Factors influencing different types of malocclusion and arch form-A review.

AIM: This review intends to highlight malocclusion as a multifactorial issue and review the different factors that influence different types of malocclusion and arch form. METHODS: An online article search was performed on the factors influencing malocclusion and arch form from January 1990 through April 2020. The search was performed within the Google, Rutgers library, PubMed, MEDLINE databases via OVID using the keywords mentioned in the PubMed and MeSH headings for the English language published articles January 1990 through April 2020, which evaluated different factors that influence malocclusion and arch form. RESULTS: Of the 300 articles found in initial search results, 31 articles met the inclusion criteria set for this review. These 31 studies were directly related to the factors that impact malocclusion and different arch forms. CONCLUSION: Genetic inheritance, genetic mutations, age, gender, ethnicity, dental anomalies like macrodontia, congenital diseases, muscular diseases, hormone imbalance, and human behaviour are all factors that influence malocclusion and arch forms. The elements within the individual's control like behaviours can aid in preventing malocclusion. However, it seems as if the underlying reason for most of these factors indicates that malocclusion is a by-product of genetics and pathology.

Histone deacetylase inhibitor treatment restores memory-related gene expression and learning ability in neonicotinoid-treated Apis mellifera.

Apis mellifera plays crucial roles in maintaining the balance of global ecosystems and stability of agricultural systems by helping pollination of flowering plants, including many crops. In recent years, this balance has been disrupted greatly by some pesticides, which results in great losses of honeybees worldwide. Previous studies have found that pesticide-caused memory loss might be one of the major reasons for colony loss. Histone deacetylase inhibitors (HDACis) are chemical compounds that inhibit the activity of histone deacetylases and are known to cause hyperacetylation of histone cores and influence gene expression. In our study, the HDACi sodium butyrate was applied to honeybees as a dietary supplement. The effect of sodium butyrate on the expression profiles of memory-related genes was analysed by quantitative reverse transcription PCR. The results revealed that this HDACi had up-regulation effects on most of the memory-related genes in bees, even in bees treated with imidacloprid. In addition, using the proboscis extension reflex to evaluate olfactory learning in bees, we found that this HDACi boosted the memory formation of bees after impairment owing to imidacloprid exposure. This study investigated the association between gene expression and memory formation from an epigenetic perspective. Additionally, we further demonstrate the possibility of enhancing bee learning using HDACis and provide initial data for future research.

Automated 3D-printed unibody immunoarray for chemiluminescence detection of cancer biomarker proteins.

A low cost three-dimensional (3D) printed clear plastic microfluidic device was fabricated for fast, low cost automated protein detection. The unibody device features three reagent reservoirs, an efficient 3D network for passive mixing, and an optically transparent detection chamber housing a glass capture antibody array for measuring chemiluminescence output with a CCD camera. Sandwich type assays were built onto the glass arrays using a multi-labeled detection antibody-polyHRP (HRP = horseradish peroxidase). Total assay time was ∼30 min in a complete automated assay employing a programmable syringe pump so that the protocol required minimal operator intervention. The device was used for multiplexed detection of prostate cancer biomarker proteins prostate specific antigen (PSA) and platelet factor 4 (PF-4). Detection limits of 0.5 pg mL-1 were achieved for these proteins in diluted serum with log dynamic ranges of four orders of magnitude. Good accuracy vs. ELISA was validated by analyzing human serum samples. This prototype device holds good promise for further development as a point-of-care cancer diagnostics tool.

Chaperones and intimate physical examinations: what do male and female patients want?

