R-domain interactions with distal regions of CFTR lead to phosphorylation and activation

Cystic fibrosis is caused by the aberrant function of the cystic fibrosis transmembrane conductance regulator (CFTR) protein. We examined whether intramolecular binding interactions involving the regulatory (R) domain contributed to CFTR regulation and function. When the R-domain (amino acids 596-836) was coexpressed with Delta1-836 CFTR (a carboxyl hemi-CFTR beginning immediately after the R-domain), strong binding between the two polypeptides was exhibited. The R-domain that co-immunoprecipitated with Delta1-836 exhibited a slower mobility on SDS-PAGE that resulted from phosphorylation of the protein. A larger CFTR polypeptide that included the R-domain (M837X) also exhibited a phosphorylation-dependent mobility shift when coexpressed with Delta1-836. Moreover, coexpression of M837X and Delta1-836 led to enhanced halide permeability in living cells. The activity, unlike in full-length CFTR, was present without forskolin activation, but still sensitive to the PKA inhibitor, Rp-8-CPT-cAMPS. This PKA inhibition of activity was found to be dependent on the carboxy region of the R-domain, amino acids 723-836. Our results indicate that the R-domain binds CFTR residues after amino acid 836 and that this binding facilitates phosphorylation and CFTR activation. We have also characterized a subdomain within CFTR (residues 723-837) that is necessary for PKA-dependent constitutive activation. Finally, these experiments demonstrate that constitutive CFTR activity can be accomplished by at least two mechanisms: (1) direct modulation of the R-domain to abrogate PKA regulation and (2) modifications that increase R-domain susceptibility to steady-state phosphorylation through PKA.

Margin status and excision of cervical intraepithelial neoplasia: a review

Excisional biopsy of the cervix for diagnosis and treatment of cervical neoplasia is common. Management of patients with involved margins of resection is unresolved. Data concerning use of thermal techniques show that this technique yields equivalent results in most cases. Important exceptions are microinvasive squamous disease and adenocarcinoma. Conservative management of involved squamous margins is possible. Techniques for follow-up include cytology, colposcopy, and endocervical curettage. Adenocarcinoma in situ (AIS) should be treated with cold-knife conization. The standard of care for AIS is hysterectomy except in certain specific indications. Data concerning technique, follow-up, use of endocervical curettage, and the need for reexcision will be presented.

TARGET AUDIENCE

Obstetricians & Gynecologists, Family Physicians.

LEARNING OBJECTIVES

After completion of this article, the reader will be able to compare the efficacy of the various excisional procedures in the treatment of cervical dysplasia, list the indications for additional surgery after positive margins on cervical excisions, and describe the proper management of a patient with adenocarcinoma in situ.

Tricorrectional bunionectomy for hallux abducto valgus. A comprehensive outcome study

A longitudinal outcome study of the tricorrectional bunionectomy with AO screw fixation for the correction of hallux abducto valgus was undertaken involving 84 consecutive patients (121 feet) with a mean age of 48.4 years who underwent the procedure over a 6-month period. Preoperative and postoperative measurements of forefoot angles were calculated, with the following mean results obtained: intermetatarsal angle of 14.46 degrees corrected to 5.72 degrees, hallux abductus angle of 26.38 degrees corrected to 11.65 degrees, proximal articular set angle of 19.85 degrees corrected to 6.06 degrees, and tibial sesamoid position of 4.75 corrected to 1.87. The average time to return to athletic shoes was 12.63 days. Postoperative complications were minor, with no delayed unions, malunions, hematomas, bone infections, or hallux varus. Long-term follow-up (mean, 21.33 months) using the American Orthopaedic Foot and Ankle Society's objective Hallux Metatarsophalangeal-Interphalangeal Scale revealed an overall mean score of 88.94 points out of a possible 100. An excellent mean result of 95 points out of a possible 100 on the subjective patient rating scale was also reported.

Allelotype analysis of uterine leiomyoma: localization of a potential tumor suppressor gene to a 4-cM region of chromosome 7q

Uterine leiomyoma is a benign smooth muscle tumor of the myometrium and is the most commonly encountered neoplasm in women of reproductive age. As for most benign tumors, the pathogenesis of leiomyoma remains obscure, especially at the molecular genetic level. The purpose of this study was to perform a genome-wide allelotype analysis to identify potential sites of tumor suppressor gene inactivation. Fifty-two cases of uterine leiomyoma were subjected to allelotype analysis by using matched pairs of tumor and blood DNA. Loss of heterozygosity (LOH) was assessed at 61 microsatellite markers distributed throughout the genome and representing all 41 chromosome arms. In general, LOH was very rare except on chromosome 7q, where LOH was observed in 34% of all informative tumors. Fine-deletion mapping with 25 microsatellite markers from the 7q22 region revealed a minimal deletion unit of approximately 4 cM, bounded by the markers D7S2453 proximally and D7S496 distally, that probably harbors a novel tumor suppressor gene involved in the etiology of this tumor.

