Toward a therapeutic reduction of imatinib refractory myeloproliferative neoplasm-initiating cells.

Myeloproliferative neoplasms (MPNs) such as chronic myelogenous (CML) and chronic myelomonocytic leukemias (CMML) are frequently induced by tyrosine kinase oncogenes. Although these MPNs are sensitive to tyrosine kinase inhibitors such as imatinib, patients often relapse upon withdrawal of therapy. We used a model of MPN, which is induced by co-expression of the oncoproteins HIP1/PDGFßR (H/P) and AML1/ETO from their endogenous loci, to examine the mechanisms of disease development and recurrence following imatinib withdrawal. Although the MPN displayed a full hematologic response to imatinib, 100% of the diseased mice relapsed upon drug withdrawal. MPN persistence was not due to imatinib resistance mutations in the H/P oncogene or massive gene expression changes. Within 1 week of imatinib treatment, more than 98% of gene expression changes induced by the oncogenes in isolated hematopoietic stem and progenitor cells (lineage(-)Sca-1(+)c-Kit(+) immunophenotype) normalized. Supplementation of imatinib with granulocyte colony-stimulating factor or arsenic trioxide reduced MPN-initiating cell frequencies and the combination of imatinib with arsenic trioxide cured a large fraction of mice with MPNs. In contrast, no mice in the imatinib-treated control cohorts were cured. These data suggest that treatment with a combination of arsenic trioxide and imatinib can eliminate refractory MPN-initiating cells and reduce disease relapse.

Tumor cells express FcgammaRI which contributes to tumor cell growth and a metastatic phenotype.

High levels of circulating immune complexes containing tumor-associated antigens are associated with a poor prognosis for individuals with cancer. The ability of B cells, previously exposed to tumor-associated antigens, to promote both in vitro and in vivo tumor growth formed the rationale to evaluate the mechanism by which immune complexes may promote tumor growth. In elucidating this mechanism, FcgammaRI expression by tumor cells was characterized by flow cytometry, polymerase chain reaction, and sequence analysis. Immune complexes containing shed tumor antigen and anti-shed tumor antigen Ab cross-linked FcgammaRI-expressing tumor cells, which resulted in an induction of tumor cell proliferation and of shed tumor antigen production. Use of selective tyrosine kinase inhibitors demonstrated that tumor cell proliferation induced by immune complex cross-linking of FcgammaRI is dependent on the tyrosine kinase signal transduction pathway. A selective inhibitor of phosphatidylinositol-3 kinase also inhibited this induction of tumor cell proliferation. These findings support a role for immune complexes and FcgammaRI expression by tumor cells in augmentation of tumor growth and a metastatic phenotype.

Analysis of extemporaneous alprostadil formulaions.

Twenty-two extemporaneous alprostadil (PGE1) injection solutions samples from five different suppliers and three Caverject (Pharmacia and Upjohn, Inc., Bridgewater, NJ) samples from three different lots, all intended for the clinical treatment of erectile dysfunction, were analyzed to determine PGE1 concentration, assess formation of the PGE1 aqueous breakdown product (PGA1), define pH and assess active microbial contamination. High-pressure liquid chromatography (HPLC), pH meter and cell culture techniques were used to conduct the analyses. Of the 22 extemporaneously formulated samples, six showed PGE1 concentrations 10% greater than their listed amounts and seven showed PGA1 weight fractions corresponding to at least 1.5% of the total prostaglandidn content. It should be noted that no standard has been published in the United States Pharmacopeia/National Formulary for this preparation as of this date. All samples were within the pH range 4.5 to 6.0. Four samples tested positive for active microbial contamination. In adition, nearly all the extemporaneously formulated samples contained what appeared to be benzyl alcohol, and about one half had at least two other undefined peaks within their HPLC chromatograms. In contrast, all three Caverject samples were within +/- 7.5% of their listed PGE1 concentrations while showing PGA1 prostaglandins weight fractions of less 0.6%, all were within the pH range 4.0 to 4.5 and all tested negative for active microbial contamination. Chromatograms of the Caverject samples also diplayed peaks consistent with the presence of benzyl alcohol but did not exhibit addtional undefined peaks. The results suggest that significant variations in PGE1 concentration and in PGA1 formation, accompanied by the possibility of microbial contamination, can occur as a result of the extemporaneous formulation and subsequent transfer of this type of product as a premixed solution intended for treating erectile dysfunction.