Outcome of patients with relapsed or progressive Ewing sarcoma enrolled on cooperative group phase 2 clinical trials: A report from the Children's Oncology Group.

SevenChildren's Oncology Group phase 2 trials for patients with relapsed/progressive solid tumors were analyzed to estimate the event-free survival (EFS) for relapsed/progressive Ewing sarcoma. One hundred twenty-eight Ewing sarcoma patients were enrolled and 124 events occurred. The 6-month EFS was 12.7%, demonstrating the poor outcome of these patients. Only docetaxel achieved its protocol-specified radiographic response rate for activity; however, the EFS for docetaxel was similar to other agents, indicating that a higher radiographic response rate may not translate into superior disease control. This EFS benchmark could be utilized as an additional endpoint in trials for recurrent Ewing sarcoma.

Effects of dexrazoxane on doxorubicin-related cardiotoxicity and second malignant neoplasms in children with osteosarcoma: a report from the Children's Oncology Group.

BACKGROUND: Dexrazoxane protects from lower-cumulative-dose doxorubicin cardiotoxicity, but the effect of dexrazoxane in children with sarcoma treated with higher-cumulative-dose doxorubicin is unknown. METHODS: We evaluated children with osteosarcoma (OS) on two Children's Oncology Group trials with higher dose doxorubicin (375-600 mg/m2) preceded by dexrazoxane (10:1 dexrazoxane:doxorubicin dosing). They were evaluated after the minimum expected treatment time (METT), defined as 28 weeks. Cardiotoxicity was identified by echocardiography and serum N-terminal pro-brain natriuretic peptide (NT-proBNP). Second malignant neoplasm (SMN) data was collected. RESULTS: All children had normal left ventricular (LV) systolic function as measured by LV fractional shortening and no heart failure. The end-diastolic septal thickness Z-scores (P < 0.01) and LV mass Z-scores (P < 0.01) were significantly smaller than normal for body-surface area in both sexes. The average LV mass Z-scores were significantly smaller for girls (P < 0.01) and marginally smaller for boys (P = 0.06). Girls had significantly smaller LV end-diastolic dimension Z-scores normalized to BSA (P < 0.01) compared to healthy controls and had significant increases in NT-proBNP. Four children developed SMNs as first events, a rate similar to historical controls. CONCLUSIONS: Dexrazoxane prevented LV dysfunction and heart failure in children with OS receiving higher dose doxorubicin. However, LV structural changes were not fully prevented, especially in girls. As a result, hearts become abnormally small for body size, resulting in higher LV stress. Dexrazoxane did not increase the risk of SMN. Dexrazoxane should be used in this population, particularly for girls, to mitigate anthracycline-induced cardiotoxicity. TRIAL REGISTRATIONS: ClinicalTrials.gov: NCT00003937 (P9754) registered 1 Nov 1999, and NCT00023998 (AOST0121) registered 13 Sept 2001.

Effect of Lecture Attendance and Prerequisite Academic Outcomes on Dental Students' Oral Pathology Performance.

Decreased lecture attendance in undergraduate and health science professions education has been noted throughout the world. The limited study of the effect of lecture attendance on dental students' performance has yielded mixed results, with some studies finding a positive effect and others reporting no association. The aim of this study was to evaluate the effect of lecture attendance on dental students' final grades in an oral pathology course at one U.S. dental school. Due to a curriculum change, second- and third-year students (N=233) were concurrently enrolled in the spring 2016 oral pathology (OP) course. Students' course grades were compared to attendance percentage (Att), grades in prerequisite basic science (PBS) courses, and Academic Average and Total Science (TS) scores on the Dental Admission Test. The results showed that both Att (p=0.011) and TS score (p<0.001) were significant predictors of OP grade, while race, gender, and age were not. Students' grades in OP were moderately to strongly correlated with their grades in all PBS courses (p<0.001). These results suggest that lecture attendance in OP should be encouraged but viewed in light of the finding that it was not as strongly correlated as PBS course performance and was a weaker predictor than TS score. Students with lower TS scores and PBS course grades should be encouraged to use additional supports such as tutoring to improve their performance in OP.

Epidermis and Enamel: Insights Into Gnawing Criticisms of Human Bitemark Evidence.

