Somatic Epigenetic Silencing of RIPK3 Inactivates Necroptosis and Contributes to Chemoresistance in Malignant Mesothelioma

PURPOSE

Receptor-interacting protein kinase 3 (RIPK3) phosphorylates effector molecule MLKL to trigger necroptosis. Although RIPK3 loss is seen in several human cancers, its role in malignant mesothelioma is unknown. This study aimed to determine whether RIPK3 functions as a potential tumor suppressor to limit development of malignant mesothelioma.

EXPERIMENTAL DESIGN

RIPK3 expression was examined in 66 malignant mesothelioma tumors and cell lines. Promoter methylation and DNMT1 siRNA studies were performed to assess the mode of RIPK3 silencing in RIPK3-deficient malignant mesothelioma cells. Restoration of RIPK3 expression in RIPK3-negative malignant mesothelioma cells, either by treatment with 5-aza-2'-deoxycytidine or lentiviral expression of cDNA, was performed to assess effects on cell viability, necrosis, and chemosensitization.

RESULTS

Loss of RIPK3 expression was observed in 42/66 (63%) primary malignant mesotheliomas and malignant mesothelioma cell lines, and RT-PCR analysis demonstrated that downregulation occurs at the transcriptional level, consistent with epigenetic silencing. RIPK3-negative malignant mesothelioma cells treated with 5-aza-2'-deoxycytidine resulted in reexpression of RIPK3 and chemosensitization. Ectopic expression of RIPK3 also resulted in chemosensitization and led to necroptosis, the latter demonstrated by phosphorylation of downstream target MLKL and confirmed by rescue experiments. Mining of RIPK3 expression and survival outcomes among patients with malignant mesothelioma available from The Cancer Genome Atlas repository revealed that promoter methylation of RIPK3 is associated with reduced RIPK3 expression and poor prognosis.

CONCLUSIONS

These data suggest that RIPK3 acts as a tumor suppressor in malignant mesothelioma by triggering necroptosis and that epigenetic silencing of RIPK3 by DNA methylation impairs necroptosis and contributes to chemoresistance and poor survival in this incurable disease.

Postoperative management: buttock claudication and limb thrombosis

As a result of endovascular repair of abdominal aortic aneurysms and the necessary associated adjunctive procedures, postoperative buttock claudication and limb thrombosis are complications that every physician who implants stent-grafts should be able to recognize and treat. Whereas the presenting complaints of these complications can be quite obvious, the treatment of them may be not so simple. Studies have shown that 28% of patients who underwent embolization of one or both hypogastric arteries develop buttock claudication. Yet 78% of these affected patients spontaneously resolve their symptoms. Strategies to both minimize and successfully treat this complication are obviously of the utmost importance. Likewise, limb thrombosis can be easy to recognize, but treatment strategies and methods to limit this complication can be quite complex and remain somewhat controversial. One center was able to reduce their limb thrombosis rate from 17% to 0% through the use of intravascular ultrasound and aggressive adjunctive stenting. The purpose of this article is to first review the data concerning these complications and then to discuss treatment strategies that are designed to minimize and treat the actual complication.

Troubleshooting techniques for abdominal aortic aneurysm endograft placement: when things go wrong

Since the Food and Drug Administration approved the Ancure (Guidant Corp, Menlo Park, CA) and AneuRx (Medtronic Corp, Minneapolis, MN) abdominal aortic aneurysm stent-grafts, there has been a tremendous increase in the number of stent-graft implantations, both in the United States and worldwide. Successful stent-graft deployment requires complex interventional skills and accurate preprocedure planning. Even the most skilled operator may experience intraoperative difficulties during graft deployment. There are intraprocedural complications that are common to all stent-grafts, as well as specific complications that are unique to the particular stent-graft being implanted. The first step to managing an intraprocedural complication is to be able to quickly recognize that a deployment difficulty has occurred. The interventionalist must then be ready to use common troubleshooting techniques to rectify or avoid complications of stent-graft delivery.

