Comparison of Efficacy and Safety of Different Second-line Therapies for Patients With Advanced Thymic Carcinoma

AIMS

Thymic carcinoma (TC) is a rare form of highly invasive tumors. Currently, the standard first-line therapy involves paclitaxel plus carboplatin treatment, while the recommended regimen for second-line therapy remains uncertain. The purpose of this study is to explore the second-line mode of TC patients.

MATERIALS AND METHODS

We evaluated the outcome of subjects with advanced TC between 2009 and 2023 in three medical centers, retrospectively. Tumor response was evaluated according to the Response Evaluation Criteria in Solid Tumors, version 1.1 (RECIST v1.1). Kaplan-Meier was used for calculating Progression-free survival (PFS) and overall survival (OS). The factors affecting survival in the real world were evaluated by Cox analysis.

RESULTS

Totally 136 patients were included in this study, the median PFS (mPFS) for all subjects was 5.97 months, and the median OS (mOS) was 25.03 months. According to patient's treatment modes, they are divided into monotherapy (n = 95) and combination therapy (n = 41), PFS manifested the difference between two groups (5.17 vs. 9.00 months, P = 0.043). OS also indicated a significant distinction (22.50 vs. 38.00 months, P = 0.017). Furthermore, there was a significant difference in PFS between patients using immunotherapy combined with chemotherapy and those with antivascular therapy (8.57 vs. 13.10 months, P = 0.047).

CONCLUSION

In the second-line therapy for advanced TC, the efficacy of combination therapy was better than monotherapy, especially for immunotherapy combined with antivascular therapy.

Derivation of no significant risk levels for three lower acrylates: Conclusions and recommendations from an expert panel

A panel of toxicology, mode of action (MOA), and cancer risk assessment experts was engaged to derive no-significant-risk-levels (NSRLs) for three lower acrylates: methyl acrylate (MA), ethyl acrylate (EA), and 2-ethylhexyl acrylate (2EHA) using the best available science, data, and methods. The review was structured as a five-round, modified Delphi format, a systematic process for collecting independent and deliberative input from panel members, and it included several procedural elements to reduce potential sources of bias and groupthink. Input from the panel for key decisions in the dose-response assessments resulted in NSRL values of 530 μg/day (330-800 μg/day), 640 μg/day (280-670 μg/day), and 1700 μg/day (1300-2700 μg/day) for MA, EA, and 2EHA, respectively. Novel to this approach were the use of nonneoplastic lesions reported at point of contact where tumors have been reported in laboratory rodents, along with nonlinear extrapolation to low doses (uncertainty factor approach) based upon panel recommendations. Confidence in these values is considered medium to high for exposures applied to the routes of exposure tested (inhalation for MA and EA, dermal for 2EHA), but confidence is considered lower when applied to other routes of exposure.

[Development and validation of risk behavior scale for in-home unintentional injury in urban children aged 0-6 years in China]

Objective: To develop and evaluate the reliability and validity of risk behavior scale for in-home unintentional injury in urban children aged 0-6 years in China. Methods: Through literature review, expert consultation and pre-survey, the final scale was determined with 10 dimensions and 54 items. A total of 1 104 children aged 0-6 years were randomly selected by using multi-stage stratified cluster sampling in the urban area of Changsha and their guardians were invited to participate in this questionnaire survey. The information about the basic characteristics, incidence of unintentional injury and risk behaviors of the children were collected. Cronbach's α coefficient and split-half reliability were used to evaluate the reliability of the scale. Pearson correlation coefficient, Spearman correlation coefficient and factor analysis were used to evaluate the content validity and structural validity of the scale respectively. The children were divided into two groups according to the incidence of unintentional injury, and t-test was used to analyze the discriminant validity of the scale. Results: The children risk behavior scale had 54 items in 10 dimensions. A total of 1 094 valid questionnaires were returned and the effective response rate was 99.09%. The incidence of unintentional injury in the children was 18.65% (204/1 104). The Cronbach's α coefficient of the scale was 0.94, and the split-half reliability was 0.87. The Pearson correlation coefficients between each dimension and the total scale were 0.50-0.84 (all P<0.001). A total of 11 common factors were extracted from the total scale, and the cumulative variance contribution rate was 56.52%. The average factor load of 54 items was more than 0.30. The fitting indexes of the scale were 0.06 for root mean square error of approximation, 0.78 for comparative fit index, 0.79 for goodness-of-fit index, and 0.77 for adjusted goodness-of-fit index. The children with injuries had higher scores than those without injuries, the difference was significant (P<0.001). Conclusion: The scale developed has good reliability and validity on assessing the risk behaviors of unintentional injury in urban children in China.