Critics describe forensic dentists' management of bitemark evidence as junk science with poor sensitivity and specificity and state that linkages to a biter are unfounded. Those vocal critics, supported by certain media, characterize odontologists' previous errors as egregious and petition government agencies to render bitemark evidence inadmissible. Odontologists acknowledge that some practitioners have made past mistakes. However, it does not logically follow that the errors of a few identify a systemic failure of bitemark analysis. Scrutiny of the contentious cases shows that most occurred 20 to 40 years ago. Since then, research has been ongoing and more conservative guidelines, standards, and terminology have been adopted so that past errors are no longer reflective of current safeguards. The authors recommend a comprehensive root analysis of problem cases to be used to determine all the factors that contributed to those previous problems. The legal community also shares responsibility for some of the past erroneous convictions. Currently, most proffered bitemark cases referred to odontologists do not reach courts because those forensic dentists dismiss them as unacceptable or insufficient for analysis. Most bitemark evidence cases have been properly managed by odontologists. Bitemark evidence and testimony remain relevant and have made significant contributions in the justice system.

Local Control Modality and Outcome for Ewing Sarcoma of the Femur: A Report From the Children's Oncology Group.

BACKGROUND: The choice of a local control (LC) modality for Ewing sarcoma (EWS) of the femur is controversial. This study aimed to determine the effect of LC modality on tumor LC and patient outcomes. METHODS: The study reviewed the treatment and outcomes for 115 patients who had EWS of the femur treated with similar chemotherapy in three cooperative group trials. Patient outcomes were analyzed according to the LC modality using the log-rank test and the cumulative incidence of local or distant failure using competing risks regression. RESULTS: The median age of the patients was 13 years. The most common tumor location was the proximal femur followed by the mid femur. For 55 patients with available data, the tumor was larger than 8 cm in 29 patients and 8 cm or smaller in 26 patients. For 84 patients (73 %), surgery only was performed, whereas 17 patients (15 %) had surgery plus radiation, and 14 patients (12 %) had radiation only. The 5-year event-free survival (EFS) rate was 65 % (95 % confidence interval [CI], 55-73 %), and the 5-year overall survival (OS) rate was 70 % (95 % CI, 61-78 %). Patient outcomes did not differ significantly according to tumor location within the femur (proximal, mid or distal) or tumor size (<8 vs ≥8 cm). The findings showed no statistically significant differences in EFS, OS, cumulative incidence of local failure, or cumulative incidence of distant failure according to LC modality (surgery, surgery plus radiation, or radiation). CONCLUSIONS: The LC modality did not significantly affect disease outcome for EWS of the femur. Further study of treatment complications and functional outcome may help to define the optimal LC modality.

Assessment of extent of surgical resection of primary high-grade osteosarcoma by treating institutions: A report from the Children's Oncology Group.

BACKGROUND: Complete surgical resection of primary tumors is critical for long-term control of high-grade osteosarcoma. Uniform assessment of the extent of surgical resection is important in clinical trials, though the accuracy of this reporting has been poorly studied. METHODS: We conducted a retrospective cohort study of patients 5-40 years of age with newly diagnosed high-grade resectable osteosarcoma treated as part of the AOST0331 clinical trial at Children's Oncology Group institutions. The extent of surgical resection of the primary tumor was graded as wide or radical by the treating institution. Central assessment of the extent of resection by two orthopedic oncologists was compared with institutional assessment by reviewing pathology and operative reports. RESULTS: We included 956 patients who had data available for central review. The extent of resection reported by treating institutions was 536/956 (56%) radical and 420/956 (44%) wide. The extent of resection assessed by central review was 162/956 (17%) radical and 794/956 (83%) wide. The overall discordance rate for the cohort was 43%. CONCLUSIONS: Institutional reports of radical resection in high-grade osteosarcoma significantly over-estimate the proportion of patients undergoing radical resection. This highlights the need for centralized review and improved accuracy of reporting of the extent of resection. J. Surg. Oncol. 2016;113:351-354. © 2016 Wiley Periodicals, Inc.

Intensified Chemotherapy With Dexrazoxane Cardioprotection in Newly Diagnosed Nonmetastatic Osteosarcoma: A Report From the Children's Oncology Group.

