Association Between Preoperative Sleep Disturbance and Postoperative Delirium in Elderly: A Retrospective Cohort Study

Purpose

Postoperative sleep disturbance, characterized by diminished postoperative sleep quality, is a risk factor for postoperative delirium (POD); however, the association between pre-existing sleep disturbance and POD remains unclear. This study aimed to evaluate the association between preoperative sleep disturbance and POD in elderly patients after non-cardiac surgery.

Patients and methods

This retrospective cohort study was conducted at a single center and enrolled 489 elderly patients who underwent surgery between May 1, 2020, and March 31, 2021. Patients were divided into the sleep disorder (SD) and non-sleep disorder (NSD) groups according to the occurrence of one or more symptoms of insomnia within one month or sleep- Numerical Rating Scale (NRS)≥6 before surgery. The primary outcome was the incidence of POD. Propensity score matching analysis was performed between the two groups. Multiple logistic regression analysis was performed to identify the risk factors for POD.

Results

In both the unmatched cohort (16.0% vs 6.7%, P=0.003) and the matched cohort (17.0% vs 6.2%, P=0.023), the incidence of POD was higher in the SD group than in the NSD group. In addition, the postoperative sleep quality and the VAS score at postoperative 24 h were significantly lower in the SD group than in the NSD group. Multivariate logistic regression analysis indicated that age (Odds Ratio, 1.13 [95% CI: 1.04-1.23], P=0.003) and preoperative sleep disturbance (Odds Ratio, 3.03 [95% CI: 1.09-9.52], P=0.034) were independent risk factors for the development of POD.

Conclusion

The incidence of POD was higher in patients with pre-existing sleep disturbance than those without it. Whether improving sleep quality for preoperative sleep disturbance may help prevent POD remains to be determined.

Quantum storage of entangled photons at telecom wavelengths in a crystal

Quantum storage and distribution of entanglement are the key ingredients for realizing a global quantum internet. Compatible with existing fiber networks, telecom-wavelength entangled photons and corresponding quantum memories are of central interest. Recently, 167Er3+ ions have been identified as a promising candidate for an efficient telecom quantum memory. However, to date, no storage of entangled photons, the crucial step of quantum memory using these promising ions, 167Er3+, has been reported. Here, we demonstrate the storage and retrieval of the entangled state of two telecom photons generated from an integrated photonic chip. Combining the natural narrow linewidth of the entangled photons and long storage time of 167Er3+ ions, we achieve storage time of 1.936 μs, more than 387 times longer than in previous works. Successful storage of entanglement in the crystal is certified using entanglement witness measurements. These results pave the way for realizing quantum networks based on solid-state devices.

[Attach importance to the research of membrane surgery in an era of precision medicine]

The "Metastasis type V", "Envelope" theory and other concepts have been proposed to make gastric surgeons have a full understanding of the importance of mesogastrium, and the correct identification of the boundary of the mesogastrium is the premise of the complete mesogastrium excision(CME), and also the best way to achieve truly standardized D2 lymph node dissection for gastric cancer. In this paper, the boundary of the mesogastrium during complete mesogastrium excision for gastric cancer and how to achieve this operation in practice were studied, which help gastric surgeons finally find the mesogastrium tissue distributed throughout the gastric cancer surgery to achieve the best surgical treatment effect.

[Advances in molecular classification and precision immunotherapy for gastric cancer]

Gastric cancer (GC) is one of the malignant tumors with both high morbidity and mortality in China. Immunotherapy is expected to improve its prognosis. Molecular classification of GC based on multiple levels of assessment such as genes and tumor immune microenvironment (TiME), which can precisely screen the population with potential benefit from immunotherapy. It is helpful to make the treatment decision-making, and to further improve the efficacy of immunotherapy.

[Comparison of short-term clinical outcome between laparoscopic distal pancreatectomy and open distal pancreatectomy]

Objective: To compare the short-term clinical effect between laparoscopic distal pancreatectomy (LDP) and open distal pancreatectomy (ODP). Methods: We performed a retrospective study on 161 patients who underwent pancreatectomy between September 2017 to December 2018 in the Department of Pancreatic and Gastric Surgery, Cancer Hospital of Chinese Academy of Medical Sciences. According to the mode of operation, the patients were divided into the LDP group (n=43) and the ODP group (n=118). To compare the short-term clinical effect and safety between the LDP group and the ODP group, the preoperative clinical data, intraoperative related index, postoperative complication, postoperative recovery index, preoperative and postoperative inflammatory index were analyzed. Results: The preoperative clinical characteristics between the LDP group and the ODP group were not statistically different (P>0.05). The intraoperative blood loss in LDP group was (194.19±241.83) ml, significantly less than (315.17±295.94) ml in ODP group (P<0.05), and the postoperative exhaust time in LDP group was (3.00±0.72) days, significantly shorter than (4.05±0.97) days in OPD group (P<0.001). The time to get out of bed in LDP group was (3.14±1.01) days, significantly shorter than (3.55±1.05) days in OPD group (P<0.05). The postoperative eating time in LDP group was (3.88±1.61) days, significantly shorter than (5.11±1.56) days in ODP group (P<0.001). The time of the drainage tube removal in LDP group was (8.44±1.93) days, significantly shorter than (9.82±3.70) days in ODP group (P<0.05). The postoperative hospital stay in LDP group was (9.65±3.57) days, significantly shorter than (11.99±6.57) days in ODP group (P<0.05). The mean operation time in LDP group was (168.65±55.45) min, shorter than (171.23±65.61) min in ODP group, but without significant difference (P>0.05). The incidences of non-pancreatic fistula-related complications in LDP group and ODP group were 16.3% and 11.0%, respectively, without statistical significance (P>0.05). The incidences of pancreatic fistula in LDP group and ODP group were 16.3% and 19.5%, respectively, without statistical significance (P>0.05). The total incidences of complications in LDP group and ODP group were 32.6% and 30.5%, respectively, without statistical significance (P>0.05). The preoperative and postoperative inflammatory indexes between these two groups were not statistically different (P>0.05). Conclusions: Compared with ODP, LDP has the advantages of less intraoperative blood loss, faster postoperative recovery, shorter postoperative hospital stays, without increased postoperative complications and prolonged operation time. LDP is a safe and feasible operation method, and its short-term clinical effect is better than that of ODP.