INTRODUCTION: Many studies of patients' perception of a medical chaperone have focused on female patients; that of male patients are less well studied. Moreover, previous studies were largely based on patient populations in English-speaking countries. Therefore, this study was conducted to investigate the perception and attitude of male and female Chinese patients to the presence of a chaperone during an intimate physical examination. METHODS: A cross-sectional guided questionnaire survey was conducted on a convenient sample of 150 patients at a public teaching hospital in Hong Kong. RESULTS: Over 90% of the participants considered the presence of a chaperone appropriate during intimate physical examination, and 84% felt that doctors, irrespective of gender, should always request the presence of a chaperone. The most commonly cited reasons included the availability of an objective account should any legal issue arise, protection against sexual harassment, and to provide psychological support. This contrasted with the experience of those who had previously undergone an intimate physical examination of whom only 72.6% of women and 35.7% of men had reportedly been chaperoned. Among female participants, 75.0% preferred to be chaperoned during an intimate physical examination by a male doctor, and 28.6% would still prefer to be chaperoned when being examined by a female doctor. Among male participants, over 50% indicated no specific preference but a substantial minority reported a preference for chaperoned examination (21.2% for male doctor and 25.8% for female doctor). CONCLUSIONS: Patients in Hong Kong have a high degree of acceptance and expectations about the role of a medical chaperone. Both female and male patients prefer such practice regardless of physician gender. Doctors are strongly encouraged to discuss the issue openly with their patients before they conduct any intimate physical examination.

Paper-based electrochemical immunoassay for rapid, inexpensive cancer biomarker protein detection.

Inexpensive, reusable electrochemical sensor chips were fabricated from gold CDs. All reagents were loaded onto a paper disk sequentially, then placed on the chip to detect cancer biomarker prostate specific antigen (PSA) in serum at pg mL-1 levels in ∼15 mins.

A HUVEC line with a stable expression of the VEGF121 gene to achieve complete endothelialization of blood conduits.

The purpose of this investigation was to establish monoclonal cell lines of HUVEC with the stable expression of the VEGF(121) gene. Such cells are likely to better adhere to the luminal surface of stents or grafts and to promote a complete endothelialization. The eukaryotic expression vector PCD(2)-VEGF(121) was transfected into cell lines of HUVEC mediated by lipofect AMINE. The positive clones were obtained by the screening of G(418). The transcription and expression of the VEGF gene were investigated by RT-PCR and immunocytochemistry, respectively. The experiment of Miles was applied for the assay of the biological activity of the protein of the VEGF produced by the HUVEC lines with transfected PCD(2)-VEGF(121). The growth curve was made for comparison with that of non-transfected HUVEC line cells. The positive clone cells from which transcripted the mRNA of VEGF(121) gene were obtained by RT-PCR. The positive results of the immunocytochemistry were found and the high biological activity of VEGF in the media was detected in the positive clone cells only. The time to achieve the multiplication of the positive clone cells by a factor of 2 was shorter than that of the non-transfected HUVEC line calculated from the growth curve. The HUVEC line of monoclonal cells with the stable expression of VEGF(121) gene has been established successfully and can be employed on the luminal surfaces of foreign blood conduits.

Attitudes of Hong Kong Chinese to traditional Chinese medicine and Western medicine: survey and cluster analysis.

OBJECTIVES: To determine whether within a cohort of Hong Kong out-patients definable subtypes exist based on their attitudes to traditional Chinese medicine and Western medicine. DESIGN: Data were collected using a structured questionnaire. SETTING: The sample of 503 subjects was recruited at two local outpatient clinics in Hong Kong. MAIN OUTCOME MEASURES: The study employs demographic variables, illness status, the Chinese-Western Medical Belief Scale, trust of physicians and subjects' preferences on consultation fees, attitude of health care professional, efficacy of service and waiting time during consultation. RESULTS: A cluster analysis yielded three clusters based on their attitudes towards traditional Chinese and Western medicine. One cluster, 24% of the sample, is noted for being older, poorer, more likely to be female and to have chronic conditions; they are sceptical of western physicians. The second cluster (63% of the sample) is younger and have considerably more belief in Western than traditional Chinese medicine. The third group (14%) is intermediate in age and is noted for a marked faith in both forms of medicine. CONCLUSIONS: A clear profile of these attitudes of Hong Kong Chinese may benefit health care professionals in making appropriate patient-doctor relationships and planning patient care.

Flavin specificity and subunit interaction of Vibrio fischeri general NAD(P)H-flavin oxidoreductase FRG/FRase I.

