Sugar-coated signaling in follicular lymphoma.

In this issue of Blood, complementary studies by Amin et al and Linley et al demonstrate that sugar moieties linked to surface immunoglobulin (sIg) of follicular lymphoma (FL) cells directly interact with endogenous lectins within the lymphoma niche and lead to activation of downstream B-cell receptor (BCR) signaling pathways. In addition to providing further insight into the role of the microenvironment in lymphomagenesis, these findings expose a unique molecular interaction that may represent a viable target for therapeutic intervention.

PLK1 and YY1 interaction in follicular lymphoma is associated with unfavourable outcome.

AIMS: Ying Yang 1 (YY1) is a transcription factor involved in both proliferation and apoptosis. It is prognostic in follicular lymphoma (FL), increased protein levels being associated with favourable outcome. PLK1 is a critical regulator of mitosis, playing a role in spindle formation and in regulation of the G2/M cell cycle checkpoint. PLK1 phosphorylates YY1 at the G2/M checkpoint with activation of YY1 and resultant progression from G2 into mitosis. METHODS: This study aims to investigate possible molecular coexpression and interaction of YY1 with PLK1 in FL using Duolink II in situ proximity ligation assay (PLA) in 51 FL samples in a tissue microarray. RESULTS: Positive PLA signals were present at variable frequency and Kaplan-Meier analysis showed association of signal frequency above the median with unfavourable outcome (p=0.0270). PLA signals were localised to the nuclear edge, with only one signal per cell, suggesting PLK1 and YY1 coexpression at the centrosome. In a minority of cells, two very close PLA signals were present in a single cell, and occasionally, there was a strong ring of semi-confluent fluorescent PLA signals round the nucleus of non-dividing cells, while rarely events were observed in the cytoplasm surrounding dividing cells. CONCLUSIONS: The results confirm association of YY1 and PLK1 with outcome in FL and suggest coexpression at the centrosome. Given the reported interaction of YY1 with PLK1 at the centriole and promotion of cell division at the G2/M checkpoint, the results would concord with the known association of higher proliferation with poor outcome in FL.

Distinct cellular and therapeutic effects of obatoclax in rituximab-sensitive and -resistant lymphomas.

Bcl-2 proteins represent a rheostat that controls cellular viability. Obatoclax, a BH3-mimetic, has been designed to specifically target and counteract anti-apoptotic Bcl-2 proteins. We evaluated the biological effects of obatoclax on the anti-tumour activity of rituximab and chemotherapy agents. Obatoclax induced cell death of rituximab/chemotherapy-sensitive (RSCL), -resistant cell lines (RRCL) and primary tumour-cells derived from patients with B-cell lymphomas (N=39). Obatoclax also enhanced the activity of rituximab and had synergistic activity when combined with chemotherapy agents. The ability of Obatoclax to induce PARP cleavage varied between patient samples and was not observed in some RRCL. Inhibition of caspase activity did not affect obatoclax activity, suggesting the existence of caspase-independent death pathways. Autophagy was detected by LC3 conversion and/or electron microscopy in RRCL and in patient-derived tumour cells. Moreover, obatoclax activity was inhibited by Beclin-1 knockdown. In summary, obatoclax is an active Bcl-2 inhibitor that potentiates the activity of chemotherapy agents and, to a lesser degree, rituximab. Defining the molecular events triggered by obatoclax is necessary to further its clinical development and identify potential biomarkers that are predictive of response.

YY1 expression predicts favourable outcome in follicular lymphoma.

AIMS: Follicular lymphoma is the second most common type of non-Hodgkin's lymphoma worldwide. The majority of patients diagnosed as having follicular lymphoma have an indolent form of the disease, but a subset of patients have aggressive disease with a shorter survival interval. Optimal treatment stratification requires a distinction between these two groups, though there are presently few prognostic biomarkers available. The transcription factor YY1 has been shown to play an important role in cancer biology. The authors have previously reported a correlation of Yin Yang 1 (YY1) mRNA levels with survival in FL. This study aimed to validate these findings at the protein level. METHODS: Quantification of YY1 protein was carried out on 26 FL biopsy samples using quantum dot labelled immunohistochemistry. Ki-67 percentage, grade, YY1 protein levels and T cell and macrophage markers were used in a multivariable analysis for survival in 26 cases of FL. RESULTS: Expression levels of YY1 protein were significantly increased in patients alive in comparison with those dead after follow-up (p ≤ 0.025). Kaplan-Meier analysis showed association of higher expression levels of YY1 with longer survival (p ≤ 0.01) (hazard ratio 3.33, 95% CI 1.26 to 8.85). The multivariable analysis identified YY1 protein level as the strongest predictor of outcome (p ≤ 0.018), with none of the other markers being significantly associated with outcome. CONCLUSION: These results support the prognostic utility of YY1 in FL, indicating potential as a clinical biomarker.

Cellular foundation of curcumin-induced apoptosis in follicular lymphoma cell lines.

OBJECTIVE: Although responsive to first-line treatments, follicular lymphoma (FL) remains a fatal disease of increasing worldwide incidence. In efforts to find novel approaches to inhibit proliferation and induce apoptosis in FL cells, we examined the action of naturally occurring compound curcumin in the three recently established FL cell lines. MATERIALS AND METHODS: Cytotoxic effects and determination of apoptotic attributes upon curcumin treatment were analyzed using growth inhibition, [(3)H]-thymidine, fluorescence microscopy, and flow cytometry assays, as well as Western blotting. Chemical inhibitor studies for the assessment of caspase and cathepsin contribution were applied. Expression of 10 members of the bcl-2 family proteins was evaluated by immunoblotting. RESULTS: Curcumin inhibited proliferation and growth, and induced profound apoptosis associated with a shift in the balance of the bcl-2 family proteins, in all cell lines tested. Strikingly, we observed that curcumin-induced caspase-dependent apoptosis is also associated with lysosomal rupture (LMP). An increase in intracellular ROS generation appeared critical for curcumin-evoked LMP, loss of Deltapsi(m,) caspase activation, and cell death, as well as ascorbic acid-mediated enhancement of curcumin's action. CONCLUSION: We have demonstrated for the first time that curcumin is an efficient inducer of apoptosis in FL cell lines, meriting its further evaluation in vivo.

HA14-1, a small molecule Bcl-2 antagonist, induces apoptosis and modulates action of selected anticancer drugs in follicular lymphoma B cells.

The BCL-2 overexpression is a hallmark of follicular lymphoma (FL). Since patients with FL often suffer from resistant to chemotherapy refractory disease, the development of new regimens is required. Herein, we analyze for the first time the effects of a B-cell lymphoma 2 (Bcl-2) antagonist, HA14-1, alone and in combination with antineoplastic agents commonly used against follicular lymphoma, in human FL cell lines with t(14;18). All cell lines tested were sensitive to HA14-1-induced cytotoxicity and apoptosis, as depicted by morphological changes, SYTO16/PI staining, oligonucleosomal DNA fragmentation and loss of Deltapsi(m). Moreover, HA14-1 significantly enhanced dexamethasone- and doxorubicin-mediated (in schedule independent and dependent manner, respectively), but not vincristine-mediated cytotoxicity and apoptosis.