Maxwell M. Krem

Mutations in a gene encoding a midbody kelch protein in familial and sporadic classical Hodgkin lymphoma lead to binucleated cells

Classical Hodgkin lymphoma (cHL) is a malignancy of B-cell origin in which the neoplastic cells, known as “Reed-Sternberg” (RS) cells, are characteristically binucleated. Here we describe a family where multiple individuals developing cHL have inherited a reciprocal translocation between chromosomes 2 and 3. The translocation disrupts KLHDC8B, an uncharacterized gene from a region (3p21.31) previously implicated in lymphoma and related malignancies, resulting in its loss of expression. We tested KLHDC8B as a candidate gene for cHL and found that a 5′-UTR polymorphism responsible for decreasing its translational expression is associated with cHL in probands from other families with cHL and segregates with disease in those pedigrees. In one of three informative sporadic cases of cHL, we detected loss of heterozygosity (LOH) for KLHDC8B in RS cells, but not reactive T lymphocytes, purified from a malignant lymph node. KLHDC8B encodes a protein predicted to contain seven kelch repeat domains. KLHDC8B is expressed during mitosis, where it localizes to the midbody structure connecting cells about to separate during cytokinesis, and it is degraded after cell division. Depletion of KLHDC8B through RNA interference leads to an increase in binucleated cells, implicating its reduced expression in the formation of cHLs signature RS cell.

Conserved Ser residues, the shutter region, and speciation in serpin evolution.

The suicide inhibitory mechanism of serine protease inhibitors of the serpin superfamily depends heavily on their structural flexibility, which is controlled in large part by the breach and shutter regions of the central Aβ-sheet. We examined codon usage by the highly conserved residues, Ser-53 and Ser-56, of the shutter region and found a TCN-AGY usage dichotomy for Ser-56 that remarkably is linked to the protostome-deuterostome split. Our results suggest that serpin evolution was driven by phylogenetic speciation and not pressure to fulfill new physiologic functions mitigating against coevolution with the family of serine proteases they inhibit.

The Kelch Protein KLHDC8B Guards against Mitotic Errors, Centrosomal Amplification, and Chromosomal Instability

Background: The large multinucleated Reed-Sternberg cell is the driving force behind Hodgkin lymphoma pathogenesis. Results: Disrupting KLHDC8B function leads to multinucleation, failed mitoses, centrosomal amplification, and aneuploidy, the major pathologic features of the Reed-Sternberg cell. Conclusion: KLHDC8B protects against mitotic errors and chromosomal instability. Significance: Midbody proteins play a previously unappreciated key role in Hodgkin lymphoma pathogenesis. The malignant cell in classical Hodgkin lymphoma (HL) is the binucleated giant Reed-Sternberg cell. Chromosomal instability and mitotic errors may contribute to HL pathogenesis; one potential mitotic regulator is the kelch protein KLHDC8B, which localizes to the midbody, is expressed during mitosis, and is mutated in a subset of familial and sporadic HL. We report that disrupting KLHDC8B function in HeLa cells, B lymphoblasts, and fibroblasts leads to significant increases in multinucleation, multipolar mitoses, failed abscission, asymmetric segregation of daughter nuclei, formation of anucleated daughter cells, centrosomal amplification, and aneuploidy. We recapitulated the major pathologic features of the Reed-Sternberg cell and concluded that KLHDC8B is essential for mitotic integrity and maintenance of chromosomal stability. The significant impact of KLHDC8B implicates the central roles of mitotic regulation and chromosomal segregation in the pathogenesis of HL and provides a novel molecular mechanism for chromosomal instability in HL.

MLLT11/AF1q boosts oncogenic STAT3 activity through Src-PDGFR tyrosine kinase signaling.

