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Biomedical subjects

B E Johnson

Publications and source records attributed to B E Johnson.

At least 19 recordsLinked to original sources
PubMed1995

Mechanism of inactivation of CDKN2 and MTS2 in non-small cell lung cancer and association with advanced stage.

The CDKN2 tumor suppressor gene encodes an inhibitor of type D cyclin dependent kinases. CDKN2 is homozygously deleted in approximately 25% of nonsmall cell lung cancer (NSCLC) cell lines and these deletions are associated with advanced stage cancer. Conflicting reports of the frequency of CDKN2 alterations in NSCLC tumors prompted us to examine the relationship of these alterations and those of the related gene, MTS2, with patient stage and site of cancer. One hundred twenty-five NSCLC samples (71 cell lines and 54 tumors) were examined by PCR-SSCP. Twenty of 71 (28%) tumor cell lines had homozygous deletions, and six (8%) had point mutations compared to 4 (7%) with point mutations among 54 tumor samples. All mutations were observed in tumors or cell lines from patients with stage III or IV disease. Two patients with no mutations in their primary tumor had a CDKN2 point mutation detected in a metastatic tumor. Point mutations were G:C to T:A transversion on the coding strand in five of 10 and resulted in nonsense mutations in seven of 10. Undetectable CDKN2 mRNA, in the absence of detectable genetic alteration, was noted in a similar fraction of cell lines derived from patients with stage I or II disease [two of seven (29%)] and stage III or IV disease [15 of 49 (31%)]. Homozygous deletion of MTS2 was found in 17 of 20 cell lines with CDKN2 deletions; no point mutations of MTS2 were identified by SSCP in the 125 samples. Thus, CDKN2 is a frequent target of genetic alterations at 9p21 in NSCLC. Both deletions and point mutations of CDKN2 are closely associated with tumor dissemination.

Amino Acid Sequence↗
PubMed1995

CDKN2 in HPV-positive and HPV-negative cervical-carcinoma cell lines.

Human cervical cancers frequently contain retinoblastoma protein (Rb) that is inactivated by binding with human papilloma virus (HPV) E7 protein or through mutation. The CDKN2 gene encodes p16INK4 which inhibits cdk4-cyclin D phosphorylation of Rb, preventing the G1-S transition. To determine whether abnormalities of CDKN2 occur in cervical-cancer cells, II cervical cell lines, including 8 HPV-positive cell lines, 2 HPV-negative cell lines containing mutant Rb, and one tumorigenic cell line derived from normal cervical cells following transfection with HPV-16 and v-H-ras (CX16-2HR), were analyzed. No cell line had a homozygous deletion of exon 1 or 2 of CDKN2, and only one cell line, CX16-2HR, had an altered DNA sequence, which represents a common polymorphism at codon 148. To exclude the possibility of other subtle inactivating mutations, immunoblot analysis of protein lysates was performed using a polyclonal anti-p16INK4 rabbit anti-serum. Abundant levels of normal-sized p16INK4 were observed in all cell samples. Thus, no alterations of CDKN2 were detected in these cervical cell lines. These results confirm that mutational inactivation of p16INK4 is a rare event in tumor samples with compromised Rb activity.

Base Sequence↗
PubMed1995

TP53 and RAS mutations in metachronous tumors from patients with cancer of the upper aerodigestive tract.

Patients who initially develop an upper aerodigestive tract cancer have an increased risk of second primary cancers. We examined TP53 and RAS mutations and p53 protein in 21 tumors from 10 patients with upper aerodigestive tract cancer who developed a metachronous tumor, to assess the genetic changes that occur in multiple primary tumors from the same individual. Thirteen of 21 (62%) tumors were found to have mis-sense mutations of either TP53 or RAS. Six tumors had TP53 mutations in codons 5 to 8 and 10 tumors from 7 patients had mutations of codons 12 or 13 of K-RAS. Only one patient had concordance of a mutation in 2 tumors; this mutation occurred in K-RAS and was accompanied by discordance of TP53 mutation. Three patients had tumors discordant for both TP53 and RAS mutations. Smoking-related tumors had TP53 and RAS mutations which were transversions in 11 (9 G:C to T:A and 2 G:C to C:G) and transitions in 3 (2 G:C to A:T and 1 A:T to G:C). Tumors not associated with smoking contained only transitions (both G:C to A:T). p53 protein was detected by immunohistochemistry in 7 of 13 (54%) tumors and was concordant in the multiple tumors of 3 patients. Three of the 7 tumors staining for p53 also had TP53 mutations. Thus, genetic alterations are discordant in multiple primary cancers and the pattern of mutations is similar to that found in patients with a single primary tumor, supporting the concept that these cancers arise independently.