[Research progress on the clinical features and mechanisms of COVID-19 combined with liver injury]

The highly contagious novel coronavirus pneumonia (COVID-19) that broke out in December 2019 has brought huge threats and losses to human society, so it has been the concern of every countries government. Presently, there are no specific drugs for COVID-19; however, a variety of potentially effective antiviral drugs, vaccines, cell therapies, traditional Chinese medicine and other methods are in clinical trials. Liver injury is a common complication of patients receiving COVID-19 treatment and its possible high incidence may affect the outcome of the disease. The pathogenesis of COVID-19 combined with liver injury in existing studies is still unclear, and relevant guidelines and expert consensuses are insufficient for clinical diagnosis and treatment. Therefore, the relevant progress and issues are now reviewed here.

[Efficacy and peripheral immunity analysis of allogeneic natural killer cells therapy in patients with hepatocellular carcinoma]

OBJECTIVE

To evaluate the safety and efficacy of allogeneic natural killer (NK) cells in the treatment of primary hepatocellular carcinoma (HCC), and to elucidate the mechanism of NK cells therapy.

METHODS

Twenty-one patients with primary HCC treated with allogeneic NK cells at the Fifth Medical Center of the PLA General Hospital were followed up for 1 year. Peripheral blood mononuclear cells (PBMCs) were isolated from patient-related donors and cultured in vitro for 15 days and infused to the patients in two consecutive days. Clinical data and laboratory data were collected and analyzed, including survival, clinical features, imaging changes, hematology, immunology, and biochemical indicators to evaluate the safety and efficacy of allogeneic NK cell therapy. The changes of peripheral blood lymphocyte subsets after treatment were also analyzed to explore the possible anti-tumor mechanisms.

RESULTS

(1) Of the 21 patients with primary HCC, 11 patients were treated once, 5 patients were treated twice, and 5 patients were treated 3 times. After allogeneic NK cells infusion, 10 patients had fever, 1 patient had slight hepatalgia and 1 patient had slight headache, no other adverse events occurred including acute and chronic graft-versus-host disease (GVHD). They resolved spontaneously within 8 hours without other treatment. (2) The total disease control rate was 76.2% during one-year follow-up. Among them, the patients with Barcelona clinic liver cancer (BCLC) stage A had a disease control rate of 100%, stable disease (SD) in 10 cases; BCLC stage B patients had a disease control rate of 60%, partial response (PR) in 1 case, and SD 2 in cases; BCLC stage C patients had a disease control rate of 50%, complete response (CR) in 1 case, and 2 cases of PR. (3) The frequencies of NK cells and CD8+ T cells in peripheral blood were significantly lower than that before at 24 hours after treatment, and the frequencies of CD4+ T cells and CD4/CD8 were significantly higher than the baseline.

CONCLUSION

Allogeneic NK cells have good safety and efficacy in the treatment of primary HCC. The anti-tumor effect of the allogeneic NK cells may play an important role in the activation of the patient's natural immune system and delay disease progression, suggesting that allogeneic NK cells combined with sorafenib may be a very effective treatment for advanced HCC, and further large-sample multicenter randomized controlled clinical trials are needed to validate this result.

[Analysis of the effects of different nutritional support methods on postoperative recovery in patients with gastric cancer]

Objective: To assess the effects of different nutritional support methods on postoperative recovery in patients with gastric cancer. Methods: 98 patients who received radical gastrectomy were divided into three groups: parenteral nutrition group (PN group) (n=36), early enteral nutrition group (EEN group) (n=33) and early oral feeding group (EON group) (n=29). Tolerance of enteral nutrition, postoperative recovery and economic indicators were compared. Results: The number of laparoscopic-assisted surgeries was 18, 17 and 25 in PN group, EEN group and EON group, respectively. There was no significant difference in sex, age and body mass index(BMI) among the three groups. Gastrointestinal function recovered slowly in 3 cases, including 2 cases in EEN group and 1 case in EON group. 1 case in EON group had abdominal hemorrhage. Median postoperative hospital stay in PN, EEN and EON group was 11.0, 11.0 and 8.0 days respectively, and significant reduction can be found in EON group(P<0.001). The complication rates were 30.5% (11 cases), 12.1% (4 cases), and 13.8% (4 cases), respectively, with no statistically significant difference(P=0.102). The median nutritional support costs for PN group, EEN group, and EON group were 4 543.3, 974.2, and 265.0 yuan, respectively. The median albumin consumption was 90.0, 40.0, and 0 g, respectively. The EON groups were significantly lower (P<0.001). The results of the laparoscopic assisted subgroup and the ones of whole group were consistent. Conclusion: Compared with parenteral nutrition and early enteral nutrition, early oral feeding can reduce the amount of albumin consumption, decrease the cost of nutrition support and shorten the average hospital stay after surgey without increasing the incidence of complications.

[Comparison of short-term outcomes of laparoscopy-assisted and totally laparoscopic distal gastrectomy for gastric cancer]

Objective: To assess the safety, feasibility and short-term outcome of totally laparoscopic distal gastrectomy(TLDG). Methods: Seventy-five patients who underwent laparoscopic distal gastrectomy in Cancer Hospital of Chinese Academy of Medical Science between August 2015 and April 2018 were enrolled in this study. A total of 46 laparoscopy-assisted distal gastrectomy (LADG) cases and 29 TLDG cases were included. The Short-term outcomes and safeties of the two groups were compared. Results: The operation time of TLDG group was significantly longer than that of LADG group (207±41 vs. 156±34 min, P<0.001), while the length of wound was shorter in the TLDG group (3.6±0.6 vs. 5.8±0.8 cm, P<0.001). The time to first flatus in TLDG group was (3.3±0.6) days, significantly shorter than (3.7±0.8) days in LADG group (P=0.034). There were no significant differences between the two groups in the estimated blood loss, intraoperative blood transfusion, extraction of gastric tube, drainage tube removal, interval of the first time to eat semi-liquid food, postoperative hospital stays, surgical complications, number of retrieved lymph nodes, proximal and distal resection margin lengths (all P>0.05). The white blood cell count at postoperative day 1 in the TLDG group was (10.96±1.96) ×10(9)/L, significantly lower than (12.49±3.46)×10(9)/L of the LADG group (P=0.017). While the CRP level at postoperative day 1 in the TLDG group were lower than that of LADG group, no statistical difference was observed (P=0.072). Conclusions: Our study shows that TLDG is safe and feasible. TLDG has better cosmesis, less blood loss, and faster recovery compared to LADG.