Apoenzyme of the major NAD(P)H-utilizing flavin reductase FRG/FRase I from Vibrio fischeri was prepared. The apoenzyme bound one FMN cofactor per enzyme monomer to yield fully active holoenzyme. The FMN cofactor binding resulted in substantial quenching of both the flavin and the protein fluorescence intensities without any significant shifts in the emission peaks. In addition to FMN binding (K(d) 0.5 microM at 23 degrees C), the apoenzyme also bound 2-thioFMN, FAD and riboflavin as a cofactor with K(d) values of 1, 12, and 37 microM, respectively, at 23 degrees C. The 2-thioFMN containing holoenzyme was about 40% active in specific activity as compared to the FMN-containing holoenzyme. The FAD- and riboflavin-reconstituted holoenzymes were also catalytically active but their specific activities were not determined. FRG/FRase I followed a ping-pong kinetic mechanism. It is proposed that the enzyme-bound FMN cofactor shuttles between the oxidized and the reduced form during catalysis. For both the FMN- and 2-thioFMN-containing holoenzymes, 2-thioFMN was about 30% active as compared to FMN as a substrate. FAD and riboflavin were also active substrates. FRG/FRase I was shown by ultracentrifugation at 4 degrees C to undergo a monomer-dimer equilibrium, with K(d) values of 18.0 and 13.4 microM for the apo- and holoenzymes, respectively. All the spectral, ligand equilibrium binding, and kinetic properties described above are most likely associated with the monomeric species of FRG/FRase I. Many aspects of these properties are compared with a structurally and functionally related Vibrio harveyi NADPH-specific flavin reductase FRP.

Nuclear localization of E-cadherin expression in Merkel cell carcinoma.

CONTEXT: Cadherins are cell-cell adhesion proteins that act as tumor suppressor genes and have a critical role in cell sorting and tissue formation during organogenesis. The pattern of cadherin expression constitutes a useful diagnostic and prognostic tool in the evaluation of tumors and for determining the histogenesis of tumor cells. We have previously characterized the cell types of several tumors based on the expression of individual cadherins. OBJECTIVE: To investigate the expression of cadherins in Merkel cell carcinomas. DESIGN: Paraffin immunohistochemical analysis of the 3 best-studied cadherins was performed on 35 cases of Merkel cell carcinoma. RESULTS: E-cadherin was expressed in 34 (97%) of 35 Merkel cell carcinomas examined, N-cadherin was expressed in 22 (63%) of 35 cases, and P-cadherin was expressed in 15 (43%) of 35 cases. This frequency of cadherin expression was similar to a group of small cell and neuroendocrine tumors from other primary sites. Interestingly, the localization of E-cadherin expression was unique in Merkel cell carcinomas compared with other primary neuroendocrine tumors. Merkel cell carcinomas showed marked preference for nuclear versus membrane localization, whereas small cell tumors from other sites showed fewer cases of nuclear E-cadherin expression. The nuclear localization of E-cadherin did not correlate with cadherin-associated protein beta-catenin nuclear expression. CONCLUSIONS: Our findings show that E-cadherin is the most frequently expressed cadherin in Merkel cell carcinoma, followed in frequency by N-cadherin then P-cadherin. The pattern of nuclear E-cadherin expression is more frequent for Merkel cell carcinoma than small cell tumors of other primary sites. These observations suggest that E-cadherin expression and function are altered in Merkel cell carcinoma, and this finding has potential use in the differential diagnosis of these tumors.

Epidermal growth factor receptor vIII enhances tumorigenicity in human breast cancer.