BACKGROUND: Although chemotherapy has improved outcome of osteosarcoma, 30-40% of patients succumb to this disease. Survivors experience substantial morbidity and mortality from anthracycline-induced cardiotoxicity. We hypothesized that the cardioprotectant dexrazoxane would (i) support escalation of the cumulative doxorubicin dose (600 mg/m(2)) and (ii) not interfere with the cytotoxicity of chemotherapy measured by necrosis grading in comparison to historical control data. PROCEDURE: Children and adolescents with nonmetastatic osteosarcoma were treated with MAP (methotrexate, doxorubicin, cisplatin) or MAPI (MAP/ifosfamide). Dexrazoxane was administered with all doxorubicin doses. Cardioprotection was assessed by measuring left ventricular fractional shortening. Interference with chemotherapy-induced cytotoxicity was determined by measuring tumor necrosis after induction chemotherapy. Feasibility of intensifying therapy with either high cumulative-dose doxorubicin or high-dose ifosfamide/etoposide was evaluated for "standard responders" (SR, <98% tumor necrosis at definitive surgery). RESULTS: Dexrazoxane did not compromise response to induction chemotherapy. With doxorubicin (450-600 mg/m(2)) and dexrazoxane, grade 1 or 2 left ventricular dysfunction occurred in five patients; 4/5 had transient effects. Left ventricular fractional shortening z-scores (FSZ) showed minimal reductions (0.0170 ± 0.009/week) over 78 weeks. Two patients (<1%) had secondary leukemia, one as a first event, a similar rate to what has been observed in prior trials. Intensification with high-dose ifosfamide/etoposide was also feasible. CONCLUSIONS: Dexrazoxane cardioprotection was safely administered. It did not impair tumor response or increase the risk of secondary malignancy. Dexrazoxane allowed for therapeutic intensification increasing the cumulative doxorubicin dose in SR to induction chemotherapy. These findings support the use of dexrazoxane in children and adolescents with osteosarcoma.

Ewing Sarcoma: Current Management and Future Approaches Through Collaboration.

Ewing sarcoma (ES) is an aggressive sarcoma of bone and soft tissue occurring at any age with a peak incidence in adolescents and young adults. The treatment of ES relies on a multidisciplinary approach, coupling risk-adapted intensive neoadjuvant and adjuvant chemotherapies with surgery and/or radiotherapy for control of the primary site and possible metastatic disease. The optimization of ES multimodality therapeutic strategies has resulted from the efforts of several national and international groups in Europe and North America and from cooperation between pediatric and medical oncologists. Successive first-line trials addressed the efficacy of various cyclic combinations of drugs incorporating doxorubicin, vincristine, cyclophosphamide, ifosfamide, etoposide, and dactinomycin and identified prognostic factors now used to tailor therapies. The role of high-dose chemotherapy is still debated. Current 5-year overall survival for patients with localized disease is 65% to 75%. Patients with metastases have a 5-year overall survival < 30%, except for those with isolated pulmonary metastasis (approximately 50%). Patients with recurrence have a dismal prognosis. The many insights into the biology of the EWS-FLI1 protein in the initiation and progression of ES remain to be translated into novel therapeutic strategies. Current options and future approaches will be discussed.

Treatment of relapsed precursor-B acute lymphoblastic leukemia with intensive chemotherapy: POG (Pediatric Oncology Group) study 9411 (SIMAL 9).

Pediatric patients who experience a bone marrow relapse of precursor-B acute lymphoblastic leukemia are cured <50% of the time. This study was designed to determine if intensification of therapies with known activity in this disease would improve the cure rates for patients with relapsed acute lymphoblastic leukemia. Patients were treated with intensive asparaginase during induction followed by repeated cycles of ifosfamide/etoposide and cytarabine/idarubicin. Patients with well-matched related donors were encouraged to undergo hematopoietic stem cell transplant as consolidation. The results of this study demonstrate no significant difference in disease-free survival in patients who received chemotherapy alone (45%) or chemotherapy followed by allogeneic stem cell transplant (50%). Furthermore, results from this study show no significant difference in event-free survival (39.9%±6.2%) or overall survival (41.6%±6.1%) at 8 years when compared with previous studies using less intensive regimens. Our results suggest that alternative therapies are needed to improve cure rates for pediatric patients with relapsed leukemia.

Recurrent gingival fibrous lesions: comparison of 2 cases and potential need for additional classification.

Historically, the classification of localized gingival fibrous lesions has been inconsistent, leading to multiple naming schemes and confusion among pathologists. Currently, lesions are broadly grouped into localized hyperplastic lesions and true neoplasms. Although some cases are clearly defined histologically (i.e., peripheral ossifying fibroma, peripheral odontogenic fibroma), another set of "reactive" fibrous lesions exhibit overlapping histologic features including nondistinctive fibrosis and inflammation. This group can exhibit recurrence, classically related to a local stimulus. However, when local factors are absent, recurrence suggests inherent neoplastic potential. Herein, we describe 2 recurrent fibrous gingival masses, one of which reportedly recurred 3 times with no obvious inciting agent. The histologic appearance of both lesions was similarly distinctive but not well classifiable, while the immunohistochemical profile indicated divergent lesions. This highlights the need for further study of recurrent gingival fibrous lesions to better predict independent growth potential.

