TET2 Is Downregulated in Early Esophageal Squamous Cell Carcinoma and Promotes Esophageal Squamous Cell Malignant Behaviors.

OBJECTIVE: To explore the expression of the ten eleven translocation (TET) 2 protein in early esophageal squamous cell carcinoma (EESCC), precancerous lesions, and cell lines and to evaluate the effect of TET2 on the functional behavior of EC109 esophageal cancer cells. METHODS: Thirty-one samples of EESCC and precancerous lesions collected via endoscopic submucosal dissection at Taihe Hospital, Shiyan, from February 1, 2017, to February 1, 2019, were analyzed. The study involved evaluating TET2 expression levels in lesion tissue and adjacent normal epithelium, correlating these with clinical pathological features. Techniques including 3-(4,5-dimethythiazol-2-yl)-2,5-diphenyl tetrazolium bromide, cell scratch assays, flow cytometry for propidium iodide (PI) staining, Hoechst 333258/PI double staining, and nude mouse tumorigenesis experiments were employed to assess the effect of TET2 on the proliferation, migration, cell cycle, apoptosis, and tumorigenic ability of esophageal cancer cells. RESULTS: TET2 expression was notably reduced in early esophageal cancer tissue and correlated with tumor invasion depth (P < 0.05). Overexpression of TET2 enhanced the proliferation and migration of esophageal cancer cells, increased the cell population in the G0 phase, decreased it in the S phase, and intensified cell necrosis (P < 0.05). There was a partial increase in tumorigenic ability (P = 0.087). CONCLUSION: TET2 downregulation in ESCC potentially influences the necrosis, cell cycle, and tumorigenic ability of esophageal cancer cells, suggesting a role in the onset and progression of esophageal cancer.

Photo-induced intramolecular dearomative [5 + 4] cycloaddition of arenes for the construction of highly strained medium-sized-rings.

Medium-sized-ring compounds have been recognized as challenging synthetic targets in organic chemistry. Especially, the difficulty of synthesis will be augmented if an E-olefin moiety is embedded. Recently, photo-induced dearomative cycloaddition reactions that proceed via energy transfer mechanism have witnessed significant developments and provided powerful methods for the organic transformations that are not easily realized under thermal conditions. Herein, we report an intramolecular dearomative [5 + 4] cycloaddition of naphthalene-derived vinylcyclopropanes under visible-light irradiation and a proper triplet photosensitizer. The reaction affords dearomatized polycyclic molecules possessing a nine-membered-ring with an E-olefin moiety in good yields (up to 86%) and stereoselectivity (up to 8.8/1 E/Z). Detailed computational studies reveal the origin behind the favorable formation of the thermodynamically less stable isomers. Diverse derivations of the dearomatized products have also been demonstrated.

Theoretical studies on thermally activated delayed fluorescence of "carbene-metal-amide" Cu and Au complexes: geometric structures, excitation characters, and mechanisms.

"Carbene-metal(I)-amide" (CMA) complexes have garnered significant attention due to their remarkable properties and potential TADF applications in organic electronics. However, the atomistic working mechanism is still elusive. Herein, we chose two CMA complexes, i.e., cyclic (alkyl)(amino) carbene-copper[gold](I)-carbazole (CAAC-Cu[Au]-Cz), and employed both DFT and TD-DFT methods, in combination with radiative and nonradiative rate calculations, to investigate geometric and electronic structures of these two complexes in the ground and excited states, including orbital compositions, electronic transitions, absorption and emission spectra, and the luminescence mechanism. It is found that the coplanar or perpendicular conformations are coexistent in the ground state (S0), the lowest excited singlet state (S1), and the triplet state (T1). Both the coplanar and perpendicular S1 and T1 states have similar ligand-to-ligand charge transfer (LLCT) character between CAAC and Cz, and some charge-transfer character between metal atoms and ligands, which is beneficial to minimize the singlet-triplet energy gaps (ΔEST) and increase the spin-orbit coupling (SOC). An interesting three-state (S0, S1, T1) model involving two regions (coplanar and perpendicular) is proposed to rationalize the experimental TADF phenomena in the CMA complexes. In addition to the coplanar ones, the perpendicular S1 and T1 states also play a role in promoting the repopulation of the coplanar S1 exciton, which is a primary source for the delayed fluorescence.

