Small interfering RNAs targeting cyclin D1 and cyclin D2 enhance the cytotoxicity of chemotherapeutic agents in mantle cell lymphoma cell lines

Management of Drug Resistance in Mantle Cell Lymphoma

Mantle cell lymphoma (MCL) is a rare but aggressive B-cell hemopathy characterized by the translocation t(11;14)(q13;q32) that leads to the overexpression of the cell cycle regulatory protein cyclin D1. This translocation is the initial event of the lymphomagenesis, but tumor cells can acquire additional alterations allowing the progression of the disease with a more aggressive phenotype and a tight dependency on microenvironment signaling. To date, the chemotherapeutic-based standard care is largely inefficient and despite the recent advent of different targeted therapies including proteasome inhibitors, immunomodulatory drugs, tyrosine kinase inhibitors, relapses are frequent and are generally related to a dismal prognosis. As a result, MCL remains an incurable disease. In this review, we will present the molecular mechanisms of drug resistance learned from both preclinical and clinical experiences in MCL, detailing the main tumor intrinsic processes and signaling pathways associated to therapeutic drug escape. We will also discuss the possibility to counteract the acquisition of drug refractoriness through the design of more efficient strategies, with an emphasis on the most recent combination approaches.

Somatic alterations of TP53, ERBB2, PIK3CA and CCND1 are associated with chemosensitivity for breast cancers

The correlation of genetic alterations with response to neoadjuvant chemotherapy (NAC) has not been fully revealed. In this study, we enrolled 247 breast cancer patients receiving anthracycline‐taxane‐based NAC treatment. A next generation sequencing (NGS) panel containing 36 hotspot breast cancer‐related genes was used in this study. Two different standards for the extent of pathologic complete response (pCR), ypT0/isypN0 and ypT0/is, were used as indicators for NAC treatment. TP53 mutation (n = 149, 60.3%), PIK3CA mutation (n = 109, 44.1%) and MYC amplification (n = 95, 38.5%) were frequently detected in enrolled cases. TP53 mutation (P = 0.019 for ypT0/isypN0 and P = 0.003 for ypT0/is) and ERBB2 amplification (P < 0.001 for both ypT0/isypN0 and ypT0/is) were related to higher pCR rates. PIK3CA mutation (P = 0.040 for ypT0/isypN0) and CCND2 amplification (P = 0.042 for ypT0/is) showed reduced sensitivity to NAC. Patients with MAPK pathway alteration had low pCR rates (P = 0.043 for ypT0/is). Patients with TP53 mutation (−) PIK3CA mutation (−) ERBB2 amplification (+) CCND1 amplification (−), TP53 mutation (+) PIK3CA mutation (−) ERBB2 amplification (+) CCND1 amplification (−) or TP53 mutation (+) PIK3CA mutation (+) ERBB2 amplification (+) CCND1 amplification (−)had significantly higher pCR rates (P < 0.05 for ypT0/isypN0 and ypT0/is) than wild type genotype tumors. Some cancer genetic alterations as well as pathway alterations were associated with chemosensitivity to NAC treatment. Our study may shed light on the molecular characteristics of breast cancer for prediction of NAC expectations when breast cancer is first diagnosed by biopsy.

Lipid nanoparticle siRNA cocktails for the treatment of mantle cell lymphoma

Mantle cell lymphoma is an aggressive and incurable subtype of non‐Hodgkin B cell lymphoma. Patients typically present with advanced disease, and most patients succumb within a decade of diagnosis. There is a clear and urgent need for novel therapeutic approaches that will affect mantle cell lymphoma through a unique mechanism compared to current therapies. This study examined the use of RNA interference (RNAi) therapy to attack mantle cell lymphoma at the mRNA level, silencing genes associated with cancer cell proliferation. We identified a lipid nanoparticle formulated with the lipidoid 306O₁₃ that delivered siRNA to JeKo‐1 and MAVER‐1 mantle cell lymphoma cell lines. Three therapeutic gene targets were examined for their effect on lymphoma growth. These included Cyclin D1, which is a cell cycle regulator, as well as Bcl‐2 and Mcl‐1, which prevent apoptosis. Gene knockdown with siRNA doses as low at 10 nM increased lymphoma cell apoptosis without carrier‐mediated toxicity. Silencing of Cyclin D1 induced apoptosis despite a twofold “compensation” upregulation of Cyclin D2. Upon simultaneous silencing of all three genes, nearly 75% of JeKo‐1 cells were apoptosing 3 days post‐transfection. Furthermore, cells proliferated at only 15% of their pretreatment rate. These data suggest that lipid nanoparticles‐formulated, multiplexed siRNA “cocktails” may serve as a beneficial addition to the treatment regimens for mantle cell lymphoma and other aggressive cancers.

