Risikoadaptierte Therapie der akuten myeloischen Leukämie

Genetic and molecular techniques have provided increasing insights into the biology of acute myeloid leukemia (AML). These investigations showed that AML is not a homogeneous disease but a heterogeneous group of biologically different subentities. These subentities are currently primarily defined by cytogenetics and molecular markers. They differ substantially in response to therapy and long-term outcome and hence allow different risk groups of patients to be defined. These will guide therapeutic decisions in future therapeutic strategies and may ultimately lead to an individualized treatment concept.

Towards a pathogenesis-oriented therapy of acute myeloid leukemia

Genetic and molecular techniques have provided increasing insights into the biology of acute myeloid leukemia (AML). These investigations showed that AML is not a homogeneous disease but a heterogeneous group of biologically different subentities. These subentities are currently primarily defined by cytogenetics by which three main subgroups can be discriminated: AML with balanced translocations, AML with unbalanced aberrations and AML without cytogenetically detectable aberrations. Within the latter group molecular alterations are identified in more than half of cases such as NPM mutations, FLT3 mutations, MLL duplications and mutations of CEBP-alpha. The clinical meaning of these findings is illustrated by substantial differences in response to therapy and long-term outcome. As demonstrated by the recent multicenter trial of the German AML Cooperative Group (AMLCG) and other studies intensification of induction therapy may improve the results in distinct subtypes but fails to do so in others. Therefore, new strategies need to be explored which incorporate the knowledge about the biology of AML to develop biology adapted treatment strategies. This process has just begun and is predominantly determined by the availability of new agents and their evaluation in clinical phase I and II studies. A variety of targets are currently explored and some trials have yielded promising results already. The step towards a biology adapted treatment of AML is long and requires the combined efforts of researchers, clinicians and the pharmaceutical industry. The first steps towards this goal have been taken and give rise to the hope for more effective and more specific therapies of AML.

Molekulare Zielstrukturen in der Onkologie

Substantial progress has been made in recent years in understanding the molecular pathogenesis of malignant disorders, especially in identification of molecular targets for therapeutic interventions ("targeted therapies"). An important group of therapeutical targets are signaling cascades, e.g. protein tyrosine kinases (PTK) that are activated by mutations, translocations or overexpression. Small molecule inhibitors that compete with ATP and inhibit kinase activity have produced clinical impressive responses in chronic myeloid leukemia, gastrointestinal stroma tumors and non-small cell lung cancer. Another group of cellular targets is represented by tumor-selective cell surface proteins that can serve as target structures for antibodies. Therapeutical concepts using monoclonal antibodies have substantially improved response rates in patients with malignant lymphomas and are currently evaluated in other types of cancer. The definition of molecular target structures critical for the malignant phenotype is driving a new era of integrated diagnostics and therapeutics in the field of oncology.

Brain metastases in metastatic non-small cell lung cancer responding to single-agent gefitinib: a case report

Brain metastases are a frequent finding in patients with non-small cell lung cancer (NSCLC). The present case reports the clinical course of a patient who was treated with gefitinib alone for progressive brain metastases after whole-brain irradiation treatment (WBRT). A 50-year-old women with primary stage IV NSCLC (bone metastases) developed brain metastases after 3 cycles of chemotherapy consisting of paclitaxel and carboplatin (CBDA). After completion of the WBRT, magnetic resonance imaging (MRI) indicated further progression. Two cycles of temozolomide and topotecan were applied; this was ineffective in preventing central nervous system progression. For symptomatic brain metastatic disease the patient received gefitinib as single-agent treatment. Within a few weeks of treatment there was an obvious clinical improvement. Follow-up of the brain 2 months after the start of treatment showed a decrease in both the size and number of brain metastases. Additional manifestations in the lungs and the skeletal system were re-assessed as stable disease during the treatment with gefitinib. Within 4 months of treatment there were no side-effects such as skin rash or any other systemic toxicity. Gefitinib may therefore have a role in the treatment of brain metastases from NSCLC.