Thermally activated delayed fluorescence of a Ir(III) complex: absorption and emission properties, nonradiative rates, and mechanism.

One recent experimental study reported a Ir(III) complex with thermally activated delayed fluorescence (TADF) phenomenon in solution, but its luminescent mechanism is elusive. In this work, we combined density functional theory (DFT), time-dependent DFT (TDDFT) and multi-state complete active space second-order perturbation theory (MS-CASPT2) methods to investigate excited-state properties, photophysics, and emission mechanism of this Ir(III) complex. Two main absorption bands observed in experiments can be attributed to the electronic transition from the S0 state to the S1 and S2 states; while, the fluorescence and phosphorescence are generated from the S1 and T1 states, respectively. Both the S1 and T1 states have clear metal-to-ligand charge transfer (MLCT) character. The present computational results reveal a three-state model including the S0, S1 and T1 states to rationalize the TADF behavior. The small energy gap between the S1 and T1 states benefits the forward and reverse intersystem crossing (ISC and rISC) processes. At 300 K, the rISC rate is five orders of magnitude larger than the phosphorescence rate therefore enabling TADF. At 77 K, the rISC rate is sharply decreased but remains close to the phosphorescence rate; therefore, in addition to the phosphorescence, the delayed fluorescence could also contribute to the experimental emission. The estimated TADF lifetime agrees well with experiments, 9.80 vs. 6.67 µs, which further verifies this three-state model.

Tuning functionalized hexagonal boron nitride quantum dots for full visible-light fluorescence emission.

Tunable photoluminescence has been observed in hexagonal boron nitride quantum dots (BNQDs), but the underlying luminescence mechanism remains elusive. In this study, we examine excited-state properties of several functionalized BNQDs models using density functional theory (DFT), time-dependent DFT, and multistate complete active space second-order perturbation theory (MS-CASPT2) methods. Unlike reported graphene quantum dots, photoluminescence of BNQDs is not affected by their sizes (<2.5 nm). Instead, the embedded single sp3 carbon atom connecting different functional groups can tune emission colors of BNQDs, whose emission wavelength cover full range of visible light and even extend toward near-infrared region. Further analysis reveals that both exciton self-trapping and electron-hole separation decrease HOMO-LUMO energy gaps, leading to large Stokes shifts. Moreover, uneven and even hybridizations induce blue- and red-shifted emission spectra. These findings provide novel insights into full-spectrum emission of BNQDs modified with functional groups.

Thermally Activated Delayed Fluorescence of a Dinuclear Platinum(II) Compound: Mechanism and Roles of an Upper Triplet State.

A dinuclear Pt(II) compound was reported to exhibit thermally activated delayed fluorescence (TADF); however, the luminescence mechanism remains elusive. To reveal relevant excited-state properties and luminescence mechanism of this Pt(II) compound, both density function theory (DFT) and time-dependent DFT (TD-DFT) calculations were carried out in this work. In terms of the results, the S1 and T2 states show mixed intraligand charge transfer (ILCT)/metal-to-ligand CT (MLCT) characters while the T1 state exhibits mixed ILCT/ligand-to-metal CT (LMCT) characters. Mechanistically, a four-state (S0 , S1 , T1 , and T2 ) model is proposed to rationalize the TADF behavior. The reverse intersystem crossing (rISC) process from the initial T1 to final S1 states involves two up-conversion channels (direct T1 →S1 and T2 -mediated T1 →T2 →S1 pathways) and both play crucial roles in TADF. At 300 K, these two channels are much faster than the T1 phosphorescence emission enabling TADF. However, at 80 K, these rISC rates are reduced by several orders of magnitude and become very small, which blocks the TADF emission; instead, only the phosphorescence is observed. These findings rationalize the experimental observation and could provide useful guidance to rational design of organometallic materials with superior TADF performances.

Thermally Activated Delayed Fluorescence of a Pyromellitic Diimide Derivative in the Film Environment Investigated by Combined QM/MM and MS-CASPT2 Methods.

