Functional RNAi screen targeting cytokine and growth factor receptors reveals oncorequisite role for interleukin-2 gamma receptor in JAK3-mutation-positive leukemia.

To understand the role of cytokine and growth factor receptor-mediated signaling in leukemia pathogenesis, we designed a functional RNA interference (RNAi) screen targeting 188 cytokine and growth factor receptors that we found highly expressed in primary leukemia specimens. Using this screen, we identified interleukin-2 gamma receptor (IL2Rγ) as a critical growth determinant for a JAK3(A572V) mutation-positive acute myeloid leukemia cell line. We observed that knockdown of IL2Rγ abrogates phosphorylation of JAK3 and downstream signaling molecules, JAK1, STAT5, MAPK and pS6 ribosomal protein. Overexpression of IL2Rγ in murine cells increased the transforming potential of activating JAK3 mutations, whereas absence of IL2Rγ completely abrogated the clonogenic potential of JAK3(A572V), as well as the transforming potential of additional JAK3-activating mutations such as JAK3(M511I). In addition, mutation at the IL2Rγ interaction site in the FERM domain of JAK3 (Y100C) completely abrogated JAK3-mediated leukemic transformation. Mechanistically, we found IL2Rγ contributes to constitutive JAK3 mutant signaling by increasing JAK3 expression and phosphorylation. Conversely, we found that mutant, but not wild-type JAK3, increased the expression of IL2Rγ, indicating IL2Rγ and JAK3 contribute to constitutive JAK/STAT signaling through their reciprocal regulation. Overall, we demonstrate a novel role for IL2Rγ in potentiating oncogenesis in the setting of JAK3-mutation-positive leukemia. In addition, our study highlights an RNAi-based functional assay that can be used to facilitate the identification of non-kinase cytokine and growth factor receptor targets for inhibiting leukemic cell growth.

Choosing a concomitant chemotherapy and radiotherapy regimen for squamous cell head and neck cancer: A systematic review of the published literature with subgroup analysis.

BACKGROUND: A systematic review was conducted to develop clinical recommendations for concomitant chemotherapy (CT) and radiotherapy (RT) in patients with locally advanced squamous cell head and neck cancer (SCHNC). METHODS: Results of published randomized controlled trials (RCTs) were pooled using Meta-analyst(0.988) software. RESULTS: A pooled analysis of 18 RCTs (20 comparisons) involving 3,192 patients detected a reduction in mortality for concomitant therapy compared with RT alone (odds ratio [OR], 0.62; 95% confidence interval [CI], 0.52-0.74; relative risk, 0.83; risk reduction, 11%; p < .00001). Platinum-based regimens involving 1,514 patients from nine trials (10 comparisons) were most effective (OR, 0.57; 95% CI, 0.46-0.71; p < .00001; risk reduction, 12%). Concomitant therapy produced more acute adverse effects than RT alone. CONCLUSION: Platinum-based concomitant CT and RT is superior to conventional RT alone in improving survival in locally advanced SCHNC. Subgroup analyses can be used to help in choosing the most appropriate concomitant regimen.

The mechanism of impaired coagulation after partial hepatectomy in the dog.

Coagulation mechanisms were examined in the dog after a 70 per cent hepatectomy and the additional effect of varying periods of ischemia on the liver remnant. Dogs were submitted to a 70 per cent partial hepatectomy, and the liver remnant was rendered ischemic by occluding the vascular inflow. Portal decompression during ischemia was accomplished by allowing portal venous flow through the lobes subsequently resected. Dogs in the control group, those undergoing hepatectomy alone and those undergoing hepatectomy together with 60 minutes of ischemia time exhibited a fall in hemoglobin and hematocrit values, a transient leukocytosis, a small increase in kaolincephalin clotting time and a decline in platelet count but no significant thrombocytopenia. Prothrombin time was changed in dogs undergoing hepatectomy, but this was not affected by ischemia. The characteristic rise in plasma fibrinogen postoperatively was abolished, and fibrinogen levels were lower in dogs undergoing hepatectomy alone and fell significantly in dogs subjected to 30 to 60 minutes of ischemia of the liver remnant. Factors V and VII were decreased after hepatectomy, and Factor V was more severely reduced after 30 to 60 minutes of ischemia. There was no overt bleeding tendency. In ten dogs, the liver remnant was subjected to ischemia for 75 minutes. Four of these died within three days of operation, two with severe hypoglycemia and two with postoperative bleeding. All six surviving dogs exhibited gross coagulation defects. Prothrombin time rose, kaolin-cephalin clotting time increased and platelets fell to a greater degree than in any of the other dogs. Plasma fibrinogen level showed a profound fall, as did Factor V, the magnitude of these changes being greater than after a shorter period of ischemia. Factor VII was also decreased, but this did not appear to be related to the ischemic interval. In the clinical situation in which intrinsic coagulation mechanisms are shown to be impaired, treatment with Factor V and VII concentrates may be the best way of correcting the coagulation defect.

Liver blood flow measurement the interpretation of xenon133 clearance curves.

Liver tissue perfusion can be measured by analysis of the clearance of the radioactive inert gases Xenon133 and Krypton85 from the liver. The technique commonly gives rise to multiexponential clearance curves which have previously been quoted as evidence of complex intrahepatic blood flow patterns. The clearance of 133Xe from the canine liver was studied in 17 dogs and by screening out extrahepatic radioactivity it was found that the true intrahepatic clearance is monoexponential. The slower components seen in the multiexponential curve recorded without screening represent 133Xe in tissue other than the liver and much of this activity was shown to originate from 133Xe which accumulates in the stomach and intestines. These findings simplify the interpretation of inert gas clearance curves in the measurement of liver blood flow and therefore encourage further application of the technique in both experimental and clinical situations.

The effects of prolonged hepatic ischaemia before 70 per cent partial hepatectomy in the dog.

The effect of prolonged normothermic ischaemia before partial hepatectomy was assessed in 10 dogs. During the period of ischaemia, portal decompression was maintained. The survival rate for animals undergoing 75 minutes of total liver ischaemia was 60 per cent and 2 of the dogs died as a result of hypoglycaemia. High levels of alkaline phosphatase and transaminases in the survivors indicated a severe degree of hepatocyte damage. However, complete restoration of liver mass was noted 6 weeks after partial hepatectomy and was not impaired by the prolonged ischaemia. This study confirms the resistance of the dog liver to ischaemia before partial hepatectomy. The critical period beyond which ischaemia is followed by an increasing number of deaths and severe metabolic upset is in the region of 1 hours.