Constitutive STAT3 activation by tyrosine phosphorylation of mutated or amplified tyrosine kinases (pYSTAT3) is critical for cancer initiation, progression, invasion, and motility of carcinoma cells. We showed that AF1q is associated with STAT3 signaling in breast cancer cells. In xenograft models, enhanced AF1q expression activated STAT3 and promoted tumor growth and metastasis in immunodeficient NSG mice. The cytokine secretory phenotype of MDA-MB-231LN breast cancer cells with altered AF1q expression revealed changes in expression of platelet-derived growth factor subunit B (PDGF-B). AF1q-induced PDGF-B stimulated motility, migration, and invasion of MDA-MB-231LN cells, and AF1q up-regulated platelet-derived growth factor receptor (PDGFR) signaling. Further, AF1q-induced PDGFR signaling enhanced STAT3 activity through Src kinase activation, which could be blocked by the Src kinase inhibitor PP1. Moreover, AF1q up-regulated tyrosine kinase signaling through PDGFR signaling, which was blockable by imatinib. In conclusion, we demonstrated that enhanced AF1q expression contributes to persistent and oncogenic pYSTAT3 levels in invasive carcinoma cells by activating Src kinase through activation of the PDGF-B/PDGFR cascade. Therefore, AF1q plays an essential role as a cofactor in PDGF-B-driven STAT3 signaling.

Mechanisms and clinical applications of chromosomal instability in lymphoid malignancy

Lymphocytes are unique among cells in that they undergo programmed DNA breaks and translocations, but that special property predisposes them to chromosomal instability (CIN), a cardinal feature of neoplastic lymphoid cells that manifests as whole chromosome‐ or translocation‐based aneuploidy. In several lymphoid malignancies translocations may be the defining or diagnostic markers of the diseases. CIN is a cornerstone of the mutational architecture supporting lymphoid neoplasia, though it is perhaps one of the least understood components of malignant transformation in terms of its molecular mechanisms. CIN is associated with prognosis and response to treatment, making it a key area for impacting treatment outcomes and predicting prognoses. Here we will review the types and mechanisms of CIN found in Hodgkin lymphoma, non‐Hodgkin lymphoma, multiple myeloma and the lymphoid leukaemias, with emphasis placed on pathogenic mutations affecting DNA recombination, replication and repair; telomere function; and mitotic regulation of spindle attachment, centrosome function, and chromosomal segregation. We will discuss the means by which chromosome‐level genetic aberrations may give rise to multiple pathogenic mutations required for carcinogenesis and conclude with a discussion of the clinical applications of CIN and aneuploidy to diagnosis, prognosis and therapy.

Mitotic errors, aneuploidy and micronuclei in Hodgkin lymphoma pathogenesis

The Reed-Sternberg (RS) cell is the driving force behind Hodgkin lymphoma (HL), a unique malignancy in which the rare RS cell creates an inflammatory microenvironment that recruits a reactive tumor infiltrate. Well-known oncogenic factors such as nuclear factor kappa B (NFκB) signaling and Epstein-Barr virus infection are linked to HL pathogenesis but do not adequately explain the RS cell’s key pathologic features of multi-nucleation, abnormalities of centrosome function and number and aneuploidy. Chromosomal instability is also considered a key pathway in the origin of the RS cell, though the molecular mechanisms have largely been a “black box.” We demonstrated that the midbody kelch domain protein KLHDC8B protects against mitotic errors, centrosomal amplification and chromosomal instability. Here we discuss how the new findings linking KLHDC8B to mitotic integrity and faithful chromosomal segregation are providing mechanistic explanations for the origin of the RS cell and the molecular pathogenesis of chromosomal instability in HL.