Arylene diimide compounds exhibit thermally activated delayed fluorescence (TADF), but its mechanism remains elusive. Herein we studied the TADF mechanism of a carbazole-substituted pyromellitic diimide derivative (CzPhPmDI) in poly(methyl methacrylate) (PMMA) film by using DFT, TD-DFT, and MS-CASPT2 methods within the QM/MM framework. We found that the TADF mechanism involves three electronic states (i.e., S0, S1, and T1), but the T2 state is not involved because its energy is higher than the S1 state by 6.9 kcal/mol. By contrast, the T1 state is only 3.2 kcal/mol lower than the S1 state and such small energy difference benefits the reverse intersystem crossing (rISC) process from T1 to S1 thereto TADF. This point is seconded by relevant radiative and nonradiative rates calculated. At room temperature, the ISC rate from S1 to T1 is calculated to be 6.1 × 106 s-1, which is larger than the fluorescence emission rate, 2.2 × 105 s-1; thus, the dominant S1 population converts to the T1 state. However, in the T1 state, the rISC process (1.8 × 104 s-1) becomes the most important channel because of the negligible phosphorescence emission rate (3.5 × 10-2 s-1). So, the T1 population is still converted back to the S1 state to fluoresce enabling TADF. Unfortunately, the rISC process is blocked in low temperature. Besides, we found that relevant Huang-Rhys factors have dominant contribution from low-frequency vibrational motion related to the torsional motion of functional groups. These gained insights could provide useful information for the design of organic TADF materials with excellent luminescence efficiency.

Thermally Activated Delayed Fluorescence Mechanism of a Bicyclic "Carbene-Metal-Amide" Copper Compound: DFT/MRCI Studies and Roles of Excited-State Structure Relaxation.

Herein we investigated the luminescence mechanism of one "carbene-metal-amide" copper compound with thermally activated delayed fluorescence (TADF) using density functional theory (DFT)/multireference configuration interaction, DFT, and time-dependent DFT methods with the polarizable continuum model. The experimentally observed low-energy absorption and emission peaks are assigned to the S1 state, which exhibits clear interligand and partial ligand-to-metal charge-transfer character. Moreover, it was found that a three-state (S0, S1, and T1) model is sufficient to describe the TADF mechanism, and the T2 state should play a negligible role. The calculated S1-T1 energy gap of 0.10 eV and proper spin-orbit couplings facilitate the reverse intersystem crossing (rISC) from T1 to S1. At 298 K, the rISC rate of T1 → S1 (∼106 s-1) is more than 3 orders of magnitude larger than the T1 phosphorescence rate (∼103 s-1), thereby enabling TADF. However, it disappears at 77 K because of a very slow rISC rate (∼101 s-1). The calculated TADF rate, lifetime, and quantum yield agree very well with the experimental data. Methodologically, the present work shows that only considering excited-state information at the Franck-Condon point is insufficient for certain emitting systems and including excited-state structure relaxation is important.

Room-Temperature Phosphorescence and Thermally Activated Delayed Fluorescence in the Pd Complex: Mechanism and Dual Upconversion Channels.

The Pd complex PdN3N exhibits an unusual dual emission of room-temperature phosphorescence (RTP) and thermally activated delayed fluorescence (TADF), but the mechanism is elusive. Herein, we employed both density functional theory (DFT) and time-dependent DFT (TD-DFT) methods to explore excited-state properties of this Pd complex, which shows that the S0, S1, T1, and T2 states are involved in the luminescence. Both the S1 → T1 and S1 → T2 intersystem crossing (ISC) processes are more efficient than the S1 fluorescence and insensitive to temperature. However, the direct T1 → S1 and T2-mediated T1 → T2 → S1 reverse ISC (rISC) processes change remarkably with temperature. At 300 K, these two processes are more efficient than the T1 phosphorescence and therefore enable TADF. Importantly, the T1 → S1 rISC and T1 phosphorescence rates are comparable at 300 K, which leads to dual emissions of TADF and RTP, whereas these two channels become blocked at 100 K so that only the T1 phosphorescence is recorded experimentally.

Clinicopathological features of esophageal schwannomas in mainland China: systematic review of the literature.

