Lawrence R. Zukerberg

Conversion of p35 to p25 deregulates Cdk5 activity and promotes neurodegeneration

Cyclin-dependent kinase 5 (Cdk5) is required for proper development of the mammalian central nervous system. To be activated, Cdk5 has to associate with its regulatory subunit, p35. We have found that p25, a truncated form of p35, accumulates in neurons in the brains of patients with Alzheimers disease. This accumulation correlates with an increase in Cdk5 kinase activity. Unlike p35, p25 is not readily degraded, and binding of p25 to Cdk5 constitutively activates Cdk5, changes its cellular location and alters its substrate specificity. In vivo the p25/Cdk5 complex hyperphosphorylates tau, which reduces taus ability to associate with microtubules. Moreover, expression of the p25/Cdk5 complex in cultured primary neurons induces cytoskeletal disruption, morphological degeneration and apoptosis. These findings indicate that cleavage of p35, followed by accumulation of p25, may be involved in the pathogenesis of cytoskeletal abnormalities and neuronal death in neurodegenerative diseases.

Induction of interleukin-8 preserves the angiogenic response in HIF-1alpha-deficient colon cancer cells.

Hypoxia inducible factor-1 (HIF-1) is considered a crucial mediator of the cellular response to hypoxia through its regulation of genes that control angiogenesis. It represents an attractive therapeutic target in colon cancer, one of the few tumor types that shows a clinical response to antiangiogenic therapy. But it is unclear whether inhibition of HIF-1 alone is sufficient to block tumor angiogenesis. In HIF-1α knockdown DLD-1 colon cancer cells (DLD-1HIF-kd), the hypoxic induction of vascular endothelial growth factor (VEGF) was only partially blocked. Xenografts remained highly vascularized with microvessel densities identical to DLD-1 tumors that had wild-type HIF-1α (DLD-1HIF-wt). In addition to the preserved expression of VEGF, the proangiogenic cytokine interleukin (IL)-8 was induced by hypoxia in DLD-1HIF-kd but not DLD-1HIF-wt cells. This induction was mediated by the production of hydrogen peroxide and subsequent activation of NF-κB. Furthermore, the KRAS oncogene, which is commonly mutated in colon cancer, enhanced the hypoxic induction of IL-8. A neutralizing antibody to IL-8 substantially inhibited angiogenesis and tumor growth in DLD-1HIF-kd but not DLD-1HIF-wt xenografts, verifying the functional significance of this IL-8 response. Thus, compensatory pathways can be activated to preserve the tumor angiogenic response, and strategies that inhibit HIF-1α may be most effective when IL-8 is simultaneously targeted.

Kaposiform hemangioendothelioma of infancy and childhood. An aggressive neoplasm associated with Kasabach-Merritt syndrome and lymphangiomatosis

We report the clinical and pathological features of nine distinctive, but relatively unknown, vascular tumors of infancy and childhood presenting as soft tissue masses often associated with locally aggressive disease, lymphangiomatosis and Kasabach-Merritt syndrome. The patients, four males and five females, were all in their first decade of life except for two (median, 2 years; range, 5 months to 19 years). These tumors involved deep soft tissues of the upper extremity (four cases), retroperitoneum (two cases), chest wall, scalp, and neck (one case each). Four patients also had Kasabach-Merritt syndrome, and three patients had lymphangiomatosis. Lymphangiomatosis consisted of diffusely infiltrating lymphangioma of soft tissue (three cases) and in two by the additional presence of bone lesions. In one of these three cases, lymphangiomatosis antedated the diagnosis of the vascular tumor, and in the remainder they were concurrently diagnosed. Tumors were characterized by infiltrating, interconnecting sheets or irregular nodules of slender endothelial cells lining crescentic or slit-like vessels and, less commonly, rounded capillary-type vessels. Within some tumors, nests of epithelioid endothelial cells with prominent eosinophilic cytoplasm containing finely granular hemosiderin, hyaline droplets, and cytoplasmic vacuoles were identified. Smaller amounts of hemosiderin were observed within the spindled endothelial cells and microthrombi could be seen occasionally within the tiny lumina. Nuclear atypia was minimal within these tumors and mitotic figures were infrequent, averaging 2 to 3/10 high-power fields (HPF) (range 0-7/10 HPF). Larger, well-formed feeding vessels were present at the periphery of the tumor. The endothelium of these vessels expressed factor VIII-AG, CD34, and bound Ulex europaeus, and muscle- specific actin. In contrast, the spindled tumor cells expressed only CD34. Human papilloma virus (HPV)-16- like DNA transcripts, which have been identified in cases of Kaposis sarcoma, were not detected by polymerase chain reaction in two cases. Follow-up information revealed that four patients were alive without disease after wide excision, multiple excision(s), or amputation (one case); three were alive with disease; and two died, one from lymphangiomatosis with respiratory compromise and the other from hemorrhage complicating Kasabach-Merritt syndrome. It appears that treatment should consist of wide local excision and supportive therapy for associated symptoms.