Enhanced magnetic circular dichroism by subradiant plasmonic mode in symmetric graphene oligomers at low static magnetic fields

Giant magnetic circular dichroism (MCD) that shows a different response to incident wave with left or right-handed circular polarization under external magnetic field is promising for magneto-optical sensing, revealing symmetry and degeneracy information of electronic states. However, traditional methods and materials that are used to obtain significant MCD involve highly strong external magnetic field. Based on the excitation of subradiant plasmonic mode and Fano resonance in graphene oligomers in the mid-infrared region, we numerically demonstrate that MCD is enhanced three times larger than the previously reported method, based on the resonance of electric dipole plasmonic mode. This giant MCD is attributed to the remarkably different excitation efficiency of subdradiant plasmonic mode due to the interparticle coupling under left or right-handed circular polarization incidence and external magnetic field. Our results offer an effective mechanism to enhance MCD signal at the nanoscale, which facilitates the sensing, spintronic, nanophotonics and other such fields.

[Efficacy of Weitan Waifu patch on the postsurgical gastroparesis syndrome of gastrointestinal cancer: a multi-center trial]

Objective: To investigate the safety and efficacy of the Weitan Waifu patch on the postsurgical gastroparesis syndrome (PGS) of gastrointestinal cancer. Methods: The multi-center, double-blind, randomized controlled trial was conducted with superiority design. Patients with PGS of gastrointestinal cancer diagnosed in 4 AAA hospitals and the abdominal symptom manifested as cold syndrome by Chinese local syndrome differentiation were recruited. These patients were randomly divided into two groups according to 1∶1 proportion. Placebo or Weitan Waifu patch was applied in control group or intervention group, respectively, based on the basic treatments, including nutrition support, gastrointestinal decompression, promoting gastric dynamics medicine.Two acupuncture points (Zhongwan and Shenque) were stuck with placebo in control group or patch in treatment group. The intervention course was 14 days or reached the effective standard. Results: From July 15, 2013 to Jun 3, 2015, 128 participants were recruited and 120 eligible cases were included in the full analysis set (FAS), and 60 cases in each group. 88 cases were included in the per-protocol set (PPS), including 45 cases in the treatment group and 43 cases in the control group. In the FAS, the clinical effective rate in the treatment group was 68.3%, significantly superior than 41.7% of the control group (P=0.003). The medium time of effective therapy in the treatment group was 8 days, significantly shorter than 10 days in the control group (P=0.017). In the FAS, 3 adverse events occurred in the treatment group, including mild to moderate decrustation, pruritus and nausea. The incidence rate of adverse events was 5.0% (3/60) and these symptoms were spontaneously remitted after drug withdrawal. No severe adverse events were observed in the control group. There was no significant difference between these two groups (P=0.244). Conclusion: Weitan Waifu patch is a safely and effectively therapeutic method for patients with PGS (cold syndrome) of gastroenterological cancer. Trial registration: International Standard Randomized Controlled Trial Number Register, ISRCTN18291857.

Myocardial protective effects of dexmedetomidine in patients undergoing cardiac surgery: A meta-analysis and systematic review

Arrhythmias are the common complications following cardiac surgery and contribute to hemodynamic instability, cognitive impairment, thromboembolic events, and congestive heart failure. Prevention of atrial fibrillation following cardiac surgery reduces morbidity and among the many available preventive approaches dexmedetomidine shows many positive effects on cardiovascular stability. Even though many studies indicated the beneficial effects of dexmedetomidine, the power of the analysis and conclusion of these studies is rather weak due to relatively smaller number of patients in these studies. In the present meta-analysis, we included a large number of patients, both children and adults, undergoing cardiac surgery, to address the efficacy of dexmedetomidine. Several databases were searched to identify clinical studies comparing the efficacy of dexmedetomidine in myocardial protection in patients undergoing cardiac surgery. Cardiac function related parameters including heart rate, blood pressure, tachycardia, arrhthmias, and bradycardia were measured. In accordance with the selection criteria, a total of 18 studies published between 2003 and 2016, with a total of 19,225 patients were included in the present meta-analysis. Dosage of dexmedetomidine was in the range of 0.5-1 µg/kg body weight loading followed by continuous infusion at a rate of 0.2-0.7 µg/kg/h. Dexmedetomidine treatment was found to lower heart rate, systolic blood pressure, incidence of tachycardia and arrhythmias in both adult and pediatric patients, but elevated the risk of bradycardia. In conclusion, results of this meta-analysis indicate that dexmedetomidine is an efficacious cardioprotective drug in adults and children undergoing cardiac surgery.

Identification of key micro-organisms involved in Douchi fermentation by statistical analysis and their use in an experimental fermentation

AIMS

To screen and identify safe micro-organisms used during Douchi fermentation, and verify the feasibility of producing high-quality Douchi using these identified micro-organisms.

METHODS AND RESULTS

PCR-denaturing gradient gel electrophoresis (DGGE) and automatic amino-acid analyser were used to investigate the microbial diversity and free amino acids (FAAs) content of 10 commercial Douchi samples. The correlations between microbial communities and FAAs were analysed by statistical analysis. Ten strains with significant positive correlation were identified. Then an experiment on Douchi fermentation by identified strains was carried out, and the nutritional composition in Douchi was analysed. Results showed that FAAs and relative content of isoflavone aglycones in verification Douchi samples were generally higher than those in commercial Douchi samples.

CONCLUSIONS

Our study indicated that fungi, yeasts, Bacillus and lactic acid bacteria were the key players in Douchi fermentation, and with identified probiotic micro-organisms participating in fermentation, a higher quality Douchi product was produced.

SIGNIFICANCE AND IMPACT OF THE STUDY

This is the first report to analyse and confirm the key micro-organisms during Douchi fermentation by statistical analysis. This work proves fermentation micro-organisms to be the key influencing factor of Douchi quality, and demonstrates the feasibility of fermenting Douchi using identified starter micro-organisms.

E2F-1 overexpression inhibits human gastric cancer MGC-803 cell growth in vivo

AIM: To evaluate the influence of E2F-1 on the growth of human gastric cancer (GC) cells in vivo and the mechanism involved.

METHODS: E2F-1 recombinant lentiviral vectors were injected into xenograft tumors of MGC-803 cells in nude mice, and then tumor growth was investigated. Overexpression of transcription factor E2F-1 was assessed by reverse transcription-polymerase chain reaction (RT-PCR) and Western blotting analysis. Apoptosis rates were determined using a terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL) assay. Expression levels of certain cell cycle regulators and apoptosis-related proteins, such as Bax, survivin, Bcl-2, cyclin D1, S-phase kinase-associated protein 2, and c-Myc were examined by Western blotting and RT-PCR.