Circular RNA hsa_circ_0008003 facilitates tumorigenesis and development of non-small cell lung carcinoma via modulating miR-488/ZNF281 axis

As one of the most aggressive malignancies, non‐small cell lung carcinoma (NSCLC) has high risks of death. It has been demonstrated that circRNAs accelerate NSCLC progression, but the underlying molecular mechanisms of circRNAs in NSCLC were still obscure. In the first place, the circRNA microarray of NSCLC was investigated in this study, and hsa_circ_0008003 (circ‐0008003) was chosen as the research object. Then, it was unveiled that the expression of circ‐0008003 examined via qRT‐PCR was elevated in tumour tissues relative to the non‐tumour tissues, which was associated with TNM stage and lymphatic metastasis in NSCLC. Additionally, the prognosis of NSCLC patients with high circ‐0008003 level was poor. Besides, circ‐0008003 silencing dampened the invasion and proliferation of NSCLC cells. Next, according to the mechanistic studies, circ‐0008003 functioned as a ceRNA of ZNF281 in NSCLC by acting as the endogenous sponge for miR‐488, which was proved to be a tumour suppressor in NSCLC. Additionally, ZNF281 overexpression and miR‐488 suppression recovered the influences of repressed circ‐0008003 on NSCLC cellular processes. It was validated in this research that circ‐0008003 triggered tumour formation in NSCLC, which was adjusted via miR‐488/ZNF281 axis, casting a novel light on the resultful target for treating NSCLC and predicting the prognosis.

Hypoxic preconditioning BMSCs-exosomes inhibit cardiomyocyte apoptosis after acute myocardial infarction by upregulating microRNA-24

OBJECTIVE

To elucidate the regulatory effect of hypoxic preconditioning bone marrow mesenchymal stem cells (BMSCs)-exosomes on cardiomyocyte apoptosis in acute myocardial infarction (AMI) rats.

MATERIALS AND METHODS

BMSCs-derived exosomes were extracted by Exoquick method. Expressions of exosome surface markers were determined by Western blot. The AMI model in rats was established by LAD ligation. Rats were randomly assigned into sham group, AMI group, AMI+H-exo group and AMI+N-exo group. MicroRNA-24 expression in rat myocardium was detected at different time points. Subsequently, hypoxic preconditioning or normoxic preconditioning BMSCs-exosomes were intramyocardially injected into rats. Infarct size was calculated through TTC (triphenyltetrazolium chloride) staining. Cardiomyocyte apoptosis was accessed with Terminal Deoxynucleotidyl Transferase dUTP Nick-end Labeling (TUNEL). Heart function of AMI rats was evaluated by echocardiography. Protein expressions of apoptotic genes in rat myocardium were detected by Western blot.

RESULTS

The mRNA level of microRNA-24 was higher in H-exo group than N-exo group. Injection of hypoxic preconditioning BMSCs-exosomes markedly upregulated microRNA-24 level, reduced infarct size and improved cardiac function in AMI rats. Protein expressions of Bax, caspase-3 and cleaved-caspase-3 were downregulated by BMSCs-exosomes treatment. H9c2 cells showed upregulated microRNA-24 level and decreased apoptotic rate after incubation with hypoxic preconditioning BMSCs-exosomes. The above cellular performances were partially reversed by transfection of microRNA-24 inhibitor.

CONCLUSIONS

Hypoxic preconditioning BMSCs-exosomes inhibit cardiomyocyte apoptosis in AMI rats by upregulating microRNA-24.

[Clinical analysis of mediastinal lymph node dissection through sternotomy approach in the treatment of papillary thyroid carcinoma with mediastinal lymph node metastasis]

