Induction of death of leukemia cells by TW-74, a novel derivative of chloro-naphthoquinone.

We have previously shown that a 2-chloro-1,4-naphthoquinone derivative (TW-92) induces cell death in leukemia cells. TW-92 exhibited relatively high selectivity towards primary Acute Myeloid Leukemia (AML) cells, as compared to normal mononuclear cells. In view of the selectivity of this family of naphthoquinones, novel chloroaminophenylnaphthoquinone isomers with different methyl substitutions on the phenyl ring were synthesized, and their effect on leukemia cells was tested. These compounds induced cell death in U937 human myeloid leukemia cells, which was prominent following 48 h of culture. Structure-activity relationship studies revealed that TW-74, a novel chloronaphthoquinone with a methyl group at the meta (m) position, was the most active derivative in inducing apoptosis. The mechanism underlying cell death induction by TW-74 was further investigated in U937 cells, a monocytic cell line which serves as a sensitive model of apoptosis induction. TW-74 induced rapid activation of Mitogen Activated Protein Kinases (MAPKs). It caused swelling of isolated rat liver mitochondria and an early reduction of mitochondrial membrane potential in intact cells, indicative of a direct effect on mitochondria. Apoptosis induced by TW-74 was accompanied by cytochrome C release and caspase activation. TW-74 induced down- regulation of (BCL2), an anti-apoptotic protein. Furthermore, TW-74 induced selective dose-dependent cell death in primary B-Chronic Lymphocytic Leukemia (CLL) cells. These findings demonstrate that chloronaphthoquiniones use common as well as diverse mechanisms for the induction of cell death. The data reported here warrant further studies of the utility of TW-74 in the treatment of CLL.

High content of Langerhans cells in malignant lymphoma--incidence and significance.

We describe 25 patients, 14 with classical Hodgkin lymphoma and 11 with non-Hodgkin lymphoma, in all of whom an excess of Langerhans cells was evident. Except for the first three cases, in which the excess of Langerhans cells was identified on routine slides, the remaining cases were disclosed by actively investigating lymphomas with excess of CD68+ histiocytes and performing CD1a and S-100 protein immunostains. Although no clonality study was performed on the Langerhans cells, we endorse the view which states that in the above association, the Langerhans cells are polyclonal. Fourteen cases of Hodgkin lymphoma with a large number of Langerhans cells were identified in a cohort of 231 classical Hodgkin lymphomas. We compared the features of classical Hodgkin lymphoma with abundant Langerhans cells with those without Langerhans cells. Our analysis reveals that Hodgkin lymphoma with Langerhans cell excess shows greater LMP1/EBV expression (P = .007) and lower p53 expression (P = .042) in the Hodgkin-Reed-Sternberg cells but is not associated with a poorer outcome.

The anti-leukaemic activity of novel synthetic naphthoquinones against acute myeloid leukaemia: induction of cell death via the triggering of multiple signalling pathways.

Naphthoquinones, such as menadione, display lower toxicity than anthracyclins used in cancer chemotherapy. Novel anti-leukaemic compounds comprised of chloro-amino-phenyl naphthoquinones with substitutions on the benzoic ring were developed. Structure-activity relationship studies indicated that the analogue with both methyl and amine substitutions (named TW-92) was the most efficient in killing leukaemic cells. Treatment of U-937 promonocytic cells with TW-92 induced apoptotic or necrotic cell death, dependent on incubation and dose conditions. TW-92 induced rapid phosphorylation of p38 mitogen-activated protein kinase (p38(MAPK)) and of extracellular signal-regulated protein kinases (ERK1/2). The generation of apoptosis was preceded by intracellular H(2)O(2) accumulation accompanied by glutathione depletion, the former inhibited by di-phenyl-iodonium (DPI), an inhibitor of NADPH oxidase. TW-92 induced swelling of isolated rat liver mitochondria, indicative of a direct effect on mitochondria. Apoptosis in intact cells was accompanied by a decrease in mitochondrial membrane potential, cytochrome c release and caspase activation. In addition, the level of Mcl-1, an anti-apoptotic regulatory protein, was down-regulated, whereas the expression of the pro-apoptotic BAX was elevated. Finally, TW-92 exerted strong pro-apoptotic and necrotic effects in primary acute myeloid leukaemia samples when given in submicromolar concentrations. Together, these findings demonstrate that TW-92 may provide an effective anti-leukaemic strategy.

