The neo-open reading frame peptides that comprise the tumor framome are a rich source of neoantigens for cancer immunotherapy

Identification of immunogenic cancer neoantigens as targets for therapy is challenging. Here, we integrate cancer whole genome and long-read transcript sequencing to identify the collection of novel open reading frame peptides (NOPs) expressed in tumors, termed the framome. NOPs represent tumor-specific peptides that are different from wild-type proteins and may be strongly immunogenic. We describe an uncharacterized class of hidden NOPs, which derive from structural genomic variants involving an upstream protein coding gene driving expression and translation of non-coding regions of the genome downstream of a rearrangement breakpoint. NOPs represent a vast amount of possible neoantigens particularly in tumors with many (complex) structural genomic variants and a low number of missense mutations. We show that NOPs are immunogenic and epitopes derived from NOPs can bind to MHC class I molecules. Finally, we provide evidence for the presence of memory T-cells specific for hidden NOPs in lung cancer patient peripheral blood.

Overall survival by IDH2 mutant allele (R140 or R172) in patients with late-stage mutant-IDH2 relapsed or refractory acute myeloid leukemia treated with enasidenib or conventional care regimens in the phase 3 IDHENTIFY trial

7005

Background: IDH2 gene mutations (m IDH2) occur in up to ̃20% of patients (pts) with acute myeloid leukemia (AML), most commonly as R140Q (in ̃75% of cases) or R172K (̃25%) point mutations. The functional effects and prognostic relevance of m IDH2-R140 and m IDH2-R172 can vary (Papaemmanuil 2016). In the randomized, phase 3 IDHENTIFY trial, enasidenib (ENA), an oral mIDH2 inhibitor, did not significantly improve overall survival (OS) vs conventional care regimens (CCR) as salvage treatment (Tx) for older pts with m IDH2 relapsed/refractory (R/R) AML in ITT analysis, but a trend for improved OS with ENA was detected in pts with IDH2-R172 mutations. We further investigated OS and correlative biomarkers in IDHENTIFY pt subgroups defined by m IDH2 variant (R140/R172). Methods: This open-label trial (NCT02577406) enrolled pts ≥ 60 years of age who had received 2 or 3 prior AML Tx. Pts were preselected to a CCR (azacitidine, intermediate- or low-dose Ara-C, or supportive care), and were then randomized 1:1 to ENA 100 mg/d or CCR in 28d cycles. Co-occurring gene mutations were identified by targeted next-generation sequencing (37-gene panel) of bone marrow mononuclear cell (BMMC) DNA. Total 2-HG levels were determined by LC/MS. Results: Of 319 pts enrolled, 88 pts (28%; 43 ENA, 45 CCR) had m IDH2-R172 and 229 (72%; 115 ENA, 114 CCR) had m IDH2-R140. Median baseline (BL) 2-HG levels were similar between Tx arms and m IDH2 variant subgroups, as were IDH2 variant allele frequencies. Pts with m IDH2-R172 had fewer median BL co-mutations (4 [range 2–8]) than did pts with m IDH2-R140 (5 [1–11]) ( P < 0.0001). The most frequently co-occurring mutations were SRSF2 and RUNX1 in the R140 cohort (59% each) and DNMT3A in the R172 cohort (57%). Compared with the R172 cohort, the R140 group was enriched with SRSF2, FLT3 (-ITD/-TKD), NPM1, RUNX1, and JAK2 mutations, whereas DNMT3A and TP53 mutations were more common in the R172 group. In Cox multivariate analysis including m IDH2 variant (R140/R172), DNMT3A mutation status, and number of gene mutations at BL, m IDH2-R172 was significantly ( P = 0.04) correlated with improved OS (vs. R140) in the ENA arm, whereas the number of BL gene mutations was significantly ( P < 0.01) associated with OS in the CCR arm. Median OS in the R172 subgroup was 14.6 mo with ENA vs 7.8 mo with CCR (HR, 0.59 [95%CI 0.35-0.98]; P = 0.039) and 1-yr survival rates were 62% and 30%, respectively. In m IDH2-R140 pts, median OS was 5.7 mo in both Tx arms (0.93 [0.70-1.24]; P = 0.61), and 1-year survival rates were 29% and 25% with ENA and CCR, respectively. Conclusions: Mutational burden and co-mutational profiles differed between pts with m IDH2-R140 and m IDH2-R172 R/R AML. ENA improved survival outcomes for pts with IDH2-R172 mutations, with median OS and 1-year survival rate approximately double those in the CCR arm. Clinical trial information: NCT02577406.

Characteristics and outcome of adult patients with acute promyelocytic leukemia and increased body mass index treated with the PETHEMA Protocols

OBJECTIVE

The obesity/overweight may have an influence on APL outcomes.

METHODS

This is the biggest multicentre analysis on 1320 APL patients treated with AIDA-induction and risk-adapted consolidation between 1996 and 2012. Patients body mass index (BMI) was classified as underweight (<18.5 kg/m² ), normal (18.5-25 kg/m² ), overweight (25-29.9 kg/m² ), and obese (≥30 kg/m² ) according to the World Health Organization (WHO) criteria.

RESULTS AND CONCLUSIONS

Relationship between male gender, older age, and other known laboratory abnormalities in overweight/obese patients was significant. The induction mortality rate was significantly higher in APL with BMI ≥25 vs BMI <25 (10% vs 6%; P = .04). APL patients with BMI ≥25 had a trend to lower OS (74% vs 80%; P = .06). However, in the multivariate analysis, BMI did not retain the independent predictive value (P = .46). There was no higher incidence of differentiation syndrome with BMI ≥25, but there was a trend in obese. There was no difference in relapse rate according to the BMI. In summary, overweight/obesity does not represent an independent risk factor for APL outcomes. The influence of obesity in APL patients treated with chemotherapy-free regimens remains to be established.

Clinical significance of complex karyotype at diagnosis in pediatric and adult patients with de novo acute promyelocytic leukemia treated with ATRA and chemotherapy

Although additional cytogenetic abnormalities (ACA) do not affect the prognosis of patients with t(15;17) acute promyelocytic leukemia (APL), the role of a complex karyotype (CK) is yet to be clarified. We aimed to investigate the relationship of CK with relapse incidence in 1559 consecutive APL patients enrolled in three consecutive trials. Treatment consisted of AIDA induction followed by risk-adapted consolidation. A CK (CK) was defined as the presence of ≥2 ACA, and a very CK (CK+) as ≥3 ACA. Eighty-nine patients (8%) had a CK, of whom 41 (4%) had CK+. The 5-year cumulative incidence of relapse (CIR) in patients with CK was 18%, and 12% in those with <2 ACA (p=.09). Among patients with CK+, the 5-year CIR was 27% vs 12% (p=.003), retaining the statistical significance in multivariate analysis. This study shows an increased risk of relapse among APL patients with CK + treated with ATRA plus chemotherapy front-line regimens.

