Prevalence and Subtype Distribution of High-Risk Human Papillomavirus Among Women Presenting for Cervical Cancer Screening at Karanda Mission Hospital

PURPOSE

High-risk human papillomaviruses (hrHPV) are the primary cause of cervical cancer. Human papillomavirus (HPV) vaccination is expected to prevent cervical cancers caused by the HPV types included in vaccines and possibly by cross-protection from other types. This study sought to determine the hrHPV type distribution in women at a rural Zimbabwe hospital.

METHODS

We implemented a cross-sectional study at the Karanda Mission Hospital. Using the Visual Inspection with Acetic Acid Cervicography technique, clinicians collected cervical swabs from 400 women presenting for screening for cervical cancer. Samples were initially analyzed by Cepheid GeneXpert; candidate hrHPV genotypes were further characterized using the Anyplex II HPV28 Detection Kit.

RESULTS

Twenty-one percent of the 400 women were positive for a high-risk genotype when using the GeneXpert analyzer; 17% were positive when using the multiplex analysis. Almost two thirds of the hrHPV women had a single DNA type identified, whereas one third had multiple genotypes, ranging from 2 to 5. hrHPV was observed more frequently in HIV-positive than in HIV-negative women (27% v 15%). Of the 113 isolates obtained, 77% were hrHPV genotypes not included in the bivalent or quadrivalent vaccines, and 47% represented DNA types not covered in the nonavalent vaccine. Forty-seven percent of the women with hrHPV harbored a single genotype that was not covered by the nonavalent vaccine.

CONCLUSION

A large fraction of hrHPV isolates from women participating in a cervical cancer screening program in northern Zimbabwe are DNA types not covered by the bivalent, quadrivalent, or nonavalent vaccines. These findings suggest the importance of characterizing the hrHPV DNA types isolated from cervical neoplasia in this population and determining whether cross-immunization against these genotypes develops after administration of the vaccines in current use.

All Men Are Created Equal: Addressing Disparities in Prostate Cancer Care

The global cancer burden is estimated to have risen to 18.1 million new cases and 9.6 million deaths in 2018. By 2030, the number of cancer cases is projected to increase to 24.6 million and the number of cancer deaths, to 13 million. Global data mask the social and health disparities that influence cancer incidence and survival. Inequality in exposure to carcinogens, education, access to quality diagnostic services, and affordable treatments all affect the probability of survival. Worryingly, despite the fact that many cancers could be prevented by stronger public health actions and many others could be largely cured by better access to diagnostics and affordable treatments, the international community has yet to make a substantial move to tackle this challenge. In prostate cancer, studies show that there are geographic and racial/ethnic distribution differences as well as a number of other variables, including environmental factors, limited access to standard cancer treatments, reduced probability to be included in trials, and the financial burden of cancer treatments. Financial burden for the patients can result in poor adherence, increased debt, and poor long-term outcomes. The following article will discuss some of the important causes for disparity in prostate cancer and prostate cancer care, focused on the current situation in the United States, as well as possible remedies to address these causes.

Comparative Assessment of Clinical Benefit Using the ESMO-Magnitude of Clinical Benefit Scale Version 1.1 and the ASCO Value Framework Net Health Benefit Score

PURPOSE

To better understand the European Society for Medical Oncology-Magnitude of Clinical Benefit Scale version 1.1 (ESMO-MCBS v1.1) and the ASCO Value Framework Net Health Benefit score version 2 (ASCO-NHB v2), ESMO and ASCO collaborated to evaluate the concordance between the frameworks when used to assess clinical benefit attributable to new therapies.

METHODS

The 102 randomized controlled trials in the noncurative setting already evaluated in the field testing of ESMO-MCBS v1.1 were scored using ASCO-NHB v2 by its developers. Measures of agreement between the frameworks were calculated and receiver operating characteristic curves used to define thresholds for the ASCO-NHB v2 corresponding to ESMO-MCBS v1.1 categories. Studies with discordant scoring were identified and evaluated to understand the reasons for discordance.

