Induction of BIM Is Essential for Apoptosis Triggered by EGFR Kinase Inhibitors in Mutant EGFR-Dependent Lung Adenocarcinomas

Using a panel of human drug-sensitive EGFR mutant lung cancer cells, William Pao and colleagues show that induction of BIM, a member of the BCL2 family, is essential for apoptosis triggered by EGFR kinase inhibitors

Enhanced Motor Function by Training in Spinal Cord Contused Rats Following Radiation Therapy

Weight-bearing stepping, without supraspinal re-connectivity, can be attained by treadmill training in an animal whose spinal cord has been completely transected at the lower thoracic level. Repair of damaged tissue and of supraspinal connectivity/circuitry following spinal cord injury in rat can be achieved by specific cell elimination with radiation therapy of the lesion site delivered within a critical time window, 2-3 weeks postinjury. Here we examined the effects of training in the repaired spinal cord following clinical radiation therapy. Studies were performed in a severe rat spinal cord contusion injury model, one similar to fracture/crush injuries in humans; the injury was at the lower thoracic level and the training was a combined hindlimb standing and stepping protocol. Radiotherapy, in a similar manner to that reported previously, resulted in a significant level of tissue repair/preservation at the lesion site. Training in the irradiated group, as determined by limb kinematics tests, resulted in functional improvements that were significant for standing and stepping capacity, and yielded a significant direct correlation between standing and stepping performance. In contrast, the training in the unirradiated group resulted in no apparent beneficial effects, and yielded an inverse correlation between standing and stepping performance, e.g., subject with good standing showed poor stepping capacity. Further, without any training, a differential functional change was observed in the irradiated group; standing capacity was significantly inhibited while stepping showed a slight trend of improvement compared with the unirradiated group. These data suggest that following repair by radiation therapy the spinal circuitries which control posture and locomotor were modified, and that the beneficial functional modulation of these circuitries is use dependent. Further, for restoring beneficial motor function following radiotherapy, training seems to be crucial

Enhanced motor function by training in spinal cord contused rats following radiation therapy.

Weight-bearing stepping, without supraspinal re-connectivity, can be attained by treadmill training in an animal whose spinal cord has been completely transected at the lower thoracic level. Repair of damaged tissue and of supraspinal connectivity/circuitry following spinal cord injury in rat can be achieved by specific cell elimination with radiation therapy of the lesion site delivered within a critical time window, 2-3 weeks postinjury. Here we examined the effects of training in the repaired spinal cord following clinical radiation therapy. Studies were performed in a severe rat spinal cord contusion injury model, one similar to fracture/crush injuries in humans; the injury was at the lower thoracic level and the training was a combined hindlimb standing and stepping protocol. Radiotherapy, in a similar manner to that reported previously, resulted in a significant level of tissue repair/preservation at the lesion site. Training in the irradiated group, as determined by limb kinematics tests, resulted in functional improvements that were significant for standing and stepping capacity, and yielded a significant direct correlation between standing and stepping performance. In contrast, the training in the unirradiated group resulted in no apparent beneficial effects, and yielded an inverse correlation between standing and stepping performance, e.g., subject with good standing showed poor stepping capacity. Further, without any training, a differential functional change was observed in the irradiated group; standing capacity was significantly inhibited while stepping showed a slight trend of improvement compared with the unirradiated group. These data suggest that following repair by radiation therapy the spinal circuitries which control posture and locomotor were modified, and that the beneficial functional modulation of these circuitries is use dependent. Further, for restoring beneficial motor function following radiotherapy, training seems to be crucial

Development of new mouse lung tumor models expressing EGFR T790M mutants associated with clinical resistance to kinase inhibitors.