Objective: To investigate the rule of mediastinal lymph node metastasis of papillary thyroid carcinoma and the application of therapeutic mediastinal lymph node dissection through the sternotomy approach in the treatment of mediastinal lymph node metastasis of papillary thyroid carcinoma. Methods: All cases of papillary thyroid carcinoma with mediastinal lymph node metastasis treated through sternotomy cooperated by thoracic surgeons and head and neck surgeons from January 2006 to January 2017 in Cancer Hospital of Chinese Academy of Medical Sciences were included in this study. The distribution, metastasis rate, metastasis degree, surgical method, surgical complications and postoperative survival of patients with mediastinal lymph node metastasis were retrospectively analyzed. Results: A total of 31 patients (16 males and 15 females) with papillary thyroid cancer with mediastinal lymph node metastasis, with a median age of 46 (19-65) years, were enrolled in the group. Partial upper sternotomy was used in 28 cases, and total sternotomy was used in 3 cases. The mediastinal lymph nodes of papillary thyroid carcinoma metastasized farthest to the station 6, and the lymph node metastasis rate of each group from high to low was: 2R (61%), 1R (39%), 3A (39%), 1L (16%), 2L (10%), 4R (10%), 5 (3%) and 6 (3%). No metastasis was observed in station 3P, 4L and 7. In addition, the degree of lymph node metastasis at station 2R was the highest, reaching 35% (77/219). Extra-nodal invasion of mediastinal metastatic lymph nodes in thyroid papillary carcinoma is common (23%), easily fuses into masses (23%) and invades peripheral vascular nerves (26%). Up to 29% of blood transfusions are required during or after surgery due to oozing or bleeding (9/31). The 1-, 3-, 5-and 10-year survival rates of patients undergoing surgical treatment were 94%, 94%, 87% and 81%, respectively. Conclusion: Papillary thyroid carcinoma can metastasize to almost all mediastinal lymph nodes except station 3P, 4L and 7. Radical mediastinal lymph node dissection through sternotomy is an effective method for the treatment of mediastinal lymph node metastasis of thyroid papillary carcinoma.

[Development and performance test of the environment scale of unintentional injury in the home for children aged 0-6 years old in urban area of China]

Objective: To develop the environment scale of unintentional injury in the home for children aged 0-6 years living in urban area of China, and test its validity and reliability. Methods: The content of the environment scale was established through the literature review, expert consultation and pilot study. A total of 1 104 children aged 0-6 years in urban area of Changsha were enrolled in this study by using a multi-stage stratified cluster random sampling method. The questionnaire was used to collect the basic information of children, the incidence of unintentional injury and the status of home environment. The reliability of the scale was tested by using Cronbach's α coefficient and split-half reliability coefficient. The content validity and construct validity were tested by using Pearson correlation analysis and factor analysis. All children were divided into two groups according to the incidence of unintentional injury in the home and the discrimination validity of the scale was tested by using t-test. Results: The scale had 54 items in 6 dimensions. The number of eligible questionnaires was 1 074, including 554 (51.6%) from boys and 519 (48.3%) from children under 3 years old. The incidence rate of unintentional injury and in-home injury was 18.34% (197 children) and 10.71% (115 children). The internal consistency reliability (Cronbach's α) coefficient for the scale was 0.87 and the split-efficacy reliability coefficient was 0.82, both meeting the standard of reliability above 0.70. The Pearson correlation coefficient between each dimension and the whole scale ranged from 0.53 to 0.84 (all P values <0.001). The common factor cumulative variance contribution rate of the scale was 58.34%. There were 54 items with factor loadings greater than 0.30. The root mean square error of approximation, comparative fit index and goodness-of-fit index were 0.07, 0.61 and 0.71, respectively. The score of scale in children with injury was significantly higher than that in children without injury (P=0.022). Conclusion: The validity and reliability of the environment scale for unintentional injury in the home for children aged 0-6 years old in the urban area of China are good.

High Expression of Nuclear Factor of Activated T Cells in Chinese Primary Non-Small Cell Lung Cancer Tissues

Purpose

Nuclear factor of activated T cells (NFAT) has been reported to be involved in the development of various types of cancer including adenocarcinoma of the breast. This research was the first to investigate NFAT protein expression in primary non-small cell lung cancer (NSCLC) tissues from Chinese patients.

Methods

NFAT protein expression was determined in 130 surgically resected primary NSCLC and matched normal tissues by immunohistochemical analysis. The association between NFAT expression and clinical categorical variables was further analyzed with the SPSS software.

Results

We found that NFAT expression was much higher in 85 tumor tissues (65.4%) and lower in 45 tumor tissues (34.6%) compared with the matched normal tissues. Further statistical analysis by the chi-square test showed that high expression of NFAT proteins was significantly associated with tumor differentiation (p=0.045), invasion (p=0.031), histology (p<0.0001), tumor size (p=0.038) and cigarette smoking history (p=0.024). However, there was no correlation between the expression of NFAT proteins and pTNM classification, and no difference in 5-year survival rate between patients with high or low expression of NFAT proteins. Multivariate logistic regression analysis for the correlation between NFAT protein expression levels and various characteristics showed a significant association with histology (p=0.008, OR=0.273).

Conclusion

Our results revealed that high NFAT expression was present in Chinese NSCLCs and that NFAT expression might be involved in the process of human lung cancer development.

Diffusion of tellurium at nickel grain boundaries: a first-principles study

The atomic structures, stabilities, segregation behaviors and diffusion barriers of Te are studied for the bulk, surfaces and four kinds of GBs of nickel. Te behavior is found to be very sensitive to the GB type. The effect of strain on diffusion is strong for different GBs.