RESULTS

The correlation of the 102 pairs of scores for studies in the noncurative setting is estimated to be 0.68 (Spearman's rank correlation coefficient; overall survival, 0.71; progression-free survival, 0.67). Receiver operating characteristic curves identified thresholds for ASCO-NHB v2 for facilitating comparisons with ESMO-MCBS v1.1 categories. After applying pragmatic threshold scores of 40 or less (ASCO-NHB v2) and 2 or less (ESMO-MCBS v1.1) for low benefit and 45 or greater (ASCO-NHB v2) and 4 to 5 (ESMO-MCBS v1.1) for substantial benefit, 37 discordant studies were identified. Major factors that contributed to discordance were different approaches to evaluation of relative and absolute gain for overall survival and progression-free survival, crediting tail of the curve gains, and assessing toxicity.

CONCLUSION

The agreement between the frameworks was higher than observed in other studies that sought to compare them. The factors that contributed to discordant scores suggest potential approaches to improve convergence between the scales.

American Society of Clinical Oncology's Global Oncology Leadership Task Force: Findings and Actions

In response to rising cancer incidence and mortality rates in low- and middle-income countries and the increasingly global profile of ASCO’s membership, the ASCO Board of Directors appointed the Global Oncology Leadership Task Force (Task Force) to provide recommendations on ASCO’s engagement in global oncology. To accomplish its work, the Task Force convened meetings of global oncology experts, conducted focus group discussions with member groups, did site visits to South America and India, and met regularly to analyze the findings and develop recommendations. Task Force findings included global concerns, such as access to care, and specific concerns of middle- and low-resource settings. The need to strengthen health systems and the importance of alliances with a range of international cancer stakeholders were emphasized. Task Force recommendations to the ASCO Board of Directors were based on a three-part global oncology strategy of professional development, improvement of access to quality care, and acceleration of global oncology research. Specific areas of focus within each of these strategic pillars are provided along with an update on areas of ASCO activity as these recommendations are implemented.

New Frameworks to Assess Value of Cancer Care: Strengths and Limitations

Confronted with the different clinical impacts of different treatments, the rising cost of cancer care, and the financial burden of high drug prices, several influential professional organizations have developed models with which to assess the clinical benefit and value of cancer treatment regimens. The goal is a system of valuing patient therapies that is aligned with the beneficial impact to the patient and society and that moves away from a fixed cost regardless of clinical circumstances.

Quality Oncology Practice Initiative: An Approach to Solving the Value Equation

There must be recruitment of a majority of the oncology practices (community, hospital based, and academic based) into the QOPI initiative, and payers must be encouraged to develop incentives for physicians who deliver high-quality oncology care.

The rising cost of cancer care: physicians take charge

The author comments on the ASCO Top Five, a list of five commonly utilized practices in each oncology specialty for which there is no evidence to support their use.

ASCO Task Force on the Cost of Cancer Care

The United States leads the world in cancer care outcomes, but the cost is extremely high-and growing rapidly. New proposals for health reform emphasize one clear and immediate need: to control runaway cost.

Value and cancer care: toward an equitable future

Health care expenses in the United States are increasing inexorably. At the current rate of growth, it is anticipated that 20% of the gross national product will consist of health-related expenditures within the next decade. Cancer is the second leading cause of death in the United States, and it is increasing in prevalence because of the aging of the population and the limited number of successful prevention strategies. As the biological characteristics of cancer come into sharper focus, targeted therapies are being developed that offer the promise of increased clinical benefit with fewer toxicities than are associated with conventional treatment. Although spectacular successes are infrequent with this approach, to date, the majority of targeted therapies are modestly effective at best, and extremely costly. This observation suggests that a broadly acceptable definition of value in a cancer therapeutic agent is not at hand, but is sorely needed from the vantage points of the patient and society. A corollary issue of enormous import is how to equitably distribute the health care dollar in the service of achieving the greatest good for the greatest number. Although cancer is responsible for only 5% of the health care budget, its cost is increasing and it can be viewed as paradigmatic when contemplating the problem of equity in health care. Here, a number of concepts are discussed that focus on this goal and its implications for the cancer patient and society at large.