The mechanism underlying cystic fibrosis transmembrane conductance regulator transport from the endoplasmic reticulum to the proteasome includes Sec61beta and a cytosolic, deglycosylated intermediary

Endoplasmic reticulum (ER) degradation pathways can selectively route proteins away from folding and maturation. Both soluble and integral membrane proteins can be targeted from the ER to proteasomal degradation in this fashion. The cystic fibrosis transmembrane conductance regulator (CFTR) is an integral, multidomain membrane protein localized to the apical surface of epithelial cells that functions to facilitate Cl- transport. CFTR was among the first membrane proteins for which a role of the proteasome in ER-related degradation was described. However, the signals that route CFTR to ubiquitination and subsequent degradation are not known. Moreover, limited information is available concerning the subcellular localization of polyubiquitinated CFTR or mechanisms underlying retrograde dislocation of CFTR from the ER membrane to the proteasome either before or after ubiquitination. In the present study, we show that proteasome inhibition with clasto-lactacystin beta-lactone (4 microM, 1 h) stabilizes the presence of a deglycosylated CFTR intermediate for up to 5 h without increasing the core glycosylated (band B) form of CFTR. Deglycosylated CFTR is present under the same conditions that result in accumulation of polyubiquitinated CFTR. Moreover, the deglycosylated form of both wild type and DeltaF508 CFTR can be found in the cytosolic fraction. Both the level and stability of cytosolic, deglycosylated CFTR are increased by proteasome blockade. During retrograde translocation from the ER to the cytosol, CFTR associates with the Sec61 trimeric complex. Sec61 is the key component of the mammalian co-translational protein translocation system and has been proposed to function as a two way channel that transports proteins both into the ER and back to the cytosol for degradation. We show that the level of the Sec61.CFTR complexes are highest when CFTR degradation proceeds at the greatest rate (approximately 90 min after pulse labeling). Quantities of Sec61.CFTR complexes are also increased by inhibition of the proteasome. Based on these results, we propose a model in which complex membrane proteins such as CFTR are transported through the Sec61 trimeric complex back to the cytosol, escorted by the beta subunit of Sec61, and degraded by the proteasome or by other proteolytic systems.

Cystic fibrosis transmembrane conductance regulator (CFTR) nucleotide-binding domain 1 (NBD-1) and CFTR truncated within NBD-1 target to the epithelial plasma membrane and increase anion permeability

The cystic fibrosis transmembrane conductance regulator (CFTR) is a member of the traffic ATPase family that includes multiple proteins characterized by (1) ATP binding, (2) conserved transmembrane (TM) motifs and nucleotide binding domains (NBDs), and (3) molecular transport of small molecules across the cell membrane. While CFTR NBD-1 mediates ATP binding and hydrolysis, the membrane topology and function of this domain in living eukaryotic cells remains uncertain. In these studies, we have expressed wild-type CFTR NBD-1 (amino acids 433-586) or NBD-1 containing the DeltaF508 mutation transiently in COS-7 cells and established that the domain is situated across the plasma membrane by four independent assays; namely, extracellular chymotrypsin digestion, surface protein biotinylation, confocal immunofluorescent microscopy, and functional measurements of cell membrane anion permeability. Functional studies indicate that basal halide permeability is enhanced above control conditions following wild-type or DeltaF508 NBD-1 expression in three different epithelial cell lines. Furthermore, when clinically relevant CFTR proteins truncated within NBD-1 (R553X or G542X) are expressed, surface localization and enhanced halide permeability are again established. Together, these findings suggest that isolated CFTR NBD-1 (with or without the DeltaF508 mutation) is capable of targeting the epithelial cell membrane and enhancing cellular halide permeability. Furthermore, CFTR truncated at position 553 or 542 and possessing the majority of NBD-1 demonstrates surface localization and also confers increased halide permeability. These findings indicate that targeting to the plasma membrane and assumption of a transmembrane configuration are innate properties of the CFTR NBD-1. The results also support the notion that components of the halide-selective pore of CFTR reside within NBD-1.