Different Effects of Tacrolimus on Innate and Adaptive Immune Cells in the Allograft Transplantation

While tacrolimus (FK506) is currently used as immunosuppression therapy in transplant recipient, the immunological mechanism remains unknown. Herein, the immunoregulatory effects of FK506 were investigated in the physiological status and allogeneic skin transplantation. FK506 cannot significantly alter the functions of innate immune cells (macrophages and neutrophils) and adaptive immune cells (T cells) in the physiological status. However, it can effectively delay allogeneic skin-graft rejection through ameliorating the T cell responses, but not myeloid-derived innate immune cell responses. Importantly, it did not affect the allograft recipient macrophage innate immune defence capacity to bacteria. In clinics, FK506 treatment can significantly control the cytokine production in T cells, but not non-T cells. This study shows targeting calcineurin signalling, FK506, to be essential in inducing allograft tolerance, but not to damage the innate defence capacity, validating the immune cell phenotypes as a potential marker in transplantation following FK506 treatment.

Disseminated Rhizopus microsporus infection following allogeneic hematopoietic stem cell transplantation in a child with severe aplastic anemia

Disseminated Rhizopus microsporus infections are uncommon in children and are resistant to echinocandin and azole antifungal agents. We describe a child with severe aplastic anemia who developed disseminated R. microsporus infection following allogeneic hematopoietic stem cell transplantation. R. microsporus was identified microscopically in the hepatic drain culture and was confirmed on the basis of 18S rRNA and 28S rRNA sequence analyses. The patient was treated successfully with hepatic drainage and amphotericin B deoxycholate.

3D knife-edge characterization of two-photon absorption volume in silicon for integrated circuit testing

We have performed three-dimensional characterization of the TPA effective laser spot size in silicon using an integrated knife-edge sensor. The TPA-induced response of a CMOS integrated circuit is analyzed based on these results and compared to simulation; we have found that the charge injection capacity in IC's active layer could be influenced by irradiance energy and focus depth.

Increased expression of paxillin is found in human oesophageal squamous cell carcinoma: a tissue microarray study

Oesophageal cancer is one of the most common cancers worldwide. Currently, the tumour, node, metastasis (TNM) staging system is the primary method for determining its extent and prognosis, however, data suggest this system does not predict prognosis accurately. Research has, therefore, concentrated on searching for specific biomarkers. Paxillin has been shown to play an important role in controlling cell spread and migration. Its over-expression is considered to correlate with the prognosis of some types of cancers, however, the relationship between paxillin expression and clinical outcome in oesophageal cancer has not been investigated. This study determined the expression of paxillin by immunohistochemistry on the tissue microarray of 100 oesophageal squamous cell cancer patients followed up for a mean of 55 months. Paxillin was over-expressed in tumours in 27/100 cases, compared with 6/100 cases for adjacent non-tumoural cells. No correlation occurred between expression of paxillin and overall patient survival, hence paxillin is not an effective prognostic marker in these patients.

Sulfatide-tenascin interaction mediates binding to the extracellular matrix and endocytic uptake of liposomes in glioma cells

Tenascin-C is an extracellular matrix glycoprotein, whose expression is highly restricted in normal adult tissues, but markedly up-regulated in a range of tumors, and therefore serves as a potential receptor for targeted anticancer drug or gene delivery. We describe here a liposomal carrier system in which the targeting ligand is sulfatide. Experiments with tenascin-C-expressing glioma cells demonstrated that binding of liposomes to the extracellular matrix relied essentially on the sulfatide-tenascin-C interaction. Following binding to the extracellular matrix, the sulfatide-containing liposomes were internalized via both caveolae/lipid raft- and clathrin-dependent pathways, which would ensure direct cytoplasmic release of the cargoes carried in the liposomes. Such natural lipid-guided intracellular delivery targeting at the extracellular matrix glycoproteins of tumor cells thus opens a new direction for development of more effective anticancer chemotherapeutics in future.

Surgical treatment for upper or middle esophageal carcinoma occurring after gastrectomy: a study of 52 cases

