NF-kappaB activation mediates resistance to IFN beta in MLL-rearranged acute lymphoblastic leukemia.

Acute lymphoblastic leukemia (ALL) harboring the t(4;11) translocation is associated with a very poor prognosis; innovative treatment strategies are required to improve the current 5-year survival rate of 30-40%. Interferon beta (IFN beta) has shown promise in the treatment of both solid and hematologic malignancies, although the short half-life and toxicity associated with high doses have limited its clinical utility. To overcome these limitations, we investigated the effect of continuous, gene transfer-mediated delivery of IFN beta using adeno-associated virus (AAV)-mediated expression, on ALL cells with the t(4;11) translocation. We found that this method of IFN beta delivery resulted in complete remission of leukemia in a murine model. However, leukemic cells eventually became resistant to IFN beta and relapse was observed. Activation of NF-kappaB was identified as a mechanism for IFN beta resistance, and inhibition of NF-kappaB activity in resistant cells sensitized cells to IFN beta. IFN beta combined with agents that inhibit NF-kappaB could have therapeutic potential in the treatment of children with mixed lineage leukemia subtype ALL.

Expression microarray analysis of papillary thyroid carcinoma and benign thyroid tissue: emphasis on the follicular variant and potential markers of malignancy.

The most common sub-variant of papillary thyroid carcinoma (PTC) is the so-called follicular variant (FVPTC), which is a particularly problematic lesion and can be challenging from a diagnostic viewpoint even in resected lesions. Although fine needle aspiration cytology is very useful in the diagnosis of PTC, its accuracy and utility would be greatly facilitated by the development of specific markers for PTC and its common variants. We used the recently developed Applied Biosystems 1700 microarray system to interrogate a series of 11 benign thyroid lesions and conditions and 14 samples of PTC (six with classic morphology and eight with follicular variant morphology). TaqMan(R) reverse transcriptase-polymerase chain reaction was used to validate the expression portfolios of 50 selected transcripts. Our data corroborates potential biomarkers previously identified in the literature, such as LGALS3, S100A11, LYN, BAX, and cluster of differentiation 44 (CD44). However, we have also identified numerous transcripts never previously implicated in thyroid carcinogenesis, and many of which are not represented on other microarray platforms. Diminished expression of metallothioneins featured strongly among these and suggests a possible role for this family as tumour suppressors in PTC. Fifteen transcripts were significantly associated with FVPTC morphology. Surprisingly, these genes were associated with an extremely narrow repertoire of functions, including the major histocompatibility complex and cathepsin families.

Antitumor efficacy of AAV-mediated systemic delivery of interferon-beta.

Type I interferons (alpha/beta) have significant antitumor activity although their short half-life and systemic side effects have limited their clinical utility. An alternative dosing schedule of continuous, low-level delivery, as is achieved by gene therapy, rather than intermittent, high concentration pulsed-dosing, might avoid the toxicity of interferon while maintaining its antitumor efficacy. We have tested a gene therapy approach in murine tumor models to treat malignancies that have shown responsiveness to interferon in clinical trials. The tumor cell lines used were moderately sensitive to the direct effects of human interferon-beta (hIFN-beta) in vitro. For in vivo testing, systemic delivery of hIFN-beta was generated following liver-targeted delivery of adeno-associated virus (AAV) vector carrying the hIFN-beta transgene. This prevented engraftment of subcutaneous human gliomas, and orthotopic, localized (intrarenal) and disseminated (primarily pulmonary) human renal cell carcinomas; and caused regression of established tumors at these sites. In a syngeneic, immunocompetent model of melanoma, AAV IFN-beta treatment limited subcutaneous tumor growth and prevented disseminated disease. A significant decrease in mean intratumoral vessel density was demonstrated in hIFN-beta-treated tumors, suggesting that in addition to a direct tumoricidal effect, the antitumor efficacy of AAV IFN-beta in this study was due to its ability to inhibit angiogenesis.

Variability in the 28-kDa surface antigen protein multigene locus of isolates of the emerging disease agent Ehrlichia chaffeensis suggests that it plays a role in immune evasion.

Infections caused by rickettsial pathogens persist in vertebrate hosts for long periods of time, despite the active host immune response. We recently described the multigene locus encoding 28 kDa surface antigen proteins (28 kDa SAPs) for two closely related rickettsials, Ehrlichia chaffeensis and Ehrlichia canis (Reddy, G. R., et al. (1998) Biochem. Biophys. Res. Commun. 247, 636-643), that share extensive structural homology to antigenic variant surface protein genes of Neisseria and Borrelia species. In this study, we describe motifs for recombinase binding sites and a high frequency of repeat elements in the cloned 28 kDa SAP genes. The locus for two newly established E. chaffeensis isolates also was characterized, and immunological specificity of the 28 kDa SAPs was investigated. The study identified variant forms of the 28 kDa SAPs and extensive restriction fragment length polymorphisms among isolates. The molecular data suggest that the locus is influenced by short-term evolutionary changes such as genetic recombinations leading to the generation of antigenic variants. Antigenic variation could contribute to the mechanism of immune evasion and the emergence of new diseases.