New insights into MLL gene rearranged acute leukemias using gene expression profiling: shared pathways, lineage commitment, and partner genes

Rearrangements of the MLL gene occur in both acute lymphoblastic and acute myeloid leukemias (ALL, AML). This study addressed the global gene expression pattern of these two leukemia subtypes with respect to common deregulated pathways and lineage-associated differences. We analyzed 73 t(11q23)/MLL leukemias in comparison to 290 other acute leukemias and demonstrate that 11q23 leukemias combined are characterized by a common specific gene expression signature. Additionally, in unsupervised and supervised data analysis algorithms, ALL and AML cases with t(11q23) segregate according to the lineage they are derived from, that is, myeloid or lymphoid, respectively. This segregation can be explained by a highly differing transcriptional program. Through the use of novel biological network analyses, essential regulators of early B cell development, PAX5 and EBF, were shown to be associated with a clear B-lineage commitment in lymphoblastic t(11q23)/MLL leukemias. Also, the influence of the different MLL translocation partners on the transcriptional program was directly assessed. Interestingly, gene expression profiling did not reveal a clear distinct pattern associated with one of the analyzed partner genes. Taken together, the identified molecular expression pattern of MLL fusion gene samples and biological networks revealed new insights into the aberrant transcriptional program in 11q23/MLL leukemias.

Prognostic impact of RT-PCR-based quantification of WT1 gene expression during MRD monitoring of acute myeloid leukemia

In search for general PCR targets for minimal residual disease (MRD) studies in acute myeloid leukemia (AML), Wilms' tumor gene 1 (WT1) expression was assessed by real-time RT-PCR relative to the control gene ABL in 569 archived samples of AML patients (pts). Pts were analyzed at diagnosis (n=116) and during follow-up (n=105, median 4 times, range 2--17). Median follow-up time was 258 days (range 16--1578 days). In 66 pts, the WT1 expression was analyzed in comparison to a second PCR marker or to multiparameter flow cytometry. Quantitative WT1 levels correlated to the clinical course or a second marker in 83-96% of the cases. Prognostic significance of WT1 levels was analyzed at diagnosis and three intervals: (1) days 16--60, (2) days 61--120, and (3) days 121--180 after start of chemotherapy. Higher levels of WT1 expression were associated with shorter overall survival (OS) and event-free survival (EFS) within intervals 2 and 3 but not at diagnosis or interval 1. In addition, within these intervals, WT1/ABL levels <or=0.4% were associated with improved OS and EFS. An increase of WT1 levels was detected in 16/44 cases, which subsequently relapsed within a median of 38 days (range 8--180 days). In conclusion, quantification of WT1 may be used for MRD studies and for prognostification in AML.

Genomic gains and losses influence expression levels of genes located within the affected regions: a study on acute myeloid leukemias with trisomy 8, 11, or 13, monosomy 7, or deletion 5q

We performed microarray analyses in AML with trisomies 8 (n=12), 11 (n=7), 13 (n=7), monosomy 7 (n=9), and deletion 5q (n=7) as sole changes to investigate whether genomic gains and losses translate into altered expression levels of genes located in the affected chromosomal regions. Controls were 104 AML with normal karyotype. In subgroups with trisomy, the median expression of genes located on gained chromosomes was higher, while in AML with monosomy 7 and deletion 5q the median expression of genes located in deleted regions was lower. The 50 most differentially expressed genes, as compared to all other subtypes, were equally distributed over the genome in AML subgroups with trisomies. In contrast, 30 and 86% of the most differentially expressed genes characteristic for AML with 5q deletion and monosomy 7 are located on chromosomes 5 or 7. In conclusion, gain of whole chromosomes leads to overexpression of genes located on the respective chromosomes. Losses of larger regions of the genome translate into lower expression of the majority of genes represented by only one allele. The reduced expression of these genes is the most characteristic difference in gene expression profiles between AML with monosomy 7 and AML with deletion 5q, respectively, and other AML subtypes. Therefore, these data provide evidence that gene dosage effects gene expression in AML with unbalanced karyotype abnormalities. Losses of specific regions of the genome determine the gene expression profile more strongly than the gain of whole chromosomes.