American society of clinical oncology statement: toward individualized care for patients with advanced cancer

Patients with advanced incurable cancer face complex physical, psychological, social, and spiritual consequences of disease and its treatment. Care for these patients should include an individualized assessment of the patient's needs, goals, and preferences throughout the course of illness. Consideration of disease-directed therapy, symptom management, and attention to quality of life are important aspects of quality cancer care. However, emerging evidence suggests that, too often, realistic conversations about prognosis, the potential benefits and limitations of disease-directed therapy, and the potential role of palliative care, either in conjunction with or as an alternative to disease-directed therapy, occur late in the course of illness or not at all. This article addresses the American Society of Clinical Oncology's (ASCO's) vision for improved communication with and decision making for patients with advanced cancer. This statement advocates an individualized approach to discussing and providing disease-directed and supportive care options for patients with advanced cancer throughout the continuum of care. Building on ASCO's prior statements on end-of-life care (1998) and palliative care (2009), this article reviews the evidence for improved patient care in advanced cancer when patients' individual goals and preferences for care are discussed. It outlines the goals for individualized care, barriers that currently limit realization of this vision, and possible strategies to overcome these barriers that can improve care consistent with the goals of our patients and evidence-based medical practice.

American Society of Clinical Oncology Guidance Statement: The Cost of Cancer Care

Advances in early detection, prevention, and treatment have resulted in consistently falling cancer death rates in the United States. In parallel with these advances have come significant increases in the cost of cancer care. It is well established that the cost of health care (including cancer care) in the United States is growing more rapidly than the overall economy. In part, this is a result of the prices and rapid uptake of new agents and other technologies, including advances in imaging and therapeutic radiology. Conventional understanding suggests that high prices may reflect the costs and risks associated with the development, production, and marketing of new drugs and technologies, many of which are valued highly by physicians, patients, and payers. The increasing cost of cancer care impacts many stakeholders who play a role in a complex health care system. Our patients are the most vulnerable because they often experience uneven insurance coverage, leading to financial strain or even ruin. Other key groups include pharmaceutical manufacturers that pass along research, development, and marketing costs to the consumer; providers of cancer care who dispense increasingly expensive drugs and technologies; and the insurance industry, which ultimately passes costs to consumers. Increasingly, the economic burden of health care in general, and high-quality cancer care in particular, will be less and less affordable for an increasing number of Americans unless steps are taken to curb current trends. The American Society of Clinical Oncology (ASCO) is committed to improving cancer prevention, diagnosis, and treatment and eliminating disparities in cancer care through support of evidence-based and cost-effective practices. To address this goal, ASCO established a Cost of Care Task Force, which has developed this Guidance Statement on the Cost of Cancer Care. This Guidance Statement provides a concise overview of the economic issues facing stakeholders in the cancer community. It also recommends that the following steps be taken to address immediate needs: recognition that patient-physician discussions regarding the cost of care are an important component of high-quality care; the design of educational and support tools for oncology providers to promote effective communication about costs with patients; and the development of resources to help educate patients about the high cost of cancer care to help guide their decision making regarding treatment options. Looking to the future, this Guidance Statement also recommends that ASCO develop policy positions to address the underlying factors contributing to the increased cost of cancer care. Doing so will require a clear understanding of the factors that drive these costs, as well as potential modifications to the current cancer care system to ensure that all Americans have access to high-quality, cost-effective care.

Familial gastrointestinal stromal tumor syndrome: phenotypic and molecular features in a kindred

PURPOSE

Members of a family with hereditary gastrointestinal stromal tumors (GISTs) and a germline KIT oncogene mutation were evaluated for other potential syndrome manifestations. A tumor from the proband was analyzed to compare features with sporadic GISTs.

PATIENTS AND METHODS

Members of a kindred in which six relatives in four consecutive generations comprised an autosomal dominant pattern of documented GISTs and cutaneous lesions underwent physical examination, imaging studies, and germline KIT analysis. A recurrent GIST from the proband was studied using microarray, karyotypic, immunohistochemical, and immunoblotting techniques.

RESULTS

In addition to evidence of multiple GISTs, lentigines, malignant melanoma, and an angioleiomyoma were identified in relatives. A previously reported gain-of-function missense mutation in KIT exon 11 (T --> C) that results in a V559A substitution within the juxtamembrane domain was identified in three family members. The proband's recurrent gastric GIST had a 44,XY-14,-22 karyotype and immunohistochemical evidence of strong diffuse cytoplasmic KIT expression without expression of actin, desmin, or S-100. Immunoblotting showed strong expression of phosphorylated KIT and downstream signaling intermediates (AKT and MAPK) at levels comparable with those reported in sporadic GISTs. cDNA array profiling demonstrated clustering with sporadic GISTs, and expression of GIST markers comparable to sporadic GISTs.

