Novel agents in mantle cell lymphoma

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.

Combining Ibrutinib with Chk1 Inhibitors Synergistically Targets Mantle Cell Lymphoma Cell Lines

BACKGROUND

Mantle cell lymphoma (MCL) is an aggressive B cell lymphoma with an unfavorable clinical course. Besides deregulation of the cell cycle, B cell receptor (BCR) signaling, essential for MCL proliferation and survival, is also often deregulated due to constitutive activation of Bruton's tyrosine kinase (BTK). The BTK inhibitor ibrutinib has been approved as a therapy for refractory MCL, and while it shows some clinical activity, patients frequently develop primary or secondary ibrutinib resistance and have very poor outcomes after relapsing following ibrutinib treatment.

OBJECTIVE

To overcome ibrutinib resistance, new therapeutic approaches are needed. As checkpoint kinase 1 (Chk1) inhibitors have recently been shown to be effective as single agents in MCL, we assessed the combination of ibrutinib with Chk1 inhibitors.

METHODS

We examined the activity of ibrutinib combined with the Chk1 inhibitor PF-00477736 in eight MCL cell lines and analyzed underlying cellular and molecular effects.

RESULTS

The combination was synergistic in all tested cell lines through different mechanisms. The treatment induced apoptosis in ibrutinib-sensitive cell lines, while in ibrutinib-resistant cells the effect was mainly cytostatic and occurred at micromolar concentrations of ibrutinib.

CONCLUSIONS

The pharmacological approach of simultaneously targeting cell cycle checkpoints (by Chk1 inhibitors) and pro-survival pathways (by ibrutinib) might offer a promising new therapeutic strategy for MCL patients.

A gene signature that distinguishes conventional and leukemic nonnodal mantle cell lymphoma helps predict outcome

Mantle cell lymphoma (MCL) is an aggressive B-cell malignancy, but some patients have a very indolent evolution. This heterogeneous course is related, in part, to the different biological characteristics of conventional MCL (cMCL) and the distinct subgroup of leukemic nonnodal MCL (nnMCL). Robust criteria to distinguish these MCL subtypes and additional biological parameters that influence their evolution are not well defined. We describe a novel molecular assay that reliably distinguishes cMCL and nnMCL using blood samples. We trained a 16-gene assay (L-MCL16 assay) on the NanoString platform using 19 purified leukemic samples. The locked assay was applied to an independent cohort of 70 MCL patients with leukemic presentation. The assay assigned 37% of cases to nnMCL and 56% to cMCL. nnMCL and cMCL differed in nodal presentation, lactate dehydrogenase, immunoglobulin heavy chain gene mutational status, management options, genomic complexity, and CDKN2A/ATM deletions, but the proportion with 17p/TP53 aberrations was similar in both subgroups. Sequential samples showed that assay prediction was stable over time. nnMCL had a better overall survival (OS) than cMCL (3-year OS 92% vs 69%; P = .006) from the time of diagnosis and longer time to first treatment. Genomic complexity and TP53/CDKN2A aberrations predicted for shorter OS in the entire series and cMCL, whereas only genomic complexity was associated with shorter time to first treatment and OS in nnMCL. In conclusion, the newly developed assay robustly recognizes the 2 molecular subtypes of MCL in leukemic samples. Its combination with genetic alterations improves the prognostic evaluation and may provide useful biological information for management decisions.