RESULTS: Xenograft tumors of MGC-803 cells in nude mice injected with E2F-1 recombinant lentiviral vectors stably overexpressed the E2F-1 gene as measured by semi-quantitative RT-PCR (relative mRNA expression: 0.10 ± 0.02 vs 0.05 ± 0.02 for control vector and 0.06 ± 0.03 for no infection; both P < 0.01) and Western blotting (relative protein expression: 1.90 ± 0.05 vs 1.10 ± 0.03 in control vector infected and 1.11 ± 0.02 for no infection; both P < 0.01). The growth-curve of tumor volumes revealed that infection with E2F-1 recombinant lentiviral vectors significantly inhibited the growth of human GC xenografts (2.81 ± 1.02 vs 6.18 ± 1.15 in control vector infected and 5.87 ± 1.23 with no infection; both P < 0.05) at 15 d after treatment. TUNEL analysis demonstrated that E2F-1 overexpression promoted tumor cell apoptosis (18.6% ± 2.3% vs 6.7% ± 1.2% in control vector infected 6.3% ± 1.2% for no infection; both P < 0.05). Furthermore, lentiviral vector-mediated E2F-1 overexpression increased the expression of Bax and suppressed survivin, Bcl-2, cyclin D1, Skp2, and c-Myc expression in tumor tissue.

CONCLUSION: E2F-1 inhibits growth of GC cells via regulating multiple signaling pathways, and may play an important role in targeted therapy for GC.

Overexpression of CDX2 in gastric cancer cells promotes the development of multidrug resistance

Modulator of multidrug resistance (MDR) gene is a direct transcriptional target of CDX2. However, we still speculate whether CDX2 affects MDR through other ways. In this study, a cisplatin-resistant (SGC7901/DDP) and a 5-fluoro-2, 4(1h,3h)pyrimidinedione-resistant (BGC823/5-FU) gastric cancer cell line with stable overexpression of CDX2 were established. The influence of overexpression of CDX2 on MDR was assessed by measuring IC50 of SGC7901/DDP and BGC823/5-FU cells to cisplatin, doxorubicin, and 5-fluorouracil, rate of doxorubicin efflux, apoptosis, and cell cycle progression detected by flow cytometry. In addition, we determined the in vivo effects of CDX2-overexpression lentiviral vector (LV-CDX2-GFP) on tumor size, and apoptotic cells in tumor tissues were detected by deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling and hematoxylin and eosin staining. Results showed that LV-CDX2-GFP led to up-regulation of CDX2 mRNA and protein expression. It significantly inhibited the sensitivity of SGC7901/DDP and BGC823/5-FU cells to cisplatin, doxorubicin, and 5-fluorouracil. Flow cytometry confirmed that the percentage of apoptotic cells decreased after CDX2 up-regulation. This notion was further supported by the observation that up-regulation of CDX2 blocked entry into the M-phase of the cell cycle. Furthermore, up-regulation of CDX2 significantly decreased intracellular accumulation of doxorubicin. In molecular studies, quantitative reverse-transcriptase real-time polymerase chain reaction and western blotting revealed that CDX2 up-regulation could suppress expression of Caspase-3, Caspase-9 and PTEN, and increased the expression of MDR1, MRP, mTOR, HIF-1α.

Reversal of multidrug resistance in gastric cancer cells by E2F-1 downregulation in vitro and in vivo

Transcription Factor E2F-1 plays a critical role in cell cycle regulation and other biological processes in cells. However whether or not it is involved in the multi-drug resistance (MDR) process of gastric cancer has not been fully elucidated yet. To explore the role of E2F-1 in the MDR process of gastric cancer in vitro and in vivo, a cisplatin-resistant gastric cancer cell line with stable downregulation of E2F-1 was established. E2F-1 shRNA led to downregulation of endogenous E2F-1 mRNA and protein. It significantly promoted the sensitivity of SGC7901/DDP cells to cisplatin, doxorubicin, and fluorouracil. Flow cytometry confirmed that the percentage of apoptotic cells increased after E2F-1 downregulation. This notion was further supported by the observation that downregulation of E2F-1 blocked entry into the S-phase of the cell cycle. Furthermore, downregulation of E2F-1 significantly increased intracellular accumulation of doxorubicin. In addition, we determined the in vivo effects of E2F-1 small interfering RNA (shRNA) on tumor size, and apoptotic cells in tumor tissues were detected by deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling and hematoxylin and eosin staining. In molecular studies, semiquantitative RT-PCR and western blotting revealed that E2F-1 downregulation could inhibit expression of MDR1, MRP, Bcl-2/Bax, c-Myc, Skp2, Survivin, and Cyclin D1.

IN CONCLUSION

E2F-1 may be involved in regulating multiple signaling pathways in reversing MDR, suggesting that E2F-1 may represent a novel target for gastric cancer therapy.

Amplified spontaneous emission via the coupling between Fabry-Perot cavity and surface plasmon polariton modes

We demonstrated amplified spontaneous emission by embedding dye molecules within a dielectric layer of a metal-dielectric-metal subwavelength structure. It was reinforced when a strong coupling occurred between the Fabry-Perot mode supported by the dielectric layer and the surface plasmon polariton mode supported by the adjacent metallic grating. Here, we adjust the two mode interaction via tuning the depth of the metallic grating grooves. The stronger the interaction, the smaller the full width at half-maximum of the emission spectra and the lower the threshold of the amplified spontaneous emission.

New insights into the functions and localization of the homeotic gene CDX2 in gastric cancer

Gastric cancer is one of the most frequent cancers, and it ranks the third most common cancer in China. The most recently caudal-related homeobox transcription factor 2 (CDX2) is expressed in a large number of human gastrointestinal cancers. In addition, gastric epithelial cell mutations in CDX2 result in tumor promotion, which is characterized by cellular drug resistance and a high proclivity for developing cancer. A series of publications over the past years suggests a mechanism by which CDX2 overexpression results in multidrug resistance. CDX2 appears to forward control regenerating IV and the multidrug resistance 1 expression signaling pathway for regulation of cell drug resistance.

Surface-enhanced fluorescence of a dye-doped polymer layer with plasmonic band edge tuning

We investigated experimentally the influence of 1D rectangular Au gratings on fluorescence. The formation of a bandgap in the dispersion relation is confirmed by our experiment. At the edge of this bandgap, the fluorescence of the dye can be strongly enhanced due to the surface plasmon polaritons' large density of states. By structural design we tuned the plasmonic band edges to the wavelength of the fluorescence of the dye molecules. An optimized Au grating structure with a duty ratio of 3/4 is found to achieve up to 120 times stronger fluorescence than that of a planar metal surface.