CONCLUSION

These studies provide the first evidence that gene expression and mechanisms of cytogenetic progression and cell signaling are indistinguishable in familial and sporadic GISTs. Current investigations of molecularly targeted therapies in GIST patients provide opportunities to increase the understanding of features of the hereditary syndrome, and risk factors and molecular pathways of the neoplastic phenotypes.

Extreme lymphoplasmacytosis and hepatic failure associated with sulfasalazine hypersensitivity reaction and a concurrent EBV infection?case report and review of the literature

We present an unusual case of a patient with extreme lymphoplasmacytosis and hepatic failure in association with a reaction to sulfasalazine and a concurrent Epstein-Barr virus (EBV) infection. Sulfa drugs can cause a wide range of allergic and hypersensitivity reactions and occasionally can lead to a fulminant illness. In the case under discussion the patient had hepatotoxicity, skin rash, fever, and peripheral blood atypical lymphocytosis. Initial impressions suggested the possibility of a malignant lymphoproliferative disorder. Flow cytometry of peripheral blood and a bone marrow biopsy provided clear evidence for a reactive, polyclonal process as opposed to a malignant disorder. Cessation of the offending drug and administration of steroids led to dramatic improvement. This case illustrates that drug hypersensitivity reactions can be manifested by an extreme lymphocytoid leukemoid reaction.

The costs of conducting clinical research

PURPOSE

Physicians frequently receive payment for enrolling subjects onto clinical trials. Some view these payments as conflicts of interest. Others contend that these payments are necessary reimbursements for conducting clinical research. We evaluated the clinical and nonclinical hours and costs associated with conducting a mock phase III clinical research trial.

METHODS

We collected data from representatives of 21 clinical sites, on the numbers of hours associated with 13 activities necessary to the conduct of clinical research. The hours were based on enrolling 20 patients in a 12-month randomized placebo-controlled trial of a new chemotherapeutic agent. The outcome measures were disease progression and quality-of-life reports. These costs were evaluated for both government and pharmaceutical industry-sponsored trials.

RESULTS

On average, 4,012 hours (range, 1,512 to 13,319 hours) were required for a government-sponsored trial, and 3,998 hours (range: 1735 to 15,699) were required for a pharmaceutical industry-sponsored trial involving 20 subjects with 17 office visits, or approximately 200 hours per subject. Thirty-two percent of the hours were devoted to nonclinical activities, such as institutional review board submission and completion of clinical reporting forms. On average, excluding overhead expenses, it cost slightly more than 6,094 dollars (range, 2,098 dollars to 19,285 dollars) per enrolled subject for an industry-sponsored trial, including 1,999 dollars devoted to nonclinical costs.

CONCLUSION

Based on the results of our mock trial, the time required for nontreatment trial activities is considerable, and the associated costs are substantial.

In vitro and in vivo induction of antiangiogenic activity by plasminogen activators and captopril

BACKGROUND

Many antiangiogenic molecules are proteolytically cleaved from larger plasma proteins. For example, plasminogen activators cleave plasminogen into plasmin, and plasmin is converted into angiostatin in the presence of sulfhydryl donors. We thus investigated whether the antiangiogenic activity in plasma could be increased by treatment with recombinant tissue plasminogen activator (rt-PA) and the sulfhydryl donor captopril.

METHODS

Human plasma was treated with rt-PA (10 micro g/mL) and/or captopril (1 micro M). Angiogenesis was measured in vitro by human endothelial cell tube formation and endothelial cell proliferation and in vivo in mice with the Matrigel plug assay. Angiostatin was removed from treated plasma by affinity chromatography, immunoprecipitation, or ion-exchange chromatography, and the antiangiogenic activity of the depleted plasma was assessed by tube formation. Three cancer patients were treated with rt-PA and captopril, and their pretreatment and post-treatment plasmas were tested for antiangiogenic activity in vitro.