MR assessment of the extremity veins

This article provides an overview of the technique of magnetic resonance venography (MRV) and its relative value in the diagnostic work-up of suspected lower or upper extremity venous thrombosis. MRV is accurate for diagnosis or exclusion of deep vein thrombosis. MRV should be considered complimentary, in many instances, to the less expensive modality of venous sonography. It is the complimentary use of magnetic resonance techniques at the level of the pelvis and the mediastinum that offers the greatest cost benefit as part of an incremental strategy for the work-up of patients presenting with lower or upper extremity swelling.

Trends in the use of radiology with inpatients: what has changed in a decade?

OBJECTIVE

Our goal was to evaluate trends in the use of radiology with inpatients in the 10-year period of 1984-1993.

MATERIALS AND METHODS

We retrospectively reviewed administrative data from a 751-bed, tertiary care hospital between October 1, 1983, and September 30, 1993 (Fiscal years 1984-1993). We coded each study by imaging technique: CT, MR imaging, sonography, nuclear medicine, or conventional studies (plain films and fluoroscopy). Echocardiography, cardiac catheterization, and angioplasty procedures were omitted. The number of admissions per year was adjusted for severity of disease (case-mix-adjusted admission [CMA]). We used relative value units to evaluate workload changes during the study period. We assessed significance of trends using linear regression analysis.

RESULTS

The total number of imaging studies per CMA decreased during the study period (p = .0001). This was due to a decrease in the number of conventional studies (p = .0001) and sonograms per CMA (p = .02), despite significant increases in the numbers of CT (p = .005) and MR imaging (p = .0001) studies per CMA. No significant change existed in the number of nuclear medicine studies per CMA (p = .11). The global, professional, and technical relative value units per CMA rose during the latter half of the study.

CONCLUSION

The overall number of imaging studies per CMA decreased during the decade, despite a significant rise in the use of CT and MR imaging, suggesting that these new imaging techniques are replacing older ones. To control further increases in overall imaging costs, priority should be placed on understanding the patterns of use for CT and MR imaging techniques and curbing their inappropriate use.

Spiral CT in the evaluation of flank pain: overall accuracy and feature analysis

PURPOSE

Our goal was to assess test reliability and identify those features that have the strongest positive and negative predictive values in the diagnosis of renal colic using spiral CT.

METHOD

Fifty non-contrast-enhanced CT scans (5 mm slice thickness) obtained in patients presenting with flank pain were reviewed by three radiologists blinded to the final diagnoses. The sensitivity, specificity, and positive and negative predictive values for nine pertinent findings were determined as compared to clinical follow-up.

RESULTS

Twenty-nine cases had findings of ureteral obstruction. Findings with the strongest positive predictive values (> 0.90) were ureteral stone, hydronephrosis, hydroureter, periureteral stranding, and ureterovesical junction edema. Findings with the strongest negative predictive values (> 0.89) were absence of hydronephrosis and hydroureter. The areas under the receiver operating curves for Readers 1, 2, and 3 were 0.970 +/- 0.030, 0.942 +/- 0.036, and 0.982 +/- 0.020.

CONCLUSION

Absence of hydroureter and hydronephrosis on spiral CT images should prompt a search for a diagnosis other than an obstructing ureteral stone.

Spiral computerized tomography in the evaluation of acute flank pain: a replacement for excretory urography

PURPOSE

We determined the value of noncontrast enhanced spiral computerized tomography (CT) in the evaluation of suspected renal colic.

MATERIALS AND METHODS

Thin section (5 mm.) noncontrast enhanced CT was used to evaluate 100 patients presenting to the emergency room with flank pain. The 55 patients with ureteral obstruction were followed at the urology outpatient clinic and by telephone interview, while 45 without ureteral obstruction were followed by telephone interview and chart review. Sensitivity, specificity, and positive and negative predictive values for CT were determined, with passage, retrieval or identification of a stone on a retrograde study considered the gold standard for diagnosis.