Fifty-two patients presenting with upper or middle esophageal carcinoma after gastrectomy between 1980 and 2003 were analyzed retrospectively. Among them, there were five cases of total gastrectomy, six cases of proximal partial gastrectomy and 41 cases of distal subtotal gastrectomy. The interval between gastrectomy and the diagnosis of esophageal carcinoma ranged from 2 to 22 years. Surgical procedures included resection of the esophageal lesion with esophageal replacement using non-reversed or reversed gastric tubes (2 and 3 cases respectively), and short or long segment colon (5 and 40 cases respectively); two cases underwent a palliative procedure (jejunostomy). Complications included cervical anastomotic leaks (3 cases), pulmonary infection (3 cases), atelectasis (2 cases) and cordis arrhythmia (5 cases), all of which responded to treatment. In our group, resection of the esophageal lesions and reconstruction of the esophagus was performed in 45 cases (86.5%), exclusion and bypass procedure of esophageal carcinoma and following radiotherapy and chemotherapy in four (7.7%), eternal jejunostomy for intestinal nutrition in two (3.9%) and death occurred in one case (1.9%) due to multiple organ dysfunction syndrome (MODS). Esophageal resection combined with lymph node dissection is indicated for the treatment of upper or middle esophageal carcinoma following gastrectomy. While esophageal substitutes can include non-reversed or reversed gastric tubes as well as short or long segment colon interpositions, we usually recommend the use of colon interposition. The 1-, 3- and 5-year survival rate of cases with resection of the esophageal lesions and reconstruction of the esophagus was 84.6%, 57.7% and 26.7% respectively.

Investigation on the rheological properties of hepatocellular carcinoma cells and their relevance to cytoskeleton structure

OBJECTIVE

To investigate the relevance of the rheological properties, i.e., viscoelasticities and adhesion to basement membrane components coated surface, of both hepatocytes and hepatocellular carcinoma (HCC) cells to the cytoskeleton structure.

METHODS

Micropipette aspiration technique was adopted to measure viscoelastic coefficients and adhesion forces to 2 microg/ml collagen IV/1.25 microg/ml laminin coated surface of the cells. Two kinds of cytoskeleton perturbing agents, colchicine and cytochalasin D, were used to treat both HCC cells and hepatocytes and the effects of these treatments on cell viscoelastic coefficients and cell adhesion forces were investigated.

RESULTS

Upon treatment of cells with colchicine in a concentration range of 1 to 60 mg/L, the elastic coefficients, especially the first elastic coefficient K1, and adhesion forces of hepatocytes generally tended to increase or increased significantly while, in contrast, viscoelastic coefficients and adhesion forces of HCC cells decreased obviously. Upon treatment of cells with cytochalasin D in a concentration range of 0.25-5.00 mg/L, viscoelastic coefficients of both hepatocytes and HCC cells decreased uniformly, with a larger magnitude for the decrease in elastic coefficients and adhesion forces of HCC cells than for those of hepatocytes. Adhesion forces of hepatocytes and HCC cells onto collagen IV/laminin coated surface varied similarly as viscoelastic coefficients under the action of the cytoskeleton perturbing agents. A significant positive correlation existed between changes of HCC cell adhesion forces on collagen IV/laminin coated surfaces and those of cell elastic coefficients (P<0.01).

CONCLUSIONS

The effects of cochicine and cytochalasin D on rheological properties of HCC cells differed significantly either in ways or extents from those on rheological properties of hepatocytes. These results might reflect the difference in the state of cytoskeleton structure and function among these two kinds of cells.

[Susceptibility to lung cancer in Chinese is associated with genetic polymorphism in cytochrome P4502E1]

OBJECTIVE

To investigate the genetic polymorphism of cytochrome P4502E1 (CYP2E1) as a susceptibility factor for lung cancer in Chinese population.

METHODS

The genotype frequencies of RsaI restriction fragment length polymorphisms were analyzed in 92 lung cancer cases and 137 frequency-matched normal controls.

RESULTS

The CYP2E1 c1/c1 genotype was found in 72.8% of lung cancer cases, which was significantly higher (P < 0.01) than that in controls (54.7%). By multivariate analysis, this genotype was found to be associated with a 2.5-fold increased risk of lung cancer (adjusted OR 2.5, 95% CI 1.8-3.8). Stratified analysis suggested an interaction between CYP2E1 c1/c1 genotype and cigarette smoking. The odds ratio (OR) for the CYP2E1 c1/c1 genotype, cigarette smoking and both factors combined was 3.9 (95% CI 1.1-15.2), 4.1 (95% CI 1.1-15.9) and 7.9 (95% CI 2.4-29.4), respectively. The interaction between CYP2E1 c1/c1 genotype and pack-years of cigarette smoking followed the same pattern, with a markedly increased risk in the heaviest smokers.

CONCLUSION

The CYP2E1 c1/c1 genotype is a susceptibility factor for development of lung cancer in Chinese and there is an apparent gene-environment interaction between the susceptible genotype and cigarette smoking.

[Adhesion of hepatocellular carcinoma cells to collagen IV coated surfaces]

OBJECTIVES

To quantitatively describe the adhesion of hepatocellular carcinoma (HCC) cells and hepatocytes to collagen IV/laminin coated surfaces and to investigate the relevance of cell adhesion forces to the coating concentration of collagen IV and, when laminin was co-coated along with collagen IV, the incorporation concentration of laminin.

