F C Marini

Interleukin (IL)-1beta is constitutively expressed in many leukemias and operates as an autocrine growth factor. To study the cellular basis for this aberrant production, we analyzed two cell lines, B1 (acute lymphoblastic leukemia) and W1 (juvenile chronic myelogenous leukemia), which express high levels of IL-1beta and have mutations in the K-RAS and N-RAS genes, respectively. Electromobility shift assays demonstrated transcription factor binding at multiple IL-1beta promoter elements [nuclear factor (NF)-IL6/CREB, NFB1, NFkappaB, and NF-IL6], consistent with the activation of an upstream signaling pathway. To determine whether activated Ras was involved, two structurally distinct classes of farnesyltransferase (FTase) inhibitors (the monoterpenes and a peptidomimetic) and an adenoviral vector expressing antisense targeted to K-RAS were used to specifically interfere with Ras function and/or expression. Treatment with the FTase inhibitors resulted in a concentration-dependent decrease in both NF-IL6/CREB binding to the IL-1beta promoter and IL-1beta protein levels, without a significant change in total cellular protein levels. Furthermore, exposure of the B1 cells to antisense against K-RAS resulted in an approximately 50% reduction in both p21Ras and IL-1beta protein levels. Growth suppression was observed after FTase inhibitor or antisense exposure, an effect that was partially reversible by the addition of recombinant IL-1beta to the cultures. Our observations suggest that mutated RAS genes may mediate autocrine IL-1beta production in some leukemias by stimulating signal transduction pathways that activate the IL-1beta promoter.

A molecular marker, human alpha-1-antitrypsin (hAAT) was transduced into tumor cells and its secretion was found to correlate with tumor growth or regression, allowing for an accurate and continuous measurement of tumor growth kinetics. Using this system, we investigated the therapeutic potential produced purely from the bystander effect of HSVtk+ CT26 cells to eradicate established CT26 colon carcinomas in mice by direct intratumoral implantation and subsequent ganciclovir administration. With lower ratios (0.1% and 1% of initial tumor burden), tumor growth kinetics went into a static (remission) phase of approximately 2 weeks duration before relapse and resumption of progressive tumor growth. When the number of CT26tk+ modified cells injected into the tumor equaled 10% to 100% of the initial tumor cell number the bystander effect was sufficient to completely eradicate established tumors indicating that a potent bystander killing effect is produced in this system, and that a cellular therapy based on this approach may have applications.