HO-1 is a stress-inducible isoform whereas HO-2 is constitutively expressed. HO-1 induction is commonly seen in cancers and impacts disease progression, supporting the possibility of targeting HO-1 for cancer therapy.

Methods

We employed a cell-based bioluminescence resonance energy transfer assay to screen compounds with ability to inhibit HO-1/CPR interaction. The effect of the identified compound on HO-1/CPR interaction was confirmed by pull down assay. Moreover, the anti-tumorigenic activity of the identified compound on HO-1-enhanced tumor growth and migration was assessed by trypan blue exclusion method and wound healing assay.

Results

Danthron was identified as an effective small molecule able to interfere with the interaction between HO-1 and CPR but not HO-2 and CPR. Additional experiments with structural analogues of danthron revealed that the positions of hydroxyl moieties significantly affected the potency of inhibition on HO-1/CPR interaction. Pull-down assay confirmed that danthron inhibited the interaction of CPR with HO-1 but not HO-2. Danthron suppressed growth and migration of HeLa cells with stable HO-1 overexpression but not mock cells. In contrast, anthrarufin, a structural analog with no ability to interfere HO-1/CPR interaction, exhibited no significant effect on HO-1-overexpressing HeLa cells.

Conclusions

These findings demonstrate that danthron is an isoform-specific inhibitor for HO-1/CPR interaction and may serve as a lead compound for novel anticancer drug.

γ-Synuclein Expression Is a Malignant Index in Oral Squamous Cell Carcinoma

Dysregulation of γ-synuclein (SNCG) has been reported in many cancers; however, its role in cancer development is still controversial. Here, we examined the potential involvement of DNA methylation in regulating SNCG and its role in oral squamous cell carcinoma (OSCC). We used 8 OSCC cell lines to investigate SNCG methylation and expression. SNCG methylation was examination by methylation-specific polymerase chain reaction and bisulfate sequencing. Cells showing a high degree of SNCG methylation were treated with 5-aza (methylation inhibitor), and changes in their methylation and expression profiles were analyzed. Functional effects of SNCG in OSCC were examined by its overexpression and knockdown. Additionally, methylation and expression of SNCG in OSCC tissues were investigated and correlated with clinicopathologic features. All OSCC cells showed detectable SNCG expression at the mRNA and protein levels. Methylation-specific polymerase chain reaction and bisulfate sequencing revealed high SNCG expression in SCC25 cells with the unmethylated allele, and their 15 CpG islands were unmethylated. The methylated allele was detected only in OEC-M1 cells exhibiting low SNCG expression, and their CpG islands were partially methylated. 5-aza treatment in OEC-M1 cells attenuated methylation and restored SNCG expression. SNCG overexpression increased colony forming, migration, and invasion abilities in OEC-M1 cells. Silencing SNCG in SCC25 cells suppressed these behaviors. All 25 tumor-adjacent normal tissues were negative for SNCG immunostaining. SNCG upregulation was frequently observed in dysplastic and OSCC tissues. Positive SNCG expression was found in 45% (37 of 82) OSCC tissues. Positive SNCG expression in OSCC significantly correlated with cancer staging and lymph node metastasis. However, SNCG methylation did not correlate with its expression and clinicopathologic variables in OSCC tissues. DNA methylation may participate in regulating SNCG expression in some OSCC cells. SNCG upregulation could be involved in OSCC progression.

Fabrication and characterization of high-T(c) YBa(2)Cu(3)O(7-x) nanoSQUIDs made by focused ion beam milling

We have fabricated high-T(c) nanoscale superconducting quantum interference devices (nanoSQUIDs) with a hole size of 250 nm × 250 nm based on a 100 nm bridge at 77 K by focused ion beam milling and ion implantation. At 78 K, the curve of the voltage branch became roughly linear and agreed with the Josephson-like behavior. The sample exhibited strong flux flow behavior at temperatures under 76 K. The voltage flux characteristic curves, V -I(mod), of the nanoSQUID at different bias currents at 78 K were observed. Typically, critical currents of 15 µA and peak-to-peak values of the voltage flux transfer function of 3.7 µV were measured. The measured data strongly suggest that the weak link structure could be a superconducting metal with a critical temperature T(c)' smaller than that (T(c)) of other YBa(2)Cu(3)O(7-x) (YBCO) films. This fabrication method of combining a nanobridge and ion implantation can improve the yield of nanojunctions and nanoSQUIDs.