Splenic micronodular T-cell/histiocyte-rich large B-cell lymphoma: effect of prior corticosteroid therapy.

We report on three patients who were treated with corticosteroids only prior to the diagnosis of splenic lymphoma. Corticosteroids were administered for different conditions, at different doses, and for various periods of time. The primary diagnosis was splenic micronodular T-cell/histiocyte-rich large B-cell lymphoma in the three cases, and it was reached with variable difficulty. We suggest that the corticosteroid treatment was one of the causes for the complications in reaching a diagnosis. The morphologic appearance of the microscopic splenic nodules was the most variable feature and may possibly reflect the dose and duration of the corticosteroid therapy. However, the histopathologic changes are probably not related with Epstein-Barr virus-induced immunosuppression.

Mantle cell lymphoma in a tubular adenoma: unusual presentation with synchronous colonic carcinoma.

An 80-year-old man underwent sigmoidectomy for adenocarcinoma. Six months later, after a near-syncope incident, pancytopenia was detected in the absence of occult blood in the stools. A bone marrow biopsy showed malignant lymphoma, suggestive of mantle cell lymphoma (MCL). Colonoscopy at this time revealed 3 colonic tubular adenomas. Reassessment of the histology of the colonic polyps and appropriate immunohistochemical stains showed that the lamina propria of one of the tubular adenomas was infiltrated by MCL. Reexamination of the sections taken at the time of the original sigmoidectomy showed MCL in 2 of the regional lymph nodes removed at that time, but no evidence of lymphoma in the colon was found. To our knowledge, this is the fifth reported case of synchronous occurrence of intestinal MCL and colonic carcinoma and the first report of MCL presenting in a tubular adenoma of the colon.

Splenic micronodular T-cell/histiocyte-rich large B-cell lymphoma.

A case showing the typical clinical and pathological features of splenic micronodular T-cell/histiocyte-rich large B-cell lymphoma is presented. Since the series recorded by Dogan et al (Am J Surg Pathol 2003;27:903-911), there have been very few reports on this lymphoma variant. Our case presents minor variations on the recorded features. Possible reasons for the scarcity of reports and for the confirmation of this lymphoma as a variant of T-cell-rich large B-cell lymphoma are discussed.

A molecular mechanism for mimosine-induced apoptosis involving oxidative stress and mitochondrial activation.

Mimosine, a non-protein amino acid, is mainly known for its action as a reversible inhibitor of DNA replication and, therefore, has been widely used as a cell cycle synchronizing agent. Recently, it has been shown that mimosine also induces apoptosis, as mainly reflected in its ability to elicit characteristic nuclear changes. The present study elucidates the mechanism underlying mimosine's apoptotic effects, using the U-937 leukemia cell line. We now demonstrate that in isolated rat liver mitochondria, mimosine induces mitochondrial swelling that can be inhibited by cyclosporine A, indicative of permeability transition (PT) mega-channel opening. Mimosine-induced apoptosis was accompanied by formation of hydrogen peroxide and a decrease in reduced glutathione levels. The apoptotic process was partially inhibited by cyclosporine A and substantially blocked by the antioxidant N-acetylcysteine, suggesting an essential role for reactive oxygen species formation during the apoptotic processes. The apoptosis induced by mimosine was also accompanied by a decrease in mitochondrial membrane potential, cytochrome c release and caspase 3 and 9 activation. Our results thus imply that mimosine activates apoptosis through mitochondrial activation and formation of H2O2, both of which play functional roles in the induction of cell death.