Mantle cell lymphoma: therapeutic strategies are different from CLL

Parallel gene expression profiling of mantle cell lymphoma - how do we transform 'omics data into clinical practice

DNA microarray technology has been a valuable tool to provide a global view of the changes in gene expression that characterize different types of B cell lymphomas, both in relation to clinical parameters but also in comparison with the non-malignant counterparts. The number of transcripts that can be analyzed on an array has dramatically increased, and now most commercially available arrays cover the whole genome, enabling overall analysis of the transcriptome.The backside of collecting this massive amount of information is that even after strict data filtering, it is impossible to do follow-up studies on all findings. Down-stream analysis is time-consuming and when performing confirmatory experiments on the protein level, the experiments are in most cases restricted to proteins recognized by commercially available reagents. Furthermore, since gene expression data is a comparative method not only are the experimental set-up but also the characteristics of both the sample and reference crucial for our ability to answer the questions posed. Thus, initial care must be taken in the design of the experiment and the preparation of the samples.The aim of this review is to discuss the progress in mantle cell lymphoma research enabled by gene expression analysis and to pinpoint the difficulties in making efficient use of the generated data to provide a fast and accurate clinical diagnosis, efficient stratification of patients into disease sub-groups and improved therapy.

[Therapy of mantle cell lymphoma]

Mantle cell lymphoma (MCL) belongs to the so-called peripheral (differentiated) B cell non-Hodgkin lymphomas. In spite of that, it runs an aggressive course; quick progression and most cases are diagnosed in advanced stages. On the other hand, chemotherapy and immunochemotherapy (in contrast with other aggressive lymphomas) are not able to show any curative potential. However, combined efforts of first line antiCD20 based intensified immunochemotherapy along with high dose therapy (preferably irradiation based conditioning regimens) and autologous transplant consolidation of first complete remission achieves major breakthrough and prolongation of life expectancies of 7-10 years instead of the 2.5-3 years average survival of the traditional chemotherapeutic approach. A lot of new agents (i.e. the FDA approved MCL indication of bortezomib, temsirolimus, thalidomide, etc.) are or should be available for the refractory or relapsed patients. This short review summarizes the most important advances of MCL therapy and provides an updated therapeutic recommendation.

Phase II Study of Yttrium-90–Ibritumomab Tiuxetan in Patients With Relapsed or Refractory Mantle Cell Lymphoma

Purpose

This phase II trial evaluated the safety and efficacy of yttrium-90 (90Y)–ibritumomab tiuxetan in patients with relapsed or refractory mantle cell lymphoma (MCL).

Patients and Methods

Patients with relapsed or refractory MCL were eligible for the study if they had adequate major organ function and performance status. Those with CNS disease, pleural effusion, circulating lymphoma cells ≥ 5,000/μL, or history of stem-cell transplant were ineligible. Patients with a platelet count ≥ 150,000/μL received a dose of 0.4 mCi/kg of90Y–ibritumomab tiuxetan, whereas those with a platelet count less than 150,000/μL received a dose of 0.3 mCi/kg.

Results

Thirty-four patients with a median age of 68 years (range, 52 to 79 years) received the therapeutic dose. The patients had received a median of three prior treatment regimens (range, one to six treatment regimens), including those that contained rituximab (n = 32) and bortezomib (n = 7). Of the 32 patients with measurable disease, 10 (31%) achieved complete or partial remission. After a median follow-up of 22 months (range, 2 to 72+ months), an intent-to-treat analysis revealed a median event-free survival (EFS) duration of 6 months and an overall survival duration of 21 months. The median EFS for those who achieved partial or complete remission was 28 months, while it was 3 months for those whose disease did not respond (P < .0001); it was 9 months for patients whose tumor measured less than 5 cm in the largest diameter before treatment and 3 months for those whose tumor measured ≥ 5 cm (P = .015).

Conclusion

The single-agent activity of90Y–ibritumomab tiuxetan and its favorable safety profile warrant its further development for the treatment of MCL.