OBJECTIVE: Esophageal schwannoma (ES) are rare and mostly benign neurogenic tumors. The clinical misdiagnosis rate of it is high. In this study, the clinicopathologic features of ES in mainland China were studied to better understand the disease and improve the diagnosis and treatment rate. METHODS: A systematic review was conducted in accordance with PRISMA guidelines. The keywords "esophageal schwannoma", "esophageal neurinoma" and "esophageal neurilemoma" were searched for databases such as Pubmed, EMbase, Wanfang Database and Chinese National Knowledge Infrastructure. The search time frame for database was until July 2019. Combined with our patient, the clinicopathological data and the diagnosis and treatment of ES were summarized. RESULTS: ES occurs in the upper part of the mediastinum and in the thoracic esophagus in most patients in the neck, upper and middle segments. CT and PET/CT examinations can be used for diagnosis, but the differentiation value of both benign and malignant ES is similar. The histopathological findings of forceps biopsy specimens are often difficult to diagnose, and deep tissue biopsies may increase pathological accuracy. EUS-FNA is also recommended for ES diagnosis, but it may also be misdiagnosed. Pathological features include a fusiform arrangement in a palisade-like structure or a tumor cell arranged in a network to form a loose structure. ES characteristic immunohistochemistry results showed that S-100 protein has strong immunological activity. CONCLUSION: The definitive diagnosis requires immunohistochemistry, especially immunological reaction with S-100 protein. The appropriate treatment plan should be selected according to the diameter of the lesion. The overall prognosis of ES is good, but attention should be paid to follow-up.

QM/MM studies on luminescence mechanism of dinuclear copper iodide complexes with thermally activated delayed fluorescence.

The QM/MM method is employed to investigate the photophysical mechanism of two dinuclear copper iodide complexes with thermally activated delayed fluorescence (TADF). The S1-T1 energy differences (ΔE ST) in these two complexes are small enough so that repopulating the S1 state from T1 becomes energetically allowed. Both forward and reverse intersystem crossing (ISC and rISC) processes are much faster than the corresponding radiative fluorescence and phosphorescence processes [k ISC (108 s-1) > k F r (106 s-1), k rISC (105 s-1) > k P r (103 s-1)]. The faster rISC process than the phosphorescence emission enables TADF. Moreover, the diphosphine ligands are found to play an important role in regulating the electronic structures and thereto the radiative and nonradiative rate constants. The present work rationalizes experimental phenomena and helps understand the intrinsic luminescence properties. The obtained insights could be useful for tuning the luminescence performance of dicopper-based luminescence materials.

QM and ONIOM studies on thermally activated delayed fluorescence of copper(i) complexes in gas phase, solution, and crystal.

Herein, we have employed B3LYP and TD-B3LYP methods with the QM/MM approach to study the thermally activated delayed fluorescence (TADF) phenomenon of two Cu(i) complexes bearing 5-(2-pyridyl)-tetrazolate (PyrTet) and phosphine (POP) ligands in the gas phase, solution, and crystal form. On the basis of spectroscopic properties, ground- and excited-state geometric and electronic structures, and related radiative and nonradiative rates, we have found that (1) the S1 and T1 excited states have clear metal-to-ligand charge transfer character from the Cu(i) atom to the PyrTet group; (2) the S1 and T1 states have a very small energy gap ΔES1-T1, less than 0.18 eV, which makes the forward and reverse intersystem crossing ISC and rISC processes between the S1 and T1 states very efficient; and (3) the low-frequency vibrational modes related to the torsional motion of the POP and PyrTet groups are found to have significant Huang-Rhys factors and are responsible for the efficient ISC and rISC rates. However, the corresponding Huang-Rhys factors are remarkably suppressed in the crystal compared with those in the gas phase and in solution due to the rigidity of the crystal surroundings; as a result, the ISC and rISC rates are accordingly reduced slightly in the crystal. This comparison also demonstrates that the surrounding effects are very important for modulating the photophysical properties of the Cu(i) complexes. Finally, our work gives helpful insights into the TADF mechanism of the Cu(i) compounds, which could assist in rationally designing TADF materials with excellent performance.

Electronic structure calculations and nonadiabatic dynamics simulations of excited-state relaxation of Pigment Yellow 101.

