Preclinical and Clinical Characterization of Fibroblast-derived Neuregulin-1 on Trastuzumab and Pertuzumab Activity in HER2-positive Breast Cancer.

PURPOSE: To characterize expression of neuregulin-1 (NRG1), an HER3 ligand, in HER2-positive breast cancer and its relation with the efficacy of trastuzumab with or without pertuzumab. EXPERIMENTAL DESIGN: Characterization of NRG1 expression in tumor cell lines, in tumor specimens, and in cancer-associated fibroblasts (CAFs). Patient-derived CAFs were used to investigate NRG1 impact on the activity of trastuzumab with or without pertuzumab in HER2-positive breast cancer cells. The relationship between NRG1 expression and pathologic response to anti-HER2-based neoadjuvant therapy was assessed in a retrospective patient cohort and in the NeoSphere trial. RESULTS: NRG1 was expressed in HER2-positive breast cancer-derived fibroblasts at significantly higher levels than in cancer cells. NRG1 and the conditioned media (CM) from CAFs phosphorylated HER3 and AKT in cancer cells and mediated trastuzumab resistance. Stable genetic depletion of NRG1 from CAFs overcame trastuzumab resistance. Pertuzumab effectively suppressed trastuzumab resistance mediated by either NRG1 or CAF's CM. NRG1 engaged an epithelial-to-mesenchymal transition that was prevented by trastuzumab and pertuzumab. In clinical samples, stromal and/or tumor cell expression of NRG1 determined by immunohistochemistry was uncommon (13.2%) yet significantly linked with residual disease following trastuzumab-based neoadjuvant therapy. In the NeoSphere trial, the magnitude of the difference of pathologic complete response rates favoring the pertuzumab arm was higher in the NRG1-high group. CONCLUSIONS: CAF-derived NRG1 mediates trastuzumab resistance through HER3/AKT, which might be reverted by pertuzumab. In patients with HER2-positive breast cancer, high expression of NRG1 was associated to poor response to trastuzumab, but not in combination with pertuzumab.

A Transient Translaminar GABAergic Interneuron Circuit Connects Thalamocortical Recipient Layers in Neonatal Somatosensory Cortex.

GABAergic activity is thought to influence developing neocortical sensory circuits. Yet the late postnatal maturation of local layer (L)4 circuits suggests alternate sources of GABAergic control in nascent thalamocortical networks. We show that a population of L5b, somatostatin (SST)-positive interneuron receives early thalamic synaptic input and, using laser-scanning photostimulation, identify an early transient circuit between these cells and L4 spiny stellates (SSNs) that disappears by the end of the L4 critical period. Sensory perturbation disrupts the transition to a local GABAergic circuit, suggesting a link between translaminar and local control of SSNs. Conditional silencing of SST+ interneurons or conversely biasing the circuit toward local inhibition by overexpression of neuregulin-1 type 1 results in an absence of early L5b GABAergic input in mutants and delayed thalamic innervation of SSNs. These data identify a role for L5b SST+ interneurons in the control of SSNs in the early postnatal neocortex.

Yy1 as a molecular link between neuregulin and transcriptional modulation of peripheral myelination.

Fast axonal conduction depends on myelin, which is formed by Schwann cells in the PNS. We found that the transcription factor Yin Yang 1 (YY1) is crucial for peripheral myelination. Conditional ablation of Yy1 in the Schwann cell lineage resulted in severe hypomyelination, which occurred independently of altered Schwann cell proliferation or apoptosis. In Yy1 mutant mice, Schwann cells established a 1:1 relationship with axons but were unable to myelinate them. The Schwann cells expressed low levels of myelin proteins and of Egr2 (also called Krox20), which is an important regulator of peripheral myelination. In vitro, Schwann cells that lacked Yy1 did not upregulate Egr2 in response to neuregulin1 and did not express myelin protein zero. This phenotype was rescued by overexpression of Egr2. In addition, neuregulin-induced phosphorylation of YY1 was required for transcriptional activation of Egr2. Thus, YY1 emerges as an important activator of peripheral myelination that links neuregulin signaling with Egr2 expression.

Bilobalide promotes expression of glial cell line-derived neurotrophic factor and vascular endothelial growth factor in rat astrocytes.

AIM: To study the effects of bilobalide on the expression of glial cell line-derived neurotrophic factor (GDNF) and vascular endothelial growth factor (VEGF) in rat astrocytes in vitro. METHODS: Semiquantification polymerase chain reaction (SQ-PCR) was used to investigate GDNF and VEGF mRNA expression in the astrocytes after bilobalide (5, 15, 50, 100 mumol.L-1) treatment. Immunohistochemistry method was used to detect GDNF and VEGF protein expression in cells treated with bilobalide 50 mumol.L-1 for 24 h. RESULTS: GDNF and VEGF mRNA increased markedly after astrocytes were treated with bilobalide 50 mumol.L-1 for 12 h. GDNF and VEGF protein were detected in the cytoplasm of astrocytes after the cells were treated with bilobalide 50 mumol.L-1 for 24 h. CONCLUSION: Bilobalide induced GDNF and VEGF expression in the cultured astrocytes.