The epigenetics of mantle cell lymphoma

There is no consensus treatment for newly diagnosed mantle cell lymphoma. The CHOP + rituximab and hyperCVAD + rituximab regimens are most commonly used. The former is limited by relatively lower rates of complete remission (CR) and frequent relapses. The latter is limited by toxicities, especially in older patients, and relapses that occur later than those usually seen with CHOP + rituximab. Thus, improved therapies are needed. The purine analog cladribine (2-cda) + rituximab has been studied as an alternative frontline regimen in MCL and is quite active with minimal toxicity. Cladribine has epigenetic activity in that it inhibits DNA methylation. Cladribine + rituximab should be further studied in newly diagnosed mantle cell lymphoma in combination with new agents such as inhibitors of histone deacetylation, the mTOR pathway, and the proteasome.

Proteasome inhibition with bortezomib: a new therapeutic strategy for non-Hodgkin's lymphoma

The incidence of non-Hodgkin's lymphoma (NHL) has markedly increased in the US and other westernized countries in recent years and presents a considerable clinical challenge. NHL is divided into subtypes that follow an aggressive or indolent course. Follicular lymphoma (FL), the most common indolent subtype, and mantle cell lymphoma (MCL), an aggressive subtype that accounts for approximately 5% of cases, are generally incurable. MCL has a relatively poor prognosis, with a median survival of 3-4 years. Despite improving response rates with new agents and regimens, the lack of demonstrated improvement in overall survival in many subtypes supports the development of novel approaches, such as proteasome inhibition. Bortezomib is the first proteasome inhibitor to be evaluated in human studies. It has already been approved as second-line treatment in multiple myeloma and is now under active investigation in NHL. The US FDA has granted bortezomib fast-track designation for relapsed and refractory MCL. In vitro and in vivo studies have demonstrated single-agent activity against various lymphoid tumors, and additive or synergistic effects in combination with other agents, including standard chemotherapy drugs employed in NHL. Phase 2 clinical trials indicate that bortezomib is well tolerated and active in several NHL subtypes, with response rates of 18-60% in FL and 39-56% in MCL. A number of combination trials are currently underway with a range of standard agents. Bortezomib has the potential to play a significant role throughout the NHL treatment algorithm in the future.

Induction of apoptosis and down regulation of cell cycle proteins in mantle cell lymphoma by flavopiridol treatment

Typical mantle cell lymphoma (MCL) is a distinct B-cell non-Hodgkin's lymphoma associated with over-expression of cyclin D1 related to translocation between the IgH and BCL-1 genes. Due to the important functional interaction between cyclin D1 and cyclin dependent kinases, cyclin dependent kinase inhibitors such as flavopiridol are under consideration for treatment of patients with MCL. The present study investigated the in vitro effects of flavopiridol on the MCL cell line (JeKo-1). Flavopiridol at a dose of 10nmol/L induced apoptosis by 6h of treatment as noted by flow cytometric analysis, morphologic examination and Western blotting. The cleavage of procaspase-3 and PARP and the decrease of flavopiridol-induced apoptosis by pan-caspase inhibition suggested that the caspase pathway serves an important role in the apoptotic process. Furthermore, MCL cells exposed to flavopiridol showed down regulation of key cell cycle proteins acting at the restriction point control between the G1 and S phases. The onset of flavopiridol-induced apoptosis also coincided with the down regulation of Mcl-1, anti-apoptotic protein. Collectively, our data indicates that flavopiridol may have significant therapeutic potential in the context of MCL.

Recent progress in the discovery and development of cyclin-dependent kinase inhibitors

Cyclin-dependent kinases (CDKs) have long been known to be the main facilitators of the cell proliferation cycle. However, they also play important roles in the regulation of the RNA polymerase II transcription cycle. Cancer cells display aberrant cell cycle regulation to gain proliferative advantages and they also appear to have an exaggerated dependence on RNA polymerase II transcriptional activity to sustain pro-survival and antiapoptotic signalling. A picture is now starting to emerge that both the cell-cycle and transcriptional functions of CDKs can be exploited pharmacologically with CDK inhibitors that possess appropriate selectivity profiles. In this article, recent advances into these mechanistic insights and how they can guide clinical development in terms of choice of indication are reviewed, as well as combinations with existing chemotherapies. An overview is also given of recent clinical trial results with the lead CDK inhibitor drug candidates seliciclib (CYC202, (R)-roscovitine; Cyclacel) and alvocidib (flavopiridol; Aventis-NCI), as well as the development of other clinical entries and advanced preclinical compounds. The discussion focuses on oncology, but we point out recent results with CDK inhibitors in virology and nephrology.