RESULTS

A total of 89 patients had adequate clinical followup to assess outcome accurately. Of 55 patients with ureteral obstruction on CT 11 underwent endoscopic stone removal, while 44 were treated conservatively with stone passage documented in 39. Of the 45 patients without ureteral stones identified 38 did not pass calculi and CT provided a definite diagnosis in 14. There was 1 false-negative study. The results yielded 98% sensitivity, 100% specificity, and 100% positive and 97% negative predictive values.

CONCLUSIONS

Noncontrast enhanced spiral CT was accurate and reliable in detecting obstructing ureteral calculi in patients with flank pain.

Neurologic anomalies of Perrault syndrome

We report on an 18-year-old man with neurosensory hearing loss and his sister with neurosensory hearing loss, ovarian dysgenesis, mental retardation, generalized ataxia of the trunk and limbs, and saccadic dysmetria. A CT scan showed cerebellar hypoplasia. The cardinal manifestations of Perrault syndrome in females are neurosensory hearing loss and ovarian dysgenesis. Other anomalies, including neurologic and skeletal, have been reported in other individuals with Perrault syndrome. We review the neurologic anomalies in previous patients with Perrault syndrome. Neurologic data are available on 14 of 21 girls; 7 of 14 had neurologic abnormalities. The high incidence of neurologic anomalies suggest that ataxia or mental retardation may not be just coincidental findings, but pleiotropic manifestations of Perrault syndrome.

Diagnostic performance of CT, MPR and 3DCT imaging in maxillofacial trauma

CT imaging of complex maxillofacial fractures is common practice now, but the relative diagnostic value of spiral computed tomography (CT), multiplanar reformations (MPR), and three-dimensional (3D) reconstructions in evaluating maxillofacial fractures is not established with independent validation of correct diagnosis. We studied these modalities and measured their diagnostic value in a carefully controlled observer based rated response experiment. Multiple fractures were created by blunt experimental trauma in nine adult cadaver heads (five males, four females). Spiral CT scans were performed on all specimens before (control) and after trauma. Axial slices (CT), sagittal and coronal multiplanar reconstructions (MPR), and 3D volumetric reconstructions views were generated. Truth was determined by defleshing the specimens and direct inspection of the traumatized skull. Three expert readers separately interpreted CT, MPR and 3D film hard copy images presented in random order blinded to patient identification or experimental conditions. We measured the time to diagnose each case as recorded by a monitor who was present while evaluations were performed. Twenty-eight facial regions were evaluated using rated response and free response illustrative formats. Each region was considered separately. Sensitivity and specificity were calculated to measure observer performance. We found that 3D and CT had a similar performance in fracture detection and both were markedly better than MPR. For free response illustrative data, CT correctly identified 10% more orbital fractures than 3D, and approximately 10% fewer zygomatic fractures. Fracture localization was best with 3D. Reader confidence was highest with CT, but assessment time was faster with 3D. We conclude that CT and 3D are comparable in detecting midfacial fractures and both are superior to MPR. 3D reconstructions are superior for localization of complex fractures involving multiple planes.

Chest radiography in patients with early stage prostatic carcinoma. Effect on treatment planning and cost analysis

STUDY OBJECTIVE

An evaluation of the impact of routine preoperative chest radiographs was retrospectively undertaken in a pilot group of 292 patients with prostatic carcinoma who were part of a prospective study of prostate specific antigen screening for prostate carcinoma.

DESIGN

Retrospective.

SETTING

Hospital-based outpatients.

PATIENTS AND PARTICIPANTS

A cost-effectiveness model was used to assess the value of routine chest radiography in this patient population. Chest radiography findings were categorized into four groups based on follow-up and impact.