Pigment Yellow 101 (PY101) is widely used as a typical pigment due to its excellent excited-state properties. However, the origin of its photostability is still elusive. In this work, we have systematically investigated the photodynamics of PY101 by performing combined electronic structure calculations and trajectory-based nonadiabatic dynamics simulations. On the basis of the results, we have found that upon photoexcitation to the S1 state, PY101 undergoes an essentially barrierless excited-state intramolecular single proton transfer generating an S1 keto species. In the keto region, there is an energetically accessible S1/S0 conical intersection that funnels the system to the S0 state quickly. In the S0 state, the keto species either goes back to its trans-enol species through a ground-state reverse hydrogen transfer or arrives at the cis-keto region. In addition, we have found an additional excited-state decay channel for the S1 enol species, which is directly linked to an S1/S0 conical intersection located in the enol region. This mechanism has also been confirmed by our dynamics simulations, in which about 54% of the trajectories decay to the S0 state via the enol S1/S0 conical intersection; while the remaining ones employ the keto S1/S0 conical intersection. The gained mechanistic information helps us understand the photostability of the PY101 chromophore and its variants with the same molecular scaffold.

Quantum Mechanics/Molecular Mechanics Study on the Photoreactions of Dark- and Light-Adapted States of a Blue-Light YtvA LOV Photoreceptor.

The dark- and light-adapted states of YtvA LOV domains exhibit distinct excited-state behavior. We have employed high-level QM(MS-CASPT2)/MM calculations to study the photochemical reactions of the dark- and light-adapted states. The photoreaction from the dark-adapted state starts with an S1 →T1 intersystem crossing followed by a triplet-state hydrogen transfer from the thiol to the flavin moiety that produces a diradical intermediate, and a subsequent internal conversion that triggers a barrierless C-S bond formation in the S0 state. The energy profiles for these transformations are different for the four conformers of the dark-adapted state considered. The photochemistry of the light-adapted state does not involve the triplet state: photoexcitation to the S1 state triggers C-S bond cleavage followed by recombination in the S0 state; both these processes are essentially barrierless and thus ultrafast. The present work offers new mechanistic insights into the photoresponse of flavin-containing blue-light photoreceptors.

Color-tunable phosphorescence of 1,10-phenanthrolines by 4,7-methyl/-diphenyl/-dichloro substituents in cocrystals assembled via bifurcated C-I...N halogen bonds using 1,4-diiodotetrafluorobenzene as a bonding donor.

Single-crystal X-ray diffraction reveals a series of phosphorescent cocrystals which were assembled by 1,4-diiodotetrafluorobenzene (1,4-DITFB) and either 4,7-dimethyl-1,10-phenanthroline (DMPhe), 4,7-diphenyl-1,10-phenanthroline (DPPhe) or 4,7-dichloro-1,10-phenanthroline (DClPhe) via C-I...N halogen bonding. These cocrystals, labeled (1), (2) and (3), respectively, are phosphorescent and a distinct change in phosphorescent color can be observed from orange-yellow, green to yellow-green, with well defined vibrational band maxima at 587, 520 and 611 nm for (1), (2) and (3). Based on the dependence of halogen bonding in sites and strength, we discussed the impact of substituents with different electron-withdrawing effects and steric hindrance on intermolecular noncovalent interactions and phosphorescence. The method of inducing and modulating phosphorescence by halogen bonding and other weak non-covalent interactions through changing the substituent groups of molecules should be significant in both theory and the application of optical function materials with predictable and modulated luminescent properties.

Excited-State Decay Paths in Tetraphenylethene Derivatives.

The photophysical properties of tetraphenylethene (TPE) compounds may differ widely depending on the substitution pattern, for example, with regard to the fluorescence quantum yield ϕf and the propensity to exhibit aggregation-induced emission (AIE). We report combined electronic structure calculations and nonadiabatic dynamics simulations to study the excited-state decay mechanisms of two TPE derivatives with four methyl substituents, either in the meta position (TPE-4mM, ϕf = 0.1%) or in the ortho position (TPE-4oM, ϕf = 64.3%). In both cases, two excited-state decay pathways may be relevant, namely, photoisomerization around the central ethylenic double bond and photocyclization involving two adjacent phenyl rings. In TPE-4mM, the barrierless S1 cyclization is favored; it is responsible for the ultralow fluorescence quantum yield observed experimentally. In TPE-4oM, both the S1 photocyclization and photoisomerization paths are blocked by non-negligible barriers, and fluorescence is thus feasible. Nonadiabatic dynamics simulations with more than 1000 surface hopping trajectories show ultrafast cyclization upon photoexcitation of TPE-4mM, whereas TPE-4oM remains unreactive during the 1 ps simulations. We discuss the chances for spectroscopic detection of the postulated cyclic photoproduct of TPE-4mM and the relevance of our findings for the AIE process.

