Immunomodulating drugs for chronic lymphocytic leukaemia

Thalidomide exerts distinct molecular antileukemic effects and combined thalidomide/fludarabine therapy is clinically effective in high-risk chronic lymphocytic leukemia

Thalidomide represents a promising immunomodulatory drug that targets both leukemia cells and the tumor microenvironment. We treated patients with chronic lymphocytic leukemia (CLL) with a combined thalidomide/fludarabine regimen and monitored cellular and molecular changes induced by thalidomide in vivo before fludarabine treatment. Thalidomide was given daily (100 mg p.o. per day) and fludarabine was administered on days 7-11 (25 mg/m(2) i.v. per day) within each 4-week cycle (maximum of 6 cycles). Twenty patients received thalidomide/fludarabine as first-line therapy and 20 patients were previously treated. Unmutated IgVH mutation status was found in 36 cases and 13 had high-risk cytogenetic aberrations (del17p, del11q). The overall response rate was 80 and 25% for untreated and previously treated patients, respectively. Although thalidomide reduced the number of CLL cells, the number of CD3 lymphocytes showed no significant change, but the number of CD4(+)CD25(hi)FOXP3(+) regulatory T cells (Tregs) was significantly decreased. Gene expression profiling revealed a thalidomide-induced signature containing both targets known to have a function in immunomodulatory drug action as well as novel candidate genes. Combined thalidomide/fludarabine therapy demonstrated efficacy in high-risk patients with CLL. Furthermore, our study provides novel biological insights into thalidomide effect, which might act by enhancing apoptosis of CLL cells and reducing Tregs, thereby enabling T-cell-dependent antitumor effect.

Treatment of chronic lymphocytic leukemia with a hypomethylating agent induces expression of NXF2, an immunogenic cancer testis antigen

PURPOSE

Critical to the success of active immunotherapy against cancer is the identification of immunologically recognized cancer-specific proteins with low tolerogenic potential. Cancer testis antigens (CTA), in particular, fulfill this requirement as a result of their aberrant expression restricted to cancer cells and lack of expression in normal tissues bypassing tolerogenic mechanisms against self. Although CTAs have been extensively studied in solid malignancies, little is known regarding their expression in chronic lymphocytic leukemia (CLL).

EXPERIMENTAL DESIGN

Using a two-pronged approach we evaluated the immunogenicity of 29 CTAs in 22 patients with CLL and correlated these results to reverse transcriptase PCR data from CLL cell lines and patient cells.

RESULTS

We identified IgG-specific antibodies for one antigen, NXF2, and confirmed this response by ELISA and Western blot. We found that treatment of CLL with 5-aza-2'-deoxycytidine can induce expression of NXF2 that lasted for several weeks after treatment. Treatment also increased levels of MHC and costimulatory molecules (CD80, CD86, and CD40) necessary for antigen presentation. In addition, we identified other promising antigens that may have potential immunotherapeutic application.

CONCLUSIONS

Our findings suggest that NXF2 could be further pursued as an immunotherapeutic target in CLL, and that treatment with demethylating agents could be exploited to specifically modulate CTA expression and effective antigen presentation in malignant B cells.

N9986: a phase II trial of thalidomide in patients with relapsed chronic lymphocytic leukemia

We enrolled 28 eligible patients with relapsed chronic lymphocytic leukemia (CLL) to a phase II study of single agent thalidomide (200 mg/d, with dose escalation up to 1000 mg/d over 60 days). The median age was 66 years and 71% were males. Study participants received a median of 2 (range 1-7) prior treatment regimens and 61% had Rai stage 3-4 disease at enrollment. Grade 3 or higher hematologic toxicity was observed in 13 (46%) and 16 (57%) had grade 3 or higher non-hematologic toxicity. Grade 3-4 tumor flare was observed in five (18%) patients. The overall response rate was 11% (3 of 28) with one (4%) complete remission and two (7%) partial remissions. Duration of response for these three responders was 3, 14 and 15 months. Fourteen (50%) patients had stabilisation of disease for a median duration of 8 months (95% CI: 7-16 months). Median time to progression for all 28 patients was 7.3 months. Although thalidomide appears to have modest clinical activity in pretreated/relapsed CLL primarily based on reduction of the absolute lymphocyte count, in our opinion the toxicity profile precludes it from more active investigation in CLL.