Cell to cell contact is not required for bystander cell killing by Escherichia coli purine nucleoside phosphorylase

Expression of Escherichia coli purine nucleoside phosphorylase (PNP) activates prodrugs and kills entire populations of mammalian cells, even when as few as 1% of the cells express this gene. This phenomenon of bystander killing has been previously investigated for herpes simplex virus-thymidine kinase (HSV-TK) and has been shown to require cell to cell contact. Using silicon rings to separate E. coli PNP expressing cells from non-expressing cells sharing the same medium, we demonstrate that bystander cell killing by E. coli PNP does not require cell-cell contact. Initially, cells expressing E. coli PNP convert the non-toxic prodrug, 6-methylpurine-2'-deoxyriboside (MeP-dR) to the highly toxic membrane permeable toxin, 6-methylpurine (MeP). As the expressing cells die, E. coli PNP is released into the culture medium, retains activity, and continues precursor conversion extracellularly (as determined by reverse phase high performance liquid chromatography of both prodrug and toxin). Bystander killing can also be observed in the absence of extracellular E. coli PNP by removing the MeP-dR prior to death of the expressing cells. In this case, 100% of cultured cells die when as few as 3% of the cells of a population express E. coli PNP. Blocking nucleoside transport with nitrobenzylthioinosine reduces MeP-dR mediated cell killing but not MeP cell killing. These mechanisms differ fundamentally from those previously reported for the HSV-TK gene.

Cycles of dose-intensive chemotherapy with peripheral stem cell support in persistent or recurrent platinum-sensitive ovarian cancer

OBJECTIVE

The objective was to determine the toxicity and surgically documented response rate of sequential high-dose chemotherapy with peripheral stem cell support in patients with persistent or recurrent cisplatin-sensitive ovarian cancer.

METHODS

Fourteen patients (average age, 45 years) were treated with cyclophosphamide (4.5 g/m2), followed by granulocyte colony-stimulating factor (G-CSF)-stimulated peripheral stem cell harvests. The subsequent regimen prescribed three courses of carboplatin (1 g/m2) and cyclophosphamide (1.5 g/m2 with 2-mercaptoethanesulfonate) every 2 weeks with stem cell support. This was followed by three courses of paclitaxel at 250 mg/m2 every 2 weeks with G-CSF support only. Six patients were entered on the basis of a positive second-look laparotomy and 8 patients had a first recurrence after at least a 6-month disease-free interval.

RESULTS

Fourteen patients were entered and 12 patients completed all planned courses of therapy (mean time, 13 weeks). Normal hematopoiesis was reestablished after each cycle. Hospitalization for neutropenic fever occurred in 11/93 cycles (11.8%). Thirteen patients required blood transfusions and in 12 patients platelet transfusions were given. One patient had grade 3 neurotoxicity. An initial elevated CA 125 returned to normal in 7/8 patients (88%) and 71% of patients with measurable disease responded to therapy. There were 2 pathologic complete responders (PCR), making the PCR rate 2/14 or 14% (0-35%).

CONCLUSION

Although this regimen was well tolerated and clinical response rates were high, the surgically documented response rate was not clearly superior to conventional salvage regimens in platinum-sensitive patients.

In vivo gene therapy of cancer with E. coli purine nucleoside phosphorylase

We have developed a new strategy for the gene therapy of cancer based on the activation of purine nucleoside analogs by transduced E. coli purine nucleoside phosphorylase (PNP, E.C. 2.4.2.1). The approach is designed to generate antimetabolites intracellularly that would be too toxic for systemic administration. To determine whether this strategy could be used to kill tumor cells without host toxicity, nude mice bearing human malignant D54MG glioma tumors expressing E. coli PNP (D54-PNP) were treated with either 6-methylpurine-2'-deoxyriboside (MeP-dR) or arabinofuranosyl-2-fluoroadenine monophosphate (F-araAMP, fludarabine, a precursor of F-araA). Both prodrugs exhibited significant antitumor activity against established D54-PNP tumors at doses that produced no discernible systemic toxicity. Significantly, MeP-dR was curative against this slow growing solid tumor after only 3 doses. The antitumor effects showed a dose dependence on both the amount of prodrug given and the level of E. coli PNP expression within tumor xenografts. These results indicated that a strategy using E. coli PNP to create highly toxic, membrane permeant compounds that kill both replicating and nonreplicating cells is feasible in vivo, further supporting development of this cancer gene therapy approach.

Relationship of preoperative antiendotoxin core antibodies and adverse outcomes following cardiac surgery

OBJECTIVE

To test the hypothesis that low serum antiendotoxin core antibody (EndoCAb) level is an independent predictor of adverse outcome following cardiac surgery.

DESIGN

Prospective, blinded, cohort study.

SETTING

Tertiary care medical center.

SUBJECTS

A total of 301 patients undergoing coronary artery bypass graft surgery and/or valvular heart surgery.

DESIGN

Preoperative serum was assayed for IgM EndoCAb, IgG EndoCAb, total IgM, and total IgG levels. Known preoperative risk factors were assessed, and patients were assigned a risk score using a validated method.

MAIN OUTCOME MEASURE

A major complication, defined as either in-hospital death or postoperative length of stay greater than 10 days.

RESULTS

Overall, a major complication occurred in 34 patients (11.3%). Lower IgM EndoCAb level independently predicted (P=.002) increased risk of major complication over and above the effects of preoperative risk score (P=.02), total IgG level (P=.07), and all other known perioperative risk factors. In contrast, IgG Endo-CAb and total IgM concentrations did not predict outcome. No association existed between risk score and level of IgM EndoCAb.