Epidermal growth factor receptor vIII (EGFRvIII) is a tumor-specific, ligand-independent, constitutively active variant of the EGFR. Its expression has been detected in gliomas and various other human malignancies. To more fully characterize the function and potential biological role of EGFRvIII in regulating cell proliferation and in tumorigenesis, we transfected EGFRvIII cDNA into a nontumorigenic, interleukin 3 (IL-3)-dependent murine hematopoietic cell line (32D cells). We observed 32D cells expressing high levels of EGFRvIII (32D/EGFRvIII P5) to be capable of abrogating the IL-3-dependent pathway in the absence of ligands. In contrast, the parental cells, 32D/EGFR, 32D/ErbB-4, and 32D/ErbB-2+ErbB-3 cells, all depended on IL-3 or EGF-like ligands for growth. 32D/EGFRvIII P5 cells subjected to long-term culture conditions in the absence of IL-3 revealed further elevation of EGFRvIII expression levels. These results suggested that the IL-3-independent phenotype is mediated by EGFRvIII. The level of expression is a critical driving force for the IL-3-independent phenotype. Dose-response analysis revealed 32D/EGFRvIII cells to require 500-fold higher concentrations (50 ng/ml) of EGF to further stimulate the EGF-mediated proliferation than in the 32D/EGFR cells (100 pg/ml). Similar effects were also observed in beta-cellulin-mediated proliferation. Moreover, 32D cells expressing high levels of EGFRvIII formed large tumors in nude mice, even when no exogenous EGF ligand was administered. In contrast, no tumors grew in mice injected with 32D/EGFR, 32D/ErbB-4, and 32D/ErbB-2+ErbB-3 cells or low-expressing clone 32D/EGFRvIII C2 cells or the parental 32D cells. The changes of the ligand specificity support the notion for an altered conformation of EGFRvIII to reveal an activated ligand-independent oncoprotein with tumorigenic activity analogous to v-erbB. These studies clearly demonstrate that EGFRvIII is capable of transforming a nontumorigenic, IL-3-dependent murine hematopoietic cell line (32D cells) into an IL-3-independent and ligand-independent malignant phenotype in vitro and in vivo. To delineate the biological significance of EGFRvIII in human breast cancer, we expressed EGFRvIII in the MCF-7 human breast cancer cell line. Expression of EGFRvIII in MCF-7 cells produced a constitutively activated EGFRvIII receptor. Expression of EGFRvIII in MCF-7 cells also elevated ErbB-2 phosphorylation, presumably through heterodimerization and cross-talk. These MCF-7/EGFRvIII transfectants exhibited an approximately 3-fold increase in colony formation in 1% serum with no significant effect observed at higher percentages of serum. A similar result was also seen in anchorage-dependent assays. Furthermore, EGFRvIII expression significantly enhanced tumorigenicity of MCF-7 cells in athymic nude mice with P < 0.001. Collectively, these results provide the first evidence that EGFRvIII could play a pivotal role in human breast cancer progression.

Probing the mechanisms of the biological intermolecular transfer of reduced flavin.

NAD(P)H-flavin oxidoreductases [flavin reductases (FR)] are a class of enzymes capable of producing reduced flavin for bacterial bioluminescence and other biological processes. Bacterial luciferase utilizes oxygen, reduced FMN (FMNH2) and a long-chain aliphatic aldehyde as substrates for light emission. The Vibrio harveyi luciferase and FRP (for which we have cloned the gene and determined the crystal structure) is a model for the elucidation of the reduced flavin transfer mechanism using both a flavin reductase single-enzyme assay monitoring the NADPH oxidation and a flavin reductase-luciferase coupled assay measuring bioluminescence intensity or quantum output. The FRP exhibits a ping-pong kinetic pattern in the single-enzyme assay but changes to a sequential pattern in the coupled assay. Furthermore, FMN at >2x10(-6) mol/L reduced both the light intensity and quantum yield of the coupled reaction by noncompetitively inhibiting NADPH and competitively inhibiting luciferase. These results support a scheme in which the luciferase forms specific complex(es) with FRP. Indeed, such complexes were shown by fluorescence anisotropy to exist between luciferase and monomeric FRP either in the holo- or apoenzyme form. Furthermore, the reduced flavin cofactor of FRP is transferred directly to luciferase for bioluminescence, whereas the reduced flavin product of FRP is inefficient in supporting the luminescence reaction. The mechanism of reduced flavin transfer is apparently flavin and flavin reductase specific.

Anti-HER2 antibody enhances the growth inhibitory effect of anti-oestrogen on breast cancer cells expressing both oestrogen receptors and HER2.

Anti-oestrogen is effective for the treatment of oestrogen receptor (ER)-positive breast carcinomas, but most of these tumours become resistant to anti-oestrogen. It has been suggested that anti-oestrogen therapy may induce a HER2 signalling pathway in breast cancer cells and this may cause resistance to anti-oestrogen. Thus, it is conceivable that combined therapy with anti-oestrogen and anti-HER2 antibody might be more effective. In the present study, we investigated the effect of combined treatment with a humanized anti-HER2 monoclonal antibody, rhumAbHER2 (trastuzumab), and an anti-oestrogen, ICI 182,780, on the cell growth of three human breast cancer cell lines which respectively express different levels of ER and HER2. The combined treatment enhanced the growth inhibitory effect on ML-20 cells, which express a high level of ER and a moderate level of HER2, but showed no additive effect on either KPL-4 cells, which express no ER and a moderate level of HER2, or MDA-MB-231 cells, which express no ER and a low level of HER2. It is also suggested that both the antibody and anti-oestrogen induce a G1-S blockade and apoptosis. These findings indicate that combined treatment with anti-HER2 antibody and anti-oestrogen may be useful for the treatment of patients with breast cancer expressing both ER and HER2.