An analysis of the impact of CD56 expression in de novo acute promyelocytic leukemia patients treated with upfront all-trans retinoic acid and anthracycline-based regimens

Out of 956, there were 95 (10%) CD56+ APL patients treated with PETHEMA ATRA and chemotherapy. CD56+ expression was associated with high WBC, BCR3 isoform, and co-expression of CD2, CD34, CD7, HLA-DR, CD15, and CD117 antigens. CD56+ vs CD56- APL presented higher induction death rate (16% vs 8%, p = .02) and 5-years cumulative incidence of relapse (33% versus 10%, p = .006), irrespectively of the Sanz score (low-risk 47% versus 5%, p < .001; intermediate 23% versus 7%, p < .001; and high-risk 42% versus 21%, p = .007). In the multivariate analysis, CD56 + (p < .0001), higher relapse-risk score (p = .001), and male gender (p = .05) retained the independent predictive value. CD56+ APL also showed a greater risk of CNS relapse (6% versus 1%, p < .001) and lower 5-year OS (75% versus 83%, p = .003). The AIDA-based LPA2012 trial, with an intensified consolidation schedule for CD56+ APL, will elucidate whether an intensified consolidation schedule could mitigate the relapse rate in this setting.

Graft-Versus-Leukemia Effect of Allogeneic Stem-Cell Transplantation and Minimal Residual Disease in Patients With Acute Myeloid Leukemia in First Complete Remission

Purpose

The detection of minimal residual disease (MRD) in patients with acute myeloid leukemia (AML) may improve future risk-adapted treatment strategies. We assessed whether MRD-positive and MRD-negative patients with AML benefit differently from the graft-versus-leukemia effect of allogeneic hematopoietic stem-cell transplantation (alloHSCT).

Methods

A total of 1,511 patients were treated in subsequent Dutch-Belgian Hemato-Oncology Cooperative Group and the Swiss Group for Clinical Cancer Research AML trials, of whom 547 obtained a first complete remission, received postremission treatment (PRT), and had available flow cytometric MRD before PRT. MRD positivity was defined as more than 0.1% cells with a leukemia-associated immunophenotype within the WBC compartment. PRT consisted of alloHSCT (n = 282), conventional PRT by a third cycle of chemotherapy (n = 160), or autologous hematopoietic stem-cell transplantation (n = 105).

Results

MRD was positive in 129 patients (24%) after induction chemotherapy before proceeding to PRT. Overall survival and relapse-free survival were significantly better in patients without MRD before PRT compared with MRD-positive patients (65% ± 2% v 50% ± 5% at 4 years; P = .002; and 58% ± 3% v 38% ± 4%; P < .001, respectively), which was mainly because of a lower cumulative incidence of relapse (32% ± 2% compared with 54% ± 4%; P < .001, respectively). Multivariable analysis with adjustment for covariables showed that the incidence of relapse was significantly reduced after alloHSCT compared with chemotherapy or autologous hematopoietic stem cell transplantation (hazard ratio [HR], 0.36; P < .001), which was similarly exerted in both MRD-negative and MRD-positive patients (HR, 0.38; P < .001; and HR, 0.35; P < .001, respectively).

Conclusion

The graft-versus-leukemia effect of alloHSCT is equally present in MRD-positive and MRD-negative patients, which advocates a personalized application of alloHSCT, taking into account the risk of relapse determined by AML risk group and MRD status, as well as the counterbalancing risk of nonrelapse mortality.

A phase I first-in-human study with tefinostat - a monocyte/macrophage targeted histone deacetylase inhibitor - in patients with advanced haematological malignancies

Tefinostat (CHR-2845) is a monocyte/macrophage targeted histone deacetylase inhibitor (HDACi). This first-in-human, standard 3 + 3 dose escalating trial of oral, once daily tefinostat was conducted to determine the safety, tolerability, pharmacokinetic and pharmacodynamic profile of tefinostat in relapsed/refractory haematological diseases. Eighteen patients were enrolled at doses of 20-640 mg. Plasma concentrations of tefinostat exceeded those demonstrated to give in vitro anti-proliferative activity. Flow cytometric pharmacodynamic assays demonstrated monocyte-targeted increases in protein acetylation, without corresponding changes in lymphocytes. Dose-limiting toxicities (DLTs) were not observed and dose escalation was halted at 640 mg without identification of the maximum tolerated dose. Drug-related toxicities were largely Common Toxicity Criteria for Adverse Events grade 1/2 and included nausea, anorexia, fatigue, constipation, rash and increased blood creatinine. A patient with chronic monomyelocytic leukaemia achieved a bone marrow response, with no change in peripheral monocytes. An acute myeloid leukaemia type M2 patient showed a >50% decrease in bone marrow blasts and clearance of peripheral blasts. In conclusion, tefinostat produces monocyte-targeted HDACi activity and is well tolerated, without the DLTs, e.g. fatigue, diarrhoea, thrombocytopenia, commonly seen with non-targeted HDACi. The early signs of efficacy and absence of significant toxicity warrant further evaluation of tefinostat in larger studies. (clinicaltrials.gov identifier: NCT00820508).

Identification of a 24-gene prognostic signature that improves the European LeukemiaNet risk classification of acute myeloid leukemia: an international collaborative study

PURPOSE

To identify a robust prognostic gene expression signature as an independent predictor of survival of patients with acute myeloid leukemia (AML) and use it to improve established risk classification.

PATIENTS AND METHODS

Four independent sets totaling 499 patients with AML carrying various cytogenetic and molecular abnormalities were used as training sets. Two independent patient sets composed of 825 patients were used as validation sets. Notably, patients from different sets were treated with different protocols, and their gene expression profiles were derived using different microarray platforms. Cox regression and Kaplan-Meier methods were used for survival analyses.