MEASUREMENTS AND RESULTS

Forty-three patients (15 percent) had a total of 45 positive findings on their chest radiographs. No patient had intrathoracic metastases from prostatic carcinoma. Only two patients (both with unsuspected second neoplasms) had findings that impacted on their treatment and one avoided retropubic radical prostatectomy. Total cost was $2,000 (based on Medicare reimbursement), or $14,000 (based on physician and hospital charges).

CONCLUSION

Although benefit is small in terms of number of patients affected, clinical impact, in the two patients with significant findings, was great. Although cost-effectiveness cannot be confirmed on the basis of this series, further evaluation of its utility for this application should be undertaken.

Kinesin-related proteins in eukaryotic flagella

To identify kinesin-related proteins that are important for ciliary and eukaryotic flagellar functions, we used affinity-purified, polyclonal antibodies to synthetic peptides corresponding to conserved sequences in the motor domain of kinesin (Sawin et al. (1992) J. Cell Sci. 101, 303–313). Using immunoblot analysis, two antibodies to distinct sequences (LNLVDLAGSE, ‘LAGSE’ and, HIPYRESKLT, ‘HIPYR’) reveal a family of proteins in flagella and axonemes isolated from Chlamydomonas. Similar analysis of axonemes from mutant Chlamydomonas strains or fractionated axonemes indicates that none of the immunoreactive proteins are associated with dynein arm or spoke structures. In contrast, one protein, approximately 110 kDa, is reduced in axonemes from mutant strains defective in the central pair apparatus. Immunoreactive proteins with masses of 96 and 97 kDa (the ‘97 kDa’ proteins) are selectively solubilized from isolated axonemes in 10 mM ATP. The 97 kDa proteins co-sediment in sucrose gradients at about 9 S and bind to axonemes or purified microtubules in a nucleotide-dependent fashion characteristic of kinesin. These results reveal that flagella contain kinesin-related proteins, which may be involved in axonemal central pair function and flagellar motility, or directed transport involved in morphogenesis or mating responses in Chlamydomonas.

CT screening for comorbid disease in patients with prostatic carcinoma: is it cost-effective?

OBJECTIVE

The role of imaging in patients with newly diagnosed prostatic carcinoma is controversial. Currently, 35% of patients with prostatic carcinoma undergo CT at the time of diagnosis, despite reports of the lack of efficacy of CT in staging the disease. We sought to evaluate the cost-effectiveness of CT in detecting unrelated comorbid disease (significant disease unrelated to prostatic carcinoma) that might affect decisions on treatment in this population of patients.

MATERIALS AND METHODS

We reviewed the medical records of 273 consecutive patients with newly diagnosed prostatic carcinoma who had CT of the abdomen and pelvis as part of their preoperative evaluation. Using costs based on Medicare reimbursements, we assessed the impact of the CT findings (related to comorbid disease) on overall costs and savings related to the workup and treatment of these patients.

RESULTS

Sixty-six patients (24%) had findings suggestive of comorbid disease. The CT findings had near-term impact on only four patients (two in whom large abdominal aortic aneurysms were detected and two in whom second primary cancers were found), despite nearly $155,000 spent on the screening CT scans and more than $4400 spent on further evaluation of false-positive CT findings. The clinical impact varied from intervening semiurgent surgery to cancellation of prostatic surgery and institution of radiation therapy.

CONCLUSION

CT is not cost-effective in screening for comorbid disease that would affect treatment in patients with newly diagnosed prostatic carcinoma.