Photochromic Mechanism of a Bridged Diarylethene: Combined Electronic Structure Calculations and Nonadiabatic Dynamics Simulations.

Intramolecularly bridged diarylethenes exhibit improved photocyclization quantum yields because the anti-syn isomerization that originally suppresses photocyclization in classical diarylethenes is blocked. Experimentally, three possible channels have been proposed to interpret experimental observation, but many details of photochromic mechanism remain ambiguous. In this work we have employed a series of electronic structure methods (OM2/MRCI, DFT, TDDFT, RI-CC2, DFT/MRCI, and CASPT2) to comprehensively study excited state properties, photocyclization, and photoreversion dynamics of 1,2-dicyano[2,2]metacyclophan-1-ene. On the basis of optimized stationary points and minimum-energy conical intersections, we have refined experimentally proposed photochromic mechanism. Only an S1/S0 minimum-energy conical intersection is located; thus, we can exclude the third channel experimentally proposed. In addition, we find that both photocyclization and photoreversion processes use the same S1/S0 conical intersection to decay the S1 system to the S0 state, so we can unify the remaining two channels into one. These new insights are verified by our OM2/MRCI nonadiabatic dynamics simulations. The S1 excited-state lifetimes of photocyclization and photoreversion are estimated to be 349 and 453 fs, respectively, which are close to experimentally measured values: 240 ± 60 and 250 fs in acetonitrile solution. The present study not only interprets experimental observations and refines previously proposed mechanism but also provides new physical insights that are valuable for future experiments.

Phosphorescence of several cocrystals assembled by diiodotetrafluorobenzene and three ring angular diazaphenanthrenes via CI···N halogen bond.

X-ray single crystal diffraction reveals that a series of cocrystals are assembled by three ring angular diazaphenanthrenes including 1,7-phenanthroline, 4,7-phenanthroline and 1,10-phenanthroline with 1,4-/1,2-diiodotetrafluorobenzenes via C-I···N halogen bonding (XB) as main driving force. Raman shift of the symmetric CI stretching vibration coupling with ring elongation and lateral ring expansion to a lower frequency by 2 to 7cm-1 for 1,4-DITFB in cocrystals shows the existence of C-I···N halogen bonding. All cocrystals phosphoresce with a distinct change of colors from yellow, orange, pink to red. Also phosphorescent lifetimes of cocrystals containing 1,4-DITFB are longer than those of others constructed by 1,2-DITFB. These phenanthrolines monomers have almost same phosphorescence wavelength (the max. at 493nm) in ß-cyclodextrin solution in the presence of bromocyclohexane as a pure physically heavy atom perturber. The results demonstrate CI···N XB makes heavy atom effect more direct and efficient, and influences significantly the energy level of the lowest lying excited triplet states and the population of electrons to triplet state of the angular diazaphenanthrenes because of greater contribution of lone pair electrons from nitrogen to conjugation systems. Meanwhile, the XB modulates luminescent behaviors due to difference in positions of nitrogen atoms. Good coplanarity, i.e., torsion angles being closer to 0°, in CI···N halogen bonded binary systems also is an important factor affecting the appearance quality of cocrystals.

Differentiation potential of bone marrow stromal cells to enteric neurons in vitro.

