Critical B-lymphoid cell intrinsic role of endogenous MCL-1 in c-MYC-induced lymphomagenesis.

Evasion of apoptosis is critical for tumorigenesis, and sustained survival of nascent neoplastic cells may depend upon the endogenous levels of pro-survival BCL-2 family members. Indeed, previous studies using gene-targeted mice revealed that BCL-XL, but surprisingly not BCL-2, is critical for the development of c-MYC-induced pre-B/B lymphomas. However, it remains unclear whether another pro-survival BCL-2 relative contributes to their development. MCL-1 is an intriguing candidate, because it is required for cell survival during early B-lymphocyte differentiation. It is expressed abnormally high in several types of human B-cell lymphomas and is implicated in their resistance to chemotherapy. To test the B-cell intrinsic requirement for endogenous MCL-1 in lymphoma development, we conditionally deleted Mcl-1 in B-lymphoid cells of Eµ-Myc transgenic mice. We found that MCL-1 loss in early B-lymphoid progenitors delayed MYC-driven lymphomagenesis. Moreover, the lymphomas that arose when MCL-1 levels were diminished appeared to have been selected for reduced levels of BIM and/or increased levels of BCL-XL. These results underscore the importance of MCL-1 in lymphoma development and show that alterations in the levels of other cell death regulators can compensate for deficiencies in MCL-1 expression.

BET inhibition represses miR17-92 to drive BIM-initiated apoptosis of normal and transformed hematopoietic cells.

The BET (bromodomain and extraterminal domain) bromodomain-containing proteins, such as BRD4, are highly promising targets for treating lymphoid and myeloid malignancies. They act to modulate the expression of multiple genes that control diverse cellular processes including proliferation, survival and differentiation that are consequentially disrupted by small-molecule BET bromodomain inhibitors such as JQ1. By assessing the impact of these inhibitors on normal mouse hematopoietic cells or their transformed counterparts, we establish definitively that their cytotoxic action in vitro and in vivo relies predominantly on the activation of BAX/BAK-dependent mitochondrial (intrinsic) apoptosis. In large part, this is triggered by marked upregulation of the BH3-only protein BIM when the BET inhibitors suppress miR-17-92, a key post-transcriptional repressor of BIM expression. Thus, our study strongly suggests that mutations that permit the evasion of apoptosis (for example, BCL2 overexpression, BIM inactivation) are likely to blunt the activity of the BET bromodomain inhibitors and should be anticipated when therapy resistance develops. Strikingly, we also found that certain normal hematopoietic cells, especially those of lymphoid origin, are as prone to apoptosis induced by the BET inhibitors as their transformed counterparts, indicating that their susceptibility to BET inhibitors did not arise from oncogenic transformation.

Re-activation of mitochondrial apoptosis inhibits T-cell lymphoma survival and treatment resistance.

T lymphocyte non-Hodgkin's lymphoma (T-NHL) represents an aggressive and largely therapy-resistant subtype of lymphoid malignancies. As deregulated apoptosis is a frequent hallmark of lymphomagenesis, we analyzed gene expression profiles and protein levels of primary human T-NHL samples for various apoptotic regulators. We identified the apoptotic regulator MCL-1 as the only pro-survival BCL-2 family member to be highly expressed throughout all human T-NHL subtypes. Functional validation of pro-survival protein members of the BCL-2 family in two independent T-NHL mouse models identified that the partial loss of Mcl-1 significantly delayed T-NHL development in vivo. Moreover, the inducible reduction of MCL-1 protein levels in lymphoma-burdened mice severely impaired the continued survival of T-NHL cells, increased their susceptibility to chemotherapeutics and delayed lymphoma progression. Lymphoma viability remained unaffected by the genetic deletion or pharmacological inhibition of all alternative BCL-2 family members. Consistent with a therapeutic window for MCL-1 treatment within the context of the whole organism, we observed an only minimal toxicity after systemic heterozygous loss of Mcl-1 in vivo. We conclude that re-activation of mitochondrial apoptosis by blockade of MCL-1 represents a promising therapeutic strategy to treat T-cell lymphoma.

Impact of the combined loss of BOK, BAX and BAK on the hematopoietic system is slightly more severe than compound loss of BAX and BAK.

It is well established that BAX and BAK play crucial, overlapping roles in the intrinsic pathway of apoptosis. Gene targeted mice lacking both BAX and BAK have previously been generated, but the majority of these animals died perinatally. BOK is a poorly studied relative of BAX and BAK that shares extensive amino acid sequence homology to both proteins, but its function remains largely unclear to date. To determine whether BOK plays an overlapping role with BAX and BAK, we utilized a hematopoietic reconstitution model where lethally irradiated wild type mice were transplanted with Bok(-/-)Bax(-/-)Bak(-/-) triple knockout (TKO) fetal liver cells, and compared alongside mice reconstituted with a Bax(-/-)Bak(-/-) double knockout (DKO) hematopoietic compartment. We report here that mice with a TKO and DKO hematopoietic system died at a similar rate and much earlier than control animals, mostly due to severe autoimmune pathology. Both TKO and DKO reconstituted mice also had altered frequencies of various leukocyte subsets in the thymus, bone marrow and spleen, displayed leukocyte infiltrates and autoimmune pathology in multiple tissues, as well as elevated levels of anti-nuclear autoantibodies. Interestingly, the additional deletion of BOK (on top of BAX and BAK loss) led to a further increase in peripheral blood lymphocytes, as well as enhanced lymphoid infiltration in some organs. These findings suggest that BOK may have some functions that are redundant with BAX and BAK in the hematopoietic system.