Ribozyme-mediated down-regulation of ErbB-4 in estrogen receptor-positive breast cancer cells inhibits proliferation both in vitro and in vivo.

ErbB-4 is a recently discovered member of the class I receptor tyrosine kinase family (ErbB). Little is known about its expression and its importance in human malignancy. To delineate the biological function of ErbB-4 receptors in breast cancer, we used a hammerhead ribozyme strategy to achieve down-regulation of ErbB-4 receptors in various breast cancer cell lines. We observed that down-regulation of ErbB-4 in estrogen receptor-positive (ER+) human breast cancer cell lines (MCF-7 and T47D), which express relatively high levels of ErbB-4, significantly inhibited colony formation. No effects were observed in estrogen receptor-negative (ER-) MDA-MB-453 cells, which express low levels of endogenous ErbB4 and high levels of ErbB-2 and ErbB-3. This occurred despite the fact that fluorescence-activated cell sorter analysis of these latter cells revealed that the expression of the ErbB-4 receptor was completely abrogated by ribozyme treatment. Furthermore, down-regulation of ErbB-4 in T47D and MCF-7 cells significantly inhibited tumor formation in athymic nude mice (P < 0.03 and P < 0.001, respectively). In addition, NRG-stimulated phosphorylation of ErbB-4- and NRG-induced colony formation was significantly reduced in ribozyme-transfected T47D cells. These data provide the first evidence that elevation of ErbB-4 expression plays a role in the proliferation of some ER+ human breast cancer cell lines (T47D and MCF-7) that express high levels of ErbB-4. We have also investigated the expression of ErbB-4 in human primary breast carcinoma specimens, using immunohistochemical staining with an anti-ErbB-4 monoclonal antibody. ErbB-4 expression was found in 60% of the 50 primary breast tumors examined, and high intense immunoreactivity of ErbB-4 was detected in 18% of these primary breast tumors. ErbB-4 receptor expression appeared to correlate with ER+ primary breast tumors. A similar correlation was also observed in the human breast cancer cell lines. These results provide a better understanding of the biological significance of ErbB-4 receptor in breast cancer. Our data suggest that elevation of the ErbB-4 receptor plays a role in ER+ breast cancer cell proliferation. Moreover, ribozyme technology provides a useful tool to delineate the role of a particular gene product.

P+HA- charge recombination reaction rate constant in Rhodobacter sphaeroides reaction centers is independent of the P/P+ midpoint potential.

The kinetics of the P+HA- (oxidized donor, reduced bacteriopheophytin acceptor) recombination reaction was measured in a series of reaction center mutants of Rhodobacter sphaeroides with altered P/P+ midpoint potentials between 410 and 765 mV. The time constant for P+HA- recombination was found to range between 14 and 26 ns and was essentially independent of P/P+ midpoint potential. Previous work has shown that the time constant for initial electron transfer in these mutants at room temperature is also only weakly dependent on the P/P+ midpoint potential, ranging from about 2.5 ps to about 50 ps. These results, taken together, imply that heterogeneity in the P/P+ midpoint potential within the reaction center population is not likely the dominant cause of the substantial kinetic complexity observed in the decay of the excited singlet state of P on the picosecond to nanosecond time scale. In addition, the pathway of P+HA- decay appears to be direct or via P+BA- rather than proceeding back through P, even in the highest-potential mutant, as is evident from the fact that the rate of P+HA- recombination is unaltered by pushing P+HA- much closer to P in energy. Finally, the midpoint potential independence of the P+HA- recombination rate constant suggests that the slow rate of P+HA- recombination arises from an inherent limitation in the maximum rate of this process rather than because it occurs in the inverted region of a classical Marcus rate vs free energy curve.