METHODS

A stepwise coating protocol was adopted to prepare the collagen IV/laminin coated surfaces, in which poly-D-lysine and collagen IV/laminin were successively coated onto glass surfaces and finally, bovine serum albumin was used to block the non-specific adhesion. Cell adhesion forces were measured by means of micropipette aspiration technique.

RESULTS

Cell adhesion forces showed good dependence on the coating concentration of collagen IV. However, the amplitude for the increase of adhesion forces of HCC cells (202 x 10(-10) N, 26%) was far more less than that for hepatocytes(1,566 x 10(-10) N, 742%) when coating concentration increased from 1 microgram/ml to 5 micrograms/ml. No further increase in the adhesion forces of HCC cells was observed when the coating concentration of collagen IV increased beyond 2 micrograms/ml. The incorporation of laminin along with 2 micrograms/ml collagen IV did not readily result in an increase in the adhesion forces of the two kinds of cells to the surfaces. Among the concentration of laminin tested, only in certain concentration(0.625 microgram/ml or 1.25 micrograms/ml) did the incorporation of laminin along with 2 micrograms/ml collagen IV lead the adhesion forces of hepatocytes and HCC cells to the coated surfaces to reach their corresponding maximum values, otherwise this incorporation led the adhesion forces to decrease.

CONCLUSION

The present method is efficient in investigating cell-matrix adhesion. The cell adhesion behavior to collagen IV for HCC differs obviously from those for normal hepatocytes. Laminin might be an important factor for the regulation of cell adhesion forces to matrix components.

Role of amino acid residues at the interface of alpha52asparginyl-N-glycosyl chain of human choriogonadotropin

Of all the four N-glycosyl chains present in hCG, only one of them at alpha52Asn is located at the alpha/beta subunit interface and is crucial for the biological function of the hormone. The other three are exposed on the surface of the molecule and play only a minor role in the function of the hormone. The alpha52Asn oligosaccharide interacts with five amino acid residues in the beta-subunit, Tyr59, Val62, Phe64, Ala83, and Thr97. The present studies were undertaken to determine the role of the residues at the alpha52Asn-oligosaccharide and the beta-subunit interface in the mechanism of subunit association and downstream signaling events. Ten mutants, two of the alpha-subunit by the replacement of Asn52 and Thr80 with Gln and eight of the beta-subunit by multiple or single amino acid mutations, were prepared. These mutants included, hCGbeta59,62,64,97Ala, hCGbeta59,62,64Ala, hCGbeta62,64Ala, hCGbeta59Phe, hCGbeta62Ala or Thr, hCGbeta83Ile and hCGbeta97Ala. The mutation of the Asn52 to Gln resulted in a drastic change in its conformation and as a consequence in its weak affinity with the wild type beta as compared with that of the wild type hCGalpha and hCGalpha80Gln. The mutants with mutations in the four or three amino acids as well as both mutants of hCGbeta62Val almost failed to combine with hCGalpha again as a result of conformational changes shown by circular dichroism (CD) analysis and not due to their direct involvement in the subunit association. The double mutant combined with hCGalpha and the heterodimer behaved more like the wild type hCG. The mutation of Tyr to Phe resulted in a drop of 20% in the receptor binding and cAMP stimulation although Tyr is considered to be involved directly in subunit association. HCGbeta with mutations in the other amino acids, Phe64, Ala83, and Thr97, combined with the alpha subunit forming heterodimers with biological activity comparable to that of the wild type hCG. Thus, it appears that among the five amino acids in the vicinity of alpha52Asn carbohydrate, only beta59Tyr and beta62Val may be involved directly or indirectly in the alpha/beta beta dimer formation.

Effect of individual N-glycosyl chains in the beta-subunit on the conformation of human choriogonadotropin

Human choriogonadotropin is a heterodimeric glycoprotein hormone comprised of noncovalently associated alpha- and beta-subunits. Each of the subunits has two N-glycosyl chains. In our previous communication, we investigated the role of individual carbohydrate chains in the alpha-subunit on the signal transduction function and conformation of the hormone. This paper deals with the effect of individual or both N-glycosyl chains in the beta-subunit on the function and conformation of the monomer as well as of the heterodimer. Three mutants each of hCGbeta and hCG lacking N-glycosyl chains at beta13Asn, beta30Asn and beta13,30Asn were prepared by site-directed mutagenesis by replacing Thr residues in the recognition triplet sequence at beta15 and beta32 positions with Gln. All mutant heterodimers had receptor binding and cAMP and progesterone stimulating activities comparable to wild type hCG. While the loss of carbohydrate at beta13Asn or beta13,30Asn in the case of hCGbeta monomer resulted in a 4-6%, decrease in the ordered structure, the loss of the glycosyl chain at beta 30Asn did not alter the conformation as compared with the wild type hCGbeta. Similarly, all carbohydrate deficient hCG heterodimers had a decrease of 6-8%) in the ordered structure as compared with hCG. Thus, while the individual N-glycosyl chains did not affect the function of the hormone, they did have marked effect on its conformation but the conformational changes were localized and did not perturb the receptor binding and signal transduction sites.