A pilot study of low-dose anti-angiogenic chemotherapy in combination with standard multiagent chemotherapy for patients with newly diagnosed metastatic Ewing sarcoma family of tumors: A Children's Oncology Group (COG) Phase II study NCT00061893.

BACKGROUND: The aims of this study were to determine the feasibility of the combination of low dose, anti-angiogenic chemotherapy with standard therapy for patients with metastatic Ewing sarcoma (ES), and to obtain preliminary outcome data. PROCEDURES: Patients with metastatic ES were eligible. Therapy consisted of alternating cycles of ifosfamide-etoposide, and vincristine, doxorubicin, cyclophosphamide. Vinblastine and celecoxib were concomitantly administered. Surgical, radiotherapeutic, or combination local control therapy was given per institutional preference. RESULTS: Thirty-five eligible patients were enrolled. Ninety percent received at least 75% of planned vinblastine/celecoxib doses. There was no excess of neurologic, infectious, hemorrhagic, or cardiovascular toxicities. However, 7 of 21 patients who received pulmonary irradiation prior to experiencing pulmonary toxicity did develop grade 2 or greater pulmonary toxicity, including two deaths of apparent radiation pneumonitis. Fourteen of 16 patients with pelvic disease received local irradiation. Hemorrhagic cystitis developed in six patients, five of whom had received pelvic irradiation. The overall 24-month event free survival was 35% (19-51%); 71% (26-92%) for the seven with isolated pulmonary metastases, 26% (10-45%) for all others. CONCLUSION: The combination of vinblastine/celecoxib metronomic therapy with standard ES treatment was feasible according to the protocol definitions. However, excess toxicity in irradiated areas was noted and limits the usefulness of this protocol. The 24-month EFS for those with isolated pulmonary metastases is better than historical controls, although the number of patient number is small, follow up short and we are lacking contemporaneous controls.

Targeted therapy in pediatric and adolescent oncology.

Cancers in children and adolescents are fortunately infrequent. Overall, cure rates are good, approximately 80%, although this varies by histology and stage. Targeted therapies aim to improve efficacy and decrease toxicity by more specifically affecting malignant cells or their supporting stroma. Cancers of early life are often of different histology than those seen in adults. Sometimes, the same pathway is affected, even if the histology is different. Toxicities may also be different, particularly in younger children. These factors render drug development in young people challenging. This article reviews some successes and challenges to that development, including brief discussions of imatinib, lestaurtinib, antiangiogenesis, and anti-GD2 therapies.

Higher dose imatinib for children with de novo chronic phase chronic myelogenous leukemia: a report from the Children's Oncology Group.

PURPOSE: To determine the efficacy of imatinib in children with newly diagnosed chronic phase (CP) chronic myelogenous leukemia (CML). METHODS: This was an open label, multi-center phase II clinical trial. Courses were defined as consecutive 28-day intervals. Oral imatinib was administered daily at 340 mg/m² without interruption in the absence of toxicity. RESULTS: Fifty-one children received 978 28-day courses of imatinib. The most common toxicities encountered were hematologic. Forty-one patients (80%) achieved a complete hematologic response by the end of course 2. Nineteen children (38%) obtained a complete cytogenetic response (CCyR) at the end of course 3. Overall, 72% achieved CCyR at a median time of 5.6 months. The rate of complete molecular response (>3 log reduction) was 27%. Progression-free and overall survival at 3 years were 72% ± 6.4% and 92% ± 3.9%, respectively. CONCLUSIONS: Daily oral imatinib at a dose of 340 mg/m² is well tolerated in children. In addition, imatinib therapy is effective in inducing a high percent of hematologic, cytogenetic and molecular responses, comparable to adults with CML. (This study was registered at ClinicalTrials.gov under identifier NCT00030394.).

Pharmacotherapy of neuroblastoma.