Cables Links Cdk5 and c-Abl and Facilitates Cdk5 Tyrosine Phosphorylation, Kinase Upregulation, and Neurite Outgrowth

Cyclin-dependent kinase 5 (Cdk5) is a small serine/threonine kinase that plays a pivotal role during development of the CNS. Cables, a novel protein, interacts with Cdk5 in brain lysates. Cables also binds to and is a substrate of the c-Abl tyrosine kinase. Active c-Abl kinase leads to Cdk5 tyrosine phosphorylation, and this phosphorylation is enhanced by Cables. Phosphorylation of Cdk5 by c-Abl occurs on tyrosine 15 (Y15), which is stimulatory for p35/Cdk5 kinase activity. Expression of antisense Cables in primary cortical neurons inhibited neurite outgrowth. Furthermore, expression of active Abl resulted in lengthening of neurites. The data provide evidence for a Cables-mediated interplay between the Cdk5 and c-Abl signaling pathways in the developing nervous system.

mTORC1 in the Paneth cell niche couples intestinal stem-cell function to calorie intake

How adult tissue stem and niche cells respond to the nutritional state of an organism is not well understood. Here we find that Paneth cells, a key constituent of the mammalian intestinal stem-cell (ISC) niche, augment stem-cell function in response to calorie restriction. Calorie restriction acts by reducing mechanistic target of rapamycin complex 1 (mTORC1) signalling in Paneth cells, and the ISC-enhancing effects of calorie restriction can be mimicked by rapamycin. Calorie intake regulates mTORC1 in Paneth cells, but not ISCs, and forced activation of mTORC1 in Paneth cells during calorie restriction abolishes the ISC-augmenting effects of the niche. Finally, increased expression of bone stromal antigen 1 (Bst1) in Paneth cells—an ectoenzyme that produces the paracrine factor cyclic ADP ribose—mediates the effects of calorie restriction and rapamycin on ISC function. Our findings establish that mTORC1 non-cell-autonomously regulates stem-cell self-renewal, and highlight a significant role of the mammalian intestinal niche in coupling stem-cell function to organismal physiology.

B-cell lymphomas with concurrent IGH-BCL2 and MYC rearrangements are aggressive neoplasms with clinical and pathologic features distinct from Burkitt lymphoma and diffuse large B-cell lymphoma.

B-cell lymphomas with concurrent IGH-BCL2 and MYC rearrangements, also known as “double-hit” lymphomas (DHL), are rare neoplasms characterized by highly aggressive clinical behavior, complex karyotypes, and a spectrum of pathologic features overlapping with Burkitt lymphoma (BL), diffuse large B-cell lymphoma (DLBCL) and B-lymphoblastic lymphoma/leukemia (B-LBL). The clinical and pathologic spectrum of this rare entity, including comparison to other high-grade B-cell neoplasms, has not been well defined. We conducted a retrospective analysis of clinical and pathologic features of 20 cases of DHL seen at our institution during a 5-year period. In addition, we carried out case-control comparisons of DHL with BL and International Prognostic Index (IPI)-matched DLBCL. The 11 men and 9 women had a median age of 63.5 years (range 32 to 91). Six patients had a history of grade 1 to 2 follicular lymphoma; review of the prior biopsy specimens in 2 of 5 cases revealed blastoid morphology. Eighteen patients had Ann Arbor stage 3 or 4 disease and all had elevated serum lactate dehydrogenase (LDH) levels at presentation. Extranodal disease was present in 17/20 (85%), bone marrow involvement in 10/17 (59%) and central nervous system (CNS) disease in 5/11 (45%). Nineteen patients were treated with combination chemotherapy, of whom 18 received rituximab and 14 received CNS-directed therapy. Fourteen patients (70%) died within 8 months of diagnosis. Median overall survival in the DHL group (4.5 mo) was inferior to both BL (P=0.002) and IPI-matched DLBCL (P=0.04) control patients. Twelve DHL cases (60%) were classified as B-cell lymphoma, unclassifiable, with features intermediate between DLBCL and BL, 7 cases (35%) as DLBCL, not otherwise specified, and 1 case as B-LBL. Distinguishing features from BL included expression of Bcl2 (P<0.0001), Mum1/IRF4 (P=0.006), Ki-67 <95% (P<0.0001), and absence of EBV-EBER (P=0.006). DHL commonly contained the t(8;22) rather than the t(8;14) seen in most BL controls (P=0.001), and exhibited a higher number of chromosomal aberrations (P=0.0009). DHL is a high-grade B-cell neoplasm with a poor prognosis, resistance to multiagent chemotherapy, and clinical and pathologic features distinct from other high-grade B-cell neoplasms. Familiarity with the morphologic and immunophenotypic spectrum of DHL is important in directing testing to detect concurrent IGH-BCL2 and MYC rearrangements when a karyotype is unavailable. The aggressive clinical behavior and combination of genetic abnormalities seen in these cases may warrant categorization as a separate entity in future classifications and call for novel therapeutic approaches.