Reversal of multidrug resistance in gastric cancer cells by CDX2 downregulation

AIM: To explore the role of CDX2 in the multi-drug resistance (MDR) process of gastric cancer in vitro and in vivo.

METHODS: A cisplatin-resistant gastric cancer cell line with stable downregulation of CDX2 was established. mRNA and protein expression levels of CDX2, survivin, cyclin D1, and c-Myc were detected by western blotting and semi-quantitative reverse-transcriptase polymerase chain reaction (RT-PCR). The influence of downregulation of CDX2 on MDR was assessed by measuring IC50 of SGC7901/DDP cells to cisplatin, doxorubicin, and 5-fluorouracil, rate of doxorubicin efflux, apoptosis, and cell cycle progression detected by flow cytometry. In addition, we determined the in vivo effects of CDX2 small interfering RNA (siRNA) on tumor size, and apoptotic cells in tumor tissues were detected by deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling and hematoxylin and eosin staining.

RESULTS: CDX2 siRNA led to downregulation of endogenous CDX2 mRNA (0.31 ± 0.05 vs 1.10 ± 0.51, 0.31 ± 0.05 vs 1.05 ± 0.21, P = 0.003) and protein (0.12 ± 0.08 vs 0.51 ± 0.07, 0.12 ± 0.08 vs 0.55 ± 0.16, P = 2.57 × 10^-4) expression. It significantly promoted the sensitivity of SGC7901/DDP cells to cisplatin (0.12 ± 0.05 vs 0.33 ± 0.08, 0.12 ± 0.05 vs 0.39 ± 0.15, P = 0.001), doxorubicin (0.52 ± 0.13 vs 4.11 ± 1.25, 0.52 ± 0.13 vs 4.05 ± 1.44, P = 2.81 × 10^-4), and 5-fluorouracil (0.82 ± 0.13 vs 2.81 ± 0.51, 0.82 ± 0.13 vs 3.28 ± 1.03, P = 1.71 × 10^-4). Flow cytometry confirmed that the percentage of apoptotic cells increased after CDX2 downregulation (32.15% ± 2.15% vs 17.63% ± 3.16%, 32.15% ± 2.15% vs 19.3% ± 2.25%, P = 1.73 × 10^-6). This notion was further supported by the observation that downregulation of CDX2 blocked entry into the S-phase of the cell cycle (31.53% ± 3.78% vs 65.05% ± 7.25%, 31.53% ± 3.78% vs 62.27% ± 5.02%, P = 7.55 × 10^-7). Furthermore, downregulation of CDX2 significantly increased intracellular accumulation of doxorubicin (0.21 ± 0.06 vs 0.41 ± 0.11, 0.21 ± 0.06 vs 0.40 ± 0.08, P = 0.003). In molecular studies, semiquantitative RT-PCR and western blotting revealed that CDX2 downregulation could inhibit expression of c-Myc, survivin and cyclin D1.

CONCLUSION: CDX2 may be involved in regulating multiple signaling pathways in reversing MDR, suggesting that CDX2 may represent a novel target for gastric cancer therapy.

Lentivirus-mediated E2F-1 gene silencing enhances sensitivity of gastric carcinoma MGC-803 cells to compound ginseng and astragalus

AIM: To observe the effect of recombinant lentivirus-mediated E2F-1 gene silencing on sensitivity of gastric carcinoma MGC-803 cells to compound ginseng and astragalus.

METHODS: MGC-803 cells were plated and divided into four groups: a normal control group (medicine medium), a blank control group, a negative LV-RNAi control group (medicine medium + infection with empty lentiviral vector particles 2.0 × 10⁹ TU/mL) and an E2F-1-RNAi-LV group (medicine medium + infection with recombinant E2F-1 lentiviral particles 2.0 × 10⁹ TU/mL). The mRNA and protein expression levels of E2F1 were detected by RT-PCR and Western blot. Cell proliferation was detected by MTT assay. Cell colony formation was detected by Giemsa staining. Cell apoptosis was observed by flow cytometry, and cell migration was detected by cell scratch assay.

RESULTS: Infection with the recombinant lentiviral vector significantly decreased the protein and mRNA expression levels of E2F-1 compared to the two control groups (0.384 ± 0.036 vs 0.883 ± 0.051 and 0.923 ± 0.049, 0.220 ± 0.056 vs 0.729 ± 0.021 and 0.712 ± 0.037, P < 0.05). Compound ginseng and astragalus inhibited MGC-803 cell growth, induced cell apoptosis, and reduced cell colony formation and migration. Compared to the two control groups, the rates of reduced cell colony formation and cell apoptosis were significantly increased and the areas of cell colony formation and migration were significantly decreased in the E2F-1 gene silencing group (0.789 ± 0.013 vs 0.484 ± 0.060 and 0.454 ± 0.006, 0.383 ± 0.027 vs 0.114 ± 0.038 and 0.089 ± 0.051, 0.024 ± 0.003 vs 0.036 ± 0.004 and 0.052 ± 0.002, 0.553 ± 0.038 vs 0.897 ± 0.020 and 0.928 ± 0.051, P < 0.05).

CONCLUSION: Recombinant lentivirus-mediated E2F-1 gene silencing effectively enhances the sensitivity of MGC-803 cells to compound ginseng and astragalus.

Role of RNA interference in research of multidrug resistance in gastric cancer

Gastric cancer is one of the most common malignant tumors in the world. Chemotherapy is the main treatment for gastric cancer after operation. However, multidrug resistance of tumor cells always reduces its effectiveness and influences the prognosis of patients directly. For this reason, more and more scientific researchers have been dedicated to the in-depth study of multidrug resistance in gastric cancer. RNA interference allows specific and effective inhibition of the expression of target genes and has been gradually applied to gene treatment for multidrug resistance in gastric cancer. The widespread use of RNA interference in recent years has led to many achievements. This article aims to review the role of RNA interference in research of multidrug resistance in gastric cancer.

