Chronic lymphocytic leukemia

A Novel Natural Product, KL-21, Inhibits Proliferation and Induces Apoptosis in Chronic Lymphocytic Leukemia Cells

Objective:

The aims of this study were to examine the cytotoxic and apoptotic effects of KL-21, a novel plant product (produced by Naturin Natural Products, İzmir, Turkey), on 232B4 chronic lymphocytic leukemia (CLL) cells and to determine the cytotoxic effects on healthy BEAS-2B human bronchial epithelial cells.

Materials and Methods:

The cytotoxic effect of KL-21 was determined by MTT cell proliferation assay. Changes in caspase-3 enzyme activity were measured using the caspase-3 colorimetric assay. Changes in mitochondrial membrane potential were determined using the JC-1 dye-based method. Annexin V-FITC/PI double staining was performed to measure the apoptotic cell population. Effects of KL-21 on cell cycle profiles of CLL cells were investigated by flow cytometry.

Results:

We detected time- and concentration-dependent increases in the cytotoxic effect of KL-21 on 232B4 CLL cells. However, we also showed that, especially at higher concentrations, KL-21 was less cytotoxic towards BEAS-2B healthy cells than towards CLL cells. Annexin-V/PI double staining results showed that the apoptotic cell population increased in 232B4 cells. Increasing concentrations of KL-21 increased caspase-3 enzyme activity and induced loss of mitochondrial membrane potential. KL-21 administration resulted in small increases in the percentage of the cells in the G0/G1 phase while it decreased the S phase cell population up to 1 mg/mL. At the highest concentration, most of the cells accumulated in the G0/G1 phase.

Conclusion:

KL-21 has a growth-inhibitory effect on 232B4 CLL cells. KL-21 causes apoptosis and cell cycle arrest at G0/G1.

Role of immunochemotherapy in the treatment of chronic lymphocytic leukemia

Major advances have been made in our understanding of the biology and opportunities for treatment of chronic lymphocytic leukemia in recent times. Newer treatment regimens incorporating purine nucleoside analogs have increased the rate of successful remission induction in chronic lymphocytic leukemia patients. Moreover, recent combination chemoimmunotherapy regimens have produced more frequent complete molecular remissions, and early evidence seems to suggest that this could result in prolonged duration of responses, although this association remains to be clearly demonstrated. This review will summarize recent advances in the biology and the management of chronic lymphocytic leukemia, including prognostic factors, pointing mainly on combination chemotherapy based on nucleoside analogs and monoclonal antibodies. In our opinion, in the future a significant improvement of clinical benefits in chronic lymphocytic leukemia will be obtained through the administration of cocktails of monoclonal antibodies combined with chemotherapy in different modalities.

Pentostatin for the Treatment of Indolent Lymphoproliferative Disorders

Purine analogues have been shown to be active in a variety of B- and T-cell malignancies. Among them, pentostatin is also a tight binding inhibitor of adenosine deaminase (ADA), a key enzyme of purine metabolism. ADA is present in all human tissues, with the highest levels in the lymphoid system. Early clinical trials with pentostatin used high doses for acute lymphoblastic leukemias, which were characterized by high levels of ADA. Through the efforts of a few investigators, low-dose regimens that are active and well tolerated for indolent lymphoid malignancies have been developed. Myelosuppressive adverse effects have been shown to be minimal using these schedules. Lymphoplasmacytic lymphoma (LL) is an indolent chronic B-cell lymphoproliferative disorder moderately responsive to alkylating agents. All of the purine analogues have shown activity in LL. However, the advantage of pentostatin over the other agents is the relatively specific toxicity to lymphoid cells and the paucity of myelosuppression as a single agent. No direct comparisons of the agents have been investigated, although pentostatin may be considered to be preferred since it has not been associated with toxicity to myeloid progenitors in colony assays. This is of significance for patients who might benefit from high-dose chemotherapy with autologous stem cell transplantation.