A Rare Case of Erdheim-Chester Disease (Non-Langerhans Cell Histiocytosis) with Concurrent Langerhans Cell Histiocytosis: A Diagnostic and Therapeutic Challenge

Erdheim-Chester disease (ECD) is a rare non-Langerhans cell histiocyte disorder most commonly characterized by multifocal osteosclerotic lesions of the long bones demonstrating sheets of foamy histiocyte infiltrates on biopsy with or without histiocytic infiltration of extraskeletal tissues. ECD can be difficult to diagnose since it is a very rare disease that can affect many organ systems. Diagnosis is based on the pathologic evaluation of involved tissue interpreted within the clinical context. Patients who have the BRAF V600E mutation are treated first line with vemurafenib. For those without the mutation with symptomatic ECD, conventional or PEGylated interferon alpha is recommended. For patients who are either intolerant or nonresponsive to interferon alpha, systemic chemotherapy with or without corticosteroids can be used. We present a rare case of Erdheim-Chester disease with concurrent Langerhans cell histiocytosis which occurs in only one fifth of the cases and often presents as a diagnostic and therapeutic challenge.

Man versus Nature — Also Sprach Zarathustra and an End-of-Life House Call

Reluctantly leaving an end-of-life house call with a patient who has decided to avail himself of his state’s death-with-dignity law, a physician hears a musical composition that reframes the experience in terms of the dialectic of Man versus Nature.

Teaching Old Drugs New Tricks: Repositioning Pharmaceuticals for Bench to Bedside Success.

The article by Zheng et al, “Local anesthetic drug inhibits growth and survival in chronic myeloid leukemia (CML) through suppressing PI3K/AKT/ mTOR,” in this issue is one of several recent examples in The American Journal of Medical Sciences (AJMS) that showcase the possibilities of repositioning drugs as anticancer agents. Drug repositioning, or repurposing, is defined by the National Center for Advancing Translational Sciences as “studying a drug already approved to treat one disease or condition to see if it is safe and effective for treating a different disease.” Research based on this idea has exploded in the past 15 years, and citations mentioning drug repositioning have increased every year since the early 2000s. Zheng et al show evidence that the local anesthetic ropivacaine may have promise in CML via targeting the PI3K/Akt/mTOR signaling pathway. They give evidence that ropivacaine causes growth arrest of CML cells by inhibiting the serine/threonine kinase Akt. The PI3K pathway governs a wide range of cellular housekeeping and growth functions and has become a fertile ground for approvals of new oncology therapies over the past decade. Several agents that inhibit signaling molecules throughout that pathway are used to treat hematologic and solid cancers, and more are on the way. Along these same lines, metformin, a biguanide long used to treat diabetes, is known to inhibit mTOR and its downstream effectors through both AMPK-dependent and independent mechanisms. Recent publications in the AJMS have highlighted metformin’s anticancer properties. A retrospective case-control study suggested that patients with both diabetes and prostate cancer who remained on metformin experienced fewer deaths, cancer recurrences, metastases and secondary cancers. A Department of Veterans Affairs case-control study of lung or colon cancer patients with diabetes showed that patients taking metformin had decreased colon cancer metastases and recurrences. Overall and 5-year survival was improved in both cancers. It must be noted that both studies were retrospective in nature, and the results should be considered hypothesis-generating rather than definitive.

To b(ortezomib) or not to be: the stroma's the thing.

The proteasome inhibitor bortezomib has been widely used to treat patients with multiple myeloma (MM). However, some patients show primary or secondary resistance. In recent work published in The Journal of Pathology, Beyar‐Katz et al demonstrate that bortezomib treatment stimulates a host inflammatory response, which in turn promotes MM cell migration, viability, and proliferation. These effects appear to be mediated by pro‐inflammatory M1‐like stromal macrophages partly via secretion of cytokine IL‐16. These unexpected findings imply that the binary M1/M2 definition of macrophages may not accurately describe the complexity and heterogeneity of macrophages associated with MM tumour growth and progression, and further suggest that bortezomib treatment stimulates host‐driven tumour‐promoting activity in addition to its cytotoxic activity, thus leading to potential bortezomib resistance in MM patients. Understanding the underlying mechanisms may identify novel targets to overcome or prevent bortezomib resistance. Copyright