RESULTS

A prognostic signature composed of 24 genes was derived from a meta-analysis of Cox regression values of each gene across the four training sets. In multivariable models, a higher sum value of the 24-gene signature was an independent predictor of shorter overall (OS) and event-free survival (EFS) in both training and validation sets (P < .01). Moreover, this signature could substantially improve the European LeukemiaNet (ELN) risk classification of AML, and patients in three new risk groups classified by the integrated risk classification showed significantly (P < .001) distinct OS and EFS.

CONCLUSION

Despite different treatment protocols applied to patients and use of different microarray platforms for expression profiling, a common prognostic gene signature was identified as an independent predictor of survival of patients with AML. The integrated risk classification incorporating this gene signature provides a better framework for risk stratification and outcome prediction than the ELN classification.

The impact of medical education and networking on the outcome of leukemia treatment in developing countries. The experience of International Consortium on Acute Promyelocytic Leukemia (IC-APL)

OBJECTIVES

Several clinical trials conducted in Europe and US reported favorable outcomes of patients with APL treated with the combination of all trans retinoic acid (ATRA) and anthracyclines. Nevertheless, the results observed in developing countries with the same regimen was poorer, mainly due to high early mortality mainly due bleeding. The International Consortium on Acute Promyelocytic Leukemia (IC-APL) is an initiative of the International Members Committee of the ASH and the project aims to reduce this gap through the establishment of international network, which was launched in Brazil, Mexico and Uruguay.

METHODS

The IC-APL treatment protocol is similar to the PETHEMA 2005, but changing idarubicin to daunorubicin. All patients with a suspected diagnosis of APL were immediately started on ATRA, while bone marrow samples were shipped to a national central lab where genetic verification of the diagnosis was performed. The immunofluorescence using an anti-PML antibody allowed a rapid confirmation of the diagnosis and, the importance of supportive measures was reinforced.

RESULTS

The interim analysis of 97 patients enrolled in the IC-APL protocol showed that complete remission (CR) rate was 83% and the 2-year overall survival and disease-free survival were 80% and 90%, respectively. Of note, the early mortality rate was reduced to 7.5%.

DISCUSSION

The results of IC-APL demonstrate the impact of educational programs and networking on the improvement of the leukemia treatment outcome in developing countries.

miR-196b directly targets both HOXA9/MEIS1 oncogenes and FAS tumour suppressor in MLL-rearranged leukaemia

HOXA9 and MEIS1 have essential oncogenic roles in mixed lineage leukaemia (MLL)-rearranged leukaemia. Here we show that they are direct targets of miRNA-196b, a microRNA (miRNA) located adjacent to and co-expressed with HOXA9, in MLL-rearranged leukaemic cells. Forced expression of miR-196b significantly delays MLL-fusion-mediated leukemogenesis in primary bone marrow transplantation through suppressing Hoxa9/Meis1 expression. However, ectopic expression of miR-196b results in more aggressive leukaemic phenotypes and causes much faster leukemogenesis in secondary transplantation than MLL fusion alone, likely through the further repression of Fas expression, a proapoptotic gene downregulated in MLL-rearranged leukaemia. Overexpression of FAS significantly inhibits leukemogenesis and reverses miR-196b-mediated phenotypes. Targeting Hoxa9/Meis1 and Fas by miR-196b is probably also important for normal haematopoiesis. Thus, our results uncover a previously unappreciated miRNA-regulation mechanism by which a single miRNA may target both oncogenes and tumour suppressors, simultaneously, or, sequentially, in tumourigenesis and normal development per cell differentiation, indicating that miRNA regulation is much more complex than previously thought.

Prognostic value of FLT3 mutations in patients with acute promyelocytic leukemia treated with all-trans retinoic acid and anthracycline monochemotherapy

BACKGROUND

Fms-like tyrosine kinase-3 (FLT3) gene mutations are frequent in acute promyelocytic leukemia but their prognostic value is not well established.

DESIGN AND METHODS

We evaluated FLT3-internal tandem duplication and FLT3-D835 mutations in patients treated with all-trans retinoic acid and anthracycline-based chemotherapy enrolled in two subsequent trials of the Programa de Estudio y Tratamiento de las Hemopatías Malignas (PETHEMA) and Hemato-Oncologie voor Volwassenen Nederland (HOVON) groups between 1996 and 2005.

RESULTS

FLT3-internal tandem duplication and FLT3-D835 mutation status was available for 306 (41%) and 213 (29%) patients, respectively. Sixty-eight (22%) and 20 (9%) patients had internal tandem duplication and D835 mutations, respectively. Internal tandem duplication was correlated with higher white blood cell and blast counts, lactate dehydrogenase, relapse-risk score, fever, hemorrhage, coagulopathy, BCR3 isoform, M3 variant subtype, and expression of CD2, CD34, human leukocyte antigen-DR, and CD11b surface antigens. The FLT3-D835 mutation was not significantly associated with any clinical or biological characteristic. Univariate analysis showed higher relapse and lower survival rates in patients with a FLT3-internal tandem duplication, while no impact was observed in relation to FLT3-D835. The prognostic value of the FLT3-internal tandem duplication was not retained in the multivariate analysis.

CONCLUSIONS

FLT3-internal tandem duplication mutations are associated with several hematologic features in acute promyelocytic leukemia, in particular with high white blood cell counts, but we were unable to demonstrate an independent prognostic value in patients with acute promyelocytic leukemia treated with all-trans retinoic acid and anthracycline-based regimens.

Evidence for acute neurotoxicity after chemotherapy

OBJECTIVE

Chronic neurotoxicity is a recognized long-term complication following chemotherapy in a range of diseases. Neurotoxicity adversely affects patients' quality of life. The objective of this study is to examine whether there is evidence of acute neurotoxicity.

METHODS

This prospective study included patients with secondary progressive multiple sclerosis (SPMS-BMT, n = 14) and hematological malignancies (HM-BMT, n = 17) receiving chemotherapy as preconditioning for bone marrow transplant. The control groups included SPMS patients matched for demographic and clinical data (SPMS-PL, n = 14) and healthy controls (n = 14). Neurodegeneration was assessed at baseline and longitudinally (months 1, 2, 3, 6, 9, 12, 24, and 36), combining a clinical scale for disability (Expanded Disability Status Scale [EDSS]), a serum protein biomarker for neurodegeneration (neurofilaments, NfH-SMI35), and brain atrophy measures (magnetic resonance imaging).