The alpha subunit of sea urchin sperm outer arm dynein mediates structural and rigor binding to microtubules

Glass-adsorbed intact sea urchin outer arm dynein and its beta/IC1 subunit supports movement of microtubules, yet does not form a rigor complex upon depletion of ATP (16). We show here that rigor is a feature of the isolated intact outer arm, and that this property subfractionates with its alpha heavy chain. Intact dynein mediates the formation of ATP-sensitive microtubule bundles, as does the purified alpha heavy chain, indicating that both particles are capable of binding to microtubules in an ATP-sensitive manner. In contrast, the beta/IC1 subunit does not bundle microtubules. Bundles formed with intact dynein are composed of ribbon-like sheets of parallel microtubules that are separated by 54 nm (center-to-center) and display the same longitudinal repeat (24 nm) and cross-sectional geometry of dynein arms as do outer doublets in situ. Bundles formed by the alpha heavy chain are composed of microtubules with a center-to-center spacing of 43 nm and display infrequent, fine crossbridges. In contrast to the bridges formed by the intact arm, the links formed by the alpha subunit are irregularly spaced, suggesting that binding of the alpha heavy chain to the microtubules is not cooperative. Cosedimentation studies showed that: (a) some of the intact dynein binds in an ATP-dependent manner and some binds in an ATP-independent manner; (b) the beta/IC1 subunit does not cosediment with microtubules under any conditions; and (c) the alpha heavy chain cosediments with microtubules in the absence or presence of MgATP2-. These results suggest that the structural binding observed in the intact arm also is a property of its alpha heavy chain. We conclude that whereas force-generation is a function of the beta/IC1 subunit, both structural and ATP-sensitive (rigor) binding of the arm to the microtubule are mediated by the alpha subunit.

An ethical dilemma: coding medical records for reimbursement

Coding accuracy is difficult enough with inconsistent and incomplete medical records adding to the challenge. But since the HCFA implementation of DRGs in 1983 to determine Medicare payments, coding has taken on an ethical dimension. In this article Leslie Ann Fox discusses the causes underlying this dilemma and proposes some solutions.

The key is teamwork: making medical records information systems succeed

Problems within an existing hospital information system can often hamper efforts of medical records personnel to perform chart completion, clinical abstracting, tracking, deficiency analysis and other essential tasks. Years of experience have enabled Leslie Ann Fox, consultant for Care Communications, Inc., to collect observations, and through them, recommend key success factors to make the system work well.

The association of chronic inflammatory disease in lichen planus with cancer of the oral cavity

Heavy cigarette smoking and alcohol consumption are the major contributing factors in the development of cancer of the upper aerodigestive tract. Other factors, such as chewing substances and chronic irritation, have been implicated. The purpose of this presentation is to draw attention to chronic inflammation as another likely etiologic factor in the pathogenesis of oral cavity cancer. During the past 4 years, we diagnosed squamous cell carcinoma of the oral cavity in six consecutive patients who had no history of cigarette smoking, alcohol intake, or substance abuse. Although this series is too small for significant analysis, it does suggest that chronic inflammatory processes such as lichen planus and chronic gingivitis can induce neoplastic metaplasia in the epithelium of the oral cavity.

Isolated beta-heavy chain subunit of dynein translocates microtubules in vitro

Our goal was to assess the microtubule translocating ability of individual ATPase subunits of outer arm dynein. Solubilized outer arm dynein from sea urchin sperm (Stronglocentrotus purpuratus) was dissociated into subunits by low ionic strength buffer and fractionated by zonal centrifugation. Fractions were assessed by an in vitro functional assay wherein microtubules move across a glass surface to which isolated dynein fractions had been absorbed. Microtubule gliding activity was coincident with the 12-S beta-heavy chain-intermediate chain 1 ATPase fractions (beta/IC1). Neither the alpha-heavy chain nor the intermediate chains 2 and 3 fractions coincided with microtubule gliding activity. The beta/IC1 ATPase induced very rapid gliding velocities (9.7 +/- 0.88 micron/s, range 7-11.5 micron/s) in 1 mM ATP-containing motility buffers. In direct comparison, isolated intact 21-S outer arm dynein, from which the beta/IC1 fraction was derived, induced slower microtubule gliding rates (21-S dynein, 5.6 +/- 0.7 micron/s; beta/IC1, 8.7 +/- 1.2 micron/s). These results demonstrate that a single subdomain in dynein, the beta/IC1 ATPase, is sufficient for microtubule sliding activity.