Adenocarcinoma↗
PubMed1995

Differential inactivation of CDKN2 and Rb protein in non-small-cell and small-cell lung cancer cell lines.

BACKGROUND: The CDKN2 gene encodes the human cyclin-dependent kinase 4 inhibitor. This inhibitor protein is believed to be a tumor suppressor that plays an essential role in cell cycle regulation. One half of all cancer cell lines and one fourth of lung cancer cell lines examined to date contain homozygous deletions (i.e., both alleles lost) of CDKN2. However, the relative frequency of homozygous CDKN2 deletions in non-small-cell lung cancers (NSCLC) and in small-cell lung cancers (SCLC) has not been determined. Inactivation or loss of another tumor suppressor encoded by the retinoblastoma gene (the Rb protein) is more common in SCLC than in NSCLC. PURPOSE: We measured the frequency of homozygous CDKN2 deletions in 77 NSCLC and in 93 SCLC tumor cell lines. In addition, possible associations were explored between CDKN2 gene loss, the presence or absence of Rb protein, and the clinical status of lung cancer patients. METHODS: DNA was isolated from each tumor cell line and from the primary tumor and normal tissue of one NSCLC patient. Sequences corresponding to exons 1 and 2 of the CDKN2 gene were amplified by use of the polymerase chain reaction, and the resulting amplification products were analyzed by agarose gel electrophoresis and DNA blotting. Genomic DNA blotting was also used to evaluate CDKN2 gene deletions. The frequency of homozygous CDKN2 loss and the presence or absence of functional Rb protein (reported previously) in the cell lines were compared. RESULTS: Homozygous deletion of CDKN2 was detected in 18 (23%) of 77 cell lines established from patients with NSCLC, compared with one (1%) of 93 cell lines established from patients with SCLC (P < .001). No CDKN2 gene loss was observed in the normal tissue of an NSCLC patient whose tumor cell line showed homozygous deletion of the gene; however, the primary tumor from this patient had evidence of CDKN2 loss. Homozygous CDKN2 deletion was detected in 13 (28%) of 46 tumor cell lines from patients with stage III or stage IV NSCLC, compared with zero of 10 tumor cell lines from patients with stage I or stage II NSCLC. Coincident loss of CDKN2 genes and functional Rb protein was rarely observed (in two of 135 cell lines). CONCLUSION: The frequency of homozygous CDKN2 gene deletion in NSCLC cell lines is greater than that observed for any other known, or candidate, tumor suppressor gene. IMPLICATION: Further study of the role of CDKN2 gene alteration in the pathogenesis of NSCLC is needed.

Base Sequence↗
PubMed1995

Cloning and characterization of TCTA, a gene located at the site of a t(1;3) translocation.

We have cloned and characterized a novel gene at the site of a t(1;3)(p34;p21) translocation breakpoint in T-cell acute lymphoblastic leukemia. A cDNA for this gene, for which we propose the designation TCTA (T-cell leukemia translocation-associated gene), has been cloned. TCTA mRNA is expressed ubiquitously in normal tissues, with the highest levels of expression seen in the kidney. The TCTA gene is conserved throughout evolution in organisms ranging from Drosophila to humans. A short open reading frame encodes a predicted M(r) 12,000 protein without strong homology to any previously reported proteins. Of note, genomic Southern blots demonstrated a reduced TCTA signal in three of four small cell lung cancer cell lines tested, suggesting loss of one of the two copies of the gene.

Amino Acid Sequence↗
PubMed1995

Biology of small cell lung cancer.

The bombesin-like peptides can function as autocrine growth factors in lung cancer and candidate tumor suppressor genes on chromosomes 3 and 9 play important roles in lung cancer. Bombesin-like peptides can function as mitogens for normal bronchial epithelial cells and lung cancer cell lines. The monoclonal antibody directed against gastrin releasing peptide and bombesin, 2A11, can inhibit the growth of small cell lung cancer in vitro and in vivo and intravenous administration has induced a clinical remission in a patient with relapsed small cell lung cancer. The loss of a portion of one of the two short arms of chromosome 3 (3p) is identified in nearly 100% of tumor cell lines and tumors from patients with small cell lung cancer. Introduction of chromosome 3 into tumor cell lines suppresses their tumorigenicity in athymic nude mice, one of the characteristics of the cancer phenotype. Both copies of the candidate tumor suppressor gene on chromosome 9, CDKN2, are deleted in approximately one-fourth of lung cancer cell lines examined and the protein product of CDKN2, p16 is undetectable in one-third of the lung cancer cell lines studied. The CDKN2 gene is inactivated more commonly in non-small cell lung cancer than small cell lung cancer while the retinoblastoma gene is inactivated more commonly in small cell lung cancer than non-small cell lung cancer. It appears that a single defect in this cell cycle pathway is necessary for unregulated growth in lung cancer and current evidence suggests these defects differ between small cell and non-small cell lung cancer.