Prognostic significance of Cdx2 immunohistochemical expression in gastric cancer: a meta-analysis of published literatures

Cdx2 is a homeobox domain-containing transcription factor that is important in the development and differentiation of the intestinal cells, and served as a potential biomarker of tumor progression in early intestinal-type gastric cancer. However, its prognostic value and significance in gastric cancer remain controversial. A meta-analysis based on published studies was performed to obtain an accurate evaluation of the association between the presence of Cdx2-positive in clinical samples and clinical outcome. A total of 13 eligible retrospective cohort studies with 1513 patients were included. Cdx2-positive cases were significantly associated with higher male-to-female ratio (RR=1.27, 95% CI: 1.17-1.38, P<0.00001 fixed-effect), lower (I+II) clinical stage (RR=1.63, 95% CI: 1.42-1.87, P<0.00001 fixed-effect), better histologic differentiation (RR=1.54, 95% CI: 1.34-1.76, P<0.00001 fixed-effect), and lower rate of vascular invasion (RR=1.23, 95% CI: 1.08-1.41, P=0.002 fixed-effect) and lymph node metastasis (RR=1.52, 95% CI: 1.33-1.73, P<0.00001 fixed-effect), as well as higher 5-year survival rate (HR=2.22, 95% CI: 1.78-2.75, P<0.00001 fixed-effect). However, the presence of Cdx2 was not associated with tumor size. In summary, Cdx2 is a prognostic factor in gastric cancer, which acts as a marker of good outcome in patients with gastric cancer. Further clinical studies are needed to confirm the role of Cdx2 in clinical practice.

siRNA targeting of Cdx2 inhibits growth of human gastric cancer MGC-803 cells

AIM: To investigate the effects of small interference RNA (siRNA) targeting of Cdx2 on human gastric cancer MGC-803 cells in vitro and in vivo.

METHODS: The recombinant pSilencer 4.1-Cdx2 siRNA plasmids were constructed and transfected into gastric cancer MGC-803 cells in vitro. The stable transfectants were selected. The effects of Cdx2 siRNA on growth, proliferation, cell cycle, apoptosis, migration and invasiveness of human gastric cancer MGC-803 cells were evaluated and the expression of phosphatase and tensin homolog (PTEN), caspase-9 and caspase-3 was observed in vitro by reverse transcription polymerase chain reaction (RT-PCR) and Western blotting analysis. We also investigated the effect of Cdx2 siRNA on growth of MGC-803 cells in nude mice in vivo.

RESULTS: Cdx2 siRNA led to inhibition of endogenous Cdx2 mRNA and protein expression as determined by RT-PCR and Western blotting analysis. Cdx2 siRNA significantly inhibited cell growth and proliferation, blocked entry into the S-phase of the cell cycle, induced cell apoptosis, and reduced the motility and invasion of MGC-803 cells. Cdx2 siRNA also increased PTEN expression, and activated caspase-9 and caspase-3 in MGC-803 cells in vitro . In addition, siRNA targeting of Cdx2 inhibited the growth of MGC-803 cells and promoted tumor cell apoptosis in vivo in nude mice tumor models.

CONCLUSION: Cdx2 was involved in regulating pro-gression of human gastric cancer cells MGC-803. Manipulation of Cdx2 expression may be a potential therapeutic strategy for gastric cancer.

[Effects of E2F-1 overexpression on apoptosis of gastric cancer cells and expressions of apoptosis-related genes]

BACKGROUND AND OBJECTIVE

E2F transcription factor 1 (E2F-1) is an important transcription factor in cell cycle. This study was to investigate the effects of E2F-1 overexpression on apoptosis of gastric cancer MGC-803 cells and expressions of the downstream genes.

METHODS

The apoptotic rates were measured by flow cytometry in MGC-803/E2F-1 cells, MGC-803/EV cells or untransfected MGC-803 cells. The total RNA was extracted from MGC-803/E2F-1 cells or MGC-803 cells, and cDNA was obtained by RT-PCR. Fluorescent (fluorescence exchange clip) probes marked by Cy5 and Cy3 were hybridized with gene chips containing 21522 human genes. Subsequently, the two signal images were scanned by Lux Scan 10K/A dual pathways laser scanner and analyzed by LuxScan3.0 image analysis software. RT-PCR was used to verify the target genes.

RESULTS

The apoptotic rate of MGC-803/E2F-1 cells [(8.40+/-0.91)%] was higher than that of MGC-803/EV [(4.53+/-0.61)%] and MGC-803 cells [(4.97+/-0.47)%]. Fifteen differentially expressed apoptosis-related genes were detected, 4 of which were up-expressed and 11 were down-expressed genes, and the same results were verified by RT-PCR.

CONCLUSION

Overexpression of E2F-1 accelerates apoptosis of gastric carcinoma MGC-803 cells, which may be related to the 15 differentially expressed genes.

Construction and identification of a lentiviral vector for RNA interference of the Cdx2 gene

AIM: To construct a lentiviral vector for RNA interference (RNAi) of the caudal-related homeobox 2 (Cdx2) gene.

METHODS: A pair of complementary small hairpin RNA (shRNA) oligonucleotides targeting the Cdx2 gene were designed, synthesized, annealed and inserted into linearized pLentiLox3.7 vector. The recombinant plasmid was identified by double restriction digestion with Xba I/Not I and DNA sequencing. The recombinant plasmid and a lentivirus packaging mix were co-transfected into 293T cells to obtain packaged lentivirus particles. Viral titer was then determined.

RESULTS: Double restriction digestion analysis and DNA sequencing showed that the shRNA sequence was successfully inserted into the pLentiLox3.7 vector. The recombinant lentiviral vector harboring shRNA targeting the Cdx2 gene was successfully transfected into 293T cells. The recombinant lentivirus harvested from 293T cells had a titer of 5×107 TU/mL.

CONCLUSION: A lentiviral shRNA expression vector targeting the Cdx2 gene is successfully constructed and can be used for further study of the role of the Cdx2 gene in the pathogenesis of gastric cancer.

Effects of E2F-1 gene overexpression on gastric cancer cell dynamics

AIM: To understand the effect of E2F-1's over-expression on gastric cancer cell proliferation, growth and cell cycle and to investigate the molecular mechanism of E2F-1's influence on gastric cancer cell dynamics.

METHODS: The MGC-803/ E2F-1 (experimental group) gastric cancer cells which were stably transfected with E2F-1, and containing unpossessed carriers (negative control group), and the cells without transfection were performed MTT test to draw growing curve, and to compute cell proliferation rate. Cell cycles were examined by flow cytometry. The total RNA was extracted, and the cDNA was obtained using reverse transcription polymerase chain reaction (RT-PCR), and then the fluorescent probes were hybridized with gene chip containing 21 522 human 22K gene expression profiles. Subsequently, the two signal images were scanned by Lux Scan 10K/A dual pathways laser scanner and analyzed by LuxScan 3.0 image analysis software.