IMPORTANCE OF THE FIELD: Neuroblastoma, a tumor of the sympathetic nervous system, is the most common extracranial solid tumor of early life. High risk disease in older children remains a therapeutic challenge, despite high-intensity therapy with correspondingly significant short- and long-term toxicities. AREAS COVERED IN THIS REVIEW: We have reviewed therapy for neuroblastoma over the last three decades. This includes cytotoxic chemotherapy, immunotherapy, radionuclides, antiangiogenic compounds, and molecularly targeted agents. We provide a perspective on the incorporation of these drugs into therapy for neuroblastoma. WHAT THE READER WILL GAIN: The reader will gain a better understanding of these novel agents and their targets in neuroblastoma. The reader will also gain insight into the need to define through sequential, carefully designed clinical trials, the roles and toxicities of these therapies, especially if the combination of targeted and conventional cytotoxic agents is used. TAKE HOME MESSAGE: Advanced-stage neuroblastoma in older infants and children remains a disease that is difficult to cure. New, targeted agents may improve both the therapeutic index and the outcome, but are, for the most part, in early development and present a challenge for clinical trial design given both the rarity of this disease and its responsiveness (albeit incomplete) to currently used cytotoxic agents.

Dog bite-related fatalities: a 15-year review of Kentucky medical examiner cases.

A human dog bite-related fatality generally refers to death proximately caused by trauma from a dog's teeth and jaws. According to The Humane Society of the United States, more than 300 individuals died of dog attacks in the United States between 1979 and 1996. Children <12 and elders >70 years represent the typical victims. Pit bull-type dogs, Rottweilers, and German Shepherds constitute the majority of canines implicated in these fatalities.This is a 15-year (1991-2005) retrospective review of dog bite-related fatalities undergoing medicolegal investigation in Kentucky. Of the 11 deaths, 10 consisted of multiple bite marks and blunt force injuries of the head and neck, trunk, and extremities. In 1 case, an asplenic victim's immediate cause of death was bacterial sepsis secondary to a dog bite. Individuals ranged between 14 months and 87 years; 7 (63.6%) were < or =6 years; 10 (90.9%) individuals were white, and 8 (72.7%) were male. Forensic odontological examinations were performed on the dogs in 4 cases. The requisite multidisciplinary investigation includes a detailed assessment of the scene, the victim, and dog or dogs suspected in the attack.

Inhibition of cytidine deaminase by zebularine enhances the antineoplastic action of 5-aza-2'-deoxycytidine.

Cytidine (CR) deaminase is a key enzyme in the catabolism of cytosine nucleoside analogues, since their deamination results in a loss of their pharmacological activity. In this report we have investigated the importance of CR deaminase with respect to the antineoplastic action of inhibitors of DNA methylation, 5-aza-2'-deoxycytidine (5-AZA-CdR) and zebularine. Zebularine has a dual mechanism of action, since it can also inhibit CR deaminase. The objective of our study was to investigate the importance of zebularine as an inhibitor of CR deaminase with respect to the antineoplastic action of 5-AZA-CdR. Using an in vitro clonogenic assay, we investigated the antineoplastic action of 5-AZA-CdR and zebularine, alone and in combination on wild type 3T3 murine fibroblasts and corresponding V5 cells transduced with CR deaminase gene to express a very high level of CR deaminase activity. The V5 cells were much less sensitive to 5-AZA-CdR than the wild type 3T3 cells. The addition of zebularine significantly enhanced the antineoplastic action of 5-AZA-CdR on V5 cells, but not 3T3 cells. Enzymatic analysis on CR deaminase purified from the V5 cells showed that zebularine is a competitive inhibitor of the deamination of 5-AZA-CdR. These in vitro observations are in accord with our in vivo study in mice with L1210 leukemia, which showed that zebularine increased the antileukemic activity of 5-AZA-CdR. Pharmacokinetic analysis also showed that zebularine increased the plasma level of 5-AZA-CdR during an i.v. infusion in mice. Our results indicate that the major mechanism by which zebularine enhances the antineoplastic action of 5-AZA-CdR is by inhibition of CR deaminase. These findings provide a rationale to investigate 5-AZA-CdR in combination with zebularine in patients with advanced leukemia.

Preclinical evaluation of the antineoplastic action of 5-aza-2'-deoxycytidine and different histone deacetylase inhibitors on human Ewing's sarcoma cells.