The EGFR T790M mutation confers acquired resistance to kinase inhibitors in human EGFR mutant lung adenocarcinoma, is occasionally detected before treatment, and may confer genetic susceptibility to lung cancer.To study further its role in lung tumorigenesis, we developed mice with inducible expression in type II pneumocytes of EGFR(T790M) alone or together with a drug-sensitive L858R mutation. Both transgenic lines develop lung adenocarcinomas that require mutant EGFR for tumor maintenance but are resistant to an EGFR kinase inhibitor. EGFR(L858R+T790M)-driven tumors are transiently targeted by hsp90 inhibition. Notably, EGFR(T790M)-expressing animals develop tumors with longer latency than EGFR(L858R+T790M)-bearing mice and in the absence of additional kinase domain mutations.These new mouse models of mutant EGFR-dependent lung adenocarcinomas provide insight into clinical observations. The models should also be useful for developing improved therapies for patients with lung cancers harboring EGFR(T790M) alone or in conjunction with drug-sensitive EGFR kinase domain mutations

BRAF-inhibitor associated MEK mutations increase RAF-dependent and -independent enzymatic activity

Alterations in MEK1/2 occur in cancers, both in the treatment-naïve state and following targeted therapies, most notably BRAF and MEK inhibitors in BRAF-V600E–mutant melanoma and colorectal cancer. Efforts were undertaken to understand the effects of these mutations, based upon protein structural location, and MEK1/2 activity. Two categories of MEK1/2 alterations were evaluated, those associated with either the allosteric pocket or helix-A. Clinically, MEK1/2 alterations of the allosteric pocket are rare and we demonstrate that they confer resistance to MEK inhibitors, while retaining sensitivity to BRAF inhibition. Most mutations described in patients fall within, or are associated with, helix-A. Mutations in this region reduce sensitivity to both BRAF and MEK inhibition and display elevated phospho-ERK1/2 levels, independent from increases in phospho-MEK1/2. Biochemical experiments with a representative helix-A variant, MEK1-Q56P, reveal both increased catalytic efficiency of the activated enzyme, and phosphorylation-independent activity relative to wild-type MEK1. Consistent with these findings, MEK1/2 alterations in helix A retain sensitivity to downstream antagonism via pharmacologic inhibition of ERK1/2. This work highlights the importance of classifying mutations based on structural and phenotypic consequences, both in terms of pathway signaling output and response to pharmacologic inhibition

Loss of Tuberous Sclerosis Complex 2 (TSC2) Confers Sensitivity to mTOR Inhibitor Everolimus in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is the third leading cause of cancer deaths worldwide and hyper-activation of mammalian target of rapamycin (mTOR) signaling plays a pivotal role in HCC tumorigenesis. Tuberous Sclerosis Complex (TSC), a heterodimer of TSC1 and TSC2, functions as a negative regulator of mTOR signaling. In the present study, we discovered that TSC2 loss of function is common in HCC. TSC2 loss was found in 4 of 8 HCC cell lines and 8 of 28 (28.5%) patient-derived HCC xenografts. TSC2 mutations and deletions are likely to be the underlying cause of TSC2 loss in HCC cell lines, xenografts and tumors for most cases. We further demonstrated that TSC2-null HCC cell lines and xenografts have elevated mTOR signaling and, more importantly, were significantly more sensitive to RAD001 (everolimus), an mTOR inhibitor. These preclinical findings led to the analysis of TSC2 status in HCC samples collected in the EVOLVE-1 clinical trial of everolimus. Using an optimized IHC assay we developed, 15 samples with low to undetectable levels of TSC2 (10.8%) were identified (5 in the placebo arm and 10 in the everolimus arm). Although the sample size lacked power to demonstrate statistical significance, TSC2-null/low tumor patients who received everolimus had noticeably longer overall survival than those who received placebo. We also observed that TSC2 loss is rare in Caucasian samples compared to Asian samples. Therefore, we performed an epidemiology survey of more than 239 Asian HCC tumors. The frequency of TSC2 loss is estimated to be around 20% in Asian HBV+ HCC, which accounts for nearly half of HCC malignancies in the world. Taken together, our data strongly argue that TSC2 loss is a predictive biomarker for the sensitivity to everolimus in HCC patients and can be applied as a robust selection biomarker for mTOR inhibitor clinical trials