Cripto-1 indirectly stimulates the tyrosine phosphorylation of erb B-4 through a novel receptor.

Cripto-1 (CR-1) is a recently discovered protein of the epidermal growth factor family that fails to directly bind to any of the four known erb B type 1 receptor tyrosine kinases. The present study demonstrates that CR-1 indirectly induces tyrosine phosphorylation of erb B-4 but not of the epidermal growth factor-related receptors erb B-2 and erb B-3 in different mouse and human mammary epithelial cell lines. In addition, down-regulation of erb B-4 in NMuMG mouse mammary epithelial cells and in T47D human breast cancer cells, using an anti-erb B-4 blocking antibody or a hammerhead ribozyme vector targeted to erb B-4 mRNA, impairs the ability of CR-1 to fully activate mitogen-activated protein kinase. Finally, chemical cross-linking of 125I-CR-1 to mouse and human mammary epithelial cell membranes results in the labeling of two specific bands with a molecular weight of 130 and 60 kDa, suggesting that the CR-1 receptor represents a novel receptor structurally unrelated to any of the known type I receptor tyrosine kinases. In conclusion, these data demonstrate that CR-1, upon binding to an unknown receptor, can enhance the tyrosine kinase activity of erb B-4 and that a functional erb B-4 receptor is required for CR-1-induced MAPK activation.

Isolation and characterization of a new human breast cancer cell line, KPL-4, expressing the Erb B family receptors and interleukin-6.

A new human breast cancer cell line, KPL-4, was recently isolated from the malignant pleural effusion of a breast cancer patient with an inflammatory skin metastasis. This cell line can be cultured under serum-free conditions and is tumorigenic in female athymic nude mice. Flow cytometric analysis revealed the expression of Erb B-1, -2 and -3. Dot blot hybridization showed a 15-fold amplification of the erb B-2. Reverse transcription-polymerase chain reaction analysis showed a detectable level of mRNA expression of all the Erb B family receptors. In addition, all the receptors were autophosphorylated under a serum-supplemented condition. Unexpectedly, transplanted KPL-4 tumours induced cachexia of recipient mice. A high concentration of interleukin-6 (IL-6) was detected in both the culture medium and the serum of mice. The weight of tumours significantly correlated with the serum IL-6 level. The antiproliferative effect of a humanized anti-Erb B-2 monoclonal antibody, rhuMAbHER2, was investigated. This antibody significantly inhibited the growth of KPL-4 cells in vitro but modestly in vivo. Loss of mouse body weight was partly reversed by rhuMAbHER2. These findings suggest that KPL-4 cells may be useful in the development of new strategies against breast cancer overexpressing the Erb B family receptors and against IL-6-induced cachexia.

Dysregulated synthesis of intracellular type 1 and type 2 cytokines by T cells of patients with cutaneous T-cell lymphoma.

Mycosis fungoides (MF) and Sezary syndrome (SS) are the two main clinical entities of cutaneous T-cell lymphoma (CTCL). As the disease progresses from MF to SS, a switch from a type 1 (interleukin [IL]-2 and gamma interferon [IFN-gamma]) to a type 2 (IL-4) cytokine production profile occurs. Although roles for type 1 and type 2 cytokines in the pathogenesis of CTCL have been proposed, the cellular origins of these cytokines are unclear. Using flow cytometry to identify individual T-cell subsets, we studied cytokine synthesis by the T cells of 13 patients with SS and 12 with MF and 9 hematologically healthy donors. Upon activation with phorbol 12-myristate 13-acetate (PMA), the numbers of T cells synthesizing IL-2 were similar for all study groups. Whereas the predominant T-cell producing IL-2 in healthy donors and in those with MF was CD7(+), in patients with SS, it was CD7(-). Although the number of IL-4(+) CD4(+) T cells was low for all study groups, there was a significantly higher number of IL-4(+) CD8(+) T cells in patients with MF than in those with SS or healthy donors. There was a decline in the number of IFN-gamma-producing T cells in CTCL donors compared to that in healthy donors. More importantly, there was a significant decrease in the number of IFN-gamma-producing T cells with disease progression from MF to SS. The inability of these T cells to synthesize IFN-gamma may have prognostic value in CTCL, since it may be responsible for the progression of the disease from MF to SS.