RESULTS

Angiogenesis in vitro was stimulated by untreated plasma and inhibited by plasma that had been treated with rt-PA and captopril but was not affected by treatment with rt-PA and/or captopril alone. In vivo angiogenesis in Matrigel plugs was substantially lower in mice treated with rt-PA and captopril than in untreated control mice. Antiangiogenic activity in treated plasma was largely retained after angiostatin was removed: treated plasma inhibited angiogenesis by 64.3% (95% confidence interval [CI] = 46.4% to 82.2%), relative to untreated plasma, and treated plasma depleted of angiostatin by affinity chromatography or immunoprecipitation inhibited angiogenesis by 65.1% (95% CI = 53.8% to 76.4%) or 63.7% (95% CI = 50.9% to 76.5%), respectively. Antiangiogenic activity of plasma from three cancer patients was higher after treatment with rt-PA and captopril than before such treatment.

CONCLUSION

Treatment with rt-PA and captopril induced antiangiogenic activity in vitro and in vivo that appears to be independent of angiostatin.

Attitudes and practices among pediatric oncologists regarding end-of-life care: results of the 1998 American Society of Clinical Oncology survey

PURPOSE

In 1998, the American Society of Clinical Oncology (ASCO) surveyed its membership to assess the attitudes, practices, and challenges associated with end-of-life care of patients with cancer. In this report, we summarize the responses of pediatric oncologists and the implications for care of children dying from cancer.

METHODS

The survey consisted of 118 questions, covering eight categories. All ASCO members in the United States, Canada, and the United Kingdom were mailed a survey, which was completed by 228 pediatric oncologists. Predictors of particular attitudes and practices were identified using stepwise logistic regression analysis. Potential predictors were age, sex, religious affiliation, importance of religious beliefs, recent death of a relative, specialty, type of practice (rural or urban, academic or nonacademic), amount of time spent in patient care, number of new patients in the past 6 months, and number of patients who died in the past year.

RESULTS

Pediatric oncologists reported a lack of formal courses in pediatric palliative care, a strikingly high reliance on trial and error in learning to care for dying children, and a need for strong role models in this area. The lack of an accessible palliative care team or pain service was often identified as a barrier to good care. Communication difficulties exist between parents and oncologists, especially regarding the shift to end-of-life care and adequate pain control.

CONCLUSION

Pediatric oncologists are working to integrate symptom control, psychosocial support, and palliative care into the routine care of the seriously ill child, although barriers exist that make such comprehensive care a challenge.

SMARCAD1, a novel human helicase family-defining member associated with genetic instability: cloning, expression, and mapping to 4q22-q23, a band rich in breakpoints and deletion mutants involved in several human diseases

Members of the DEAD/H box-containing helicase superfamily include proteins essential to genome replication, repair, and expression. We report here the cloning and initial characterization of a novel human member of this protein family, designated hHel1 (human helicase 1), now designated SMARCAD1 by HUGO. This DEAD/H box-containing molecule has seven highly conserved sequence regions that allow us to place it in the SNF2 family of the helicase superfamily. Uniquely, though, hHel1 contains two DEAD/H box motifs, a property not reported to be shared by any other SNF2 family members. This defines a new subfamily consisting of hHel1 and its homologues. In addition to these DEAD/H box/ATP-binding motifs, hHel1 has a putative nuclear localization signal and several regions that may mediate protein-protein interactions. Expression analysis indicates that hHel1 transcripts are ubiquitous, with particularly high levels in endocrine tissue. We have mapped the gene for hHel1 to human chromosome 4q22-q23; this region is rich in breakpoints and deletion mutants of genes involved in several human diseases, notably soft tissue leiomyosarcoma, hepatocellular carcinoma, and hematologic malignancies. Our observation that human Hel1 gene overexpression is present in an E1A-expressing cell line with increased capacity for gene reactivation events by genomic rearrangement suggests that human Hel1 may play a role in genetic instability development.

Attitudes and practices of U.S. oncologists regarding euthanasia and physician-assisted suicide

BACKGROUND

The practices of euthanasia and physician-assisted suicide remain controversial.

OBJECTIVE

To achieve better understanding of attitudes and practices regarding euthanasia and physician-assisted suicide in the context of end-of-life care.

DESIGN

Cohort study.

SETTING

United States.

PARTICIPANTS

3299 oncologists who are members of the American Society of Clinical Oncology.

MEASUREMENTS

Responses to survey questions on attitudes toward euthanasia and physician-assisted suicide for a terminally ill patient with prostate cancer who has unremitting pain, requests for and performance of euthanasia and physician-assisted suicide, and sociodemographic characteristics.

