Characterizing the immune response to myocardial infarction in pigs.

Though myocardial infarction (MI) in pigs is a well-established translational large animal model, it has not yet been widely used for immunotherapy studies, and a comprehensive description of the immune response to MI in this species is lacking. We induced MI in Landrace pigs by balloon occlusion of the left anterior descending artery over 90 min. Within 14 days, the necrotic myocardium was progressively replaced by scar tissue with involvement of myofibroblasts. We characterized the immune response in the heart ex vivo by (immuno)histology, flow cytometry, and RNA sequencing of myocardial tissue on days 3, 7, and 14 after MI. Besides a clear predominance of myeloid cells among heart-infiltrating leukocytes, we detected activated T cells and an increasing proportion of CD4+ Foxp3+ regulatory T cells (Treg), especially in the infarct core-findings that closely mirror what has been observed in mice and humans after MI. Transcriptome data indicated inflammatory activity that was persistent but markedly changing in character over time and linked to extracellular matrix biology. Analysis of lymphocytes in heart-draining lymph nodes revealed significantly higher proliferation rates of T helper cell subsets, including Treg on day 7 after MI, compared to sham controls. Elevated frequencies of myeloid progenitors in the spleen suggest that it might be a site of emergency myelopoiesis after MI in pigs, as previously shown in mice. We thus provide a first description of the immune response to MI in pigs, and our results can aid future research using the species for preclinical immunotherapy studies.

B-cell receptor-driven MALT1 activity regulates MYC signaling in mantle cell lymphoma.

Mantle cell lymphoma (MCL) is a mature B-cell lymphoma characterized by poor clinical outcome. Recent studies revealed the importance of B-cell receptor (BCR) signaling in maintaining MCL survival. However, it remains unclear which role MALT1, an essential component of the CARD11-BCL10-MALT1 complex that links BCR signaling to the NF-κB pathway, plays in the biology of MCL. Here we show that a subset of MCLs is addicted to MALT1, as its inhibition by either RNA or pharmacologic interference induced cytotoxicity both in vitro and in vivo. Gene expression profiling following MALT1 inhibition demonstrated that MALT1 controls an MYC-driven gene expression network predominantly through increasing MYC protein stability. Thus, our analyses identify a previously unappreciated regulatory mechanism of MYC expression. Investigating primary mouse splenocytes, we could demonstrate that MALT1-induced MYC regulation is not restricted to MCL, but represents a common mechanism. MYC itself is pivotal for MCL survival because its downregulation and pharmacologic inhibition induced cytotoxicity in all MCL models. Collectively, these results provide a strong mechanistic rationale to investigate the therapeutic efficacy of targeting the MALT1-MYC axis in MCL patients.

Variability in morphology and cell proliferation in sequential biopsies of mantle cell lymphoma at diagnosis and relapse: clinical correlation and insights into disease progression.

AIMS: The variable morphology of mantle cell lymphoma (MCL) is assumed to reflect progression from an early form with classical cytology and mantle zone or nodular growth to a later, more aggressive variant of the disease with blastoid cytology and a diffuse growth pattern. However, studies of sequential biopsies of MCL are very limited, and we therefore undertook to carry out such a study. METHODS AND RESULTS: We analysed a cohort of 47 MCLs at primary diagnosis and relapse for cytology, growth pattern, and Ki67 index, and correlated the findings with outcome. In the majority of cases, the mantle zone growth pattern was lost, but it had been reacquired in a small subset of MCLs at relapse. Twenty-two per cent of MCLs with classical/small cell cytology acquired blastoid features during the course of the disease. However, 50% of MCLs with blastoid cytology at primary diagnosis recurred as a classical variant. The Ki67 index increased over time, and was associated with prognosis in the primary and the relapse biopsy specimens. CONCLUSIONS: This is the first study to show, in a large cohort of MCLs, that the Ki67 index increases over time in MCL. Assessment of the Ki67 index remains a useful prognostic tool if assessment is performed in the relapse situation.

Hibernoma of the Upper Extremity: Complete Case of a Rare but Benign Soft Tissue Tumor.

Hibernoma is a rare benign lipomatous tumor showing differentiation of brown fatty tissue. To the author's best knowledge, there is no known case of malignant transformation or metastasis. Due to their slow, noninfiltrating growth hibernomas are often an incidental finding in the third or fourth decade of life. The vast majority are located in the thigh, neck, and periscapular region. A diagnostic workup includes ultrasound and contrast-enhanced MRI. Differential diagnosis is benign lipoma, well-differentiated liposarcoma, and rhabdomyoma. An incisional biopsy followed by marginal resection of the tumor is the standard of care, and recurrence after complete resection is not reported. The current paper presents diagnostic and intraoperative findings of a hibernoma of the upper arm and reviews similar reports in the current literature.

The molecular pathogenesis of mantle cell lymphoma.

Mantle cell lymphoma (MCL) is characterized by the translocation t(11;14) leading to constitutive cyclin D1 overexpression. However, overexpression of cyclin D1 alone is insufficient to cause malignant transformation. Secondary genetic alterations and deregulated signaling pathways involved in DNA damage response, cell proliferation, and apoptosis are indispensable for MCL lymphomagenesis. Recent studies investigating the biology of MCL have revealed crucial importance of B-cell receptor (BCR), nuclear factor-kappa B (NF-κB), phosphoinositide 3-kinase (PI3K), and BCL2 signaling for the molecular pathogenesis of MCL. In addition, activation of the Janus kinase (JAK)/signal transducer and activator of transcription 3 (STAT3), NOTCH and WNT pathway can be observed in subsets of MCLs. These addictions can potentially be utilized therapeutically by implementing small molecule inhibitors into current treatment regimens.

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.

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."