Protective effect of epigenetic silencing of CyclinD1 against spinal cord injury using bone marrow-derived mesenchymal stem cells in rats

This study focuses on the protective effect of epigenetic silencing of CyclinD1 against spinal cord injury (SCI) using bone marrow-derived mesenchymal stem cells (BMSCs) in rats. Eighty-eight adult female Wistar rats were randomly assigned into the sham group, the control group, the si-CyclinD1 + BMSCs group and the BMSCs group. CyclinD1 protein and mRNA expressions after siRNA transfection were detected by Western blotting and qRT-PCR. The siRNA-CyclinD1 BMSCs were transplanted into rats in the si-CyclinD1 + BMSCs group using stereotaxic method 6 hr after SCI. Hindlimb locomotor performance was determined using inclined plane test and Basso-Beattie-Bresnahan (BBB) locomotor rating scale. Expressions of glial fibrillary acidic protein (GFAP) and nerve growth factor (NGF) were detected by immunohistochemistry. Inclined plane and BBB scores in the control, si-CyclinD1 + BMSCs, and BMSCs groups were significantly lower than the sham group, but these scores were evidently decreased in the control group and increased in the si-CyclinD1 + BMSCs group compared with the BMSCs group. The repair degree of spinal cord tissues of rats in the si-CyclinD1 + BMSCs group was obvious than the BMSCs group. GFAP and NGF protein expressions were markedly decreased in the control, si-CyclinD1 + BMSCs and BMSCs groups when compared with the sham group. GFAP- and NGF-positive cells were significantly increased in the si-CyclinD1 + BMSCs group while decreased in the control group. Our study provides evidence that epigenetic silencing of CyclinD1 using BMSCs might accelerate the repair of SCI in rats.

Cyclin D1 depletion induces DNA damage in mantle cell lymphoma lines

Elevated cyclin D1 (CCND1) expression levels in mantle cell lymphoma (MCL) are associated with aggressive clinical manifestations related to chemoresistance, but little is known about how this important proto-oncogene contributes to the resistance of MCL. Here, we showed that RNA interference-mediated depletion of CCND1 increased caspase-3 activities and induced apoptosis in the human MCL lines UPN-1 and JEKO-1. In vitro and xenotransplant studies revealed that the toxic effect of CCND1 depletion in MCL cells was likely due to increase in histone H2AX phosphorylation, a DNA damage marker. DNA fiber analysis suggested deregulated replication initiation after CCND1 depletion as a potential cause of DNA damage. Finally, in contrast to depletion or inhibition of cyclin-dependent kinase 4, CCND1 depletion increased chemosensitivity of MCL cells to replication inhibitors hydroxyurea and cytarabine. Our findings have an important implication for CCND1 as a potential therapeutic target in MCL patients who are refractory to standard chemotherapy.

New paradigms in mantle cell lymphoma: is it time to risk-stratify treatment based on the proliferative signature?

The elucidation of crucial biologic pathways of cell survival and proliferation has led to the development of highly effective drugs, some of which have markedly improved mantle cell lymphoma (MCL) therapeutic opportunities in the past 10 years. Moreover, an undeniable clinical heterogeneity in treatment response and disease behavior has become apparent in this neoplasm. Thus, the need for biologic markers stratifying patients with MCL in risk classes deserving different treatment approaches has recently been fervently expressed. Among several newly discovered biomarkers, the dismal predictive value of a high proliferative signature has been broadly recognized in large studies of patients with MCL. Different techniques have been used to assess tumor cell proliferation, including mitotic index, immunostaining with Ki-67 antibody, and gene expression profiling. Ki-67 proliferative index, in particular, has been extensively investigated, and its negative impact on relapse incidence and overall survival has been validated in large prospective clinical trials. However, one important pitfall limiting its widespread use in clinical practice is the reported interobserver variability, due to the previous lack of a standardized approach for quantification among different laboratories. In the present review, we describe some of the major techniques to assess cell proliferation in MCL, focusing in particular on the Ki-67 index and its need for a standardized approach to be used in multicenter clinical trials. The value of MCL biologic prognostic scores (as MIPI-b) is discussed, along with our proposal on how to integrate these scores in the planning of future trials investigating a tailored therapeutic approach for patients with MCL. See all articles in this CCR Focus section, "Paradigm Shifts in Lymphoma."