Pentostatin and purine analogs for indolent lymphoid malignancies

Pentostatin has been shown to be active in a variety of B- and T-cell malignancies. The drug is a tight inhibitor of adenosine deaminase, a key degradative enzyme of purine metabolism present in all human tissues, with the highest levels found in the lymphoid system. Early clinical trials indicated that this agent was highly active in acute lymphoblastic leukemias with high intracellular adenosine deaminase levels. Relatively high doses of the drug were needed, which was associated with severe adverse events. Through the efforts of a few investigators, better tolerated, low-dose regimens have been shown to be extremely active in lymphoproliferative diseases with very low intracellular adenosine deaminase levels such as hairy cell leukemia, B- and T-cell chronic leukemias, T-cell cutaneous lymphomas and low-grade non-Hodgkin lymphomas. Clinical as well as experimental data have indicated that this drug induces lymphocyte-specific cytotoxicity, and myelosuppressive adverse events have been minimal. Although all the purine analogs have shown similar activity, the advantage of pentostatin is the relatively specific cytotoxicity against lymphocytes, which permits treatment even in patients with severe cytopenias. Although no direct comparisons of the purine analogs have been performed, pentostatin may be preferred due to this property.

Alkylating agents and nucleoside analogues in the treatment of B cell chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) is the most common form of leukemia in the Western world. The natural clinical course is highly variable and chemotherapy is usually not indicated in early and stable disease. Treatment is needed in the progressive form of this leukemia. Chlorambucil, with or without steroids, has been for many years the drug of choice in the treatment of CLL. More recently, treatment approaches have included nucleoside analogues, (NA) fludarabine (FAMP) and cladribine (2-CdA, 2-chlorodeoxyadenosine), which seem to be the treatment of choice for patients failing standard therapies. Their role as first line therapy is being investigated in randomized trials and the results have recently been published. These studies have shown a higher overall response and complete remission (CR) rate and longer response duration in patients treated initially with NA than with chlorambucil or cyclophosphamide-based combination regimens. In contrast, overall survival is similar in patients treated with NA and alkylating agents. However, the randomized trials were designed as crossover studies which may influence survival. Combined use of NA with other cytotoxic drugs, cytokines, monoclonal antibodies and other agents may increase the CR and prolong survival time. However, the results of randomized trials comparing combination treatment with NA alone are not yet available. In conclusion, alkylating agents still have an important place in the routine management of the majority of CLL patients. NA should be routinely used as second line treatment and possibly as first line therapy in younger patients, who are candidates for potentially curative treatment such as stem cell transplantation and/or monoclonal antibodies.

Leptomeningeal involvement in chronic lymphocytic leukemia

PURPOSE

This review and case report address the rare complication of leptomeningeal involvement in patients with chronic lymphocytic leukemia.

OVERVIEW

Chronic lymphocytic leukemia is the most common form of leukemia, with more than 200,000 cases reported in the past 20 years. An uncommon complication of the disorder is central nervous system invasion. To date, only 21 cases have been reported, and their presenting symptoms have been heterogeneous and often nonspecific, including headache, cranial nerve abnormalities, confusion, ataxia, nausea, vomiting, and fever. The diagnosis is confirmed by the presence of a clonal population of lymphocytes in the cerebrospinal fluid. Treatment is either intrathecal or intraventricular chemotherapy with adjuvant radiation therapy or radiation alone. Prognosis is improved by prompt and aggressive therapy. In this case report, a 61-year-old man developed severe ataxia, vertigo, and occipital headaches 4 weeks after diagnosis with otherwise asymptomatic chronic lymphocytic leukemia. After treatment with both radiation to the head and neck and intrathecal methotrexate the patient achieved complete symptom resolution. Thus far, no additional systemic cytotoxic chemotherapy has been necessary.

CLINICAL IMPLICATIONS

Because central nervous system invasion is uncommon in chronic lymphocytic leukemia, it may go undiagnosed and under-reported. Providers of patients with this disease need to be aware of possible central nervous system invasion when patients present with cranial nerve signs or symptoms and/or nonspecific neurologic manifestations. Early identification and prompt central nervous system-directed chemotherapy can affect morbidity and quality of life positively.