Animals↗
PubMed1995

Soft tissue profile: a survey of African-American preference.

Soft tissue profile is a critical area of interest in the development of an orthodontic treatment plan. This study was designed to elicit the current soft tissue profile preference of African-American respondents. Results indicate that: (1) African-American male and female subjects prefer relatively flat profiles, with varied fullness of the lips. (2) African-American male and female subjects prefer the male subjects to have more protrusive profiles than the female subjects. (3) Respondents do not always correctly select their own profile type. (4) More than a third of the respondents desire a change in their own profile.

Adolescent↗
PubMed1995

An analytical evaluation of a new spring design for segmented space closure.

Contemporary segmented-arch space-closure springs require activation techniques that have the side effect of producing a significant amount of geometric nonlinearity. This nonlinearity makes these springs difficult to manipulate because it allows tipping during space closure which may be considered adverse. A new spring mechanism has been designed in response to these difficulties so that the advantages of the segmented-arch technique can be extended to those clinicians presently using simple sliding mechanics as a means of space closure. This spring mechanism has eliminated a significant portion of the geometric nonlinearity by using force-application devices (activators) such as elastics or coil springs as the means of activation. By selecting the right activator it may be possible to close an entire extraction site (approx. 7 mm) with one activation. The proposed mechanism essentially consists of two units: an anchorage unit (M/F = 18 mm), and a translational unit (M/F = 11 mm). These units are combined in order to achieve anterior retraction, posterior protraction, or a combination of the two, which is termed reciprocal-attraction. The finite-element method was used in place of bench studies to test the new spring design. The commonly used reciprocal-attraction spring tested with a nearly constant M/F ratio equal to 11 +/- 1 mm over an effective force range of 50 gm to 450 gm. The results from the other two tests also showed that precisely controlled couple-to-force (M/F) ratios can be maintained over a wide range of effective forces.

Activator Appliances↗
PubMed1995

Risk of second aerodigestive cancers increases in patients who survive free of small-cell lung cancer for more than 2 years.

PURPOSE: Patients who survived small-cell lung cancer (SCLC) for more than 2 years were evaluated to determine the frequency and anatomic pattern of redevelopment of small-cell cancer and development of non-small-cell lung cancer (NSCLC) and aerodigestive cancers with the passage of time. PATIENTS AND METHODS: From April 1973 through December 1991, 578 patients with previously untreated SCLC were entered onto prospective therapeutic trials at the National Cancer Institute (NCI), Bethesda, MD. Sixty-two (11%) were cancer-free 2 years after initiation of therapy and were assessable for redevelopment of SCLC and development of NSCLC, and aerodigestive cancers. RESULTS: Twenty patients redeveloped SCLC 2.0 to 12.2 years after initiation of chemotherapy, of whom two patients were deemed to have a second primary small-cell cancer that involved the aerodigestive tract. Fifteen patients developed 16 cancers in the lung other than SCLC 3.4 to 14.9 years after initiation of therapy. Two developed other aerodigestive cancers that involved the larynx and lip. The risk of a NSCLC and aerodigestive cancer in these patients increased more than sixfold from 2% per patient per year during years 2 to 4 to 12.6% and 14.4%, respectively, after more than 10 years. The cumulative actuarial risk of a second primary NSCLC or aerodigestive cancer at 16 years is 69% and 72%, respectively. CONCLUSION: The increasing risk of second aerodigestive cancers with the passage of time is a mounting problem for patients cured of SCLC. Chemoprevention trials for these patients should be considered.

Adult↗
PubMed1995

Biologic and molecular prognostic factors--impact on treatment of patients with non-small cell lung cancer.

A wide range of genetic and phenotypic abnormalities have been identified in lung cancer. However, only a few are known to have an impact on patient outcome and thus may influence choice of therapy. Biologic and molecular factors known in this regard include the epidermal growth factor family and its receptors, markers of neuroendocrine differentiation in non-small cell lung cancer, and mutations of the ras gene family. None of these factors, however, can be considered a standard for selection of patients for therapy until additional information is gleaned from ongoing prospective studies.