Thalidomide inhibits leukemia cell invasion and migration by upregulation of early growth response gene 1

Thalidomide has been shown to exert its antitumor activity through the significant effects on microenvironment and immunomodulatory properties. In this study, 10 microM thalidomide treatment markedly increased the expression of the early growth response gene 1 (Egr-1) at both mRNA and protein levels in HL-60 leukemic cells. Thalidomide treatment significantly decreased the invasive cells number through Matrigel and human umbilical vein endothelial cells when compared with the controls. Moreover, the inhibitory effects could be markedly abolished by Egr-1 gene silencing with siRNA technology. Our data indicated thalidomide could suppress leukemia cell invasion and migration by upregulation of Egr-1, suggesting a novel mechanism of thalidomide in the treatment of leukemia. Further investigations are needed to explore the detailed mechanism of Egr-1 induction by thalidomide and the downstream pathways involved in the regulation of leukemia cell invasion.

Lenalidomide down-regulates the CD20 antigen and antagonizes direct and antibody-dependent cellular cytotoxicity of rituximab on primary chronic lymphocytic leukemia cells

Lenalidomide, an immunomodulatory agent that enhances antibody-dependent cellular cytotoxicity (ADCC), is currently being investigated as a therapy for chronic lymphocytic leukemia (CLL). The anti-CD20 antibody rituximab is active in CLL and represents a rational agent to combine with lenalidomide. We therefore examined whether lenalidomide combined with rituximab enhances direct apoptosis and ADCC in CLL cells. In contrast to previous reports using CD20-positive lymphoma cell lines, lenalidomide down-regulated CD20 surface antigen expression in CLL patient cells via enhanced internalization, without influencing transcription. The CD20 surface antigen internalization enhanced delivery of an oligonucleotide incorporated into anti-CD20 immunoliposomes. In addition, CD20 surface antigen down-modulation by lenalidomide in CLL was accompanied by diminished rituximab-mediated apoptosis and ADCC. These observations suggest a need for alternative sequencing strategies to avoid antagonism between lenalidomide and rituximab therapy in CLL. In addition, they suggest that lenalidomide therapy might be useful to enhance targeted delivery of RNAi-based therapies using CD20 immunoliposomes in B-cell malignancies.

CC-4047 promotes Th1 cell differentiation and reprograms polarized human Th2 cells by enhancing transcription factor T-bet

The IMiDs immunomodulatory drugs are an expanding family of compounds under investigation in a broad range of diseases because they exhibit immunomodulatory and anti-tumorigenic properties. Although the molecular targets remain unidentified, the broad activity of select IMiDs immunomodulatory drugs on cell signaling pathways and transcription regulation has been partly described. One characteristic of these compounds is their ability to act as a co-stimulus of TCR ligation leading to increased IL-2, TNF-alpha and IFN-gamma expression indicative of a Th1 phenotype. Because clinical evidence for this response has been observed in thalidomide and lenalidomide treated patients, we investigated the effect of CC-4047 on T cell activation and differentiation at the molecular level. We used primary human CD4(+) T cells as a model and found that CC-4047 enhances the expression of transcription factor T-bet in both naive and pre-polarized Th2 cells. This modulation leads to upregulation of Th1 markers and cytokine production. By increasing the expression of T-bet, CC-4047 promotes the differentiation of naive T-cells to Th1 as well as effectively reverting Th2 cells into Th1-like effector cells in vitro. These findings elucidate a novel mechanism of action of CC-4047 on T cell differentiation, suggesting that certain IMiDs immunomodulatory drugs may have expanded clinical application in treating both allergic diseases and certain T cell lymphomas where a predominant Th2 phenotype is displayed.

