Blockade of insulin-like growth factors increases efficacy of paclitaxel in metastatic breast cancer.

Breast cancer remains the leading cause of cancer death in women owing to metastasis and the development of resistance to established therapies. Macrophages are the most abundant immune cells in the breast tumor microenvironment and can both inhibit and support cancer progression. Thus, gaining a better understanding of how macrophages support cancer could lead to the development of more effective therapies. In this study, we find that breast cancer-associated macrophages express high levels of insulin-like growth factors 1 and 2 (IGFs) and are the main source of IGFs within both primary and metastatic tumors. In total, 75% of breast cancer patients show activation of insulin/IGF-1 receptor signaling and this correlates with increased macrophage infiltration and advanced tumor stage. In patients with invasive breast cancer, activation of Insulin/IGF-1 receptors increased to 87%. Blocking IGF in combination with paclitaxel, a chemotherapeutic agent commonly used to treat breast cancer, showed a significant reduction in tumor cell proliferation and lung metastasis in pre-clinical breast cancer models compared to paclitaxel monotherapy. Our findings provide the rationale for further developing the combination of paclitaxel with IGF blockers for the treatment of invasive breast cancer, and Insulin/IGF1R activation and IGF+ stroma cells as potential biomarker candidates for further evaluation

The APP intracellular domain is required for normal synaptic morphology, synaptic plasticity, and hippocampus-dependent behavior

The amyloid precursor protein family (APP/APLPs) has essential roles for neuromuscular synapse development and for the formation and plasticity of synapses within the CNS. Despite this, it has remained unclear whether APP mediates its functions primarily as a cell surface adhesion and signaling molecule or via its numerous proteolytic cleavage products. To address these questions, we followed a genetic approach and used APPΔCT15 knockin mice lacking the last 15 amino acids of APP, including the highly conserved YENPTY protein interaction motif. To circumvent functional compensation by the closely related APLP2, these mice were bred to an APLP2-KO background to generate APPΔCT15-DM double mutants. These APPΔCT15-DM mice were partially viable and displayed defects in neuromuscular synapse morphology and function with impairments in the ability to sustain transmitter release that resulted in muscular weakness. In the CNS, we demonstrate pronounced synaptic deficits including impairments in LTP that were associated with deficits in spatial learning and memory. Thus, the APP-CT15 domain provides essential physiological functions, likely via recruitment of specific interactors. Together with the well-established role of APPsα for synaptic plasticity, this shows that multiple domains of APP, including the conserved C-terminus, mediate signals required for normal PNS and CNS physiology. In addition, we demonstrate that lack of the APP-CT15 domain strongly impairs Aβ generation in vivo, establishing the APP C-terminus as a target for Aβ-lowering strategies. SIGNIFICANCE STATEMENT Synaptic dysfunction and cognitive decline are early hallmark features of Alzheimer's disease. Thus, it is essential to elucidate the in vivo function(s) of APP at the synapse. At present, it is unknown whether APP family proteins function as cell surface receptors, or mainly via shedding of their secreted ectodomains, such as neurotrophic APPsα. Here, to dissect APP functional domains, we used APP mutant mice lacking the last 15 amino acids that were crossed onto an APLP2-KO background. These APPΔCT15-DM mice showed defects in neuromuscular morphology and function. Synaptic deficits in the CNS included impairments of synaptic plasticity, spatial learning, and memory. Collectively, this indicates that multiple APP domains, including the C-terminus, are required for normal nervous system function

Hippocampal Network Oscillations in APP/APLP2-Deficient Mice

<div><p>The physiological function of amyloid precursor protein (APP) and its two homologues APP-like protein 1 (APLP1) and 2 (APLP2) is largely unknown. Previous work suggests that lack of APP or APLP2 impairs synaptic plasticity and spatial learning. There is, however, almost no data on the role of APP or APLP at the network level which forms a critical interface between cellular functions and behavior. We have therefore investigated memory-related synaptic and network functions in hippocampal slices from three lines of transgenic mice: APPsα-KI (mice expressing extracellular fragment of APP, corresponding to the secreted APPsα ectodomain), APLP2-KO, and combined APPsα-KI/APLP2-KO (APPsα-DM for “double mutants”). We analyzed two prominent patterns of network activity, gamma oscillations and sharp-wave ripple complexes (SPW-R). Both patterns were generally preserved in all strains. We find, however, a significantly reduced frequency of gamma oscillations in CA3 of APLP2-KO mice in comparison to APPsα-KI and WT mice. Network activity, basic synaptic transmission and short-term plasticity were unaltered in the combined mutants (APPsα-DM) which showed, however, reduced long-term potentiation (LTP). Together, our data indicate that APLP2 and the intracellular domain of APP are not essential for coherent activity patterns in the hippocampus, but have subtle effects on synaptic plasticity and fine-tuning of network oscillations.</p></div