RESULTS

Of U.S. oncologists surveyed, 22.5% supported the use of physician-assisted suicide for a terminally ill patient with unremitting pain and 6.5% supported euthanasia. Oncologists who were reluctant to increase the dose of intravenous morphine for terminally ill patients in excruciating pain (odds ratio [OR], 0.61 [95% CI, 0.48 to 0.77]) and had sufficient time to talk to dying patients about end-of-life care issues (OR, 0.79 [CI, 0.71 to 0.87]) were less likely to support euthanasia or physician-assisted suicide. During their career, 3.7% of surveyed oncologists had performed euthanasia and 10.8% had performed physician-assisted suicide. Oncologists who were reluctant to increase the morphine dose for patients in excruciating pain (OR, 0.58 [CI, 0.43 to 0.79]) and those who believed that they had received adequate training in end-of-life care (OR, 0.86 [CI, 0.79 to 0.95]) were less likely to have performed euthanasia or physician-assisted suicide. Oncologists who reported not being able to obtain all the care that a dying patient needed were more likely to have performed euthanasia (P = 0.001).

CONCLUSIONS

Requests for euthanasia and physician-assisted suicide are likely to decrease as training in end-of-life care improves and the ability of physicians to provide this care to their patients is enhanced.

Cloning and characterization of the 5'-flanking sequence for the human DNA topoisomerase II beta gene

Mammalian cells express two isoforms of type II DNA topoisomerase which are the intracellular targets of many structurally diverse antineoplastic agents. The levels of topoisomerase II isozymes are important determinants for the sensitivity of cells to the cytotoxicity of drugs that target topoisomerase II. To investigate whether the expression of topoisomerase II isoforms is coordinated and the mechanisms governing their expression in the context of drug resistance, the 5'-flanking sequence for the gene of human topoisomerase IIbeta isoform was cloned and characterized. The 5'-flanking region has a very high GC content and contains no canonical TATA box element. Two separate transcriptional start sites are located to an adenine and a guanine, 193 and 89 nucleotides, respectively, upstream from the ATG translation initiation codon. Except for a small region immediately upstream of the translation initiation codon, there is no obvious sequence homology between the 5'-flanking sequences of human topoisomerase IIbeta gene and the previously described alpha gene. Transient expression assays with different 5'- and 3'-deletions of the 5'-flanking region of the topoisomerase IIbeta gene have delineated regions important for transcriptional regulation of the gene. Interestingly, sequences within the first intron also contribute to the promoter activity. Gel mobility shift studies demonstrate that protein factors from the nuclear extracts can bind specifically to the downstream elements and may participate in transcriptional regulation.

Passage to nonselective media transiently alters growth of mycophenolic acid-resistant mammalian cells expressing the escherichia coli xanthine-guanine phosphoribosyltransferase gene: implications for sequential selection strategies

The Escherichia coli xanthine-guanine phosphoribosyltransferase gene (Ecogpt) rescues mammalian cells from inhibition of purine nucleotide biosynthesis by mycophenolic acid (MPA). We used Ecogpt and other selectable markers to obtain subclones of NIH 3T3 derivatives (EN/NIH) stably expressing transfected genes of interest. In their respective selective mediums, growth of MPA-resistant (MPA(R)) isolates was indistinguishable from that of aminoglycoside-resistant counterparts expressing selectable marker genes conferring resistance to protein synthesis inhibitors hygromycin B, puromycin, and G418. Growth of aminoglycoside-resistant isolates remained unaltered on passage to nonselective media. In contrast, MPA(R) cells transferred from MPA complete media to nonselective media displayed morphologic changes with static growth. These findings resolved completely by third passage in nonselective media and were independent of the gene of interest cis-linked to the selectable marker. Sequential selection strategies involving cell culture conditions resulting in these altered growth characteristics significantly impaired detection (by selection in G418) of genomic events associated with reactivation of enhancerless, transcriptionally silent neointegrants present in MPA(R) EN/NIH isolates. We explored the cause of these cell culture findings and defined transfection and sequential selection strategies for MPA(R) derivatives that successfully circumvented these effects.