Dopamine overload visualized in the basal ganglia of rabbit brain during heatstroke can be suppressed by hypothermia

The present study assesses the changes of dopamine levels in the basal ganglia (BG) of rabbit brain during heatstroke with or without hypothermia therapy. The dopamine levels were determined by using 6(F18) fluoro-L-dopa (FDOPA) positron emission tomography (PET) scan. Heatstroke was induced by exposing the anesthetized rabbits to a high blanket temperature (T(blanket)) of 45 degrees C. Hypothermia therapy was accomplished by decreasing T(blanket) from 45 to 16 degrees C. Regions-of-interest were carefully selected on the BG and cerebellum (C). The uptake ratio of FDOPA was defined as the mean counts per pixel from BG divided by the mean counts from C. BG/C ratios represent the dopamine levels of BG. The results showed that the values of mean arterial pressure (MAP) in heatstroke rabbits without hypothermia therapy were significantly lower than those in normothermic controls. However, BG/C FDOPA ratios were greater. Both the arterial hypotension and the increased BG/C FDOPA ratios observed during heatstroke were all reduced after hypothermia therapy. Our data demonstrate that the dopamine overload visualized in the BG of rabbit brain during heatstroke can be suppressed by hypothermia therapy.

Menadione-induced cell degeneration is related to lipid peroxidation in human cancer cells

The role of lipid peroxidation, intracellular glutathione and Ca2+ concentration in menadione-mediated toxicity was investigated in human hepatoma cell lines, Hep G2 and Hep 3B, and in human leukemia cell lines, CCRF-CEM and MOLT-3. Incubation of these cells with 80 microM menadione at 37 degrees C resulted in depletion of intracellular glutathione, increased intracellular Ca2+, and increased lipid peroxidation, events leading to cell degeneration. The sensitivity of these cells to menadione, in order, was: Hep G2 cells > Hep 3B cells > CCRF-CEM cells and MOLT-3 cells. The extent of menadione-induced lipid peroxidation in different cell types followed the same order as did their susceptibility to menadione-induced cell degeneration. The menadione-induced depletion in glutathione level was in the following sequence: Hep G2 cells > MOLT-3 and CCRF-CEM cells > Hep 3B cells. The extent of the menadione-induced increase in the intracellular Ca2+ concentration was: Hep G2 cells > Molt-3 cells > CCRF-CEM cells and Hep 3B cells. Pre-treatment of Hep G2 cells with 20 mM deferoxamine mesylate, an iron chelator, reduced both the menadione-induced cell degeneration and lipid peroxidation; however, it did not prevent the menadione-induced increase in intracellular Ca2+ nor the depletion of glutathione. These data suggest that menadione-induced cell degeneration is directly linked to lipid peroxidation, and that it is less related to the rise in intracellular Ca2+ and the depletion in glutathione content. Dicumarol (an inhibitor of DT diaphorase) enhanced the capacity of menadione to induce Hep 3B cell degeneration from 71.3% to 86.2% after 120 min of menadione treatment at 37 degrees C, but did not have this effect in Hep G2, CCRF-CEM or MOLT-3 cells. The activities of DT diaphorase were 52.4, 39.6, 1.5 and 1.8 nmol cytochrome c reduced/min/mg protein in Hep G2, Hep 3B, CCRF-CEM and MOLT-3 cells, respectively. The activity of DT diaphorase was much higher in Hep G2 cells than in the other cells. It seems that DT diaphorase may not, as suggested by others, protect against cell degeneration by quinones, such as menadione.