BCR-ABL tyrosine kinase inhibitors for chronic myelogenous leukemia

The spectrum of adult B-lymphoid leukemias with BCR-ABL: molecular diagnostic, cytogenetic, and clinical laboratory perspectives

The Philadelphia (Ph) chromosome is characteristic of chronic myelogenous leukemia (CML), but it is also the most frequent cytogenetic abnormality in precursor B-lymphoblastic leukemia (ALL) of adults. The vast majority of CML patients have a BCR-ABL translocation that yields a 210 kD (p210) oncoprotein, whereas adult Ph-positive ALL cases can present with either a p190 or a p210 oncoprotein, or both. Considering that 30% of the patients with CML that progress to blast crisis will have a lymphoblastic presentation, adults presenting with a p210 ALL may have either a de novo ALL or CML presenting for the first time in lymphoblastic phase. To identify the distinguishing features, cases of p190-ALL, p210-ALL, and lymphoblastic CML were compared. In spite of significant overlap between the three entities, a number of features were found to aid in their differentiation. p210-ALL patients present at a younger age with blasts that frequently show loss of expression of CD34, whereas p190-ALL patients present with marked increase in peripheral blast percentage. Interestingly, bone marrow findings characteristic of a myeloproliferative disorder are specific, but are not sensitive for lymphoblastic CML. This study suggests that despite the similarities between these leukemias, p190-ALL, p210-ALL, and lymphoblastic phase CML likely represent three distinct diseases.

Chronic myeloid leukaemia: the evolution of gene-targeted therapy

Chronic myeloid leukaemia (CML) was the first human cancer linked to an acquired chromosomal abnormality, subsequently shown to be a reciprocal translocation between chromosomes 9 and 22. The resulting fusion gene product, BCR-ABL, was shown to be the causative agent of the disease. CML has an incidence of around 1-2 cases per 100,000; in Australia, there are probably more than 200 new cases per year and more than 1300 prevalent cases. Treatment of CML with imatinib has been a powerful vindication of the concept of rational, gene-targeted drug design. Five-year published experience with imatinib at 400 mg orally daily demonstrates 89% overall survival and an estimated 93% freedom from disease progression. Adverse effects are mostly mild and transient. Higher doses of imatinib may be more efficacious and will be studied in upcoming clinical trials in Australia; however, imatinib is almost certainly not curative. Up to 28% of patients may have to stop imatinib because of intolerance or disease resistance, mostly due to point mutations of BCR-ABL. In this situation, many patients will respond to second- and third-generation tyrosine kinase inhibitors. Management of CML patients should involve close monitoring, especially in the first 2 years, with regular cytogenetics and quantitative polymerase chain reaction to optimise response and identify suboptimal responders as early as possible. Bone marrow transplantation remains the only known cure, but is reserved for patients whose kinase inhibitor therapy has failed, or who have advanced disease (accelerated phase or blastic transformation).

A phase II study of continuous infusion homoharringtonine and cytarabine in newly diagnosed patients with chronic myeloid leukemia: CALGB study 19804

BACKGROUND

Both homoharringtonine (HHT), an alkaloid derivative from the Chinese yew tree that inhibits protein synthesis, and low-dose cytarabine have independent activity in CML and have been used in combination after failure of interferon therapy.

PATIENTS AND METHODS

The CALGB performed a phase II trial of HHT (2.5 mg/m(2) per day) plus cytarabine (7.5 mg/m(2) per day), given together via continuous intravenous infusion for 7 days in previously untreated patients with Ph chromosome positive chronic phase CML. HHT/cytarabine cycles were repeated every 28 days if the blood counts were adequate. The primary endpoint was the major cytogenetic response rate after 9 months.

RESULTS

Forty of the 44 enrolled patients required reduction in the infusion duration during at least one cycle. Myelosuppression was common; 66% developed neutrophil count <500/microl, but grade 3 infections occurred in only 7%. Thirty-six of 44 patients (82%) achieved a complete hematologic remission; the median duration has not been reached. Only 4 of the 23 patients (17%) having adequate cytogenetic response assessment achieved a major response within nine cycles.

CONCLUSIONS

Although HHT/cytarabine was generally well tolerated, the cytogenetic response rate did not exceed the level previously seen in patients with interferon-refractory CML and was not nearly as high as associated with imatinib in newly diagnosed patients.

Diversity synthesis of complex pyridines yields a probe of a neurotrophic signaling pathway

Recognizing the value of including complex pyridines in small-molecule screening collections, we developed a previously unexplored [2 + 2 + 2]-cycloaddition of silyl-tethered diynes with nitriles. The tether provides high regioselectivity, while the solvent THF allows catalytic CpCo(CO)₂ to be used without exogenous irradiation. One of the resulting bicyclic and monocyclic (desilylated) pyridines was identified as an inhibitor of neuregulin-induced neurite outgrowth (EC₅₀ = 0.30 µM) in a screen that probes a pathway likely to be involved in breast cancers and schizophrenia.