CONCLUSION

There is marked preoperative variability in humoral immunity against endotoxin core, which is not accounted for by differences in known preoperative risk factors. In this study, low levels of IgMEndoCAb were an important independent predictor of adverse postoperative outcome, which supports the theory that endotoxemia is a cause of postoperative morbidity.

Deletion mapping of two potential chromosome 14 tumor suppressor gene loci in ovarian carcinoma

Previous allelotyping studies of epithelial ovarian carcinoma suggest that loss of heterozygosity on chromosome 14q may be a common genetic alteration in this tumor type. The purpose of this study was to determine a precise frequency of chromosome 14q allelic loss in ovarian carcinomas and to define a minimal region(s) of deletion. Seventy-six ovarian carcinomas representative of the complete spectrum of grade, stage, and histological subtype were selected for PCR-based deletion mapping analysis using 15 highly polymorphic microsatellite markers spanning the length of this chromosome arm. Loss of heterozygosity was observed in 49% of the tumors studied, placing 14q among the most frequently affected chromosomal regions in ovarian cancer. Deletions were observed in all tumor grades and stages and in all histological subtypes except tumors of low malignant potential. Deletion of the entire chromosome arm was rare; the majority of tumors displayed partial losses, providing an informative basis for detailed deletion mapping. Two distinct minimal regions of deletion were delineated. One region was defined by markers D14S80 and D14S75 at 14q12-13, and the other region was defined by markers D14S65 and D14S267 at 14q32. These data implicate the involvement of two tumor suppressor genes on chromosome 14q in a substantial fraction of ovarian carcinomas.

Depression and pain: Assessment and therapeutic strategies

Many patients with pain also suffer from depression. The exact relationship between these two problems is unclear but it appears that, in many patients, the depression may not simply be secondary to the pain. When these problems coexist, successful management requires the proper assessment and treatment of both. This paper discusses depressive disorders associated with pain and their treatment, with special focus on medication management.

Effect of surgical debulking on survival in stage IV ovarian cancer

In order to determine whether optimal surgical debulking in Stage IV epithelial ovarian cancer impacts survival, a retrospective review of patients treated at the University of Pennsylvania Cancer Center (UPCC) from 1984 to 1995 diagnosed with Stage IV epithelial ovarian cancer was performed. Data were collected regarding grade, histology, reason for allocation to Stage IV, extent of surgery performed and residual disease at initial staging procedure, major perioperative complications, first-line chemotherapy regimen, length of inpatient hospital stay, outcome at second-look laparotomy, follow-up, and survival. For the purposes of this study, optimal cytoreduction was defined as a residual disease of 2 cm or less. Forty-seven patients with Stage IV epithelial ovarian cancer identified in the Society of Gynecologic Oncologists (SGO) Database at UPCC are included. Fourteen of 47 (30%) were optimally cytoreduced at the time of their staging procedure. Twenty-six of 47 (55%) were deemed Stage IV by virtue of positive pleural effusion cytology only. Twenty-one of 47 (45%) had intraparenchymal liver involvement or metastatic disease outside of the abdomen. The median survival of the suboptimally debulked group was 17 months, while median survival in the optimal group was 37 months (P = 0.0295). These data suggest that Stage IV epithelial ovarian cancer patients with less than 2 cm residual disease have a survival advantage over patients with greater than 2 cm residual.

Racial differences in survival from gynecologic cancer

OBJECTIVE

To determine whether survival from gynecologic cancer is different between African-American and white patients at an inner-city hospital with both a large clinic and a private service.

METHODS

We studied 538 patients (89 African American, 449 white) diagnosed with cervical, uterine, or ovarian cancer at a single institution from January 1, 1989 through December 31, 1993. Information was obtained on age, stage, site of disease, histology, and type of health insurance (public or commercial). Insurance coverage was used as a proxy for socioeconomic status. Overall survival was estimated by the method of Kaplan and Meier and compared by the log-rank test. Cox proportional hazard modeling was used to evaluate the effects of multiple factors on survival.

RESULTS

African-American patients were significantly older and were more likely to have cervical cancer and public insurance than white patients. Overall survival was worse for African-American patients than for white patients (P < .05). However, stage for stage, there was no significant difference in survival between the groups. There was also no difference when patients were grouped by insurance status. African Americans had a significantly worse survival for cervical cancer than whites, and African-American patients older than 65 years had a worse survival than whites of similar age. On multivariate analysis, only stage and insurance coverage were significant predictors of survival.

CONCLUSIONS

African-American patients with gynecologic cancer at our institution have worse overall survival than white patients. The survival difference seems to be due predominantly to differences in socioeconomic status and stage at diagnosis.