Lymphoma of the ocular adnexa: A study of 353 cases.

We studied the cases of 353 patients with lymphoma involving the ocular adnexa diagnosed at the Massachusetts General Hospital between 1974 and 2005. The patients included 153 males and 200 females, aged 7 to 95 years, with a mean age of 64 years. In 277 cases, there was no known history of lymphoma. Seventy-six patients had a history of lymphoma, with the ocular adnexa being involved at relapse or with progression of the previously diagnosed lymphoma. The patients had marginal zone lymphoma (182 cases), follicular lymphoma (80 cases), mantle cell lymphoma (18 cases), small lymphocytic lymphoma/chronic lymphocytic leukemia (13 cases), lymphoplasmacytic lymphoma (4 cases), splenic marginal zone lymphoma (2 cases), low-grade B cell, not subclassified (19 cases), precursor B lymphoblastic lymphoma (3 cases), diffuse large B-cell lymphoma (26 cases), and 1 case each of high-grade B-cell lymphoma, not subclassified, peripheral T-cell lymphoma, unspecified type, extranodal NK/T-cell lymphoma, nasal type, and Hodgkin lymphoma, nodular sclerosis type. Almost all marginal zone lymphoma patients (168 of 182, 92%) had primary ocular adnexal lymphoma. Fourteen marginal zone lymphoma patients (8%) had a prior history of lymphoma, usually arising in another extranodal site. Twenty-five of 80 (31%) follicular lymphoma patients had a prior history of lymphoma, usually arising in lymph nodes. Patients with mantle cell lymphoma, chronic lymphocytic leukemia, lymphoplasmacytic lymphoma, and splenic marginal zone lymphoma almost always had a prior history of lymphoma or were known to have widespread disease at the time of diagnosis of ocular adnexal lymphoma. A subset of the diffuse large B-cell lymphomas were associated with large destructive masses involving adjacent structures such as paranasal sinuses, raising the possibility that they may have arisen from one of the adjacent structures and involved the ocular adnexa by direct extension. The relatively high proportion of low-grade lymphoma, not subclassified, highlights the difficulty that may arise in distinguishing different types of low-grade lymphoma, particularly when biopsies are small and artifactually distorted. Ocular adnexal lymphoma is primarily a disease of older adults, with a slight female preponderance. Most lymphomas are low-grade B-cell lymphomas, with marginal zone lymphoma being by far the most common type. Marginal zone lymphoma typically involves the ocular adnexa primarily, whereas other types of low-grade B-cell lymphoma often involve the ocular adnexa secondarily. High-grade B-cell lymphomas only occasionally involve the ocular adnexa, and T-cell lymphoma, NK-cell lymphoma, and Hodgkin lymphoma are only rarely encountered in this site.

In vivo association of E2F and DP family proteins.

The mammalian transcription factor E2F plays an important role in regulating the expression of genes that are required for passage through the cell cycle. This transcriptional activity is inhibited by association with the retinoblastoma tumor suppressor protein (pRB) or its relatives p107 and p103. The first cDNA from the E2F family to be cloned was designated E2F-1, and multiple E2F family members have now been identified. They bind to DNA as heterodimers, interacting with proteins known as DP. Here we demonstrate that DP is also a family of polypeptides with at least two members (hDP-1 and hDP-2). Both hDP-1 and hDP-2 bind to all E2F family members in vivo, and each complex is capable of activating transcription. However, the various E2F/DP complexes display strong differences in the ability to bind to either pRB or p107 in vivo, and the specificity of pRB or p107 binding is mediated by the E2F subunit.