DNA topoisomerase II alpha expression is associated with alkylating agent resistance

Increased expression of DNA topoisomerase II alpha has been associated with resistance to certain DNA-damaging alkylating agents, but no causal relationship or mechanism has been established. To investigate this observation, we developed a model of topoisomerase II overexpression by transfecting a full-length Chinese hamster ovary topoisomerase II alpha into EMT6 mouse mammary carcinoma. Topoisomerase II alpha-transfected cell lines demonstrated continued topoisomerase II alpha mRNA and protein expression, which were undetectable in vector-only lines, in stationary phase (G0-G1). The topoisomerase II transfectants were approximately 5-10-fold resistant to the alkylating agents cisplatin and mechlorethamine. Upon release from G0-G1, the topoisomerase II transfectants demonstrated more rapid thymidine incorporation and shorter cell-doubling times than control cells. Purified topoisomerase II and nuclear extracts with topoisomerase II-decatenating activity bound to cisplatin-treated DNA with significantly greater affinity than to untreated DNA in a cisplatin concentration-dependent manner. These observations suggest that expression of topoisomerase II alpha may have a role in cellular resistance to antineoplastic alkylating agents. The mechanism for this may involve increased binding of topoisomerase II alpha to alkylating agent-damaged DNA.

Molecular cloning and characterization of the promoter for the Chinese hamster DNA topoisomerase II alpha gene

To investigate the mechanisms governing the expression of DNA topoisomerase II alpha, the Chinese hamster topoisomerase II alpha gene has been cloned and the promoter region analyzed. There are several transcriptional start sites clustered in a region of 30 base pairs, with the major one being 102 nucleotides upstream from the ATG translation initiation site. Sequencing data reveal one GC box and a total of five inverted CCAAT elements (ICEs) within a region of 530 base pairs upstream from the major transcription start site. Sequence comparison between the human and Chinese hamster topoisomerase II alpha gene promoter regions shows a high degree of homology centered at the ICEs and GC box. In vitro DNase I footprinting results indicate protection by binding proteins at and around each ICE on both DNA strands. However, no obvious protection was observed for the GC box. Competition gel mobility shift assays with oligonucleotides containing either the wild-type or mutated ICE sequences suggest that identical or similar proteins specifically bind at each ICE, although with different affinities for individual ICE sequences. Chloramphenicol acetyltransferase assays employing nested 5'-deletions of the 5'-flanking sequence of the gene demonstrate that the sequence between -186 and +102, which contains three proximal ICEs, is sufficient for near wild-type level of promoter activity. When these three ICEs were gradually replaced with sequences which do not interact with the binding proteins, reducing promoter activity of the resulted constructs was observed. In conjunction with results from footprinting and gel mobility shift studies, the transient gene expression finding suggests that the ICEs are functionally important for the transcriptional regulation of the topoisomerase II alpha gene.

Phase I trial of an interleukin-2 fusion toxin (DAB486IL-2) in hematologic malignancies: complete response in a patient with Hodgkin's disease refractory to chemotherapy

BACKGROUND

DAB486IL-2 is a recombinant fusion toxin in which the native diphtheria toxin-receptor binding-domain has been replaced with human interleukin-2 (IL-2). This molecule is specifically cytotoxic in vitro within 30 minutes for cells that express the high-affinity IL-2 receptor (IL-2R).

METHODS

This was a Phase I/II study of DAB486IL-2 as a brief infusion in 15 patients with refractory lymphoid malignancies. Five patients per cohort received DAB486IL-2 as a 30-60 minute intravenous infusion at dose levels of 0.075, 0.115, and 0.2 mg/kg daily for 5 days.

RESULTS

The maximal tolerated dose (MTD) of DAB486IL-2 was determined to be 0.2 mg/kg daily on the basis of hypersensitivity-like symptoms and reversible hepatic transaminase elevations. Other adverse effects included mild creatinine elevations, proteinuria, and hypoalbuminemia. The presence of antibodies to diphtheria toxin or DAB486IL-2 was correlated with hypersensitivity-like effects but did not prevent an antitumor effect. One complete response was observed in a patient with Hodgkin's disease in relapse with bilateral pulmonary nodules after autologous bone marrow transplantation. He remains free of disease more than 2 years after completion of therapy.

CONCLUSIONS

The dramatic antitumor response seen in one patient and the relative tolerability of DAB486IL-2 indicates the potential utility of this targeted agent in IL-2-expressing hematologic malignancies.