Emerging drugs for rarer chronic lymphoid leukemias

BACKGROUND

Rarer indolent lymphoid leukemias include well defined mature B-cell and T-cell neoplasm with widely varying natural history and specific morphological, immunophenotypic and molecular characteristics. Among these are prolymphocytic leukemia (PLL), hairy cell leukemia (HCL) and its variants, large granular lymphocyte leukemia (LGLL) and adult T-cell leukemia/lymphoma (ATLL).

OBJECTIVE

To present current therapies and emerging drugs potentially useful in the treatment of rarer chronic lymphoid leukemias.

METHODS

After searching MEDLINE, PubMed and the Current Contents database, and conference proceedings from the previous 3 years of the American Society of Hematology (ASH), the European Society of Hematology (EHA) and the American Society of Clinical Oncology (ASCO) were searched manually; articles written in English and additional relevant publications were then selected.

RESULTS/CONCLUSION

New drugs including monoclonal antibodies (mAbs), new purine analogs, small molecules targeting specific molecular targets and other agents are included. Future research should focus on the novel therapeutic strategies based on the molecular pathogenic mechanisms and the development of new targeted therapies for each distinct chronic lymphoid leukemia.

Valproic acid sensitizes chronic lymphocytic leukemia cells to apoptosis and restores the balance between pro- and antiapoptotic proteins

Chronic lymphocytic leukemia (CLL) is one of the most common leukemias in adults in the developed world. Despite significant advances in the treatment of cancer, CLL remains incurable. The main feature of the disease is the generation of circulating B-cells with prolonged survival caused by aberrant apoptosis. In this study, we observe that valproic acid (VPA), a well-established histone deacetylase (HDAC) inhibitor, mediates apoptosis in CLL cells ex vivo through caspase activation via both the extrinsic and the intrinsic apoptosis pathways, as indicated by the activation of the caspase proteins 8 and 9, and cleavage of the proapoptotic protein BID. The Bcl-2/Bax ratio was decreased as a consequence of decreased bcl-2 mRNA levels in response to treatment with VPA. With the results presented in this study, we have identified the HDAC inhibitor VPA as restoring the apoptotic pathways in CLL cells and thus their ability to undergo apoptosis.

Lenalidomide for the treatment of B-cell malignancies

Lenalidomide is a novel anticancer agent that has made a major impact in the treatment of patients with B-cell malignancies. A more potent analog of thalidomide, lenalidomide was developed to enhance immunomodulatory properties with improved safety profile. Its antitumor activity seems mediated through modulation of both the cytokine and cellular tumor cell microenvironment. Preclinical as well as clinical observations demonstrate that lenalidomide downregulates production of various critical prosurvival cytokines in the tumor microenvironment while concurrently promoting activation of T- and natural killer (NK) cell-mediated antitumor response. Early clinical investigations noted its efficacy in relapsed and/or refractory multiple myeloma patients. Subsequently, larger randomized studies confirmed the clinical benefit of lenalidomide when added to dexamethasone compared with dexamethasone alone in previously treated myeloma patients resulting in its recent approval by the US Food and Drug Administration. Consequently, the role of lenalidomide in other B-cell malignancies has been investigated, with impressive results in chronic lymphocytic leukemia and non-Hodgkin's lymphoma. This review summarizes the data from various clinical investigations and highlights the impact of lenalidomide in the management of patients with B-cell malignancies.

New treatments for chronic lymphocytic leukemia

An enhanced understanding of the important pathways governing chronic lymphocytic leukemia (CLL) cell survival and the critical role played by the microenvironment in the pathogenesis of the disease has brought new opportunities for drug development in CLL. Several new targets have been identified, and novel agents are under intense investigation in clinical trials. Some of these agents are already demonstrating promising anti-CLL activity on their own, whereas others hold promise in combination with existing therapeutic options. As the use of monoclonal antibodies for chemoimmunotherapy becomes standard clinical practice, the future holds promise for concurrent targeting of the tumor cell as well as its microenvironment.