RESULTS

Disability progression was significantly more acute and severe following chemotherapy compared to placebo. Immediately after starting chemotherapy, serum NfH-SMI35 levels increased in 79% (p < 0.0001) of SPMS-BMT patients and 41% (p < 0.01) of HM-BMT patients compared to 0% of SPMS-PL patients or healthy controls. In SPMS-BMT serum NfH-SMI35 levels were > 100-fold higher 1 month after chemotherapy (29.73ng/ml) compared to baseline (0.28ng/ml, p < 0.0001). High serum NfH-SMI35 levels persisting for at least 3 months were associated with sustained disability progression on the EDSS (p < 0.05). Brain atrophy rates increased acutely in SPMS-BMT (-2.09) compared to SPMS-PL (-1.18, p < 0.05).

INTERPRETATION

Neurotoxicity is an unwanted acute side effect of aggressive chemotherapy.

Additional chromosome abnormalities in patients with acute promyelocytic leukemia treated with all-trans retinoic acid and chemotherapy

BACKGROUND

Acute promyelocytic leukemia is a subtype of acute myeloid leukemia characterized by the t(15;17). The incidence and prognostic significance of additional chromosomal abnormalities in acute promyelocytic leukemia is still a controversial matter.

DESIGN AND METHODS

Based on cytogenetic data available for 495 patients with acute promyelocytic leukemia enrolled in two consecutive PETHEMA trials (LPA96 and LPA99), we analyzed the incidence, characteristics, and outcome of patients with acute promyelocytic leukemia with and without additional chromosomal abnormalities who had been treated with all-trans retinoic acid plus anthracycline monochemotherapy for induction and consolidation.

RESULTS

Additional chromosomal abnormalities were observed in 140 patients (28%). Trisomy 8 was the most frequent abnormality (36%), followed by abn(7q) (5%). Patients with additional chromosomal abnormalities more frequently had coagulopathy (P=0.03), lower platelet counts (P=0.02), and higher relapse-risk scores (P=0.02) than their counterparts without additional abnormalities. No significant association with FLT3/ITD or other clinicopathological characteristics was demonstrated. Patients with and without additional chromosomal abnormalities had similar complete remission rates (90% and 91%, respectively). Univariate analysis showed that additional chromosomal abnormalities were associated with a lower relapse-free survival in the LPA99 trial (P=0.04), but not in the LPA96 trial. However, neither additional chromosomal abnormalities overall nor any specific abnormality was identified as an independent risk factor for relapse in multivariate analysis.

CONCLUSIONS

The lack of independent prognostic value of additional chromosomal abnormalities in acute promyelocytic leukemia does not support the use of alternative therapeutic strategies when such abnormalities are found.

Central nervous system involvement at first relapse in patients with acute promyelocytic leukemia treated with all-trans retinoic acid and anthracycline monochemotherapy without intrathecal prophylaxis

BACKGROUND

The prevalence of and risk factors for central nervous system recurrence in patients with acute promyelocytic leukemia are not well established and remain a controversial matter.

DESIGN AND METHODS

Between 1996 and 2005, 739 patients with newly diagnosed acute promyelocytic leukemia enrolled in two consecutive trials (PETHEMA LPA96 and LPA99) received induction therapy with all-trans retinoic acid and idarubicin. Consolidation therapy comprised three courses of anthracycline monochemotherapy (LPA96), with all-trans retinoic acid and reinforced doses of idarubicin in patients with an intermediate or high risk of relapse (LPA99). Central nervous system prophylaxis was not given.

RESULTS

Central nervous system relapse was documented in 11 patients. The 5-year cumulative incidence of central nervous system relapse was 1.7% (LPA96 3.2% and LPA99 1.2%; p=0.09). The cumulative incidence was 0%, 0.8%, and 5.5% in low-, intermediate-, and high-risk patients, respectively. Relapse risk score (p=0.0001) and the occurrence of central nervous system hemorrhage during induction (5-year cumulative incidence 18.7%, p=0.006) were independent risk factors for central nervous system relapse.

CONCLUSIONS

This study shows a low incidence of central nervous system relapse in patients with acute promyelocytic leukemia following therapy with all-trans retinoic acid and anthracycline without specific central nervous system prophylaxis. Central nervous system relapse was significantly associated with high white blood cell counts and prior central nervous system hemorrhage, which emerged as independent prognostic factors.

Age-specific differences in oncogenic pathway deregulation and chemosensitivity in patients with acute myeloid leukemia: Strategies to maximize response to induction chemotherapy

7013

Background: Despite all the advances made in understanding the poor prognosis of acute myeloid leukemia (AML) in the elderly, the underlying biology at a molecular signaling pathway level has yet to be defined. Methods: Clinically annotated, microarray data from 425 patients with newly diagnosed AML from two publicly available datasets GSE1159 and GSE12417 were analyzed. Age-specific cohorts (young ≤45 years; n = 175 and elderly ≥55 years; n = 144) were prospectively identified. Gene expression analysis was conducted by applying previously defined and tested signature profiles reflecting deregulation of oncogenic signaling pathways, altered tumor environment, and signatures of chemotherapy sensitivity. Standard Kaplan-Meier survival curves were generated using the two-sided log-rank test and individual differences in the probability of oncogenic pathway deregulation between young vs. elderly were analyzed via the non-parametric Mann-Whitney U test and a one-sided p-value ≤ 0.05 was considered statistically significant. Results: Elderly AML patients had worse OS (median 8.8 months vs. 24.1 months in younger patients; p = 0.001) and EFS (median 7.1 months vs. 15.3 months in younger patients; p < 0.0001). Analysis of oncogenic pathways revealed that older patients had higher probability of Ras, Src, and TNF pathway activation, p < 0.0001. Older patients were also less sensitive to anthracycline compared to younger AML patients, p < 0.0001. Unsupervised hierarchical clustering of younger AML patients revealed two clusters and clinically better survival for cluster 1 compared to cluster 2 (high Ras, Src, TNF pathway activation) and the latter were in turn less sensitive to adriamycin. However, in elderly patients those in cluster 2 also had high Ras, Src, TNF but this did not translate into differences in survival or chemotherapy sensitivity. Conclusions: AML arising in the elderly represents a distinct biologic entity characterized by unique patterns of deregulated signaling pathways that contributes to poor survival and resistance to adriamycin. We hope these findings will enable clinically meaningful adjustments of treatment strategies in the older patient population.

No significant financial relationships to disclose.