Biomarkers, Tumor↗
PubMed1995

Four-day paclitaxel infusion with cisplatin for patients with lung cancer.

Lung cancer cell lines are between seven and 1,000 times more sensitive to paclitaxel (Taxol; Bristol-Myers Squibb Co, Princeton, NJ) when exposed for 120 hours (5 days) compared with 3-hour exposure. A phase I study of 4-day infusion of paclitaxel plus bolus cisplatin for patients with lung cancer has defined the recommended phase II dose. In this study, paclitaxel infused at 30 mg/m2/d for 4 days followed by a cisplatin bolus of 80 mg/m2 after infusion completion was associated with acceptable hematologic toxicity. Nine of the 16 patients with non-small cell lung cancer treated with at least two cycles of this regimen attained an objective tumor response (one complete response and eight partial responses; overall response rate, 56%). The recommended phase II dose of a 4-day infusion of paclitaxel plus bolus cisplatin followed by the administration of granulocyte colony-stimulating factor has not yet been determined.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1992

Development of antibodies against p53 in lung cancer patients appears to be dependent on the type of p53 mutation.

Using immunoblotting techniques we studied the sera from small cell lung cancer and non-small cell lung cancer patients for antibodies directed against p53. We have also characterized the majority of these patients' tumors for p53 mutations. In the sera of 13% of the patients (4 of 40 small cell lung cancer and 2 of 6 non-small cell lung cancer) we found antibodies specific for the p53 tumor suppressor gene product. All of the antibody-positive patients tested had p53 missense mutations and expressed detectable p53 antigen in their tumor cell lines. No anti-p53 antibodies were detected in sera from patients whose tumor had p53 stop, splice/stop, splice, or frameshift mutations (n = 10). Thus, while we find that the ability of lung cancer patients to develop anti-p53 antibodies is correlated with the type of p53 mutation, many patients have tumors with missense p53 mutations and did not develop anti-p53 antibodies. The presence of p53 antibodies was not correlated to stage, prior treatment, sex, or survival. None of these lung cancer patient sera had measurable amounts of p53 antigen. By immunoblotting all six anti-p53 antisera we were able to detect a variety of mutant p53 proteins (including those from antibody-negative patients) and detected wild-type p53 protein. The development of anti-p53 antibodies represents an interesting model system for studying immune responses in cancer patients against mutant oncogene products.

Adenocarcinoma↗
PubMed1992

Antitumor activity of magainin analogues against human lung cancer cell lines.

Magainin 1 and magainin 2, originally isolated from African clawed frog Xenopus laevis skin, inhibit the growth of bacteria and fungi. Synthetic magainin A (MAG A) and magainin G (MAG G) are more potent against bacteria and protozoa. In order to determine the antitumor activity of these analogues, we have tested these two analogues against six small cell lung cancer (SCLC) cell lines NCI-H82, NCI-H526, NCI-H678, NCI-H735, NCI-H841, and NCI-H889, which were known to differ by more than 10-fold in their sensitivity to different chemotherapeutic agents, and four normal human fibroblast cell lines. Semiautomated 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assays of the six SCLC cell lines revealed average concentrations producing 50% inhibition (IC50) values of 2.6 microM (range, 0.49-9.30 microM) for cisplatin, 2.5 microM (range, 0.39-6.00 microM) for etoposide, and 138.8 nM (range, 55.0-450.0 nM) for doxorubicin. The average IC50 of MAG A was 8.64 microM (range, 6.23-11.7 microM) and that of MAG G was 8.82 microM (range, 4.44-12.5 microM) against the SCLC cell lines. Despite a 10-fold difference in sensitivity to standard chemotherapeutic agents, the IC50 of MAG A and MAG G differs by less than 3-fold. The average IC50 against four normal human fibroblast cell lines was 21.1 microM (range, 12.7-25.6 microM) for MAG A and 29.2 microM (range, 21.3-34.8 microM) for MAG G. Combined exposure to the IC50 concentration of MAG A or MAG G plus IC50 of etoposide or cisplatin decreased the percentage of surviving SCLC cells to 29.0% (range, 26.1-31.7%). MAG A or MAG G had an additive effect when used with standard chemotherapeutic agents. These data suggest that MAG A and MAG G have in vitro antitumor activity against SCLC cell lines.

Antimicrobial Cationic Peptides↗
PubMed1992

In vitro phototoxicity of nifedipine: sequential induction of toxic and non-toxic photoproducts with UVA radiation.