Comparative analysis of single and combined APP/APLP knockouts reveals reduced spine density in APP-KO mice that is prevented by APPα expression

Synaptic dysfunction and synapse loss are key features of Alzheimer's pathogenesis. Previously, we showed an essential function of APP and APLP2 for synaptic plasticity, learning and memory. Here, we used organotypic hippocampal cultures to investigate the specific role(s) of APP family members and their fragments for dendritic complexity and spine formation of principal neurons within the hippocampus. Whereas CA1 neurons from APLP1-KO or APLP2-KO mice showed normal neuronal morphology and spine density, APP-KO mice revealed a highly reduced dendritic complexity in mid-apical dendrites. Despite unaltered morphology of APLP2-KO neurons, combined APP/APLP2-DKO mutants showed an additional branching defect in proximal apical dendrites, indicating redundancy and a combined function of APP and APLP2 for dendritic architecture. Remarkably, APP-KO neurons showed a pronounced decrease in spine density and reductions in the number of mushroom spines. No further decrease in spine density, however, was detectable in APP/APLP2-DKO mice. Mechanistically, using APPsalpha-KI mice lacking transmembrane APP and expressing solely the secreted APPsalpha fragment we demonstrate that APPsalpha expression alone is sufficient to prevent the defects in spine density observed in APP-KO mice. Collectively, these studies reveal a combined role of APP and APLP2 for dendritic architecture and a unique function of secreted APPs for spine density

Insulin-Like Growth Factor (IGF) Pathway Targeting in Cancer: Role of the IGF Axis and Opportunities for Future Combination Studies

<h3>Article full text</h3><div>The full text of this article can be found below.</div

Spontaneous sharp wave-ripple complexes (SPW-R) in CA1 pyramidal layer.

<p>(A) 5 s of SPW-R raw trace recorded in the CA1 pyramidal layer. (B) Time-frequency of SPW-R, sharp waves are superimposed by high frequency ripple oscillation (∼240 Hz). (C) Medians of sharp-wave frequency are around 3 Hz in all four groups. (D) Medians of sharp-wave amplitude are around 0.4 mV, which is similar among all four groups. (E) Median of ripple frequency is slightly higher in APPsα-KI mice, in comparison to APLP2-KO mice, but without significant difference. (F) Mean of ripple energy is slightly higher in APPsα-KI and APPsα-DM mice. (n = 17/15/16/14 slices from 11/11/11/10 animals).</p

Gamma oscillations in CA3 among four groups.

<p>(A) 1 s raw traces of gamma oscillation in CA3. (B) The leading frequency and the full width of half maximum are indicated in the power spectra of CA3 (taken from the same recording as (A)). (C) Mean of gamma frequency in APLP2-KO mice is significantly decreased in comparison to WT and APPsα-KI mice. (D) Gamma amplitude is gradually enhanced from APPsα-KI, APLP2-KO to APPsα-DM in CA3, but without significant difference. (E) Gamma power shows similar trend as gamma amplitude, but doesn’t reach the significant level. (F) Gamma distinctness in CA3 is gradually enhanced. (G) Coupling strength between CA3 to CA1 is slightly weaker in APPsα-KI mice in comparison to APLP2-KO mice. (n = 8/7/9/7 slices from 7/6/7/6 animals).</p

Acute function of secreted amyloid precursor protein fragment APPsα in synaptic plasticity

The key role of APP in the pathogenesis of Alzheimer disease is well established. However, postnatal lethality of double knockout mice has so far precluded the analysis of the physiological functions of APP and the APLPs in the brain. Previously, APP family proteins have been implicated in synaptic adhesion, and analysis of the neuromuscular junction of constitutive APP/APLP2 mutant mice showed deficits in synaptic morphology and neuromuscular transmission. Here, we generated animals with a conditional APP/APLP2 double knockout (cDKO) in excitatory forebrain neurons using NexCre mice. Electrophysiological recordings of adult NexCre cDKOs indicated a strong synaptic phenotype with pronounced deficits in the induction and maintenance of hippocampal LTP and impairments in paired pulse facilitation, indicating a possible presynaptic deficit. These deficits were also reflected in impairments in nesting behavior and hippocampus-dependent learning and memory tasks, including deficits in Morris water maze and radial maze performance. Moreover, while no gross alterations of brain morphology were detectable in NexCre cDKO mice, quantitative analysis of adult hippocampal CA1 neurons revealed prominent reductions in total neurite length, dendritic branching, reduced spine density and reduced spine head volume. Strikingly, the impairment of LTP could be selectively rescued by acute application of exogenous recombinant APPsα, but not APPsβ, indicating a crucial role for APPsα to support synaptic plasticity of mature hippocampal synapses on a rapid time scale. Collectively, our analysis reveals an essential role of APP family proteins in excitatory principal neurons for mediating normal dendritic architecture, spine density and morphology, synaptic plasticity and cognition