A phase 2 study of the oral farnesyltransferase inhibitor tipifarnib in patients with refractory or relapsed acute myeloid leukemia

This phase 2 study evaluated the efficacy and safety of the oral farnesyltransferase inhibitor tipifarnib in adults with refractory or relapsed acute myeloid leukemia (AML). Patients (n=252) received tipifarnib 600 mg twice a day for 21 days in 28-day cycles. Median age was 62 years; 99 (39%) patients were 65 years or older. Eleven (4%) of 252 patients achieved complete remission (CR) or complete remission with incomplete platelet recovery (CRp; 9 CR and 2 CRp). Nineteen patients (8%), including those who achieved CR/CRp, achieved a reduction in bone marrow blasts to less than 5% blasts. Bone marrow blasts were reduced more than 50% in an additional 8 patients (total = 27; 11%). Median survival was 369 days for patients who achieved CR/CRp. Myelosuppression was the most common adverse event. The most common nonhematologic toxicities were fever, nausea, and hypokalemia. Single-agent treatment with tipifarnib induced durable CR/CRp, which was associated with prolonged survival, in some patients with refractory or relapsed AML. The response rate observed in this heavily pretreated group of patients suggests the requirement to enhance the response rate either by combining tipifarnib with other active agents or determining factors that are predictive of response.

Results of a HOVON/SAKK donor versus no-donor analysis of myeloablative HLA-identical sibling stem cell transplantation in first remission acute myeloid leukemia in young and middle-aged adults: benefits for whom?

The Dutch-Belgian Hemato-Oncology Cooperative Group and the Swiss Group for Clinical Cancer Research (HOVON-SAKK) collaborative study group evaluated outcome of patients (pts) with acute myeloid leukemia (AML) in first remission (CR1) entered in 3 consecutive studies according to a donor versus no-donor comparison. Between 1987 and 2004, 2287 pts were entered in these studies of whom 1032 pts (45%) without FAB M3 or t(15;17) were in CR1 after 2 cycles of chemotherapy, received consolidation treatment, and were younger than 55 years of age and therefore eligible for allogeneic hematopoietic stem cell transplantation (allo-SCT). An HLA-identical sibling donor was available for 326 pts (32%), whereas 599 pts (58%) lacked such a donor, and information was not available in 107 pts. Compliance with allo-SCT was 82% (268 of 326). Cumulative incidences of relapse were, respectively, 32% versus 59% for pts with versus those without a donor (P < .001). Despite more treatment-related mortality (TRM) in the donor group (21% versus 4%, P < .001), disease-free survival (DFS) appeared significantly better in the donor group (48% +/- 3% versus 37% +/- 2% in the no-donor group, P < .001). Following risk-group analysis, DFS was significantly better for pts with a donor and an intermediate- (P = .01) or poor-risk profile (P = .003) and also better in pts younger than 40 years of age (P < .001). We evaluated our results and those of the previous MRC, BGMT, and EORTC studies in a meta-analysis, which revealed a significant benefit of 12% in overall survival (OS) by donor availability for all patients with AML in CR1 without a favorable cytogenetic profile.

Clinical application and proposal for modification of the International Working Group (IWG) response criteria in myelodysplasia

The myelodysplastic syndromes (MDSs) are heterogeneous with respect to clinical characteristics, pathologic features, and cytogenetic abnormalities. This heterogeneity is a challenge for evaluating response to treatment. Therapeutic trials in MDS have used various criteria to assess results, making cross-study comparisons problematic. In 2000, an International Working Group (IWG) proposed standardized response criteria for evaluating clinically significant responses in MDS. These criteria included measures of alteration in the natural history of disease, hematologic improvement, cytogenetic response, and improvement in health-related quality of life. The relevance of the response criteria has now been validated prospectively in MDS clinical trials, and they have gained acceptance in research studies and in clinical practice. Because limitations of the IWG criteria have surfaced, based on practical and reported experience, some modifications were warranted. In this report, we present recommendations for revisions of some of the initial criteria.

The effect of oligonucleotide microarray data pre-processing on the analysis of patient-cohort studies

Background

Intensity values measured by Affymetrix microarrays have to be both normalized, to be able to compare different microarrays by removing non-biological variation, and summarized, generating the final probe set expression values. Various pre-processing techniques, such as dChip, GCRMA, RMA and MAS have been developed for this purpose. This study assesses the effect of applying different pre-processing methods on the results of analyses of large Affymetrix datasets. By focusing on practical applications of microarray-based research, this study provides insight into the relevance of pre-processing procedures to biology-oriented researchers.

Results

Using two publicly available datasets, i.e., gene-expression data of 285 patients with Acute Myeloid Leukemia (AML, Affymetrix HG-U133A GeneChip) and 42 samples of tumor tissue of the embryonal central nervous system (CNS, Affymetrix HuGeneFL GeneChip), we tested the effect of the four pre-processing strategies mentioned above, on (1) expression level measurements, (2) detection of differential expression, (3) cluster analysis and (4) classification of samples. In most cases, the effect of pre-processing is relatively small compared to other choices made in an analysis for the AML dataset, but has a more profound effect on the outcome of the CNS dataset. Analyses on individual probe sets, such as testing for differential expression, are affected most; supervised, multivariate analyses such as classification are far less sensitive to pre-processing.

Conclusion

Using two experimental datasets, we show that the choice of pre-processing method is of relatively minor influence on the final analysis outcome of large microarray studies whereas it can have important effects on the results of a smaller study. The data source (platform, tissue homogeneity, RNA quality) is potentially of bigger importance than the choice of pre-processing method.

AML1-ETO fusion protein up-regulates TRKA mRNA expression in human CD34+ cells, allowing nerve growth factor-induced expansion

The AML1-ETO fusion protein, generated by the t(8;21) in acute myeloid leukemia (AML), exerts dominant-negative functions and a variety of gains of function, including a positive effect on the growth of primary human CD34+ hematopoietic stem/progenitor cells. We now show that AML1-ETO expression up-regulates the level of TRKA mRNA and protein in these cells and that AML1-ETO-expressing CD34+ hematopoietic cells grown in the presence of five early-acting hematopoietic cytokines further proliferate in response to nerve growth factor (NGF). These cells also show a unique response to NGF and IL-3; namely, they expand in liquid culture. To determine the biological relevance of our findings, we analyzed 262 primary AML patient samples using real-time RT-PCR and found that t(8;21)-positive AML samples express significantly higher levels of TRKA mRNA than other subtypes of AML. NGF, which is normally expressed by bone marrow stromal cells, could provide important proliferative or survival signals to AML1-ETO-expressing leukemic or preleukemic cells, and the NGF/TRKA signaling pathway may be a suitable target for therapeutic approaches to AML.