RESULTS: Compared with two control groups, the growth of the MGC-803 gastric cancer cells stably transfected with E2F-1 was obviously inhibited, and proliferation rate was decreased (26.61% ± 5.19% vs 93.4% ± 10.29%, 100% ± 0.00%, both P < 0.05), cell cycle staged in periods of G₀/G₁. Of the 21 522 target genes, there were 20 cell proliferation, growth and cell cycle-related differential expression ones. Of the 20 genes, 9 were up-regulated and 11 were down-regulated.

CONCLUSION: E2F-1 overexpression inhibits gastric cancer cell proliferation, growth and cell cycle, then cell cycle remains in periods of G₀/G₁, and perhaps the molecular mechanism has direct relationship with the 20 selected differential expression genes.

[Inhibitory effects of transcription factor E2F-1 siRNA on invasion and proliferation of gastric cancer cell line MGC803]

BACKGROUND & OBJECTIVE

As an important regulatory factor of cell cycle, transcription factor E2F-1 is closely related to tumorigenesis. This study was to investigate the effects of E2F-1 small interfering RNA (siRNA) on invasion and proliferation of human gastric cancer MGC803 cells.

METHODS

E2F-1 siRNA vector containing short hairpin structure was transfected into MGC803 cells. Untransfected and pSilencer4.1-negative-transfected cells were used as controls. The expression of E2F-1 was detected by reverse transcription-polymerase chain reaction (RT-PCR) and Western blot. Cell matrigel invasion assay and cloning assay were used to detect the invasion and proliferation of MGC803 cells after E2F-1 siRNA transfection.

RESULTS

At 48 h after E2F-1 siRNA transfection, the mRNA level of E2F-1 was down-regulated by over 90.0% of controls; the protein level of E2F-1 was down-regulated by 79.6% of negative control and by 81.5% of empty control. The number of migrated cells was significantly smaller in E2F-1 siRNA group than in negative and empty control groups (18.0+/-2.6 vs. 48.0+/-4.6 and 54.0+/-5.6, P<0.05). The number of cell clones was also significantly smaller in E2F-1 siRNA group than in negative and empty control groups (46.0+/-2.0 vs. 122.3+/-1.5 and 128.7+/-2.1, P<0.05)

CONCLUSION

E2F-1 siRNA could down-regulate E2F-1 expression in human gastric cancer MGC803 cells and suppress its invasion and proliferation to some extent.

[Construction of a eukaryotic vector expressing E2F-1 Gene and its effect on proliferation of gastric cancer cell line MKN-45]

BACKGROUND & OBJECTIVE

E2F-1 is overexpressed in many tumors and functions as an oncogene or tumor suppressor gene. This study was to construct the recombinant eukaryotic vector expressing E2F-1 cDNA, and explore the effect of E2F-1 overexpression on the proliferation of human gastric carcinoma cell line MKN-45.

METHODS

The fragment of E2F-1 gene was amplified by polymerase chain reaction (PCR). A eukaryotic vector expressing E2F-1 (pCMV-E2F1-HA) was constructed with pCMV-HA, and transfected into COS-7 cells to identify whether E2F-1 was successfully subcloned into the eukaryotic vector. pCMV-E2F1-HA was transfected into MKN-45 cells. The expression of E2F-1 in MKN-45 cells was detected by Western blot. The proliferation of MKN-45 cells was observed by colony formation assay and MTS method. Cell cycle was analyzed by flow cytometry (FCM).

RESULTS

Recombinant plasmid pCMV-E2F1-HA was successfully constructed and transfected into COS-7 and MKN-45 cells. MKN-45 cell clones were significantly fewer in pCMV-E2F1-HA group than in pCMV-HA group (4.7+/-1.8 vs. 30.2+/-6.7, P<0.01). The proliferation rate of MKN-45 cells was significantly lower in pCMV-E2F1-HA group (73.5% on Day 5, 63.5% on Day 6, 56.1% on Day 7) than in pCMV-HA group (100%, P<0.01). The G0/G1 phase proportion of MKN-45 cells was significantly higher in pCMV-E2F1-HA group than in pCMV-HA group (71.4% vs. 59.7%, P<0.05); the S phase proportion was significantly lower in pCMV-E2F1-HA group than in pCMV-HA group (18.7% vs. 30.7%, P<0.05).

CONCLUSION

Overexpression of E2F-1 suppresses the proliferation of gastric cancer MKN-45 cells.

Microcalorimetric study on the growth and metabolism of microencapsulated microbial cell culture

The rate of heat output is one of the suitable measurements of metabolic activity of the organism or its parts, down to the cellular or even the sub-cellular levels. In this paper, microcalorimetry was first applied to study the metabolic activity of microbial in both alginate-polylysine-alginate and alginate-chitosan-alginate microencapsulated cultures as well as in free non-encapsulated culture. The organisms used for the measurements were Escherichia coli and Saccharomyces cerevisiae. As a result of this work, it was found that, despite E. coli cell in free non-encapsulated culture has the highest metabolic rate due to the highest value of heat output, the proliferation of the cells terminates quickly with a lowest biomass formed. And we found also an obviously longer stationary phase in microencapsulated culture. As far as S. cerevisiae was concerned, it was found that there was also the highest value of heat output in free non-encapsulated culture, but the cell density was lower than that in microencapsulated culture. On account of the microcalorimetric and metabolic measurements, it can be concluded that more substrate can be used to convert to biomass in microencapsulated culture which means a higher biomass yield existed.

Production of recombinant androgen receptor in a heterologous expression system

To facilitate detailed studies of androgen receptor, we have produced a full-length receptor protein and some of its deletion mutants in Spodoptera frugiperda (Sf9) insect cells, using the baculovirus expression system. Recombinant baculovirus DNA-infected Sf9 cells expressed these proteins in very high quantities, which represented as much as 30-40% of total insect cell protein at 72 h after infection. Only &lt; 1% of the recombinant protein was soluble in low-salt buffers; the majority formed electron-dense cytoplasmic aggregates 30-40 nm in diameter. These aggregates could be solubilized in 6 mol/L guanidine HCl, and biologically active receptor was generated by diluting the guanidine HCl preparation 20- to 50-fold. The full-length receptor, expressed either in a soluble or aggregated form, had characteristics typical of a native receptor: it bound steroids with high affinity and specificity, interacted with DNA in a sequence-specific fashion, and was recognized by domain-specific receptor antibodies. Androgen-receptor protein purified to homogeneity in guanidine HCl required the presence of Zn2+ ions during the refolding to reconstitute its DNA-binding form; ZnCl2 was not, however, needed to restore the receptor's steroid-binding activity.

