The CFU-C assay in patients with neutropenia and, in particular, drug associated neutropenia

Cucurbitacin B, a novel in vivo potentiator of gemcitabine with low toxicity in the treatment of pancreatic cancer

BACKGROUND AND PURPOSE

Pancreatic cancer is a highly aggressive malignancy, and improvement in systemic therapy is necessary to treat this frequently encountered metastatic disease. The current targeted agents used in combination with gemcitabine improved objective response rates, but with little or no improvements in survival and also increased toxicities in pancreatic cancer patients. Recently, we showed that the triterpenoid cucurbitacin B inhibited tumour growth in pancreatic cancer cells by inhibition of the JAK/STAT pathway, and synergistically increased antiproliferative effects of gemcitabine in vitro.

EXPERIMENTAL APPROACH

The anti-tumour effects and toxicities of cucurbitacin B in combination with gemcitabine were tested against human pancreatic cancer cells in a murine xenograft model.

KEY RESULTS

Combined therapy with cucurbitacin B and gemcitabine at relatively low doses (0.5 mg x kg(-1) and 25 mg x kg(-1) respectively) resulted in highly significant tumour growth inhibition of pancreatic cancer xenografts (up to 79%). Remarkably, this therapy was well tolerated by the animals, as shown by histology of visceral organs, analysis of serum chemistry, full blood counts and bone marrow colony numbers. Western blot analysis of the tumour samples of mice who received both cucurbitacin B and gemcitabine, revealed stronger inhibition of Bcl-XL, Bcl-2 and c-myc, and higher activation of the caspase cascades, than mice treated with either agent alone.

CONCLUSIONS AND IMPLICATIONS

Combination of cucurbitacin B and gemcitabine had profound anti-proliferative effects in vivo against xenografts of human pancreatic cancer cells, without any significant signs of toxicity. This promising combination should be examined in therapeutic trials of pancreatic cancer.

Prospective in vitro testing for drug-induced neutropenia in a patient requiring anti-malarial prophylaxis: confirmation of findings on exposure of patient to drug

A patient with moderate pancytopenia thought to be due to chloroquine ingestion was shown to have granulocyte progenitors (CFU-G) which were abnormally sensitive in vitro to chloroquine. As he required further anti-malarial prophylaxis, his marrow was prospectively tested in vitro with proguanil and its metabolite cycloguanil. The patient's CFU-G were also abnormally sensitive to these agents and predicted neutropenia was verified when the patient had a trial course of proguanil. We believe this is the first instance of in vivo confirmation of in vitro CFU-G drug sensitivities.

Alternative testing systems for evaluating noncarcinogenic, hematologic toxicity

Hematopoietic tissues are the targets of numerous xenobiotics. Clinical hematotoxicity is either a decrease or an increase in peripheral blood cell counts in one or more cell lineages--a cytopenia or a cytosis, respectively--that carries a risk of an adverse clinical event. The purpose of in vitro hematotoxicology is the prediction of these adverse hematologic effects from the effects of the toxicants on human hematopoietic targets under controlled experimental conditions in the laboratory. Building on its important foundations in experimental hematology and the wealth of hematotoxicology data found in experimental oncology, this field of alternative toxicology has developed rapidly during the past decade. Although the colony-forming unit-granulocyte/monocyte neutrophil progenitor is most frequently evaluated, other defined progenitors and stem cells as well as cell types found in the marrow stroma can be evaluated in vitro. End points have been proposed for predicting toxicant exposure levels at the maximum tolerated dose and the no observable adverse effect level for the neutrophil lineage, and several clinical prediction models for neutropenia have developed to the point that they are ready for prospective evaluation and validation in both preclinical species and humans. Known predictive end points are the key to successful comparisons across species or across chemical structures when in vitro dose-response curves are nonparallel. Analytical chemistry support is critical for accurate interpretation of in vitro data and for relating the in vitro pharmacodynamics to the in vivo pharmacokinetics. In contrast to acute neutropenia, anemia and acute thrombocytopenia, as well as adverse effects from chronic toxicant exposure, are much more difficult to predict from in vitro data. Pharmacologic principles critical for clinical predictions from in vitro data very likely will apply to toxicities to other proliferative tissues, such as mucositis.

Drug-induced neutropenia due to direct effects on CFU-C--ten years of culture experience

Seventeen patients with suspected drug-induced neutropenia were referred to our laboratory for investigation within a 10-year period. In each case, the suspected drugs were incorporated separately into in vitro cultures of the patients' bone marrow. The cultures were performed in triplicate, using multiple controls. In 10 of these patients a drug-induced inhibition of CFU-C was demonstrated in vitro. The in vitro culture technique is a valuable investigation in patients with suspected drug-induced neutropenia, as it can help identify the causative agent, especially in cases of multidrug administration. It also has a useful application in allowing the clinician to predict drugs to which a patient may be unduly sensitive, and prescribe accordingly.