Targeting the kinase activities of ATR and ATM exhibits antitumoral activity in mouse models of MLL-rearranged AML

Among the various subtypes of acute myeloid leukemia (AML), those with chromosomal rearrangements of the MLL oncogene (AML-MLL) have a poor prognosis. AML-MLL tumor cells are resistant to current genotoxic therapies because of an attenuated response by p53, a protein that induces cell cycle arrest and apoptosis in response to DNA damage. In addition to chemicals that damage DNA, efforts have focused on targeting DNA repair enzymes as a general chemotherapeutic approach to cancer treatment. Here, we found that inhibition of the kinase ATR, which is the primary sensor of DNA replication stress, induced chromosomal breakage and death of mouse AML(MLL) cells (with an MLL-ENL fusion and a constitutively active N-RAS independently of p53. Moreover, ATR inhibition as a single agent exhibited antitumoral activity, both reducing tumor burden after establishment and preventing tumors from growing, in an immunocompetent allograft mouse model of AML(MLL) and in xenografts of a human AML-MLL cell line. We also found that inhibition of ATM, a kinase that senses DNA double-strand breaks, also promoted the survival of the AML(MLL) mice. Collectively, these data indicated that ATR or ATM inhibition represent potential therapeutic strategies for the treatment of AML, especially MLL-driven leukemias.

Bispectral index-guided intraoperative sedation with dexmedetomidine and midazolam infusion in outpatient cataract surgery

BACKGROUND

This study aimed to evaluate the role of alfa-2 agonist infusion, with dexmedetomidine or midazolam, on hemodynamic and respiratory parameters while titrating the sedation level with the bispectral index (BIS) during cataract surgery.

METHODS

Ninety consenting ASA class I-III patients who were electively undergoing cataract surgery were enrolled in the double blind study. A random infusion of 0.25 microg kg(-1) hr(-1) Dexmedetomidine (Group D), 25 microg kg(-1) hr(-1) midazolam (Group M), or saline for controls (Group C) was administered after mounting a BIS monitor and routine anesthetic care. The target BIS level was >85. An additional bolus dose in 1 mL increments of the study drug or cessation of the infusion was adjusted according to the BIS level. Changes in respiratory and vital parameters were noted and, in case of mild pain, 25 microg fentanyl was administered as a bolus. Pain and sedation were evaluated in the early postoperative period using visual analogue and four rating sedation scales.

RESULTS

In Group D, heart rate decreased in the later periods of surgery (35-50 min) and in the early postoperative period (5(th) and 15(th) min). Dose adjustments were required in six and ten patients in Groups D and M, respectively. Pain scores were lower with dexmedetomidine infusion.

CONCLUSIONS

Dexmedetomidine infusion mildly decreased heart rate in the later periods of surgery with better pain scores in the postoperative period. Dexmedetomidine should be an alternative for intraoperative sedation in outpatient cataract surgery.