Purpose-Lenalidomide is a novel therapeutic agent with uncertain mechanism of action that is clinically active in myelodysplastic syndrome (MDS) and multiple myeloma (MM). Application of high (MM) and low (MDS) doses of lenalidomide has been reported to have clinical activity in CLL. Herein, we highlight life-threatening tumor flare when higher doses of lenalidomide are administered to patients with CLL and provide a potential mechanism for its occurrence. AUTHORS' DISCLOSURES OF POTENTIAL CONFLICTS OF INTERESTAlthough all authors completed the disclosure declaration, the following author(s) indicated a financial or other interest that is relevant to the subject matter under consideration in this article. Certain relationships marked with a "U" are those for which no compensation was received; those relationships marked with a "C" were compensated. For a detailed description of the disclosure categories, or for more information about ASCO's conflict of interest policy, please refer to the Author Disclosure Results-Four consecutive patients were treated with lenalidomide; all had serious adverse events. Tumor flare was observed in three patients and was characterized by dramatic and painful lymph node enlargement resulting in hospitalization of two patients, with one fatal outcome. Another patient developed sepsis and renal failure. In vitro studies demonstrated lenalidomideinduced B-cell activation (upregulation of CD40 and CD86) corresponding to degree of tumor flare, possibly explaining the tumor flare observation.Conclusion-Lenalidomide administered at 25 mg/d in relapsed CLL is associated with unacceptable toxicity; the rapid onset and adverse clinical effects of tumor flare represent a significant limitation of lenalidomide use in CLL at this dose. Drug-associated B-cell activation may contribute to this adverse event. Future studies with lenalidomide in CLL should focus on understanding this toxicity, investigating patients at risk, and investigating alternative safer dosing schedules.

Chronic lymphocytic leukemia (CLL) involves a profound humoral immune defect and tumor-specific humoral tolerance that directly contribute to disease morbidity and mortality. CD154 gene therapy can reverse this immune defect, but attempts to do this pharmacologically have been unsuccessful. The immunemodulatory agent lenalidomide shows clinical activity in CLL, but its mechanism is poorly understood. Here, we demonstrate that lenalidomide induces expression of functional CD154 antigen on CLL IntroductionChronic lymphocytic leukemia (CLL) is the most common adult leukemia, and is characterized by an elevated frequency of infections, secondary malignancy, and autoimmune complications compared with the general population. Current treatment options for CLL are palliative and further exacerbate the immune deficiency seen in this disease. Nonetheless, CLL represents an "immunoresponsive" disease as evidenced by extended disease remission and potential cure with reduced intensity allogeneic stem cell transplantation (reviewed in Gribben 1 ). This suggests that strategies that restore immune function have potential to effectively eliminate CLL.The immune defect in CLL is characterized by both humoral and cellular immune defects. Although detailed studies of normal B cells in CLL patients have not been performed due to the difficulty in isolating these cells, hypogammaglobulinemia is often present at diagnosis and becomes worse with disease progression. A profound cellular immune defect 2-4 is present in CLL with significant alterations in genes involved in differentiation, cytoskeleton formation, vesicle trafficking, and cell death. 4 Coculture of CLL cells with normal T cells produces the same T-cell defects observed in CLL patients, 4 suggesting a direct role of the leukemia cells in contributing to the T cell-dependent cellular immune deficiency. The clinical manifestation of the humoral and cellular immune defects in CLL patients includes hypogammaglobulinemia, 5,6 poor response to both polysaccharide-based 7-9 and proteinbased 10 vaccines, and a high predisposition to infections 11,12 that represents a leading cause of death.To date, attempts to reverse the immune defects in CLL have been limited. Most promising has been adenovirus-delivered CD154 gene therapy that in small numbers of patients reversed cellular and humoral tumor tolerance. CD154 is the surface ligand of CD40 and is expressed on activated T cells, natural killer cells, and dendritic cells, but not normal B cells. Activation of T cells promotes increased surface expression of CD154, thereby promoting both activation and antigen presentation in normal and transformed B cells. Congenital mutations in the CD154 gene promote profound cellular and humoral immune deficiency. Although mutations of the CD154 gene have not been described in CLL, these patients have diminished CD154 expression on T cells after CD3 ligation. 13 Transduction of murine or human CD154 into primary CLL cells ex vivo with adenovirus gene therapy vectors, followed by systemic reintr...

Due to their interesting physicochemical properties, gold nanoparticles (Au-NPs) are the focus of increasing attention in the field of biomedicine and are under consideration for use in drug delivery and bioimaging, or as radiosensitizers and nano-based vaccines. Thorough evaluation of the genotoxic potential of Au-NPs is required, since damage to the genome can remain undetected in standard hazard assessments. Available genotoxicity data is either limited or contradictory. Here, we examined the influence of three surface modified 3-4 nm Au-NPs on human A549 cells, according to the reactive oxygen species (ROS) paradigm. After 24 h of Au-NP treatment, nanoparticles were taken up by cells as agglomerates; however, no influence on cell viability or inflammation was detected. No increase in ROS production was observed by H2-DCF assay; however, intracellular glutathione levels reduced over time, indicating oxidative stress. All three types of Au-NPs induced DNA damage, as detected by alkaline comet assay. The strongest genotoxic effect was observed for positively charged Au-NP I. Further analysis of Au-NP I by neutral comet assay, fluorimetric detection of alkaline DNA unwinding assay, and γH2AX staining, revealed that the induced DNA lesions were predominantly alkali-labile sites. As highly controlled repair mechanisms have evolved to remove a wide range of DNA lesions with great efficiency, it is important to focus on both acute cyto- and genotoxicity, alongside post-treatment effects and DNA repair. We demonstrate that Au-NP-induced DNA damage is largely repaired over time, indicating that the observed damage is of transient nature.