Production of recombinant androgen receptor in a heterologous expression system

To facilitate detailed studies of androgen receptor, we have produced a full-length receptor protein and some of its deletion mutants in Spodoptera frugiperda (Sf9) insect cells, using the baculovirus expression system. Recombinant baculovirus DNA-infected Sf9 cells expressed these proteins in very high quantities, which represented as much as 30-40% of total insect cell protein at 72 h after infection. Only < 1% of the recombinant protein was soluble in low-salt buffers; the majority formed electron-dense cytoplasmic aggregates 30-40 nm in diameter. These aggregates could be solubilized in 6 mol/L guanidine HCl, and biologically active receptor was generated by diluting the guanidine HCl preparation 20- to 50-fold. The full-length receptor, expressed either in a soluble or aggregated form, had characteristics typical of a native receptor: it bound steroids with high affinity and specificity, interacted with DNA in a sequence-specific fashion, and was recognized by domain-specific receptor antibodies. Androgen-receptor protein purified to homogeneity in guanidine HCl required the presence of Zn2+ ions during the refolding to reconstitute its DNA-binding form; ZnCl2 was not, however, needed to restore the receptor's steroid-binding activity.

Expression of androgen receptor in insect cells. Purification of the receptor and renaturation of its steroid- and DNA-binding functions

A full-length rat androgen receptor cDNA was used to produce a recombinant baculovirus (AcrAR) by homologous recombination. Spodoptera frugiperda (Sf9) cells infected with this virus expressed a 110-kDa polypeptide that amounted up to about one-third of total cell protein. Studies with AR antibodies confirmed that this protein was indeed rAR. Only a minor portion of the recombinant AR was soluble in buffers without ionic detergents, but its complete solubilization was achieved in 6 M guanidine HCl (GdnHCl). Electron microscopy of cell pellets revealed that AR was localized to electron-dense cytoplasmic aggregates. The soluble cytosolic receptor was biologically active, in that it bound [3H]mibolerone with high affinity and specificity and interacted with an androgen-responsive element. The functions of the GdnHCl-solubilized AR were partially restored by a 20-50-fold dilution. The solubilized receptor was purified to an apparent homogeneity in a single step by gel filtration on a Sephacryl S-400 column in the presence of 6 M GdnHCl. The homogeneous AR protein could be renatured to bind [3H]mibolerone, interact specifically with a DNA element, and be recognized by receptor antibodies. Receptor-DNA interaction was stabilized by an antibody directed against the N-terminal part and abolished by an antibody against the hinge region of the receptor Zn2+ ions were essential for the purified receptor to refold into a specific DNA-binding form during the renaturation, with the optimal ZnCl2 concentration being 50-100 microM depending on the buffer conditions. Cd2+ ions were also capable of restoring the receptor's DNA-binding activity and did so at concentrations 10-fold lower than those of the Zn2+ ions.

Effects of truncations of the cytoplasmic tail of the luteinizing hormone/chorionic gonadotropin receptor on receptor-mediated hormone internalization

The LH/CG receptor is a member of the family of G protein-coupled receptors and consists of a large N-terminal extracellular domain (which is responsible for binding hormone) attached to a region that spans the plasma membrane seven times, ending with an intracellularly located C-terminus. Binding of LH or human CG (hCG) to the LH/CG receptor causes a stimulation of adenylyl cyclase, presumably via activation of Gs. The binding of hormone also leads to its subsequent internalization by receptor-mediated endocytosis. In order to investigate the role of the cytoplasmic tail of this receptor in these events, we prepared a series of mutants in which progressively larger portions of the cytoplasmic tail were deleted. Deletion of 58 amino acids from the C-terminus, in which only 11 cytoplasmic residues remain, resulted in a receptor that was not expressed on the plasma membrane. Receptors rat LHR (rLHR)-t653 and rLHR-t631, in which 21 or 43 amino acids were removed, respectively, were properly expressed. These results suggest that a region(s) between residues 616 and 631 of the rLH/CG receptor are required for proper insertion and/or targeting of the receptor into the plasma membrane. Cells expressing rLHR-t653 or rLHR-t631 bound hCG with the same high affinity as cells expressing the full-length receptor, and basal levels of cAMP were the same among the cells. However, cells expressing the truncated receptors responded to hCG with approximately 2-fold greater levels of maximal cAMP accumulation than cells expressing the full-length receptor. Deletion of up to 43 amino acids from the C-terminus of the rLH/CG receptor had no deleterious effect on hCG internalization. In fact, mutants lacking 21 and 43 amino acids exhibited progressively faster rates of hCG internalization as compared to the full-length receptor. Once internalized, hCG was also degraded at a faster rate in cells expressing the truncated LH/CG receptors. Since hCG-stimulated cAMP stimulation and hCG internalization are retained by rLHR-t631, it can be concluded that the residues, not necessarily the same, required for these functions reside within the 26 amino acids of the cytoplasmic tail closest to the seventh transmembrane helix and/or residues within the intracellular loops. Our data show, however, that both hCG-stimulated cAMP production and hCG internalization are enhanced by the removal of the distal portion of the cytoplasmic tail.

Extracellular domain of lutropin/choriogonadotropin receptor expressed in transfected cells binds choriogonadotropin with high affinity

The lutropin-choriogonadotropin (LH/CG) receptor is a cell surface receptor comprised of two domains of roughly equivalent size. The amino-terminal half of the receptor is relatively hydrophilic and is located extracellularly, whereas the carboxyl-terminal half of the receptor shares amino acid homology with other receptors that couple to G proteins and is similarly thought to span the plasma membrane seven times, ending with a relatively short carboxyl-terminal tail. In order to test the role of the extracellular domain in binding hormone, we constructed a mutated rat luteal LH/CG receptor cDNA (termed pCLHR-D2), which encodes for only the extracellular domain, and used it to transiently transfect human kidney 293 cells. Here we report that the expressed extracellular domain of the LH/CG receptor is capable of binding human CG with a high affinity, comparable with that of the full-length receptor. Thus, not only is the extracellular domain of the glycoprotein hormone receptors involved in binding hormone, but it alone is capable of conferring high affinity binding. Unexpectedly, it was also found that this truncated receptor is not secreted into the culture media but remains trapped within the cells.