Mutants of human choriogonadotropin lacking N-glycosyl chains in the alpha-subunit. 1. Mechanism for the differential action of the N-linked carbohydrates

Analogs of human choriogonadotropin (hCG) lacking N-glycosyl chains at alpha52Asn and alpha78Asn were purified from the culture media of insect cells by immunoaffinity chromatography using a monoclonal antibody column. As previously reported, while analogs lacking carbohydrate at alpha52Asn and alpha78Asn had similar receptor binding activities compared with the wild type recombinant hCG (hCGwt), they differed in their signal transduction properties. The mutant lacking carbohydrate at alpha78Asn had 20% less cAMP-stimulating activity than hCGwt, but the absence of glycosylation at alpha52Asn resulted in the reduction of cAMP accumulation by 90-95%. A similar effect of the mutations was observed on the stimulation of steroidogenesis. Circular dichroism spectra of the two mutants showed significant differences. The mutant lacking carbohydrate at alpha52Asn had a much higher negative mean residue ellipticity (MRE) at 200 nm and a lower negative MRE at 220 nm than that lacking carbohydrate at alpha78Asn and hCGwt. The dissociation rates of the alpha52Asn and alpha78Asn carbohydrate deficient mutants at pH 3 and room temperature, measured by using 1-anilino-8-naphthalenesulfonate, were 9.4 x 10(-5) and 3.8 x 10(-5) s-1, respectively, as compared with 1.5 x 10(-5) s-1 for hCGwt. The results of both CD measurements and dissociation studies strongly suggest that the absence of carbohydrate at alpha52Asn results in conformational changes in the mutant which might explain the loss in its signal transduction function. This is further supported by indirect evidence from two other lines of experimentation. Unlike the mutant lacking carbohydrate at alpha78Asn, the one lacking carbohydrate at alpha52Asn cross-reacted with the two subunit specific monoclonal antibodies, anti-hCGalpha and anti-hCGbeta, which normally did not cross-react with the native or the hCGwt. Also, polyclonal anti-hCGbeta but not anti-hCGalpha was able to restore the cAMP-producing activity of the alpha52Asn carbohydrate deficient mutant. From all the data taken together, it appears that the loss of second messenger-producing activity of hCG with the absence of the glycosyl chain at alpha52Asn was probably due to a conformational change in the heterodimer rather than due to the loss of the alpha52Asn-carbohydrate-receptor interaction.

Effect of modification of the beta-hairpin and long loops simultaneously in both alpha- and beta-subunits on the function of human choriogonadotropin: part II

According to the X-ray diffraction, human choriogonadotropin has four beta-hairpin and two long loops, equally distributed in each of the alpha and beta subunits. Radical mutations such as the replacement of alpha 18Phe and alpha 74Phe with Thr in the alpha1 and alpha3 loops respectively and the replacement of alpha 45Lys with Asp in the alpha2 loop in the alpha-subunit were introduced while the loop sequences in the beta-subunit were replaced with the corresponding sequences in hFSH beta. Nine different double mutants with simultaneous mutations in both the alpha and beta loops including hCG alpha1 beta1, hCG alpha1 beta2, hCG alpha1 beta3, hCG alpha2 beta1, hCG alpha2 beta2, hCG alpha2 beta3, hCG alpha3 beta1, hCG alpha3 beta2 and hCG alpha3 beta3 were partially purified from insect High-Five cells. As previously reported (Shao et al., 1996, Mol. Cell. Endocrinol. 122, 173-182), the mutation in the alpha1 loop in the mutant, hCG alpha1 beta, the mutants hCG alpha1 beta1 and hCG alpha1 beta3 caused 200%, increase in the receptor binding, cAMP and progesterone stimulation. The mutant, hCG alpha1 beta2 and all other mutants behaved like the recombinant hCG (rehCG) in the receptor binding and post-receptor signaling activities. The molecular cause for this increase is probably due to a conformational change in the heterodimers caused by the mutation in the alpha1 loop. This conclusion is based on the results of the dissociation studies of the mutants heterodimers which indicated a decreased affinity between the subunits. The first order rate constants for the dissociation of the mutants hCG alpha1 beta1, hCG alpha1 beta2 and hCG alpha beta3 were 3.7 x 10(-2) min(-1), 1.4 x 10(-2) min(-1) and 4.6 x 10(-2) min(-1) respectively, as compared with 4.6 x 10(-3) min(-1) for the rehCG. It seems from the data that alpha 18Phe is located in, or in proximity to the receptor binding site and probably plays a critical role in maintaining either directly or indirectly its conformational integrity.