ErbB-4 ribozymes abolish neuregulin-induced mitogenesis.

The epidermal growth factor-like receptor tyrosine kinase (ErbB) family is frequently overexpressed in a variety of human carcinomas, including breast cancer. To assist in characterizing the role of ErbB-4 in breast cancer, we generated three specific hammerhead ribozymes targeted to the ErbB-4 mRNA. These ribozymes, Rz6, Rz21, and Rz29, efficiently catalyzed the specific cleavage of ErbB-4 message in a cell-free system. We demonstrated that the neuregulin-induced mitogenic effect was abolished in ribozyme Rz29- and Rz6-transfected 32D/ErbB-4 cells. Inhibition of mitogenesis was characterized by ribozyme-mediated down-regulation of ErbB-4 expression. In addition, we provide the first evidence that different threshold levels of ErbB-4 expression and activation correlate with different responses to neuregulin stimulation. High levels of ErbB-4 expression, phosphorylation, and homodimerization are necessary for neuregulin-stimulated, interleukin 3-independent cell proliferation in the 32D/E4 cells. In the case of Rz29-transfected 32D/E4 cells, low levels of ErbB-4 expression allowed neuregulin-induced phosphorylation but were insufficient to couple the activated receptor to cellular signaling. Furthermore, expression of the functional ErbB-4 ribozyme in T47D human breast carcinoma cells led to a down-regulation of endogenous ErbB-4 expression and a reduction of anchorage-independent colony formation. These studies support the use of ErbB-4 ribozymes to define the role of ErbB-4 receptors in human cancers.

Involvement of heregulin-beta2 in the acquisition of the hormone-independent phenotype of breast cancer cells.

The erbB-2 receptor plays an important role in the prognosis of breast cancer. Amplification or overexpression of the erbB-2 proto-oncogene has been detected in 30% of breast cancers and is associated with poor patient prognosis. The significance of erbB-3 and erbB-4 in breast cancer is not yet known. The discovery of the growth factor heregulin (HRG) has allowed us to investigate a number of biological events that are regulated by erbB-2, -3, and -4 signal transduction. To determine the role of HRG in breast cancer tumor progression, we have developed an in vitro/in vivo model. We transfected HRG cDNA into the estrogen receptor (ER)-positive breast cancer cell line, MCF-7, and studied these cells as they progressed from a hormone-dependent to -independent phenotype. The biochemical and biological characteristics presented here demonstrate that overexpression of HRG induces morphological changes in MCF-7 cells as well as erbB-2, erbB-3, and erbB-4 autophosphorylation. MCF-7/ heregulin-transfected cells, which express relatively high levels of HRG, developed estrogen independence and resistance to antiestrogens in vitro and in vivo. This is consistent with a more aggressive hormone-independent phenotype. In contrast with control parental/wild-type cells, estradiol-mediated down-regulation of erbB-2 expression is blocked completely in this particular model system. These results indicate that HRG plays a role in the disruption of ER function. When a transient transfection with an ERE-CAT construct was introduced into these HRG-transfected MCF-7 cells, we observed that the ER was transcriptionally inactive. This suggests that ER signaling is altered in HRG-transfected cells. We observed that overexpression of HRG induces a more aggressive, hormone-independent phenotype that is most likely directly related to the constitutive activation of the erbB-2, erbB-3, and erbB-4 receptor signaling cascade. The data presented here suggest a close cross-regulation between the erbB-2/4 receptors and ER and provide new insights into the mechanism by which breast cancer cells acquire a hormone-independent phenotype.

Malignant myoepithelioma of the parotid gland: case report and review of the literature.

A 62-year-old male with a myoepithelioma of the right parotid gland was treated with surgical excision followed by adjuvant radiation therapy. Prior to the completion of radiation therapy, the patient developed progressive disease at local, regional, and distant metastatic sites. Combined modality treatment with radiation and chemotherapy resulted in a significant but transient shrinkage of the tumours at all sites. The patient succumbed to metastatic disease 212 days following the diagnostic biopsy. This case illustrates several of the distinctive clinical and pathological characteristics of this rare tumour.