Conditional expression of wild-type topoisomerase II complements a mutant enzyme in mammalian cells

Alterations in the amino acid composition, phosphorylation pattern, or intracellular levels of topoisomerase II have been associated with resistance to antineoplastic agents whose effects are mediated through interactions with this enzyme. To develop a model system with which to investigate the determinants of topoisomerase II sensitivity or resistance to antineoplastic agents that target this enzyme, a cDNA encoding the wild-type Drosophila melanogaster topoisomerase II was ligated into a mammalian expression vector containing a glucocorticoid-inducible mouse mammary tumor virus promoter and transfected into an epipodophyllotoxin-resistant Chinese hamster ovary cell line (VPM(r)-5). In two transfectants carrying an intact, full-length Drosophila topoisomerase II cDNA, exposure to the inducing agent, dexamethasone (10 microM), resulted in complementation of the endogenous mutant topoisomerase II and phenotypic reversion to etoposide sensitivity. In the presence of glucocorticoid, etoposide-induced cytotoxicity increased 20-fold, despite the fact that Drosophila topoisomerase II mRNA expression was only 0.1% of that of the endogenous mammalian topoisomerase II. Induced cells demonstrated a marked increase in DNA single strand breaks compared with uninduced resistant cells, thereby providing biochemical evidence supporting increased DNA strand cleavage due to activation of the Drosophila enzyme. These observations demonstrate the ability of a wild-type Drosophila topoisomerase II to complement a mutant mammalian enzyme and suggest that transfectants capable of conditional topoisomerase II expression represent a useful model for studies of the biochemical pharmacology and structure-function relationships of normal and mutant enzymes.

Molecular cloning and identification of a point mutation in the topoisomerase II cDNA from an etoposide-resistant Chinese hamster ovary cell line

Topoisomerase II (Top II) is the target enzyme for many antineoplastic drugs such as epipodophyllotoxins, anthracyclines, and acridines. Cell lines with alterations in Top II are resistant to drugs that interact with the enzyme. Studies of the Top II from a Chinese hamster ovary line, VpmR-5, that is resistant to VP-16 and VM-26, demonstrated that it is very similar, qualitatively and quantitatively, to its normal counterpart except that DNA cleavage by the VpmR-5 enzyme is not stimulated by VP-16 or VM-26. To understand the basis for the drug-resistant phenotype, the Top II cDNAs were isolated from both Chinese hamster ovary (CHO) and VpmR-5 cells by cDNA cloning with lambda gt22, and the entire cDNAs were sequenced. A mutation of G-->A at nucleotide 1478 was the only alteration observed in the VpmR-5 Top II cDNA compared with the wild-type gene. The mutation in VpmR-5 was confirmed by sequencing DNA fragments amplified from the genomic DNA by the polymerase chain reaction. Southern blot hybridization analysis of genomic DNA demonstrated loss of a Top II allele in VpmR-5 probably occurred during the development of resistance to etoposide. The mutation in VpmR-5 changes amino acid 493 from arginine to glutamine and is located adjacent to a putative ATP binding site of Top II. Mutations in an analogous region have been identified in two human leukemia cell lines by amplification of segments of Top II cDNA with Taq DNA polymerase. Taken together, these observations suggest that mutations in this region of the gyrase B domain of mammalian topoisomerase II may be capable of conferring resistance to antineoplastic agents that interact with this enzyme.

Pulmonary toxicity associated with high dose chemotherapy in the treatment of solid tumors with autologous marrow transplant: an analysis of four chemotherapy regimens

We retrospectively reviewed the pulmonary toxicity of six high dose chemotherapy protocols using four chemotherapy regimens in the treatment of solid tumors. All protocols used either high dose cyclophosphamide or ifosfamide in combination with one to three additional chemotherapeutic agents. In each protocol autologous bone marrow was reinfused post chemotherapy to shorten the period of severe myelosuppression. Of 178 patients there were 20 cases of fatal or life-threatening pulmonary toxicity including nine cases of pneumonia, nine cases of interstitial pneumonitis and two cases of pulmonary hemorrhage. Pulmonary function tests revealed modest changes in FEV1 and DLCO in the majority of patients, although 24 patients had more dramatic changes in DLCO suggesting interstitial damage. Significant decrements in FEV1 were seen in the BCNU containing regimen. Statistically significant or nearly significant decreases in DLCO were seen after all cyclophosphamide containing regimens. A regimen containing ifosfamide, carboplatin, and etoposide had minimal associated pulmonary toxicity.