Impaired recovery of Epstein-Barr virus (EBV)--specific CD8+ T lymphocytes after partially T-depleted allogeneic stem cell transplantation may identify patients at very high risk for progressive EBV reactivation and lymphoproliferative disease

Epstein-Barr virus (EBV)-specific cytotoxic T lymphocytes are considered pivotal to prevent lymphoproliferative disease (LPD) in allogeneic stem cell transplantation (SCT) recipients. We evaluated the recovery of EBV-specific CD8+ T cells after partially T-cell-depleted SCT and studied the interaction between EBV-specific CD8+ T cells, EBV reactivation, and EBV-LPD. EBV-specific CD8+ T cells were enumerated using 12 class I HLA tetramers presenting peptides derived from 7 EBV proteins. Blood samples were taken at regular intervals after SCT in 61 patients, and EBV DNA levels were assessed by real-time polymerase chain reaction. Forty-five patients showed EBV reactivation, including 25 with high-level reactivation (ie, more than 1000 genome equivalents [geq] per milliliter). Nine of these 25 patients progressed to EBV-LPD. CD8+ T cells specific for latent or lytic EBV epitopes repopulated the peripheral blood at largely similar rates. In most patients, EBV-specific CD8+ T-cell counts had returned to normal levels within 6 months after SCT. Concurrently, the incidence of EBV reactivations clearly decreased. Patients with insufficient EBV-specific CD8+ T-cell recovery were at high risk for EBV reactivation in the first 6 months after SCT. Failure to detect EBV-specific CD8+ T cells in patients with high-level reactivation was associated with the subsequent development of EBV-LPD (P =.048). Consequently, the earlier defined positive predictive value of approximately 40%, based on high-level EBV reactivation only, increased to 100% in patients without detectable EBV-specific CD8+ T cells. Thus, impaired recovery of EBV-specific CD8+ T cells in patients with high-level EBV reactivation may identify a subgroup at very high risk for EBV-LPD and supports that EBV-specific CD8+ T cells protect SCT recipients from progressive EBV reactivation and EBV-LPD.

The peripheral cannabinoid receptor Cb2, a novel oncoprotein, induces a reversible block in neutrophilic differentiation

We previously identified a novel common virus integration site, Evi11, by means of retroviral insertional mutagenesis. We demonstrated that the gene encoding the peripheral cannabinoid receptor (Cb2) is the potential target, suggesting that Cb2 is a proto-oncogene. To elucidate a role for this G protein-coupled receptor (GPCR) in leukemic transformation we generated a Cb2-EGFP cDNA construct that was introduced into 32D/G-CSF-R cells. These cells require interleukin 3 (IL-3) to proliferate in vitro, whereas in the presence of granulocyte-colony-stimulating factor (G-CSF) they differentiate toward mature neutrophils. We demonstrate that 32D/G-CSF-R/Cb2-EGFP cells migrate in a transwell assay in reponse to the Cb2 ligand 2-arachidonoylglycerol (2-AG), indicating that the fusion protein was functional. When cultured in the presence of G-CSF neutrophilic differentiation of Cb2-EGFP-expressing 32D/G-CSF-R cells was completely blocked. Moreover, a Cb2-specific antagonist fully recovered the G-CSF-induced neutrophilic differentiation of 32D/G-CSF-R/Cb2-EGFP cells. To investigate which signal transduction pathway(s) may be involved in the block of neutrophilic maturation, differentiation experiments were carried out using specific inhibitors of signaling routes. Interestingly, full rescue of G-CSF-induced neutrophilic differentiation was observed when cells were cultured with the mitogen-induced extracellular kinase (MEK) inhibitors, PD98059 or U0126, and partial recovery was detected with the phosphoinositide 3-kinase (PI3-K) inhibitor LY-294002. These studies demonstrate that the Cb2 receptor is an oncoprotein that blocks neutrophilic differentiation when overexpressed in myeloid precursor cells. Cb2 appears to mediate its activity through MEK/extracellular signal-related kinase (ERK) and PI3-K pathways.

Cyclosporin A combined with vincristine, doxorubicin and dexamethasone (VAD) compared with VAD alone in patients with advanced refractory multiple myeloma: an EORTC-HOVON randomized phase III study (06914)

Patients with multiple myeloma (MM) refractory to alkylating agents frequently express P-glycoprotein (Pgp), which is associated with the multidrug resistance (MDR) phenotype. We have conducted a randomized phase II/III study of the MDR reversal agent cyclosporin A combined with VAD (vincristine, doxorubicin, dexamethasone) compared with standard VAD in patients with MM stage IIA/IIIA who were refractory to or progressive after treatment with alkylating agents. Out of 81 patients who were randomized, 75 were eligible and evaluable: 34 in the VAD + cyclosporin A arm versus 41 in the VAD arm. Toxicities of grade 2-3 were observed more often with VAD + cyclosporin A than with VAD only: nausea (30% versus 8%, P = 0.015), mucositis (18% versus 5%, P = 0.13), infection (45% versus 35%, P = 0.50). The treatment results were similar in the two arms: 53% versus 49% responded [95% CI (-18.5%, 26.9%)]. The median progression-free survival (PFS) was 8.6 months (VAD + cyclosporin A) versus 5.8 months (VAD): [log rank P = 0.16, hazard ratio = 0.71, 95% CI (0.44, 1.15)], and median overall survival was 13 months versus 14.6 months [log rank P = 0.89, hazard ratio = 0.96, 95% CI (0.62, 1.72)]. The cause of death was progressive disease (85%), toxicity (10%) or other (5%). Bone marrow analysis performed in 23 patients showed that the response rate was 67% in Pgp-positive versus 55% in Pgp-negative patients. Cyclosporin A combined with VAD is relatively well tolerated. There is no effect of cyclosporin A on the overall response rate, PFS and overall survival with VAD.