Effect of modification of all loop regions in the alpha- and beta-subunits of human choriogonadotropin on its signal transduction activity

Human choriogonadotropin (hCG), according to its three dimensional structure as determined by X-ray diffraction, has three beta-hairpin loops each in the alpha and beta subunit designated as alpha 1, alpha 2 alpha 3 and beta 1 beta 2 and beta 3, respectively. Since similar beta-hairpin loops in NGF and TNF beta have been implicated in their direct interaction with the receptor, it prompted the present investigation to determine the role of such loops in receptor binding and post-receptor signaling events in hCG. Based on the three dimensional structure of hCG, radical mutations were introduced in the alpha loops by replacing hydrophobic alpha 18Phe and alpha 74Phe by hydrophilic Thr residues in the alpha 1 and alpha 3 loops, respectively, and positively charged alpha 45Lys by negatively charged Asp in the helical segment in the alpha 2 loop. The beta loops were mutated by replacement of the beta 1, beta 2 and beta 3 sequences with the corresponding hFSH sequences. These replacements included beta 22Gly, beta 24Pro and beta 25Val with Glu, Arg and Phe in beta 1, 45Leu Gln Gly Val Leu Pro Ala Leu Pro53 with Tyr Lys Asn Pro Ala Arg Pro Leu Ile in beta 2 and 73Pro Arg Gly with Ala His His in the beta 3 loop. Six mutants, hCG alpha 1 beta, hCG alpha 2 beta and hCG alpha 3 beta and hCG alpha beta 1, hCG alpha beta 2 and h CG alpha beta 3, were obtained by co-infection of the insect High-Five cells with baculovirus containing mutant alpha or beta cDNAs and that containing complimentary wild type beta or alpha cDNAs. The mutants were almost completely secreted in the culture medium and were over expressed at levels ranging between 4.5 to 29 micrograms/ml indicating that mutations had no effect on the secretion or subunit assembly of hCG. In order to remove any contaminating beta-subunit, the culture medium was passed through a column of an hCG beta-specific monoclonal antibody, B158. The receptor binding activity of the mutant hCG alpha 1 beta, in which alpha 18Phe was replaced with Thr, increased almost 200% relative to rehCG. Similarly, increase in the cAMP and progesterone stimulation by the mutant ranged between 150 to 200%. This increase is believed to be due to a short range conformational change in the mutant as a result of the mutation rather than direct involvement of alpha 18Phe in the receptor binding. The evidence in support of this was derived from the fact that the affinity or interaction between the two subunits was impaired as indicated by the first order rate constant of hCG alpha 1 beta (km = 4.1 x 10(-2) min-1) at pH 3.0 at 23 degrees C which is one order of magnitude greater relative to rehCG (kw = 4.6 x 10(-3) min-1). All other mutations had no effect on the receptor binding or signal transduction of hCG indicating that, unlike NGF or TNF beta, beta-hairpin loops in hCG were not directly involved in receptor binding or post-receptor signaling events. However, since the mutation in the alpha 1 loop affects the receptor binding site, its presence in the vicinity of the alpha 1 loop is highly likely.

Preparation of recombinant carbohydrate deficient active analogs of human chorionic gonadotropin from insect cells

Human chorionic gonadotropin (hCG) has four N-glycosyl chains, two in each subunit. Several analogs lacking one or more specific N-linked carbohydrate chains have been purified from insect cells by immunoaffinity chromatography on a monoclonal antibody, B17, column Traces of the hCG beta mutant present, if any, were removed by a second immunoaffinity chromatography on a column of hCG beta specific monoclonal antibody, B158. N-glycosylation was inhibited by the replacement of either Asn or Thr to Gln in the consensus sequence. -Asn x Ser/Thr-, for N-glycosylation. All analogs were overexpressed in High-Five insect cells with the expression levels ranging between 1.5 to 15 micrograms/ml and were found homogeneous by SDS-PAGE under nonreducing and reducing conditions. Their molecular sizes ranged between 34k to 44k. The receptor binding affinity of all the analogs was unaltered as determined by radio receptor assay using rat ovarian membranes. The availability of these analogs should facilitate studies on the effect of a specific carbohydrate chain on the conformation and in vivo properties of hCG.