Solitary fibrous tumor of the nasal cavity and paranasal sinuses

We report two solitary fibrous tumors of the nasal cavity and paranasal sinuses that were histologically and immunohistochemically virtually identical to solitary fibrous tumors (fibrous mesotheliomas) of the pleura. One tumor arose in a 48-year-old woman and the other in a 45-year-old woman. Both patients presented with nasal symptoms, and both patients are alive without evidence of disease 6 months and 1 year after excision. The tumors had a disorganized or “patternless” arrangement of spindle cells in a collagenous background and prominent vascular channels of varying size. Immunoperoxidase stains on paraffin sections showed staining of the cells for vimentin only; there was no staining for keratin, S-100 protein, desmin, and actin. Both cases presented some degree of diagnostic difficulty and had to be distinguished from other spindle cell tumors of the nasal cavity and paranasal sinuses, such as hemangiopericytoma, angiofibroma, and fibrous histiocytoma.

Chronic sclerosing sialadenitis (Küttner tumor) is an IgG4-associated disease.

BackgroundChronic sclerosing sialadenitis is a fibroinflammatory disease of the salivary glands, characteristically of the submandibular gland. One prior Asian study proposed that chronic sclerosing sialadenitis is a part of the spectrum of IgG4-associated disease. This association has not been confirmed in Western populations. We therefore, investigated the relationship between IgG4 and chronic sclerosing sialadenitis, and compared the histomorphologic features of this condition with those of chronic sialadenitis-not otherwise specified, Sjögren syndrome, and lymphoepithelial sialadenitis. Materials and MethodsWe evaluated 13 cases of chronic sclerosing sialadenitis and compared them with 15 cases of chronic sialadenitis-not otherwise specified, 8 lip biopsies from individuals with Sjögren syndrome, and 4 cases of lymphoepithelial sialadenitis. Immunohistochemistry for IgG, and IgG4 was carried out. IgG4-positive plasma cells were quantified and the IgG4/IgG ratio was calculated. ResultsSeven patients with chronic sclerosing sialadenitis were female and 6 were male. Their mean age was 61 years (range: 27 to 80). Twelve chronic sclerosing sialadenitis cases involved the submandibular gland (bilaterally in 3) and in 1 there was a parotid lesion. Three of these 12 cases had manifestations of IgG4-associated systemic disease. Morphologically these specimens had preservation of lobular architecture, hypercellular interlobular fibrosis, florid lymphoid hyperplasia, and numerous plasma cells. Obliterative phlebitis was observed in 6 cases. The histologic features of chronic sclerosing sialadenitis were reminiscent of autoimmune pancreatitis, and were either not observed or were present only focally in cases of chronic sialadenitis, Sjögren syndrome, and lymphoepithelial sialadenitis.Eleven of 12 evaluable cases showed an increased number of IgG4 plasma cells with a mean of 229/high-power field (HPF) (range 75 to 608) and an overall IgG4/IgG ratio of 0.86 (range 0.5 to 1). The only patient whose biopsy lacked IgG4-positive plasma cells had pathologic evidence of cytomegalovirus infection. Chronic sclerosing sialadenitis cases, in comparison with the other 3 groups studied, showed a significantly higher number of IgG4 positive plasma cells (P<0.05). Patients with chronic sialadenitis-not otherwise specified had a median number of only 16 IgG4-positive plasma cells/HPF (range 2 to 44), with an IgG4/IgG ratio of 0.14 (range 0.02 to 0.28). The Sjögren syndrome patients had a median of 1 IgG4-positive plasma cell/HPF (range 0 to 3), with an IgG4/IgG ratio of 0.02 (range 0 to 0.07). Patients with lymphoepithelial sialadenitis had a median of 0 IgG4-positive plasma cells per HPF. ConclusionChronic sclerosing sialadenitis has a characteristic morphologic appearance. This morphologic appearance, in conjunction with the elevated IgG4 expression, distinguishes chronic sclerosing sialadenitis from other inflammatory diseases of the salivary glands. Chronic sclerosing sialadenitis belongs to the spectrum of IgG4-related diseases.