Direction of force generated by the inner row of dynein arms on flagellar microtubules

Our goal was to determine the direction of force generation of the inner dynein arms in flagellar axonemes. We developed an efficient means of extracting the outer row of dynein arms in demembranated sperm tail axonemes, leaving the inner row of dynein arms structurally and functionally intact. Sperm tail axonemes depleted of outer arms beat at half the beat frequency of sperm tails with intact arms over a wide range of ATP concentrations. The isolated, outer arm-depleted axonemes were induced to undergo microtubule sliding in the presence of ATP and trypsin. Electron microscopic analysis of the relative direction of microtubule sliding (see Sale, W. S. and P. Satir, 1977, Proc. Natl. Acad. Sci. USA, 74:2045-2049) revealed that the doublet microtubule with the row of inner dynein arms, doublet N, always moved by sliding toward the proximal end of the axoneme relative to doublet N + 1. Therefore, the inner arms generate force such that doublet N pushes doublet N + 1 tipward. This is the same direction of microtubule sliding induced by ATP and trypsin in axonemes having both inner and outer dynein arms. The implications of this result for the mechanism of ciliary bending and utility in functional definition of cytoplasmic dyneins are discussed.

The influence of fibroblast-like cells derived from canine fetal hematopoietic tissues on the regulation of lymphohematopoiesis

Media conditioned by fibroblast-like cells derived from organs active in fetal lymphohematopoiesis were studied for their effects on adult granulocyte/macrophage colony-forming units (CFU-GM). Fibroblasts from fetal liver produced a factor stimulatory for CFU-GM, whereas fibroblasts from fetal marrow produced a factor inhibitory for CFU-GM which was not completely relieved by adding indomethacin to the assay. Our studies indicated that neither fetal marrow nor fetal liver produced factors affecting lymphocyte colony-forming units (CFU-L). Cell-cell interactions between fibroblast-like cells derived from fetal liver or marrow and normal adult CFU-GM were also studied. We observed that fibroblasts derived from both fetal and adult marrow inhibited colony formation, whereas inhibition in the presence of fetal liver fibroblasts was minimal. Loss of inhibitory activity by a liver fibroblast cell line over repeated passages was seen. Differential analysis of colonies formed above an adherent layer of fetal marrow fibroblasts suggested that these fibroblasts suppress myeloid/macrophage differentiation to a far greater degree than did adult marrow fibroblasts. A role in the regulation of fetal lymphohematopoiesis may be played by stromal fibroblasts.

Characterization of canine fetal lymphohematopoiesis: studies of CFUGM, CFUL, and CFUF

We assayed the colony forming units for granulocyte-macrophages (CFUGM), T-lymphocytes (CFUL) and fibroblasts (CFUF) in the blood, bone marrow, liver and spleen of the canine at 45 and 55 days of gestation and 4 and 30 days post partum. As the number of CFUGM per 5 x 10(5) cells increased in the fetal liver, the number of CFUGM increased in circulating blood, whereas when the number of CFUGM decreased in liver and blood, CFUGM increased in both bone marrow and spleen. This suggests that CFUGM are produced in the liver, are released into the circulation and then transported to the spleen and bone marrow. CFUF studies showed that canine fetal bone marrow and spleen are active sites of fibroblast proliferation, whereas the liver is not. Morphologic examination of colonies derived from concanavalin-A stimulated progenitors ("CFUL") demonstrated that these colonies from fetal tissues and adult bone marrow were not exclusively lymphoid but were also made up of significant numbers of precursors of the myeloid and monocytic series. Lymphocyte stimulation tests (LST) showed the presence of a large population of mitogen-independent dividing cells, suggesting that fetal lymphohematopoiesis may be at least partially under the influence of factors other than those of adult cells.