BACKGROUND: Most patients with advanced Ewing's sarcoma (EWS) respond poorly to conventional chemotherapy, indicating the need for new treatment approaches. Epigenetic events, such as promoter hypermethylation and chromatin histone deacetylation, silence the expression of tumor suppressor genes (TSGs) and play an important role in tumorigenesis. These epigenetic changes can be reversed by using 5-aza-2'-deoxycytidine (5AZA-CdR), a potent inhibitor of DNA methylation, in combination with an inhibitor of histone deacetylase (HDAC). RESULTS: Here, we used a clonogenic assay to evaluate the in vitro antineoplastic activity of 5AZA-CdR in combination with different HDAC inhibitors on EWS cells. We observed that the HDAC inhibitors, MS-275, trichostatin-A, phenylbutyrate, LAQ824 and depsipeptide, enhanced the antineoplastic action of 5AZA-CdR on EWS cells. The combination of 5AZA-CdR and MS-275 showed marked synergy, and was correlated with significant reactivation of the expression of two TSGs, E-cadherin and tumor suppressor lung cancer-1 (TSLC1), in a EWS cell line. CONCLUSION: These results suggest the value of future clinical studies investigating the combination of 5AZA-CdR and MS-275 in patients with advanced EWS.

Prognostic factors for patients with Ewing sarcoma (EWS) at first recurrence following multi-modality therapy: A report from the Children's Oncology Group.

BACKGROUND: The prognosis for patients with recurrent Ewing sarcoma (EWS) is very poor with 5-year survival of 13%. METHODS: To evaluate prognostic factors for these patients we studied patients initially treated on the multi-institutional study INT0091. RESULTS: Two hundred sixty-two patients experienced disease recurrence. The median time to first recurrence was 1.3 years (0-7.4 years), 1.4 years (0-7.4 years) for patients with initially localized disease and 1 year (0-6 years) for patients with initially metastatic disease. Time to first recurrence from date of initial diagnosis was a predictor of post-recurrence survival (P < 0.0001). Twenty-one percent of patients, with recurrent or progressive disease >or=2 years from initial diagnosis, had an estimated 5-year survival of 30% (vs. 7% estimated 5-year survival with an earlier recurrence). No statistical difference was detected between patients whose disease recurred <1 year and between 1 and 2 years from initial diagnosis. A stepwise relative risk model and backwards stepwise regression was used to explore factors significantly associated with risk for post-recurrence death. Significant risk factors for death after recurrence included recurrence at combined local and distant sites, elevated LDH at initial diagnosis and initial recurrence less than 2 years after diagnosis. Isolated pulmonary recurrence was not predictive of survival after recurrence. CONCLUSION: Patients with a longer disease control interval represent the subset of patients most likely to survive following recurrence of EWS. All patients with recurrence would benefit from collaborative trials to investigate new therapeutic options.

Importance of dose-schedule of 5-aza-2'-deoxycytidine for epigenetic therapy of cancer.

BACKGROUND: The inactivation of tumor suppressor genes (TSGs) by aberrant DNA methylation plays an important role in the development of malignancy. Since this epigenetic change is reversible, it is a potential target for chemotherapeutic intervention using an inhibitor of DNA methylation, such as 5-aza-2'-deoxycytidine (DAC). Although clinical studies show that DAC has activity against hematological malignancies, the optimal dose-schedule of this epigenetic agent still needs to be established. METHODS: Clonogenic assays were performed on leukemic and tumor cell lines to evaluate the in vitro antineoplastic activity of DAC. The reactivation of TSGs and inhibition of DNA methylation by DAC were investigated by reverse transcriptase-PCR and Line-1 assays. The in vivo antineoplastic activity of DAC administered as an i.v. infusion was evaluated in mice with murine L1210 leukemia by measurement of survival time, and in mice bearing murine EMT6 mammary tumor by excision of tumor after chemotherapy for an in vitro clonogenic assay. RESULTS: Increasing the DAC concentration and duration of exposure produced a greater loss of clonogenicity for both human leukemic and tumor cell lines. The reactivation of the TSGs (p57KIP2 in HL-60 leukemic cells and p16CDKN2A in Calu-6 lung carcinoma cells) and the inhibition of global DNA methylation in HL-60 leukemic cells increased with DAC concentration. In mice with L1210 leukemia and in mice bearing EMT6 tumors, the antineoplastic action of DAC also increased with the dose. The plasma level of DAC that produced a very potent antineoplastic effect in mice with leukemia or solid tumors was > 200 ng/ml (> 1 microM). CONCLUSION: We have shown that intensification of the DAC dose markedly increased its antineoplastic activity in mouse models of cancer. Our data also show that there is a good correlation between the concentrations of DAC that reduce in vitro clonogenicity, reactivate TSGs and inhibit DNA methylation. These results suggest that the antineoplastic action of DAC is related to its epigenetic action. Our observations provide a strong rationale to perform clinical trials using dose intensification of DAC to maximize the chemotherapeutic potential of this epigenetic agent in patients with cancer.