High-throughput kinase profiling as a platform for drug discovery

To fully exploit the potential of kinases as drug targets, novel strategies for the efficient discovery of inhibitors are required. In contrast to the traditional, linear process of inhibitor discovery, high-throughput kinase profiling enables a parallel approach by interrogating compounds against hundreds of targets in a single screen. Compound potency and selectivity are determined simultaneously, providing a choice of targets to pursue that is guided by the quality of lead compounds available, rather than by target biology alone.

A multidisciplinary approach for the treatment of GIST liver metastasis

Background

Advanced gastrointestinal stromal tumors (GISTs) can metastasize and recur after a long remission period, resulting in serious morbidity, mortality, and complex management issues.

Case presentation

A 67-year-old woman presented with epigastric fullness, mild jaundice and weight loss with a history of a bowel resection 7 years prior for a primary GIST of the small bowel. The finding of a heterogeneous mass 15.5 cm in diameter replacing most of the left lobe of the liver by ultrasonography and CT, followed by positive cytological studies revealed a metastatic GIST. Perioperative optimization of the patient's nutritional status along with biliary drainage, and portal vein embolization were performed. Imatinib was successful in reducing the tumor size and facilitating surgical resection.

Conclusion

A well-planned multidisciplinary approach should be part of the standard management of advanced or metastatic GIST.

Met receptor contributes to trastuzumab resistance of Her2-overexpressing breast cancer cells

Her2 is overexpressed in 20% to 30% of breast tumors and correlates with reduced disease-free and overall patient survival. Trastuzumab, a humanized monoclonal antibody directed against Her2, represents the first Her2-targeted therapy, which decreases the risk of relapse and prolongs patient survival. Resistance to trastuzumab, both inherent and treatment-acquired, represents a significant barrier to the effective treatment of Her2 (+) breast cancer. The Met receptor tyrosine kinase is aberrantly expressed in breast cancer and predicts poor patient prognosis. In this study, we find that Met is frequently expressed in Her2-overexpressing breast cancer cells, as well as Her2 (+) breast cancer. Importantly, Met contributes to trastuzumab resistance, as inhibition of Met sensitizes cells to trastuzumab-mediated growth inhibition, whereas Met activation protects cells against trastuzumab by abrogating p27 induction. Remarkably, Her2-overexpressing breast cancer cells rapidly up-regulate Met expression after trastuzumab treatment, promoting their own resistance. Our study suggests that a subset of Her2 (+) patients may benefit from combined inhibition of Her2 and Met.

Systemic and targeted therapy for advanced colon cancer

Colorectal cancer (CRC) is the third most common malignancy and the second most common cause of cancer-related death in the USA. Prognosis is best when the disease is detected early; however, nearly two-thirds of newly diagnosed cases of CRC have lymph node involvement or metastatic disease. For years, 5-fluorouracil (FU)-based regimens represented the only viable treatment option for patients with metastatic CRC. However, in recent years several newer agents have been added to the treatment arsenal for this disease. These agents include oxaliplatin, irinotecan and newer monoclonal antibodies targeting the epidermal growth factor receptor (cetuximab and panitumumab) and VEGF (bevacizumab). This review aims to discuss current systemic and targeted therapies for metastatic colon cancer with a focus on mechanism of action, indications, toxicity and efficacy.

Molecular oncology: current trends in diagnostics

Applications of molecular diagnostics to oncology have been slow to make their way to the clinical laboratory. While numerous genes and mutation spectra have been found to be involved in tumorigenesis, it is only recently that these findings begin to become useful in a clinical setting. Building on the technical knowledge obtained from molecular infectious disease testing, new instruments and assays have been developed to answer similar questions regarding qualitative, quantitative and genotyping issues. In this manuscript we describe two current examples of clinical molecular diagnostic applications, the assessment of BCR–ABL in chronic myelogenous leukemia patients and the detection of tumor cells in the sentinel lymph nodes of breast cancer patients, to demonstrate the role of molecular techniques in a routine clinical setting.

Current status of antivascular therapy and targeted treatment in the clinic

Antivascular and targeted therapy are now an integrated part of the treatment of myelogenous leukemias, GIST tumours, B-cell lymphomas and breast cancer. In various malignancies improved responses and prolongation of survival for several months is regularly reported. The progress in this field is relevant for hyperthermia. Heat has among other effects documented antivascular effects, and can be considered as one of the established methods in the field based on several randomised phase III studies. Hyperthermia should be considered for combination with other antiangiogenic agents.