3 research outputs found
MEK inhibition leads to BRCA2 downregulation and sensitization to DNA damaging agents in pancreas and ovarian cancer models
Targeting the DNA damage response (DDR) in tumors with defective DNA repair
is a clinically successful strategy. The RAS/RAF/MEK/ERK signalling pathway is
frequently deregulated in human cancers. In this study, we explored the effects of
MEK inhibition on the homologous recombination pathway and explored the potential
for combination therapy of MEK inhibitors with DDR inhibitors and a hypoxia-activated
prodrug.
We studied effects of combining pimasertib, a selective allosteric inhibitor of
MEK1/2, with olaparib, a small molecule inhibitor of poly (adenosine diphosphate
[ADP]-ribose) polymerases (PARP), and with the hypoxia-activated prodrug
evofosfamide in ovarian and pancreatic cancer cell lines. Apoptosis was assessed
by Caspase 3/7 assay and protein expression was detected by immunoblotting.
DNA damage response was monitored with γH2AX and RAD51 immunofluorescence
staining. In vivo antitumor activity of pimasertib with evofosfamide were assessed
in pancreatic cancer xenografts.
We found that BRCA2 protein expression was downregulated following pimasertib
treatment under hypoxic conditions. This translated into reduced homologous
recombination repair demonstrated by levels of RAD51 foci. MEK inhibition was
sufficient to induce formation of γH2AX foci, suggesting that inhibition of this pathway
would impair DNA repair. When combined with olaparib or evofosfamide, pimasertib
treatment enhanced DNA damage and increased apoptosis. The combination of
pimasertib with evofosfamide demonstrated increased anti-tumor activity in BRCA
wild-type Mia-PaCa-2 xenograft model, but not in the BRCA mutated BxPC3 model.
Our data suggest that targeted MEK inhibition leads to impaired homologous
recombination DNA damage repair and increased PARP inhibition sensitivity in BRCA-
2 proficient cancers
Fast modulation of visual perception by basal forebrain cholinergic neurons
The basal forebrain provides the primary source of cholinergic input to the cortex, and it has a crucial function in promoting wakefulness and arousal. However, whether rapid changes in basal forebrain neuron spiking in awake animals can dynamically influence sensory perception is unclear. Here we show that basal forebrain cholinergic neurons rapidly regulate cortical activity and visual perception in awake, behaving mice. Optogenetic activation of the cholinergic neurons or their V1 axon terminals improved performance of a visual discrimination task on a trial-by-trial basis. In V1, basal forebrain activation enhanced visual responses and desynchronized neuronal spiking; these changes could partly account for the behavioral improvement. Conversely, optogenetic basal forebrain inactivation decreased behavioral performance, synchronized cortical activity and impaired visual responses, indicating the importance of cholinergic activity in normal visual processing. These results underscore the causal role of basal forebrain cholinergic neurons in fast, bidirectional modulation of cortical processing and sensory perception.National Institute of Mental Health (U.S.) (Grant RC1-MH088434)National Institute of Neurological Disorders and Stroke (U.S.) (Ruth L. Kirschstein National Research Service Award F31NS059258