Correlation of ZAP-70 expression in B cell leukemias to the ex vivo response to a combination of fludarabine/genistein

Effects of Chronic Dietary Exposure to Phytoestrogen Genistein on Uterine Morphology in Mice

Genistein is naturally occurring in plants and binds to estrogen receptors. Humans are mainly exposed through diet, but the use of supplements is increasing as genistein is claimed to promote health and alleviate menopausal symptoms. We analyzed diverse uterine features in adult mice chronically fed genistein for different times. The luminal epithelium height was increased in females treated with 500 and 1000 ppm at PND 95, and the width of the outer myometrium was increased in females treated with 1000 ppm at PND 65 compared to that in controls. An increase in proliferation was noted in the inner myometrium layer of animals exposed to 300 ppm genistein at PND 185 compared to that in controls. Luminal hyperplasia was greater in the 1000 ppm group at PND 65, 95, and 185, although not statistically different from control. These results indicate that genistein may exert estrogenic activity in the uterus, without persistent harm to the organ.

Potentiation of luteolin cytotoxicity by flavonols fisetin and quercetin in human chronic lymphocytic leukemia cell lines

Despite numerous studies chronic lymphocytic leukemia (CLL) still remains an incurable disease. Therefore, all new compounds and novel strategies which are able to eradicate CLL cells should be considered as valuable clues for a potential future remedy against this malignancy. In the present study, the cytotoxic profiles of natural flavonoids were described in two human CLL cell lines, HG-3 and EHEB, indicating the flavone luteolin as the most potent flavonoid with half-maximal inhibitory constants (IC50) of 37 μM and 26 μM, respectively. Luteolin significantly increased the apoptotic cell population in both cell lines by increasing the activities of caspases-3 and -9 and triggering the intrinsic apoptotic pathway. Two flavonols, fisetin and quercetin, were somewhat less efficient in suppressing cellular viability, whereas baicalein, chrysin, (+)-catechin and hesperetin exerted only a small or no response at doses as high as 100 μM. Both fisetin and quercetin were able to augment the cytotoxic activity of luteolin in both cell lines by reducing the IC50 values up to four fold. As a result of this, luteolin displayed cytotoxicity activity already at low micromolar concentrations that could potentially be physiologically achievable through oral ingestion. No other tested flavonoids were capable of sensitizing CLL cells to luteolin pointing to a specific binding of fisetin and quercetin to the cellular targets which interfere with the signaling pathways induced by luteolin. Although further molecular studies to unravel this potentiating mechanism are certainly needed, this phenomenon could contribute to future remedies for prevention and treatment of chronic lymphocytic leukemia.

Understanding genistein in cancer: The "good" and the "bad" effects: A review

Nowadays, diet and specific dietary supplements are seen as potential adjuvants to prevent different chronic diseases, including cancer, or to ameliorate pharmacological therapies. Soybean is one of the most important food components in Asian diet. A plethora of evidence supports the in vitro and in vivo anticancer effects of genistein, a soybean isoflavone. Major tumors affected by genistein here reviewed are breast, prostate, colon, liver, ovarian, bladder, gastric, brain cancers, neuroblastoma and chronic lymphocytic leukemia. However, it is not always clear if and when genistein is beneficial against tumors (the "good" effects), or the opposite, when the same molecule exerts adverse effects (the "bad" effects), favouring cancer cell proliferation. This review will critically evaluate this concept in the light of the different molecular mechanisms of genistein which occur when the molecule is administered at low doses (chemopreventive effects), or at high doses (pharmacological effects).

Quercetin downregulates Mcl-1 by acting on mRNA stability and protein degradation

Background:

We recently demonstrated that quercetin, a flavonoid naturally present in food and beverages belonging to the large class of phytochemicals, was able to sensitise leukaemic cells isolated from patients with chronic lymphocytic leukaemia (CLL) when associated with recombinant tumour necrosis factor-related apoptosis-inducing ligand (TRAIL) or anti-CD95. We also showed that quercetin potentiated the effect of fludarabine on resistant B cells from CLL patients. Resistance to therapy in CLL depends on the expression and activity of anti-apoptotic proteins of the Bcl-2 family. Among these, myeloid cell leukaemia-1 (Mcl-1) has been associated with apoptotic resistance in CLL. Therefore, we investigate here whether the sensitising activity of this flavonoid, which leads to increased apoptosis in both cell lines and CLL, could be related to Mcl-1 expression and stability.

Results:

B cells isolated from CLL patients showed different levels of Mcl-1 protein expression, resulting, in several cases, in increased sensitivity to fludarabine. Quercetin significantly enhanced the downregulation of Mcl-1 in B cells isolated from selected patients expressing detectable levels of Mcl-1. In U-937 cells, quercetin increased Mcl-1 mRNA instability in the presence of actinomycin D. When cells were treated with MG-132, a proteasome inhibitor, Mcl-1 protein level increased. However, quercetin, in the presence of Z-Vad-FMK, continued to lower Mcl-1 protein expression, indicating its independence from caspase-mediated degradation. In contrast, co-treatment of quercetin and MG-132 did not revert the effect of MG-132 mono-treatment, thus suggesting a possible interference of quercetin in regulating the proteasome-dependent degradation of Mcl-1. Gossypol, a small-molecule inhibitor of Bcl-2 family members, mimics the activity of quercetin by lowering Mcl-1 expression and sensitising U-937 cells to apoptosis induced by recombinant TRAIL and the Fas-ligand.

Conclusion:

This study demonstrates that in U-937 cells, quercetin downregulates Mcl-1 acting directly or indirectly on its mRNA stability and protein degradation, suggesting that the same mechanism may bypass resistance to apoptosis in leukaemic cells isolated from CLL patients and sensitise B cells to apoptosis induced by drugs and death receptor inducers.