Liposomal amphotericin B compared with amphotericin B deoxycholate in the treatment of documented and suspected neutropenia-associated invasive fungal infections

It has been suggested that a better outcome of neutropenia-associated invasive fungal infections can be achieved when high doses of lipid formulations of amphotericin B are used. We now report a randomized multicentre study comparing liposomal amphotericin B (AmBisome, 5 mg/kg/d) to amphotericin B deoxycholate (AmB, 1 mg/kg/d) in the treatment of these infections. Of 106 possible patients, 66 were enrolled and analysed for efficacy: nine had documented fungaemia, 17 had other invasive mould infections and 40 had suspected pulmonary aspergillosis. After completion of the course medication, in the AmBisome group (n = 32) 14 patients had achieved complete response, seven a partial response and 11 were failures as compared to 6, 13 and 15 patients (n = 34) treated with AmB (P=0.09); P=0.03 for complete responders. A favourable trend for AmBisome was found at day 14, in patients with documented infections and in patients with pulmonary aspergillosis (P=0.05 and P=0.096 respectively). Mortality rates were lower in patients treated with AmBisome (adjusted for malignancy status, P=0.03). More patients on AmB had a >100% increase of their baseline serum creatinine (P<0.001). The results indicate that, in neutropenic patients with documented or suspected invasive fungal infections AmBisome 5 mg/kg/d was superior to AmB 1 mg/kg/d with respect to efficacy and safety.

Proliferation signaling and activation of Shc, p21Ras, and Myc via tyrosine 764 of human granulocyte colony-stimulating factor receptor

The membrane-distal region of the cytoplasmic domain of human granulocyte colony-stimulating factor receptor (G-CSF-R) contains four conserved tyrosine residues: Y704, Y729, Y744, and Y764. Three of these (Y729, Y744, and Y764) are located in the C-terminal part of G-CSF-R, previously shown to be essential for induction of neutrophilic differentiation. To determine the role of the tyrosines in G-CSF-mediated responses, we constructed tyrosine-to-phenylalanine (Y-to-F) substitution mutants and expressed these in a differentiation competent subclone of 32D cells that lacks endogenous G-CSF-R. We show that all tyrosines can be substituted essentially without affecting the differentiation signaling properties of G-CSF-R. However, substitution of one specific tyrosine, ie, Y764, markedly influenced proliferation signaling as well as the timing of differentiation. 32D cells expressing wild-type (WT) G-CSF-R (or mutants Y704F, Y729F, or Y744F) proliferated in G-CSF-containing cultures until day 8 and then developed into mature neutrophils. In contrast, 32D/Y764F cells arrested in the G1 phase of the cell cycle within 24 hours and showed complete neutrophilic differentiation after 3 days of culture. This resulted in an average 30-fold reduction of neutrophil production as compared with the 32D/WT controls. Importantly, G-CSF-mediated activation of Shc, p21Ras and the induction of c-myc were severely reduced by substitution of Y764. These findings indicate that Y764 of G-CSF-R is crucial for maintaining the proliferation/differentiation balance during G-CSF-driven neutrophil development and suggest a role for multiple signaling mechanisms in maintaining this balance.

Results of allogeneic bone marrow transplants for leukemia using donors other than HLA-identical siblings

PURPOSE

To compare outcomes of bone marrow transplants for leukemia from HLA-identical siblings, haploidentical HLA-mismatched relatives, and HLA-matched and mismatched unrelated donors.

PATIENTS

A total of 2,055 recipients of allogeneic bone marrow transplants for chronic myelogenous leukemia (CML), acute myelogenous leukemia (AML), and acute lymphoblastic leukemia (ALL) were entered onto the study. Transplants were performed between 1985 and 1991 and reported to the International Bone Marrow Transplant Registry (IBMTR). Donors were HLA-identical siblings (n = 1,224); haploidentical relatives mismatched for one (n = 238) or two (n = 102) HLA-A, -B, or -DR antigens; or unrelated persons who were HLA-matched (n = 383) or mismatched for one HLA-A, -B, or -DR antigen (n = 108). HLA typing was performed using serologic techniques.

RESULTS

Transplant-related mortality was significantly higher after alternative donor transplants than after HLA-identical sibling transplants. Among patients with early leukemia (CML in chronic phase or acute leukemia in first remission), 3-year transplant-related mortality (+/-SE) was 21% +/- 2% after HLA-identical sibling transplants and greater than 50% after all types of alternative donor transplants studied. Among patients with early leukemia, relative risks of treatment failure (inverse of leukemia-free survival), using HLA-identical sibling transplants as the reference group, were 2.43 (P < .0001) with 1-HLA-antigen-mismatched related donors, 3.79 (P < .0001) with 2-HLA-antigen-mismatched related donors, 2.11 (P < .0001) with HLA-matched unrelated donors, and 3.33 (P < .0001) with 1-HLA-antigen-mismatched unrelated donors. For patients with more advanced leukemia, differences in treatment failure were less striking: 1-HLA-antigen-mismatched relatives, 1.22 (P = not significant [NS]); 2-HLA-antigen-mismatched relatives, 1.81 (P < .0001); HLA-matched unrelated donors, 1.39 (P = .002); and 1-HLA-antigen-mismatched unrelated donors, 1.63 (P = .002).

CONCLUSION

Although transplants from alternative donors are effective in some patients with leukemia, treatment failure is higher than after HLA-identical sibling transplants. Outcome depends on leukemia state, donor-recipient relationship, and degree of HLA matching. In early leukemia, alternative donor transplants have a more than twofold increased risk of treatment failure compared with HLA-identical sibling transplants. This difference is less in advanced leukemia.

Comparison of doxorubicin and mitoxantrone in the treatment of elderly patients with advanced diffuse non-Hodgkin's lymphoma using CHOP versus CNOP chemotherapy

PURPOSE AND METHODS

A prospective, randomized, multicenter phase III trial was performed to investigate the feasibility of cyclophosphamide, doxorubicin, vincristine, and prednisone (CHOP) chemotherapy in elderly patients ( > or = 60 years) with advanced non-Hodgkin's lymphoma (NHL) of intermediate- and high-grade malignancy, and to compare the tolerance and efficacy of doxorubicin versus mitoxantrone (CHOP v CNOP).