No evidence of cell cycle dysregulation in mantle cell lymphoma in vivo

Mantle cell lymphoma (MCL) is characterized by the translocation t(11;14)(q13;q32) leading to an overexpression of cyclin D1, a mediator of G1-S phase transition. Thus MCL is regarded as a paradigm of lymphoma with a dysregulated cell cycle. The proliferation rate of MCL is in fact a strong predictor of outcome. We analyzed proteins that are expressed at defined cell cycle phases, such as Ki67, survivin and phosphorylated histone H3 as well as cyclin D1, p53 and p27, on the cellular level by immunofluorescence double stainings in MCL biopsy specimens. Unexpectedly, we did not detect a shortening of early phases in MCL in vivo. Despite the control of the immunoglobulin enhancer, cyclin D1 was expressed in a cell cycle-dependent manner. However, the proliferating Ki67-positive tumor cells expressed low amounts of cyclin D1. Therefore, the expression of cyclin D1 appears not to be the driving factor behind the total proliferation rate of MCL.

Expression of cyclin A, B1 and D1 after induction of cell cycle arrest in the Jurkat cell line exposed to doxorubicin

Jurkat human lymphoblastoid cells were incubated in increasing concentrations of doxorubicin (0.05, 0.1 and 0.15 μM) to induce cell death, and their expression of cyclin A, B1 and D1 was evaluated by flow cytometry (cell cycle progression, Annexin V assay, percentages and levels of each of the cyclins), transmission electron microscopy (ultrastructure) and confocal fluorescence microscopy (expression and intracellular localization of cyclins). After low-dose doxorubicin treatment, Jurkat cells responded mainly by G2/M arrest, which was related to increased cyclin B1, A and D1 levels, a low level of apoptosis and/or mitotic catastrophe. The influence of doxorubicin on levels and/or localization of selected cyclins was confirmed, which may in turn contribute to the G2/M arrest induced by the drug.

Dual functional BAFF receptor aptamers inhibit ligand-induced proliferation and deliver siRNAs to NHL cells

The B-cell–activating factor (BAFF)-receptor (BAFF-R) is restrictedly expressed on B-cells and is often overexpressed in B-cell malignancies, such as non-Hodgkin’s lymphoma. On binding to its ligand BAFF, proliferation and cell survival are increased, enabling cancer cells to proliferate faster than normal B-cells. Nucleic acid aptamers can bind to target ligands with high specificity and affinity and may offer therapeutic advantages over antibody-based approaches. In this study, we isolated several 2′-F–modified RNA aptamers targeting the B-cell–specific BAFF-R with nanomolar affinity using in vitro SELEX technology. The aptamers efficiently bound to BAFF-R on the surface of B-cells, blocked BAFF-mediated B-cell proliferation and were internalized into B-cells. Furthermore, chimeric molecules between the BAFF-R aptamer and small interfering RNAs (siRNAs) were specifically delivered to BAFF-R expressing cells with a similar efficiency as the aptamer alone. We demonstrate that a signal transducer and activator of transcription 3 (STAT3) siRNA delivered by the BAFF-R aptamer was processed by Dicer and efficiently reduced levels of target mRNA and protein in Jeko-1 and Z138 human B-cell lines. Collectively, our results demonstrate that the dual-functional BAFF-R aptamer–siRNA conjugates are able to deliver siRNAs and block ligand mediated processes, suggesting it might be a promising combinatorial therapeutic agent for B-cell malignancies.

RNA inhibition highlights cyclin D1 as a potential therapeutic target for mantle cell lymphoma

Mantle cell lymphoma is characterized by a genetic translocation results in aberrant overexpression of the CCND1 gene, which encodes cyclin D1. This protein functions as a regulator of the cell cycle progression, hence is considered to play an important role in the pathogenesis of the disease. In this study, we used RNA interference strategies to examine whether cyclin D1 might serve as a therapeutic target for mantle cell lymphoma. Knocking down cyclin D1 resulted in significant growth retardation, cell cycle arrest, and most importantly, induction of apoptosis. These results mark cyclin D1 as a target for mantle cell lymphoma and emphasize the therapeutic potential hidden in its silencing.