Quercetin induced apoptosis in association with death receptors and fludarabine in cells isolated from chronic lymphocytic leukaemia patients

Background:

Quercetin is a flavonoid naturally present in food and beverages belonging to the large class of phytochemicals with potential anti-cancer properties. Here, we investigated the ability of quercetin to sensitise primary cells from chronic lymphocytic leukaemia (CLL) to death receptor (DR) agonists, recombinant TNF-related-apoptosis-inducing ligand (rTRAIL) and anti-CD95, and to fludarabine, a widely used chemotherapeutic drug against CLL.

Methods:

Peripheral white blood cells were isolated from patients and incubated with medium containing 50 ng ml anti-CD95 agonist antibody; 10 ng ml recombinant TRAIL; 10–25 μM quercetin and 3.5–14 μM fludarabine. Neutral Red assay was used to measure cell viability, where as apoptosis was assessed by determining caspase-3 activity, exposure to Annexin V and PARP fragmentation.

Results:

Quercetin significantly enhanced anti-CD95- and rTRAIL-induced cell death as shown by decreased cell viability, increased caspase-3 and -9 activities, and positivity to Annexin V. In addition, association of quercetin with fludarabine increases the apoptotic response in CLL cells of about two-fold compared with quercetin monotreatment.

Conclusion:

This work shows that resistance to DR- and fludarabine-induced cell death in leukaemic cells isolated from CLL patients can be ameliorated or bypassed by the combined treatment with quercetin. Considering the low toxicity of the molecule, our study results are in favour of a potential use of quercetin in adjuvant chemotherapy in combination with other drugs.

Spleen tyrosine kinase is overexpressed and represents a potential therapeutic target in chronic lymphocytic leukemia

B-cell receptor signaling contributes to apoptosis resistance in chronic lymphocytic leukemia (CLL), limiting the efficacy of current therapeutic approaches. In this study, we investigated the expression of spleen tyrosine kinase (SYK), a key component of the B-cell receptor signaling pathway, in CLL and its role in apoptosis. Gene expression profiling identified enhanced expression of SYK and downstream pathways in CLL compared with healthy B cells. Immunoblotting showed increased expression and phosphorylation of SYK, PLCgamma(2), signal transducers and activators of transcription 3, and extracellular signal regulated kinase 1/2 in CLL compared with healthy B cells, suggesting enhanced activation of these mediators in CLL. SYK inhibitors reduced phosphorylation of SYK downstream targets and induced apoptosis in primary CLL cells. With respect to prognostic factors, SYK inhibitors exerted stronger cytotoxic effects in unmutated and ZAP70(+) cases. Cytotoxic effects of SYK inhibitors also associated with SYK protein expression, potentially predicting response to therapy. Combination of fludarabine with SYK Inhibitor II or R406 increased cytotoxicity compared with fludarabine therapy alone. We observed no stroma-contact-mediated drug resistance for SYK inhibitors as described for fludarabine treatment. CD40 ligation further enhanced efficacy of SYK inhibition. Our data provide mechanistic insight into the recently observed therapeutic effects of the SYK inhibitor R406 in CLL. Combination of SYK inhibitors with fludarabine might be a novel treatment option particularly for CLL patients with poor prognosis and should be further evaluated in clinical trials.

Molecular and cellular mechanisms of CLL: novel therapeutic approaches

The mainstay of therapy of chronic lymphocytic leukemia (CLL) is cytotoxic chemotherapy; however, CLL is still an incurable disease with resistance to therapy developing in the majority of patients. In recent years, our understanding of the biological basis of CLL pathogenesis has substantially improved and novel treatment strategies are emerging. Tailoring and individualizing therapy according to the molecular and cellular biology of the disease is on the horizon, and advances with targeted agents such as monoclonal antibodies combined with traditional chemotherapy have lead to improved remission rates. The proposed key role of the B-cell receptor (BCR) in CLL pathogenesis has led to a number of possible opportunities for therapeutic exploitation. We are beginning to understand that the microenvironment is of utmost importance in CLL because certain T-cell subsets and stromal cells support the outgrowth and development of the malignant clone. Furthermore, an increase in our understanding of the deregulated cell-death machinery in CLL is a prerequisite to developing new targeted strategies that might be more effective in engaging with the cell-death machinery. This Review summarizes the progress made in understanding these features of CLL biology and describes novel treatment strategies that have also been exploited in current clinical trials.

The kinase inhibitor dasatinib induces apoptosis in chronic lymphocytic leukemia cells in vitro with preference for a subgroup of patients with unmutated IgVH genes

Src family kinases (SFKs) were described to be overexpressed in chronic lymphocytic leukemia (CLL). We wished to examine the effects of the Src and Abl kinase inhibitor dasatinib on the intracellular signaling and survival of CLL cells. Dasa-tinib showed a dose- and time-dependent reduction of global tyrosine phosphorylation and of activating phosphotyrosine levels of SFKs. Treatment with 100 nM dasatinib led to decreased levels of the activated, phosphorylated forms of Akt, Erk1/2, and p38, and induced PARP cleavage through caspase activity. In Mec1 and JVM-3 cell lines, dasatinib increased p53 protein levels and inhibited proliferation. In freshly isolated CLL cells, dasatinib reduced the expression of Mcl-1 and Bcl-x(L). Combination of 5 microM dasatinib and fludarabine increased the apoptosis induction of each by approximately 50%. In 15 primary CLL samples, cells with unmutated immunoglobulin variable heavy chain (IgV(H)) genes were more sensitive to dasatinib than those with mutated IgV(H) genes (P = .002). In summary, dasatinib shows potent inhibitory effects on the survival of CLL cells in vitro, most prominently in samples obtained from patients with unfavorable prognostic features.