RESULTS

Of 157 enrolled patients, 148 were eligible and 145 were assessable for response. Thirty-one percent of CNOP and 45% of CHOP patients completed six cycles without dose reduction. The cumulative normalized dose-intensity (NDI) was 92% with CHOP and 90% with CNOP after six cycles. The overall complete response (CR) rates were 49% and 31% in CHOP- and CNOP-treated patients, respectively (P = .03). Survival with CNOP was significantly worse as compared with CHOP (P = .03). Lymphoma-specific survival was significantly better in CHOP-treated patients (P = .034) At 3 years, 42% of CHOP and 26% of CNOP patients were alive. Additional unfavorable prognostic factors at diagnosis were high serum lactate dehydrogenase (LDH) level, bulky mass, and low performance status, but not age. The median disease-free intervals of complete responders were 27 (CHOP) and 15 (CNOP) months, respectively. Considering the complete group of patients, at 3 years 17% of CHOP and 13% of CNOP patients were alive and disease-free (P = .12). Common toxicity criteria (CTC) grade > or = 2 with CNOP and CHOP was not different.

CONCLUSION

CHOP is well tolerated in elderly patients with advanced intermediate- or high-grade NHL and its NDI is not seriously impaired. Treatment with CHOP (doxorubicin) results in better CR and survival rates than CNOP (mitoxantrone). CHOP should be recommended for elderly patients with high-risk NHL.

Impact of cytogenetic abnormalities on outcome of bone marrow transplants in acute myelogenous leukemia in first remission

This study analyzed the impact of cytogenetic abnormalities on outcome of 1516 HLA-identical sibling bone marrow transplants for acute myelogenous leukemia (AML) in first remission reported to the International Bone Marrow Transplant Registry by 188 centers. 708 patients (47%) had cytogenetic studies performed. Transplant outcome in these subjects was similar to the 808 in whom cytogenetic studies were not performed. One or more cytogenetic abnormalities were detected in 284 (40%) of subjects studied. Relapse rates were higher and leukemia-free survival lower in patients with poor prognosis abnormalities vs those with no abnormality or with good or intermediate prognosis abnormalities (relative risk of relapse 2.40, P < 0.01; relative risk of treatment failure 1.68, P < 0.03). We conclude that cytogenetic abnormalities correlated with increased relapse in patients treated with chemotherapy. HLA-identical sibling transplants are similar.

Azathioprine-associated pure red cell aplasia

Azathioprine-associated pure red cell aplasia in patients with a renal allograft is a rare complication. Although immunological inhibition of erythroid progenitor cell has been suggested, the cause of this phenomenon remains unclear. The patient we describe showed a decrease in the number of erythroid progenitor cells and no evidence for the presence of a serum inhibitor of these precursor cells. Discontinuation of azathioprine was associated with a complete recovery from anaemia as well, with an increase in the number of erythroid progenitor cells.

Resorption of sintered synthetic hydroxyapatite by osteoclasts in vitro

Primary rat bone marrow cells were cultured for periods of 8 d on hydroxyapatite discs produced by sintering compressed powder at 1130 degrees C. The disc surfaces were roughened using silicon carbide paper to create three groups of samples (n = 10) of differing surface topography. The culture conditions permitted both the differentiation and fusion of cells of the osteoclast lineage. Following culture, the cells were stained in situ for tartrate-resistant acid phosphatase activity, and the samples were prepared for scanning electron microscopy. Evidence of cellular resorption of the hydroxyapatite discs was seen on all samples. Small tartrate-resistant acid phosphatase positive cells created resorption pits of 15-25 microns diameter in the ceramic surface, which were morphologically similar to those found in natural bone tissue, while multinucleate cells caused erosion of the ceramic surface without pit formation. Statistical analyses showed that the total numbers of cells, tartrate-resistant acid phosphatase positive cells, and multinucleated cells were all higher on the roughened surfaces, although the resorption pits were more easily visualized on the smooth surfaces. The results clearly demonstrate that not only are osteoclasts capable of resorbing sintered hydroxyapatite but that the rugosity of the hydroxyapatite influences the fusion of osteoclast mononuclear precursors.

Bone marrow transplantation from related donors other than HLA-identical siblings: effect of T cell depletion

Results of 470 bone marrow transplants from related donors other than genotypically HLA-identical siblings (alternative related donors) were analysed to identify factors associated with transplant outcome and to determine whether T cell depletion improved results. As compared to 3648 transplant from HLA-identical siblings, alternative related donor transplants were associated with increased graft failure, increased acute graft-versus-host disease (GVHD), and lower disease-free survival. The likelihood of adverse outcome correlated with increasing donor-recipient HLA-disparity. In multivariate analysis of alternative related donor transplants, donor age greater than or equal to 30 years, (relative risk [RR] 1.7, p less than 0.006), intermediate and advanced leukemia (RR 1.5 and 1.6, p less than 0.01 and p less than 0.003), infection pretransplant (RR 1.7, p less than 0.005) and 2- and 3-locus donor-recipient HLA-disparity (RR 1.3, p less than 0.04) were associated with increased risks of treatment failure. The 2-year probability of leukemia-free survival after alternative related donor transplants (n = 43) with none of these adverse prognostic features was 44% (95% confidence interval 28-59%) compared to 56% (95% confidence interval 52-59%) for similar patients receiving HLA-identical sibling transplants (n = 868, univariate p less than 0.03). T cell depletion increased graft failure and decreased acute GVHD after alternative related donor transplants but did not improve leukemia-free survival.

The bone-titanium interface in vitro

Commercially pure 5-mm-diameter titanium (cpTi) discs received droplet inoculations of cells derived from rat bone marrow and were maintained in supplemented culture medium for 2-3 weeks. The cells and extracellular matrix (ECM) were processed for observation by light (LM), scanning (SEM), and transmission electron (TEM) microscopy. The latter was achieved by freeze-fracturing the solid metal from the resin-embedded tissue using a method which preserved the interface. Surface staining of whole discs revealed cells separated from the metal substratum by areas of ECM which stained positively using von Kossa's method to identify mineralization. At SEM, the ECM comprised dense interwoven collagen fiber networks which were partially obscured by globular masses (GMs). Individual GMs were associated with collagen fibers, especially at fiber intersections. EDAX line scan analysis confirmed the presence of Ca and P in these areas which were assumed to be spheritic foci of calcification since the Ca and P peaks diminished in areas which demonstrated only collagen fibers or the underlying cpTi. TEM examination confirmed the presence of globular mineralization and also revealed the presence of an interfacial zone between the metal substratum and the mineralized ECM elaborated by osteoblasts during the culture period. The interfacial zone comprised two layers, a bonding zone containing few collagen fragments and a ruthenium red positive layer containing more densely packed collagen fibers. We believe that this is the first report of both the formation of bonelike tissue on solid titanium substrata in vitro and demonstration of an interface which bears close morphological similarities to that known to develop in vivo.