Development of a new vascular prosthetic: lessons learned.

In 1972, polytetrafluoroethylene (PTFE) (GoreTex) wire insulation was first implanted into arteries and veins of dogs at the University of Colorado Health Sciences Center in Denver. Subsequent modifications including fibrillar arrangement, wall thickness, and pore size led to the development of a vascular prosthesis with tissue ingrowth, viable neointima, and encouraging patency rates. Tissue culture, surface charge, and platelet studies have all demonstrated the optimal biologic qualities of PTFE grafts. Replacement of one human portal vein by a PTFE graft for invasive carcinoma of the pancreas was strikingly successful. Only unexplained intimal hyperplasia at the arterial anastomotic margins discouraged us from extensive early clinical trials.

Reassessment of simple cholecystostomy.

Cholecystostomy was performed on 22 patients with acute cholecystitis after partial (13) or complete (9) removal of gallbladder stones. One patient had complementary common-duct drainage. Early mortality occurred in two patients. Three patients with associated cholangitis but intraoperative reflux of cysticduct bile were all treated by cholecystostomy alone and survived. For the poor-risk patient with cholecystitis, cholecystostomy is effective. When there is associated cholangitis and documented cystic-duct patency, cholecystostomy is also sufficient. When accompanying cholangitis is associated with cystic-duct occlusion, choledochotomy and T tube drainage should be added.

Reoperation after abdominal trauma.

A five year experience with 782 patients requiring laparotomy for trauma is reviewed. Specifically, the 70 patients requiring unplanned reexploration have been studied to delineate the indications for and implications of such repeat laparotomies. The major indications for such reoperation were intraabdominal abscess (45.7 per cent), bleeding (15.5 per cent), peritonitis (12.1 per cent), and small bowel obstruction (8.6 per cent). There were 16 negative reexplorations (13.8 per cent). Overall mortality in the reexplored patients was 21.4 per cent, all victims of gunshot or blunt trauma. Mortality correlated with the number of required reexplorations, being 67 per cent in those requiring four operations. Of the 31 laparotomies performed initially for diffuse or localized intraabdominal sepsis, only 15 were highly suspected, and 13 of these by simple chest x-ray findings. If after laparotomy for repair of intraabdominal trauma a patient fails to meet the anticipated norm of convalescence, a high index of suspicion for early postoperative hemorrhage, or later sepsis, should be maintained. Such patients have far more to gain than lose by reexploration.

Vascular trauma in the groin: contrast between iliac and femoral injuries.

Vascular injuries to the groin are common and often life-threatening. Injuries above the inguinal ligament, to the iliac system, are associated with a 37 percent mortality. Associated intraabdominal injuries are common. These patients must be identified promptly, given broad-spectrum antibiotics and taken immediately to the operating room for exploration through a midline incision. Injuries below the inguinal ligament are usually to the femoral vessels and are rarely fatal. These patients may be evaluated more extensively before leg exploration. Associated intraabdominal injuries are unusual, but disability from femoral fractures and nerve injuries are common.

Childhood depression and suicide.

Recent years have witnessed accumulating evidence that the disorders subsumed under the heading of childhood depression are much more prevalent than used to be believed; that these conditions in prepubertal youngsters are more similar to those disorders occurring in adolescents and adults than was previously believed; that childhood depression can co-exist with many other childhood conditions; and that, although a rare occurrence, suicide is committed by older children. To quote a professional in the child mental health field: It is difficult to see how depression could not be involved in almost every form of psychopathology. The various theories of personality speculate on the existence of unhappy and depressing feelings and cognitions at the core of human development, with ineffective means of dealing with these concerns expressed by abnormalities. . . . Thus it becomes reasonable to argue that depression is everywhere in childhood and adulthood and hence we must be careful to specify under what conditions it is to be regarded as pathological.

Laboratory adaptation of Bactrocera tryoni (Diptera: Tephritidae) decreases mating age and increases protein consumption and number of eggs produced per milligram of protein.

A significant reduction in age of mating occurred during the first four generations (G1-G4) of laboratory adaptation of wild Bactrocera tryoni (Froggatt) and this was associated with the earlier attainment of peak egg load although no significant differences were detected in the peak egg load itself. A long term laboratory (LTL) strain had a significantly earlier mating age and higher peak egg load than flies of wild origin or those from the first four laboratory generations. The amount of protein consumed by females in the first week of adult life was significantly higher in the LTL strain than in flies of wild origin or G1-G4 but there were no significant changes (or only slight changes) with laboratory adaptation in the amounts of protein consumed up to the ages of mating and peak egg load. Laboratory adaptation resulted in no significant changes in egg size, egg dry weight, puparial fresh weight and the dry weight of newly emerged females. The large increase in fecundity with laboratory adaptation is associated with a 4- to 5-fold increase in the rate of conversion of dietary protein to eggs (i.e. eggs produced per mg of protein consumed).