Anecdotal reports suggest that the dihydropyridine calcium antagonist, nifedipine (NIF), may be phototoxic in human skin. We have studied NIF phototoxicity in vitro using UVA fluorescent tubes (Sylvania PUVA). NIF was phototoxic to Candida albicans and induced photohaemolysis both with NIF present during irradiation and with pre-irradiated drug. In V79 hamster fibroblasts, NIF (10 micrograms ml-1) was phototoxic MTT assay) 24 h after irradiation (0-112 kJ m-2); at 7.5 kJ m-2, about 70% of cells were damaged whilst at 37.5 kJ m-2, only about 45% of cells were damaged. A similar pattern was seen with pre-irradiated NIF. Absorption spectroscopy showed that the NIF absorption maximum (Amax approximately 340 nm) blue-shifted to 314 nm at low UVA doses (7.5 kJ m-2 or less) and red-shifted to 345 nm at higher doses (isosbestic point, 325 nm). Thin layer chromatography of irradiated NIF showed a single photoproduct (PP1; Amax approximately 314 nm) formed at 7.5 kJ m-2 or less which disappeared at higher UVA doses to give further photoproducts. PP1 was highly dark toxic to V79 cells (50% damage at about 5 micrograms ml-1) but PP1 pre-irradiated with UVA was non-toxic. Preliminary gas chromatography-mass spectroscopy studies suggest that PP1 is the nitroso derivative of NIF. These results indicate that NIF phototoxicity in vitro is partially mediated by initial formation of a toxic photoproduct (PP1) but, paradoxically, subsequent UVA irradiation may reduce phototoxicity. The NIF concentrations required to induce in vitro phototoxicity are much greater than therapeutic plasma levels. Unless there is skin accumulation of NIF or PP1, our in vitro results suggest that NIF may not be an important skin-photosensitizing agent in vivo.

Animals↗
PubMed1992

Polymorphic sites within the MCC and APC loci reveal very frequent loss of heterozygosity in human small cell lung cancer.

Using single-strand conformation polymorphism we have found two polymorphic sites, AAC to AAT at codon 511 (exon 12) and GCT to GCG at codon 708 (exon 15), in the MCC gene. These sites and an RsaI polymorphic site in APC allowed us to study 23 human small cell lung cancer (SCLC) and 7 non-small cell lung cancer samples for allele loss. Of the 23 SCLC samples, 21 (91%) were informative for one or more of these markers, and we found allele loss in more than 80% (17 of 21). In non-small cell lung cancer samples, 5 of 7 (71%) were informative, and reduction or loss of one allele was found in 2 of 5 (40%). Seven cases were informative for both genes, loss of heterozygosity occurred for both genes in five, one retained heterozygosity for both, and one SCLC had loss of heterozygosity for APC but not for MCC. We conclude that loss of heterozygosity occurs frequently for MCC and APC in lung cancer of all histological types and is very frequent in SCLC. This suggests the presence of tumor suppressor gene(s) in the MCC/APC region of 5q21 involved in human lung cancer.

Base Sequence↗
PubMed1992

Estrogen and progesterone replacement therapy reduces glucocorticoid-induced bone loss.

This is a retrospective study of 15 postmenopausal or amenorrheic women aged 34-78 years who had taken prednisone for 6-108 months and were followed for 1 year while continuing to take doses of 5-15 mg/day. A total of 8 patients were treated with 0.6256 mg Premarin daily for 25 days and 5 mg/day of medroxyprogesterone on days 15-25 (ERT, group 2); 7 were followed without ERT (group 1). A group of 17 women, matched for age, were randomly selected from our computerized data base to serve as a control group (group 3), and 10 women of similar age who were taking ERT only (group 4) were selected to compare the response to ERT to that of group 2. Bone density (BD) was measured in the lumbar spine baseline and at 1 year using dual-photon or dual-energy x-ray absorptiometry. Spine density did not change significantly during the year of observation in group 1. Although BD decreased in 5 of 7 patients, the change was not significant (-0.034 +/- 0.018 g/cm2, p = 0.10). In group 2 BD increased significantly, with 7 of 8 patients showing an increase (0.037 +/- 0.011 g/cm2, p = 0.008). BD did not change significantly in the control group (0.013 +/- 0.008 g/cm2, p = 0.16). Loss of bone from the spine was significantly greater in group 1 than in controls (p = 0.02), but changes in group 2 were similar to those in the control group (p = 0.66).(ABSTRACT TRUNCATED AT 250 WORDS)

Absorptiometry, Photon↗