OBJECTIVE: To investigate whether bone marrow stromal cells (BMSC) can be induced to differentiate into enteric neurons and to produce more nerve growth factor (NGF) and glial cell line-derived neurotrophic factor (GDNF). METHODS: Bone marrow stromal cells were harvested from male Sprague-Dawley rats and cultured in Dulbecco's modified eagle medium supplemented with 20% fetal bovine serum. The BMSC were passaged six times and characterized by flow cytometry. The BMSC were pre-induced by basic fibroblast growth factor (10 ng/mL) for 24 h, then induced with GDNF in fetal gut condition medium (FGCM) for 10 days. The expressions of neuronal markers neural specific enolase (NSE), neurofilament (NF), glial cell marker, glial fibrillary acedic protein (GFAP), and enteric neuronal marker protein gene product 9.5 (PGP9.5), neural nitric oxide synthase (nNOS), and enteric neural transmitter vasoactive intestinal polypeptide (VIP) were detected by fluorescent immunohistochemistry. Expression levels of GDNF and NGF mRNA were determined by RT-PCR. RESULTS: The cultured BMSC were CD90 (99.7%) positive and CD45 negative on flow cytometry. At day 10 of induction, 58.5 +/- 10.8% cells adopted neuron-like morphological changes and showed expression of NSE (47.6 +/- 7.5%), NF (75.6 +/- 8.4%), GFAP (negative), PGP9.5 (57.7 +/- 6.5%), nNOS (46.6 +/- 5.4%) and VIP (72.3 +/- 6.7%) by immunofluorescence. The BMSC expressed low levels of NGF and GDNF mRNA; however, after induction of GDNF in FGCM, the expression levels of NGF and GDNF mRNA were significantly increased. CONCLUSION: Bone marrow stromal cells have the potential to be induced to differentiate into enteric neurons, express enteric neural transmitters, and produce more NGF and GDNF. Therefore, BMSC could be used as new method to treat gastrointestinal motility disorders associated with enteric neural lesions.

[Effects of inhibition of cyclooxygenase-2 by RNA interference on proliferation and apoptosis of human gastric cancer cells: an experimental study with human gastric cancer cells and mice].

OBJECTIVE: To study whether the expression level of cyclooxygenase-2 (COX-2) is correlated with the proliferation and apoptosis of cancer cells and to study whether the RNA interference technique can be used in anti-cancer gene therapy. METHODS: WBH1, a eukaryotic expression plasmid of shRNA targeting on COX-2, was constructed. Human gastric cancer cells of the line SGC-7901 were cultured and divided into 3 groups: to be transfected with WBH1 or negative control plasmid HK, or used as un-transfected control group. RT-PCR and Western blotting were used to detect the expression of COX-2 mRNA and protein. MTT method was used to detect the proliferation of the cells. The apoptosis of the cells was determined by flow cytometry. Fifteen nude mice were randomly divided into 3 equal groups: 10 to be inoculated subcutaneously with WBH1 plasmid transfected SGC-7901 cells (inhibition group) or negative control plasmid HK transfected SGC-7901 cells, and 5 were used as un-transfected controls. The mice were observed for 4 weeks to observe the survival and the tumorigenesis. Then the mice were killed to take out the tumors. The tumorigenic rate and tumor inhibition rate were evaluated. RESULTS: The proliferation of the SGC-7091 cells transfected with WHB1 plasmid did not changed significantly 24 and 48 hours after the transfection, however, decreased significantly 96 hours and 1 week after (both P < 0.01). The apoptotic rate of the SGC-7091 cells transfected with WHB1 plasmid was 52.28% +/- 17.91%, significantly higher than that of the cells transfected with the control plasmid HK (0.54% +/- 0.16%) and that of the un-transfected cells (0.52% +/- 0.27%, both P = 0.009) without a significant difference between the latter 2 groups (P = 0.998). Four weeks after inoculation the tumorigenic rate was 100% in both the un-transfected control mice and the mice inoculated with negative plasmid HK transfected SGC-7901 cells. There was no significant difference in tumor size between these 2 groups (P = 0.965). The tumorigenic rate of the mice in the inhibition group was 0.4 with an inhibition rate of 89.8%. The tumor weight of the inhibition group was 0.050 g +/- 0.003 g, significantly lighter than those of the control group and the group inoculated with negative plasmid transfected SGC cells (0.490 g +/- 0.017 g and 0.490 g +/- 0.013 g respectively, both P < 0.01). CONCLUSION: Construction of a eukaryotic expression vector expressing the specific shRNA targeting on COX-2, closely related to the proliferation and apoptosis of tumor cells, and transfection of it into the tumor cells helps inhibit the expression of COX-1, thus inhibiting the growth and proliferation of the tumor cells.